A comparative analysis of multidimensional features of objects resembling sets of graphs

In the present paper, we introduce a notion of a style representing abstract, complex objects having characteristics that can be represented as structured objects. Furthermore, we provide some mathematical properties of such styles. As a main result, we present a novel approach to perform a meaningful comparative analysis of such styles by defining and using graph-theoretic measures. We compare two styles by comparing the underlying feature sets representing sets of graph structurally. To determine the structural similarity between the underlying graphs, we use graph similarity measures that are computationally efficient. More precisely, in order to compare styles, we map each feature set to a so-called median graph and compare the resulting median graphs. As an application, we perform an experimental study to compare special styles representing sets of undirected graphs and present numerical results thereof.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: TU Vienna, Department of Biostatistics, Visiting Graduate Student in Department of Urban Design and Planning, University of Washington, Seattle, USA 1.1.2012-15.6.2012 (12.9.2011 alkaen), University of Veterinary Medicine Vienna
Contributors: Dehmer, M., Emmert-Streib, F., Gesell, T.
Number of pages: 15
Pages: 221-235
Publication date: 15 Feb 2008
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 196
Issue number: 1
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2008): SJR 0.778 SNIP 0.983
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics, Numerical Analysis
Keywords: Classification, Object comparison, Similarity, Structural similarity, Structured objects
Source: Scopus
Source ID: 38049038817

Research output: Contribution to journalArticleScientificpeer-review

A comparison between joint regression analysis and the AMMI model: A case study with barley

Joint regression analysis (JRA) and additive main effects and multiplicative interaction (AMMI) models are compared in order to (i) access the ability of describing a genotype by environment interaction effects and (ii) evaluate the agreement between the winners of mega-environments obtained from the AMMI analysis and the genotypes in the upper contour of the JRA. An iterative algorithm is used to obtain the environmental indexes for JRA, and standard multiple comparison procedures are adapted for genotype comparison and selection. This study includes three data sets from a spring barley (Hordeum vulgare L.) breeding programme carried out between 2004 and 2006 in Czech Republic. The results from both techniques are integrated in order to advise plant breeders, farmers and agronomists for better genotype selection and prediction for new years and/or new environments.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Depto. de Matemática, NOVA University of Lisbon, Dept. of Mathematical and Statistical Methods
Contributors: Pereira, D. G., Rodrigues, P. C., Mejza, S., Mexia, J. T.
Number of pages: 15
Pages: 193-207
Publication date: Feb 2012
Peer-reviewed: Yes

Publication information

Journal: JOURNAL OF STATISTICAL COMPUTATION AND SIMULATION
Volume: 82
Issue number: 2
ISSN (Print): 0094-9655
Ratings: 
  • Scopus rating (2012): CiteScore 0.68 SJR 0.604 SNIP 1.041
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Statistics and Probability, Modelling and Simulation, Statistics, Probability and Uncertainty
Keywords: AMMI models, joint regression analysis, mega-environments, multiple comparisons, spring barley, zigzag algorithm
Source: Scopus
Source ID: 84856990001

Research output: Contribution to journalArticleScientificpeer-review

A Comprehensive Framework for Spectrum Sensing in Non-Linear and Generalized Fading Conditions

We derive a comprehensive analytical framework for the ED over generalized, extreme, and non-linear fading conditions which addresses the topic completely. This is carried out for both conventional and diversity receptions and it is based on the area under the ROC curve (AUC), which is an efficient performance measure that is widely used in physical sciences and engineering. This differentiates the considered methodology from the aforementioned routine approaches and additionally provides generic results on the arbitrary derivatives of the MGF of useful generalized processes. The asymptotic behavior of the derived expressions is also analyzed providing direct and concrete insights on the role and effect of the involved parameters on the ED performance. The offered analytic results are subsequently employed in quantifying the performance of ED over various types of fading conditions, which exhibits that ED performance is significantly degraded by even slight variations of the severity of fading. To this end, it is shown that the detrimental effects of fading can be effectively mitigated with the aid of square-law combining and switch-And-stay combining methods, as a low number of diversity branches can ensure sufficient and holistic performance improvement even in severe fading conditions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, University of Leeds, Department of Electrical and Computer Engineering, Khalifa University, Semnan University, New Jersey Institute of Technology, Technological Educational Institute of Central Greece, Nazarbayev University
Contributors: Sofotasios, P. C., Bagheri, A., Tsiftsis, T. A., Freear, S., Shahzadi, A., Valkama, M.
Number of pages: 17
Pages: 8615-8631
Publication date: 1 Oct 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 66
Issue number: 10
ISSN (Print): 0018-9545
Ratings: 
  • Scopus rating (2017): CiteScore 4.69 SJR 0.75 SNIP 2.059
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Area under ROC curve, Bell polynomials, cognitive radio, diversity, multipath fading, radar systems
Electronic versions: 
Source: Scopus
Source ID: 85035745212

Research output: Contribution to journalArticleScientificpeer-review

Adaptive autoregressive model for reduction of noise in SPECT

This paper presents improved autoregressive modelling (AR) to reduce noise in SPECT images. An AR filter was applied to prefilter projection images and postfilter ordered subset expectation maximisation (OSEM) reconstruction images (AR-OSEM-AR method). The performance of this method was compared with filtered back projection (FBP) preceded by Butterworth filtering (BW-FBP method) and the OSEM reconstruction method followed by Butterworth filtering (OSEM-BW method). A mathematical cylinder phantom was used for the study. It consisted of hot and cold objects. The tests were performed using three simulated SPECT datasets. Image quality was assessed by means of the percentage contrast resolution (CR%) and the full width at half maximum (FWHM) of the line spread functions of the cylinders. The BW-FBP method showed the highest CR% values and the AR-OSEM-AR method gave the lowest CR% values for cold stacks. In the analysis of hot stacks, the BW-FBP method had higher CR% values than the OSEM-BW method. The BW-FBP method exhibited the lowest FWHM values for cold stacks and the AR-OSEM-AR method for hot stacks. In conclusion, the AR-OSEM-AR method is a feasible way to remove noise from SPECT images. It has good spatial resolution for hot objects.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Automation Science and Engineering, Division of Nuclear Medicine, Department of Diagnostic Radiology, Oulu University Hospital, Department of Clinical Physiology and Nuclear Medicine, Joint Authority for Päijät-Häme Social and Health Care
Contributors: Takalo, R., Hytti, H., Ihalainen, H., Sohlberg, A.
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: Computational and Mathematical Methods in Medicine
Volume: 2015
Article number: 494691
ISSN (Print): 1748-670X
Ratings: 
  • Scopus rating (2015): CiteScore 1.03 SJR 0.466 SNIP 0.726
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Modelling and Simulation, Biochemistry, Genetics and Molecular Biology(all), Medicine(all), Immunology and Microbiology(all)
Source: Scopus
Source ID: 84930684783

Research output: Contribution to journalArticleScientificpeer-review

A general framework for island systems

The notion of an island defined on a rectangular board is an elementary combinatorial concept that occurred first in [3]. Results of [3] were starting points for investigations exploring several variations and various aspects of this notion. In this paper we introduce a general framework for islands that subsumes all earlier studied concepts of islands on finite boards, moreover we show that the prime implicants of a Boolean function, the formal concepts of a formal context, convex subgraphs of a simple graph, and some particular subsets of a projective plane also fit into this framework. We axiomatize those cases where islands have the property of being pairwise comparable or disjoint, or they are distant, introducing the notion of a connective island domain and of a proximity domain, respectively. In the general case the maximal systems of islands are characterised by using the concept of an admissible system. We also characterise all possible island systems in the case of connective island domains and proximity domains.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Mathematics, Bolyai Institute, University of Szeged, University of Miskolc
Contributors: Foldes, S., Horváth, E. K., Radeleczki, S., Waldhauser, T.
Number of pages: 22
Pages: 3-24
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: Acta Universitatis Szegediensis: Acta Scientiarum Mathematicarum
Volume: 81
Issue number: 1-2
ISSN (Print): 0001-6969
Ratings: 
  • Scopus rating (2015): CiteScore 0.34 SJR 0.309 SNIP 0.73
Original language: English
ASJC Scopus subject areas: Analysis, Applied Mathematics
Keywords: Admissible system, CD-independent and CDW-independent sets, Connected subgraph, Convex subgraph, Distant system, Formal concept, Height function, Island domain, Island system, Point-to-set proximity relation, Prime implicant, Projective plane, Proximity domain
Source: Scopus
Source ID: 84938827353

Research output: Contribution to journalArticleScientificpeer-review

A hybrid optimization grey model based on segmented gra and multi-strategy contest for short-term power load forecasting

In this paper, a hybrid grey model with both internal and external optimization is proposed to forecast the short-term power load which has the characteristics of nonlinear fluctuation and random growth. The internal optimization consists of modeling feasibility test and parameter a correction. The external optimization includes three aspects. First, the original series are selected from different viewpoints to construct different forecasting strategies. Second, the predicted day is divided into several smooth segments for separate forecasting. Finally, the different forecasting strategies are implemented respectively in the different segments through grey correlation contest. A practical application verifies that the proposed model has a higher forecasting accuracy and the independency on the choice of initial value.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Sensing Systems for Wireless Medicine (MediSense), Hunan University, Institute of Intelligence Engineering, Georgia Institute of Technology
Contributors: Min, J., Xiang, Z., Zhiming, Z., Tentzeris, M. M.
Number of pages: 14
Pages: 15-28
Publication date: 2012
Peer-reviewed: Yes

Publication information

Journal: JOURNAL OF GREY SYSTEM
Volume: 24
Issue number: 1
ISSN (Print): 0957-3720
Ratings: 
  • Scopus rating (2012): CiteScore 0.43 SJR 0.374 SNIP 0.642
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Control and Optimization, Modelling and Simulation, Statistics, Probability and Uncertainty
Keywords: External optimization, Hybrid grey model, Multi-strategy contest, Parameter a correction, Segmented grey correlation, Short-term power load forecasting
Source: Scopus
Source ID: 84858229525

Research output: Contribution to journalArticleScientificpeer-review

Analysis of common rail pressure signal of dual-fuel large industrial engine for identification of injection duration of pilot diesel injectors

In this paper, we address the problem of identification of injection duration of common rail (CR) diesel pilot injectors of dual-fuel engines. In these pilot injectors, the injected volume is small and the repeatability of injections and identification of drifts of injectors are important factors, which need to be taken into account in order to achieve good repeatability (shot-to-shot with every cylinder) and therefore a well-balanced engine and furthermore reduced overall wear. This information can then be used for calibration and diagnostics purposes to guarantee engine longevity facilitated by consistent operating conditions throughout the life of the unit. A diagnostics method based on analysis of CR pressure with experimental results is presented in this paper. Using the developed method, the relative duration of injection events can be identified for multiple injectors. We use the phenomenon of drop in rail pressure due to an injection event as a feature of the injection process. The method is based on filtered CR pressure data during and after the injection event. First, the pressure signal during injection is extracted after control of each injection event. After that, the signal is normalized and filtered. Then a derivative of the filtered signal is calculated. Change in the derivative of the filtered signal larger than a predefined threshold indicates an injection event that can be detected and its relative duration can be identified. We present the experimental results and demonstrate the efficacy of the proposed methods using two different
types of pressure sensors. We are able to properly identify a change of ≥10 μs (2%, 500 μs) in injection time. This shows that the developed method detects drifts in injection duration and the magnitude of drift. This information can be used for adaptive control of injection duration, so that finally the injected fuel volume is the same as the original.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Automation and Hydraulic Engineering
Contributors: Krogerus, T., Hyvönen, M., Huhtala, K.
Pages: 1-9
Publication date: Mar 2018
Peer-reviewed: Yes
Early online date: 6 Dec 2017

Publication information

Journal: Fuel
Volume: 216
ISSN (Print): 0016-2361
Ratings: 
  • Scopus rating (2018): CiteScore 5.8 SJR 1.745 SNIP 2.012
Original language: English
ASJC Scopus subject areas: Mechanical Engineering, Signal Processing, Modelling and Simulation, Applied Mathematics
Keywords: Analysis , Dual-fuel engine , Diesel , Common rail , Injector , Rail pressure
Electronic versions: 
URLs: 

Research output: Contribution to journalArticleScientificpeer-review

Analysis of the damping characteristics of two power electronics-based devices using ‘individual channel analysis and design’

A comparison of the capabilities of two quite distinct power electronics-based ‘flexible AC transmission systems’ devices is presented. In particular, the damping of low frequency electromechanical oscillations is investigated aiming at improving the performance of power systems. The comparison is made using frequency domain methods under the ‘individual channel analysis and design’ framework. A synchronous generator feeding into a system with large inertia is used for such a purpose. Two system configurations including compensation are analysed: (a) in series in the form of a thyristor-controlled series compensator, and (b) in shunt through a static VAr compensator featuring a damping controller. Analyses are carried out to elucidate the dynamic behaviour of the synchronous generator in the presence of the power electronics-based controllers and for the case when no controller is present. Performance and robustness assessments are given particular emphasis. The crux of the matter is the comparison between the abilities of the static VAr compensator and the thyristor-controlled series compensator to eliminate the problematic switch-back characteristic intrinsic to synchronous generator operation by using the physical insight afforded by ‘individual channel analysis and design’.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Energy Engineering, Research group: Power systems, Cardiff University, Monterrey
Contributors: Ugalde-Loo, C. E., Acha, E., Licéaga-Castro, E.
Number of pages: 19
Pages: 527-545
Publication date: 1 Jul 2018
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematical Modelling
Volume: 59
ISSN (Print): 0307-904X
Ratings: 
  • Scopus rating (2018): CiteScore 3.36 SJR 0.873 SNIP 1.495
Original language: English
ASJC Scopus subject areas: Modelling and Simulation, Applied Mathematics
Keywords: Flexible AC transmission systems, Frequency domain analysis, Individual channel analysis and design, Multivariable control, Static VAr compensator, Thyristor-controlled series compensator
Electronic versions: 
Source: Scopus
Source ID: 85044623804

Research output: Contribution to journalArticleScientificpeer-review

Analytical model for magnetic anisotropy of non-oriented steel sheets

Purpose - Recent investigations on magnetic properties of non-oriented (NO) steel sheets enhance the comprehension of the magnetic anisotropy behaviour of widely employed electrical sheets. The concept of energy/coenergy density can be employed to model these magnetic properties. However, it usually presents an implicit form which requires an iterative process. The purpose of this paper is to develop an analytical model to consider these magnetic properties with an explicit formulation in order to ease the computations. Design/methodology/approach - From rotational measurements, the anhysteretic curves are interpolated in order to extract the magnetic energy density for different directions and amplitudes of the magnetic flux density. Furthermore, the analytical representation of this energy is suggested based on statistical distribution which aims to minimize the intrinsic energy of the material. The model is finally validated by comparing measured and computed values of the magnetic field strength. Findings - The proposed model is based on an analytical formulation of the energy depending on the components of the magnetic flux density. This formulation is composed of three Gumbel distributions. Every functional parameters of energy density is formulated with only four parameters which are calculated by fitting the energy extracted from measurements. Finally, the proposed model is validated by comparing the computation and the measurements of 9 H loci for NO steel sheets at 10 Hz. The proposed analytical model shows good agreements with an average relative error of 27 per cent. Originality/value - The paper presents an original analytical method to model magnetic anisotropy for NO electrical sheets. With this analytical formulation, the determination of H does not require any iterative process as it is usually the case with this energy method coupled with implicit function. This method can be easily incorporated in finite element method since it does not require any extra iterative process.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Smart Energy Systems (SES), Aalto University
Contributors: Martin, F., Singh, D., Belahcen, A., Rasilo, P., Haavisto, A., Arkkio, A.
Number of pages: 14
Pages: 1475-1488
Publication date: 7 Sep 2015
Peer-reviewed: Yes

Publication information

Journal: COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering
Volume: 34
Issue number: 5
ISSN (Print): 0332-1649
Ratings: 
  • Scopus rating (2015): CiteScore 0.68 SJR 0.231 SNIP 0.554
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Computational Theory and Mathematics, Applied Mathematics
Keywords: FEM, Ferromagnetic materials, Magnetic anisotropy, Soft magnetic materials
Source: Scopus
Source ID: 84941117731

Research output: Contribution to journalArticleScientificpeer-review

An efficient heuristic approach to detecting graph isomorphism based on combinations of highly discriminating invariants

The search for an easily computable, finite, complete set of graph invariants remains a challenging research topic. All measures characterizing the topology of a graph that have been developed thus far exhibit some degree of degeneracy, i.e., an inability to distinguish between non-isomorphic graphs. In this paper, we show that certain graph invariants can be useful in substantially reducing the computational complexity of isomorphism testing. Our findings are underpinned by numerical results based on a large scale statistical analysis.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Institute for Bioinformatics and Translational Research, The City College of New York (CUNY), Computational Biology and Machine Learning Lab., Faculty of Medicine, Health and Life Sciences, Queen's University, Belfast, Northern Ireland
Contributors: Dehmer, M., Grabner, M., Mowshowitz, A., Emmert-Streib, F.
Number of pages: 15
Pages: 311-325
Publication date: Aug 2013
Peer-reviewed: Yes

Publication information

Journal: Advances in Computational Mathematics
Volume: 39
Issue number: 2
ISSN (Print): 1019-7168
Ratings: 
  • Scopus rating (2013): CiteScore 1.5 SJR 1.063 SNIP 1.644
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics
Keywords: Graph isomorphism, Graph measures, Graph topology, Graphs, Uniqueness
Source: Scopus
Source ID: 84884974800

Research output: Contribution to journalArticleScientificpeer-review

A New Approach to Sign-Bit-Based Parameter Estimation in OFDM Receivers

This article combines algorithm development, thorough analysis and implementation of sign-bit (SB) estimation techniques for symbol timing, carrier frequency offset (CFO) and signal-to-noise ratio (SNR) in orthogonal frequency division multiplexing receivers. The SB estimation is compared in terms of performance and hardware complexity to an equivalent implementation with higher quantization. The techniques are demonstrated by simulation of a SB time/frequency and SB-SNR estimator for 3rd Generation Partnership Project long-term evolution (LTE) cell search in 65-nm technology operating at nominal voltage of 1.2 V. According to post-layout power simulations with toggling information, the architecture estimates the corresponding CFO and SNR for as little as $$479\,\upmu \hbox {W}$$479μW average power for LTE-R8/10, while occupying a silicon area as small as $$0.03\,\hbox {mm}^2$$0.03<sup>mm2</sup>. Even though SB estimation experiences some relative performance penalty when compared to 8-bit quantization, this paper demonstrates various advantages and the potential of employing these techniques in low-complexity terminals.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Wireless Communications and Positioning (WICO), Lund Univ, Lund University, Ericsson Research
Contributors: Diaz, I., Wilhelmsson, L. R., Sofotasios, P. C., Miao, Y., Tan, S., Edfors, O., Öwall, V.
Number of pages: 30
Pages: 3631-3660
Publication date: 23 Nov 2015
Peer-reviewed: Yes

Publication information

Journal: Circuits, Systems and Signal Processing
Volume: 34
Issue number: 11
ISSN (Print): 0278-081X
Ratings: 
  • Scopus rating (2015): CiteScore 1.54 SJR 0.506 SNIP 0.909
Original language: English
ASJC Scopus subject areas: Signal Processing, Applied Mathematics
Keywords: CFO, LTE, OFDM, Receiver design, SNR, Symbol timing, Time synchronization
Source: Scopus
Source ID: 84941992241

Research output: Contribution to journalArticleScientificpeer-review

A similarity measure for graphs with low computational complexity

We present and analyze an algorithm to measure the structural similarity of generalized trees, a new graph class which includes rooted trees. For this, we represent structural properties of graphs as strings and define the similarity of two graphs as optimal alignments of the corresponding property stings. We prove that the obtained graph similarity measures are so called Backward similarity measures. From this we find that the time complexity of our algorithm is polynomial and, hence, significantly better than the time complexity of classical graph similarity methods based on isomorphic relations.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Technical University Darmstadt, Stowers Institute for Medical Research
Contributors: Dehmer, M., Emmert-Streib, F., Kilian, J.
Number of pages: 13
Pages: 447-459
Publication date: 1 Nov 2006
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 182
Issue number: 1
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2006): SJR 0.809 SNIP 1.217
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics, Numerical Analysis
Keywords: Computational complexity, Dynamic programming, Graph similarity, Graph theory
Source: Scopus
Source ID: 33750819438

Research output: Contribution to journalArticleScientificpeer-review

Asymptotic expansion of European options with mean-reverting stochastic volatility dynamics

We develop methods for pricing European options under general mean-reverting stochastic volatility dynamics, which can be used with both affine and non-affine volatility models. In our methods, the option price under stochastic volatility is expanded as a power series of parameters or variables by transferring the original partial differential equation to a set of solvable inhomogeneous Black–Scholes equations. The analytic approximation is more generally applicable than the fast Fourier transform, because it does not rely on the existence of a characteristic function. Finally, we numerically demonstrate our approach with the Heston, 3/2, and continuous-time GARCH models.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Industrial Management, Research group: Financial Engineering, Research Community on Data-to-Decision (D2D)
Contributors: Hu, J., Kanniainen, J.
Number of pages: 10
Pages: 1-10
Publication date: Aug 2015
Peer-reviewed: Yes

Publication information

Journal: Finance Research Letters
Volume: 14
ISSN (Print): 1544-6123
Ratings: 
  • Scopus rating (2015): CiteScore 0.72 SJR 0.397 SNIP 0.804
Original language: English
ASJC Scopus subject areas: Economics, Econometrics and Finance(all), Business, Management and Accounting(all), Applied Mathematics
Keywords: Option pricing, Series expansion, Partial Differential Equations, Stochastic volatility, Non-affine models

Research output: Contribution to journalArticleScientificpeer-review

Asymptotics for infinite systems of differential equations

This paper investigates the asymptotic behavior of solutions to certain infinite systems of ordinary differential equations. In particular, we use results from ergodic theory and the asymptotic theory of C0-semigroups to obtain a characterization, in terms of convergence of certain Cesàro averages, of those initial values which lead to convergent solutions. Moreover, we obtain estimates on the rate of convergence for solutions whose initial values satisfy a stronger ergodic condition. These results rely on a detailed spectral analysis of the operator describing the system, which is made possible by certain structural assumptions on the operator. The resulting class of systems is sufficiently broad to cover a number of important applications including, in particular, both the so-called robot rendezvous problem and an important class of platoon systems arising in control theory. Our method leads to new results in both cases.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, Research group: Computer Science and Applied Logics
Contributors: Paunonen, L., Seifert, D.
Number of pages: 26
Pages: 1153-1178
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: SIAM Journal on Control and Optimization
Volume: 55
Issue number: 2
ISSN (Print): 0363-0129
Ratings: 
  • Scopus rating (2017): CiteScore 1.94 SJR 1.399 SNIP 1.723
Original language: English
ASJC Scopus subject areas: Control and Optimization, Applied Mathematics
Keywords: Asymptotic behavior, C0-semigroup, Ergodic theory, Ordinary differential equations, Rates of convergence, Spectrum, System
Electronic versions: 
Source: Scopus
Source ID: 85018956934

Research output: Contribution to journalArticleScientificpeer-review

Asymptotics for periodic systems

This paper investigates the asymptotic behaviour of solutions of periodic evolution equations. Starting with a general result concerning the quantified asymptotic behaviour of periodic evolution families we go on to consider a special class of dissipative systems arising naturally in applications. For this class of systems we analyse in detail the spectral properties of the associated monodromy operator, showing in particular that it is a so-called Ritt operator under a natural ‘resonance’ condition. This allows us to deduce from our general result a precise description of the asymptotic behaviour of the corresponding solutions. In particular, we present conditions for rational rates of convergence to periodic solutions in the case where the convergence fails to be uniformly exponential. We illustrate our general results by applying them to concrete problems including the one-dimensional wave equation with periodic damping.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, St Giles
Contributors: Paunonen, L., Seifert, D.
Pages: 7152-7172
Publication date: May 2019
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: Journal of Differential Equations
Volume: 266
Issue number: 11
ISSN (Print): 0022-0396
Original language: English
ASJC Scopus subject areas: Analysis, Applied Mathematics
Keywords: Damped wave equation, Evolution family, Non-autonomous system, Periodic, Rates of convergence, Ritt operator
Electronic versions: 
URLs: 
Source: Scopus
Source ID: 85057519870

Research output: Contribution to journalArticleScientificpeer-review

A topological algorithm for identification of structural domains of proteins

Background: Identification of the structural domains of proteins is important for our understanding of the organizational principles and mechanisms of protein folding, and for insights into protein function and evolution. Algorithmic methods of dissecting protein of known structure into domains developed so far are based on an examination of multiple geometrical, physical and topological features. Successful as many of these approaches are, they employ a lot of heuristics, and it is not clear whether they illuminate any deep underlying principles of protein domain organization. Other well-performing domain dissection methods rely on comparative sequence analysis. These methods are applicable to sequences with known and unknown structure alike, and their success highlights a fundamental principle of protein modularity, but this does not directly improve our understanding of protein spatial structure. Results: We present a novel graph-theoretical algorithm for the identification of domains in proteins with known three-dimensional structure. We represent the protein structure as an undirected, unweighted and unlabeled graph whose nodes correspond to the secondary structure elements and edges represent physical proximity of at least one pair of alpha carbon atoms from two elements. Domains are identified as constrained partitions of the graph, corresponding to sets of vertices obtained by the maximization of the cycle distributions found in the graph. When a partition is found, the algorithm is iteratively applied to each of the resulting subgraphs. The decision to accept or reject a tentative cut position is based on a specific classifier. The algorithm is applied iteratively to each of the resulting subgraphs and terminates automatically if partitions are no longer accepted. The distribution of cycles is the only type of information on which the decision about protein dissection is based. Despite the barebone simplicity of the approach, our algorithm approaches the best heuristic algorithms in accuracy. Conclusion: Our graph-theoretical algorithm uses only topological information present in the protein structure itself to find the domains and does not rely on any geometrical or physical information about protein molecule. Perhaps unexpectedly, these drastic constraints on resources, which result in a seemingly approximate description of protein structures and leave only a handful of parameters available for analysis, do not lead to any significant deterioration of algorithm accuracy. It appears that protein structures can be rigorously treated as topological rather than geometrical objects and that the majority of information about protein domains can be inferred from the coarse-grained measure of pairwise proximity between elements of secondary structure elements.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Stowers Institute for Medical Research, University of Kansas Medical Center
Contributors: Emmert-Streib, F., Mushegian, A.
Publication date: 3 Jul 2007
Peer-reviewed: Yes

Publication information

Journal: BMC Bioinformatics
Volume: 8
Article number: 237
ISSN (Print): 1471-2105
Ratings: 
  • Scopus rating (2007): SJR 1.973 SNIP 1.12
Original language: English
ASJC Scopus subject areas: Medicine(all), Structural Biology, Applied Mathematics
Source: Scopus
Source ID: 34547667016

Research output: Contribution to journalArticleScientificpeer-review

Bio-inspired service management framework: Green data-centres case study

The internet is evolving into a full-scale distributed service platform, offering a plethora of services from communications to business, entertainment, social connectivity and much more. The range of services and applications offered is diversifying, with new applications constantly emerging. For example, utility-based computing (e.g. HPC and cloud computing) which relies heavily on data-centre resources. These services will be more dynamic and sophisticated, providing a range of complex capabilities, which puts further burden on datacentres, in terms of supporting and managing these services. At the same time, society is becoming acutely aware of the significant energy burden the communications industry, and in particular data-centres, are becoming. With these trends in mind we propose a biologically inspired service framework that supports services which can autonomously carry out management functions. We then apply this framework to address the emerging problem of a sustainable future internet by autonomously migrating services to greener locations.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Wireless Communications and Positioning (WICO), Waterford Institute of Technology, Telecommunications Software and Systems Group (TSSG), University of Massachusetts Boston, Imperial College London and Nanyang Technological University
Contributors: Carroll, R., Balasubramaniam, S., Suzuki, J., Lee, C., Donnelly, W., Botvich, D.
Number of pages: 15
Pages: 278-292
Publication date: 2013
Peer-reviewed: Yes

Publication information

Journal: International Journal of Grid and Utility Computing
Volume: 4
Issue number: 4
ISSN (Print): 1741-847X
Ratings: 
  • Scopus rating (2013): CiteScore 0.81 SJR 0.176 SNIP 0.858
Original language: English
ASJC Scopus subject areas: Management Information Systems, Computer Science Applications, Applied Mathematics
Keywords: Bio-inspired services, Genetic algorithm, Green data-centres
Source: Scopus
Source ID: 84886912413

Research output: Contribution to journalArticleScientificpeer-review

Capacity of Multiconnectivity mmWave Systems with Dynamic Blockage and Directional Antennas

The challenges of millimeter-wave (mmWave) radio propagation in dense crowded environments require dynamic re-associations between the available access points (APs) to reduce the chances of losing the line-of-sight path. However, the antenna beamsearching functionality in the mmWave systems may introduce significant delays in the course of AP re-association. In this paper, we analyze user performance in dense urban mmWave deployments that are susceptible to blockage by the dynamically moving crowd. Our approach relies on the ergodic capacity as the key parameter of interest. We conduct a detailed evaluation with respect to the impact of various system parameters on the ergodic capacity, such as AP density and height, blocker density and speed, number of antenna array elements, array switching time, degree of multiconnectivity, and employed connectivity strategies. Particularly, we demonstrate that dual connectivity delivers the desired performance out of all possible degrees of multiconnectivity, and there is an optimal density of mmWave APs that maximizes the capacity of cell-edge users. We also show that the use of low complexity 'reactive' multiconnectivity design, where the beamtracking is only performed when the currently active connection is lost, together with the utilization of iterative beamsearching algorithms, does not significantly deteriorate the ergodic capacity.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Engineering, National Research University Higher School of Economics
Contributors: Gerasimenko, M., Moltchanov, D., Gapeyenko, M., Andreev, S., Koucheryavy, Y.
Number of pages: 16
Pages: 3534-3549
Publication date: 1 Apr 2019
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 68
Issue number: 4
ISSN (Print): 0018-9545
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Millimeter wave communication, 5G mobile communication, beam steering, multi-connectivity, dynamic blockage
Source: Scopus
Source ID: 85064628647

Research output: Contribution to journalArticleScientificpeer-review

Cauchy–Riemann Operators in Octonionic Analysis

In this paper we first recall the definition of the octonion algebra and its algebraic properties. We derive the so called e4-calculus and using it we obtain the list of generalized Cauchy–Riemann systems for octonionic monogenic functions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, Research group: Computer Science and Applied Logics, Civil Engineering
Contributors: Kauhanen, J., Orelma, H.
Publication date: 2018
Peer-reviewed: Yes
Early online date: Jan 2018

Publication information

Journal: Advances in Applied Clifford Algebras
Volume: 28
Issue number: 1
Article number: 1
ISSN (Print): 0188-7009
Ratings: 
  • Scopus rating (2018): CiteScore 0.9 SJR 0.4 SNIP 0.899
Original language: English
ASJC Scopus subject areas: Applied Mathematics
Keywords: Cauchy–Riemann operators, Dirac operators, Monogenic functions, Octonions
Electronic versions: 
Source: Scopus
Source ID: 85041309780

Research output: Contribution to journalArticleScientificpeer-review

Characterization and Performance Improvement of Cooperative Wireless Networks with Nonlinear Power Amplifier at Relay

In this paper, the performance of the cooperative cognitive radio network with the amplify-and-forward protocol is studied when the relay uses a nonlinear power amplifier (NLPA). Furthermore, taking the pulse shaping filter for the data signal into account, the power of the adjacent channel interference (ACI) to the primary users (PUs) caused by the spectral regrowth of the relay output signal is analytically calculated. Moreover, two compensation techniques are proposed which are implemented at the destination receiver to deal with the in-band nonlinear interference. The first technique is based on the calculation of the distorted signal constellation to enhance the performance of the demodulator. The second technique is feedforward compensation at the receiver. The bit error rate (BER) expressions for both techniques are presented. The ACI resulting from the spectral regrowth due to the relay NLPA is investigated by the simulation and numerical studies, and then, the BER performance degradation at the destination node and the performance improvement resulting from the proposed compensation methods are evaluated. Since the ACI confines the transmit power due to the interference power constraint of the PU, the achievable BER of the secondary user (SU) is studied. The simulation results show that the feedforward compensation technique has better BER performance than the modified constellation based approach.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Engineering, University of Kashan, Amirkabir University of Technology
Contributors: Majidi, M., Mohammadi, A., Abdipour, A., Valkama, M.
Number of pages: 12
Pages: 3244-3255
Publication date: 1 Mar 2020
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 69
Issue number: 3
Article number: 8951265
ISSN (Print): 0018-9545
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Electrical and Electronic Engineering, Applied Mathematics
Keywords: Amplify and forward, cognitive radio, maximum ratio combining, nonlinearity compensation, power amplifier nonlinearity
Source: Scopus
Source ID: 85082043909

Research output: Contribution to journalArticleScientificpeer-review

Characterization of Radio Links at 60 GHz Using Simple Geometrical and Highly Accurate 3-D Models

In order to effectively deploy high data rate millimeter-wave communication systems in urban environments, accurate information about the radio-wave propagation channel is essential. Radio-wave propagation in urban scenarios strongly depends on the topography of the immediate surroundings. A measurement campaign has been carried out to evaluate the impact of propagation effects on the radio channel at the rooftop level of buildings. In the simulation part of the paper, we present two 3-D models produced with different techniques: first, a simple geometrical model and, second, a highly accurate close-range photogrammetry model; the latter replicates the detailed building geometry. To construct a highly accurate 3-D model, images obtained by an unmanned aerial vehicle were utilized together with the photogrammetry technique. In this paper, we provide a thorough comparison between the measured and the simulated power delay profiles by conducting shooting-and-bouncing ray-based simulations for the rooftop scenario using two 3-D models of different accuracy. The results show that the use of the close-range photogrammetry model can provide better propagation prediction at millimeter-wave frequencies.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Emerging Technologies for Nano-Bio-Info-Cogno, Aalto University
Contributors: Semkin, V., Solomitckii, D., Naderpour, R., Andreev, S., Koucheryavy, Y., Räisänen, A. V.
Number of pages: 10
Pages: 4647-4656
Publication date: 1 Jun 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 66
Issue number: 6
ISSN (Print): 0018-9545
Ratings: 
  • Scopus rating (2017): CiteScore 4.69 SJR 0.75 SNIP 2.059
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Computer Networks and Communications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Millimeter-wave, photogrammetry, radio-wave propagation, ray-based simulations, unmanned aerial vehicle (UAV)
Source: Scopus
Source ID: 85028773753

Research output: Contribution to journalArticleScientificpeer-review

Characterizing Radio Wave Propagation in Urban Street Canyon with Vehicular Blockage at 28 GHz

The communications between two driving vehicles along a narrow street may be limited by the presence of a third vehicle blocking the transmission. In this work, we investigate radio wave propagation at 28 GHz in an urban street canyon scenario by conducting channel measurements, where the vehicle(s) occlude(s) the line-of-sight path. We quantify the impact of the car blockage and study the alternative propagation paths, which can be used for establishing a data link. Based on the obtained results, we report that besides the low-loss (3.4 dB) reflection from the wall, a radio link through the blocking car may potentially be established for data sharing. Specifically, the attenuation through clear windows is 2 dB, while the attenuation caused by sun protective film is 15 dB. Diffraction over the car and propagation in foliage reduce the multipath power drastically by 21-24 dB and 16-19 dB, respectively, and cannot be associated with reliable links. Finally, measurement results were compared with the ray-based simulation data, which demonstrate agreement to within ± 4.3 dB of measured losses.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Engineering, Research group: Wireless Communications and Positioning, Department of Chemistry and Bioengineering, Aalto University, Intel Corporation
Contributors: Solomitckii, D., Koucheryavy, Y., Semkin, V., Karttunen, A., Petrov, V., Nguyen, S. L. H., Nikopour, H., Haneda, K., Andreev, S., Talwar, S.
Number of pages: 10
Pages: 1227-1236
Publication date: 1 Feb 2020
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 69
Issue number: 2
ISSN (Print): 0018-9545
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Electrical and Electronic Engineering, Applied Mathematics
Keywords: 5G vehicular scenarios, blockage, Millimeter-wave, multipath, propagation losses, radio wave propagation
Source: Scopus
Source ID: 85079816735

Research output: Contribution to journalArticleScientificpeer-review

Comparative evaluation of gene set analysis approaches for RNA-Seq data

Background: Over the last few years transcriptome sequencing (RNA-Seq) has almost completely taken over microarrays for high-throughput studies of gene expression. Currently, the most popular use of RNA-Seq is to identify genes which are differentially expressed between two or more conditions. Despite the importance of Gene Set Analysis (GSA) in the interpretation of the results from RNA-Seq experiments, the limitations of GSA methods developed for microarrays in the context of RNA-Seq data are not well understood. Results: We provide a thorough evaluation of popular multivariate and gene-level self-contained GSA approaches on simulated and real RNA-Seq data. The multivariate approach employs multivariate non-parametric tests combined with popular normalizations for RNA-Seq data. The gene-level approach utilizes univariate tests designed for the analysis of RNA-Seq data to find gene-specific -values and combines them into a pathway -value using classical statistical techniques. Our results demonstrate that the Type I error rate and the power of multivariate tests depend only on the test statistics and are insensitive to the different normalizations. In general standard multivariate GSA tests detect pathways that do not have any bias in terms of pathways size, percentage of differentially expressed genes, or average gene length in a pathway. In contrast the Type I error rate and the power of gene-level GSA tests are heavily affected by the methods for combining -values, and all aforementioned biases are present in detected pathways. Conclusions: Our result emphasizes the importance of using self-contained non-parametric multivariate tests for detecting differentially expressed pathways for RNA-Seq data and warns against applying gene-level GSA tests, especially because of their high level of Type I error rates for both, simulated and real data.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), University of Arkansas for Medical Sciences, Computational Biology and Machine Learning, Queen's University, Belfast, Northern Ireland
Contributors: Rahmatallah, Y., Emmert-Streib, F., Glazko, G.
Publication date: 5 Dec 2014
Peer-reviewed: Yes

Publication information

Journal: BMC Bioinformatics
Volume: 15
Issue number: 1
Article number: 397
ISSN (Print): 1471-2105
Ratings: 
  • Scopus rating (2014): CiteScore 2.91 SJR 1.916 SNIP 1.185
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Structural Biology, Biochemistry, Molecular Biology, Computer Science Applications
Source: Scopus
Source ID: 84923922737

Research output: Contribution to journalArticleScientificpeer-review

Comparing large graphs efficiently by margins of feature vectors

Measuring the structural similarity of graphs is a challenging and outstanding problem. Most of the classical approaches of the so-called exact graph matching methods are based on graph or subgraph isomorphic relations of the underlying graphs. In contrast to these methods in this paper we introduce a novel approach to measure the structural similarity of directed and undirected graphs that is mainly based on margins of feature vectors representing graphs. We introduce novel graph similarity and dissimilarity measures, provide some properties and analyze their algorithmic complexity. We find that the computational complexity of our measures is polynomial in the graph size and, hence, significantly better than classical methods from, e.g. exact graph matching which are NP-complete. Numerically, we provide some examples of our measure and compare the results with the well-known graph edit distance.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: University of Veterinary Medicine Vienna, Stowers Institute for Medical Research
Contributors: Dehmer, M., Emmert-Streib, F.
Number of pages: 12
Pages: 1699-1710
Publication date: 15 May 2007
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 188
Issue number: 2
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2007): SJR 0.869 SNIP 1.113
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics, Numerical Analysis
Keywords: Degree vectors, Directed and undirected graphs, Graph similarity, Similarity measures
Source: Scopus
Source ID: 34248165422

Research output: Contribution to journalArticleScientificpeer-review

Continuum approach to high-cycle fatigue. The finite life-time case with stochastic stress history

In this paper, we consider continuum approach for high-cycle fatigue in the case where life-time is finite. The method is based on differential equations and all basic concepts are explained. A stress history is assumed to be a stochastic process and this leads us to the theory of stochastic differential equations. The life-time is a quantity, which tells us when the breakdown of the material happens. In this method, it is naturally a random variable. The basic assumption is, that the distribution of the life-time is log-normal or Weibull. We give a numerical basic example to demonstrate the method.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computing Sciences
Contributors: Orelma, H.
Number of pages: 12
Pages: 452-463
Publication date: 2019
Peer-reviewed: Yes

Publication information

Journal: Vestnik Samarskogo Gosudarstvennogo Tekhnicheskogo Universiteta, Seriya Fiziko-Matematicheskie Nauki
Volume: 23
Issue number: 3
ISSN (Print): 1991-8615
Original language: English
ASJC Scopus subject areas: Mechanics of Materials, Condensed Matter Physics, Mathematical Physics, Modelling and Simulation, Analysis, Applied Mathematics, Software
Keywords: Evolution equation, High-cycle fatigue, Life-time
Source: Scopus
Source ID: 85079143163

Research output: Contribution to journalArticleScientificpeer-review

Customized dimensional analysis conceptual modelling framework for design optimization—a case study on the cross-flow micro turbine model

Dimensional Analysis Conceptual Modelling (DACM) is a framework used for conceptual modelling and simulation in system and product designs. The framework is based on cause–effect analysis between variables and functions in a problem. This article presents an approach that mobilizes concepts from the DACM framework to assist solve high-dimensional expensive optimization problems with lower computational costs. The latter fundamentally utilizes theories and concepts from well-practised dimensional analysis, functional modelling and bond graphing. Statistical design-of-experiments theory is also utilized in the framework to measure impact levels of variables towards the objective. Simplifying as well as decomposing followed by optimization of expensive problems are the focuses of the article. To illustrate the approach, a case study on the performance optimization of a cross-flow micro hydro turbine is presented. The customized DACM framework assisted optimization approach converges faster and returns better results than the one without. A single-step simplification approach is employed in the case study and it returns a better average optimization result with about only one fifth of the function evaluations compared to optimization using the original model.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mechanical Engineering and Industrial Systems, Research area: Manufacturing and Automation, University of Stavanger, Simon Fraser University
Contributors: Woldemariam, E. T., Coatanéa, E., Wang, G. G., Lemu, H. G., Wu, D.
Pages: 1168-1184
Publication date: 2019
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: Engineering Optimization
Volume: 51
Issue number: 7
ISSN (Print): 0305-215X
Original language: English
ASJC Scopus subject areas: Computer Science Applications, Management Science and Operations Research, Control and Optimization, Industrial and Manufacturing Engineering, Applied Mathematics
Keywords: Causality analysis, conceptual modelling, DACM assisted optimization, high-dimensional optimization, micro cross-flow turbine
Source: Scopus
Source ID: 85054818014

Research output: Contribution to journalArticleScientificpeer-review

Damped Posterior Linearization Filter

In this letter, we propose an iterative Kalman type algorithm based on posterior linearization. The proposed algorithm uses a nested loop structure to optimize the mean of the estimate in the inner loop and update the covariance, which is a computationally more expensive operation, only in the outer loop. The optimization of the mean update is done using a damped algorithm to avoid divergence. Our simulations show that the proposed algorithm is more accurate than existing iterative Kalman filters.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Automation and Hydraulic Engineering, Lab of Electrical and Automation, University of Liverpool
Contributors: Raitoharju, M., Svensson, L., Garcia-Fernandez, A. F., Piche, R.
Publication date: 2018
Peer-reviewed: Yes
Early online date: 13 Feb 2018

Publication information

Journal: IEEE Signal Processing Letters
Volume: 25
Issue number: 4
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2018): CiteScore 4.37 SJR 0.785 SNIP 1.88
Original language: English
ASJC Scopus subject areas: Signal Processing, Electrical and Electronic Engineering, Applied Mathematics
Keywords: Bayesian state estimation, Computational modeling, Convergence, Cost function, estimation, Kalman filters, Noise measurement, nonlinear, Signal processing algorithms
Electronic versions: 

Bibliographical note

EXT="Raitoharju, Matti"

Source: Scopus
Source ID: 85042110206

Research output: Contribution to journalArticleScientificpeer-review

Data augmentation approaches for improving animal audio classification

In this paper we present ensembles of classifiers for automated animal audio classification, exploiting different data augmentation techniques for training Convolutional Neural Networks (CNNs). The specific animal audio classification problems are i) birds and ii) cat sounds, whose datasets are freely available. We train five different CNNs on the original datasets and on their versions augmented by four augmentation protocols, working on the raw audio signals or their representations as spectrograms. We compared our best approaches with the state of the art, showing that we obtain the best recognition rate on the same datasets, without ad hoc parameter optimization. Our study shows that different CNNs can be trained for the purpose of animal audio classification and that their fusion works better than the stand-alone classifiers. To the best of our knowledge this is the largest study on data augmentation for CNNs in animal audio classification audio datasets using the same set of classifiers and parameters. Our MATLAB code is available at https://github.com/LorisNanni.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: BioMediTech, Research group: Computational Biophysics and Imaging Group, Universita degli Studi di Padova, Italy
Contributors: Nanni, L., Maguolo, G., Paci, M.
Number of pages: 8
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: Ecological Informatics
Volume: 57
Article number: 101084
ISSN (Print): 1574-9541
Original language: English
ASJC Scopus subject areas: Ecology, Evolution, Behavior and Systematics, Ecology, Modelling and Simulation, Ecological Modelling, Computer Science Applications, Computational Theory and Mathematics, Applied Mathematics
Keywords: Acoustic features, Animal audio, Audio classification, Data augmentation, Ensemble of classifiers, Pattern recognition
URLs: 
Source: Scopus
Source ID: 85082116223

Research output: Contribution to journalArticleScientificpeer-review

Development of a constant dilution sampling system for particulate and gaseous pollutant measurements

This paper presents a new concept of a partial flow sampling system (PFSS), involving a two-stage diluter which operates on the principle of underpressure, while exhaust is sampled through a capillary. Due to the low flowrate through the capillary, the diluter may be sampling from a freely exhausting tailpipe and is not prone to pressure variations in the exhaust line. In addition, the PFSS operates at constant pressure conditions even upstream of diesel particle filters that increase the backpressure in the tailpipe. As a result, the PFSS offers a constant dilution ratio (DR) over any engine or vehicle operation condition. This study presents the diluter concept and a straightforward model developed to calculate the DR, depending on the dilution air flowrate and the diluter underpressure. The model is validated using CO2 as a trace gas, and very good agreement is demonstrated between the calculated and the measured DR values. Following validation, the PFSS is combined with aerosol measurement instruments to measure the exhaust particle concentration of a diesel engine operating at different steady-state modes. For demonstrating the stability of the DR and applicability of the PFSS, measurements are conducted with both heavy duty and light duty diesel exhaust gases. Future applications of this device include gas and particle exhaust measurements both in laboratory environments and on-board vehicles.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Urban circular bioeconomy (UrCirBio), Aristotle University of Thessaloniki, Laboratory of Applied Thermodynamics, Dekati Ltd
Contributors: Tzamkiozis, T., Ntziachristos, L., Amanatidis, S., Niemelä, V., Ukkonen, A., Samaras, Z.
Publication date: Aug 2013
Peer-reviewed: Yes

Publication information

Journal: Measurement Science and Technology
Volume: 24
Issue number: 8
Article number: 085801
ISSN (Print): 0957-0233
Ratings: 
  • Scopus rating (2013): CiteScore 1.53 SJR 0.639 SNIP 1.417
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Instrumentation
Source: Scopus
Source ID: 84880789628

Research output: Contribution to journalArticleScientificpeer-review

Development of artificial neuronal networks for molecular communication

Communication at the nanoscale can enhance capabilities for nanodevices, and at the same time open new opportunities for numerous healthcare applications. One approach toward enabling communication between nanodevices is through molecular communications. While a number of solutions have been proposed for molecular communication (e.g. calcium signaling, molecular motors, bacteria communication), in this paper, we propose the use of neuronal networks for molecular communication network. In particular, we provide two design aspects of neuron networks, which includes, (i) the design of an interface between nanodevice and neurons that can initiate signaling, and (ii) the design of transmission scheduling to ensure that signals initiated by multiple devices will successfully reach the receiver with minimum interference. The solution for (i) is developed through wet lab experiments, while the solution for (ii) is developed through genetic algorithm optimization technique, and is validated through simulations.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Wireless Communications and Positioning (WICO), Telecommunications Software and Systems Group (TSSG), Waterford Institute of Technology, Trinity College Dublin, Chalmers University of Technology
Contributors: Balasubramaniam, S., Boyle, N. T., Della-Chiesa, A., Walsh, F., Mardinoglu, A., Botvich, D., Prina-Mello, A.
Number of pages: 11
Pages: 150-160
Publication date: Jun 2011
Peer-reviewed: Yes

Publication information

Journal: Nano Communication Networks
Volume: 2
Issue number: 2-3
ISSN (Print): 1878-7789
Ratings: 
  • Scopus rating (2011): CiteScore 2.15 SJR 0.282 SNIP 1.673
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computer Networks and Communications, Electrical and Electronic Engineering
Keywords: Molecular communications, Neuron networks, Scheduling
Source: Scopus
Source ID: 80052538220

Research output: Contribution to journalArticleScientificpeer-review

Diffusion and Fokker-Planck-Smoluchowski equations with generalized memory kernel

We consider anomalous stochastic processes based on the renewal continuous time random walk model with different forms for the probability density of waiting times between individual jumps. In the corresponding continuum limit we derive the generalized diffusion and Fokker-Planck- Smoluchowski equations with the corresponding memory kernels. We calculate the qth order moments in the unbiased and biased cases, and demonstrate that the generalized Einstein relation for the considered dynamics remains valid. The relaxation of modes in the case of an external harmonic potential and the convergence of the mean squared displacement to the thermal plateau are analyzed.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics, Institute for Physics and Astronomy, University of Potsdam, Radiation Safety Directorate, Akhiezer Institute for Theoretical Physics, Max-Planck Institute for the Physics of Complex Systems
Contributors: Sandev, T., Chechkin, A., Kantz, H., Metzler, R.
Number of pages: 33
Pages: 1006-1038
Publication date: 1 Aug 2015
Peer-reviewed: Yes

Publication information

Journal: Fractional Calculus and Applied Analysis
Volume: 18
Issue number: 4
ISSN (Print): 1311-0454
Ratings: 
  • Scopus rating (2015): CiteScore 2.41 SJR 1.551 SNIP 1.52
Original language: English
ASJC Scopus subject areas: Analysis, Applied Mathematics
Keywords: anomalous diffusion, continuous time random walk (CTRW), Fokker- Planck-Smoluchowski equation, Mittag-Leffler functions, multi-scaling
Source: Scopus
Source ID: 84939133175

Research output: Contribution to journalArticleScientificpeer-review

Dimensionality reduction for data visualization

Dimensionality reduction is one of the basic operations in the toolbox of data analysts and designers of machine learning and pattern recognition systems. Given a large set of measured variables but few observations, an obvious idea is to reduce the degrees of freedom in the measurements by representing them with a smaller set of more condensed variables. Another reason for reducing the dimensionality is to reduce computational load in further processing. A third reason is visualization.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Aalto University
Contributors: Kaski, S., Peltonen, J.
Number of pages: 5
Pages: 100-104
Publication date: Mar 2011
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Magazine
Volume: 28
Issue number: 2
Article number: 5714379
ISSN (Print): 1053-5888
Ratings: 
  • Scopus rating (2011): CiteScore 6.44 SJR 2.164 SNIP 5.856
Original language: English
ASJC Scopus subject areas: Signal Processing, Music, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Data models, Data visualization, Information retrieval, Machine learning, Manifolds, Probabilistic logic, Visualization

Research output: Contribution to journalArticleScientificpeer-review

Early analysis of resource consumption patterns in mobile applications

Mobile device capabilities have increased tremendously in recent years, and the complexity of the applications executed in these devices has evolved accordingly. However, despite the efforts made by mobile manufactures, resource consumption, particularly battery and data traffic, are still limiting factors for mobile applications. The most important aspects determining the consumption of a mobile application is its software architecture and its behaviour. Hence, by comparing the resource consumption of different software architectures before an application is built, mobile developers can make decisions that are better informed. This work presents the consumption analysis of two applications, each of them built with two different architectures in order to identify under which situation each architecture is more efficient. In addition, by generalizing the analysis of the two applications, a conceptual framework is created with which to analyse the consumption pattern of applications in their early development phases. This conceptual framework will allow mobile developers to estimate the resource consumption of their applications under different conditions of software architecture and usage scenarios, providing them with information relevant for decision making.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Pervasive Computing, Research area: Software engineering, Universidad de Extremadura, UNIVERSIDAD DE MALAGA
Contributors: Berrocal, J., Garcia-Alonso, J., Vicente-Chicote, C., Hernández, J., Mikkonen, T., Canal, C., Murillo, J. M.
Pages: 32–50
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: Pervasive and Mobile Computing
Volume: 35
ISSN (Print): 1574-1192
Ratings: 
  • Scopus rating (2017): CiteScore 3.35 SJR 0.368 SNIP 1.82
Original language: English
ASJC Scopus subject areas: Computer Science (miscellaneous), Applied Mathematics
Keywords: Mobile software architecture, Mobile-centric, Resource consumption, Resource estimation
Source: Scopus
Source ID: 84979658407

Research output: Contribution to journalArticleScientificpeer-review

Efficient Noise Variance Estimation under Pilot Contamination for Large-Scale MIMO Systems

Massive multiple-input multiple-output (MIMO) is expected to be one of the enabling technologies for fifth generation (5G) cellular networks. One of the major challenges in massive MIMO systems is the accurate joint estimation of the channel and noise variance, which significantly affects the performance of wireless communications in practical scenarios. In this paper, we first derive a novel maximum likelihood (ML) estimator for the noise variance at the receiver of massive MIMO systems considering practical impairments such as pilot contamination. Then, this estimate is used to compute the minimum mean square error (MMSE) estimate of the channel. In order to measure the performance of the proposed noise variance estimator, we derive the corresponding Cramer-Rao lower bound (CRLB). Simulation results show that the estimator is efficient in certain scenarios, outperforming existing approaches in the literature. Furthermore, we develop the estimator and CRLB for equal and different noise variance at the receive antennas. Although the proposed estimator is valid for all antenna array sizes, its use is particularly effective for massive MIMO systems.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Florida International University, North Carolina State University
Contributors: Iscar Vergara, J., Guvenc, I., Dikmese, S., Rupasinghe, N.
Pages: 2982-2996
Publication date: 2018
Peer-reviewed: Yes
Early online date: 24 Oct 2017

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 67
Issue number: 4
ISSN (Print): 0018-9545
Ratings: 
  • Scopus rating (2018): CiteScore 6.29 SJR 1.089 SNIP 2.256
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: 5G, Channel estimation, Contamination, Covariance matrices, CRLB, massive MIMO, maximum likelihood, Maximum likelihood estimation, method of moments, MIMO, MMSE channel estimation, noise variance estimation, Partial transmit sequences, pilot contamination
Source: Scopus
Source ID: 85032440423

Research output: Contribution to journalArticleScientificpeer-review

Energy Efficiency Maximization of Full-Duplex Two-Way Relay with Non-Ideal Power Amplifiers and Non-Negligible Circuit Power

In this paper, we maximize the energy efficiency (EE) of full-duplex (FD) two-way relay (TWR) systems under non-ideal power amplifiers (PAs) and non-negligible transmission-dependent circuit power. We start with the case where only the relay operates full duplex and two timeslots are required for TWR. Then, we extend to the advanced case, where the relay and the two nodes all operate full duplex, and accomplish TWR in a single timeslot. In both cases, we establish the intrinsic connections between the optimal transmit powers and durations, based on which the original non-convex EE maximization can be convexified and optimally solved. Simulations show the superiority of FD-TWR in terms of EE, especially when traffic demand is high. The simulations also reveal that the maximum EE of FD-TWR is more sensitive to the PA efficiency, than it is to self-cancellation. The full FD design of FD-TWR is susceptible to traffic imbalance, while the design with only the relay operating in the FD mode exhibits strong tolerance.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Beijing University of Posts and Telecommunications, CSIRO Energy Centre, Aalto University
Contributors: Cui, Q., Zhang, Y., Ni, W., Valkama, M., Jantti, R.
Number of pages: 15
Pages: 6264-6278
Publication date: 1 Sep 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Wireless Communications
Volume: 16
Issue number: 9
ISSN (Print): 1536-1276
Ratings: 
  • Scopus rating (2017): CiteScore 6.43 SJR 1.246 SNIP 2.451
Original language: English
ASJC Scopus subject areas: Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Energy efficiency, full-duplex, non-ideal power amplifier, non-negligible circuit power, two-way relay
Source: Scopus
Source ID: 85023192668

Research output: Contribution to journalArticleScientificpeer-review

Energy-efficient and high-precision control of hydraulic robots

In addition to high-precision closed-loop control performance, energy efficiency is another vital characteristic in field-robotic hydraulic systems as energy source(s) must be carried on board in limited space. This study proposes an energy-efficient and high-precision closed-loop controller for the highly nonlinear hydraulic robotic manipulators. The proposed method is twofold: 1) A possibility for energy consumption reduction is realized by using a separate meter-in separate meter-out (SMISMO) control set-up, enabling an independent metering (pressure control) of each chamber in hydraulic actuators. 2) A novel subsystem-dynamics-based and modular controller is designed for the system actuators, and it is integrated to the previously designed state-of-the-art controller for multiple degrees-of-freedom (n-DOF) manipulators. Stability of the overall controller is rigorously proven. The comparative experiments with a three-DOF redundant hydraulic robotic manipulator (with a payload of 475 kg) demonstrate that: 1) It is possible to design the triple objective of high-precision piston position, piston force and chamber pressure trackings for the hydraulic actuators. 2) In relation to the previous SMISMO-control methods, unprecedented motion and chamber pressure tracking performances are reported. 3) In comparison to the state-of-the-art motion tracking controller with a conventional energy-inefficient servovalve control, the actuators’ energy consumption is reduced by 45% without noticeable motion control (position-tracking) deterioration.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research group: Innovative Hydraulic Automation, Automation Technology and Mechanical Engineering, Canadian Space Agency
Contributors: Koivumäki, J., Zhu, W. H., Mattila, J.
Number of pages: 18
Pages: 176-193
Publication date: 1 Apr 2019
Peer-reviewed: Yes

Publication information

Journal: Control Engineering Practice
Volume: 85
ISSN (Print): 0967-0661
Original language: English
ASJC Scopus subject areas: Control and Systems Engineering, Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: Energy efficiency, Hydraulic robots, Independent metering, Nonlinear control, SMISMO control, Stability analysis
Electronic versions: 
Source: Scopus
Source ID: 85061341920

Research output: Contribution to journalArticleScientificpeer-review

Entropy analysis of word-length series of natural language texts: Effects of text language and genre

We estimate the n-gram entropies of natural language texts in word-length representation and find that these are sensitive to text language and genre. We attribute this sensitivity to changes in the probability distribution of the lengths of single words and emphasize the crucial role of the uniformity of probabilities of having words with length between five and ten. Furthermore, comparison with the entropies of shuffled data reveals the impact of word length correlations on the estimated n-gram entropies.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Multi-scaled biodata analysis and modelling (MultiBAM), University of Athens, Institute of Microelectronics, Athens, Institute for Language and Speech Processing, Athena R.C.
Contributors: Kalimeri, M., Constantoudis, V., Papadimitriou, C., Karamanos, K., Diakonos, F. K., Papageorgiou, H.
Publication date: Sep 2012
Peer-reviewed: Yes

Publication information

Journal: INTERNATIONAL JOURNAL OF BIFURCATION AND CHAOS
Volume: 22
Issue number: 9
Article number: 1250223
ISSN (Print): 0218-1274
Ratings: 
  • Scopus rating (2012): CiteScore 1.04 SJR 0.551 SNIP 0.772
Original language: English
ASJC Scopus subject areas: Applied Mathematics, General, Engineering(all), Modelling and Simulation
Keywords: N-gram entropies, Quantitative linguistics, Symbolic dynamics, Time series, Word-length representation

Bibliographical note

EXT="Kalimeri, Maria"

Source: Scopus
Source ID: 84867518276

Research output: Contribution to journalArticleScientificpeer-review

Entropy and Channel Capacity under Optimum Power and Rate Adaptation over Generalized Fading Conditions

Accurate fading characterization and channel capacity determination are of paramount importance in both conventional and emerging communication systems. The present work addresses the non-linearity of the propagation medium and its effects on the channel capacity. Such fading conditions are first characterized using information theoretic measures, namely, Shannon entropy, cross entropy and relative entropy. The corresponding effects on the channel capacity with and without power adaptation are then analyzed. Closed-form expressions are derived and validated through computer simulations. It is shown that the effects of nonlinearities are significantly larger than those of fading parameters such as the scattered-wave power ratio, and the correlation coefficient between the in-phase and quadrature components in each cluster of multipath components.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research group: Wireless Communications and Positioning, Department of Electronics and Communications Engineering, Wireless Communications and Positioning (WICO), Department of Electrical Engineering and Computer Science, Aristotle University of Thessaloniki, Department of Electronic Engineering, Khalifa University, Centre for Communication Systems Research, University of Surrey, University of Leeds, International University of Rabat
Contributors: Sofotasios, P. C., Muhaidat, S., Valkama, M., Ghogho, M., Karagiannidis, G. K.
Number of pages: 5
Pages: 2162-2166
Publication date: 1 Nov 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 22
Issue number: 11
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2015): CiteScore 3.13 SJR 0.822 SNIP 1.788
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics
Keywords: Adaptation policies, channel capacity, entropy
Source: Scopus
Source ID: 84939865476

Research output: Contribution to journalArticleScientificpeer-review

Entropy bounds for dendrimers

Many graph invariants have been used for the construction of entropy-based measures to characterize the structure of complex networks. When considering Shannon entropy-based graph measures, there has been very little work to find their extremal values. A reason for this might be the fact that Shannon's entropy represents a multivariate function and all probability values are not equal to zero when considering graph entropies. Dehmer and Kraus proved some extremal results for graph entropies which are based on information functionals and express some conjectures generated by numerical simulations to find extremal values of graph entropies. Dehmer and Kraus discussed the extremal values of entropies for dendrimers. In this paper, we continue to study the extremal values of graph entropy for dendrimers, which has most interesting applications in molecular structure networks, and also in the pharmaceutical and biomedical area. Among all dendrimers with n vertices, we obtain the extremal values of graph entropy based on different well-known information functionals. Numerical experiments verifies our results.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Nankai University, Universität der Bundeswehr München, Computational Biology and Machine Learning, Queen's University, Belfast, Northern Ireland
Contributors: Chen, Z., Dehmer, M., Emmert-Streib, F., Shi, Y.
Number of pages: 11
Pages: 462-472
Publication date: 1 Sep 2014
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 242
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2014): CiteScore 1.86 SJR 0.961 SNIP 1.463
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics
Keywords: Dendrimers, Extremal values, Graph entropy, Information theory, Shannon's entropy
Source: Scopus
Source ID: 84903150191

Research output: Contribution to journalArticleScientificpeer-review

Enzyme-based circuit design for nano-scale computing

Enzyme-based logical gates have been proposed as an alternative to conventional semiconductor gates in order to support computing at the nano-scale for nano-devices. In particular, certain enzyme-based implementations of AND, OR and NOT gates were proposed for further composing enzyme-based circuits for various Boolean functions. However, inputs and outputs of these gates are presented by different chemical species, and this results in potential incompatibility between gates. Therefore, opposite to conventional semiconductor gates not just any pair of enzyme-based logical gates may be used consequently in a circuit. This significantly complicates circuit creation and raises the question of the existence of an enzyme-based circuit for a generic Boolean function. This paper addresses the issue while providing its formal mathematical description together with an algorithm for enzyme-based circuit design.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Wireless Communications and Positioning (WICO), Waterford Institute of Technology, Telecommunications Software and Systems Group (TSSG)
Contributors: Ivanov, S., Botvich, D., Balasubramaniam, S.
Number of pages: 7
Pages: 168-174
Publication date: Sep 2012
Peer-reviewed: Yes

Publication information

Journal: Nano Communication Networks
Volume: 3
Issue number: 3
ISSN (Print): 1878-7789
Ratings: 
  • Scopus rating (2012): CiteScore 2.47 SJR 0.724 SNIP 2.354
Original language: English
ASJC Scopus subject areas: Computer Networks and Communications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Circuit design, Enzyme logic, Nano-scale computing
Source: Scopus
Source ID: 84867739312

Research output: Contribution to journalArticleScientificpeer-review

Estimation of additional losses due to random contacts at the edges of stator of an electrical machine

Purpose - Punching of the electrical sheets impair the insulation and make random galvanic contacts between the edges of the sheets. The purpose of this paper is to model the random galvanic contacts at the stator edges of 37 kW induction machine and estimate the additional losses due to these contacts. Design/methodology/approach - The presence of the surface current at the edges of sheets causes the discontinuity in the tangential component of the magnetic field. The surface boundary layer model which is based on this concept is implemented to model the galvanic contacts at the edges of the sheets. Finite element analysis based on magnetic vector potential was done and theoretical statistical study of the random conductivity at the stator edge was performed using brute force method. Findings - Finite element analysis validates the interlaminar current when galvanic contacts are present at the edges of electrical sheets. The case studies show that the rotor and stator losses increases with the thickness of the contacts. Statistical studies show that the mean value of total electromagnetic loss was increased by 7.7 percent due to random contacts at the edges of sheets. Originality/value - The novel approach for modeling the galvanic contacts at the stator edges of induction machine is discussed in this paper. The hypothesis of interlaminar current due to galvanic contacts is also validated using finite element simulation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Smart Energy Systems (SES), Aalto University
Contributors: Shah, S. B., Rasilo, P., Belahcen, A., Arkkio, A.
Number of pages: 10
Pages: 1501-1510
Publication date: 7 Sep 2015
Peer-reviewed: Yes

Publication information

Journal: COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering
Volume: 34
Issue number: 5
ISSN (Print): 0332-1649
Ratings: 
  • Scopus rating (2015): CiteScore 0.68 SJR 0.231 SNIP 0.554
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Computational Theory and Mathematics, Applied Mathematics
Keywords: Boundary conditions, Eddy current, Electrical conductivity, FEM, Magnetic vector potential
Source: Scopus
Source ID: 84941111680

Research output: Contribution to journalArticleScientificpeer-review

Evolutionary dynamics of the spatial Prisoner's Dilemma with self-inhibition

In this paper we study the influence of interventions on self-interactions in a spatial Prisoner's Dilemma on a two-dimensional grid with periodic boundary conditions and synchronous updating of the dynamics. We investigate two different types of self-interaction modifications. The first type (FSIP) is deterministic, effecting each self-interaction of a player by a constant factor, whereas the second type (PSIP) performs a probabilistic interventions. Both types of interventions lead to a reduction of the payoff of the players and, hence, represent inhibiting effects. We find that a constant but moderate reduction of self-interactions has a very beneficial effect on the evolution of cooperators in the population, whereas probabilistic interventions on self-interactions are in general counter productive for the coexistence of the two different strategies.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Computational Biology and Machine Learning, Queen's University, Belfast, Northern Ireland
Contributors: Emmert-Streib, F.
Number of pages: 7
Pages: 6482-6488
Publication date: 5 Feb 2012
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 218
Issue number: 11
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2012): CiteScore 1.77 SJR 1.02 SNIP 1.295
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics
Keywords: Evolutionary dynamics, Evolutionary game theory, Game theory, Prisoner's dilemma
Source: Scopus
Source ID: 84855904251

Research output: Contribution to journalArticleScientificpeer-review

Forward simulation and inverse dipole localization with the lowest order Raviart - Thomas elements for electroencephalography

Electroencephalography is a non-invasive imaging modality in which a primary current density generated by the neural activity in the brain is to be reconstructed based on external electric potential measurements. This paper focuses on the finite element method (FEM) from both forward and inverse aspects. The goal is to establish a clear correspondence between the lowest order Raviart-Thomas basis functions and dipole sources as well as to show that the adopted FEM approach is computationally effective. Each basis function is associated with a dipole moment and a location. Four candidate locations are tested. Numerical experiments cover two different spherical multilayer head models, four mesh resolutions and two different forward simulation approaches, one based on FEM and another based on the boundary element method (BEM) with standard dipoles as sources. The forward simulation accuracy is examined through column- and matrix-wise relative errors as well as through performance in inverse dipole localization. A closed-form approximation of dipole potential was used as the reference forward simulation. The present approach is compared to the BEM and indirectly also to the recent FEM-based subtraction approach regarding both accuracy, computation time and accessibility of implementation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematical modelling with wide societal impact (MathImpact), Aalto University, Dipartimento di Matematica, Università di Genova, University of Warwick, University of Helsinki, CNR-SPIN
Contributors: Pursiainen, S., Sorrentino, A., Campi, C., Piana, M.
Publication date: Apr 2011
Peer-reviewed: Yes

Publication information

Journal: Inverse Problems
Volume: 27
Issue number: 4
Article number: 045003
ISSN (Print): 0266-5611
Ratings: 
  • Scopus rating (2011): CiteScore 1.9 SJR 1.208 SNIP 1.579
Original language: English
ASJC Scopus subject areas: Theoretical Computer Science, Signal Processing, Mathematical Physics, Computer Science Applications, Applied Mathematics
Source: Scopus
Source ID: 79953662770

Research output: Contribution to journalArticleScientificpeer-review

Frequency domain robust regulation of signals generated by an infinite-dimensional exosystem

This paper deals with frequency domain robust regulation of signals generated by an infinite-dimensional exosystem. The problem is formulated and the stability types are chosen so that one can generalize the existing finite-dimensional theory to more general classes of infinite-dimensional systems and signals. The main results of this article are extensions of the internal model principle, of a necessary and sufficient solvability condition for the robust regulation problem, and of Davison's simple servo compensator for stable plants in the chosen algebraic framework.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Mathematics, Research group: MAT Intelligent Information Systems Laboratory
Contributors: Laakkonen, P., Pohjolainen, S.
Number of pages: 28
Pages: 139-166
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: SIAM Journal on Control and Optimization
Volume: 53
Issue number: 1
ISSN (Print): 0363-0129
Ratings: 
  • Scopus rating (2015): CiteScore 1.92 SJR 2.017 SNIP 1.646
Original language: English
ASJC Scopus subject areas: Control and Optimization, Applied Mathematics
Keywords: Frequency domain, Infinite-dimensional exosystems, Infinite-dimensional systems, Internal model, Robust regulation
Source: Scopus
Source ID: 84923923144

Research output: Contribution to journalArticleScientificpeer-review

Frequency-selective PAPR reduction for OFDM

In this correspondence paper, we study the peak-To-Average power ratio (PAPR) problem in orthogonal frequency-division multiplexing systems. In conventional clipping and filtering based PAPR reduction techniques, clipping noise is allowed to spread over the whole active passband, thus degrading the transmit signal quality similarly at all active subcarriers. However, since modern radio networks support frequency multiplexing of users and services with highly different quality-of-service expectations, clipping noise from PAPR reduction should be distributed unequally over the corresponding physical resource blocks (PRBs). To facilitate this, we present an efficient PAPR reduction technique, where clipping noise can be flexibly controlled and filtered inside the transmitter passband, allowing to control the transmitted signal quality per PRB. Numerical results are provided in 5G new radio mobile network context, demonstrating the flexibility and efficiency of the proposed method.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electrical Engineering
Contributors: Gokceli, S., Levanen, T., Riihonen, T., Renfors, M., Valkama, M.
Number of pages: 5
Pages: 6167-6171
Publication date: 1 Jun 2019
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 68
Issue number: 6
ISSN (Print): 0018-9545
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: 5G New Radio (NR), clipping, filtering, orthogonal frequency-division multiplexing (OFDM), peak-To-Average-power ratio (PAPR), waveform, wireless communications
Source: Scopus
Source ID: 85067791739

Research output: Contribution to journalArticleScientificpeer-review

Functional and genetic analysis of the colon cancer network.

Cancer is a complex disease that has proven to be difficult to understand on the single-gene level. For this reason a functional elucidation needs to take interactions among genes on a systems-level into account. In this study, we infer a colon cancer network from a large-scale gene expression data set by using the method BC3Net. We provide a structural and a functional analysis of this network and also connect its molecular interaction structure with the chromosomal locations of the genes enabling the definition of cis- and trans-interactions. Furthermore, we investigate the interaction of genes that can be found in close neighborhoods on the chromosomes to gain insight into regulatory mechanisms. To our knowledge this is the first study analyzing the genome-scale colon cancer network.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Queen’s University Belfast
Contributors: Emmert-Streib, F., de Matos Simoes, R., Glazko, G., McDade, S., Haibe-Kains, B., Holzinger, A., Dehmer, M., Campbell, F.
Publication date: 2014
Peer-reviewed: Yes

Publication information

Journal: BMC Bioinformatics
Volume: 15
Issue number: Suppl 6
Article number: S6
ISSN (Print): 1471-2105
Ratings: 
  • Scopus rating (2014): CiteScore 2.91 SJR 1.916 SNIP 1.185
Original language: English
ASJC Scopus subject areas: Biochemistry, Molecular Biology, Computer Science Applications, Applied Mathematics, Structural Biology

Research output: Contribution to journalArticleScientificpeer-review

Further hardness results on rainbow and strong rainbow connectivity

A path in an edge-colored graph is rainbow if no two edges of it are colored the same. The graph is said to be rainbow connected if there is a rainbow path between every pair of vertices. If there is a rainbow shortest path between every pair of vertices, the graph is strong rainbow connected. We consider the complexity of the problem of deciding if a given edge-colored graph is rainbow or strong rainbow connected. These problems are called Rainbow connectivity and Strong rainbow connectivity, respectively. We prove both problems remain NP-complete on interval outerplanar graphs and k-regular graphs for k≥3. Previously, no graph class was known where the complexity of the two problems would differ. We show that for block graphs, which form a subclass of chordal graphs, Rainbow connectivity is NP-complete while Strong rainbow connectivity is in P. We conclude by considering some tractable special cases, and show for instance that both problems are in XP when parameterized by tree-depth.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Mathematics
Contributors: Lauri, J.
Pages: 191-200
Publication date: 2016
Peer-reviewed: Yes

Publication information

Journal: Discrete Applied Mathematics
Volume: 201
ISSN (Print): 0166-218X
Ratings: 
  • Scopus rating (2016): CiteScore 1 SJR 0.863 SNIP 1.23
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Discrete Mathematics and Combinatorics
Keywords: Computational complexity, Rainbow connectivity
Source: Scopus
Source ID: 84956591316

Research output: Contribution to journalArticleScientificpeer-review

Geometric solution strategy of Laplace problems with free boundary

This paper introduces a geometric solution strategy for Laplace problems. Our main interest and emphasis is on efficient solution of the inverse problem with a boundary with Cauchy condition and with a free boundary. This type of problem is known to be sensitive to small errors. We start from the standard Laplace problem and establish the geometric solution strategy on the idea of deforming equipotential layers continuously along the field lines from one layer to another. This results in exploiting ordinary differential equations to solve any boundary value problem that belongs to the class of Laplace's problem. Interpretation in terms of a geometric flow will provide us with stability considerations. The approach is demonstrated with several examples.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research area: Electromagnetics, Department of Electrical Engineering
Contributors: Poutala, A., Tarhasaari, T., Kettunen, L.
Number of pages: 24
Pages: 723-746
Publication date: 9 Mar 2016
Peer-reviewed: Yes

Publication information

Journal: International Journal for Numerical Methods in Engineering
Volume: 105
Issue number: 10
ISSN (Print): 0029-5981
Ratings: 
  • Scopus rating (2016): CiteScore 2.64 SJR 1.751 SNIP 1.604
Original language: English
ASJC Scopus subject areas: Engineering(all), Applied Mathematics, Numerical Analysis
Keywords: Bernoulli problem, Cauchy condition, Differential equations, Elliptic partial differential equations, Equipotential layers, Field lines, Inverse problem, Laplace problem, Mean curvature, Shape design
Source: Scopus
Source ID: 84956739407

Research output: Contribution to journalArticleScientificpeer-review

Graph distance measures based on topological indices revisited

Graph distance measures based on topological indices have been already explored by Dehmer et al. Also, inequalities for those graph distance measures have been proved. In this paper, we continue studying such comparative graph measures based on the well-known Wiener index, graph energy and Randić index, respectively. We prove extremal properties of the graph distance measures for some special classes of graphs. To demonstrate useful properties of the measures, we also discuss numerical results. To conclude the paper we state some open problems.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, BioMediTech, Research Community on Data-to-Decision (D2D), BioMediTech - Institute of Biosciences and Medical Technology, Department of Mechatronics and Biomedical Computer Science, Universität der Bundeswehr München, UMIT, Center for Combinatorics and LPMC-TJKLC, Eduard Wallnoefer Zentrum 1, Nankai University
Contributors: Dehmer, M., Emmert-Streib, F., Shi, Y.
Number of pages: 11
Pages: 623-633
Publication date: 18 Jun 2015
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 266
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2015): CiteScore 1.7 SJR 0.95 SNIP 1.239
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics
Keywords: Distance measure, Edit distance, Extremal graph, Topological index
Source: Scopus
Source ID: 84935922526

Research output: Contribution to journalArticleScientificpeer-review

Graph entropy based on the number of spanning forests of c-cyclic graphs

Graph entropies have been introduced to quantitatively measure the structural information content of graphs and networks; they have plenty of applications in various fields. Utilizing the number of subgraphs to establish measures for determining the complexity of molecular graphs are also prevalent in the study of mathematical chemistry. In this paper, we develop a new graph entropy measure that is based on the number of spanning forests. We prove explicit expressions for the entropy for trees, unicyclic and bicyclic graphs, and show that the cycle graph Cn attains the maximal value of the entropy for unicyclic graphs with order n and large cycle lengths. Based on generating numerical results, we conjecture extremal unicyclic graphs with respect to the entropy as well as we compare the values of our entropy for c-cyclic graphs, and generate graphs of bicyclic graphs and tricyclic graphs with 6 vertices for performing further research.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computing Sciences, Research group: Predictive Society and Data Analytics (PSDA), Northwestern Polytechnical University, Yulin University, Beijing University of Chemical Technology, University of Applied Sciences Upper Austria, School of Management, Nankai University, Hall in Tyrol, Mathematics Faculty of Information Technology and Communication Sciences
Contributors: Wan, P., Tu, J., Dehmer, M., Zhang, S., Emmert-Streib, F.
Publication date: 15 Dec 2019
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 363
Article number: 124616
ISSN (Print): 0096-3003
Original language: English
ASJC Scopus subject areas: Computational Mathematics, Applied Mathematics
Keywords: Graph entropy, Spanning forest, Subgraph
Source: Scopus
Source ID: 85073703315

Research output: Contribution to journalArticleScientificpeer-review

GSAR: Bioconductor package for Gene Set analysis in R

Background: Gene set analysis (in a form of functionally related genes or pathways) has become the method of choice for analyzing omics data in general and gene expression data in particular. There are many statistical methods that either summarize gene-level statistics for a gene set or apply a multivariate statistic that accounts for intergene correlations. Most available methods detect complex departures from the null hypothesis but lack the ability to identify the specific alternative hypothesis that rejects the null. Results: GSAR (Gene Set Analysis in R) is an open-source R/Bioconductor software package for gene set analysis (GSA). It implements self-contained multivariate non-parametric statistical methods testing a complex null hypothesis against specific alternatives, such as differences in mean (shift), variance (scale), or net correlation structure. The package also provides a graphical visualization tool, based on the union of two minimum spanning trees, for correlation networks to examine the change in the correlation structures of a gene set between two conditions and highlight influential genes (hubs). Conclusions: Package GSAR provides a set of multivariate non-parametric statistical methods that test a complex null hypothesis against specific alternatives. The methods in package GSAR are applicable to any type of omics data that can be represented in a matrix format. The package, with detailed instructions and examples, is freely available under the GPL (> = 2) license from the Bioconductor web site.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Faculty of Biomedical Sciences and Engineering, Research group: Predictive Society and Data Analytics (PSDA), University of Arkansas for Medical Sciences, Computational Medicine and Statistical Learning Laboratory
Contributors: Rahmatallah, Y., Zybailov, B., Emmert-Streib, F., Glazko, G.
Publication date: 24 Jan 2017
Peer-reviewed: Yes

Publication information

Journal: BMC Bioinformatics
Volume: 18
Issue number: 1
Article number: 61
ISSN (Print): 1471-2105
Ratings: 
  • Scopus rating (2017): CiteScore 2.49 SJR 1.479 SNIP 0.896
Original language: English
ASJC Scopus subject areas: Structural Biology, Biochemistry, Molecular Biology, Computer Science Applications, Applied Mathematics
Keywords: Gene set analysis, Kolmogorov-Smirnov, Minimum spanning tree, Non-parametric, Pathways, Wald Wolfowitz
Source: Scopus
Source ID: 85010460642

Research output: Contribution to journalArticleScientificpeer-review

Harnessing the complexity of gene expression data from cancer: From single gene to structural pathway methods

: High-dimensional gene expression data provide a rich source of information because they capture the expression level of genes in dynamic states that reflect the biological functioning of a cell. For this reason, such data are suitable to reveal systems related properties inside a cell, e.g., in order to elucidate molecular mechanisms of complex diseases like breast or prostate cancer. However, this is not only strongly dependent on the sample size and the correlation structure of a data set, but also on the statistical hypotheses tested. Many different approaches have been developed over the years to analyze gene expression data to (I) identify changes in single genes, (II) identify changes in gene sets or pathways, and (III) identify changes in the correlation structure in pathways. In this paper, we review statistical methods for all three types of approaches, including subtypes, in the context of cancer data and provide links to software implementations and tools and address also the general problem of multiple hypotheses testing. Further, we provide recommendations for the selection of such analysis methods.Reviewers: This article was reviewed by Arcady Mushegian, Byung-Soo Kim and Joel Bader.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Prostate cancer research center (PCRC), Computational Biology and Machine Learning, Queen's University, Belfast, Northern Ireland
Contributors: Emmert-Streib, F., Tripathi, S., Matos Simoes, R. D.
Publication date: 10 Dec 2012
Peer-reviewed: Yes

Publication information

Journal: Biology Direct
Volume: 7
Article number: 44
ISSN (Print): 1745-6150
Ratings: 
  • Scopus rating (2012): CiteScore 3.15 SJR 2.148 SNIP 0.745
Original language: English
ASJC Scopus subject areas: Agricultural and Biological Sciences(all), Biochemistry, Genetics and Molecular Biology(all), Immunology, Applied Mathematics, Modelling and Simulation, Ecology, Evolution, Behavior and Systematics
Keywords: Cancer data, Cancer genomics, Correlation structure, Gene expression data, Pathway methods, Statistical analysis methods
Source: Scopus
Source ID: 84872650417

Research output: Contribution to journalArticleScientificpeer-review

Hierarchical coordination of periodic genes in the cell cycle of Saccharomyces cerevisiae

Background: Gene networks are a representation of molecular interactions among genes or products thereof and, hence, are forming causal networks. Despite intense studies during the last years most investigations focus so far on inferential methods to reconstruct gene networks from experimental data or on their structural properties, e.g., degree distributions. Their structural analysis to gain functional insights into organizational principles of, e.g., pathways remains so far under appreciated. Results: In the present paper we analyze cell cycle regulated genes in S. cerevisiae. Our analysis is based on the transcriptional regulatory network, representing causal interactions and not just associations or correlations between genes, and a list of known periodic genes. No further data are used. Partitioning the transcriptional regulatory network according to a graph theoretical property leads to a hierarchy in the network and, hence, in the information flow allowing to identify two groups of periodic genes. This reveals a novel conceptual interpretation of the working mechanism of the cell cycle and the genes regulated by this pathway. Conclusion: Aside from the obtained results for the cell cycle of yeast our approach could be exemplary for the analysis of general pathways by exploiting the rich causal structure of inferred and/or curated gene networks including protein or signaling networks.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computational Biology and Machine Learning Lab., Faculty of Medicine, Health and Life Sciences, Queen's University, Belfast, Northern Ireland, Institute for Bioinformatics and Translational Research
Contributors: Emmert-Streib, F., Dehmer, M.
Publication date: 20 Jul 2009
Peer-reviewed: Yes

Publication information

Journal: BMC Systems Biology
Volume: 3
Article number: 76
ISSN (Print): 1752-0509
Ratings: 
  • Scopus rating (2009): SJR 1.493 SNIP 0.974
Original language: English
ASJC Scopus subject areas: Molecular Biology, Structural Biology, Applied Mathematics, Modelling and Simulation, Computer Science Applications
Source: Scopus
Source ID: 68949220295

Research output: Contribution to journalArticleScientificpeer-review

Homogeneous (α,k)-Polynomial Solutions of the Fractional Riesz System in Hyperbolic Space

In this paper we study the fractional analogous of the Laplace–Beltrami equation and the hyperbolic Riesz system studied previously by H. Leutwiler, in (Formula presented.). In both cases we replace the integer derivatives by Caputo fractional derivatives of order (Formula presented.). We characterize the space of solutions of the fractional Laplace–Beltrami equation, and we calculate its dimension. We establish relations between the solutions of the fractional Laplace–Beltrami equation and the solutions of the hyperbolic fractional Riesz system. Some examples of the polynomial solutions will be presented. Moreover, the behaviour of the obtained results when (Formula presented.) is presented, and a final remark about the consideration of Riemann–Liouville fractional derivatives instead of Caputo fractional derivatives is made.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, Universidade de Aveiro
Contributors: Orelma, H., Vieira, N.
Number of pages: 15
Pages: 1253–1267
Publication date: 2017
Peer-reviewed: Yes
Early online date: 1 Apr 2017

Publication information

Journal: Complex Analysis and Operator Theory
Volume: 11
Issue number: 5
ISSN (Print): 1661-8254
Ratings: 
  • Scopus rating (2017): CiteScore 0.72 SJR 0.663 SNIP 1.063
Original language: English
ASJC Scopus subject areas: Computational Theory and Mathematics, Computational Mathematics, Applied Mathematics
Keywords: Caputo fractional derivative, Hyperbolic, Hyperbolic fractional Riesz system, Hypermonogenic functions, Laplace–Beltrami fractional differential operator
Source: Scopus
Source ID: 85016641794

Research output: Contribution to journalArticleScientificpeer-review

Hyperbolic Function Theory in the Skew-Field of Quaternions

We are studying hyperbolic function theory in the total skew-field of quaternions. Earlier the theory has been studied for quaternion valued functions depending only on three reduced variables. Our functions are depending on all four coordinates of quaternions. We consider functions, called α-hyperbolic harmonic, that are harmonic with respect to the Riemannian metric dsα2=dx02+dx12+dx22+dx32x3αin the upper half space R+4={(x0,x1,x2,x3)∈R4:x3>0}. If α= 2 , the metric is the hyperbolic metric of the Poincaré upper half-space. Hempfling and Leutwiler started to study this case and noticed that the quaternionic power function xm(m∈Z), is a conjugate gradient of a 2-hyperbolic harmonic function. They researched polynomial solutions. Using fundamental α-hyperbolic harmonic functions, depending only on the hyperbolic distance and x3, we verify a Cauchy type integral formula for conjugate gradient of α-hyperbolic harmonic functions. We also compare these results with the properties of paravector valued α-hypermonogenic in the Clifford algebra Cℓ0,3.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computing Sciences, Department of Mathematics and Statistics, Helsinki University
Contributors: Eriksson, S., Orelma, H.
Publication date: 1 Nov 2019
Peer-reviewed: Yes

Publication information

Journal: Advances in Applied Clifford Algebras
Volume: 29
Issue number: 5
Article number: 97
ISSN (Print): 0188-7009
Original language: English
ASJC Scopus subject areas: Applied Mathematics
Keywords: Clifford algebra, Hyperbolic Laplace operator, Hyperbolic metric, Laplace–Beltrami operator, Monogenic function, Quaternions, α-hyperbolic harmonic, α-hypermonogenic

Bibliographical note

EXT="Eriksson, Sirkka-Liisa"

Source: Scopus
Source ID: 85073523419

Research output: Contribution to journalArticleScientificpeer-review

Hypermonogenic Functions of Two Vector Variables

In this paper we introduce the modified Dirac operators (Formula presented.) and (Formula presented.), where (Formula presented.) is differentiable function, and (Formula presented.) is the Clifford algebra generated by the basis vectors of (Formula presented.). We look for solutions (Formula presented.) of the system (Formula presented.), where the first and third variables are invariant under rotations. These functions are called (Formula presented.)-hypermonogenic functions. We discuss about axially symmetric functions with respect to the symmetric group (Formula presented.). Some examples of axially symmetric (Formula presented.)-hypermonogenic functions generated by homogeneous functions and hypergeometric functions are presented.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Civil Engineering, University of Helsinki, Laboratory of Civil Engineering, Universidade de Aveiro
Contributors: Eriksson, S. L., Orelma, H., Vieira, N.
Number of pages: 16
Pages: 555–570
Publication date: 2018
Peer-reviewed: Yes
Early online date: 26 Sep 2017

Publication information

Journal: Complex Analysis and Operator Theory
Volume: 12
Issue number: 2
ISSN (Print): 1661-8254
Ratings: 
  • Scopus rating (2018): CiteScore 0.72 SJR 0.459 SNIP 0.889
Original language: English
ASJC Scopus subject areas: Computational Theory and Mathematics, Computational Mathematics, Applied Mathematics
Keywords: Axially symmetric functions, Hypermonogenic functions, Modified Dirac operator, Several vector variables

Bibliographical note

EXT="Eriksson, S. L."

Source: Scopus
Source ID: 85029901048

Research output: Contribution to journalArticleScientificpeer-review

Hypermonogenic Plane Wave Solutions of the Dirac Equation in Superspace

In this paper, we obtain Cauchy–Kovalevskaya theorems for hypermonogenic superfunctions depending only on purely bosonic and fermionic vector variables. In addition, we use these results to construct plane wave examples of such functions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Civil Engineering, Universiteit Gent
Contributors: Adán, A. G., Orelma, H., Sommen, F.
Publication date: 1 Sep 2019
Peer-reviewed: Yes

Publication information

Journal: Advances in Applied Clifford Algebras
Volume: 29
Issue number: 4
Article number: 71
ISSN (Print): 0188-7009
Original language: English
ASJC Scopus subject areas: Applied Mathematics
Keywords: Cauchy–Kovalevskaya extension, Clifford analysis, Hypermonogenic functions, Plane waves, Superspace
Source: Scopus
Source ID: 85069655339

Research output: Contribution to journalArticleScientificpeer-review

Hypermonogenic solutions and plane waves of the Dirac operator in Rp×Rq

In this paper we first define hypermonogenic solutions of the Dirac operator in Rp×Rq and study some basic properties, e.g., obtaining a Cauchy integral formula in the unit hemisphere. Hypermonogenic solutions form a natural function class in classical Clifford analysis. After that, we define the corresponding hypermonogenic plane wave solutions and deduce explicit methods to compute these functions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Civil Engineering, Universiteit Gent
Contributors: Guzmán Adán, A., Orelma, H., Sommen, F.
Number of pages: 14
Pages: 1-14
Publication date: 1 Apr 2019
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: Applied Mathematics and Computation
Volume: 346
ISSN (Print): 0096-3003
Original language: English
ASJC Scopus subject areas: Computational Mathematics, Applied Mathematics
Keywords: Cauchy's formula, Hypermonogenic solution, Plane wave
Source: Scopus
Source ID: 85055664097

Research output: Contribution to journalArticleScientificpeer-review

Improving reliability for classification of metallic objects using a WTMD portal

In this paper, a walk-through metal detection (WTMD) portal is used for classification of metallic objects. The classification is based on the inversion of the magnetic polarisability tensor (tensor) of the object. The nature of bias and noise components in the tensor are examined by using real walk-through data, and consequently, a novel classifier is introduced. Furthermore, a novel method for detecting poorly inverted tensors is presented, enabling self-diagnostics for the WTMD portal. Based on the results, the novel methods increase the accuracy of metal object classification and have the potential to improve the reliability of a WTMD system.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Research group: MMDM, Signal Processing Research Community (SPRC), School of Electrical and Electronic Engineering, University of Manchester, Rapiscan Systems Oy
Contributors: Makkonen, J., Marsh, L. A., Vihonen, J., Järvi, A., Armitage, D. W., Visa, A., Peyton, A. J.
Publication date: 26 Aug 2015
Peer-reviewed: Yes

Publication information

Journal: Measurement Science and Technology
Volume: 26
Issue number: 10
Article number: 105103
ISSN (Print): 0957-0233
Ratings: 
  • Scopus rating (2015): CiteScore 1.71 SJR 0.704 SNIP 1.396
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Instrumentation
Keywords: bias, classification, eigenvalues, electromagnetic polarisability, noise, tensor, WTMD
Source: Scopus
Source ID: 84941975778

Research output: Contribution to journalArticleScientificpeer-review

Indirect NOx emission monitoring in natural gas fired boilers

New emission regulations will increase the need for inexpensive NOx emission monitoring solutions also in smaller power plants. The objective in this study is to find easily maintainable and transparent but still valid models to predict NOx emissions in natural gas fired hot water boilers utilizing existing process instrumentation. With a focus on long-term applicability in practical installations, the performance of linear regression is compared in two municipal 43 MW boilers with three widely used nonlinear methods: multilayer perceptron, support vector regression, and fuzzy inference system. The linear models were the most applicable providing the best estimation results (relative error of 1 applications in practise. However, each boiler model should be identified individually.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Automation and Hydraulic Engineering, Research area: Measurement Technology and Process Control, Helen Ltd.
Contributors: Korpela, T., Kumpulainen, P., Majanne, Y., Häyrinen, A., Lautala, P.
Number of pages: 15
Pages: 11-25
Publication date: 1 Aug 2017
Peer-reviewed: Yes

Publication information

Journal: Control Engineering Practice
Volume: 65
ISSN (Print): 0967-0661
Ratings: 
  • Scopus rating (2017): CiteScore 3.42 SJR 1.069 SNIP 1.905
Original language: English
ASJC Scopus subject areas: Control and Systems Engineering, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Combustion, Estimation, Modelling, Monitoring, Natural gas, NO, Soft sensor
Electronic versions: 
URLs: 
Source: Scopus
Source ID: 85019718306

Research output: Contribution to journalArticleScientificpeer-review

Inferring the conservative causal core of gene regulatory networks

Background: Inferring gene regulatory networks from large-scale expression data is an important problem that received much attention in recent years. These networks have the potential to gain insights into causal molecular interactions of biological processes. Hence, from a methodological point of view, reliable estimation methods based on observational data are needed to approach this problem practically.Results: In this paper, we introduce a novel gene regulatory network inference (GRNI) algorithm, called C3NET. We compare C3NET with four well known methods, ARACNE, CLR, MRNET and RN, conducting in-depth numerical ensemble simulations and demonstrate also for biological expression data from E. coli that C3NET performs consistently better than the best known GRNI methods in the literature. In addition, it has also a low computational complexity. Since C3NET is based on estimates of mutual information values in conjunction with a maximization step, our numerical investigations demonstrate that our inference algorithm exploits causal structural information in the data efficiently.Conclusions: For systems biology to succeed in the long run, it is of crucial importance to establish methods that extract large-scale gene networks from high-throughput data that reflect the underlying causal interactions among genes or gene products. Our method can contribute to this endeavor by demonstrating that an inference algorithm with a neat design permits not only a more intuitive and possibly biological interpretation of its working mechanism but can also result in superior results.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Queen's University, Belfast, Northern Ireland, Computational Biology and Machine Learning Lab., Faculty of Medicine, Health and Life Sciences
Contributors: Altay, G., Emmert-Streib, F.
Publication date: 28 Sep 2010
Peer-reviewed: Yes

Publication information

Journal: BMC Systems Biology
Volume: 4
Article number: 132
ISSN (Print): 1752-0509
Ratings: 
  • Scopus rating (2010): SJR 1.832 SNIP 1.057
Original language: English
ASJC Scopus subject areas: Molecular Biology, Structural Biology, Applied Mathematics, Modelling and Simulation, Computer Science Applications
Source: Scopus
Source ID: 77957141016

Research output: Contribution to journalArticleScientificpeer-review

Information processing in the transcriptional regulatory network of yeast: Functional robustness

Background: Gene networks are considered to represent various aspects of molecular biological systems meaningfully because they naturally provide a systems perspective of molecular interactions. In this respect, the functional understanding of the transcriptional regulatory network is considered as key to elucidate the functional organization of an organism. Results: In this paper we study the functional robustness of the transcriptional regulatory network of S. cerevisiae. We model the information processing in the network as a first order Markov chain and study the influence of single gene perturbations on the global, asymptotic communication among genes. Modification in the communication is measured by an information theoretic measure allowing to predict genes that are 'fragile' with respect to single gene knockouts. Our results demonstrate that the predicted set of fragile genes contains a statistically significant enrichment of so called essential genes that are experimentally found to be necessary to ensure vital yeast. Further, a structural analysis of the transcriptional regulatory network reveals that there are significant differences between fragile genes, hub genes and genes with a high betweenness centrality value. Conclusion: Our study does not only demonstrate that a combination of graph theoretical, information theoretical and statistical methods leads to meaningful biological results but also that such methods allow to study information processing in gene networks instead of just their structural properties.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computational Biology and Machine Learning, Queen's University, Belfast, Northern Ireland, Center for Mathematics Probability and Statistics
Contributors: Emmert-Streib, F., Dehmer, M.
Publication date: 19 Mar 2009
Peer-reviewed: Yes

Publication information

Journal: BMC Systems Biology
Volume: 3
Article number: 35
ISSN (Print): 1752-0509
Ratings: 
  • Scopus rating (2009): SJR 1.493 SNIP 0.974
Original language: English
ASJC Scopus subject areas: Molecular Biology, Structural Biology, Applied Mathematics, Modelling and Simulation, Computer Science Applications
Source: Scopus
Source ID: 65649087188

Research output: Contribution to journalArticleScientificpeer-review

Information theoretic measures of UHG graphs with low computational complexity

We introduce a novel graph class we call universal hierarchical graphs (UHG) whose topology can be found numerously in problems representing, e.g., temporal, spacial or general process structures of systems. For this graph class we show, that we can naturally assign two probability distributions, for nodes and for edges, which lead us directly to the definition of the entropy and joint entropy and, hence, mutual information establishing an information theory for this graph class. Furthermore, we provide some results under which conditions these constraint probability distributions maximize the corresponding entropy. Also, we demonstrate that these entropic measures can be computed efficiently which is a prerequisite for every large scale practical application and show some numerical examples.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Stowers Institute for Medical Research, University of Veterinary Medicine Vienna
Contributors: Emmert-Streib, F., Dehmer, M.
Number of pages: 12
Pages: 1783-1794
Publication date: 15 Jul 2007
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 190
Issue number: 2
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2007): SJR 0.869 SNIP 1.113
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics, Numerical Analysis
Keywords: Entropy, Graph classes, Graph measures, Hierarchical graphs, Information theory
Source: Scopus
Source ID: 34250623666

Research output: Contribution to journalArticleScientificpeer-review

Integral kernels for k-hypermonogenic functions

We consider the modified Cauchy–Riemann operator (Formula presented.) in the universal Clifford algebra (Formula presented.) with the basis (Formula presented.). The null-solutions of this operator are called k-hypermonogenic functions. We calculate the k-hyperbolic harmonic fundamental solutions, i.e. solutions to (Formula presented.), and use these solutions to find k-hypermonogenic kernels for a Cauchy-type integral formula in the upper half-space.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, University of Helsinki
Contributors: Vuojamo, V., Eriksson, S.
Number of pages: 12
Pages: 1-12
Publication date: 2017
Peer-reviewed: Yes
Early online date: 21 Feb 2017

Publication information

Journal: Complex Variables and Elliptic Equations
Volume: 62
Issue number: 9
ISSN (Print): 1747-6933
Ratings: 
  • Scopus rating (2017): CiteScore 0.73 SJR 0.616 SNIP 0.989
Original language: English
ASJC Scopus subject areas: Analysis, Numerical Analysis, Computational Mathematics, Applied Mathematics
Keywords: Cauchy integral formula, Clifford algebra, hyperbolic Laplace–Beltrami, k-hyperbolic harmonic, k-hypermonogenic

Bibliographical note

EXT="Eriksson, Sirkka-Liisa"

Source: Scopus
Source ID: 85013192611

Research output: Contribution to journalArticleScientificpeer-review

Interference and SINR in Millimeter Wave and Terahertz Communication Systems With Blocking and Directional Antennas

The fifth generation wireless systems are expected to rely on a large number of small cells to massively offload traffic from the cellular and even from the wireless local area networks. To enable this functionality, mm-wave (EHF) and Terahertz (THF) bands are being actively explored. These bands are characterized by unique propagation properties compared with microwave systems. As a result, the interference structure in these systems could be principally different to what we observed so far at lower frequencies. In this paper, using the tools of stochastic geometry, we study the systems operating in the EHF/THF bands by explicitly capturing three phenomena inherent for these frequencies: 1) high directivity of the transmit and receive antennas; 2) molecular absorption; and 3) blocking of high-frequency radiation. We also define and compare two different antenna radiation pattern models. The metrics of interest are the mean interference and the signal-to-interference-plus-noise (SINR) ratio at the receiver. Our results reveal that: 1) for the same total emitted energy by a Poisson field of interferers, both the interference and SINR significantly increase when simultaneously both transmit and receive antennas are directive and 2) blocking has a profound impact on the interference and SINR creating much more favorable conditions for communications compared with no blocking case.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Emerging Technologies for Nano-Bio-Info-Cogno, State University of New York
Contributors: Petrov, V., Komarov, M., Moltchanov, D., Jornet, J. M., Koucheryavy, Y.
Number of pages: 18
Pages: 1791-1808
Publication date: 1 Mar 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Wireless Communications
Volume: 16
Issue number: 3
ISSN (Print): 1536-1276
Ratings: 
  • Scopus rating (2017): CiteScore 6.43 SJR 1.246 SNIP 2.451
Original language: English
ASJC Scopus subject areas: Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: 5G systems, blocking, directional antennas, Interference, millimeter waves, terahertz band
Source: Scopus
Source ID: 85015301037

Research output: Contribution to journalArticleScientificpeer-review

Iterative unsupervised domain adaptation for generalized cell detection from brightfield z-stacks

Background: Cell counting from cell cultures is required in multiple biological and biomedical research applications. Especially, accurate brightfield-based cell counting methods are needed for cell growth analysis. With deep learning, cells can be detected with high accuracy, but manually annotated training data is required. We propose a method for cell detection that requires annotated training data for one cell line only, and generalizes to other, unseen cell lines. Results: Training a deep learning model with one cell line only can provide accurate detections for similar unseen cell lines (domains). However, if the new domain is very dissimilar from training domain, high precision but lower recall is achieved. Generalization capabilities of the model can be improved with training data transformations, but only to a certain degree. To further improve the detection accuracy of unseen domains, we propose iterative unsupervised domain adaptation method. Predictions of unseen cell lines with high precision enable automatic generation of training data, which is used to train the model together with parts of the previously used annotated training data. We used U-Net-based model, and three consecutive focal planes from brightfield image z-stacks. We trained the model initially with PC-3 cell line, and used LNCaP, BT-474 and 22Rv1 cell lines as target domains for domain adaptation. Highest improvement in accuracy was achieved for 22Rv1 cells. F 1 -score after supervised training was only 0.65, but after unsupervised domain adaptation we achieved a score of 0.84. Mean accuracy for target domains was 0.87, with mean improvement of 16 percent. Conclusions: With our method for generalized cell detection, we can train a model that accurately detects different cell lines from brightfield images. A new cell line can be introduced to the model without a single manual annotation, and after iterative domain adaptation the model is ready to detect these cells with high accuracy.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: BioMediTech, Tampere University of Applied Sciences, University of Eastern Finland
Contributors: Liimatainen, K., Kananen, L., Latonen, L., Ruusuvuori, P.
Publication date: 15 Feb 2019
Peer-reviewed: Yes

Publication information

Journal: BMC Bioinformatics
Volume: 20
Issue number: 1
Article number: 80
ISSN (Print): 1471-2105
Original language: English
ASJC Scopus subject areas: Structural Biology, Biochemistry, Molecular Biology, Computer Science Applications, Applied Mathematics
Keywords: Brightfield, Cell detection, Deep learning, Semi-supervised learning, Unsupervised domain adaptation
Electronic versions: 

Bibliographical note

DUPL=47150514

Source: Scopus
Source ID: 85061610929

Research output: Contribution to journalArticleScientificpeer-review

Magnetomechanical coupled FE simulations of rotating electrical machines

Purpose - The purpose is to implement and compare different approaches for modelling the magnetostriction phenomenon in iron sheet used in rotating electrical machines. Design/methodology/approach - In the force-based approach, the magnetostriction is modelled as a set of equivalent forces, which produce the same deformation of the material as the magnetostriction strains. These forces among other magnetic forces are computed from the solution of the finite element (FE) field computation and used as loads for the displacement-based mechanical FE analysis. In the strain-based approach, the equivalent magnetostrictive forces are not needed and an energy-based model is used to define magnetomechanically coupled constitutive equations of the material. These equations are then space-discretised and solved with the FE method for the magnetic field and the displacements. Findings - It is found that the equivalent forces method can reproduce the displacements and strains of the structure but it results in erroneous stress states. The energy-based method has the ability to reproduce both the stress and strains correctly; thus enabling the analysis of stress-dependent quantities such as the iron losses and the magnetostriction itself. Research limitations/implications - The investigated methods do not account for hysteresis and other dynamic effects. They also require long computation times. With the available computing resources, the computation time does not present any problem as far as they are not used in everyday design procedures but the modelling of dynamic effect needs to be elaborated. Originality/value - The developed and implemented methods are verified with measurements and simulation experiments and applied to as complex structure as an electrical machine. The problems related to the different approaches are investigated and explained through simulations. © Emerald Group Publishing Limited.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Mechanical Engineering and Industrial Systems, Life Cycle Effectiveness of the Built Environment (LCE@BE), Smart Energy Systems (SES), Aalto University
Contributors: Belahcen, A., Fonteyn, K., Kouhia, R., Rasilo, P., Arkkio, A.
Number of pages: 16
Pages: 1484-1499
Publication date: 2013
Peer-reviewed: Yes

Publication information

Journal: COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering
Volume: 32
Issue number: 5
Article number: 17095978
ISSN (Print): 0332-1649
Ratings: 
  • Scopus rating (2013): CiteScore 0.55 SJR 0.215 SNIP 0.6
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Computational Theory and Mathematics, Applied Mathematics
Keywords: Coupled systems, Electrical equipment, Finite element simulation, Iron, Iron losses, Magnetoelasticity, Stress, Stress analysis

Bibliographical note

Contribution: organisation=ede,FACT1=1<br/>Portfolio EDEND: 2013-10-29<br/>Publisher name: Emerald Group Publishing

Source: researchoutputwizard
Source ID: 1975

Research output: Contribution to journalArticleScientificpeer-review

Meeting a deadline: shortest paths on stochastic directed acyclic graphs with information gathering

We consider the problem of an agent traversing a directed graph with the objective of maximizing the probability of reaching a goal node before a given deadline. Only the probability of the travel times of edges is known to the agent. The agent must balance between traversal actions towards the goal, and delays due to actions improving information about graph edge travel times. We describe the relationship of the problem to the more general partially observable Markov decision process. Further, we show that if edge travel times are independent and the underlying directed graph is acyclic, a closed loop solution can be computed. The solution specifies whether to execute a traversal or information-gathering action as a function of the current node, the time remaining until the deadline, and the information about edge travel times. We present results from two case studies, quantifying the usefulness of information-gathering as opposed to applying only traversal actions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Automation Science and Engineering
Contributors: Lauri, M., Ropponen, A., Ritala, R.
Number of pages: 34
Pages: 337–370
Publication date: Apr 2017
Peer-reviewed: Yes
Early online date: 28 Sep 2016

Publication information

Journal: Annals of Mathematics and Artificial Intelligence
Volume: 79
Issue number: 4
ISSN (Print): 1012-2443
Ratings: 
  • Scopus rating (2017): CiteScore 1.21 SJR 0.413 SNIP 1.036
Original language: English
ASJC Scopus subject areas: Artificial Intelligence, Applied Mathematics
Keywords: Applied probability, Decision processes, Dynamic programming, Markov processes, Transportation
Source: Scopus
Source ID: 84988712384

Research output: Contribution to journalArticleScientificpeer-review

Modeling carbon dioxide transport in PDMS-based microfluidic cell culture devices

Maintaining a proper pH level is crucial for successful cell culturing. Mammalian cells are commonly cultured in incubators, where the cell culture medium is saturated with a mixture of air and 5% carbon dioxide (CO<inf>2</inf>). Therefore, to keep cell culture medium pH in an acceptable level outside these incubators, a suitable CO<inf>2</inf> concentration must be dissolved in the medium. However, it can be very difficult to control and measure precisely local concentration levels. Furthermore, possible undesired concentration gradients generated during long-term cell culturing are almost impossible to detect. Therefore, we have developed a computational model to estimate CO<inf>2</inf> transport in silicone-based microfluidic devices. An extensive set of experiments was used to validate the finite element model. The model parameters were obtained using suitable measurement set-ups and the model was validated using a fully functional cell cultivation device. The predictions obtained by the simulations show very good responses to experiments. It is shown in this paper how the model helps to understand the dynamics of CO<inf>2</inf> transport in silicone-based cell culturing devices possessing different geometries, thus providing cost-effective means for studying different device designs under a variety of experimental conditions without the need of actual testing. Finally, based on the results from the computational model, an alternative strategy for feeding CO<inf>2</inf> is proposed to accelerate the system performance such that a faster and more uniform CO<inf>2</inf> concentration response is achieved in the area of interest.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Automation Science and Engineering, Department of Materials Science, Research group: Paper Converting and Packaging, BioMediTech, Integrated Technologies for Tissue Engineering Research (ITTE), BioMediTech
Contributors: Mäki, A. J., Peltokangas, M., Kreutzer, J., Auvinen, S., Kallio, P.
Number of pages: 10
Pages: 515-524
Publication date: 1 Dec 2015
Peer-reviewed: Yes

Publication information

Journal: Chemical Engineering Science
Volume: 137
ISSN (Print): 0009-2509
Ratings: 
  • Scopus rating (2015): CiteScore 2.96 SJR 1.022 SNIP 1.55
Original language: English
ASJC Scopus subject areas: Chemical Engineering(all), Chemistry(all), Applied Mathematics, Industrial and Manufacturing Engineering
Keywords: Carbon dioxide, Finite element method, Mass transport, Microfluidics cell culturing, Numerical simulation, pH
Electronic versions: 
URLs: 

Bibliographical note

ORG=ase,0.9
ORG=mol,0.1

Source: Scopus
Source ID: 84938149959

Research output: Contribution to journalArticleScientificpeer-review

Modeling probability densities with sums of exponentials via polynomial approximation

Abstract We propose a method for optimization with semi-infinite constraints that involve a linear combination of functions, focusing on shape-constrained optimization with exponential functions. Each function is lower and upper bounded on sub-intervals by low-degree polynomials. Thus, the constraints can be approximated with polynomial inequalities that can be implemented with linear matrix inequalities. Convexity is preserved, but the problem has now a finite number of constraints. We show how to take advantage of the properties of the exponential function in order to build quickly accurate approximations. The problem used for illustration is the least-squares fitting of a positive sum of exponentials to an empirical probability density function. When the exponents are given, the problem is convex, but we also give a procedure for optimizing the exponents. Several examples show that the method is flexible, accurate and gives better results than other methods for the investigated problems.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Research group: SGN-SPAG, Department of Automatic Control and Computers, University Politehnica of Bucharest, Université de Pau et des Pays de l'Adour
Contributors: Dumitrescu, B., Şicleru, B. C., Avram, F.
Pages: 513–525
Publication date: 2016
Peer-reviewed: Yes
Early online date: 30 Jul 2015

Publication information

Journal: Journal of Computational and Applied Mathematics
Volume: 292
ISSN (Print): 0377-0427
Ratings: 
  • Scopus rating (2016): CiteScore 1.56 SJR 1.087 SNIP 1.291
Original language: English
ASJC Scopus subject areas: Computational Mathematics, Applied Mathematics
Keywords: Density fitting, Optimization, Polynomial approximation, Semi-infinite programming, Sum of exponentials
Source: Scopus
Source ID: 84939247768

Research output: Contribution to journalArticleScientificpeer-review

Modeling Transmit Power Reduction for a Typical Cell with Licensed Shared Access Capabilities

Currently, there is a strong demand to augment capacity of mobile cellular deployments as dictated by advanced bandwidth-hungry applications and services. Network densification and the use of millimeter-wave frequencies develop as the mainstream solutions in fifth-generation (5G) systems, but both suffer from increased complexity and cost. A viable alternative is based on the Licensed Shared Access (LSA) framework that manages spectrum sharing between a limited number of participants. However, interference produced by the current user of the spectrum (the mobile operator) toward its owner (the incumbent) has to be carefully controlled and a number of LSA policies thus emerge. A feasible policy is to reduce the transmit power of the user equipment served by the mobile operator on the LSA bands whenever requested by the incumbent. This work contributes a novel mathematical analysis of the said LSA policy in a challenging scenario that features a highly-dynamic incumbent (the airport), as well as verifies the findings with more detailed system-level simulations. The proposed results constitute a tight estimate on the practical system operation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Rossijskij universitet druzby narodov, Brno University of Technology
Contributors: Mokrov, E., Ponomarenko-Timofeev, A., Gudkova, I., Masek, P., Hosek, J., Andreev, S., Koucheryavy, Y., Gaidamaka, Y.
Pages: 5505-5509
Publication date: Jun 2018
Peer-reviewed: Yes
Early online date: 25 Jan 2018

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 67
Issue number: 6
ISSN (Print): 0018-9545
Ratings: 
  • Scopus rating (2018): CiteScore 6.29 SJR 1.089 SNIP 2.256
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Airplanes, Airports, Atmospheric modeling, Interference, Mobile communication, Telemetry
Source: Scopus
Source ID: 85041344586

Research output: Contribution to journalArticleScientificpeer-review

Multiresolution analysis for compactly supported interpolating tensor product wavelets

We construct multidimensional interpolating tensor product multiresolution analyses (MRA's) of the function spaces C<inf>0</inf>(R<sup>n</sup>,K), K = R or K = C, consisting of real or complex valued functions on R<sup>n</sup> vanishing at infinity and the function spaces Cu(R<sup>n</sup>,K) consisting of bounded and uniformly continuous functions on R<sup>n</sup>. We also construct an interpolating dual MRA for both of these spaces. The theory of the tensor products of Banach spaces is used. We generalize the Besov space norm equivalence from the one-dimensional case to our n-dimensional construction.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Physics
Contributors: Höynälänmaa, T.
Number of pages: 36
Publication date: 6 Mar 2015
Peer-reviewed: Yes

Publication information

Journal: International Journal of Wavelets Multiresolution and Information ProcessIng
Volume: 13
Issue number: 2
Article number: 1550010
ISSN (Print): 0219-6913
Ratings: 
  • Scopus rating (2015): CiteScore 0.52 SJR 0.319 SNIP 0.541
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Information Systems, Signal Processing
Keywords: Besov space, injective tensor norm, Interpolating wavelets, multiresolution analysis, multivariate wavelets, projective tensor norm, tensor Product
Source: Scopus
Source ID: 84928923864

Research output: Contribution to journalArticleScientificpeer-review

Nonlocality-Reinforced Convolutional Neural Networks for Image Denoising

We introduce a paradigm for nonlocal sparsity reinforced deep convolutional neural network denoising. It is a combination of a local multiscale denoising by a convolutional neural network (CNN) based denoiser and a nonlocal denoising based on a nonlocal filter (NLF), exploiting the mutual similarities between groups of patches. CNN models are leveraged with noise levels that progressively decrease at every iteration of our framework, while their output is regularized by a nonlocal prior implicit within the NLF. Unlike complicated neural networks that embed the nonlocality prior within the layers of the network, our framework is modular, and it uses standard pretrained CNNs together with standard nonlocal filters. An instance of the proposed framework, called NN3D, is evaluated over large grayscale image datasets showing state-of-the-art performance.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Signal Processing, Noiseless Imaging Ltd
Contributors: Cruz, C., Foi, A., Katkovnik, V., Egiazarian, K.
Number of pages: 5
Pages: 1216-1220
Publication date: 1 Aug 2018
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 25
Issue number: 8
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2018): CiteScore 4.37 SJR 0.785 SNIP 1.88
Original language: English
ASJC Scopus subject areas: Signal Processing, Electrical and Electronic Engineering, Applied Mathematics
Keywords: BM3D, convolutional neural network, image denoising, nonlocal filters
Source: Scopus
Source ID: 85049097929

Research output: Contribution to journalArticleScientificpeer-review

On derivatives of hypergeometric functions and classical polynomials with respect to parameters

Closed expressions are obtained for derivatives of symbolic order with respect to parameters for the hypergeometric functions, Laguerre, Gegenbauer, Jacobi and some other polynomial.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research group: Wireless Communications and Positioning, Electronics and Communications Engineering, Khalifa University, Russian Academy of Sciences
Contributors: Sofotasios, P. C., Brychkov, Y. A.
Number of pages: 14
Pages: 852-865
Publication date: 2 Nov 2018
Peer-reviewed: Yes

Publication information

Journal: Integral Transforms and Special Functions
Volume: 29
Issue number: 11
ISSN (Print): 1065-2469
Ratings: 
  • Scopus rating (2018): CiteScore 0.92 SJR 0.676 SNIP 0.989
Original language: English
ASJC Scopus subject areas: Analysis, Applied Mathematics
Keywords: 33C20, 33C45, Bessel polynomial, C33, Charlier polynomial, continuous Hahn polynomial, differentiation, Gegenbauer polynomial, Hahn polynomial, hypergeometric functions, Jacobi polynomial, Krawtchouk polynomial, Laguerre polynomial, Legendre function, Meixner polynomial, Special functions
Source: Scopus
Source ID: 85053369865

Research output: Contribution to journalArticleScientificpeer-review

On efficient network similarity measures

This paper presents novel graph similarity measures which can be applied to simple directed and undirected networks. To define the graph similarity measures, we first map graphs to real numbers by utilizing structural graph measures. Then, we define measures of similarity between real numbers and prove that they can be used as proxies for graph similarity. Numerical results are derived to show the domain coverage of these measures as well as their clustering ability. The latter relates to the efficient grouping of graphs according to certain structural properties. Our numerical results are sensitive to these properties and offer insights useful for designing effective graph similarity measures.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computing Sciences, Research group: Computational Medicine and Statistical Learning Laboratory (CMSL), Research group: Predictive Society and Data Analytics (PSDA), University of Applied Sciences Upper Austria, Nankai University, Hall in Tyrol, Shandong University at Weihai, Steyr School of Management, Shahid Rajaee Teacher Training University, The City College of New York (CUNY), Predictive Society and Data Analytics Lab, Institute of Biosciences and Medical Technology
Contributors: Dehmer, M., Chen, Z., Shi, Y., Zhang, Y., Tripathi, S., Ghorbani, M., Mowshowitz, A., Emmert-Streib, F.
Publication date: 1 Dec 2019
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 362
Article number: 124521
ISSN (Print): 0096-3003
Original language: English
ASJC Scopus subject areas: Computational Mathematics, Applied Mathematics
Keywords: Distance measures, Graphs, Inequalities, Networks, Similarity measures
Source: Scopus
Source ID: 85068221101

Research output: Contribution to journalArticleScientificpeer-review

On k-Hypermonogenic Functions and Their Mean Value Properties

We study a hyperbolic version of holomorphic functions to higher dimensions. In this frame work, a generalization of holomorphic functions are called (Formula presented.)-hypermonogenic functions. These functions are depending on several real variables and their values are in a Clifford algebra. They are defined in terms of hyperbolic Dirac operators. They are connected to harmonic functions with respect to the Riemannian metric (Formula presented.) in the same way as the usual harmonic function to holomorphic functions. We present the mean value property for (Formula presented.)-hypermonogenic functions and related results. Earlier the mean value properties has been proved for hypermonogenic functions. The key tools are the invariance properties of the hyperbolic metric.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Mathematics, Research group: MAT Clifford analysis
Contributors: Eriksson, S., Orelma, H.
Number of pages: 15
Pages: 311-325
Publication date: 2016
Peer-reviewed: Yes
Early online date: 8 Mar 2015

Publication information

Journal: Complex Analysis and Operator Theory
Volume: 10
Issue number: 2
ISSN (Print): 1661-8254
Ratings: 
  • Scopus rating (2016): CiteScore 0.57 SJR 0.554 SNIP 0.776
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics, Computational Theory and Mathematics
Keywords: Dirac operator, Hyperbolic metric, Hypermonogenic, Monogenic
Source: Scopus
Source ID: 84955725749

Research output: Contribution to journalArticleScientificpeer-review

Online Spectrogram Inversion for Low-Latency Audio Source Separation

Audio source separation is usually achieved by estimating the short-time Fourier transform (STFT) magnitude of each source, and then applying a spectrogram inversion algorithm to retrieve time-domain signals. In particular, the multiple input spectrogram inversion (MISI) algorithm has been exploited successfully in several recent works. However, this algorithm suffers from two drawbacks, which we address in this letter. First, it has originally been introduced in a heuristic fashion: we propose here a rigorous optimization framework in which MISI is derived, thus proving the convergence of this algorithm. Besides, while MISI operates offline, we propose here an online version of MISI called oMISI, which is suitable for low-latency source separation, an important requirement for e.g., hearing aids applications. oMISI also allows one to use alternative phase initialization schemes exploiting the temporal structure of audio signals. Experiments conducted on a speech separation task show that oMISI performs as well as its offline counterpart, thus demonstrating its potential for real-time source separation.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research group: Audio research group - ARG, Computing Sciences, University of Toulouse, INP, LAAS-CNRS
Contributors: Magron, P., Virtanen, T.
Number of pages: 5
Pages: 306-310
Publication date: 2020
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 27
Article number: 8974192
ISSN (Print): 1070-9908
Original language: English
ASJC Scopus subject areas: Signal Processing, Electrical and Electronic Engineering, Applied Mathematics
Keywords: Audio source separation, low-latency, online spectrogram inversion, phase recovery, sinusoidal modeling
Source: Scopus
Source ID: 85080104357

Research output: Contribution to journalArticleScientificpeer-review

On the complexity of restoring corrupted colorings

In the r-Fix problem, we are given a graph G, a (non-proper) vertex-coloring c: V(G) → [r] , and a positive integer k. The goal is to decide whether a proper r-coloring c is obtainable from c by recoloring at most k vertices of G. Recently, Junosza-Szaniawski et al. (in: SOFSEM 2015: theory and practice of computer science, Springer, Berlin, 2015) asked whether the problem has a polynomial kernel parameterized by the number of recolorings k. In a full version of the manuscript, the authors together with Garnero and Montealegre, answered the question in the negative: for every r≥ 3 , the problem r-Fix does not admit a polynomial kernel unless [InlineEquation not available: see fulltext.]. Independently of their work, we give an alternative proof of the theorem. Furthermore, we study the complexity of r-Swap, where the only difference from r-Fix is that instead of k recolorings we have a budget of k color swaps. We show that for every r≥ 3 , the problem r-Swap is [InlineEquation not available: see fulltext.]-hard whereas r-Fix is known to be FPT. Moreover, when r is part of the input, we observe both Fix and Swap are [InlineEquation not available: see fulltext.]-hard parameterized by the treewidth of the input graph. We also study promise variants of the problems, where we are guaranteed that a proper r-coloring c is indeed obtainable from c by some finite number of swaps. For instance, we prove that for r= 3 , the problems r-Fix-Promise and r-Swap-Promise are [InlineEquation not available: see fulltext.]-hard for planar graphs. As a consequence of our reduction, the problems cannot be solved in 2o(n) time unless the Exponential Time Hypothesis fails.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, Bell Labs
Contributors: De Biasi, M., Lauri, J.
Number of pages: 20
Pages: 1150-1169
Publication date: May 2019
Peer-reviewed: Yes

Publication information

Journal: Journal of Combinatorial Optimization
Volume: 37
Issue number: 4
ISSN (Print): 1382-6905
Original language: English
ASJC Scopus subject areas: Computer Science Applications, Discrete Mathematics and Combinatorics, Control and Optimization, Computational Theory and Mathematics, Applied Mathematics
Keywords: Combinatorial reconfiguration, Computational complexity, Graph coloring, Local search, Parameterized complexity
Source: Scopus
Source ID: 85053264976

Research output: Contribution to journalArticleScientificpeer-review

On the Degree of Multi-Connectivity in 5G Millimeter-Wave Cellular Urban Deployments

Outage event caused by dynamic link blockage at millimeter-wave (mmWave) frequencies is a challenging problem for cell-edge users. To address it, 3GPP is currently working on multi-connectivity mechanisms that allow a user to remain connected to several mmWave access points simultaneously as well as switch between them in case its active connection drops. However, the actual number of such simultaneous links -- named the degree of multi-connectivity -- to reach the desired trade-off between the system design simplicity and the outage probability levels remains an open research question. In this work, we characterize the outage probability and spectral efficiency associated with different degrees of multi-connectivity in a typical 5G urban scenario, where the line-of-sight propagation path can be blocked by buildings as well as humans. These results demonstrate that the degrees of multi-connectivity of up to 4 offer higher relative gains. At the same time, performance improvements brought by the multi-connectivity degrees of 5 and higher are much lower. Our analytical framework can be further employed for the performance analysis of multi-connectivity-capable mmWave systems across their different deployment configurations.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Intel Corporation
Contributors: Gapeyenko, M., Petrov, V., Moltchanov, D., Akdeniz, M. R., Andreev, S., Himayat, N., Koucheryavy, Y.
Pages: 1973-1978
Publication date: Feb 2019
Peer-reviewed: Yes
Early online date: 2018

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 68
Issue number: 2
ISSN (Print): 0018-9545
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: dynamic human body blockage, macro diversity, mmWave systems, multi-connectivity, outage probability
Source: Scopus
Source ID: 85058896072

Research output: Contribution to journalArticleScientificpeer-review

On the effect of deformation twinning and microstructure to strain hardening of high manganese austenitic steel 3D microstructure aggregates at large strains

The hardening and deformation characteristics of Hadfield microstructure are studied to investigate the effect of microstucture to the material behavior. A crystal plasticity model including dislocation slip and deformation twinning is employed. The role of deformation twinning to the overall strain hardening of the material is evaluated for two different grain structures. Large compressive strains are applied on 3D microstructural aggregates representing the uniform and non-uniform grain structures of Hadfield steels. The grain structure has an effect on the strain hardening rate as well as on the overall hardening capability of the microstructure. A major reason causing the difference in strain hardening arises from the different twin volume fraction evolution influenced by intra-grain and inter-grain interactions. A mixture of large and small grains was found to be more favorable for twinning and thus resulting in a greater hardening capability than uniform grain size.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Materials Science, Research group: Materials Characterization, VTT Lifecycle Solutions
Contributors: Lindroos, M., Laukkanen, A., Cailletaud, G., Kuokkala, V.
Pages: 68-76
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: International Journal of Solids and Structures
Volume: 125
ISSN (Print): 0020-7683
Ratings: 
  • Scopus rating (2017): CiteScore 2.66 SJR 1.295 SNIP 1.574
Original language: English
ASJC Scopus subject areas: Modelling and Simulation, Materials Science(all), Condensed Matter Physics, Mechanics of Materials, Mechanical Engineering, Applied Mathematics
Keywords: Austenitic manganese steel, Crystal plasticity, Deformation twinning, Microstructure based modeling

Bibliographical note

EXT="Lindroos, Matti"

Source: Scopus
Source ID: 85025152227

Research output: Contribution to journalArticleScientificpeer-review

On the Performance of Visible Light Communication Systems with Non-Orthogonal Multiple Access

Visible light communication (VLC) has been proposed as a promising and efficient solution to indoor ubiquitous broadband connectivity. In this paper, non-orthogonal multiple access, which has been recently introduced as an effective scheme for fifth generation (5G) wireless networks, is considered in the context of VLC systems under different channel uncertainty models. To this end, we first derive a novel closed-form expression for the bit-error-rate (BER) under perfect channel state information (CSI). Capitalizing on this, we then quantify the effect of noisy and outdated CSI by deriving a simple and accurate approximation for the former and a tight upper bound for the latter. The offered results are corroborated by respective results from extensive Monte Carlo simulations and assist in developing useful insights on the effect of imperfect CSI knowledge on the overall system performance. Furthermore, it was shown that while noisy CSI leads to slight degradation in the BER performance, outdated CSI can cause considerable performance degradation, if the order of the users' channel gains change due to the involved mobility.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Khalifa University, Department of Electrical and Computer Engineering, University of Surrey, Aristotle University of Thessaloniki
Contributors: Marshoud, H., Sofotasios, P. C., Muhaidat, S., Karagiannidis, G. K., Sharif, B. S.
Number of pages: 15
Pages: 6350-6364
Publication date: 1 Oct 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Wireless Communications
Volume: 16
Issue number: 10
ISSN (Print): 1536-1276
Ratings: 
  • Scopus rating (2017): CiteScore 6.43 SJR 1.246 SNIP 2.451
Original language: English
ASJC Scopus subject areas: Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: bit-error-rate, dimming control, imperfect channel state information, non-orthogonal multiple access, Visible light communications
Source: Scopus
Source ID: 85023196523

Research output: Contribution to journalArticleScientificpeer-review

On the Temporal Effects of Mobile Blockers in Urban Millimeter-Wave Cellular Scenarios

Millimeter-wave (mmWave) propagation is known to be severely affected by the blockage of the line-of-sight (LoS) path. In contrast to microwave systems, at shorter mmWave wavelengths such blockage can be caused by human bodies, where their mobility within environment makes wireless channel alternate between the blocked and non-blocked LoS states. Following the recent 3GPP requirements on modeling the dynamic blockage as well as the temporal consistency of the channel at mmWave frequencies, in this paper a new model for predicting the state of a user in the presence of mobile blockers for representative 3GPP scenarios is developed: urban micro cell (UMi) street canyon and park/stadium/square. It is demonstrated that the blockage effects produce an alternating renewal process with exponentially distributed non-blocked intervals, and blocked durations that follow the general distribution. The following metrics are derived (i) the mean and the fraction of time spent in blocked/non-blocked state, (ii) the residual blocked/non-blocked time, and (iii) the time-dependent conditional probability of having blockage/no blockage at time t1 given that there was blockage/no blockage at time t0. The latter is a function of the arrival rate (intensity), width, and height of moving blockers, distance to the mmWave access point (AP), as well as the heights of the AP and the user device. The proposed model can be used for system-level characterization of mmWave cellular communication systems. For example, the optimal height and the maximum coverage radius of the mmWave APs are derived, while satisfying the required mean data rate constraint. The system-level simulations corroborate that the use of the proposed method considerably reduces the modeling complexity.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Emerging Technologies for Nano-Bio-Info-Cogno, ECE Department, Intel Corporation, Portland State University
Contributors: Gapeyenko, M., Samuylov, A., Gerasimenko, M., Moltchanov, D., Singh, S., Akdeniz, M. R., Aryafar, E., Himayat, N., Andreev, S., Koucheryavy, Y.
Pages: 10124-10138
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 66
Issue number: 11
ISSN (Print): 0018-9545
Ratings: 
  • Scopus rating (2017): CiteScore 4.69 SJR 0.75 SNIP 2.059
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: 3GPP, Analytical models, Biological system modeling, Cellular networks, Correlation, human body blockage, Mathematical model, mmWave, Mobile communication, mobility of blockers, temporal consistency, Vehicle dynamics
Source: Scopus
Source ID: 85030633275

Research output: Contribution to journalArticleScientificpeer-review

Opportunistic routing through conjugation in bacteria communication nanonetwork

As the field of molecular communication continues to grow, numerous solutions have been proposed to enable communication between nanomachines. Amongst these solutions, bacteria communication nanonetworks has been proposed as a promising approach for molecular communication. This is driven by a number of attractive properties found in bacteria, which includes biased motility toward the destination through chemotaxis process, as well as the ability of bacteria to transfer genetic information between each other using conjugation. Bacterial conjugation is a major mechanism for Lateral Gene Transfer (LGT) that enables information transfer among bacteria. In this paper, we propose an opportunistic routing process in bacteria communication network using these two properties. The paper presents the simulation work to analyze the performance of message delivery for three different topology shapes, which includes grid, hexagon, and T-shape topologies. The aim of simulating on different shape topologies is to determine the impact that conjugation will have to improve message delivery. In all topologies, the use of conjugation helped improve the reliability of message delivery to the destination point. The paper will analyze various commonly used metrics used in communication networks, such as the average delay, the number of messages, as well as the distribution of messages and their originating node. The conjugation process is most beneficial in complexed shaped topologies, where the directionality from the source to the destination is a number of hops apart, as represented in the T-shape topology.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Wireless Communications and Positioning (WICO), University of Cambridge, Telecommunications Software and Systems Group (TSSG), Waterford Institute of Technology
Contributors: Lio', P., Balasubramaniam, S.
Number of pages: 10
Pages: 36-45
Publication date: Mar 2012
Peer-reviewed: Yes

Publication information

Journal: Nano Communication Networks
Volume: 3
Issue number: 1
ISSN (Print): 1878-7789
Ratings: 
  • Scopus rating (2012): CiteScore 2.47 SJR 0.724 SNIP 2.354
Original language: English
ASJC Scopus subject areas: Computer Networks and Communications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Bacteria communication nanonetworks, Opportunistic routing
Source: Scopus
Source ID: 84858002058

Research output: Contribution to journalArticleScientificpeer-review

Optimal energy decay for the wave-heat system on a rectangular domain

We study the rate of energy decay for solutions of a coupled wave-heat system on a rectangular domain. Using techniques from the theory of C 0 -semigroups, and in particular a well-known result due to Borichev and Tomilov, we prove that the energy of classical solutions decays like t - 2/ 3 as t \rightarrow \infty . This rate is moreover shown to be sharp. Our result implies in particular that a general estimate in the literature, which predicts at least logarithmic decay and is known to be best possible in general, is suboptimal in the special case under consideration here. Our strategy of proof involves direct estimates based on separation of variables and a refined version of the technique developed in our earlier paper for a one-dimensional wave-heat system.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computing Sciences, St Giles
Contributors: Batty, C., Paunonen, L., Seifert, D.
Number of pages: 12
Pages: 808-819
Publication date: 2019
Peer-reviewed: Yes

Publication information

Journal: SIAM JOURNAL ON MATHEMATICAL ANALYSIS
Volume: 51
Issue number: 2
ISSN (Print): 0036-1410
Original language: English
ASJC Scopus subject areas: Analysis, Computational Mathematics, Applied Mathematics
Keywords: C -semigroups, Coupled, Energy, Heat equation, Rates of decay, Rectangular domain, Resolvent estimates, Wave equation
Source: Scopus
Source ID: 85065492247

Research output: Contribution to journalArticleScientificpeer-review

Organizational structure and the periphery of the gene regulatory network in B-cell lymphoma.

The physical periphery of a biological cell is mainly described by signaling pathways which are triggered by transmembrane proteins and receptors that are sentinels to control the whole gene regulatory network of a cell. However, our current knowledge about the gene regulatory mechanisms that are governed by extracellular signals is severely limited. The purpose of this paper is three fold. First, we infer a gene regulatory network from a large-scale B-cell lymphoma expression data set using the C3NET algorithm. Second, we provide a functional and structural analysis of the largest connected component of this network, revealing that this network component corresponds to the peripheral region of a cell. Third, we analyze the hierarchical organization of network components of the whole inferred B-cell gene regulatory network by introducing a new approach which exploits the variability within the data as well as the inferential characteristics of C3NET. As a result, we find a functional bisection of the network corresponding to different cellular components. Overall, our study allows to highlight the peripheral gene regulatory network of B-cells and shows that it is centered around hub transmembrane proteins located at the physical periphery of the cell. In addition, we identify a variety of novel pathological transmembrane proteins such as ion channel complexes and signaling receptors in B-cell lymphoma.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Prostate cancer research center (PCRC), Queen's University, Belfast, Northern Ireland, Computational Biology and Machine Learning Lab., Faculty of Medicine, Health and Life Sciences
Contributors: de Matos Simoes, R., Tripathi, S., Emmert-Streib, F.
Publication date: 14 May 2012
Peer-reviewed: Yes

Publication information

Journal: BMC Systems Biology
Volume: 6
Article number: 38
ISSN (Print): 1752-0509
Ratings: 
  • Scopus rating (2012): CiteScore 3.32 SJR 1.577 SNIP 1.009
Original language: English
ASJC Scopus subject areas: Molecular Biology, Structural Biology, Applied Mathematics, Modelling and Simulation, Computer Science Applications
Keywords: B-cell lymphoma, Gene expression data, Gene regulatory network, Statistical network inference
Source: Scopus
Source ID: 84865119369

Research output: Contribution to journalArticleScientificpeer-review

Performance analysis of simultaneous communications in bacterial nanonetworks

Utilizing biological components for data transfer is considered as a promising technique for communications at nanoscales. The ability to store data in its DNA strands as well as natural mobility make flagellated bacteria a good candidate for such systems. The use of advanced mechanisms such as replication-based encoding and conjugation to improve the performance of bacterial nanonetworks as well as stochastic bacteria movement pattern make their performance assessment a non-trivial task. Universal analytical frameworks taking into account these mechanisms are still missing. The situation is complicated by the possibility of having more than a single transmitter-receiver (Tx-Rx) pair communicating in the environment of interest. In this paper, we develop a framework to characterize performance of the bacterial networks taking all the abovementioned mechanisms into account and capable to address the case of simultaneous communications between a number of Tx-Rx pairs. The framework is based on the absorbing Markov chains theory and allows to reveal inherent trade-offs related to delay performance of bacterial nanonetworks.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electronics and Communications Engineering, School of Business Informatics, National Research University Higher School of Economics, Nano Communication Centre
Contributors: Komarov, M., Deng, B., Petrov, V., Moltchanov, D.
Number of pages: 13
Pages: 55-67
Publication date: 2016
Peer-reviewed: Yes

Publication information

Journal: Nano Communication Networks
Volume: 8
ISSN (Print): 1878-7789
Ratings: 
  • Scopus rating (2016): CiteScore 2.22 SJR 0.326 SNIP 0.793
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computer Networks and Communications, Electrical and Electronic Engineering
Keywords: Analytical model, Bacterial nanonetworks, Multiple Tx-Rx communicating pairs, Performance analysis
Source: Scopus
Source ID: 84978726703

Research output: Contribution to journalArticleScientificpeer-review

Properties of graph distance measures by means of discrete inequalities

In this paper, we investigate graph distance measures based on topological graph measures. Those measures can be used to measure the structural distance between graphs. When studying the scientific literature, one is aware that measuring distance/similarity between graphs meaningfully has been intricate. We demonstrate that our measures are well-defined and prove bounds for investigating their value domain. Also, we generate numerical results and demonstrate that the measures have useful properties.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Faculty of Biomedical Sciences and Engineering, Research group: Computational Medicine and Statistical Learning Laboratory (CMSL), Research group: Predictive Society and Data Analytics (PSDA), University of Applied Sciences Upper Austria, Nankai University, Institute for Bioinformatics and Translational Research, Laboratory of Biosystem Dynamics, Institute of Biosciences and Medical Technology, Institute for Intelligent Production, The City College of New York (CUNY)
Contributors: Dehmer, M., Chen, Z., Emmert-Streib, F., Shi, Y., Tripathi, S., Musa, A., Mowshowitz, A.
Number of pages: 11
Pages: 739-749
Publication date: 1 Jul 2018
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematical Modelling
Volume: 59
ISSN (Print): 0307-904X
Ratings: 
  • Scopus rating (2018): CiteScore 3.36 SJR 0.873 SNIP 1.495
Original language: English
ASJC Scopus subject areas: Modelling and Simulation, Applied Mathematics
Keywords: Distance measures, Graphs, Inequalities, Networks, Similarity measures

Bibliographical note

EXT="Tripathi, Shailesh"

Source: Scopus
Source ID: 85044481326

Research output: Contribution to journalArticleScientificpeer-review

Real-time observation of bacterial gene expression noise

The mRNA variability in the single cells attributes to random periods of transcription bursts. The cell cycle possesses a global role in affecting transcriptional output. By expressing this process as a communication system at the nanoscale, this transcription output often accounts for the gene expression noise, and this quantifies the promoter activity. However, current stochastic models ignore the fact that gene expression noise is affected not only by the cell cycle and promoter activity, but, also, by the time during which new mRNAs are produced. Here we show that noise from the lac promoter in E.coli is dominated by intrinsic and extrinsic noises in slow and fast dividing cells, respectively. Such domination of the noise components in phases with different generation times is achieved through distinct and combinatorial interactions between the upstream/downstream regulatory elements. These mechanisms serve as an adaptive strategy for increasing population homogeneity under changing environments.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Research group: Computational Systems Biology, Research group: Molecular Signaling Lab, Prostate cancer research center (PCRC)
Contributors: Anufrieva, O., Sala, A., Yli-Harja, O., Kandhavelu, M.
Pages: 68-75
Publication date: Jun 2016
Peer-reviewed: Yes
Early online date: 24 Mar 2016

Publication information

Journal: Nano Communication Networks
Volume: 8
ISSN (Print): 1878-7789
Ratings: 
  • Scopus rating (2016): CiteScore 2.22 SJR 0.326 SNIP 0.793
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computer Networks and Communications, Electrical and Electronic Engineering
Keywords: Bursty mRNA production, Cell cycle, Gene expression, lac promoter, Noise components
Source: Scopus
Source ID: 84992291852

Research output: Contribution to journalArticleScientificpeer-review

Restoration of low-dose digital breast tomosynthesis

In breast cancer screening, the radiation dose must be kept to the minimum necessary to achieve the desired diagnostic objective, thus minimizing risks associated with cancer induction. However, decreasing the radiation dose also degrades the image quality. In this work we restore digital breast tomosynthesis (DBT) projections acquired at low radiation doses with the goal of achieving a quality comparable to that obtained from current standard full-dose imaging protocols. A multiframe denoising algorithm was applied to low-dose projections, which are filtered jointly. Furthermore, a weighted average was used to inject a varying portion of the noisy signal back into the denoised one, in order to attain a signal-to-noise ratio comparable to that of standard full-dose projections. The entire restoration framework leverages a signal-dependent noise model with quantum gain which varies both upon the projection angle and on the pixel position. A clinical DBT system and a 3D anthropomorphic breast phantom were used to validate the proposed method, both on DBT projections and slices from the 3D reconstructed volume. The framework is shown to attain the standard full-dose image quality from data acquired at 50% lower radiation dose, whereas progressive loss of relevant details compromises the image quality if the dosage is further decreased.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Signal Processing, University of São Paulo, Noiseless Imaging Ltd, University of Pennsylvania
Contributors: Borges, L. R., Azzari, L., Bakic, P. R., Maidment, A. D., Vieira, M. A., Foi, A.
Publication date: 19 Apr 2018
Peer-reviewed: Yes

Publication information

Journal: Measurement Science and Technology
Volume: 29
Issue number: 6
Article number: 064003
ISSN (Print): 0957-0233
Ratings: 
  • Scopus rating (2018): CiteScore 2.21 SJR 0.57 SNIP 1.243
Original language: English
ASJC Scopus subject areas: Instrumentation, Engineering (miscellaneous), Applied Mathematics
Keywords: denoising, digital breast tomosynthesis, dose reduction, variance stabilization
Electronic versions: 
URLs: 
Source: Scopus
Source ID: 85047322570

Research output: Contribution to journalArticleScientificpeer-review

Robust controllers for regular linear systems with infinite-dimensional exosystems

We construct two error feedback controllers for robust output tracking and disturbance rejection of a regular linear system with nonsmooth reference and disturbance signals. We show that for sufficiently smooth signals the output converges to the reference at a rate that depends on the behavior of the transfer function of the plant on the imaginary axis. In addition, we construct a controller that can be designed to achieve robustness with respect to a given class of uncertainties in the system, and we present a novel controller structure for output tracking and disturbance rejection without the robustness requirement. We also generalize the internal model principle for regular linear systems with boundary disturbance and for controllers with unbounded input and output operators. The construction of controllers is illustrated with an example where we consider output tracking of a nonsmooth periodic reference signal for a two-dimensional heat equation with boundary control and observation, and with periodic disturbances on the boundary.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, Research group: Computer Science and Applied Logics
Contributors: Paunonen, L.
Number of pages: 31
Pages: 1567-1597
Publication date: 2017
Peer-reviewed: Yes

Publication information

Journal: SIAM Journal on Control and Optimization
Volume: 55
Issue number: 3
ISSN (Print): 0363-0129
Ratings: 
  • Scopus rating (2017): CiteScore 1.94 SJR 1.399 SNIP 1.723
Original language: English
ASJC Scopus subject areas: Control and Optimization, Applied Mathematics
Keywords: Controller Design, Feedback, Regular Linear Systems, Robust Output Regulation, Stability
Electronic versions: 
Source: Scopus
Source ID: 85021700145

Research output: Contribution to journalArticleScientificpeer-review

Robust data reconciliation of combustion variables in multi-fuel fired industrial boilers

This paper introduces an application of simultaneous nonlinear data reconciliation and gross error detection for power plants utilizing a complex but computationally light first principle combustion model. Element and energy balances and robust techniques introduce nonlinearity and the consequent optimization problem is solved using nonlinear optimization. Data reconciliation improves estimation of process variables and enables improved sensor quality control and identification of process anomalies. The approach was applied to an industrial 200 MWth fluidized bed boiler combusting wood, peat, bark, and slurry. The results indicate that the approach is valid and is able to perform in various process conditions. As the combustion model is generic, the method is applicable in any boiler environment.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Automation Science and Engineering, Research area: Dynamic Systems, Research area: Measurement Technology and Process Control, Indmeas Ltd.
Contributors: Korpela, T., Suominen, O., Majanne, Y., Laukkanen, V., Lautala, P.
Number of pages: 15
Pages: 101-115
Publication date: 21 Jul 2016
Peer-reviewed: Yes

Publication information

Journal: Control Engineering Practice
Volume: 55
ISSN (Print): 0967-0661
Ratings: 
  • Scopus rating (2016): CiteScore 3.42 SJR 1.076 SNIP 2.087
Original language: English
ASJC Scopus subject areas: Control and Systems Engineering, Electrical and Electronic Engineering, Applied Mathematics, Computer Science Applications
Keywords: Data reconciliation, Diagnostics, Estimation, Gross error detection, Monitoring, Power plant
Source: Scopus
Source ID: 84978710819

Research output: Contribution to journalArticleScientificpeer-review

Robust Inference for State-Space Models with Skewed Measurement Noise

Filtering and smoothing algorithms for linear discrete-time state-space models with skewed and heavy-tailed measurement noise are presented. The algorithms use a variational Bayes approximation of the posterior distribution of models that have normal prior and skew-t-distributed measurement noise. The proposed filter and smoother are compared with conventional low-complexity alternatives in a simulated pseudorange positioning scenario. In the simulations the proposed methods achieve better accuracy than the alternative methods, the computational complexity of the filter being roughly 5 to 10 times that of the Kalman filter.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Automation Science and Engineering, Research group: Positioning, Wireless Communications and Positioning (WICO), Linköping University
Contributors: Nurminen, H., Ardeshiri, T., Piché, R., Gustafsson, F.
Number of pages: 5
Pages: 1898-1902
Publication date: 1 Nov 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 22
Issue number: 11
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2015): CiteScore 3.13 SJR 0.822 SNIP 1.788
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics
Keywords: Kalman filter, robust filtering, RTS smoother, skew t, skewness, t-distribution, variational Bayes
Electronic versions: 
Source: Scopus
Source ID: 84933056939

Research output: Contribution to journalArticleScientificpeer-review

Rotation Invariant Texture Description Using Symmetric Dense Microblock Difference

This letter is devoted to the problem of rotation invariant texture classification. Novel rotation invariant feature, symmetric dense microblock difference (SDMD), is proposed which captures the information at different orientations and scales. N-fold symmetry is introduced in the feature design configuration, while retaining the random structure that provides discriminative power. The symmetry is utilized to achieve a rotation invariance. The SDMD is extracted using an image pyramid and encoded by the Fisher vector approach resulting in a descriptor which captures variations at different resolutions without increasing the dimensionality. The proposed image representation is combined with the linear SVM classifier. Extensive experiments are conducted on four texture data sets [Brodatz, UMD, UIUC, and Flickr material data set (FMD)] using standard protocols. The results demonstrate that our approach outperforms the state of the art in texture classification. The MATLAB code is made available.1 1Matlab Code: http://www.cs.tut.fi/~mehta/symdmd.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI
Contributors: Mehta, R., Egiazarian, K.
Number of pages: 5
Pages: 833-837
Publication date: 1 Jun 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 23
Issue number: 6
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2016): CiteScore 3.54 SJR 0.798 SNIP 1.758
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics
Keywords: image representation, local features, Rotation invariant features, texture classification
Source: Scopus
Source ID: 84970004897

Research output: Contribution to journalArticleScientificpeer-review

sgnesR: An R package for simulating gene expression data from an underlying real gene network structure considering delay parameters

Background: sgnesR (Stochastic Gene Network Expression Simulator in R) is an R package that provides an interface to simulate gene expression data from a given gene network using the stochastic simulation algorithm (SSA). The package allows various options for delay parameters and can easily included in reactions for promoter delay, RNA delay and Protein delay. A user can tune these parameters to model various types of reactions within a cell. As examples, we present two network models to generate expression profiles. We also demonstrated the inference of networks and the evaluation of association measure of edge and non-edge components from the generated expression profiles. Results: The purpose of sgnesR is to enable an easy to use and a quick implementation for generating realistic gene expression data from biologically relevant networks that can be user selected. Conclusions: sgnesR is freely available for academic use. The R package has been tested for R 3.2.0 under Linux, Windows and Mac OS X.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: BioMediTech, Faculty of Biomedical Sciences and Engineering, Signal Processing, Research group: Laboratory of Biosystem Dynamics-LBD, Research group: Computational Systems Biology, Research group: Computational Medicine and Statistical Learning Laboratory (CMSL), Research group: Predictive Society and Data Analytics (PSDA), Harvard T.H. Chan School of Public Health, Harvard School of Public Health, Mathematics and Operations Research
Contributors: Tripathi, S., Lloyd-Price, J., Ribeiro, A., Yli-Harja, O., Dehmer, M., Emmert-Streib, F.
Publication date: 4 Jul 2017
Peer-reviewed: Yes

Publication information

Journal: BMC Bioinformatics
Volume: 18
Issue number: 1
Article number: 325
ISSN (Print): 1471-2105
Ratings: 
  • Scopus rating (2017): CiteScore 2.49 SJR 1.479 SNIP 0.896
Original language: English
ASJC Scopus subject areas: Structural Biology, Biochemistry, Molecular Biology, Computer Science Applications, Applied Mathematics
Keywords: Gene expression data, Gene network, Simulation
Electronic versions: 
Source: Scopus
Source ID: 85021637056

Research output: Contribution to journalArticleScientificpeer-review

Solutions to integrals involving the marcum Q-function and applications

Novel analytic solutions are derived for integrals that involve the generalized Marcum Q -function, exponential functions and arbitrary powers. Simple closed-form expressions are also derived for specific cases of the generic integrals. The offered expressions are both convenient and versatile, which is particularly useful in applications relating to natural sciences and engineering, including wireless communications and signal processing. To this end, they are employed in the derivation of the average probability of detection in energy detection of unknown signals over multipath fading channels as well as of the channel capacity with fixed rate and channel inversion in the case of correlated multipath fading and switched diversity.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Wireless Communications and Positioning (WICO), Department of Electrical and Computer Engineering, Khalifa University, Centrefor Communication Systems Research, Department of Electronic Engineering, University of Surrey, Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki
Contributors: Sofotasios, P. C., Muhaidat, S., Karagiannidis, G. K., Sharif, B. S.
Number of pages: 5
Pages: 1752-1756
Publication date: 1 Oct 2015
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 22
Issue number: 10
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2015): CiteScore 3.13 SJR 0.822 SNIP 1.788
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics
Source: Scopus
Source ID: 84930225545

Research output: Contribution to journalArticleScientificpeer-review

Sparse Overcomplete Denoising: Aggregation Versus Global Optimization

Denoising is often addressed via sparse coding with respect to an overcomplete dictionary. There are two main approaches when the dictionary is composed of translates of an orthonormal basis. The first, traditionally employed by techniques such as wavelet cycle spinning, separately seeks sparsity w.r.t. each translate of the orthonormal basis, solving multiple partial optimizations and obtaining a collection of sparse approximations of the noise-free image, which are aggregated together to obtain a final estimate. The second approach, recently employed by convolutional sparse representations, instead seeks sparsity over the entire dictionary via a global optimization. It is tempting to view the former approach as providing a suboptimal solution of the latter. In this letter, we analyze whether global sparsity is a desirable property, and under what conditions the global optimization provides a better solution to the denoising problem. In particular, our experimental analysis shows that the two approaches attain comparable performance in case of natural images and global optimization outperforms the simpler aggregation of partial estimates only when the image admits an extremely sparse representation. We explain this phenomenon by separately studying the bias and variance of these solutions, and by noting that the variance of the global solution increases very rapidly as the original signal becomes less and less sparse.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Signal Processing, Politecnico di Milano, Los Alamos National Laboratory
Contributors: Carrera, D., Boracchi, G., Foi, A., Wohlberg, B.
Number of pages: 5
Pages: 1468-1472
Publication date: 1 Oct 2017
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 24
Issue number: 10
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2017): CiteScore 3.81 SJR 0.732 SNIP 1.77
Original language: English
ASJC Scopus subject areas: Signal Processing, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Convolutional sparse coding, denoising, overcomplete representations, sparse representations

Bibliographical note

EXT="Carrera, Diego"
EXT="Boracchi, Giacomo"

Source: Scopus
Source ID: 85029186566

Research output: Contribution to journalArticleScientificpeer-review

Spatial Interpolation of Cyclostationary Test Statistics in Cognitive Radio Networks: Methods and Field Measurements

The focus of this paper is on evaluating different spatial interpolation methods for the construction of radio environment map (REM) using field measurements obtained by cyclostationary based mobile sensors. Mobile sensing devices employing cyclostationary detectors provide lot of advantages compared to widely used energy detectors such as robustness to noise uncertainty and ability to distinguish among different primary user signals. However, mobile sensing results are not available at locations between the sensors making it difficult for a secondary user (possibly without a spectrum sensor) to decide whether or not to use primary user resources at that location. To overcome this, spatial interpolation of test statistics measured at limited number of locations can be carried out to create a channel occupancy map at unmeasured locations between the sensors. For this purpose, different spatial interpolation techniques for the cyclostationary test statistic have been employed in this paper such as inverse distance weighting (IDW), ordinary Kriging (OK), and universal Kriging (UK). The effectiveness of these methods is demonstrated by applying them on extensive real-world field measurement data obtained by mobile-phone-compliant spectrum sensors. The field measurements were carried out using four mobile spectrum sensors measuring eight DVB-T channels at more than hundred locations encompassing roughly one-third of the area of the city of Espoo in Finland. The accuracy of the spatial interpolation results based on the field measurements is determined using the cross validation approach with the widely used root mean square error (RMSE) as the metric. Field measurement results indicate that reliable results with spatial coverage can be achieved using Kriging for cyclostationary based test statistics. Comparison of spatial interpolation results of cyclostationary test statistics is also carried out with those of energy values obtained during the measurement campaign in the form of received signal strength indicator (RSSI). Comparison results clearly show the performance improvement and robustness obtained by the use of cyclostationary based detectors instead of energy detectors.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Research group: Wireless Communications and Positioning
Contributors: Chaudhari, S., Kosunen, M., Mäkinen, S., Chandrasekaran, R., Oksanen, J., Laatta, M., Ryynänen, J., Koivunen, V., Valkama, M.
Pages: 1113-1129
Publication date: 2018
Peer-reviewed: Yes

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 67
Issue number: 2
ISSN (Print): 0018-9545
Ratings: 
  • Scopus rating (2018): CiteScore 6.29 SJR 1.089 SNIP 2.256
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Computer Networks and Communications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Cognitive radio, cyclostationary detection, Databases, Detectors, energy detection, Hardware, Interference, Interpolation, Kriging, Mobile communication, radio environment map, spatial estimation, spectrum sensing
Source: Scopus
Source ID: 85021845608

Research output: Contribution to journalArticleScientificpeer-review

Spectral modeling of time series with missing data

Singular spectrum analysis is a natural generalization of principal component methods for time series data. In this paper we propose an imputation method to be used with singular spectrum-based techniques which is based on a weighted combination of the forecasts and hindcasts yield by the recurrent forecast method. Despite its ease of implementation, the obtained results suggest an overall good fit of our method, being able to yield a similar adjustment ability in comparison with the alternative method, according to some measures of predictive performance.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), ISLA Campus Lisbon, Laureate International Universities, Pontificia Universidad Católica de Chile
Contributors: Rodrigues, P. C., de Carvalho, M.
Number of pages: 9
Pages: 4676-4684
Publication date: 1 Apr 2013
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematical Modelling
Volume: 37
Issue number: 7
ISSN (Print): 0307-904X
Ratings: 
  • Scopus rating (2013): CiteScore 2.73 SJR 1.074 SNIP 1.961
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Modelling and Simulation
Keywords: Karhunen-Loève decomposition, Missing data, Singular spectrum analysis, Time series analysis
Source: Scopus
Source ID: 84872620531

Research output: Contribution to journalArticleScientificpeer-review

Stabilization to trajectories for parabolic equations

Both internal and boundary feedback exponential stabilization to trajectories for semilinear parabolic equations in a given bounded domain are addressed. The values of the controls are linear combinations of a finite number of actuators which are supported in a small region. A condition on the family of actuators is given which guarantees the local stabilizability of the control system. It is shown that a linearization-based Riccati feedback stabilizing controller can be constructed. The results of numerical simulations are presented and discussed.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Mathematics, Johann Radon Institute for Computational and Applied Mathematics
Contributors: Phan, D., Rodrigues, S. S.
Publication date: 1 Jun 2018
Peer-reviewed: Yes

Publication information

Journal: Mathematics of Control, Signals, and Systems
Volume: 30
Issue number: 2
Article number: 11
ISSN (Print): 0932-4194
Ratings: 
  • Scopus rating (2018): CiteScore 0.95 SJR 0.386 SNIP 0.701
Original language: English
ASJC Scopus subject areas: Control and Systems Engineering, Signal Processing, Control and Optimization, Applied Mathematics
Keywords: Feedback stabilization to trajectories, Semilinear parabolic equations
Source: Scopus
Source ID: 85050079985

Research output: Contribution to journalArticleScientificpeer-review

State Estimation for a Class of Piecewise Affine State-Space Models

We propose a filter for piecewise affine state-space models. In each filtering recursion, the true filtering posterior distribution is a mixture of truncated normal distributions. The proposed filter approximates the mixture with a single normal distribution via moment matching. The proposed algorithm is compared with the extended Kalman filter (EKF) in a numerical simulation, where the proposed method obtains, on average, better root mean square error than the EKF.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Automation Science and Engineering, Research area: Dynamic Systems, Research group: Positioning, Universidade Federal do Rio Grande do Sul, Porto Alegre, Linköping University
Contributors: Rui, R., Ardeshiri, T., Nurminen, H., Bazanella, A., Gustafsson, F.
Number of pages: 5
Pages: 61-65
Publication date: Jan 2017
Peer-reviewed: Yes
Early online date: 1 Dec 2016

Publication information

Journal: IEEE Signal Processing Letters
Volume: 24
Issue number: 1
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2017): CiteScore 3.81 SJR 0.732 SNIP 1.77
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics
Keywords: piecewise affine, state-space models, nonlinear filtering, Kalman filtering

Research output: Contribution to journalArticleScientificpeer-review

Still image/video frame lossy compression providing a desired visual quality

The problem of how to automatically provide a desired (required) visual quality in lossy compression of still images and video frames is considered in this paper. The quality can be measured based on different conventional and visual quality metrics. In this paper, we mainly employ human visual system (HVS) based metrics PSNR-HVS-M and MSSIM since both of them take into account several important peculiarities of HVS. To provide a desired visual quality with high accuracy, iterative image compression procedures are proposed and analyzed. An experimental study is performed for a large number of grayscale test images. We demonstrate that there exist several coders for which the number of iterations can be essentially decreased using a reasonable selection of the starting value and the variation interval for the parameter controlling compression (PCC). PCC values attained at the end of the iterative procedure may heavily depend upon the coder used and the complexity of the image. Similarly, the compression ratio also considerably depends on the above factors. We show that for some modern coders that take HVS into consideration it is possible to give practical recommendations on setting a fixed PCC to provide a desired visual quality in a non-iterative manner. The case when original images are corrupted by visible noise is also briefly studied.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI, National Aerospace University
Contributors: Zemliachenko, A., Lukin, V., Ponomarenko, N., Egiazarian, K., Astola, J.
Pages: 697-718
Publication date: 2016
Peer-reviewed: Yes

Publication information

Journal: Multidimensional Systems and Signal Processing
Volume: 27
Issue number: 3
ISSN (Print): 0923-6082
Ratings: 
  • Scopus rating (2016): CiteScore 1.47 SJR 0.424 SNIP 1.123
Original language: English
ASJC Scopus subject areas: Computer Science Applications, Information Systems, Signal Processing, Software, Artificial Intelligence, Hardware and Architecture, Applied Mathematics
Keywords: Compression ratio, Lossy compression, Required quality, Visual quality metrics
Source: Scopus
Source ID: 84930357751

Research output: Contribution to journalArticleScientificpeer-review

Structural influence of gene networks on their inference: Analysis of C3NET

Background: The availability of large-scale high-throughput data possesses considerable challenges toward their functional analysis. For this reason gene network inference methods gained considerable interest. However, our current knowledge, especially about the influence of the structure of a gene network on its inference, is limited.Results: In this paper we present a comprehensive investigation of the structural influence of gene networks on the inferential characteristics of C3NET - a recently introduced gene network inference algorithm. We employ local as well as global performance metrics in combination with an ensemble approach. The results from our numerical study for various biological and synthetic network structures and simulation conditions, also comparing C3NET with other inference algorithms, lead a multitude of theoretical and practical insights into the working behavior of C3NET. In addition, in order to facilitate the practical usage of C3NET we provide an user-friendly R package, called c3net, and describe its functionality. It is available from https://r-forge.r-project.org/projects/c3net and from the CRAN package repository.Conclusions: The availability of gene network inference algorithms with known inferential properties opens a new era of large-scale screening experiments that could be equally beneficial for basic biological and biomedical research with auspicious prospects. The availability of our easy to use software package c3net may contribute to the popularization of such methods.Reviewers: This article was reviewed by Lev Klebanov, Joel Bader and Yuriy Gusev.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), University of Cambridge, Computational Biology and Machine Learning Lab., Faculty of Medicine, Health and Life Sciences, Queen's University, Belfast, Northern Ireland, Cambridge Research Institute
Contributors: Altay, G., Emmert-Streib, F.
Publication date: 22 Jun 2011
Peer-reviewed: Yes

Publication information

Journal: Biology Direct
Volume: 6
Article number: 31
Ratings: 
  • Scopus rating (2011): CiteScore 3.6 SJR 2.274 SNIP 0.857
Original language: English
ASJC Scopus subject areas: Agricultural and Biological Sciences(all), Biochemistry, Genetics and Molecular Biology(all), Immunology, Applied Mathematics, Modelling and Simulation, Ecology, Evolution, Behavior and Systematics
Source: Scopus
Source ID: 79959327654

Research output: Contribution to journalArticleScientificpeer-review

Structural Measures for Network Biology Using QuACN

Background: Structural measures for networks have been extensively developed, but many of them have not yet demonstrated their sustainably. That means, it remains often unclear whether a particular measure is useful and feasible to solve a particular problem in network biology. Exemplarily, the classification of complex biological networks can be named, for which structural measures are used leading to a minimal classification error. Hence, there is a strong need to provide freely available software packages to calculate and demonstrate the appropriate usage of structural graph measures in network biology.Results: Here, we discuss topological network descriptors that are implemented in the R-package QuACN and demonstrate their behavior and characteristics by applying them to a set of example graphs. Moreover, we show a representative application to illustrate their capabilities for classifying biological networks. In particular, we infer gene regulatory networks from microarray data and classify them by methods provided by QuACN. Note that QuACN is the first freely available software written in R containing a large number of structural graph measures.Conclusion: The R package QuACN is under ongoing development and we add promising groups of topological network descriptors continuously. The package can be used to answer intriguing research questions in network biology, e.g., classifying biological data or identifying meaningful biological features, by analyzing the topology of biological networks.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Institute for Bioinformatics and Translational Research, Computational Biology and Machine Learning Lab., Faculty of Medicine, Health and Life Sciences, Queen's University, Belfast, Northern Ireland
Contributors: Mueller, L. A. J., Kugler, K. G., Graber, A., Emmert-Streib, F., Dehmer, M.
Publication date: 24 Dec 2011
Peer-reviewed: Yes

Publication information

Journal: BMC Bioinformatics
Volume: 12
Issue number: 1
Article number: 492
ISSN (Print): 1471-2105
Ratings: 
  • Scopus rating (2011): CiteScore 3.34 SJR 1.662 SNIP 1.196
Original language: English
ASJC Scopus subject areas: Biochemistry, Molecular Biology, Computer Science Applications, Applied Mathematics, Structural Biology
Source: Scopus
Source ID: 84155173344

Research output: Contribution to journalArticleScientificpeer-review

Structural Results for Quaternionic Gabor Frames

We study quaternionic Gabor frames based on the two-sided quaternionic windowed Fourier transform. Since classical Hilbert space based methods do not work in this case we introduce appropriated versions of translation and modulation operators. We prove Janssen’s and Walnut’s representations, as well as modified versions of the Wexler–Raz biorthogonality and Ron–Shen duality based on the concept of correlation function. We end up with a characterization of tight quaternionic Gabor frames.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Civil Engineering, Universidade de Aveiro
Contributors: Cerejeiras, P., Hartmann, S., Orelma, H.
Number of pages: 12
Publication date: 1 Nov 2018
Peer-reviewed: Yes

Publication information

Journal: Advances in Applied Clifford Algebras
Volume: 28
Issue number: 5
Article number: 86
ISSN (Print): 0188-7009
Ratings: 
  • Scopus rating (2018): CiteScore 0.9 SJR 0.4 SNIP 0.899
Original language: English
ASJC Scopus subject areas: Applied Mathematics
Keywords: Frame bounds, Janssen’s representation, Quaternionic frame operator, Quaternionic Gabor frames, Two-sided QWFT, Wexler–Raz biorthogonality
Source: Scopus
Source ID: 85053020211

Research output: Contribution to journalArticleScientificpeer-review

Structural similarity of directed universal hierarchical graphs: A low computational complexity approach

In the present paper we mainly introduce an efficient approach to measure the structural similarity of so called directed universal hierarchical graphs. We want to underline that directed universal hierarchical graphs can be obtained from generalized trees which are already introduced. In order to classify these graphs, we state our novel graph similarity method. As a main result we notice that our novel algorithm has low computational complexity.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: University of Veterinary Medicine Vienna, Stowers Institute for Medical Research
Contributors: Dehmer, M., Emmert-Streib, F.
Number of pages: 14
Pages: 7-20
Publication date: 1 Dec 2007
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 194
Issue number: 1
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2007): SJR 0.869 SNIP 1.113
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics, Numerical Analysis
Keywords: Complexity analysis, Graph classes, Graph classification, Graph similarity, Hierarchical models, Structured objects
Source: Scopus
Source ID: 35648968162

Research output: Contribution to journalArticleScientificpeer-review

Target tracking via combination of particle filter and optimisation techniques

Particle filters (PFs) have been used for the nonlinear estimation for a number of years. However, they suffer from the impoverishment phenomenon. It is brought by resampling which intends to prevent particle degradation, and therefore becomes the inherent weakness of this technique. To solve the problem of sample impoverishment and to improve the performance of the standard particle filter we propose a modification to this method by adding a sampling mechanism inspired by optimisation techniques, namely, the pattern search, particle swarm optimisation, differential evolution and Nelder-Mead algorithms. In the proposed methods, the true state of the target can be better expressed by the optimised particle set and the number of meaningful particles can be grown significantly. The efficiency of the proposed particle filters is supported by a truck-trailer problem. Simulations show that the hybridised particle filter with Nelder-Mead search is better than other optimisation approaches in terms of particle diversity.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, University of Toledo, Bowling Green State University
Contributors: Hosseini, S. S. S., Jamali, M. M., Astola, J., Gorsevski, P. V.
Number of pages: 18
Pages: 212-229
Publication date: 2016
Peer-reviewed: Yes

Publication information

Journal: International Journal of Mathematical Modelling and Numerical Optimization
Volume: 7
Issue number: 2
ISSN (Print): 2040-3607
Ratings: 
  • Scopus rating (2016): CiteScore 1.44 SJR 0.351 SNIP 0.935
Original language: English
ASJC Scopus subject areas: Numerical Analysis, Modelling and Simulation, Applied Mathematics
Keywords: Differential evolution, Nelder-Mead, Particle filter, Particle swarm optimisation, Pattern search, PSO, Target tracking
Source: Scopus
Source ID: 84990239582

Research output: Contribution to journalArticleScientificpeer-review

The Impact of Interference from the Side Lanes on mmWave/THz Band V2V Communication Systems with Directional Antennas

Communications systems operating in the millimeter and terahertz band have been recently suggested to enable high data-rate vehicle-to-vehicle communications in future networks. However, massive deployment of such systems may lead to significant interference, affecting the performance of information transmission. While the multipath interference caused by the signal reflections from the road has been extensively discussed in literature, the interference caused by the vehicles on the side lanes has been insufficiently studied so far. In this paper, using a combination of measurement, simulation, and analytical methods we comprehensively characterize the interference from the side lanes in two typical deployments including highway and urban road environments for millimeter and low terahertz bands. Both the multipath interference and direct interference from the transmitting vehicles on the side lanes are taken into account. As a result of the presented study, we reveal that: i) the interference from the side lanes can be well approximated using two-dimensional stochastic models without any notable loss of accuracy; and ii) even when highly directional antennas are used there are special spatial configurations, where the interference may greatly affect the communication systems performance. We lately apply the developed models to estimate the signal-to-interference ratio and link capacity of mmWave/THz band V2V communications with directional antennas.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Univ of Oulu, Centre for Wireless Communications Finland
Contributors: Petrov, V., Kokkoniemi, J., Moltchanov, D., Lehtomaki, J., Juntti, M., Koucheryavy, Y.
Pages: 5028-5041
Publication date: Jun 2018
Peer-reviewed: Yes
Early online date: 29 Jan 2018

Publication information

Journal: IEEE Transactions on Vehicular Technology
Volume: 67
Issue number: 6
ISSN (Print): 0018-9545
Ratings: 
  • Scopus rating (2018): CiteScore 6.29 SJR 1.089 SNIP 2.256
Original language: English
ASJC Scopus subject areas: Automotive Engineering, Aerospace Engineering, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Analytical models, Antenna measurements, Communication systems, Directional antennas, Interference, Millimeter waves, Propagation losses, Road transportation, SIR, THz band, Vehicle-to-Vehicle communications
Source: Scopus
Source ID: 85041396063

Research output: Contribution to journalArticleScientificpeer-review

The watching system as a generalization of identifying code

The watching system, as a generalization of identifying code, has been defined by Auger in 2010. The identifying code has been used to wireless networks and it has been also applied to locate objects in the sensor networks. On the other hand, the graph product is employed in most of the mathematic branches such as network design to study the structure of network elements. In this paper, we give some upper bounds for the watching number of well-know product graphs.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Computing Sciences, Teacher Training University, Swiss Distance University of Applied Sciences, Institute for Bioinformatics and Translational Research, Nankai University, Predictive Society and Data Analytics Lab
Contributors: Ghorbani, M., Dehmer, M., Maimani, H., Maddah, S., Roozbayani, M., Emmert-Streib, F.
Publication date: 1 Sep 2020
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 380
Article number: 125302
ISSN (Print): 0096-3003
Original language: English
ASJC Scopus subject areas: Computational Mathematics, Applied Mathematics
Keywords: Domination number, Graph products, Identifying code, Watching system
Source: Scopus
Source ID: 85083340308

Research output: Contribution to journalArticleScientificpeer-review

Topological mappings between graphs, trees and generalized trees

We present novel topological mappings between graphs, trees and generalized trees that means between structured objects with different properties. The two major contributions of this paper are, first, to clarify the relation between graphs, trees and generalized trees, a graph class recently introduced. Second, these transformations provide a unique opportunity to transform structured objects into a representation that might be beneficial for a processing, e.g., by machine learning techniques for graph classification.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Stowers Institute for Medical Research, Universität Rostock, Albert
Contributors: Emmert-Streib, F., Dehmer, M.
Number of pages: 8
Pages: 1326-1333
Publication date: 15 Mar 2007
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 186
Issue number: 2
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2007): SJR 0.869 SNIP 1.113
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics, Numerical Analysis
Keywords: Applied graph theory, Graph transformation, Hierarchical graphs
Source: Scopus
Source ID: 33947616843

Research output: Contribution to journalArticleScientificpeer-review

Transmit Power Optimization and Feasibility Analysis of Self-backhauling Full-Duplex Radio Access Systems

We analyze an inband full-duplex access node that is serving mobile users while simultaneously connecting to a core network over a wireless backhaul link, utilizing the same frequency band for all communication tasks. Such wireless self-backhauling is an intriguing option for the next generation wireless systems since a wired backhaul connection might not be economically viable if the access nodes are deployed densely. In particular, we derive the optimal transmit power allocation for such a system in closed form under Quality-of-Service (QoS) requirements, which are defined in terms of the minimum data rates for each mobile user. For comparison, the optimal transmit power allocation is solved also for two reference scenarios: a purely half-duplex access node, and a relay-type full-duplex access node. Based on the obtained expressions for the optimal transmit powers, we then show that the systems utilizing a full-duplex capable access node have a fundamental feasibility boundary, meaning that there are circumstances under which the QoS requirements cannot be fulfilled using finite transmit powers. This fundamental feasibility boundary is also derived in closed form. The feasibility boundaries and optimal transmit powers are then numerically evaluated in order to compare the different communication schemes. In general, utilizing the purely full-duplex access node results in the lowest transmit powers for all the communicating parties, although there are some network geometries under which such a system is not capable of reaching the required minimum data rates. In addition, the numerical results indicate that a full-duplex capable access node is best suited for relatively small cells.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Electronics and Communications Engineering, Rice University
Contributors: Korpi, D., Riihonen, T., Sabharwal, A., Valkama, M.
Pages: 4219-4236
Publication date: 2018
Peer-reviewed: Yes
Early online date: 7 Apr 2018

Publication information

Journal: IEEE Transactions on Wireless Communications
Volume: 17
Issue number: 6
ISSN (Print): 1536-1276
Ratings: 
  • Scopus rating (2018): CiteScore 7.79 SJR 1.692 SNIP 2.5
Original language: English
ASJC Scopus subject areas: Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: full-duplex wireless, massive MIMO, Self-backhauling, transmit power optimization
Electronic versions: 
Source: Scopus
Source ID: 85045199222

Research output: Contribution to journalArticleScientificpeer-review

Two-Sided Hypergenic Functions

In this paper we present an analogous of the class of two-sided axial monogenic functions to the case of axial κ-hypermonogenic functions. In order to do that we will solve a Vekua-type system in terms of Bessel functions.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Mathematics, Research group: MAT Clifford analysis, Department of Mathematics, CIDMA, Center for Research and Development in Mathematics and Applications
Contributors: Eriksson, S., Orelma, H., Vieira, N.
Number of pages: 14
Pages: 111–123
Publication date: 2017
Peer-reviewed: Yes
Early online date: 12 Sep 2015

Publication information

Journal: Advances in Applied Clifford Algebras
Volume: 27
Issue number: 1
ISSN (Print): 0188-7009
Ratings: 
  • Scopus rating (2017): CiteScore 0.96 SJR 0.698 SNIP 1.444
Original language: English
ASJC Scopus subject areas: Applied Mathematics
Keywords: $${\kappa}$$κ-Hypergenic functions, Clifford algebras, Hypergenic functions, Two-side hypergenic functions
Source: Scopus
Source ID: 84941331725

Research output: Contribution to journalArticleScientificpeer-review

Unbiased Injection of Signal-Dependent Noise in Variance-Stabilized Range

The design, optimization, and validation of many image processing or image-based analysis systems often requires testing of the system performance over a dataset of images corrupted by noise at different signal-to-noise ratio regimes. A noise-free ground-truth image may not be available, and different SNRs are simulated by injecting extra noise into an already noisy image. However, noise in real-world systems is typically signal-dependent, with variance determined by the noise-free image. Thus, also the noise to be injected shall depend on the unknown ground-truth image. To circumvent this issue, we consider the additive injection of noise in variance-stabilized range, where no previous knowledge of the ground-truth signal is necessary. Specifically, we design a special noise-injection operator that prevents the errors on expectation and variance that would otherwise arise when standard variance-stabilizing transformations are used for this task. Thus, the proposed operator is suitable for accurately injecting signal-dependent noise even to images acquired at very low counts.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Research group: Signal and Image Restoration-RST, Department of Applied Physics
Contributors: Borges, L., Vieira, M., Foi, A.
Pages: 1494-1498
Publication date: 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 23
Issue number: 10
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2016): CiteScore 3.54 SJR 0.798 SNIP 1.758
Original language: English
ASJC Scopus subject areas: Signal Processing, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Anscombe transformation, Noise injection, optimization, Poisson noise, variance stabilization
Electronic versions: 
Source: Scopus
Source ID: 85027556734

Research output: Contribution to journalArticleScientificpeer-review

Uncertainty propagation of iron loss from characterization measurements to computation of electrical machines

Purpose - The purpose of this paper is to find out how uncertainties in the characterization of magnetic materials propagate through identification and numerical simulation to the computation of iron losses in electrical machines. Design/methodology/approach - The probabilistic uncertainties in the iron losses are modelled with the spectral approach using chaos polynomials. The Sobol indices are used for the global sensitivity analysis. The machine is modelled with a 2D finite element method and the iron losses are computed with a previously developed accurate method. Findings - The uncertainties propagate in different ways to the different components of losses, i.e. eddy current, hysteresis, and excess losses. The propagation is also different depending on the investigated region of the machine, i.e. Stator or rotor teeth, yokes, tooth tips. Research limitations/implications - The method does not account for uncertainties related to the manufacturing process, which might result in even larger variability. Practical implications - A major implication of the findings is that the identification of iron loss parameters at low frequencies does not affect the loss variability. The identification with high-frequency measurement is very important for the rotor tooth tips. The variability in the excess loss parameters is of low impact. Originality/value - The presented results are of importance for the magnetic material manufacturers and the electrical machine designers. The manufacturers can plan the measurement and identification procedures as to minimize the output variability of the parameters. The designers of the machine can use the result and the presented procedures to estimate the variability of their design.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Smart Energy Systems (SES), Aalto University, L2EP, Université Lille 1, L2EP, Arts et Metiers Paris Tech
Contributors: Belahcen, A., Rasilo, P., Nguyen, T. T., Clénet, S.
Number of pages: 13
Pages: 624-636
Publication date: 2015
Peer-reviewed: Yes

Publication information

Journal: COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering
Volume: 34
Issue number: 3
ISSN (Print): 0332-1649
Ratings: 
  • Scopus rating (2015): CiteScore 0.68 SJR 0.231 SNIP 0.554
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Computational Theory and Mathematics, Applied Mathematics
Keywords: Electrical machine, Finite element methods, Iron losses, Uncertainty estimation
Source: Scopus
Source ID: 84929258660

Research output: Contribution to journalArticleScientificpeer-review

Universal construction mechanism for networks from one-dimensional symbol sequences

In this paper we introduce construction mechanisms to generate directed networks from one-dimensional symbol sequences. We prove that any of these construction mechanism leads to the same undirected network. Further, we prove that the introduced construction mechanisms are universal in the sense that any undirected network can be generated by such a mechanism. In addition, we provide various numerical examples to demonstrate the applicability of the introduced mechanism.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Research Community on Data-to-Decision (D2D), Computational Biology and Machine Learning, Queen's University, Belfast, Northern Ireland
Contributors: Emmert-Streib, F.
Number of pages: 11
Pages: 1020-1030
Publication date: 15 Oct 2012
Peer-reviewed: Yes

Publication information

Journal: Applied Mathematics and Computation
Volume: 219
Issue number: 3
ISSN (Print): 0096-3003
Ratings: 
  • Scopus rating (2012): CiteScore 1.77 SJR 1.02 SNIP 1.295
Original language: English
ASJC Scopus subject areas: Applied Mathematics, Computational Mathematics
Keywords: Complex networks, Network construction, Random networks, Symbol sequences, Universal network construction
Source: Scopus
Source ID: 84867336661

Research output: Contribution to journalArticleScientificpeer-review

Urothelial cancer gene regulatory networks inferred from large-scale RNAseq, Bead and Oligo gene expression data

Background: Urothelial pathogenesis is a complex process driven by an underlying network of interconnected genes. The identification of novel genomic target regions and gene targets that drive urothelial carcinogenesis is crucial in order to improve our current limited understanding of urothelial cancer (UC) on the molecular level. The inference of genome-wide gene regulatory networks (GRN) from large-scale gene expression data provides a promising approach for a detailed investigation of the underlying network structure associated to urothelial carcinogenesis. Methods: In our study we inferred and compared three GRNs by the application of the BC3Net inference algorithm to large-scale transitional cell carcinoma gene expression data sets from Illumina RNAseq (179 samples), Illumina Bead arrays (165 samples) and Affymetrix Oligo microarrays (188 samples). We investigated the structural and functional properties of GRNs for the identification of molecular targets associated to urothelial cancer. Results: We found that the urothelial cancer (UC) GRNs show a significant enrichment of subnetworks that are associated with known cancer hallmarks including cell cycle, immune response, signaling, differentiation and translation. Interestingly, the most prominent subnetworks of co-located genes were found on chromosome regions 5q31.3 (RNAseq), 8q24.3 (Oligo) and 1q23.3 (Bead), which all represent known genomic regions frequently deregulated or aberated in urothelial cancer and other cancer types. Furthermore, the identified hub genes of the individual GRNs, e.g., HID1/DMC1 (tumor development), RNF17/TDRD4 (cancer antigen) and CYP4A11 (angiogenesis/ metastasis) are known cancer associated markers. The GRNs were highly dataset specific on the interaction level between individual genes, but showed large similarities on the biological function level represented by subnetworks. Remarkably, the RNAseq UC GRN showed twice the proportion of significant functional subnetworks. Based on our analysis of inferential and experimental networks the Bead UC GRN showed the lowest performance compared to the RNAseq and Oligo UC GRNs. Conclusion: To our knowledge, this is the first study investigating genome-scale UC GRNs. RNAseq based gene expression data is the data platform of choice for a GRN inference. Our study offers new avenues for the identification of novel putative diagnostic targets for subsequent studies in bladder tumors.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, BioMediTech, Research Community on Data-to-Decision (D2D), BioMediTech - Institute of Biosciences and Medical Technology, Queen's University, Belfast, Northern Ireland
Contributors: Matos Simoes, R. D., Dalleau, S., Williamson, K. E., Emmert-Streib, F.
Publication date: 14 May 2015
Peer-reviewed: Yes

Publication information

Journal: BMC Systems Biology
Volume: 9
Article number: 21
ISSN (Print): 1752-0509
Ratings: 
  • Scopus rating (2015): CiteScore 2.54 SJR 1.549 SNIP 0.89
Original language: English
ASJC Scopus subject areas: Molecular Biology, Structural Biology, Applied Mathematics, Modelling and Simulation, Computer Science Applications
Keywords: BC3Net, Computational genomics, Gene regulatory network, Urothelial cancer
Source: Scopus
Source ID: 84931068065

Research output: Contribution to journalArticleScientificpeer-review

Variance Stabilization for Noisy+Estimate Combination in Iterative Poisson Denoising

We denoise Poisson images with an iterative algorithm that progressively improves the effectiveness of variance-stabilizing transformations (VST) for Gaussian denoising filters. At each iteration, a combination of the Poisson observations with the denoised estimate from the previous iteration is treated as scaled Poisson data and filtered through a VST scheme. Due to the slight mismatch between a true scaled Poisson distribution and this combination, a special exact unbiased inverse is designed. We present an implementation of this approach based on the BM3D Gaussian denoising filter. With a computational cost at worst twice that of the noniterative scheme, the proposed algorithm provides significantly better quality, particularly at low signal-to-noise ratio, outperforming much costlier state-of-the-art alternatives.

General information

Publication status: Published
MoE publication type: A1 Journal article-refereed
Organisations: Department of Signal Processing, Research group: Signal and Image Restoration-RST
Contributors: Azzari, L., Foi, A.
Number of pages: 5
Pages: 1086-1090
Publication date: 1 Aug 2016
Peer-reviewed: Yes

Publication information

Journal: IEEE Signal Processing Letters
Volume: 23
Issue number: 8
ISSN (Print): 1070-9908
Ratings: 
  • Scopus rating (2016): CiteScore 3.54 SJR 0.798 SNIP 1.758
Original language: English
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics
Keywords: Anscombe transformation, image denoising, iterative filtering, photon-limited imaging, Poisson noise
Electronic versions: 
Additional files: 
Source: Scopus
Source ID: 84979891796

Research output: Contribution to journalArticleScientificpeer-review

A simulation case study of production planning and control in printed wiring board manufacturing

Production planning and control in printed wiring board (PWB) manufacturing is becoming more difficult as PWB's technology is developing and the production routings become more complex. Simultaneously, the strategic importance of delivery accuracy, short delivery times, and production flexibility is increasing with the highly fluctuating demand and short product life cycles of end products. New principles, that minimize throughput time while guaranteering excellent customer service and adequate capacity utilization, are needed for production planning and control. Simulation is needed in order to develop the new principles and test their superiority. This paper presents an ongoing simulation product that aims at developing the production planning and control of a PWB manufacturer. In the project, a discrete event simulation model is built of a pilot case factory. The model is used for comparing the effect of scheduling, queuing rules, buffer policies, and lot sizes on customer service and cost efficiency.

General information

Publication status: Published
MoE publication type: Not Eligible
Organisations: Industrial Engineering and Management, Aalto University, TAI Research Centre
Contributors: Korhonen, H. M. E., Heikkilä, J., Törnwall, J. M.
Number of pages: 4
Pages: 844-847
Publication date: 1 Dec 2001
Peer-reviewed: Yes

Publication information

Journal: Winter Simulation Conference Proceedings
Volume: 2
ISSN (Print): 0275-0708
Ratings: 
  • Scopus rating (2001): SJR 0.377
Original language: English
ASJC Scopus subject areas: Chemical Health and Safety, Software, Safety, Risk, Reliability and Quality, Applied Mathematics, Modelling and Simulation
Source: Scopus
Source ID: 0035708229

Research output: Contribution to journalConference articleScientificpeer-review

Acoustic Modelling

Let us examine the behaviour of sound in a gas or in a liquid medium. From a physical point of view, the sound we hear is created by the pressure change in the medium surrounding us that is sensed by our ears. The equations describing the behaviour of a liquid or a gas are based on well-known equations of fluid mechanics. Therefore in acoustics, they are often referred to as fluids. In the following sections we present a simple wave equation, which is the simplest of (linear) equations used to model acoustical phenomena. Even though the wave equation is quite a simplified model, it has proven to be extremely useful for describing the behaviour of sound in the most common fluid we face every day, namely air.

General information

Publication status: Published
MoE publication type: A3 Part of a book or another research book
Organisations: Department of Mathematics, Research group: MAT Intelligent Information Systems Laboratory, Research group: MAT Mathematical and semantic modelling, Tampere Univ Technol, Tampere University of Technology
Contributors: Pohjolainen, S., Suutala, A.
Number of pages: 21
Pages: 185-205
Publication date: 30 Jun 2016

Host publication information

Title of host publication: Mathematical Modelling
Place of publication: Switzerland
Publisher: Springer
Editor: Pohjolainen, S.
ISBN (Print): 978-3-319-27834-6
ISBN (Electronic): 978-3-319-27836-0
ASJC Scopus subject areas: Applied Mathematics, Modelling and Simulation, Acoustics and Ultrasonics

Bibliographical note

INT=mat,”Suutala, Antti"

Research output: Chapter in Book/Report/Conference proceedingChapterScientificpeer-review

1180nm VECSEL with 50 W output power

We report on the development of a high-power vertical-external-cavity surface-emitting laser (VECSEL) emitting around 1180 nm. The laser emitted 50 W of output power when the mount of the gain chip was cooled to -15°C. The output power was measured using a 97% reflective cavity end-mirror. The VECSEL was arranged to form an I-shaped cavity with a length of ∼100 mm; the gain chip and a curved dielectric mirror (RoC=150) acting as cavity end mirrors. The gain chip was grown by molecular beam epitaxy (MBE) and incorporated 10 GaInAs/GaAs quantum wells. For efficient heat extraction, the chip was capillary bonded to a diamond heat spreader which was attached to a TEC-cooled copper mount. The maximum optical-to-optical conversion efficiency of 28% was achieved for 42 W of output power and -15°C mount temperature.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Frontier Photonics
Contributors: Kantola, E., Leinonen, T., Ranta, S., Tavast, M., Penttinen, J., Guina, M.
Publication date: 2015

Host publication information

Title of host publication: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 9349
Publisher: SPIE
Article number: 93490U
ISBN (Print): 9781628414394
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: continuous wave, frequency doubling, heat management, high power, infrared, power scaling, SDL, VECSEL
Source: Scopus
Source ID: 84925666801

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

1.3μm U-bend traveling wave SOA devices for high efficiency coupling to silicon photonics

We present a U-bend design for traveling wave III-V gain devices, such as semiconductor optical amplifiers and laser diodes. The design greatly simplifies the butt-coupling between the III-V chip and silicon-on-insulator photonic circuit by bringing the I/O ports on one facet. This removes the need for precise dimension control otherwise required for 2-side coupling, therefore increasing the yield of mounted devices towards 100%. The design, fabrication and characterization of the U-bend device based on Euler bend geometry is presented. The losses for a bend with a minimum bending radius of 83 μm are 1.1 dB. In addition, we present an analysis comparing the yield and coupling losses of the traditionally cleaved devices with the results that the Euler bend approach enable, with the final conclusion that the yield is improved by several times while the losses are decreased by several dB.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, VTT Technical Research Centre of Finland
Contributors: Viheriälä, J., Tuorila, H., Zia, N., Cherchi, M., Aalto, T., Guina, M.
Publication date: 2019

Host publication information

Title of host publication: Silicon Photonics XIV
Publisher: SPIE, IEEE
Editors: Reed, G. T., Knights, A. P.
Article number: 109230E
ISBN (Electronic): 9781510624887

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10923
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Coupling losses, Hybrid integration, III-V, Semiconductor optical amplifiers, Silicon-on-insulator

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85065404814

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

1.55-μm wavelength wafer-fused OP-VECSELs in flip-chip configuration

Optically-pumped vertical external cavity surface emitting lasers (VECSELs) based on flip-chip gain mirrors emitting at the 1.55-μm wavelength range are reported. The gain mirrors employ wafer-fused InAlGaAs/InP quantum well heterostructures and GaAs/AlAs distributed Bragg reflectors, which were incorporated in a linear and a V-cavity configurations. A maximum output power of 3.65 W was achieved for a heatsink temperature of 11°C and employing a 2.2% output coupler. The laser exhibited circular beam profiles for the full emission power range. The demonstration represents more than 10-fold increase of the output power compared to state-of-the-art flip-chip VECSELs previously demonstrated at the 1.55-μm wavelength range, and opens a new perspective for developing practical VECSEL-based laser system for applications such as LIDAR, spectroscopy, communications and distributed sensing.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, CRPP, LakeDiamond SA
Contributors: Mereuta, A., Nechay, K., Caliman, A., Suruceanu, G., Gallo, P., Guina, M., Kapon, E.
Publication date: 2019

Host publication information

Title of host publication: Vertical External Cavity Surface Emitting Lasers (VECSELs) IX
Publisher: SPIE, IEEE
Editor: Keller, U.
Article number: 1090103
ISBN (Electronic): 9781510624443

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10901
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Optically-pumped VECSELs, Semiconductor lasers, Wafer-Fusion

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85066636665

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

405-nm pumped Ce3+-doped silica fiber for broadband fluorescence from cyan to red

A pure Ce-doped silica fiber is fabricated using modified chemical vapor deposition (MCVD) technique. Fluorescence characteristics of a Ce-doped silica fiber are experimentally investigated with continuous wave pumping from 440 nm to 405 nm. Best pump absorption and broad fluorescence spectrum is observed for ∼ 405 nm laser. Next, the detailed analysis of spectral response as a function of pump power and fiber length is performed. It is observed that a-10dB spectral width of ∼ 280 mn can be easily achieved with different combinations of the fiber length and pump power. Lastly, we present, for the first time to the best of our knowledge, a broadband fluorescence spectrum with-10dB spectral width of 301 nm, spanning from ∼ 517.36 nm to ∼ 818 nm, from such fibers with non-UV pump lasers.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Aston University, Fiber Optics Research Center of the Russian Academy of Sciences, Russian Academy of Sciences
Contributors: Yadav, A., Chichkov, N. B., Gumenyuk, R., Zherebtsov, E., Melkumov, M. A., Yashkov, M. V., Dianov, E. M., Rafailov, E. U.
Publication date: 2019

Host publication information

Title of host publication: Optical Components and Materials XVI
Publisher: SPIE, IEEE
Editors: Digonnet, M. J. F., Jiang, S.
Article number: 1091406
ISBN (Electronic): 9781510624702

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10914
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Broadband spectrum, Ce-doped fiber, Ce-ion, Rare earth doped

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85066046508

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Action and power efficiency in self-organization: The case for growth efficiency as a cellular objective in escherichia coli

Complex systems of different nature self-organize using common mechanisms. One of those is increase of their efficiency. The level of organization of complex systems of different nature can be measured as increased efficiency of the product of time and energy for an event, which is the amount of physical action consumed by it. Here we apply a method developed in physics to study the efficiency of biological systems. The identification of cellular objectives is one of the central topics in the research of microbial metabolic networks. In particular, the information about a cellular objective is needed in flux balance analysis which is a commonly used constrained-based metabolic network analysis method for the prediction of cellular phenotypes. The cellular objective may vary depending on the organism and its growth conditions. It is probable that nutritionally scarce conditions are very common in the nature, and, in order to survive in those conditions, cells exhibit various highly efficient nutrient-processing systems like enzymes. In this study, we explore the efficiency of a metabolic network in transformation of substrates to new biomass, and we introduce a new objective function simulating growth efficiency. We are searching for general principles of self-organization across systems of different nature. The objective of increasing efficiency of physical action has been identified previously as driving systems toward higher levels of self-organization. The flow agents in those networks are driven toward their natural state of motion, which is governed by the principle of least action in physics. We connect this to a power efficiency principle. Systems structure themselves in a way to decrease the average amount of action or power per one event in the system. In this particular example, action efficiency is examined in the case of growth efficiency of E. coli. We derive the expression for growth efficiency as a special case of action (power) efficiency to justify it through first principles in physics. Growth efficiency as a cellular objective of E. coli coincides with previous research on complex systems and is justified by first principles in physics. It is expected and confirmed outcome of this work. We examined the properties of growth efficiency using a metabolic model for Escherichia coli. We found that the maximal growth efficiency is obtained at a finite nutrient uptake rate. The rate is substrate dependent and it typically does not exceed 20 mmol/h/gDW. We further examined whether the maximal growth efficiency could serve as a cellular objective function in metabolic network analysis and found that cellular growth in batch cultivation can be predicted reasonably well under this assumption. The fit to experimental data was found slightly better than with the commonly used objective function of maximal growth rate. Based on our results, we suggest that the maximal growth efficiency can be considered a plausible optimization criterion in metabolic modeling for E. coli. In the future, it would be interesting to study growth efficiency as an objective also in other cellular systems and under different cultivation conditions.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: BioMediTech, Wireless Innovation Laboratory at Worcester Polytechnic Institute, Assumption College, Tufts University, Complex Systems Center, University of Vermont
Contributors: Georgiev, G. Y., Aho, T., Kesseli, J., Yli-Harja, O., Kauffman, S. A.
Number of pages: 16
Pages: 229-244
Publication date: 2019

Host publication information

Title of host publication: Evolution, Development and Complexity - Multiscale Evolutionary Models of Complex Adaptive Systems
Publisher: Springer
Editors: Flores Martinez, C. L., Georgiev, G. Y., Smart, J. M., Price, M. E.
ISBN (Print): 9783030000745

Publication series

Name: Springer Proceedings in Complexity
ISSN (Print): 2213-8684
ISSN (Electronic): 2213-8692
ASJC Scopus subject areas: Applied Mathematics, Modelling and Simulation, Computer Science Applications
Keywords: Action efficiency, Constraint-based modeling, Metabolism, Microorganism, Principle of least action

Bibliographical note

jufoid=84878

Source: Scopus
Source ID: 85071889407

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Action recognition using the 3D dense microblock difference

This paper describes a framework for action recognition which aims to recognize the goals and activities of one or more human from a series of observations. We propose an approach for the human action recognition based on the 3D dense micro-block difference. The proposed algorithm is a two-stage procedure: (a) image preprocessing using a 3D Gabor filter and (b) a descriptor calculation using 3D dense micro-block difference with SVM classifier. At the first step, an efficient spatial computational scheme designed for the convolution with a bank of 3D Gabor filters is present. This filter intensifies motion using a convolution for a set of 3D patches and arbitrarily-oriented anisotropic Gaussian. For preprocessed frames, we calculate the local features such as 3D dense micro-block difference (3D DMD), which capture the local structure from the image patches at high scales. This approach is processing the small 3D blocks with different scales from frames which capture the microstructure from it. The proposed image representation is combined with fisher vector method and linear SVM classifier. We evaluate the proposed approach on the UCF50, HMDB51 and UCF101 databases. Experimental results demonstrate the effectiveness of the proposed approach on video with a stochastic textures background with comparisons of the state-of-The-Art methods.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing, Don State Technical University, Moscow State University of Technology 'Stankin', Beijing Jiaotong University
Contributors: Voronin, V., Pismenskova, M., Zelensky, A., Cen, Y., Nadykto, A., Egiazarian, K.
Publication date: 2018

Host publication information

Title of host publication: Counterterrorism, Crime Fighting, Forensics, and Surveillance Technologies II
Publisher: SPIE
Article number: 108020O
ISBN (Electronic): 9781510621879

Publication series

Name: Proceedings of SPIE
Volume: 10802
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: 3D Gabor filter., Action recognition, Micro-block difference, Texture

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85057423236

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A hand-held immaterial volumetric display

We have created an ultralight, movable, "immaterial" fogscreen. It is based on the fogscreen mid-air imaging technology. The hand-held unit is roughly the size and weight of an ordinary toaster. If the screen is tracked, it can be swept in the air to create mid-air slices of volumetric objects, or to show augmented reality (AR) content on top of real objects. Interfacing devices and methodologies, such as hand and gesture trackers, camera-based trackers and object recognition, can make the screen interactive. The user can easily interact with any physical object or virtual information, as the screen is permeable. Any real objects can be seen through the screen, instead of e.g., through a video-based augmented reality screen. It creates a mixed reality setup where both the real world object and the augmented reality content can be viewed and interacted with simultaneously. The hand-held mid-air screen can be used e.g., as a novel collaborating or classroom tool for individual students or small groups.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Augmented Human Activities (AHA), University of Tampere
Contributors: Sand, A., Rakkolainen, I.
Publication date: 2014

Host publication information

Title of host publication: Proceedings of SPIE-IS and T Electronic Imaging - Stereoscopic Displays and Applications XXV
Volume: 9011
Publisher: SPIE
Article number: 90110Q
ISBN (Print): 9780819499288
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: display technology, Fog screen, mixed reality, volumetric, walk-through screen
Source: Scopus
Source ID: 84901008644

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A membrane external-cavity surface-emitting laser (MECSEL) with emission around 825 nm

A MECSEL emitting around 825nm is reported. With a tuning range from 807nm to 840 nm, the MECSEL extends the coverage of high beam quality semiconductor based lasers in the short 8XXnm region and opens new perspectives for scanning ground-based water-vapor differential absorption lidar. 1.4W maximum output power has been achieved at room temperature operation and at 12.5W absorbed power using a 532 nm emitting pump laser. The beam quality has been investigated by M2 measurements at different pump power. The effect from a growing pump mode and thermal lensing has been observed as the beam divergence angle decreases and the beam waist radius enlargens with increasing pump power.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Research group: ORC
Contributors: Phung, H. M., Kahle, H., Penttinen, J., Rajala, P., Ranta, S., Guina, M.
Publication date: 2020

Host publication information

Title of host publication: Vertical External Cavity Surface Emitting Lasers (VECSELs) X
Publisher: SPIE
Editor: Hastie, J. E.
Article number: 112630H
ISBN (Print): 9781510632899
ISBN (Electronic): 9781510632905

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 11263
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: GaInAsP, MECSEL, Semiconductor laser, Short 8XXnm region, SiC heatspreaders, Thermal lensing, VECSEL

Bibliographical note

INT=phys,"Rajala, Patrik"
jufoid=71479

Source: Scopus
Source ID: 85082694209

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A method for predicting DCT-based denoising efficiency for grayscale images corrupted by AWGN and additive spatially correlated noise

Results of denoising based on discrete cosine transform for a wide class of images corrupted by additive noise are obtained. Three types of noise are analyzed: additive white Gaussian noise and additive spatially correlated Gaussian noise with middle and high correlation levels. TID2013 image database and some additional images are taken as test images. Conventional DCT filter and BM3D are used as denoising techniques. Denoising efficiency is described by PSNR and PSNR-HVS-M metrics. Within hard-thresholding denoising mechanism, DCT-spectrum coefficient statistics are used to characterize images and, subsequently, denoising efficiency for them. Results of denoising efficiency are fitted for such statistics and efficient approximations are obtained. It is shown that the obtained approximations provide high accuracy of prediction of denoising efficiency.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI, Signal Processing Research Community (SPRC), National Aerospace University
Contributors: Rubel, A. S., Lukin, V. V., Egiazarian, K.
Publication date: 2015

Host publication information

Title of host publication: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 9399
Publisher: SPIE
Article number: 93990P
ISBN (Print): 9781628414899
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: DCT and BM3D filter, Denoising, Fitting, Grayscale images, Prediction
Source: Scopus
Source ID: 84928473717

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A mixed-integer linear programming approach for global discrete size optimization of frame structures

This paper proposes a method to solve discrete size optimization problems of frame structures to global optimality. Global optimality is guaranteed by reformulating the optimization problem as a mixed-integer linear program (MILP) and solving it with the branch-and-bound method. The presented mixed variable formulation extends the existing mixed variable formulation for size and topology optimization of truss structures. The MILP is obtained by adopting the simultaneous analysis and design approach. The variables consist of binary decision variables to select a profile section from the catalog, and state variables representing the member end forces. The equilibrium equations and member stiffness relations are included as constraints. The displacement and stress constraints are formulated such that for each member limit values are imposed at predefined locations along the member. The proposed method is applied to a three-bay three-story frame.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Civil Engineering, Research group: Metal and Light-wight structures, KU Leuven
Contributors: Van Mellaert, R., Mela, K., Tiainen, T., Heinisuo, M., Lombaert, G., Schevenels, M.
Number of pages: 14
Pages: 3395-3408
Publication date: 2016

Host publication information

Title of host publication: ECCOMAS Congress 2016 - Proceedings of the 7th European Congress on Computational Methods in Applied Sciences and Engineering : Crete; Greece; 5 June 2016 through 10 June 2016
Volume: 2
Publisher: National Technical University of Athens
ISBN (Electronic): 9786188284401
ASJC Scopus subject areas: Artificial Intelligence, Applied Mathematics
Keywords: Discrete optimization, Frame structures, Global optimization, Mixed-integer linear programs, Size optimization
Source: Scopus
Source ID: 84995387507

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A multi-purpose automated vehicular platform with multi-radio connectivity capabilities

Internet access has become commonplace in the modern world. As the number of users and the amount of data traffic in the Internet keep rising exponentially, while the requirements of novel applications are becoming more stringent, there is a clear need for new networking solutions. Therefore, one of the key concepts in resolving the challenges of the upcoming 5G era of communications will be represented by multi-radio heterogeneous networks, where the users can gain benefits by either being connected to multiple different radio technologies simultaneously or seamlessly changing from one network to another based on their needs. In this work, we propose a multi-purpose automated vehicular platform prototype equipped with multiple radio access technologies, which was constructed to demonstrate the potential performance gains provided by the use of multi-radio heterogeneous networks in terms of network throughput, latency, and reliability. We discuss the potential drawbacks of using multiple radio interfaces at the same time. The constructed vehicular platform prototype constitutes a flexible research framework for communications technology within heterogeneous networks and becomes helpful for supporting future use cases of industrial IoT applications.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electronics and Communications Engineering, Brno University of Technology
Contributors: Urama, J., Gerasimenko, M., Stusek, M., Masek, P., Andreev, S., Hosek, J., Koucheryavy, Y.
Number of pages: 7
Pages: 1-7
Publication date: 20 Jul 2018

Host publication information

Title of host publication: 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018
Publisher: IEEE
ISBN (Electronic): 9781538663554
ASJC Scopus subject areas: Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Source: Scopus
Source ID: 85050987115

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A novel stochastic channel modeling approach for mmWave systems with beamforming

The stochastic channel models typically abstract away the details of the paths that carry energy in the radio channel. While these have been universally acceptable for decades due to their ease of use and reasonable accuracy in most practical cases, the appearance of steerable, narrow-beam antennas in mmWave bands makes the exact path information very valuable, primarily for beam tracking algorithms. Currently, only deterministic channel modeling (e.g. ray tracing) provides the required level of details, but at prohibitive computing cost. This limits the study and design environments for such algorithms to the confines of existing ray tracing data, which is bulky and rarely available for free. In this paper, we consider an approach to stochastic channel modeling that allows to achieve the level of details equivalent to ray tracing, but at a fraction of the computing costs. The proposed approach may be immediately applied to any system operating at 20-100 GHz. It allows the researchers and engineers to perform quick testing of elaborate mmWave MAC and PHY algorithms with a system-level simulation, without having to obtain exhaustive measurement or ray tracing data.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Electronics and Communications Engineering, Research group: Emerging Technologies for Nano-Bio-Info-Cogno, Intel Corporation
Contributors: Pyattaev, A., Johnsson, K., Andreev, S., Koucheryavy, Y.
Publication date: 5 Jul 2016

Host publication information

Title of host publication: 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring)
Publisher: IEEE
ISBN (Electronic): 9781509016983
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Applied Mathematics
Keywords: Beamforming, EHF, MIMO, MmWave, Multipath, Stochastic channel model
Source: Scopus
Source ID: 84979729800

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A perceptual quality metric for high-definition stereoscopic 3D video

The use of 3D video is growing in several fields such as entertainment, military simulations, medical applications. However, the process of recording, transmitting, and processing 3D video is prone to errors thus producing artifacts that may affect the perceived quality. Nowadays a challenging task is the definition of a new metric able to predict the perceived quality with low computational complexity in order to be used in real-time applications. The research in this field is very active due to the complexity of the analysis of the influence of stereoscopic cues. In this paper we present a novel stereoscopic metric based on the combination of relevant features able to predict the subjective quality rating in a more accurate way.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: 3D MEDIA, Signal Processing Research Community (SPRC), Universita' degli Studi Roma TRE
Contributors: Battisti, F., Carli, M., Stramacci, A., Boev, A., Gotchev, A.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Publisher: SPIE
Article number: 939916
ISBN (Print): 9781628414899

Publication series

Name: SPIE Conference Proceedings
Volume: 9399
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Quality metric, Stereoscopic 3D video, Video transmission
Electronic versions: 
Source: Scopus
Source ID: 84928485494

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

A Simple Controller with a Reduced Order Internal Model in the Frequency Domain

We use frequency domain methods to study robust output regulation of a stable plant in a situation where the controller is only required to be robust with respect to a predefined class of perturbations. We present a characterization for the solvability of the control problem and design a minimal order controller that achieves robustness with respect to a given class of uncertainties. The construction of the controller is illustrated with an example.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Mathematics, Research group: MAT Mathematical and semantic modelling
Contributors: Laakkonen, A., Paunonen, L.
Number of pages: 5
Pages: 1988-1992
Publication date: 2016

Host publication information

Title of host publication: Proceedings of European Control Conference 2016
Publisher: IEEE
ISBN (Electronic): 978-1-5090-2590-9
ASJC Scopus subject areas: Applied Mathematics

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Benchmarking of several disparity estimation algorithms for light field processing

A number of high-quality depth imaged-based rendering (DIBR) pipelines have been developed to reconstruct a 3D scene from several images taken from known camera viewpoints. Due to the specific limitations of each technique, their output is prone to artifacts. Therefore, the quality cannot be ensured. To improve the quality of the most critical and challenging image areas, an exhaustive comparison is required. In this paper, we consider three questions of benchmarking the quality performance of eight DIBR techniques on light fields: First, how does the density of original input views affect the quality of the rendered novel views? Second, how does disparity range between adjacent input views impact the quality? Third, how does each technique behave for different object properties? We compared and evaluated the results visually as well as quantitatively (PSNR, SSIM, AD, and VDP2). The results show some techniques outperform others in different disparity ranges. The results also indicate using more views not necessarily results in visually higher quality for all critical image areas. Finally, we have shown a comparison for different scene's complexity such as non-Lambertian objects.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Computing Sciences, Moving Picture Technologies
Contributors: Zakeri, F. S., Bätz, M., Jaschke, T., Keinert, J., Chuchvara, A.
Publication date: 2019

Host publication information

Title of host publication: Fourteenth International Conference on Quality Control by Artificial Vision
Publisher: SPIE, IEEE
Editors: Bazeille, S., Verrier, N., Cudel, C.
Article number: 111721C
ISBN (Electronic): 9781510630536

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 11172
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Depth image-based rendering, Disparity estimation, Quality evaluation

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85070208910

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Combining full-reference image visual quality metrics by neural network

A task of assessing full-reference visual quality of images is considered. Correlation between the obtained array of mean opinion scores (MOS) and the corresponding array of given metric values allows characterizing correspondence of a considered metric to HVS. For the largest openly available database TID2013 intended for metric verification, a Spearman correlation is about 0.85 for the best existing HVS-metrics. One simple way to improve an efficiency of assessing visual quality of images is to combine several metrics. Our work addresses a possibility of using neural networks for the aforementioned purpose. As leaning data, we have used metric sets for images of the database TID2013 that are employed as the network inputs. Randomly selected half of 3000 images of the database TID2013 has been used at the learning stage whilst other half have been exploited for assessing quality of neural network based HVS-metric. Six metrics "cover" well all types of distortions: FSIMc, PSNR-HMA, PSNR-HVS, SFF, SR-SIM, and VIF, have been selected. As the result of NN learning, the Spearman correlation between the NN output and the MOS for the verification set of database TID2013 reaches 0.93 for the best configuration of NN. This is considerably better than for any particular metric employed as an input (FSIMc is the best among them). Analysis of the designed metric efficiency is carried out, its advantages and drawbacks are demonstrated.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Signal Processing Research Community (SPRC), National Aerospace University
Contributors: Lukin, V. V., Ponomarenko, N. N., Ieremeiev, O., Egiazarian, K., Astola, J.
Publication date: 2015

Host publication information

Title of host publication: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 9394
Publisher: SPIE
Article number: 93940K
ISBN (Print): 9781628414844
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Full-reference image visual quality assessment, Neural networks
Source: Scopus
Source ID: 84928473490

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Compressive strain measurement using RFID patch antenna sensors

In this research, two radiofrequency identification (RFID) antenna sensor designs are tested for compressive strain measurement. The first design is a passive (battery-free) folded patch antenna sensor with a planar dimension of 61mm × 69mm. The second design is a slotted patch antenna sensor, whose dimension is reduced to 48mm × 44mm by introducing slots on antenna conducting layer to detour surface current path. A three-point bending setup is fabricated to apply compression on a tapered aluminum specimen mounted with an antenna sensor. Mechanics-electromagnetics coupled simulation shows that the antenna resonance frequency shifts when each antenna sensor is under compressive strain. Extensive compression tests are conducted to verify the strain sensing performance of the two sensors. Experimental results confirm that the resonance frequency of each antenna sensor increases in an approximately linear relationship with respect to compressive strain. The compressive strain sensing performance of the two RFID antenna sensors, including strain sensitivity and determination coefficient, is evaluated based on the experimental data.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, Georgia Institute of Technology, School of Electrical and Computer Engineering, Virginia Tech
Contributors: Cho, C., Yi, X., Wang, Y., Tentzeris, M. M., Leon, R. T.
Publication date: 2014

Host publication information

Title of host publication: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2014
Volume: 9061
Publisher: SPIE
Article number: 90610X
ISBN (Print): 9780819499875
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Folded patch antenna, Passive wireless sensor, RFID, Slotted patch antenna, Strain sensor
Source: Scopus
Source ID: 84902151393

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Computational wavelength resolution for in-line lensless holography: Phase-coded diffraction patterns and wavefront group-sparsity

In-line lensless holography is considered with a random phase modulation at the object plane. The forward wavefront propagation is modelled using the Fourier transform with the angular spectrum transfer function. The multiple intensities (holograms) recorded by the sensor are random due to the random phase modulation and noisy with Poissonian noise distribution. It is shown by computational experiments that high-accuracy reconstructions can be achieved with resolution going up to the two thirds of the wavelength. With respect to the sensor pixel size it is a super-resolution with a factor of 32. The algorithm designed for optimal superresolution phase/amplitude reconstruction from Poissonian data is based on the general methodology developed for phase retrieval with a pixel-wise resolution in V. Katkovnik, "Phase retrieval from noisy data based on sparse approximation of object phase and amplitude", http://www.cs.tut.fi/∼lasip/DDT/index3.html.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing, Department of Photonics and Optical Information Technology, ITMO University
Contributors: Katkovnik, V., Shevkunov, I., Petrov, N. V., Egiazarian, K.
Publication date: 2017

Host publication information

Title of host publication: Digital Optical Technologies 2017
Publisher: SPIE
Article number: 1033509
ISBN (Electronic): 9781510611153

Publication series

Name: Proceedings of SPIE
Volume: 10335
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Discrete optical signal processing, Image processing, Noise in imaging systems, Phase retrieval, Superresolution

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85030715279

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Depth map occlusion filling and scene reconstruction using modified exemplar-based inpainting

RGB-D sensors are relatively inexpensive and are commercially available off-the-shelf. However, owing to their low complexity, there are several artifacts that one encounters in the depth map like holes, mis-alignment between the depth and color image and lack of sharp object boundaries in the depth map. Depth map generated by Kinect cameras also contain a significant amount of missing pixels and strong noise, limiting their usability in many computer vision applications. In this paper, we present an efficient hole filling and damaged region restoration method that improves the quality of the depth maps obtained with the Microsoft Kinect device. The proposed approach is based on a modified exemplar-based inpainting and LPA-ICI filtering by exploiting the correlation between color and depth values in local image neighborhoods. As a result, edges of the objects are sharpened and aligned with the objects in the color image. Several examples considered in this paper show the effectiveness of the proposed approach for large holes removal as well as recovery of small regions on several test images of depth maps. We perform a comparative study and show that statistically, the proposed algorithm delivers superior quality results compared to existing algorithms.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI, Signal Processing Research Community (SPRC), Dept. of Radio-Electronics Systems, Don State Technical University
Contributors: Voronin, V. V., Marchuk, V. I., Fisunov, A. V., Tokareva, S. V., Egiazarian, K. O.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Publisher: SPIE
Article number: 93990S
ISBN (Print): 9781628414899

Publication series

Name: SPIE Conference Proceedings
Volume: 9399
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Depth map, Filtering, Image processing, Inpainting, Kinect, Occlusion
Source: Scopus
Source ID: 84928473063

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Design and simulation of a slotted patch antenna sensor for wireless strain sensing

In this work, a slotted patch antenna is employed as a wireless sensor for monitoring structural strain and fatigue crack. Using antenna miniaturization techniques to increase the current path length, the footprint of the slotted patch antenna can be reduced to one quarter of a previously presented folded patch antenna. Electromagnetic simulations show that the antenna resonance frequency varies when the antenna is under strain. The resonance frequency variation can be wirelessly interrogated and recorded by a radiofrequency identification (RFID) reader, and can be used to derive strain/deformation. The slotted patch antenna sensor is entirely passive (battery-free), by exploiting an inexpensive off-the-shelf RFID chip that receives power from the wireless interrogation by the reader.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Sensing Systems for Wireless Medicine (MediSense), Georgia Institute of Technology, Georgia Institute of Technology, School of Electrical and Computer Engineering, Virginia Tech
Contributors: Yi, X., Cho, C., Cook, B., Wang, Y., Tentzeris, M. M., Leon, R. T.
Publication date: 2013

Host publication information

Title of host publication: Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2013
Volume: 8694
Article number: 86941J
ISBN (Print): 9780819494771
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: RFID, Slotted patch antenna, Strain sensor, Wireless passive sensor
Source: Scopus
Source ID: 84878419679

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Dots-on-the-fly electron beam lithography

We demonstrate a novel approach for electron-beam lithography (EBL) of periodic nanostructures. This technique can rapidly produce arrays of various metallic and etched nanostructures with line and pitch dimensions approaching the beam spot size. Our approach is based on often neglected functionality which is inherent in most modern EBL systems. The raster/vector beam exposure system of the EBL software is exploited to produce arrays of pixel-like spots without the need to define coordinates for each spot in the array. Producing large arrays with traditional EBL techniques is cumbersome during pattern design, usually leads to large data files and easily results in system memory overload during patterning. In Dots-on-The-fly (DOTF) patterning, instead of specifying the locations of individual spots, a boundary for the array is given and the spacing between spots within the boundary is specified by the beam step size. A designed pattern element thus becomes a container object, with beam spacing acting as a parameterized location list for an array of spots confined by that container. With the DOTF method, a single pattern element, such as a square, rectangle or circle, can be used to produce a large array containing thousands of spots. In addition to simple arrays of nano-dots, we expand the technique to produce more complex, highly tunable arrays and structures on substrates of silicon, ITO/ FTO coated glass, as well as uncoated fused silica, quartz and sapphire.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Electronics and Communications Engineering, Research group: Wireless Communications and Positioning, Optoelectronics Research Centre, Research group: Nanophotonics
Contributors: Isotalo, T. J., Niemi, T.
Number of pages: 7
Publication date: 2016

Host publication information

Title of host publication: SPIE Proceedings : Alternative Lithographic Technologies VIII
Volume: 9777
Publisher: SPIE
Editor: Bencher, C.
Article number: 97771E
ISBN (Electronic): 9781510600126

Publication series

Name: Proceedings of SPIE
Publisher: SPIE
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: electron beam lithography, nano-fabrication, nano-particle arrays, optoelectronics, periodic nano-structures, plasmonics
Source: Scopus
Source ID: 84981516864

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Dynamic laser speckle metrology with binarization of speckle patterns

Dynamic laser speckle analysis is non-destructive detection of physical or biological activity through statistical processing of speckle patterns on the surface of diffusely reflecting objects. This method is sensitive to microscopic changes of the surface over time and needs simple optical means. Advances in computers and 2D optical sensors forced development of pointwise algorithms. They rely on acquisition of a temporal sequence of correlated speckle images and generate activity data as a 2D spatial contour map of the estimate of a given statistical parameter. The most widely used pointwise estimates are the intensity-based estimates which compose each map entry from a time sequence of intensity values taken at one and the same pixel in the acquired speckle images. Accuracy of the pointwise approach is strongly affected by the signal-dependent nature of the speckle data when the spread of intensity fluctuations depends on the intensity itself. The latter leads to erroneous activity determination at non-uniform distribution of intensity in the laser beam for the non-normalized estimates. Normalization of the estimates, introduces errors. We propose to apply binarization to the acquired speckle images by comparing the intensity values in the temporal sequence for a given spatial point to the mean intensity value estimated for this point and to evaluate a polar correlation function. Efficiency of this new processing algorithm is checked both by simulation and experiment.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing, Research group: 3D MEDIA, Bulgarian Academy of Sciences
Contributors: Stoykova, E., Nazarova, D., Berberova, N., Gotchev, A., Ivanov, B., Mateev, G.
Publication date: 2017

Host publication information

Title of host publication: 19th International Conference and School on Quantum Electronics: Laser Physics and Applications
Publisher: SPIE
Article number: 102260R
ISBN (Electronic): 9781510609532

Publication series

Name: Proceedings of SPIE
Volume: 10226
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Binary patterns, Dynamic speckle, Intensity-based algorithms, Optical metrology, Pointwise processing

Bibliographical note

JUFOID=71479

Source: Scopus
Source ID: 85017345812

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Effects of structure on spontaneous activity in simulated neuronal networks

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, BioMediTech, Research group: Computational Neuro Science-CNS, Faculty of Biomedical Sciences and Engineering, Department of Mathematics, Research group: Computational Neuro Science-CNS
Contributors: Mäki-Marttunen, T., Acimovic, J., Ruohonen, K., Linne, M.
Publication date: 11 Apr 2011

Host publication information

Title of host publication: Proceedings of Mathematical Neuroscience (ICMS 2011), April 11-13, 2011, Edinburgh, Scotland
ASJC Scopus subject areas: Cellular and Molecular Neuroscience, Neuroscience (miscellaneous), Applied Mathematics, Signal Processing

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Engineering motif search for large graphs

In the graph motif problem, we are given as input a vertexcolored graph H (the host graph) and a multiset of colors M (the motif). Our task is to decide whether H has a connected set of vertices whose multiset of colors agrees with M. The graph motif problem is NP-complete but known to admit parameterized algorithms that run in linear time in the size of H. We demonstrate that algorithms based on constrained multilinear sieving are viable in practice, scaling to graphs with hundreds of millions of edges as long as M remains small. Furthermore, our implementation is topologyinvariant relative to the host graph H, meaning only the most crude graph parameters (number of edges and number of vertices) suffice in practice to determine the algorithm performance.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Mathematics, Aalto University, Lunds Universitet / Lunds Tekniska Högskola, Lund Univ, Lund University, University of Calgary, Institute for Biocomplexity and Informatics, Canada, Medical University of Warsaw, Helsinki Institute for Information Technology HIIT, Department of Computer Science and Information Systems
Contributors: Björklund, A., Kaski, P., Kowalik, Ł., Lauri, J.
Number of pages: 15
Pages: 104-118
Publication date: 2015

Host publication information

Title of host publication: 2015 Proceedings of the Seventeenth Workshop on Algorithm Engineering and Experiments (ALENEX)
ISBN (Electronic): 978-1-61197-375-4

Publication series

Name: Workshop on Algorithm Engineering and Experiments
ISSN (Print): 2164-0300
ASJC Scopus subject areas: Engineering(all), Applied Mathematics
Source: Scopus
Source ID: 84937777832

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Ergodic Capacity Analysis of Wireless Transmission over Generalized Multipath/Shadowing Channels

Novel composite fading models were recently proposed based on inverse gamma distributed shadowing conditions. These models were extensively shown to provide remarkable modeling of the simultaneous occurrence of multipath fading and shadowing phenomena in emerging wireless scenarios such as cellular, off-body and vehicle-to-vehicle communications. Furthermore, the algebraic representation of these models is rather tractable, which renders them convenient to handle both analytically and numerically. Based on this, the present contribution analyzes the ergodic capacity over the recently proposed κ-μ inverse gamma composite fading channels, which were shown to characterize excellently multipath fading and shadowing in line-of-sight communication scenarios, including realistic vehicular communications. Novel analytic expressions are derived which are subsequently used in the analysis of the corresponding system performance. In this context, the offered results are compared with respective results from cases assuming conventional fading conditions, which leads to the development of numerous insights on the effect of the multipath fading and shadowing severity on the achieved capacity levels. It is expected that these results will be useful in the design of timely and demanding wireless technologies such as wearable, cellular and inter-vehicular communications.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Wireless Communications and Positioning, Electronics and Communications Engineering, Department of Electrical and Computer Engineering, Khalifa University, Queen's University, Belfast, Northern Ireland, University of Surrey, Aristotle University of Thessaloniki
Contributors: Sofotasios, P. C., Yoo, S. K., Muhaidat, S., Cotton, S. L., Matthaiou, M., Valkama, M., Karagiannidis, G. K.
Number of pages: 5
Pages: 1-5
Publication date: 20 Jul 2018

Host publication information

Title of host publication: 2018 IEEE 87th Vehicular Technology Conference
Publisher: IEEE
ISBN (Electronic): 9781538663554
ASJC Scopus subject areas: Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Source: Scopus
Source ID: 85050971918

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Exploiting local class information in extreme learning machine

In this paper we propose an algorithm for Single-hidden Layer Feedforward Neural networks training. Based on the observation that the learning process of such networks can be considered to be a non-linear mapping of the training data to a high-dimensional feature space, followed by a data projection process to a low-dimensional space where classification is performed by a linear classifier, we extend the Extreme Learning Machine (ELM) algorithm in order to exploit the local class information in its optimization process. The proposed Local Class Variance Extreme Learning Machine classifier is evaluated in facial image classification problems, where we compare its performance with that of other ELM-based classifiers. Experimental results show that the incorporation of local class information in the ELM optimization process enhances classification performance.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research Community on Data-to-Decision (D2D), Aristotle University of Thessaloniki, Department of Informatics
Contributors: Iosifidis, A., Tefas, A., Pitas, I.
Number of pages: 7
Pages: 49-55
Publication date: 2014

Host publication information

Title of host publication: NCTA 2014 - Proceedings of the International Conference on Neural Computation Theory and Applications
Publisher: INSTICC PRESS
ISBN (Print): 9789897580543
ASJC Scopus subject areas: Computational Theory and Mathematics, Applied Mathematics
Keywords: Extreme learning machine, Facial image analysis, Single-hidden layer feedforward neural networks
Source: Scopus
Source ID: 84908870373

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Fabrication and characterization of broadband superluminescent diodes for 2 μm wavelength

Single-mode superluminescent diodes operating at 2 μm wavelength are reported. The structures are based on GaSb material systems and were fabricated by molecular beam epitaxy. Several waveguide designs have been implemented. A continuous-wave output power higher than 35 mW is demonstrated for a spectrum centered at around 1.92 μm. We show that the maximum output power of the devices is strongly linked to spectrum width. Device having low output power exhibit a wide spectrum with a full-width half-maximum (FWHM) as large as 209 nm, while devices with highest output power exhibit a narrower spectrum with about 61 nm FWHM.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications
Contributors: Zia, N., Viheriälä, J., Koskinen, R., Koskinen, M., Suomalainen, S., Guina, M.
Publication date: 2016

Host publication information

Title of host publication: Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XX
Publisher: SPIE
Article number: 97680Q
ISBN (Electronic): 9781510600034

Publication series

Name: Proceedings of SPIE
Volume: 9768
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Gallium antimonide, SLD design, Superluminescent diodes, Tilt waveguide

Bibliographical note

INT=orc,"Koskinen, Mervi"

Source: Scopus
Source ID: 84978727362

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

We report on green (550-560 nm) electroluminescence (EL) from (Al<inf>0.5</inf>Ga<inf>0.5</inf>)<inf>0.5</inf>In<inf>0.5</inf>P-(Al<inf>0.8</inf>Ga<inf>0.2</inf>)<inf>0.5</inf>In<inf>0.5</inf>P double p-i-n heterostructures with monolayer-scale tensile strained GaP insertions in the cladding layers and light-emitting diodes (LEDs) based thereupon. The structures are grown side-by-side on high-index and (100) GaAs substrates by molecular beam epitaxy. Cross-sectional transmission electron microscopy studies indicate that GaP insertions are flat, thus the GaP-barrier substrate orientation-dependent heights should match the predictions of the flat model. At moderate current densities (∼500 A/cm<sup>2</sup>) the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)-grown strictures, the EL spectra of (211) and (311)-grown devices are shifted towards shorter wavelengths (∼550 nm at room temperature). At high current densities (>1 kA/cm<sup>2</sup>) a much higher EL intensity is achieved for the devices grown on high-index substrates. The integrated intensity of (311)-grown structures gradually saturates at current densities above 4 kA/cm<sup>2</sup>, whereas no saturation is revealed for (211)-grown structures up to the current densities above 14 kA/cm<sup>2</sup>. We attribute the effect to the surface orientation-dependent engineering of the GaP band structure which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p- doped (Al<inf>0.8</inf>Ga<inf>0.2</inf>)<inf>0.5</inf>In<inf>0.5</inf>P cladding layers.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Ultrafast and intense lasers, Frontier Photonics, Technische Universität Berlin, Fakultät VII-Wirtschaft und Management, 25.6.2012, VI Systems GmbH, CEMES-CNRS, A. F. Ioffe Physical Technical Institute, Institut Für Festkörperphysik
Contributors: Ledentsov, N. N., Shchukin, V. A., Lyytikäinen, J., Okhotnikov, O., Cherkashin, N. A., Shernyakov, Y. M., Payusov, A. S., Gordeev, N. Y., Maximov, M. V., Schlichting, S., Nippert, F., Hoffmann, A.
Publication date: 2015

Host publication information

Title of host publication: Proceedings of SPIE : Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIX
Volume: 9383
Publisher: SPIE
Article number: 93830E
ISBN (Print): 9781628414738
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: high-index surface, light-emitting diode, tensile strained barrier
Source: Scopus
Source ID: 84930074847

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

>8W GaInNAs VECSEL emitting at 615 nm

We report a high-power VECSEL emitting <8W around 615 nm. The gain chip of the laser was grown by plasmaassisted molecular beam epitaxy and it comprised 10 GaInNAs quantum wells. The VECSEL cavity had a V-shaped geometry and a 10-mm-long non-critically phase-matched LBO crystal for second harmonic generation. The cavity incorporated also an etalon and a birefringent filter for controlling the output wavelength. With the aid of the secondharmonic output and the infrared light leaking out from the laser cavity, the single-pass conversion efficiency of the crystal was estimated to have a value of 0.75%.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Frontier Photonics
Contributors: Leinonen, T., Penttinen, J. P., Korpijärvi, V. M., Kantola, E., Guina, M.
Publication date: 2015

Host publication information

Title of host publication: Proceedings of SPIE : Vertical External Cavity Surface Emitting Lasers (VECSELs) V
Volume: 9349
Publisher: SPIE
Article number: 934909
ISBN (Print): 9781628414394
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: frequency doubling, high power visible laser, OPSL, orange-red VECSEL, SDL, SHG
Source: Scopus
Source ID: 84925597620

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Highly-efficient Ho:KY(WO4)2 thin-disk lasers at 2.06 μm

The recent advances in the development of Holmium monoclinic double tungstate thin-disk lasers are reviewed. The thin-disk is based on a 250-μm-thick 3 at. % Ho:KY(WO4)2 active layer grown on a (010)-oriented KY(WO4)2 substrate. When pumped by a Tm-fiber laser at 1960 nm with a single-bounce pump geometry, the continuous-wave Ho:KY(WO4)2 thin-disk laser generates an output power of 1.01 W at 2057 nm corresponding to a slope efficiency η of 60% and a laser threshold of only 0.15 W. The thin-disk laser is passively Q-switched with a GaSb-based quantum-well semiconductor saturable absorber mirror. In this regime, it generates an average output power of 0.551 W at ∼2056 nm with η = 44%. The best pulse characteristics are 4.1 μJ/201 ns at a repetition rate of 135 kHz. The laser performance, beam quality and thermo-optic aberrations of such lasers are strongly affected by the Ho3+ doping concentration. For the 3 at.% Ho3+-doped thin-disk, the thermal lens is negative (the sensitivity factors for the two principal meridional planes are-1.7 and-0.6 m-1/W) and astigmatic. The Ho:KY(WO4)2 epitaxial structures are promising as active elements in mode-locked thin-disk lasers at ∼2060 nm.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Research group: ORC, Max Born Institute, Universitat Rovira i Virgili, LISA Laser Products OHG, ITMO University, Institute of Laser Physics of the Siberian Branch of the RAS
Contributors: Mateos, X., Loiko, P., Lamrini, S., Scholle, K., Fuhrberg, P., Suomalainen, S., Härkönen, A., Guina, M., Vatnik, S., Vedin, I., Aguiló, M., Diáz, F., Wang, Y., Griebner, U., Petrov, V.
Publication date: 2018

Host publication information

Title of host publication: Pacific-Rim Laser Damage 2018 : Optical Materials for High-Power Lasers
Publisher: SPIE, IEEE
Article number: 107130J
ISBN (Electronic): 9781510619920

Publication series

Name: Proceedings of SPIE
Volume: 10713
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: 2-micron lasers, Ho-lasers, monoclinic double tungstates, Q-switched lasers, thin-disk lasers

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85051249536

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

High-performance programs by source-level merging of RVC-CAL dataflow actors

RVC-CAL is a dataflow language that has acquired an ecosystem of sophisticated design tools. Previous works have shown that RVC-CAL-based applications can automatically be deployed to multiprocessor platforms, as well as hardware descriptions with high efficiency. However, as RVC-CAL is a concurrent language, code generation for a single processor core requires careful application analysis and scheduling. Although much work has been done in this area, to this date no publication has reported that programs generated from RVC-CAL could rival handwritten programs on single-core processors. This paper proposes performance optimization of RVCCAL applications by actor merging at source code level. The proposed methodology is demonstrated with an IEEE 802.15.4 (ZigBee) transmitter case study. The transmitter baseband software, previously written in C, is rewritten in RVC-CAL and optimized with the proposed methodology. Experiments show that on a VLIW-flavored processor the RVC-CAL-based program achieves the performance of manually written software.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing Research Community (SPRC), Dept. of Computer Science and Engineering, Univ of Oulu, Abo Akad Univ, Abo Akademi University, Dept Phys
Contributors: Boutellier, J., Ghazi, A., Silvén, O., Ersfolk, J.
Number of pages: 6
Pages: 360-365
Publication date: 2013

Host publication information

Title of host publication: 2013 IEEE Workshop on Signal Processing Systems, SiPS 2013
Publisher: Institute of Electrical and Electronics Engineers Inc.
Article number: 6674533
ISBN (Print): 9781467362382
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics, Hardware and Architecture
Keywords: Dataflow computing, Design automation, Signal processing
Source: Scopus
Source ID: 84896457580

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

High-power 1550 nm tapered DBR lasers fabricated using soft UV-nanoimprint lithography

Paper reports the DBR-RWG surface grating design, the fabrication process, and the output characteristics of tapered DBR laser diodes for the applications, like for example LIDAR and range finding, that require eye-safe high-power single-mode coherent light sources. The fabricated regrowth-free DBR AlGaInAs/InP lasers exhibited a CW output power as high as 560 mW in single-mode operation at room temperature. At maximum output power the SMSR was 38 dB, proving the excellent behavior of the surface gratings. The tapered section enabled scaling the maximum CW power at room temperature from 125 mW to 560 mW, by increasing its length from 0.5 mm to 4.0 mm. The paper discusses the limitations and performance variation associated to the power scaling by using the tapered section length as a scaling parameter.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Nanophotonics, Research group: Semiconductor Technology and Applications, Materials Research Laboratory, Turun Yliopisto/Turun Biomateriaalikeskus
Contributors: Viheriälä, J., Aho, A. T., Mäkelä, J., Salmi, J., Virtanen, H., Leinonen, T., Dumitrescu, M., Guina, M.
Number of pages: 7
Publication date: 2016

Host publication information

Title of host publication: High-Power Diode Laser Technology and Applications XIV
Publisher: SPIE
Article number: 97330Q
ISBN (Electronic): 9781628419689

Publication series

Name: SPIE Conference Proceedings
Publisher: SPIE
Volume: 9733
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: 1550 nm laser diode, DBR, Power scaling, Tapered laser diode

Bibliographical note

INT=orc,"Aho, Antti T."
JUFOID=71479

Source: Scopus
Source ID: 84978785955

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Hot pen and laser writable photonic polymer films

An orange-reflecting photonic polymer film has been fabricated based on a hydrogen-bonded cholesteric liquid crystalline (CLC) polymer consisting of non-reactive (R)-(+)-3-methyladipic acid as the chiral dopant. This polymer film can be patterned easily by evaporating the chiral dopant at specific locations with a hot pen or a laser beam. Removal of chiral dopant leads to a decrease in the helical pitch at the heat treated areas leading to a change in color from orange to green revealing a high contrast pattern. The photonic patterns are irreversible and stable at ambient conditions. This makes such a CLC polymer film interesting as writable photonic paper.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Eindhoven University of Technology
Contributors: Moirangthem, M., Stumpel, J. E., Alp, B., Teunissen, P., Bastiaansen, C. W. M., Schenning, A. P. H. J.
Publication date: 2016

Host publication information

Title of host publication: Emerging Liquid Crystal Technologies XI
Volume: 9769
Publisher: SPIE
Article number: 97690Y
ISBN (Electronic): 9781510600041
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: Cholesteric liquid crystals, laser writing, patterned surface, photonic paper, thermal writing
Source: Scopus
Source ID: 84982292427

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Independent Loops Search in Flow Networks Aiming for Well-Conditioned System of Equations

We approach the problem of choosing linearly independent loops in a pipeflow network as choosing the best-conditioned submatrix of a given larger matrix. We present some existing results of graph theory and submatrix selection problems, based on which we construct three heuristic algorithms for choosing the loops. The heuristics are tested on two pipeflow networks that differ significantly on the distribution of pipes and nodes in the network.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Mathematics, Research group: Computer Science and Applied Logics, Research group: Positioning, Research group: MAT Intelligent Information Systems Laboratory, Tekes
Contributors: Humaloja, J., Ali-Löytty, S., Pohjolainen, S., Hämäläinen, T.
Publication date: 2017

Host publication information

Title of host publication: Progress in Industrial Mathematics at ECMI 2016
Publisher: Springer International Publishing
Editors: Quintela, P., Barral, P., Gómez, D., Pena, F. J., Rodríguez, J., Salgado, P., Vázquez-Mendéz, M. E.
ISBN (Print): 978-3-319-63081-6
ISBN (Electronic): 978-3-319-63082-3

Publication series

Name: Mathematics in industry
Publisher: Springer
Volume: 26
ISSN (Print): 1612-3956
ISSN (Electronic): 2198-3283
ASJC Scopus subject areas: Applied Mathematics, Modelling and Simulation
Keywords: pipeflow analysis, independent loops
Electronic versions: 
  • ecmi16. Embargo ended: 4/12/18

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

In silico study on structure and dynamics in bursting neuronal networks

In vitro cell cultures have been widely used as a model system for studying neuronal development and electroresponsiveness in the absence of in vivo regulation. These networks are characterized by population bursts that vary largely in both frequency and shape (Wagenaar et al., BMC Neurosci. 2000). In this work we study the interplay of structure and activity in simulated spontaneously bursting networks. The computational approach is useful due to the difficulty of gaining enough control on the structure in in vitro experiments, although promising attempts are being made in cultured neuronal networks (Wheeler, Proc. IEEE 2010). Recently, the effect of network structure on activity has been analyzed through, e.g., the degree distribution width (Roxin, Front. Comp. Neurosci. 2011) and occurrence of second-order connections (Zhao et al. 2011, Front. Comp. Neurosci. 2011). In the present work we apply a set of graph measures to a wide set of different networks in order to determine which of the structural measures are relevant in the prediction of the bursting network activity. The network activity is quantified using standard measures such as number of bursts and burst duration.
We use two neuron models that are applicable to small (N=100) spontaneously bursting networks, namely, an integrate-and-fire model with short-term plasticity (Tsodyks et al., J. Neurosci. 2000) and a more detailed point-neuron model with four ionic and three synaptic currents (Golomb et al., J. Neurophysiol. 2006). We show that when the in-degree is sharp (binomial), the network activity is best predicted by using the clustering coefficient of the underlying graph. By contrast, when a broad in-degree is used (power-law), the maximum eigenvalue of the connectivity matrix becomes dominant in predicting the network activity. The results are consistent across the two neuron models. In our work the neurons are identical by their features, and no input is applied to the network, and hence all statistical difference between the compared networks is caused by the network structure and the network structure only.
The obtained results shed light on the relevance of different aspects of structure. In in vivo applications the full connectome is rarely accessible, but estimates of certain structural measures may be assessed indirectly (Vlachos et al., PLoS Comp. Biol. 2012). Extracting the structure-function relationship in neuronal networks may have implication on both the way experiments are conducted and on how biologically inspired artificial intelligence will be designed in the future.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Faculty of Biomedical Sciences and Engineering, Research group: Computational Neuro Science-CNS, Department of Signal Processing, Research group: Computational Neuro Science-CNS
Contributors: Mäki-Marttunen, T. M., Acimovic, J., Ruohonen, K. P., Linne, M.
Number of pages: 1
Publication date: 13 Oct 2012

Host publication information

Title of host publication: Neuroscience 2012; 42nd Annual Meeting, New Orleans, USA, October 14-18, 2012
Publisher: Society for Neuroscience (SfN)
Article number: 300.26/DDD70

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Integrated multi-wavelength mid-IR light source for gas sensing

Cost effective multi-wavelength light sources are key enablers for spectroscopic applications at Mid-IR wavelength range. Utilizing a novel Mid-IR Si-based photonic integrated circuit filter and wide-band Mid-IR SLEDs, we show the concept of a light source that covers 2.7.3.5 μm wavelength range with a resolution <1nm. The spectral bands are switchable and tunable and they can be modulated. The source allows for the fabrication of an affordable multi-band gas sensor with good selectivity and sensitivity. The unit price can be lowered in high volumes by utilizing tailored molded IR lens technology and automated packaging and assembling technologies. The status of the development of the key components of the light source are reported. The Mid-IR PIC is based on the use of thick-SOI technology, SLED is based on AlGaInAsSb materials and the lenses are tailored single crystal, nonoxide glass and heavy metal oxide glasses fabricated by the use of hot-embossing. The packaging concept utilizing automated assembly tools are depicted. In safety and security applications, the Mid-IR wavelength range covered by the source allows for the detection of several harmful gas components with a single sensor. At the moment, affordable sources are not available. The market impact is expected to be disruptive, since the devices currently in the market are either complicated, expensive and heavy instruments, or the applied measurement principles are inadequate in terms of stability and selectivity.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Photonics, Research group: ORC, VTT Technical Research Centre of Finland, Institute of Electronic Materials Technology, Vaisala Oyj, Airoptic Sp. z o.o., GasSecure, VIGO System S.A.
Contributors: Karioja, P., Alajoki, T., Cherchi, M., Ollila, J., Harjanne, M., Heinilehto, N., Suomalainen, S., Zia, N., Tuorila, H., Viheriälä, J., Guina, M., Buczynski, R., Kasztelanic, R., Salo, T., Virtanen, S., Kluczynski, P., Borgen, L., Ratajczyk, M., Kalinowski, P.
Publication date: 2018

Host publication information

Title of host publication: Next-Generation Spectroscopic Technologies XI
Publisher: SPIE, IEEE
Article number: 106570A
ISBN (Electronic): 9781510618251

Publication series

Name: SPIE Conference Proceedings
Volume: 10657
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: gas sensing, Mid-IR integrated optics, Mid-IR lens, photonics packaging, PIC, Si photonics, SLED

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85050701514

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Integrating III-V, Si, and polymer waveguides for optical interconnects: RAPIDO

We present a vision for the hybrid integration of advanced transceivers at 1.3 μm wavelength, and the progress done towards this vision in the EU-funded RAPIDO project. The final goal of the project is to make five demonstrators that show the feasibility of the proposed concepts to make optical interconnects and packet-switched optical networks that are scalable to Pb/s systems in data centers and high performance computing. Simplest transceivers are to be made by combining directly modulated InP VCSELs with 12 μm SOI multiplexers to launch, for example, 200 Gbps data into a single polymer waveguide with 4 channels to connect processors on a single line card. For more advanced transceivers we develop novel dilute nitride amplifiers and modulators that are expected to be more power-efficient and temperatureinsensitive than InP devices. These edge-emitting III-V chips are flip-chip bonded on 3 μm SOI chips that also have polarization and temperature independent multiplexers and low-loss coupling to the 12 μm SOI interposers, enabling to launch up to 640 Gbps data into a standard single mode (SM) fiber. In this paper we present a number of experimental results, including low-loss multiplexers on SOI, zero-birefringence Si waveguides, micron-scale mirrors and bends with 0.1 dB loss, direct modulation of VCSELs up to 40 Gbps, ±0.25μm length control for dilute nitride SOA, strong band edge shifts in dilute nitride EAMs and SM polymer waveguides with 0.4 dB/cm loss.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, VTT Technical Research Centre of Finland, IBM Research, Vertilas GmbH, Scuola Superiore sant'Anna, Tyndall National Institute at National University of Ireland, Cork, Modulight Inc.
Contributors: Aalto, T., Harjanne, M., Offrein, B. J., Caër, C., Neumeyr, C., Malacarne, A., Guina, M., Sheehan, R. N., Peters, F. H., Melanen, P.
Publication date: 2016

Host publication information

Title of host publication: Optical Interconnects XVI
Publisher: SPIE
Article number: 97530D
ISBN (Print): 9781628419887

Publication series

Name: Proceedings of SPIE
Volume: 9753
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: electro absorption modulator, hybrid integration, optical interconnect, optical interposer, optoelectronics, polymer photonics, semiconductor optical amplifier, Silicon photonics, VCSEL, wavelength multiplexers

Bibliographical note

EXT="Melanen, Petri"

Source: Scopus
Source ID: 84975114015

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Labyrinth based left-handed metamaterials and sub-wavelength focusing of electromagnetic waves

We propose and demonstrate a resonant structure that solves two major problems related to the split-ring resonator structure. These major problems may be stated as the bianisotropy and electric coupling to the magnetic resonance. These two problems introduce difficulties in obtaining isotropic left-handed metamaterial mediums. The resonant structure that we propose here solves both of these problems. We further show that in addition to the magnetic resonance, when combined with a suitable wire medium, the structure that we propose exhibits left-handed transmission band. We further demonstrate the sub-wavelength focusing of electromagnetic waves by use of a two dimensional labyrinth based metamaterial. Our experimental results showed that it is possible to focus the source field with half widths as small as λ/4 by using the labyrinth based metamaterial.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Bilkent University
Contributors: Ozbay, E., Bulu, I., Caglayan, H.
Publication date: 2006

Host publication information

Title of host publication: Photonic Crystal Materials and Devices IV
Volume: 6128
Article number: 612813
ISBN (Print): 0819461709, 9780819461704

Publication series

Name: Proceedings of SPIE
Publisher: SPIE
Volume: 6128
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Left-handed medium, Magnetic Resonance, Metamaterial, Split-ring Resonator, Sub-wavelength Focusing

Bibliographical note

EXT="Caglayan, Humeyra"

Source: Scopus
Source ID: 33745626124

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Machine learning for adaptive bilateral filtering

We describe a supervised learning procedure for estimating the relation between a set of local image features and the local optimal parameters of an adaptive bilateral filter. A set of two entropy-based features is used to represent the properties of the image at a local scale. Experimental results show that our entropy-based adaptive bilateral filter outperforms other extensions of the bilateral filter where parameter tuning is based on empirical rules. Beyond bilateral filter, our learning procedure represents a general framework that can be used to develop a wide class of adaptive filters.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI, Signal Processing Research Community (SPRC), NVIDIA
Contributors: Frosio, I., Egiazarian, K., Pulli, K.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Volume: 9399
Publisher: SPIE
Article number: 939908
ISBN (Print): 9781628414899

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Publisher: The International Society for Optical Engineering
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Adaptive bilateral filter, Denoising, Machine learning, Optimization, Training
Source: Scopus
Source ID: 84928485491

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Measuring bend losses in large-mode-area fibers

We investigate the measurement of bend losses in few-mode large-mode-area (LMA) fibers. The influence of the light source spectral characteristics, modal power content and cladding light on the measurement accuracy and precision is studied experimentally. Monte-Carlo simulations are performed to understand the distribution of the variations. This study provides practical guidelines for bend loss measurements.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, nLIGHT Corporation
Contributors: Ye, C., Koponen, J., Aallos, V., Kokki, T., Petit, L., Kimmelma, O.
Publication date: 2015

Host publication information

Title of host publication: Fiber Lasers XII: Technology, Systems, and Applications
Volume: 9344
Publisher: SPIE
Article number: 934425
ISBN (Electronic): 9781628414349
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Bend loss, Few-mode, Fiber amplifiers, Fiber lasers, Large-mode-area fiber, Silica optical fiber
Source: Scopus
Source ID: 84931311791

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

MECSELs with direct emission in the 760 nm to 810 nm spectral range: A single- and double-side pumping comparison and high-power continuous-wave operation

We compared single-side pumping (SSP) and double-side pumping (DSP) of a semiconductor membrane external-cavity surface-emitting laser (MECSEL). The MECSEL's active region was based on a 4×3 AlGaAs quantum well (QW) structure. This structure was embedded between two silicon carbide (SiC) wafer pieces that were used as transparent intra-cavity (IC) heat spreaders creating a symmetrical cooling environment. The MECSEL structure targeted emission at 780nm and was operated at 20°C heat sink temperature. Via DSP the differential efficiency was improved from 31.9% to 34.4 %. The laser threshold was reduced from 0.79 W to 0.69 W of absorbed pump power while the maximum output power was increased from 3.13 W to 3.22 W. The DSP configuration enabled these improvements by a reduced thermal resistance of the gain element by 9 %. The MECSEL operated at a fundamental Gaussian TEM00 mode profile and the beam quality was measured to be M2 <1.09. We further demonstrate a maximum tuning range from 767 nm to 811 nm. A similar active region with about half the thickness (2×3 AlGaAs QWs) was investigated using the DSP configuration and first results are presented here. 500-μm-thick sapphire IC heat spreaders were used instead of SiC. The output power exceeded 0.5W and the emission was spectrally located around 770 nm.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics
Contributors: Kahle, H., Penttinen, J. P., Phung, H. M., Rajala, P., Tukiainen, A., Ranta, S., Guina, M.
Publication date: 2019

Host publication information

Title of host publication: Vertical External Cavity Surface Emitting Lasers (VECSELs) IX
Publisher: SPIE, IEEE
Editor: Keller, U.
Article number: 109010D
ISBN (Electronic): 9781510624443

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10901
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: AlGaAs, DBR-free, MECSEL, Near infra-red, Thermal management, Thermal resistance, VECSEL

Bibliographical note

INT=phys,"Rajala, Patrik"
jufoid=71479

Source: Scopus
Source ID: 85066635597

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Mode coupling in few-mode large-mode-area fibers

We present an experimental study on mode coupling characteristics of few-mode large-mode-area (LMA) fibers, which are widely used in high power fiber lasers. The modal power allocation is measured by modal decomposition of the nearfield intensity profile of the output beam. Cut-back measurements are carried out with commonly-used fibers with different fiber geometries. The evolution of the modal power content due to mode coupling is presented. The influence of the fiber geometry on mode coupling is discussed.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, nLIGHT Corporation
Contributors: Ye, C., Koponen, J., Aallos, V., Petit, L., Kimmelma, O., Kokki, T.
Publication date: 2014

Host publication information

Title of host publication: Fiber Lasers XI: Technology, Systems, and Applications
Volume: 8961
Publisher: SPIE
Article number: 89612W
ISBN (Print): 9780819498748
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Beam quality, Few-mode, Large-mode-area fiber, Mode coupling, Mode decomposition, Silica optical fiber
Source: Scopus
Source ID: 84900835091

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Model-based dynamic scheduling for multicore implementation of image processing systems

In this paper, we present a new software tool, called HTGS Model-based Engine (HMBE), for the design and implementation of multicore signal processing applications. HMBE provides complementary capabilities to HTGS (Hybrid Task Graph Scheduler), which is a recently-introduced software tool for implementing scalable workflows for high performance computing applications. HMBE integrates advanced design optimization techniques provided in HTGS with model-based approaches that are founded on dataflow principles. Such integration contributes to (a) making the application of HTGS more systematic and less time consuming, (b) incorporating additional dataflow-based optimization capabilities with HTGS optimizations, and (c) automating significant parts of the HTGS-based design process. In this paper, we present HMBE with an emphasis on novel dynamic scheduling techniques that are developed as part of the tool. We demonstrate the utility of HMBE through a case study involving an image stitching application for large scale microscopy images.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Pervasive Computing, University of Maryland, National Institute of Standards and Technology
Contributors: Wu, J., Blattner, T., Keyrouz, W., Bhattacharyya, S. S.
Publication date: 14 Nov 2017

Host publication information

Title of host publication: 2017 IEEE International Workshop on Signal Processing Systems, SiPS 2017
Publisher: IEEE
Article number: 8110003
ISBN (Electronic): 9781538604465
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics, Hardware and Architecture
Source: Scopus
Source ID: 85040564128

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Models of architecture: Reproducible efficiency evaluation for signal processing systems

The current trend in high performance and embedded signal processing consists of designing increasingly complex heterogeneous hardware architectures with non-uniform communication resources. In order to take hardware and software design decisions, early evaluations of the system non-functional properties are needed. These evaluations of system efficiency require high-level information on both the algorithms and the architecture. In this paper, we define the notion of Model of Architecture (MoA) and study the combination of a Model of Computation (MoC) and an MoA to provide a design space exploration environment for the study of the algorithmic and architectural choices. A cost is computed from the mapping of an application, represented by a model conforming a MoC onto an architecture represented by a model conforming an MoA. The cost is composed of a processing-related part and a communicationrelated part. It is an abstract scalar value to be minimized and can represent any non-functional requirement of a system such as memory, energy, throughput or latency.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Pervasive Computing, Research area: Computer engineering, Institut Pascal, UBL, Scuola Superiore sant'Anna, Salzburg University of Applied Sciences, University of Maryland
Contributors: Pelcat, M., Desnos, K., Maggiani, L., Liu, Y., Heulot, J., Nezan, J. F., Bhattacharyya, S. S.
Number of pages: 6
Pages: 121-126
Publication date: 9 Dec 2016

Host publication information

Title of host publication: IEEE International Workshop on Signal Processing Systems, SiPS 2016
Publisher: IEEE
Article number: 7780083
ISBN (Electronic): 9781509033614

Publication series

Name: IEEE International Workshop on Signal Processing Systems
ISSN (Electronic): 2374-7390
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics, Hardware and Architecture
Source: Scopus
Source ID: 85013141986

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Monolithic GaInNAsSb/GaAs VECSEL emitting at 1550 nm

We report the first monolithic GaAs-based vertical external-cavity surface-emitting laser (VECSEL) operating at 1550 nm. The VECSEL is based on a gain mirror which was grown by plasma-assisted molecular beam epitaxy and comprises 8 GaInNAsSb/GaAs quantum wells and an AlAs/GaAs distributed Bragg reflector. When pumped by an 808 nm diode laser, the laser exhibited an output power of 80 mW for a mount temperature of 16 °C.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, Research group: Semiconductor Technology and Applications, Frontier Photonics
Contributors: Korpijärvi, V., Kantola, E. L., Leinonen, T., Guina, M.
Publication date: 2015

Host publication information

Title of host publication: SPIE conference proceedings
Volume: 9349
Publisher: SPIE
Article number: 93490D
ISBN (Print): 9781628414394
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: dilute nitride, diode-pumped lasers, GaInNAsSb, semiconductor disk lasers, Semiconductor lasers, vertical external cavity surface emitting lasers
Source: Scopus
Source ID: 84925652903

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Multi-carrier CDMA for network assisted device-to-device communications for an integrated OFDMA cellular system

Device-to-Device communication (D2D) has been a hot research topic in recent years, especially concerning the integration of D2D and conventional cellular networks. In general, the integration improves the efficiency and flexibility of the overall system. Furthermore, D2D can provide partial solutions for some inherent problems of cellular systems, such as cell edge related problems. Currently, most of the D2D integration studies assume that D2D UEs and cellular UEs use identical multiple access (MA) technology for the convenience of integration and backward compatibility. In this paper, besides the conventional OFDMA based D2D, we investigate the use of multicarrier code division multiple access (MC-CDMA) as the MA scheme for D2D UEs. The idea is to use processing gains obtained by spreading against critical interference, especially from cellular UEs. The study is emphasized on interference related issues, including interference analysis of the integrated system, and overall performance enhancement, mainly for D2D UEs, by utilizing frequency domain spreading. Network simulations show the gain against critical interference from cellular UEs. Meanwhile, it is shown that intra-cell cross mode interference control/elimination is the key scheme to guarantee performance of the integrated system. Furthermore, we discuss the potential benefits and procedures of MC-CDMA D2D based cluster integration.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Electronics and Communications Engineering, Research group: Wireless Communications and Positioning
Contributors: Xing, H., Renfors, M.
Publication date: 5 Jul 2016

Host publication information

Title of host publication: 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring)
ISBN (Electronic): 9781509016983
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Applied Mathematics
Keywords: D2D, MC-CDMA, OFDMA
Source: Scopus
Source ID: 84979740932

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Multicolor nonlinear pulse compression by consecutive optical parametric amplification in quasi-phase matched structures

Simultaneous generation of the 2nd and 3rd harmonic, excited by linearly frequency-chirped fundamental pulse in quasiphase matched grating with linearly varying inverse domain sizes has been studied numerically with taking into account effects of the group velocity mismatches and dispersions. Mechanisms of efficient nonlinear pulse compressions and conversion efficiencies of the generated harmonics have been analyzed.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, Academy of Sciences of the Republic of Uzbekistan, Tashkent State Technical University, Nonlinear Optics and OptoElectronics Lab, University “Roma Tre”
Contributors: Sapaev, U. K., Yusupov, D. B., Assanto, G.
Publication date: 2011

Host publication information

Title of host publication: ICONO 2010: International Conference on Coherent and Nonlinear Optics
Volume: 7993
Article number: 79930Q
ISBN (Print): 9780819485663
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Cascading, Lithium niobate, Nonlinear pulse compression, Parametric effects, Quasi-phase matching, Simultaneous frequency doubling and tripling
Source: Scopus
Source ID: 79951653950

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Multidimensional dataflow graph modeling and mapping for efficient GPU implementation

Multidimensional synchronous dataflow (MDSDF) provides an effective model of computation for a variety of multidimensional DSP systems that have static dataflow structures. In this paper, we develop new methods for optimized implementation of MDSDF graphs on embedded platforms that employ multiple levels of parallelism to enhance performance at different levels of granularity. Our approach allows designers to systematically represent and transform multi-level parallelism specifications from a common, MDSDF-based application level model. We demonstrate our methods with a case study of image histogram implementation on a graphics processing unit (GPU). Experimental results from this study show that our approach can be used to derive fast GPU implementations, and enhance trade-off analysis during design space exploration.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing Research Community (SPRC), University of Maryland, Air Force Research Laboratory Information Directorate, University of Missouri-Columbia, Department of Electrical and Computer Engineering
Contributors: Wang, L. H., Shen, C. C., Seetharaman, G., Palaniappan, K., Bhattacharyya, S. S.
Number of pages: 6
Pages: 300-305
Publication date: 2012

Host publication information

Title of host publication: Proceedings - 2012 IEEE Workshop on Signal Processing Systems, SiPS 2012
Article number: 6363272
ISBN (Print): 9780769548562
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics, Hardware and Architecture
Keywords: Dataflow graph, Graphics processing unit, Integral histogram, Multidimensional synchronous dataflow
Source: Scopus
Source ID: 84875330462

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Multiwavelength surface contouring from phase-coded diffraction patterns

We propose a new algorithm for absolute phase retrieval from multiwavelength noisy phase coded diffraction patterns in the task of surface contouring. A lensless optical setup is considered with a set of successive single wavelength experiments. The phase masks are applied for modulation of the multiwavelength object wavefronts. The algorithm uses the forward and backward propagation for coherent light beams and sparsely encoding wavefronts which leads to the complex-domain block-matching 3D filtering. The key-element of the algorithm is an original aggregation of the multiwavelength object wavefronts for high-dynamic-range profile measurement. Numerical experiments demonstrate that the developed approach leads to the effective solutions explicitly using the sparsity for noise suppression and high-accuracy object profile reconstruction.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing, Research group: Computational Imaging-CI, ITMO University
Contributors: Katkovnik, V., Shevkunov, I., Petrov, N. V., Eguiazarian, K.
Publication date: 1 Jan 2018

Host publication information

Title of host publication: Unconventional Optical Imaging 2018. Strasbourg, France
Publisher: SPIE
Article number: 106771B
ISBN (Print): 978-1-5106-1880-0

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10677
ISSN (Electronic): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: absolute phase retrieval, discrete optical signal processing, Multiwavelength phase retrieval, phase imaging, surface contouring
Source: Scopus
Source ID: 85052446644

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

No-reference visual quality assessment for image inpainting

Inpainting has received a lot of attention in recent years and quality assessment is an important task to evaluate different image reconstruction approaches. In many cases inpainting methods introduce a blur in sharp transitions in image and image contours in the recovery of large areas with missing pixels and often fail to recover curvy boundary edges. Quantitative metrics of inpainting results currently do not exist and researchers use human comparisons to evaluate their methodologies and techniques. Most objective quality assessment methods rely on a reference image, which is often not available in inpainting applications. Usually researchers use subjective quality assessment by human observers. It is difficult and time consuming procedure. This paper focuses on a machine learning approach for no-reference visual quality assessment for image inpainting based on the human visual property. Our method is based on observation that Local Binary Patterns well describe local structural information of the image. We use a support vector regression learned on assessed by human images to predict perceived quality of inpainted images. We demonstrate how our predicted quality value correlates with qualitative opinion in a human observer study. Results are shown on a human-scored dataset for different inpainting methods.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: Computational Imaging-CI, Signal Processing Research Community (SPRC), Dept. of Radio-Electronics Systems, Don State Technical University
Contributors: Voronin, V. V., Frantc, V. A., Marchuk, V. I., Sherstobitov, A. I., Egiazarian, K.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Publisher: SPIE
Article number: 93990U
ISBN (Print): 9781628414899

Publication series

Name: SPIE Conference Proceedings
Volume: 9399
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Inpainting, Machine learning, Metric, Quality assessment, SVR, Visual salience
Source: Scopus
Source ID: 84928473922

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Novel frequency domain cyclic prefix autocorrelation based compressive spectrum sensing for cognitive radio

Cognitive radio (CR) has received increasing attention and is considered an important solution to the spectral crowding problem. The main idea behind CR technology is to utilize the unused spectral resources which are determined to be available for secondary user by effective spectrum sensing techniques. However, CR technology significantly depends on the spectrum sensing techniques which are applied to detect the presence of primary user (PU) signals. This paper focuses on detecting OFDM primaries using novel frequency-domain cyclic prefix (CP) autocorrelation based compressive spectrum sensing algorithms. To counteract the practical wireless channel effects, frequency domain approaches for PU signal detection are developed. The proposed spectrum sensing method eliminates the effects of both noise uncertainty and frequency selective channels. Using the frequency domain autocorrelation approach results in highly increased flexibility, facilitating robust wideband multi-mode, multi-channel sensing with low complexity. It also allows to sense weak PU signals which are partly overlapped by other strong PU or CR transmissions.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Electronics and Communications Engineering, Research group: Wireless Communications and Positioning
Contributors: Dikmese, S., Ilyas, Z., Sofotasios, P., Renfors, M., Valkama, M.
Publication date: 5 Jul 2016

Host publication information

Title of host publication: 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring)
Publisher: IEEE
ISBN (Electronic): 9781509016983
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Applied Mathematics
Keywords: Cognitive radio, Energy detector, Frequency selective channel and noise uncertainty, OFDMVCP, Time and/or frequency domain CP autocorrelation based compressive spectrum sensing

Bibliographical note

INT=elt,"Ilyas, Zobia"

Source: Scopus
Source ID: 84979752384

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Observation of local electroluminescent cooling and identifying the remaining challenges

The cooling of a light emitting diode (LED) by photons carrying out more energy than was used to electrically bias the device, has been predicted decades ago. 1, 2 While this effect, known as electroluminescent cooling (ELC), may allow e.g. fabricating thermophotonic heat pumps (THP) providing higher efficiencies than the existing solid state coolers, 3 ELC at powers sufficient for practical applications is still not demonstrated. To study high-power ELC we use double diode structures (DDSs), which consist of a double heterojunction (DHJ) LED and a photodiode (PD) grown within a single technological process and, thus, enclosed in a cavity with a homogeneous refractive index. 4, 5 The presence of the PD in the structure allows to more directly probe the efficiency of the LED, without the need for light extraction from the system, reducing undesirable losses. Our analysis of experimentally measured I - V curves for both the LED and the PD suggests that the local efficiency of the high-performance LEDs we have fabricated is approximately 110%, exceeding unity over a wide range of injection current densities of up to about 100A/cm 2 . At present the efficiency of the full DDS, however, still falls short of unity, not allowing direct evidence of the extraction of thermal energy from the LED. Here we review our previous studies of DDS for high-power EL cooling and discuss in more detail the remaining bottlenecks for demonstrating high-power ELC in the DDS context: the LED surface states, resistive and photodetection losses. In particular we report our first surface passivation measurements. Further optimization therefore mainly involves reducing the influence of the surface states, e.g. using more efficient surface passivation techniques and optimizing the PD. This combined with the optimization of the DDS layer thicknesses and contact metallization schemes is expected to finally allow purely experimental observation of high-power ELC.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Physics, Aalto University
Contributors: Radevici, I., Sadi, T., Tripurari, T., Tiira, J., Ranta, S., Tukiainen, A., Guina, M., Oksanen, J.
Publication date: 2019

Host publication information

Title of host publication: Photonic Heat Engines : Science and Applications
Publisher: SPIE, IEEE
Editors: Seletskiy, D. V., Epstein, R. I., Sheik-Bahae, M.
Article number: 109360A
ISBN (Electronic): 9781510625143

Publication series

Name: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 10936
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Double diode structures, Electroluminescent cooling, III-V semiconductors, Quantum efficiency, Surface states

Bibliographical note

jufoid=71479

Source: Scopus
Source ID: 85065604697

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Optical and topographic changes in water-responsive patterned cholesteric liquid crystalline polymer coatings

In this work, we present patterned water-responsive coatings, which alter both their topological and optical properties. The polymer coatings are based on a hydrogen-bonded cholesteric liquid crystalline polymer network. A two-step photopolymerization procedure leads to a patterned coating with repeating liquid crystalline and isotropic areas. The cholesteric liquid crystalline areas reflect green light, whilst the isotropic areas are transparent for visible light. Treatment with alkaline solution results in a hygroscopic polymer salt coating. When placed in demineralized water, the polymer films swells, leading to an enhancement of the surface topography structure in which the liquid crystalline areas swell more. Moreover, the pitch of the helical organization in the cholesteric areas increases due to this swelling leading to a color change from green to red.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Eindhoven University of Technology, School of Mathematical Sciences
Contributors: Stumpel, J. E., Broer, D. J., Bastiaansen, C. W. M., Schenning, A. P. H. J.
Publication date: 2014

Host publication information

Title of host publication: Proceedings of SPIE : Organic Photonics VI
Volume: 9137
Publisher: SPIE
Article number: 91370U
ISBN (Print): 9781628410853

Publication series

Name: Proceedings of SPIE: the International Society for Optical Engineering
Publisher: SPIE
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: cholesteric liquid crystals, patterned surfaces, responsive optical coatings, responsive surface topographies, water-responsive

Bibliographical note

EXT="Stumpel, Jelle"

Source: Scopus
Source ID: 84902324488

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Optical Asymmetric Modulation for VLC Systems - Invited Paper

The explosive growth of connected devices and the increasing number of broadband users have led to an unprecedented growth in traffic demand. To this effect, the next generation wireless systems are envisioned to meet this growth and offer a potential data rate of 10 Gbps or more. In this context, an attractive solution to the current spectrum crunch issue is to exploit the visible light spectrum for the realization of high-speed commutation systems. However, this requires solutions to certain challenges relating to visible light communications (VLC), such as the stringent requirements of VLC-based intensity modulation and direct detection (IM/DD), which require signals to be real and unipolar. The present work proposes a novel power-domain multiplexing based optical asymmetric modulation (OAM) scheme for indoor VLC systems, which is particularly adapted to transmit high-order modulation signals using linear real and unipolar constellations that fit into the restrictions of IM/DD systems. It is shown that the proposed scheme provides improved system performance that outperforms alternative modulation schemes, at no extra complexity.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Wireless Communications and Positioning, Electronics and Communications Engineering, Khalifa University, University of Glasgow, Aristotle University of Thessaloniki
Contributors: Marshoud, H., Muhaidat, S., Sofotasios, P. C., Imran, M., Sharif, B. S., Karagiannidis, G. K.
Number of pages: 5
Pages: 1-5
Publication date: 20 Jul 2018

Host publication information

Title of host publication: 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018
Publisher: IEEE
ISBN (Electronic): 9781538663554
ASJC Scopus subject areas: Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Source: Scopus
Source ID: 85050962279

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Optical fiber amplifier with spectral compression elements for high-power laser pulse generation

We report main features of spectral compression of parabolic pulses in nonlinear optical fibers. It is shown that the variational analysis correctly describes evolution of pulse parameters during spectral compression. The model of cascade amplifier system employing spectral compression is developed to achieve superior spectral densities. The proposed configuration is promising as optical pulse preamplifier for operation in the high-energy pulse laser systems.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Optoelectronics Research Centre, University de Mons, Ulyanovsk State University, Optoelectronic Research Center
Contributors: Fotiadi, A. A., Korobko, D. A., Okhotnikov, O. G., Zolotovskii, I. O.
Publication date: 2016

Host publication information

Title of host publication: Nonlinear Optics and its Applications IV
Volume: 9894
Publisher: SPIE
Article number: 989411
ISBN (Electronic): 9781510601390

Publication series

Name: Proceedings of SPIE
Volume: 9894
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: Fiber optics amplifiers, high-power laser pulses, nonlinear spectral compression, phase self-modulation
Source: Scopus
Source ID: 84985911601

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Parameterized core functional dataflow graphs and their application to design and implementation of wireless communication systems

Due to the increased complexity of dynamics in modern DSP applications, dataflow-based design methodologies require significant enhancements in modeling and scheduling techniques to provide for efficient and flexible handling of dynamic behavior. In this paper, we address this problem through a new framework that is based on integrating two complementary modeling techniques, core functional dataflow (CFDF) and parameterized synchronous dataflow (PSDF). We apply, in a systematically integrated way, the structured mode-based dynamic dataflow modeling capability of CFDF together with the features of PSDF for dynamic parameter reconfiguration and quasi-static scheduling. We refer to this integrated methodology for mode - and dynamic-parameter - based modeling and scheduling as core functional parameterized synchronous dataflow (CF-PSDF). Through a wireless communication case study involving MIMO detection, we demonstrate the utility of design and implementation using CF-PSDF graphs. Experimental results on this case study demonstrate the efficiency and flexibility of our proposed new CF-PSDF based design methodology.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing Research Community (SPRC), University of Maryland
Contributors: Wang, L. H., Shen, C. C., Bhattacharyya, S. S.
Number of pages: 6
Pages: 1-6
Publication date: 2013

Host publication information

Title of host publication: 2013 IEEE Workshop on Signal Processing Systems, SiPS 2013
Publisher: Institute of Electrical and Electronics Engineers Inc.
Article number: 6674471
ISBN (Print): 9781467362382
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics, Hardware and Architecture
Keywords: Dataflow graph, Dynamic scheduling, MIMO detector, Parameterized modeling
Source: Scopus
Source ID: 84896476923

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Performance Analysis of Single Carrier Coherent and Noncoherent Modulation under I/Q Imbalance

In-phase/quadrature-phase Imbalance (IQI) is considered a major performance-limiting impairment in direct-conversion transceivers. Its effects become even more pronounced at higher carrier frequencies such as the millimeter-wave frequency bands considered for 5G systems. In this work, we quantify the effects of IQI on the performance of different modulations under multipath fading channels. This is realized by developing a comprehensive framework for the symbol error rate (SER) analysis of coherent phase shift keying (PSK), noncoherent differential phase shift keying (DPSK) and noncoherent frequency shift keying (FSK) under IQI effects. In this context, the moment generating function of the signal-to-interference-plus-noise-ratio is first derived for single-carrier systems suffering from transmitter (TX) IQI only, receiver (RX) IQI only and joint TX/RX IQI. Capitalizing on this, we derive analytic expressions for the SER of the different modulation schemes considered. These expressions are corroborated with simulation results and they provide insights into the dependence of IQI on the system parameters. We further demonstrate that, while in some cases, IQI can cause a slight degradation of the SER performance and, hence, it can be neglected, in other cases it should be compensated in order to achieve a reliable communication link.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Wireless Communications and Positioning, Electronics and Communications Engineering, Khalifa University, Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, University of Texas at Dallas
Contributors: Selim, B., Muhaidat, S., Sofotasios, P. C., Sharif, B. S., Stouraitis, T., Karagiannidis, G. K., Al-Dhahir, N.
Number of pages: 5
Pages: 1-5
Publication date: 20 Jul 2018

Host publication information

Title of host publication: 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018
Publisher: IEEE
ISBN (Electronic): 9781538663554
ASJC Scopus subject areas: Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Source: Scopus
Source ID: 85050981792

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Performance Evaluation of Coordinated Multipoint Transmission at 28 GHz Frequency Using 3D Ray Tracing

The main target of this paper is to evaluate the performance of Coordinated Multipoint (CoMP) transmission technique at Millimeter Wave (mmWave) frequency through a comprehensive set of simulations. A new metric for the performance evaluation of CoMP functionality called the Net CoMP utilization gain is introduced in this paper that takes into account the expected loading of the coordinating cells. Other performance metrics considered are the Signal to Interference plus Noise Ratio (SINR), throughput and dominance area. The acquired results show that the adoption of CoMP functionality provides higher gain in improving the Quality of Service (QoS) for the cell edge users compared with the other users. The net CoMP utilization gain as well as the overhead increases with the increase in number of transmission points (TPs). However, in highly loaded networks the risk of having negative impact (capacity loss) also increases with the increase in number of transmission points.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Electronics and Communications Engineering
Contributors: Sheikh, M. U., Biswas, R., Lempiäinen, J.
Number of pages: 6
Pages: 1-6
Publication date: 20 Jul 2018

Host publication information

Title of host publication: 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018 - Proceedings
Publisher: IEEE
ISBN (Electronic): 9781538663554
ASJC Scopus subject areas: Computer Science Applications, Electrical and Electronic Engineering, Applied Mathematics
Keywords: 3D ray tracing, CoMP, macro cellular, mmWave propagation, performance analysis
Source: Scopus
Source ID: 85050982698

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Picosecond MOPA with ytterbium doped tapered double clad fiber

The powerful picosecond master oscillator - power amplifier (MOPA) with double clad ytterbium doped tapered fiber as a buster amplifier has been demonstrated in the presented paper. The developed MOPA has 60ps pulses with 0.3mJ pulse energy and 5MW peak power.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Research group: Ultrafast and intense lasers, Photonics, Research group: Nanophotonics, Ampliconyx Ltd, Institute of Radio Engineering and Electronics of the Russian Academy of Sciences
Contributors: Filippov, V., Vorotynskii, A., Noronen, T., Gumenyuk, R., Chamorovskii, Y., Golant, K.
Number of pages: 6
Publication date: 2017

Host publication information

Title of host publication: Fiber Lasers XIV : Technology and Systems
Volume: 10083
Publisher: SPIE
Article number: 100831H
ISBN (Electronic): 9781510606074

Publication series

Name: Proceedings of SPIE
Publisher: SPIE
No.: 10083
ISSN (Print): 0277-786X
ISSN (Electronic): 1996-756X
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering
Keywords: Fiber laser, Picosecond laser, Ultrafast laser
Source: Scopus
Source ID: 85019465842

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Power and wavelength scaling using semiconductor disk laser - bismuth fiber MOPA systems

We present a master oscillator power amplifier (MOPA) system that comprises a mode-locked semiconductor disk laser (SDL) emitting at 1.33 mu m and a bismuth-doped fiber amplifier. The mode-locked SDL was fabricated by wafer bonding an InP-based gain section with a GaAs-based distributed Bragg reflector (DBR) using (3-Mercaptopropyl)trimethoxysilane. The bismuth-doped fiber amplifier was pumped with a continuous wave SDL emitting at 1.18 mu m. The MOPA system produced pulses at a repetition rate of 827 MHz with a pulse energy of 0.62 nJ, which corresponds to an average output power of more than 0.5 W.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Frontier Photonics, Optoelectronics Research Centre, Research group: Ultrafast and intense lasers, Research group: Semiconductor Technology and Applications, Ulyanovsk State University, Fiber Optics Research Center, Russian Academy of Sciences
Contributors: Heikkinen, J., Gumenyuk, R., Rantamäki, A., Lyytikäinen, J., Leinonen, T., Zolotovskii, I., Melkumov, M., Dianov, E. M., Okhotnikov, O. G.
Number of pages: 7
Publication date: 2015

Host publication information

Title of host publication: Vertical External Cavity Surface Emitting Lasers (VECSELs) V
Place of publication: BELLINGHAM
Publisher: SPIE
Editor: Guina, M.
Article number: 93490E
ISBN (Print): 9781628414394

Publication series

Name: Proceedings of SPIE
Publisher: SPIE-INT SOC OPTICAL ENGINEERING
Volume: 9349
ISSN (Print): 0277-786X
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Semiconductor disk laser (SDL), vertical-external-cavity surface-emitting laser (VECSEL), modelocking, wafer bonding, bismuth-doped fiber, master oscillator power amplifier (MOPA), SUPERCONTINUUM GENERATION, OUTPUT POWER, PICOSECOND, VECSEL, PULSES, GHZ
Source: WOS
Source ID: 000353134900011

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Preserving natural scene lighting by strobe-lit video

Capturing images in low light intensity, and preserving ambient light in such conditions pose significant problems in terms of achievable image quality. Either the sensitivity of the sensor must be increased, filling the resulting image with noise, or the scene must be lit with artificial light, destroying the aesthetic quality of the image. While the issue has been previously tackled for still imagery using cross-bilateral filtering, the same problem exists in capturing video. We propose a method of illuminating the scene with a strobe light synchronized to every other frame captured by the camera, and merging the information from consecutive frames alternating between high gain and high intensity lighting. The motion between the frames is compensated using motion estimation based on block matching between strobe-illuminated frames. The uniform lighting conditions between every other frame make it possible to utilize conventional motion estimation methods, circumventing the image registration challenges faced in fusing flash/non-flash pairs from non-stationary images. The results of the proposed method are shown to closely resemble those computed using the same filter based on reference images captured at perfect camera alignment. The method can be applied starting from a simple set of three frames to video streams of arbitrary lengths with the only requirements being sufficiently accurate syncing between the imaging device and the lighting unit, and the capability to switch states (sensor gain high/low, illumination on/off) fast enough.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Signal Processing, Research group: 3D MEDIA, Signal Processing Research Community (SPRC)
Contributors: Suominen, O., Gotchev, A.
Publication date: 2015

Host publication information

Title of host publication: Image Processing: Algorithms and Systems XIII
Publisher: SPIE
Article number: 939919
ISBN (Print): 9781628414899

Publication series

Name: SPIE Conference Proceedings
Volume: 9399
ASJC Scopus subject areas: Applied Mathematics, Computer Science Applications, Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Keywords: Ambient light, Bilateral filter, Computational photography, Image denoising, Low-light, Motion compensation
Electronic versions: 
Source: Scopus
Source ID: 84928473920

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Prioritized centrally-controlled resource allocation in integrated multi-RAT HetNets

Given the importance of multi-radio heterogeneous networks (HetNets) in delivering more throughput and better connectivity experience to today's wireless users, we investigate the prioritized centrally-controlled resource allocation mechanisms in such systems. First, we theoretically formulate the problem of assisted rate allocation across multiple radio access technologies (RATs) as a special case of relative max-min fairness problem with bifurcated (splittable) traffic flows, which can then be solved by employing the standard linear optimization techniques. Our proposed solution delivers certain minimum guarantees to all the network users, while the rest of system resources are divided proportionally to the preset priority of the users. The priorities in our system may correspond to different subscription/pricing plans of a network operator. Finally, we demonstrate the practical benefits of the proposed resource allocation scheme with system-level simulations, as well as discuss its implementation within a testbed prototype based on the OpenFlow architecture.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Department of Electronics and Communications Engineering, Tampere University of Technology, Research group: Emerging Technologies for Nano-Bio-Info-Cogno, Wireless Communications and Positioning (WICO), Intel Corporation
Contributors: Gerasimenko, M., Moltchanov, D., Florea, R., Himayat, N., Andreev, S., Koucheryavy, Y.
Number of pages: 7
Publication date: 1 Jul 2015

Host publication information

Title of host publication: IEEE Vehicular Technology Conference
Volume: 2015-July
Publisher: The Institute of Electrical and Electronics Engineers, Inc.
ISBN (Print): 9781479980888
ASJC Scopus subject areas: Electrical and Electronic Engineering, Computer Science Applications, Applied Mathematics

Bibliographical note

AUX=elt,"Florea, Roman"

Source: Scopus
Source ID: 84940398708

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Programmable implementation of zero-crossing demodulator on an application specific processor

The zero-intermediate frequency zero-crossing demodulator (ZIFZCD) is extensively used for demodulating continuous phase frequency shift keying (CPFSK) signals in low power and low cost devices. ZIFZCD has previously been implemented as hardwired circuits. Many variations have been suggested to the ZIFZCD algorithm for different modulation methods and channel conditions. To support all these variants, a programmable processor based implementation of the ZIFZCD is needed. This paper describes a programmable software implementation of ZIFZCD on an application specific processor (ASP). The ASP is based on transport triggered architecture (TTA) and provides an ideal low power platform for ZIFZCD implementation due to its simplicity. The designed processor operates at a maximum clock frequency of 250 MHz and has gate count of 134 kGE for a 32-bit TTA processor and 76 kGE for a 16-bit processor. The demodulator has been developed as a part of an open source radio implementation for wireless sensor nodes.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing Research Community (SPRC), Dept. of Computer Science and Engineering, Univ of Oulu
Contributors: Ghazi, A., Boutellier, J., Hannuksela, J., Shahabuddin, S., Silvén, O.
Number of pages: 6
Pages: 231-236
Publication date: 2013

Host publication information

Title of host publication: 2013 IEEE Workshop on Signal Processing Systems, SiPS 2013
Publisher: Institute of Electrical and Electronics Engineers Inc.
Article number: 6674510
ISBN (Print): 9781467362382
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics, Hardware and Architecture
Keywords: Demodulation, Signal Processing, Software radio
Source: Scopus
Source ID: 84896460964

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

Programming graphics processing units in the RVC-CAL dataflow language

The interest towards programming of streaming applications using dataflow models of computation has been increasing steadily in the recent years. Among the numerous dataflow formalisms, the ISO-standardized RVC-CAL dataflow language has offered a solid basis for programming tool development and research. To this date RVC-CAL programming tools have enabled transforming dataflow programs into concurrent executables for multicore processors, as well as for generating synthesizable hardware descriptions. In this paper it is shown how the RVC-CAL dataflow language can be used for programming graphics processing units (GPUs) with high efficiency. Considering the processing architectures of recent mobile and desktop computing devices, this advance is of high importance, as most consumer devices contain a graphics processing unit nowadays. To evaluate the proposed solution, the paper presents a video processing application case study. At best, the solution is shown to provide a speedup of 42× over single-threaded CPU execution.

General information

Publication status: Published
MoE publication type: A4 Article in a conference publication
Organisations: Signal Processing Research Community (SPRC), Dept. of Computer Science and Engineering, Univ of Oulu
Contributors: Boutellier, J., Nyländen, T.
Publication date: 2 Dec 2015

Host publication information

Title of host publication: Electronic Proceedings of the 2015 IEEE International Workshop on Signal Processing Systems, SiPS 2015
Volume: 2015-December
Publisher: Institute of Electrical and Electronics Engineers Inc.
Article number: 7344994
ISBN (Electronic): 9781467396042
ASJC Scopus subject areas: Electrical and Electronic Engineering, Signal Processing, Applied Mathematics, Hardware and Architecture
Keywords: Dataflow computing, design automation, parallel processing