Portfolio EDEND: 2013-10-29

Publisher name: Emerald Group Publishing PY - 2013 Y1 - 2013 N2 - 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. AB - 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. KW - Coupled systems KW - Electrical equipment KW - Finite element simulation KW - Iron KW - Iron losses KW - Magnetoelasticity KW - Stress KW - Stress analysis UR - http://www.scopus.com/inward/record.url?scp=84884134763&partnerID=8YFLogxK U2 - 10.1108/COMPEL-04-2013-0109 DO - 10.1108/COMPEL-04-2013-0109 M3 - Article VL - 32 SP - 1484 EP - 1499 JO - COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering JF - COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering SN - 0332-1649 IS - 5 M1 - 17095978 ER - TY - GEN T1 - Measuring bend losses in large-mode-area fibers AU - Ye, Changgeng AU - Koponen, Joona AU - Aallos, Ville AU - Kokki, Teemu AU - Petit, Laeticia AU - Kimmelma, Ossi PY - 2015 Y1 - 2015 N2 - 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. AB - 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. KW - Bend loss KW - Few-mode KW - Fiber amplifiers KW - Fiber lasers KW - Large-mode-area fiber KW - Silica optical fiber UR - http://www.scopus.com/inward/record.url?scp=84931311791&partnerID=8YFLogxK U2 - 10.1117/12.2076813 DO - 10.1117/12.2076813 M3 - Conference contribution VL - 9344 BT - Fiber Lasers XII: Technology, Systems, and Applications PB - SPIE ER - TY - GEN T1 - MECSELs with direct emission in the 760 nm to 810 nm spectral range T2 - A single- and double-side pumping comparison and high-power continuous-wave operation AU - Kahle, Hermann AU - Penttinen, Jussi Pekka AU - Phung, Hoy My AU - Rajala, Patrik AU - Tukiainen, Antti AU - Ranta, Sanna AU - Guina, Mircea N1 - INT=phys,"Rajala, Patrik" jufoid=71479 PY - 2019 Y1 - 2019 N2 - 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. AB - 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. KW - AlGaAs KW - DBR-free KW - MECSEL KW - Near infra-red KW - Thermal management KW - Thermal resistance KW - VECSEL U2 - 10.1117/12.2512111 DO - 10.1117/12.2512111 M3 - Conference contribution T3 - Proceedings of SPIE - The International Society for Optical Engineering BT - Vertical External Cavity Surface Emitting Lasers (VECSELs) IX A2 - Keller, Ursula PB - SPIE, IEEE ER - TY - JOUR T1 - Meeting a deadline T2 - shortest paths on stochastic directed acyclic graphs with information gathering AU - Lauri, Mikko AU - Ropponen, Aino AU - Ritala, Risto PY - 2017/4 Y1 - 2017/4 N2 - 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. AB - 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. KW - Applied probability KW - Decision processes KW - Dynamic programming KW - Markov processes KW - Transportation U2 - 10.1007/s10472-016-9527-5 DO - 10.1007/s10472-016-9527-5 M3 - Article VL - 79 SP - 337 EP - 370 JO - Annals of Mathematics and Artificial Intelligence JF - Annals of Mathematics and Artificial Intelligence SN - 1012-2443 IS - 4 ER - TY - GEN T1 - Mode coupling in few-mode large-mode-area fibers AU - Ye, Changgeng AU - Koponen, Joona AU - Aallos, Ville AU - Petit, Laeticia AU - Kimmelma, Ossi AU - Kokki, Teemu PY - 2014 Y1 - 2014 N2 - 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. AB - 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. KW - Beam quality KW - Few-mode KW - Large-mode-area fiber KW - Mode coupling KW - Mode decomposition KW - Silica optical fiber UR - http://www.scopus.com/inward/record.url?scp=84900835091&partnerID=8YFLogxK U2 - 10.1117/12.2038575 DO - 10.1117/12.2038575 M3 - Conference contribution SN - 9780819498748 VL - 8961 BT - Fiber Lasers XI: Technology, Systems, and Applications PB - SPIE ER - TY - GEN T1 - Model-based dynamic scheduling for multicore implementation of image processing systems AU - Wu, Jiahao AU - Blattner, Timothy AU - Keyrouz, Walid AU - Bhattacharyya, Shuvra S. PY - 2017/11/14 Y1 - 2017/11/14 N2 - 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. AB - 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. U2 - 10.1109/SiPS.2017.8110003 DO - 10.1109/SiPS.2017.8110003 M3 - Conference contribution BT - 2017 IEEE International Workshop on Signal Processing Systems, SiPS 2017 PB - IEEE ER - TY - JOUR T1 - Modeling carbon dioxide transport in PDMS-based microfluidic cell culture devices AU - Mäki, A. J. AU - Peltokangas, M. AU - Kreutzer, J. AU - Auvinen, S. AU - Kallio, P. N1 - ORG=ase,0.9 ORG=mol,0.1 PY - 2015/12/1 Y1 - 2015/12/1 N2 - 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 (CO2). Therefore, to keep cell culture medium pH in an acceptable level outside these incubators, a suitable CO2 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 CO2 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 CO2 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 CO2 is proposed to accelerate the system performance such that a faster and more uniform CO2 concentration response is achieved in the area of interest. AB - 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 (CO2). Therefore, to keep cell culture medium pH in an acceptable level outside these incubators, a suitable CO2 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 CO2 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 CO2 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 CO2 is proposed to accelerate the system performance such that a faster and more uniform CO2 concentration response is achieved in the area of interest. KW - Carbon dioxide KW - Finite element method KW - Mass transport KW - Microfluidics cell culturing KW - Numerical simulation KW - pH U2 - 10.1016/j.ces.2015.06.065 DO - 10.1016/j.ces.2015.06.065 M3 - Article VL - 137 SP - 515 EP - 524 JO - Chemical Engineering Science JF - Chemical Engineering Science SN - 0009-2509 ER - TY - JOUR T1 - Modeling probability densities with sums of exponentials via polynomial approximation AU - Dumitrescu, Bogdan AU - Şicleru, Bogdan C. AU - Avram, Florin PY - 2016 Y1 - 2016 N2 - 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. AB - 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. KW - Density fitting KW - Optimization KW - Polynomial approximation KW - Semi-infinite programming KW - Sum of exponentials U2 - 10.1016/j.cam.2015.07.032 DO - 10.1016/j.cam.2015.07.032 M3 - Article VL - 292 SP - 513 EP - 525 JO - Journal of Computational and Applied Mathematics JF - Journal of Computational and Applied Mathematics SN - 0377-0427 ER - TY - JOUR T1 - Modeling Transmit Power Reduction for a Typical Cell with Licensed Shared Access Capabilities AU - Mokrov, Evgeny AU - Ponomarenko-Timofeev, Aleksei AU - Gudkova, Irina AU - Masek, Pavel AU - Hosek, Jiri AU - Andreev, Sergey AU - Koucheryavy, Yevgeni AU - Gaidamaka, Yuliya PY - 2018/6 Y1 - 2018/6 N2 - 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. AB - 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. KW - Airplanes KW - Airports KW - Atmospheric modeling KW - Interference KW - Mobile communication KW - Telemetry U2 - 10.1109/TVT.2018.2799141 DO - 10.1109/TVT.2018.2799141 M3 - Article VL - 67 SP - 5505 EP - 5509 JO - IEEE Transactions on Vehicular Technology JF - IEEE Transactions on Vehicular Technology SN - 0018-9545 IS - 6 ER - TY - GEN T1 - Models of architecture T2 - Reproducible efficiency evaluation for signal processing systems AU - Pelcat, Maxime AU - Desnos, Karol AU - Maggiani, Luca AU - Liu, Yanzhou AU - Heulot, Julien AU - Nezan, Jean François AU - Bhattacharyya, Shuvra S. PY - 2016/12/9 Y1 - 2016/12/9 N2 - 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. AB - 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. U2 - 10.1109/SiPS.2016.29 DO - 10.1109/SiPS.2016.29 M3 - Conference contribution T3 - IEEE International Workshop on Signal Processing Systems SP - 121 EP - 126 BT - IEEE International Workshop on Signal Processing Systems, SiPS 2016 PB - IEEE ER - TY - GEN T1 - Monolithic GaInNAsSb/GaAs VECSEL emitting at 1550 nm AU - Korpijärvi, Ville-Markus AU - Kantola, Emmi L. AU - Leinonen, Tomi AU - Guina, Mircea PY - 2015 Y1 - 2015 N2 - 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. AB - 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. KW - dilute nitride KW - diode-pumped lasers KW - GaInNAsSb KW - semiconductor disk lasers KW - Semiconductor lasers KW - vertical external cavity surface emitting lasers U2 - 10.1117/12.2077517 DO - 10.1117/12.2077517 M3 - Conference contribution SN - 9781628414394 VL - 9349 BT - SPIE conference proceedings PB - SPIE ER - TY - GEN T1 - Multi-carrier CDMA for network assisted device-to-device communications for an integrated OFDMA cellular system AU - Xing, Hongnian AU - Renfors, Markku PY - 2016/7/5 Y1 - 2016/7/5 N2 - 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. AB - 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. KW - D2D KW - MC-CDMA KW - OFDMA U2 - 10.1109/VTCSpring.2016.7504354 DO - 10.1109/VTCSpring.2016.7504354 M3 - Conference contribution BT - 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring) ER - TY - GEN T1 - Multicolor nonlinear pulse compression by consecutive optical parametric amplification in quasi-phase matched structures AU - Sapaev, U. K. AU - Yusupov, D. B. AU - Assanto, G. PY - 2011 Y1 - 2011 N2 - 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. AB - 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. KW - Cascading KW - Lithium niobate KW - Nonlinear pulse compression KW - Parametric effects KW - Quasi-phase matching KW - Simultaneous frequency doubling and tripling UR - http://www.scopus.com/inward/record.url?scp=79951653950&partnerID=8YFLogxK U2 - 10.1117/12.882887 DO - 10.1117/12.882887 M3 - Conference contribution SN - 9780819485663 VL - 7993 BT - ICONO 2010: International Conference on Coherent and Nonlinear Optics ER - TY - GEN T1 - Multidimensional dataflow graph modeling and mapping for efficient GPU implementation AU - Wang, Lai Huei AU - Shen, Chung Ching AU - Seetharaman, Gunasekaran AU - Palaniappan, Kannappan AU - Bhattacharyya, Shuvra S. PY - 2012 Y1 - 2012 N2 - 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. AB - 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. KW - Dataflow graph KW - Graphics processing unit KW - Integral histogram KW - Multidimensional synchronous dataflow UR - http://www.scopus.com/inward/record.url?scp=84875330462&partnerID=8YFLogxK U2 - 10.1109/SiPS.2012.10 DO - 10.1109/SiPS.2012.10 M3 - Conference contribution SN - 9780769548562 SP - 300 EP - 305 BT - Proceedings - 2012 IEEE Workshop on Signal Processing Systems, SiPS 2012 ER - TY - JOUR T1 - Multiresolution analysis for compactly supported interpolating tensor product wavelets AU - Höynälänmaa, Tommi PY - 2015/3/6 Y1 - 2015/3/6 N2 - We construct multidimensional interpolating tensor product multiresolution analyses (MRA's) of the function spaces C0(Rn,K), K = R or K = C, consisting of real or complex valued functions on Rn vanishing at infinity and the function spaces Cu(Rn,K) consisting of bounded and uniformly continuous functions on Rn. 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. AB - We construct multidimensional interpolating tensor product multiresolution analyses (MRA's) of the function spaces C0(Rn,K), K = R or K = C, consisting of real or complex valued functions on Rn vanishing at infinity and the function spaces Cu(Rn,K) consisting of bounded and uniformly continuous functions on Rn. 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. KW - Besov space KW - injective tensor norm KW - Interpolating wavelets KW - multiresolution analysis KW - multivariate wavelets KW - projective tensor norm KW - tensor Product UR - http://www.scopus.com/inward/record.url?scp=84928923864&partnerID=8YFLogxK U2 - 10.1142/S0219691315500101 DO - 10.1142/S0219691315500101 M3 - Article VL - 13 JO - International Journal of Wavelets Multiresolution and Information ProcessIng JF - International Journal of Wavelets Multiresolution and Information ProcessIng SN - 0219-6913 IS - 2 M1 - 1550010 ER - TY - GEN T1 - Multiwavelength surface contouring from phase-coded diffraction patterns AU - Katkovnik, Vladimir AU - Shevkunov, Igor AU - Petrov, Nikolay V. AU - Eguiazarian, Karen PY - 2018/1/1 Y1 - 2018/1/1 N2 - 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. AB - 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. KW - absolute phase retrieval KW - discrete optical signal processing KW - Multiwavelength phase retrieval KW - phase imaging KW - surface contouring U2 - 10.1117/12.2306127 DO - 10.1117/12.2306127 M3 - Conference contribution SN - 978-1-5106-1880-0 T3 - Proceedings of SPIE - The International Society for Optical Engineering BT - Unconventional Optical Imaging 2018. Strasbourg, France PB - SPIE ER - TY - JOUR T1 - Nonlocality-Reinforced Convolutional Neural Networks for Image Denoising AU - Cruz, Cristovao AU - Foi, Alessandro AU - Katkovnik, Vladimir AU - Egiazarian, Karen PY - 2018/8/1 Y1 - 2018/8/1 N2 - 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. AB - 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. KW - BM3D KW - convolutional neural network KW - image denoising KW - nonlocal filters U2 - 10.1109/LSP.2018.2850222 DO - 10.1109/LSP.2018.2850222 M3 - Article VL - 25 SP - 1216 EP - 1220 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 8 ER - TY - GEN T1 - No-reference visual quality assessment for image inpainting AU - Voronin, V. V. AU - Frantc, V. A. AU - Marchuk, V. I. AU - Sherstobitov, A. I. AU - Egiazarian, K. PY - 2015 Y1 - 2015 N2 - 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. AB - 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. KW - Inpainting KW - Machine learning KW - Metric KW - Quality assessment KW - SVR KW - Visual salience U2 - 10.1117/12.2076507 DO - 10.1117/12.2076507 M3 - Conference contribution SN - 9781628414899 T3 - SPIE Conference Proceedings BT - Image Processing: Algorithms and Systems XIII PB - SPIE ER - TY - GEN T1 - Novel frequency domain cyclic prefix autocorrelation based compressive spectrum sensing for cognitive radio AU - Dikmese, Sener AU - Ilyas, Zobia AU - Sofotasios, Paschalis AU - Renfors, Markku AU - Valkama, Mikko N1 - INT=elt,"Ilyas, Zobia" PY - 2016/7/5 Y1 - 2016/7/5 N2 - 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. AB - 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. KW - Cognitive radio KW - Energy detector KW - Frequency selective channel and noise uncertainty KW - OFDMVCP KW - Time and/or frequency domain CP autocorrelation based compressive spectrum sensing U2 - 10.1109/VTCSpring.2016.7504368 DO - 10.1109/VTCSpring.2016.7504368 M3 - Conference contribution BT - 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring) PB - IEEE ER - TY - GEN T1 - Observation of local electroluminescent cooling and identifying the remaining challenges AU - Radevici, Ivan AU - Sadi, Toufik AU - Tripurari, Tripathi AU - Tiira, Jonna AU - Ranta, Sanna AU - Tukiainen, Antti AU - Guina, Mircea AU - Oksanen, Jani N1 - jufoid=71479 PY - 2019 Y1 - 2019 N2 - 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. AB - 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. KW - Double diode structures KW - Electroluminescent cooling KW - III-V semiconductors KW - Quantum efficiency KW - Surface states U2 - 10.1117/12.2505814 DO - 10.1117/12.2505814 M3 - Conference contribution T3 - Proceedings of SPIE - The International Society for Optical Engineering BT - Photonic Heat Engines A2 - Seletskiy, Denis V. A2 - Epstein, Richard I. A2 - Sheik-Bahae, Mansoor PB - SPIE, IEEE ER - TY - JOUR T1 - On derivatives of hypergeometric functions and classical polynomials with respect to parameters AU - Sofotasios, P. C. AU - Brychkov, Yu A. PY - 2018/11/2 Y1 - 2018/11/2 N2 - Closed expressions are obtained for derivatives of symbolic order with respect to parameters for the hypergeometric functions, Laguerre, Gegenbauer, Jacobi and some other polynomial. AB - Closed expressions are obtained for derivatives of symbolic order with respect to parameters for the hypergeometric functions, Laguerre, Gegenbauer, Jacobi and some other polynomial. KW - 33C20 KW - 33C45 KW - Bessel polynomial KW - C33 KW - Charlier polynomial KW - continuous Hahn polynomial KW - differentiation KW - Gegenbauer polynomial KW - Hahn polynomial KW - hypergeometric functions KW - Jacobi polynomial KW - Krawtchouk polynomial KW - Laguerre polynomial KW - Legendre function KW - Meixner polynomial KW - Special functions U2 - 10.1080/10652469.2018.1504042 DO - 10.1080/10652469.2018.1504042 M3 - Article VL - 29 SP - 852 EP - 865 JO - Integral Transforms and Special Functions JF - Integral Transforms and Special Functions SN - 1065-2469 IS - 11 ER - TY - JOUR T1 - On efficient network similarity measures AU - Dehmer, Matthias AU - Chen, Zengqiang AU - Shi, Yongtang AU - Zhang, Y. AU - Tripathi, Shailesh AU - Ghorbani, Modjtaba AU - Mowshowitz, Abbe AU - Emmert-Streib, F. PY - 2019/12/1 Y1 - 2019/12/1 N2 - 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. AB - 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. KW - Distance measures KW - Graphs KW - Inequalities KW - Networks KW - Similarity measures U2 - 10.1016/j.amc.2019.06.035 DO - 10.1016/j.amc.2019.06.035 M3 - Article VL - 362 JO - Applied Mathematics and Computation JF - Applied Mathematics and Computation SN - 0096-3003 M1 - 124521 ER - TY - JOUR T1 - On k-Hypermonogenic Functions and Their Mean Value Properties AU - Eriksson, Sirkka-Liisa AU - Orelma, Heikki PY - 2016 Y1 - 2016 N2 - 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. AB - 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. KW - Dirac operator KW - Hyperbolic metric KW - Hypermonogenic KW - Monogenic U2 - 10.1007/s11785-015-0445-z DO - 10.1007/s11785-015-0445-z M3 - Article VL - 10 SP - 311 EP - 325 JO - Complex Analysis and Operator Theory JF - Complex Analysis and Operator Theory SN - 1661-8254 IS - 2 ER - TY - JOUR T1 - Online Spectrogram Inversion for Low-Latency Audio Source Separation AU - Magron, Paul AU - Virtanen, Tuomas N1 - EXT="Magron, Paul" PY - 2020 Y1 - 2020 N2 - 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. AB - 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. KW - Audio source separation KW - low-latency KW - online spectrogram inversion KW - phase recovery KW - sinusoidal modeling U2 - 10.1109/LSP.2020.2970310 DO - 10.1109/LSP.2020.2970310 M3 - Article VL - 27 SP - 306 EP - 310 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 ER - TY - JOUR T1 - On the complexity of restoring corrupted colorings AU - De Biasi, Marzio AU - Lauri, Juho PY - 2019/5 Y1 - 2019/5 N2 - 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. AB - 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. KW - Combinatorial reconfiguration KW - Computational complexity KW - Graph coloring KW - Local search KW - Parameterized complexity U2 - 10.1007/s10878-018-0342-2 DO - 10.1007/s10878-018-0342-2 M3 - Article VL - 37 SP - 1150 EP - 1169 JO - Journal of Combinatorial Optimization JF - Journal of Combinatorial Optimization SN - 1382-6905 IS - 4 ER - TY - JOUR T1 - On the Degree of Multi-Connectivity in 5G Millimeter-Wave Cellular Urban Deployments AU - Gapeyenko, Margarita AU - Petrov, Vitaly AU - Moltchanov, Dmitri AU - Akdeniz, Mustafa Riza AU - Andreev, Sergey AU - Himayat, Nageen AU - Koucheryavy, Yevgeni PY - 2019/2 Y1 - 2019/2 N2 - 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. AB - 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. KW - dynamic human body blockage KW - macro diversity KW - mmWave systems KW - multi-connectivity KW - outage probability U2 - 10.1109/TVT.2018.2887343 DO - 10.1109/TVT.2018.2887343 M3 - Article VL - 68 SP - 1973 EP - 1978 JO - IEEE Transactions on Vehicular Technology JF - IEEE Transactions on Vehicular Technology SN - 0018-9545 IS - 2 ER - TY - JOUR T1 - On the effect of deformation twinning and microstructure to strain hardening of high manganese austenitic steel 3D microstructure aggregates at large strains AU - Lindroos, Matti AU - Laukkanen, Anssi AU - Cailletaud, Georges AU - Kuokkala, Veli-Tapani N1 - EXT="Lindroos, Matti" PY - 2017 Y1 - 2017 N2 - 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. AB - 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. KW - Austenitic manganese steel KW - Crystal plasticity KW - Deformation twinning KW - Microstructure based modeling U2 - 10.1016/j.ijsolstr.2017.07.015 DO - 10.1016/j.ijsolstr.2017.07.015 M3 - Article VL - 125 SP - 68 EP - 76 JO - International Journal of Solids and Structures JF - International Journal of Solids and Structures SN - 0020-7683 ER - TY - JOUR T1 - On the Performance of Visible Light Communication Systems with Non-Orthogonal Multiple Access AU - Marshoud, Hanaa AU - Sofotasios, Paschalis C. AU - Muhaidat, Sami AU - Karagiannidis, George K. AU - Sharif, Bayan S. PY - 2017/10/1 Y1 - 2017/10/1 N2 - 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. AB - 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. KW - bit-error-rate KW - dimming control KW - imperfect channel state information KW - non-orthogonal multiple access KW - Visible light communications U2 - 10.1109/TWC.2017.2722441 DO - 10.1109/TWC.2017.2722441 M3 - Article VL - 16 SP - 6350 EP - 6364 JO - IEEE Transactions on Wireless Communications JF - IEEE Transactions on Wireless Communications SN - 1536-1276 IS - 10 ER - TY - JOUR T1 - On the Temporal Effects of Mobile Blockers in Urban Millimeter-Wave Cellular Scenarios AU - Gapeyenko, Margarita AU - Samuylov, Andrey AU - Gerasimenko, Mikhail AU - Moltchanov, Dmitri AU - Singh, Sarabjot AU - Akdeniz, Mustafa Riza AU - Aryafar, Ehsan AU - Himayat, Nageen AU - Andreev, Sergey AU - Koucheryavy, Yevgeni PY - 2017 Y1 - 2017 N2 - 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. AB - 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. KW - 3GPP KW - Analytical models KW - Biological system modeling KW - Cellular networks KW - Correlation KW - human body blockage KW - Mathematical model KW - mmWave KW - Mobile communication KW - mobility of blockers KW - temporal consistency KW - Vehicle dynamics U2 - 10.1109/TVT.2017.2754543 DO - 10.1109/TVT.2017.2754543 M3 - Article VL - 66 SP - 10124 EP - 10138 JO - IEEE Transactions on Vehicular Technology JF - IEEE Transactions on Vehicular Technology SN - 0018-9545 IS - 11 ER - TY - JOUR T1 - Opportunistic routing through conjugation in bacteria communication nanonetwork AU - Lio', Pietro AU - Balasubramaniam, Sasitharan PY - 2012/3 Y1 - 2012/3 N2 - 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. AB - 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. KW - Bacteria communication nanonetworks KW - Opportunistic routing UR - http://www.scopus.com/inward/record.url?scp=84858002058&partnerID=8YFLogxK U2 - 10.1016/j.nancom.2011.10.003 DO - 10.1016/j.nancom.2011.10.003 M3 - Article VL - 3 SP - 36 EP - 45 JO - Nano Communication Networks JF - Nano Communication Networks SN - 1878-7789 IS - 1 ER - TY - GEN T1 - Optical and topographic changes in water-responsive patterned cholesteric liquid crystalline polymer coatings AU - Stumpel, Jelle E. AU - Broer, Dirk J. AU - Bastiaansen, Cees W M AU - Schenning, Albert P H J N1 - EXT="Stumpel, Jelle" PY - 2014 Y1 - 2014 N2 - 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. AB - 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. KW - cholesteric liquid crystals KW - patterned surfaces KW - responsive optical coatings KW - responsive surface topographies KW - water-responsive UR - http://www.scopus.com/inward/record.url?scp=84902324488&partnerID=8YFLogxK U2 - 10.1117/12.2052678 DO - 10.1117/12.2052678 M3 - Conference contribution SN - 9781628410853 VL - 9137 T3 - Proceedings of SPIE: the International Society for Optical Engineering BT - Proceedings of SPIE PB - SPIE ER - TY - GEN T1 - Optical Asymmetric Modulation for VLC Systems - Invited Paper AU - Marshoud, Hanaa AU - Muhaidat, Sami AU - Sofotasios, Paschalis C. AU - Imran, Muhammad AU - Sharif, Bayan S. AU - Karagiannidis, George K. PY - 2018/7/20 Y1 - 2018/7/20 N2 - 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. AB - 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. U2 - 10.1109/VTCSpring.2018.8417541 DO - 10.1109/VTCSpring.2018.8417541 M3 - Conference contribution SP - 1 EP - 5 BT - 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018 PB - IEEE ER - TY - GEN T1 - Optical fiber amplifier with spectral compression elements for high-power laser pulse generation AU - Fotiadi, Andrei A. AU - Korobko, Dmitry A. AU - Okhotnikov, Oleg G. AU - Zolotovskii, Igor O. PY - 2016 Y1 - 2016 N2 - 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. AB - 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. KW - Fiber optics amplifiers KW - high-power laser pulses KW - nonlinear spectral compression KW - phase self-modulation U2 - 10.1117/12.2223637 DO - 10.1117/12.2223637 M3 - Conference contribution VL - 9894 T3 - Proceedings of SPIE BT - Nonlinear Optics and its Applications IV PB - SPIE ER - TY - JOUR T1 - Optimal energy decay for the wave-heat system on a rectangular domain AU - Batty, Charles AU - Paunonen, Lassi AU - Seifert, David PY - 2019 Y1 - 2019 N2 - 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. AB - 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. KW - C -semigroups KW - Coupled KW - Energy KW - Heat equation KW - Rates of decay KW - Rectangular domain KW - Resolvent estimates KW - Wave equation U2 - 10.1137/18M1195796 DO - 10.1137/18M1195796 M3 - Article VL - 51 SP - 808 EP - 819 JO - SIAM JOURNAL ON MATHEMATICAL ANALYSIS JF - SIAM JOURNAL ON MATHEMATICAL ANALYSIS SN - 0036-1410 IS - 2 ER - TY - JOUR T1 - Organizational structure and the periphery of the gene regulatory network in B-cell lymphoma. AU - de Matos Simoes, Ricardo AU - Tripathi, Shailesh AU - Emmert-Streib, Frank PY - 2012/5/14 Y1 - 2012/5/14 N2 - 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. AB - 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. KW - B-cell lymphoma KW - Gene expression data KW - Gene regulatory network KW - Statistical network inference UR - http://www.scopus.com/inward/record.url?scp=84865119369&partnerID=8YFLogxK U2 - 10.1186/1752-0509-6-38 DO - 10.1186/1752-0509-6-38 M3 - Article VL - 6 JO - BMC Systems Biology JF - BMC Systems Biology SN - 1752-0509 M1 - 38 ER - TY - GEN T1 - Parameterized core functional dataflow graphs and their application to design and implementation of wireless communication systems AU - Wang, Lai Huei AU - Shen, Chung Ching AU - Bhattacharyya, Shuvra S. PY - 2013 Y1 - 2013 N2 - 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. AB - 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. KW - Dataflow graph KW - Dynamic scheduling KW - MIMO detector KW - Parameterized modeling UR - http://www.scopus.com/inward/record.url?scp=84896476923&partnerID=8YFLogxK M3 - Conference contribution SN - 9781467362382 SP - 1 EP - 6 BT - 2013 IEEE Workshop on Signal Processing Systems, SiPS 2013 PB - Institute of Electrical and Electronics Engineers Inc. ER - TY - JOUR T1 - Performance analysis of simultaneous communications in bacterial nanonetworks AU - Komarov, Mikhail AU - Deng, Boya AU - Petrov, Vitaly AU - Moltchanov, Dmitri PY - 2016 Y1 - 2016 N2 - 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. AB - 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. KW - Analytical model KW - Bacterial nanonetworks KW - Multiple Tx-Rx communicating pairs KW - Performance analysis U2 - 10.1016/j.nancom.2016.02.002 DO - 10.1016/j.nancom.2016.02.002 M3 - Article VL - 8 SP - 55 EP - 67 JO - Nano Communication Networks JF - Nano Communication Networks SN - 1878-7789 ER - TY - GEN T1 - Performance Analysis of Single Carrier Coherent and Noncoherent Modulation under I/Q Imbalance AU - Selim, Bassant AU - Muhaidat, Sami AU - Sofotasios, Paschalis C. AU - Sharif, Bayan S. AU - Stouraitis, Thanos AU - Karagiannidis, George K. AU - Al-Dhahir, Naofal PY - 2018/7/20 Y1 - 2018/7/20 N2 - 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. AB - 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. U2 - 10.1109/VTCSpring.2018.8417514 DO - 10.1109/VTCSpring.2018.8417514 M3 - Conference contribution SP - 1 EP - 5 BT - 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018 PB - IEEE ER - TY - GEN T1 - Performance Evaluation of Coordinated Multipoint Transmission at 28 GHz Frequency Using 3D Ray Tracing AU - Sheikh, Muhammad Usman AU - Biswas, Ritayan AU - Lempiäinen, Jukka PY - 2018/7/20 Y1 - 2018/7/20 N2 - 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. AB - 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. KW - 3D ray tracing KW - CoMP KW - macro cellular KW - mmWave propagation KW - performance analysis U2 - 10.1109/VTCSpring.2018.8417593 DO - 10.1109/VTCSpring.2018.8417593 M3 - Conference contribution SP - 1 EP - 6 BT - 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018 - Proceedings PB - IEEE ER - TY - GEN T1 - Picosecond MOPA with ytterbium doped tapered double clad fiber AU - Filippov, Valery AU - Vorotynskii, Andrei AU - Noronen, Teppo AU - Gumenyuk, Regina AU - Chamorovskii, Yuri AU - Golant, Konstantin PY - 2017 Y1 - 2017 N2 - 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. AB - 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. KW - Fiber laser KW - Picosecond laser KW - Ultrafast laser U2 - 10.1117/12.2252006 DO - 10.1117/12.2252006 M3 - Conference contribution VL - 10083 T3 - Proceedings of SPIE BT - Fiber Lasers XIV PB - SPIE ER - TY - GEN T1 - Power and wavelength scaling using semiconductor disk laser - bismuth fiber MOPA systems AU - Heikkinen, Juuso AU - Gumenyuk, Regina AU - Rantamäki, Antti AU - Lyytikäinen, Jari AU - Leinonen, Tomi AU - Zolotovskii, Igor AU - Melkumov, Mikhail AU - Dianov, Evgeny M. AU - Okhotnikov, Oleg G. PY - 2015 Y1 - 2015 N2 - 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. AB - 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. KW - Semiconductor disk laser (SDL) KW - vertical-external-cavity surface-emitting laser (VECSEL) KW - modelocking KW - wafer bonding KW - bismuth-doped fiber KW - master oscillator power amplifier (MOPA) KW - SUPERCONTINUUM GENERATION KW - OUTPUT POWER KW - PICOSECOND KW - VECSEL KW - PULSES KW - GHZ U2 - 10.1117/12.2076805 DO - 10.1117/12.2076805 M3 - Conference contribution SN - 9781628414394 T3 - Proceedings of SPIE BT - Vertical External Cavity Surface Emitting Lasers (VECSELs) V A2 - Guina, M PB - SPIE CY - BELLINGHAM ER - TY - GEN T1 - Preserving natural scene lighting by strobe-lit video AU - Suominen, Olli AU - Gotchev, Atanas PY - 2015 Y1 - 2015 N2 - 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. AB - 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. KW - Ambient light KW - Bilateral filter KW - Computational photography KW - Image denoising KW - Low-light KW - Motion compensation U2 - 10.1117/12.2185013 DO - 10.1117/12.2185013 M3 - Conference contribution SN - 9781628414899 T3 - SPIE Conference Proceedings BT - Image Processing: Algorithms and Systems XIII PB - SPIE ER - TY - GEN T1 - Prioritized centrally-controlled resource allocation in integrated multi-RAT HetNets AU - Gerasimenko, Mikhail AU - Moltchanov, Dmitri AU - Florea, Roman AU - Himayat, Nageen AU - Andreev, Sergey AU - Koucheryavy, Yevgeni N1 - AUX=elt,"Florea, Roman" PY - 2015/7/1 Y1 - 2015/7/1 N2 - 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. AB - 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. U2 - 10.1109/VTCSpring.2015.7146031 DO - 10.1109/VTCSpring.2015.7146031 M3 - Conference contribution SN - 9781479980888 VL - 2015-July BT - IEEE Vehicular Technology Conference PB - The Institute of Electrical and Electronics Engineers, Inc. ER - TY - GEN T1 - Programmable implementation of zero-crossing demodulator on an application specific processor AU - Ghazi, Amanullah AU - Boutellier, Jani AU - Hannuksela, Jari AU - Shahabuddin, Shahriar AU - Silvén, Olli PY - 2013 Y1 - 2013 N2 - 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. AB - 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. KW - Demodulation KW - Signal Processing KW - Software radio UR - http://www.scopus.com/inward/record.url?scp=84896460964&partnerID=8YFLogxK M3 - Conference contribution SN - 9781467362382 SP - 231 EP - 236 BT - 2013 IEEE Workshop on Signal Processing Systems, SiPS 2013 PB - Institute of Electrical and Electronics Engineers Inc. ER - TY - GEN T1 - Programming graphics processing units in the RVC-CAL dataflow language AU - Boutellier, J. AU - Nyländen, T. PY - 2015/12/2 Y1 - 2015/12/2 N2 - 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. AB - 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. KW - Dataflow computing KW - design automation KW - parallel processing UR - http://www.scopus.com/inward/record.url?scp=84958191208&partnerID=8YFLogxK U2 - 10.1109/SiPS.2015.7344994 DO - 10.1109/SiPS.2015.7344994 M3 - Conference contribution VL - 2015-December BT - Electronic Proceedings of the 2015 IEEE International Workshop on Signal Processing Systems, SiPS 2015 PB - Institute of Electrical and Electronics Engineers Inc. ER - TY - GEN T1 - Propagation dynamics of ultrabroadband terahertz beams with orbital angular momentum for wireless data transfer AU - Kulya, Maksim S. AU - Sokolenko, Bogdan AU - Gorodetsky, Andrei AU - Petrov, Nikolay V. N1 - jufoid=71479 PY - 2020 Y1 - 2020 N2 - We investigate an approach to short and medium-range wireless communications based on the use of terahertz beams possessing an orbital angular momentum (OAM) that allows for noise-resistant broadband carrier. A the- oretical model of the proposed beams generation is developed and numerical predictions are given for propagation and visualization of complex-structured THz beams, including ones carrying a unit topological charge on a large number of spectral components of broadband terahertz radiation. The assessment method which in our case is terahertz pulse time-domain holography allows for analyzing spatiooral and spatio-spectral evolution of arbitrary shaped THz wave trains during their propagation in free space and interaction with obstacles. AB - We investigate an approach to short and medium-range wireless communications based on the use of terahertz beams possessing an orbital angular momentum (OAM) that allows for noise-resistant broadband carrier. A the- oretical model of the proposed beams generation is developed and numerical predictions are given for propagation and visualization of complex-structured THz beams, including ones carrying a unit topological charge on a large number of spectral components of broadband terahertz radiation. The assessment method which in our case is terahertz pulse time-domain holography allows for analyzing spatiooral and spatio-spectral evolution of arbitrary shaped THz wave trains during their propagation in free space and interaction with obstacles. KW - THz radiation KW - Vortex beams KW - wireless data transfer U2 - 10.1117/12.2547695 DO - 10.1117/12.2547695 M3 - Conference contribution SN - 9781510633773 T3 - Proceedings of SPIE - The International Society for Optical Engineering BT - Broadband Access Communication Technologies XIV A2 - Dingel, Benjamin B. A2 - Tsukamoto, Katsutoshi A2 - Mikroulis, Spiros PB - SPIE ER - TY - JOUR T1 - Properties of graph distance measures by means of discrete inequalities AU - Dehmer, Matthias AU - Chen, Zengqiang AU - Emmert-Streib, Frank AU - Shi, Yongtang AU - Tripathi, Shailesh AU - Musa, Aliyu AU - Mowshowitz, Abbe N1 - EXT="Tripathi, Shailesh" PY - 2018/7/1 Y1 - 2018/7/1 N2 - 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. AB - 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. KW - Distance measures KW - Graphs KW - Inequalities KW - Networks KW - Similarity measures U2 - 10.1016/j.apm.2018.01.027 DO - 10.1016/j.apm.2018.01.027 M3 - Article VL - 59 SP - 739 EP - 749 JO - Applied Mathematical Modelling JF - Applied Mathematical Modelling SN - 0307-904X ER - TY - GEN T1 - Pulsed high-power yellow-orange VECSEL AU - Kantola, Emmi AU - Leinonen, Tomi AU - Ranta, Sanna AU - Tavast, Miki AU - Guina, Mircea N1 - Contribution: organisation=orc,FACT1=1

Portfolio EDEND: 2014-08-31

Publisher name: SPIE - International Society for Optical Engineering PY - 2014 Y1 - 2014 N2 - We report on the development of a pulsed high-power frequency doubled vertical-external-cavity surface-emitting laser (VECSEL) with a peak output power of 14 W and emission spectrum near 588 nm. The semiconductor gain chip was grown by molecular beam epitaxy and comprised 10 GaInAs quantum wells. The gain structure was designed to be antiresonant at 1180 nm. The fundamental wavelength was frequency doubled to the yellow-orange spectral range using a 10-mm long critically phase matched lithium triborate nonlinear crystal, situated at the mode waist of the V-shaped laser cavity. The emission spectrum was narrowed down to FWHM of < 0.2 nm by employing a 1.5 mm birefringent filter and a 100-μm-thick etalon inside the cavity. By directly modulating the pump laser of the VECSEL, we were able to produce pulse widths down to 570 ns with average and peak output power of 81 mW and 14 W, respectively. The repetition rate was kept constant at 10 kHz throughout the measurements. The maximum peak power obtained was pump power limited. In comparison, at the same coolant temperature, a maximum of 8.5 W was achieved in continuous wave. The maximum optical-to-optical conversion efficiency (absorbed peak pump power to peak output power) was calculated to be 20-21 %. © 2014 SPIE. AB - We report on the development of a pulsed high-power frequency doubled vertical-external-cavity surface-emitting laser (VECSEL) with a peak output power of 14 W and emission spectrum near 588 nm. The semiconductor gain chip was grown by molecular beam epitaxy and comprised 10 GaInAs quantum wells. The gain structure was designed to be antiresonant at 1180 nm. The fundamental wavelength was frequency doubled to the yellow-orange spectral range using a 10-mm long critically phase matched lithium triborate nonlinear crystal, situated at the mode waist of the V-shaped laser cavity. The emission spectrum was narrowed down to FWHM of < 0.2 nm by employing a 1.5 mm birefringent filter and a 100-μm-thick etalon inside the cavity. By directly modulating the pump laser of the VECSEL, we were able to produce pulse widths down to 570 ns with average and peak output power of 81 mW and 14 W, respectively. The repetition rate was kept constant at 10 kHz throughout the measurements. The maximum peak power obtained was pump power limited. In comparison, at the same coolant temperature, a maximum of 8.5 W was achieved in continuous wave. The maximum optical-to-optical conversion efficiency (absorbed peak pump power to peak output power) was calculated to be 20-21 %. © 2014 SPIE. KW - Frequency doubling KW - Gain modulation KW - High-efficiency KW - High-power KW - Pulsed KW - SHG KW - Yellow-orange VECSEL UR - http://www.scopus.com/inward/record.url?scp=84902438552&partnerID=8YFLogxK U2 - 10.1117/12.2054716 DO - 10.1117/12.2054716 M3 - Conference contribution SN - 978-1-6284-1090-7 VL - 9134 T3 - SPIE Conference Proceedings BT - Photonics Europe 2014, Semiconductor Lasers and Laser Dynamics VI, April 14-17, 2014, Brussels, Belgium. Proceedings of SPIE PB - SPIE ER - TY - GEN T1 - Ray-based evaluation of dual-polarized MIMO in (Ultra-)dense millimeter-wave urban deployments AU - Solomitckii, Dmitrii AU - Petrov, Vitaly AU - Nikopour, Hosein AU - Akdeniz, Mustafa AU - Orhan, Oner AU - Himayat, Nageen AU - Talwar, Shilpa AU - Andreev, Sergey AU - Koucheryavy, Yevgeni PY - 2018/7/20 Y1 - 2018/7/20 N2 - Dense deployments of millimeter-wave (mmWave) base stations (BSs) are being considered as the most feasible solution to meet the steadily growing data rate demands of mobile users. Accordingly, the achievable performance gains of mmWave-based dense networks in real deployments have to be studied carefully, since mmWave radio technology features specific transceiver, antenna, and propagation properties. In this paper, we contribute an accurate performance evaluation of single- versus dual-polarized MIMO systems operating over the mmWave channel in typical urban scenarios as well as address the impact of device- and network-centric parameters on the performance gains enabled by MIMO in dense to ultra-dense BS deployments. This study relies on our in-house ray-based modeler and takes into account the key mmWave system effects, such as multi-path propagation, utilization of dual-polarized antennas, and characteristic interference models. Our results show that the benefit of using mmWave- MIMO grows with increasing BS density, thus encouraging a further study of this technology especially for (ultra-)dense setups. We also demonstrate that non-coherent non-polarized diffuse scattering component may reduce the capacity gain of dual-polarized vs. single- polarized MIMO. AB - Dense deployments of millimeter-wave (mmWave) base stations (BSs) are being considered as the most feasible solution to meet the steadily growing data rate demands of mobile users. Accordingly, the achievable performance gains of mmWave-based dense networks in real deployments have to be studied carefully, since mmWave radio technology features specific transceiver, antenna, and propagation properties. In this paper, we contribute an accurate performance evaluation of single- versus dual-polarized MIMO systems operating over the mmWave channel in typical urban scenarios as well as address the impact of device- and network-centric parameters on the performance gains enabled by MIMO in dense to ultra-dense BS deployments. This study relies on our in-house ray-based modeler and takes into account the key mmWave system effects, such as multi-path propagation, utilization of dual-polarized antennas, and characteristic interference models. Our results show that the benefit of using mmWave- MIMO grows with increasing BS density, thus encouraging a further study of this technology especially for (ultra-)dense setups. We also demonstrate that non-coherent non-polarized diffuse scattering component may reduce the capacity gain of dual-polarized vs. single- polarized MIMO. U2 - 10.1109/VTCSpring.2018.8417788 DO - 10.1109/VTCSpring.2018.8417788 M3 - Conference contribution SP - 1 EP - 7 BT - 2018 IEEE 87th Vehicular Technology Conference, VTC Spring 2018 - Proceedings PB - IEEE ER - TY - GEN T1 - Real-time depth image-based rendering with layered dis-occlusion compensation and aliasing-free composition AU - Smirnov, Sergey AU - Gotchev, Atanas PY - 2015 Y1 - 2015 N2 - Depth Image-based Rendering (DIBR) is a popular view synthesis technique which utilizes the RGB+D image format, also referred to as view-plus-depth scene representation. Classical DIBR is prone to dis-occlusion artefacts, caused by the lack of information in areas behind foreground objects, which appear visible in the synthesized images. A number of recently proposed compensation techniques have addressed the problem of hole filling. However, their computational complexity does not allow for real-time view synthesis and may require additional user input. In this work, we propose a hole-compensation technique, which works fully automatically and in a perceptually-correct manner. The proposed technique applies a two-layer model of the given RGB+D imagery, which is specifically tailored for rendering with free viewpoint selection. The main two components of the proposed technique are an adaptive layering of depth into relative 'foreground' and 'background' layers to be rendered separately and an additional blending filtering aimed at creating a blending function for aliasing cancellation during the process of view composition. The proposed real-time implementation turns ordinary view-plus-depth images to true 3D scene representations, which allow visualization in the fly-around manner. AB - Depth Image-based Rendering (DIBR) is a popular view synthesis technique which utilizes the RGB+D image format, also referred to as view-plus-depth scene representation. Classical DIBR is prone to dis-occlusion artefacts, caused by the lack of information in areas behind foreground objects, which appear visible in the synthesized images. A number of recently proposed compensation techniques have addressed the problem of hole filling. However, their computational complexity does not allow for real-time view synthesis and may require additional user input. In this work, we propose a hole-compensation technique, which works fully automatically and in a perceptually-correct manner. The proposed technique applies a two-layer model of the given RGB+D imagery, which is specifically tailored for rendering with free viewpoint selection. The main two components of the proposed technique are an adaptive layering of depth into relative 'foreground' and 'background' layers to be rendered separately and an additional blending filtering aimed at creating a blending function for aliasing cancellation during the process of view composition. The proposed real-time implementation turns ordinary view-plus-depth images to true 3D scene representations, which allow visualization in the fly-around manner. U2 - 10.1117/12.2086895 DO - 10.1117/12.2086895 M3 - Conference contribution SN - 9781628414899 T3 - SPIE Conference Proceedings BT - Proceedings of SPIE - The International Society for Optical Engineering PB - SPIE ER - TY - JOUR T1 - Real-time observation of bacterial gene expression noise AU - Anufrieva, Olga AU - Sala, Adrien AU - Yli-Harja, Olli AU - Kandhavelu, Meenakshisundaram PY - 2016/6 Y1 - 2016/6 N2 - 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. AB - 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. KW - Bursty mRNA production KW - Cell cycle KW - Gene expression KW - lac promoter KW - Noise components U2 - 10.1016/j.nancom.2016.03.001 DO - 10.1016/j.nancom.2016.03.001 M3 - Article VL - 8 SP - 68 EP - 75 JO - Nano Communication Networks JF - Nano Communication Networks SN - 1878-7789 ER - TY - JOUR T1 - Relations and bounds for the zeros of graph polynomials using vertex orbits AU - Dehmer, Matthias AU - Emmert-Streib, Frank AU - Mowshowitz, Abbe AU - Ilić, Aleksandar AU - Chen, Zengqiang AU - Yu, Guihai AU - Feng, Lihua AU - Ghorbani, Modjtaba AU - Varmuza, Kurt AU - Tao, Jin PY - 2020/9/1 Y1 - 2020/9/1 N2 - In this paper, we prove bounds for the unique, positive zero of OG ★(z):=1−OG(z), where OG(z) is the so-called orbit polynomial [1]. The orbit polynomial is based on the multiplicity and cardinalities of the vertex orbits of a graph. In [1], we have shown that the unique, positive zero δ ≤ 1 of OG ★(z) can serve as a meaningful measure of graph symmetry. In this paper, we study special graph classes with a specified number of orbits and obtain bounds on the value of δ. AB - In this paper, we prove bounds for the unique, positive zero of OG ★(z):=1−OG(z), where OG(z) is the so-called orbit polynomial [1]. The orbit polynomial is based on the multiplicity and cardinalities of the vertex orbits of a graph. In [1], we have shown that the unique, positive zero δ ≤ 1 of OG ★(z) can serve as a meaningful measure of graph symmetry. In this paper, we study special graph classes with a specified number of orbits and obtain bounds on the value of δ. KW - Data science KW - Graph measures KW - Graphs KW - Networks KW - Quantitative graph theory KW - Symmetry U2 - 10.1016/j.amc.2020.125239 DO - 10.1016/j.amc.2020.125239 M3 - Article VL - 380 JO - Applied Mathematics and Computation JF - Applied Mathematics and Computation SN - 0096-3003 M1 - 125239 ER - TY - JOUR T1 - Restoration of low-dose digital breast tomosynthesis AU - Borges, Lucas R. AU - Azzari, Lucio AU - Bakic, Predrag R. AU - Maidment, Andrew D.A. AU - Vieira, Marcelo A.C. AU - Foi, Alessandro PY - 2018/4/19 Y1 - 2018/4/19 N2 - 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. AB - 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. KW - denoising KW - digital breast tomosynthesis KW - dose reduction KW - variance stabilization U2 - 10.1088/1361-6501/aab2f6 DO - 10.1088/1361-6501/aab2f6 M3 - Article VL - 29 JO - Measurement Science and Technology JF - Measurement Science and Technology SN - 0957-0233 IS - 6 M1 - 064003 ER - TY - JOUR T1 - Robust controllers for regular linear systems with infinite-dimensional exosystems AU - Paunonen, Lassi PY - 2017 Y1 - 2017 N2 - 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. AB - 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. KW - Controller Design KW - Feedback KW - Regular Linear Systems KW - Robust Output Regulation KW - Stability U2 - 10.1137/16M107181X DO - 10.1137/16M107181X M3 - Article VL - 55 SP - 1567 EP - 1597 JO - SIAM Journal on Control and Optimization JF - SIAM Journal on Control and Optimization SN - 0363-0129 IS - 3 ER - TY - JOUR T1 - Robust data reconciliation of combustion variables in multi-fuel fired industrial boilers AU - Korpela, Timo AU - Suominen, Olli AU - Majanne, Yrjö AU - Laukkanen, Ville AU - Lautala, Pentti PY - 2016/7/21 Y1 - 2016/7/21 N2 - 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. AB - 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. KW - Data reconciliation KW - Diagnostics KW - Estimation KW - Gross error detection KW - Monitoring KW - Power plant U2 - 10.1016/j.conengprac.2016.07.002 DO - 10.1016/j.conengprac.2016.07.002 M3 - Article VL - 55 SP - 101 EP - 115 JO - Control Engineering Practice JF - Control Engineering Practice SN - 0967-0661 ER - TY - JOUR T1 - Robust Inference for State-Space Models with Skewed Measurement Noise AU - Nurminen, Henri AU - Ardeshiri, Tohid AU - Piché, Robert AU - Gustafsson, Fredrik PY - 2015/11/1 Y1 - 2015/11/1 N2 - 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. AB - 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. KW - Kalman filter KW - robust filtering KW - RTS smoother KW - skew t KW - skewness KW - t-distribution KW - variational Bayes U2 - 10.1109/LSP.2015.2437456 DO - 10.1109/LSP.2015.2437456 M3 - Article VL - 22 SP - 1898 EP - 1902 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 11 ER - TY - GEN T1 - Robust Regulation of SISO Systems: The Fractional Ideal Approach AU - Laakkonen, Petteri AU - Quadrat, Alban PY - 2015 Y1 - 2015 N2 - We solve the robust regulation problem for single-input single-output plants by using the fractional ideal approach and without assuming the existence of coprime factorizations. In particular, we are able to formulate the famous internal model principle for stabilizable plants which do not necessarily admit coprime factorizations. We are able to give a necessary and suffcient solvability condition for the robust regulation problem, which leads to a design method for a robustly regulating controller. The theory is illustrated by examples. AB - We solve the robust regulation problem for single-input single-output plants by using the fractional ideal approach and without assuming the existence of coprime factorizations. In particular, we are able to formulate the famous internal model principle for stabilizable plants which do not necessarily admit coprime factorizations. We are able to give a necessary and suffcient solvability condition for the robust regulation problem, which leads to a design method for a robustly regulating controller. The theory is illustrated by examples. U2 - 10.1137/1.9781611974072.43 DO - 10.1137/1.9781611974072.43 M3 - Conference contribution SP - 311 EP - 318 BT - Proceedings of the SIAM Conference on Control and Its Applications (CT15) PB - SIAM, Society for Industrial and Applied Mathematics ER - TY - JOUR T1 - Rotation Invariant Texture Description Using Symmetric Dense Microblock Difference AU - Mehta, Rakesh AU - Egiazarian, Karen PY - 2016/6/1 Y1 - 2016/6/1 N2 - 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. AB - 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. KW - image representation KW - local features KW - Rotation invariant features KW - texture classification U2 - 10.1109/LSP.2016.2561311 DO - 10.1109/LSP.2016.2561311 M3 - Article VL - 23 SP - 833 EP - 837 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 6 ER - TY - JOUR T1 - sgnesR T2 - An R package for simulating gene expression data from an underlying real gene network structure considering delay parameters AU - Tripathi, Shailesh AU - Lloyd-Price, Jason AU - Ribeiro, Andre AU - Yli-Harja, Olli AU - Dehmer, Matthias AU - Emmert-Streib, Frank PY - 2017/7/4 Y1 - 2017/7/4 N2 - 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. AB - 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. KW - Gene expression data KW - Gene network KW - Simulation U2 - 10.1186/s12859-017-1731-8 DO - 10.1186/s12859-017-1731-8 M3 - Article VL - 18 JO - BMC Bioinformatics JF - BMC Bioinformatics SN - 1471-2105 IS - 1 M1 - 325 ER - TY - GEN T1 - Short-range supercontinuum based lidar for combustion diagnostics AU - Saleh, Abba AU - Ryczkowski, Piotr AU - Genty, Goery AU - Toivonen, Juha N1 - jufoid=71479 PY - 2019 Y1 - 2019 N2 - We developed a short range Lidar system using a supercontinuum source spectrally tailored to cover the ro-vibrational transition energies of desired components of a flue gas. The system enables simultaneous remote measurements of the gas parameters, like temperature and concentration which play a key role in the performance of combustion power plants. The technique requires only one inspection window and can thus be used in combustion units with limited access. It exploits differential absorption between specific wavelength bands of the gas absorption spectrum. The transmittance of individual wavelength band is derived from the detected backscattered temporal intensity of the supercontinuum pulses. We demonstrate preliminary industrial measurement of water vapor temperature and concentration in a full scale boiler. The technique also enables 3D mapping of temperature and concentration. AB - We developed a short range Lidar system using a supercontinuum source spectrally tailored to cover the ro-vibrational transition energies of desired components of a flue gas. The system enables simultaneous remote measurements of the gas parameters, like temperature and concentration which play a key role in the performance of combustion power plants. The technique requires only one inspection window and can thus be used in combustion units with limited access. It exploits differential absorption between specific wavelength bands of the gas absorption spectrum. The transmittance of individual wavelength band is derived from the detected backscattered temporal intensity of the supercontinuum pulses. We demonstrate preliminary industrial measurement of water vapor temperature and concentration in a full scale boiler. The technique also enables 3D mapping of temperature and concentration. KW - Combustion KW - Diagnostics KW - Lidar KW - Remote sensing KW - Supercontinuum U2 - 10.1117/12.2542720 DO - 10.1117/12.2542720 M3 - Conference contribution T3 - Proceedings of SPIE BT - SPIE Future Sensing Technologies A2 - Kimata, Masafumi A2 - Valenta, Christopher R. PB - SPIE, IEEE ER - TY - GEN T1 - Significance of graph theoretic measures in predicting neuronal network activity AU - Mäki-Marttunen, Tuomo Mikael AU - Acimovic, Jugoslava AU - Ruohonen, Keijo Pellervo AU - Linne, Marja-Leena PY - 2012/2/23 Y1 - 2012/2/23 N2 - One of the most prominent patterns of activity observed in developing cortical neuronal networks in vitro is network-wide spontaneous bursting (Wagenaar et al. 2005). In this work, we study computationally the spontaneous emergence of bursts and the effect of network structure on burst shape and frequency. Recent computational structure-function approaches show the effect of, e.g., second-order connections (Zhao et al. 2011) and degree distribution widths (Roxin 2011) on activity patterns. We aim to study a wider set of graph-theoretical measures using networks with identical in-degree distributions. We apply a biophysically plausible point-neuron model of a cortical cell (Golomb et al. 2006). The model network consists of a small (N=100) number of neurons, both excitatory pyramidal neurons and inhibitory interneurons. A model of short-term depression (Golomb and Amitai 1997) is used for glutamatergic synapses. The activity simulation is run over a wide set of classes of network structure. To quantify the structure of the network, we consider graph theoretical measures such as clustering coefficient, geodesic path length, node-betweenness and occurrence of different motifs. We restrict to unweighted bidirectional graph representation, hence the synaptic weights between the neurons are uniform. We study the significance of different graph theoretic measures using a prediction framework: How well can a bursting property, such as burst duration or frequency, be estimated using various measures of structure as attributes? We show that the prediction of bursting properties is improved by taking one or more of the aforementioned measures as prediction attributes. It is best improved when the prediction is based on the clustering coefficient or occurrence of the most highly connected motifs. We confirm the results using a noise-driven LIF model with short-term depression (Tsodyks et al. 2000). We conclude that the significance of measures of clustering is prominent compared to other measures of structure. AB - One of the most prominent patterns of activity observed in developing cortical neuronal networks in vitro is network-wide spontaneous bursting (Wagenaar et al. 2005). In this work, we study computationally the spontaneous emergence of bursts and the effect of network structure on burst shape and frequency. Recent computational structure-function approaches show the effect of, e.g., second-order connections (Zhao et al. 2011) and degree distribution widths (Roxin 2011) on activity patterns. We aim to study a wider set of graph-theoretical measures using networks with identical in-degree distributions. We apply a biophysically plausible point-neuron model of a cortical cell (Golomb et al. 2006). The model network consists of a small (N=100) number of neurons, both excitatory pyramidal neurons and inhibitory interneurons. A model of short-term depression (Golomb and Amitai 1997) is used for glutamatergic synapses. The activity simulation is run over a wide set of classes of network structure. To quantify the structure of the network, we consider graph theoretical measures such as clustering coefficient, geodesic path length, node-betweenness and occurrence of different motifs. We restrict to unweighted bidirectional graph representation, hence the synaptic weights between the neurons are uniform. We study the significance of different graph theoretic measures using a prediction framework: How well can a bursting property, such as burst duration or frequency, be estimated using various measures of structure as attributes? We show that the prediction of bursting properties is improved by taking one or more of the aforementioned measures as prediction attributes. It is best improved when the prediction is based on the clustering coefficient or occurrence of the most highly connected motifs. We confirm the results using a noise-driven LIF model with short-term depression (Tsodyks et al. 2000). We conclude that the significance of measures of clustering is prominent compared to other measures of structure. M3 - Conference contribution SP - 55 EP - 55 BT - Proceedings of The 9th annual Computational and Systems Neuroscience meeting (COSYNE 2012) CY - Salt Lake City ER - TY - GEN T1 - Simultenious binary hash and features learning for image retrieval AU - Frantc, V. A. AU - Makov, S. V. AU - Voronin, V. V. AU - Marchuk, V. I. AU - Semenishchev, E. A. AU - Egiazarian, K. O. AU - Agaian, S. PY - 2016 Y1 - 2016 N2 - Content-based image retrieval systems have plenty of applications in modern world. The most important one is the image search by query image or by semantic description. Approaches to this problem are employed in personal photo-collection management systems, web-scale image search engines, medical systems, etc. Automatic analysis of large unlabeled image datasets is virtually impossible without satisfactory image-retrieval technique. It's the main reason why this kind of automatic image processing has attracted so much attention during recent years. Despite rather huge progress in the field, semantically meaningful image retrieval still remains a challenging task. The main issue here is the demand to provide reliable results in short amount of time. This paper addresses the problem by novel technique for simultaneous learning of global image features and binary hash codes. Our approach provide mapping of pixel-based image representation to hash-value space simultaneously trying to save as much of semantic image content as possible. We use deep learning methodology to generate image description with properties of similarity preservation and statistical independence. The main advantage of our approach in contrast to existing is ability to fine-tune retrieval procedure for very specific application which allow us to provide better results in comparison to general techniques. Presented in the paper framework for data- dependent image hashing is based on use two different kinds of neural networks: convolutional neural networks for image description and autoencoder for feature to hash space mapping. Experimental results confirmed that our approach has shown promising results in compare to other state-of-the-art methods. AB - Content-based image retrieval systems have plenty of applications in modern world. The most important one is the image search by query image or by semantic description. Approaches to this problem are employed in personal photo-collection management systems, web-scale image search engines, medical systems, etc. Automatic analysis of large unlabeled image datasets is virtually impossible without satisfactory image-retrieval technique. It's the main reason why this kind of automatic image processing has attracted so much attention during recent years. Despite rather huge progress in the field, semantically meaningful image retrieval still remains a challenging task. The main issue here is the demand to provide reliable results in short amount of time. This paper addresses the problem by novel technique for simultaneous learning of global image features and binary hash codes. Our approach provide mapping of pixel-based image representation to hash-value space simultaneously trying to save as much of semantic image content as possible. We use deep learning methodology to generate image description with properties of similarity preservation and statistical independence. The main advantage of our approach in contrast to existing is ability to fine-tune retrieval procedure for very specific application which allow us to provide better results in comparison to general techniques. Presented in the paper framework for data- dependent image hashing is based on use two different kinds of neural networks: convolutional neural networks for image description and autoencoder for feature to hash space mapping. Experimental results confirmed that our approach has shown promising results in compare to other state-of-the-art methods. KW - autoencoder KW - content{based image retrieval KW - deep convolutional neural network KW - semantic hashing U2 - 10.1117/12.2223605 DO - 10.1117/12.2223605 M3 - Conference contribution T3 - SPIE Conference Proceedings BT - Mobile Multimedia/Image Processing, Security, and Applications 2016 PB - SPIE ER - TY - GEN T1 - Single exposure lensless subpixel phase imaging AU - Kocsis, Péter AU - Shevkunov, Igor AU - Katkovnik, Vladimir AU - Egiazarian, Karen PY - 2019 Y1 - 2019 N2 - Lensless phase-retrieval system with phase modulation of free propagation wavefront is proposed. Contrary to the traditional super-resolution phase-retrieval, the method in this paper requires a single observation only and uses advanced SR-SPAR iterative technique. Successful object imaging relies on modulation of the object wavefront with a random phase-mask, which generates enlarged intensity patterns, allowing us to extract more information than it is possible without such a mask. The achieved high-quality super-resolution phase-imaging is demonstrated by simulation-tests produced with the parameters corresponding to the physical prototype of the considered optical system. AB - Lensless phase-retrieval system with phase modulation of free propagation wavefront is proposed. Contrary to the traditional super-resolution phase-retrieval, the method in this paper requires a single observation only and uses advanced SR-SPAR iterative technique. Successful object imaging relies on modulation of the object wavefront with a random phase-mask, which generates enlarged intensity patterns, allowing us to extract more information than it is possible without such a mask. The achieved high-quality super-resolution phase-imaging is demonstrated by simulation-tests produced with the parameters corresponding to the physical prototype of the considered optical system. KW - Diffractive optical element KW - Lensless imaging KW - Lensless system design KW - Phase imaging KW - Phase measurement KW - Phase retrieval KW - Sparse representation KW - Sub-pixel resolution U2 - 10.1117/12.2525679 DO - 10.1117/12.2525679 M3 - Conference contribution T3 - Proceedings of SPIE - The International Society for Optical Engineering BT - Digital Optical Technologies 2019 A2 - Kress, Bernard C. A2 - Schelkens, Peter PB - SPIE, IEEE ER - TY - JOUR T1 - Solutions to integrals involving the marcum Q-function and applications AU - Sofotasios, Paschalis C. AU - Muhaidat, Sami AU - Karagiannidis, George K. AU - Sharif, Bayan S. PY - 2015/10/1 Y1 - 2015/10/1 N2 - 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. AB - 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. U2 - 10.1109/LSP.2015.2432064 DO - 10.1109/LSP.2015.2432064 M3 - Article VL - 22 SP - 1752 EP - 1756 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 10 ER - TY - JOUR T1 - Sparse Overcomplete Denoising T2 - Aggregation Versus Global Optimization AU - Carrera, Diego AU - Boracchi, Giacomo AU - Foi, Alessandro AU - Wohlberg, Brendt N1 - EXT="Carrera, Diego" EXT="Boracchi, Giacomo" PY - 2017/10/1 Y1 - 2017/10/1 N2 - 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. AB - 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. KW - Convolutional sparse coding KW - denoising KW - overcomplete representations KW - sparse representations U2 - 10.1109/LSP.2017.2734119 DO - 10.1109/LSP.2017.2734119 M3 - Article VL - 24 SP - 1468 EP - 1472 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 10 ER - TY - JOUR T1 - Spatial Interpolation of Cyclostationary Test Statistics in Cognitive Radio Networks T2 - Methods and Field Measurements AU - Chaudhari, Sachin AU - Kosunen, Marko AU - Mäkinen, Semu AU - Chandrasekaran, Ramanathan AU - Oksanen, Jan AU - Laatta, Markus AU - Ryynänen, Jussi AU - Koivunen, Visa AU - Valkama, Mikko PY - 2018 Y1 - 2018 N2 - 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. AB - 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. KW - Cognitive radio KW - cyclostationary detection KW - Databases KW - Detectors KW - energy detection KW - Hardware KW - Interference KW - Interpolation KW - Kriging KW - Mobile communication KW - radio environment map KW - spatial estimation KW - spectrum sensing U2 - 10.1109/TVT.2017.2717379 DO - 10.1109/TVT.2017.2717379 M3 - Article VL - 67 SP - 1113 EP - 1129 JO - IEEE Transactions on Vehicular Technology JF - IEEE Transactions on Vehicular Technology SN - 0018-9545 IS - 2 ER - TY - JOUR T1 - Spectral modeling of time series with missing data AU - Rodrigues, Paulo C. AU - de Carvalho, Miguel PY - 2013/4/1 Y1 - 2013/4/1 N2 - 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. AB - 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. KW - Karhunen-Loève decomposition KW - Missing data KW - Singular spectrum analysis KW - Time series analysis UR - http://www.scopus.com/inward/record.url?scp=84872620531&partnerID=8YFLogxK U2 - 10.1016/j.apm.2012.09.040 DO - 10.1016/j.apm.2012.09.040 M3 - Article VL - 37 SP - 4676 EP - 4684 JO - Applied Mathematical Modelling JF - Applied Mathematical Modelling SN - 0307-904X IS - 7 ER - TY - JOUR T1 - Stabilization to trajectories for parabolic equations AU - Phan, Duy AU - Rodrigues, Sérgio S. PY - 2018/6/1 Y1 - 2018/6/1 N2 - 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. AB - 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. KW - Feedback stabilization to trajectories KW - Semilinear parabolic equations U2 - 10.1007/s00498-018-0218-0 DO - 10.1007/s00498-018-0218-0 M3 - Article VL - 30 JO - Mathematics of Control Signals and Systems JF - Mathematics of Control Signals and Systems SN - 0932-4194 IS - 2 M1 - 11 ER - TY - JOUR T1 - State Estimation for a Class of Piecewise Affine State-Space Models AU - Rui, Rafael AU - Ardeshiri, Tohid AU - Nurminen, Henri AU - Bazanella, Alexandre AU - Gustafsson, Fredrik PY - 2017/1 Y1 - 2017/1 N2 - 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. AB - 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. KW - piecewise affine KW - state-space models KW - nonlinear filtering KW - Kalman filtering U2 - 10.1109/LSP.2016.2633624 DO - 10.1109/LSP.2016.2633624 M3 - Article VL - 24 SP - 61 EP - 65 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 1 ER - TY - JOUR T1 - Still image/video frame lossy compression providing a desired visual quality AU - Zemliachenko, Alexander AU - Lukin, Vladimir AU - Ponomarenko, Nikolay AU - Egiazarian, Karen AU - Astola, Jaakko PY - 2016 Y1 - 2016 N2 - 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. AB - 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. KW - Compression ratio KW - Lossy compression KW - Required quality KW - Visual quality metrics UR - http://www.scopus.com/inward/record.url?scp=84930357751&partnerID=8YFLogxK U2 - 10.1007/s11045-015-0333-8 DO - 10.1007/s11045-015-0333-8 M3 - Article VL - 27 SP - 697 EP - 718 JO - Multidimensional Systems and Signal Processing JF - Multidimensional Systems and Signal Processing SN - 0923-6082 IS - 3 ER - TY - JOUR T1 - Structural influence of gene networks on their inference T2 - Analysis of C3NET AU - Altay, Gökmen AU - Emmert-Streib, Frank PY - 2011/6/22 Y1 - 2011/6/22 N2 - 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. AB - 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. UR - http://www.scopus.com/inward/record.url?scp=79959327654&partnerID=8YFLogxK U2 - 10.1186/1745-6150-6-31 DO - 10.1186/1745-6150-6-31 M3 - Article VL - 6 JO - Biology Direct JF - Biology Direct SN - 1745-6150 M1 - 31 ER - TY - JOUR T1 - Structural Measures for Network Biology Using QuACN AU - Mueller, Laurin A. J. AU - Kugler, Karl G. AU - Graber, Armin AU - Emmert-Streib, Frank AU - Dehmer, Matthias PY - 2011/12/24 Y1 - 2011/12/24 N2 - 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. AB - 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. UR - http://www.scopus.com/inward/record.url?scp=84155173344&partnerID=8YFLogxK U2 - 10.1186/1471-2105-12-492 DO - 10.1186/1471-2105-12-492 M3 - Article VL - 12 JO - BMC Bioinformatics JF - BMC Bioinformatics SN - 1471-2105 IS - 1 M1 - 492 ER - TY - JOUR T1 - Structural Results for Quaternionic Gabor Frames AU - Cerejeiras, Paula AU - Hartmann, Stefan AU - Orelma, Heikki PY - 2018/11/1 Y1 - 2018/11/1 N2 - 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. AB - 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. KW - Frame bounds KW - Janssen’s representation KW - Quaternionic frame operator KW - Quaternionic Gabor frames KW - Two-sided QWFT KW - Wexler–Raz biorthogonality U2 - 10.1007/s00006-018-0901-8 DO - 10.1007/s00006-018-0901-8 M3 - Article VL - 28 JO - Advances in Applied Clifford Algebras JF - Advances in Applied Clifford Algebras SN - 0188-7009 IS - 5 M1 - 86 ER - TY - GEN T1 - Structural Similarity Index with Predictability of Image Blocks AU - Ponomarenko, Mykola AU - Egiazarian, Karen AU - Lukin, Vladimir AU - Abramova, Victoriya N1 - JUFOID=72887 EXT="Lukin, Vladimir" PY - 2018/9/10 Y1 - 2018/9/10 N2 - Structural similarity index (SSIM) is a widely used full-reference metric for assessment of visual quality of images and remote sensing data. It is calculated in a block-wise manner and is based on multiplication of three components: similarity of means of image blocks, similarity of contrasts and a correlation factor. In this paper, two modifications of SSIM are proposed. First, a fourth multiplicative component is introduced to SSIM (thus obtaining SSIM4) that describes a similarity of predictability of image blocks. A predictability for a given block is calculated as a minimal value of mean square error between the considered block and the neighboring blocks. Second, a simple scheme for calculating the metrics SSIM and SSIM4 for color images is proposed and optimized. Effectiveness of the proposed modifications is confirmed for the specialized image databases TID2013, LIVE, and FLT. In particular, the Spearman rank order correlation coefficient (SROCC) for the recently introduced FLT Database, calculated between the proposed metric color SSIM4 and mean opinion scores (MOS), has reached the value 0.85 (the best result for all compared metrics) whilst for SSIM it is equal to 0.58. AB - Structural similarity index (SSIM) is a widely used full-reference metric for assessment of visual quality of images and remote sensing data. It is calculated in a block-wise manner and is based on multiplication of three components: similarity of means of image blocks, similarity of contrasts and a correlation factor. In this paper, two modifications of SSIM are proposed. First, a fourth multiplicative component is introduced to SSIM (thus obtaining SSIM4) that describes a similarity of predictability of image blocks. A predictability for a given block is calculated as a minimal value of mean square error between the considered block and the neighboring blocks. Second, a simple scheme for calculating the metrics SSIM and SSIM4 for color images is proposed and optimized. Effectiveness of the proposed modifications is confirmed for the specialized image databases TID2013, LIVE, and FLT. In particular, the Spearman rank order correlation coefficient (SROCC) for the recently introduced FLT Database, calculated between the proposed metric color SSIM4 and mean opinion scores (MOS), has reached the value 0.85 (the best result for all compared metrics) whilst for SSIM it is equal to 0.58. KW - image visual quality assessment KW - masking of unpredictable energy U2 - 10.1109/MMET.2018.8460285 DO - 10.1109/MMET.2018.8460285 M3 - Conference contribution SN - 9781538654385 VL - 2018-July SP - 115 EP - 118 BT - 2018 IEEE 17th International Conference on Mathematical Methods in Electromagnetic Theory, MMET 2018 - Proceedings PB - IEEE COMPUTER SOCIETY PRESS ER - TY - JOUR T1 - Structural similarity of directed universal hierarchical graphs T2 - A low computational complexity approach AU - Dehmer, Matthias AU - Emmert-Streib, Frank PY - 2007/12/1 Y1 - 2007/12/1 N2 - 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. AB - 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. KW - Complexity analysis KW - Graph classes KW - Graph classification KW - Graph similarity KW - Hierarchical models KW - Structured objects UR - http://www.scopus.com/inward/record.url?scp=35648968162&partnerID=8YFLogxK U2 - 10.1016/j.amc.2007.04.006 DO - 10.1016/j.amc.2007.04.006 M3 - Article VL - 194 SP - 7 EP - 20 JO - Applied Mathematics and Computation JF - Applied Mathematics and Computation SN - 0096-3003 IS - 1 ER - TY - GEN T1 - Switchable unidirectional second-harmonic emission through GaAs nanoantennas AU - Xu, Lei AU - Saerens, Grégoire AU - Timofeeva, Maria AU - Miroshnichenko, Andrey E. AU - Camacho-Morales, Rocio AU - Volkovskaya, Irina AU - Smirnova, Daria A. AU - Lysevych, Mykhaylo AU - Huang, Lujun AU - Cai, Marcus AU - Karouta, Fouad AU - Hoe Tan, H. AU - Kauranen, Martti AU - Jagadish, Chennupati AU - Grange, Rachel AU - Neshev, Dragomir N. AU - Rahmani, Mohsen N1 - jufoid=71479 PY - 2019 Y1 - 2019 N2 - Switching the scattering direction of high-index dielectric nanoantennas between forward and backward, via Mie resonances in the linear regime, has been widely studied, recently. However, switching the harmonic emission of nanoantennas without applying any physical change to the antennas, such as geometry, or environment, is a chal-lenging task that has not been demonstrated yet. Here, we investigate multipolar second-harmonic switch from GaAs nanoantennas. Based on the peculiar nonlinearities of zinc-blende semiconductors, we demonstrate both theoretically and experimentally unidirectional nonlinear emission routing and switching via pump polarization control. Our results offer exciting opportunities for nonlinear nanophotonics technologies, such as nanoscale light routing elements, nonlinear light sources, nonlinear imaging, multifunctional flat optical elements. AB - Switching the scattering direction of high-index dielectric nanoantennas between forward and backward, via Mie resonances in the linear regime, has been widely studied, recently. However, switching the harmonic emission of nanoantennas without applying any physical change to the antennas, such as geometry, or environment, is a chal-lenging task that has not been demonstrated yet. Here, we investigate multipolar second-harmonic switch from GaAs nanoantennas. Based on the peculiar nonlinearities of zinc-blende semiconductors, we demonstrate both theoretically and experimentally unidirectional nonlinear emission routing and switching via pump polarization control. Our results offer exciting opportunities for nonlinear nanophotonics technologies, such as nanoscale light routing elements, nonlinear light sources, nonlinear imaging, multifunctional flat optical elements. KW - Dielectric nanoresonators KW - Mie resonance KW - Second harmonic generation KW - Unidirectional emission U2 - 10.1117/12.2539887 DO - 10.1117/12.2539887 M3 - Conference contribution T3 - Proceedings of SPIE - The International Society for Optical Engineering BT - AOS Australian Conference on Optical Fibre Technology, ACOFT 2019 and Australian Conference on Optics, Lasers, and Spectroscopy, ACOLS 2019 A2 - Mitchell, Arnan A2 - Rubinsztein-Dunlop, Halina PB - SPIE ER - TY - GEN T1 - Tailoring directional scattering of second-harmonic generation from (111)-GaAs nanoantennas AU - Sautter, J. AU - Xu, L. AU - Miroshnichenko, A. AU - Lysevych, M. AU - Volkovskaya, I. AU - Smirnova, D. AU - Camacho Morales, M. AU - Zangeneh Kamali, K. AU - Karouta, F. AU - Vora, K. AU - Tan, H. H. AU - Kauranen, M. AU - Staude, I. AU - Jagadish, C. AU - Neshev, D. N. AU - Rahmani, M. N1 - jufoid=71479 PY - 2019 Y1 - 2019 N2 - The group of zincblende III-V compound semiconductors, especially (100)-grown AlGaAs and GaAs, have recently been presented as promising materials for second harmonic generation (SHG) at the nanoscale. However, major obstacles to push the technology towards practical applications are the limited control over directionality of the SH emission and especially zero forward/backward radiation. In this work we provide both theoretically and experimentally a solution to these problems by presenting the first SHG nanoantennas made from (111)-GaAs embedded in a low index material. These nanoantennas show superior forward directionality compared to their (100)-counterparts. Most importantly, it is possible to manipulate the SHG radiation pattern of the nanoantennas by changing the pump polarization without affecting the linear properties and the total nonlinear conversion efficiency. AB - The group of zincblende III-V compound semiconductors, especially (100)-grown AlGaAs and GaAs, have recently been presented as promising materials for second harmonic generation (SHG) at the nanoscale. However, major obstacles to push the technology towards practical applications are the limited control over directionality of the SH emission and especially zero forward/backward radiation. In this work we provide both theoretically and experimentally a solution to these problems by presenting the first SHG nanoantennas made from (111)-GaAs embedded in a low index material. These nanoantennas show superior forward directionality compared to their (100)-counterparts. Most importantly, it is possible to manipulate the SHG radiation pattern of the nanoantennas by changing the pump polarization without affecting the linear properties and the total nonlinear conversion efficiency. KW - Dielectric nanoantennas KW - Directional emission KW - Multipolar interference KW - Second harmonic generation U2 - 10.1117/12.2539086 DO - 10.1117/12.2539086 M3 - Conference contribution T3 - Proceedings of SPIE - The International Society for Optical Engineering BT - AOS Australian Conference on Optical Fibre Technology, ACOFT 2019 and Australian Conference on Optics, Lasers, and Spectroscopy, ACOLS 2019 A2 - Mitchell, Arnan A2 - Rubinsztein-Dunlop, Halina PB - SPIE ER - TY - JOUR T1 - Target tracking via combination of particle filter and optimisation techniques AU - Hosseini, Seyyed Soheil Sadat AU - Jamali, Mohsin M. AU - Astola, Jaakko AU - Gorsevski, Peter V. PY - 2016 Y1 - 2016 N2 - 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. AB - 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. KW - Differential evolution KW - Nelder-Mead KW - Particle filter KW - Particle swarm optimisation KW - Pattern search KW - PSO KW - Target tracking U2 - 10.1504/IJMMNO.2016.077068 DO - 10.1504/IJMMNO.2016.077068 M3 - Article VL - 7 SP - 212 EP - 229 JO - International Journal of Mathematical Modelling and Numerical Optimization JF - International Journal of Mathematical Modelling and Numerical Optimization SN - 2040-3607 IS - 2 ER - TY - GEN T1 - The different levels of magneto-mechanical coupling in energy conversion machines and devices AU - Belahcen, A. AU - Kouhia, R. AU - Fonteyn, K. PY - 2011 Y1 - 2011 N2 - This paper reviews the methods for coupling the magnetic and mechanical problems in magnetic materials and their application to electrical machines. The reviewed methods include both the material models and the computing methods as well as the methods for computing the magnetic forces. The paper shows that there are different levels of coupling the magnetic system with the mechanical one and that the use of a method or another depends on the application and the level of accuracy aimed at. The paper also clarifies some terms and concepts related to the coupling terminology such as strong, weak, local, global, direct and indirect coupling and put these terms in a coherent context. Most of the examples are related to the two dimensional analysis but some three dimensional ones are also shown. AB - This paper reviews the methods for coupling the magnetic and mechanical problems in magnetic materials and their application to electrical machines. The reviewed methods include both the material models and the computing methods as well as the methods for computing the magnetic forces. The paper shows that there are different levels of coupling the magnetic system with the mechanical one and that the use of a method or another depends on the application and the level of accuracy aimed at. The paper also clarifies some terms and concepts related to the coupling terminology such as strong, weak, local, global, direct and indirect coupling and put these terms in a coherent context. Most of the examples are related to the two dimensional analysis but some three dimensional ones are also shown. KW - Computing Methods KW - Coupled problems KW - Electrical machines KW - Magnetic forces KW - Magneto-mechanics KW - Magnetostriction UR - http://www.scopus.com/inward/record.url?scp=84857432902&partnerID=8YFLogxK M3 - Conference contribution SN - 9788489925786 SP - 472 EP - 483 BT - Proceedings of the 4th International Conference on Computational Methods for Coupled Problems in Science and Engineering, COUPLED PROBLEMS 2011 ER - TY - JOUR T1 - The Impact of Interference from the Side Lanes on mmWave/THz Band V2V Communication Systems with Directional Antennas AU - Petrov, Vitaly AU - Kokkoniemi, Joonas AU - Moltchanov, Dmitri AU - Lehtomaki, Janne AU - Juntti, Markku AU - Koucheryavy, Yevgeni PY - 2018/6 Y1 - 2018/6 N2 - 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. AB - 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. KW - Analytical models KW - Antenna measurements KW - Communication systems KW - Directional antennas KW - Interference KW - Millimeter waves KW - Propagation losses KW - Road transportation KW - SIR KW - THz band KW - Vehicle-to-Vehicle communications U2 - 10.1109/TVT.2018.2799564 DO - 10.1109/TVT.2018.2799564 M3 - Article VL - 67 SP - 5028 EP - 5041 JO - IEEE Transactions on Vehicular Technology JF - IEEE Transactions on Vehicular Technology SN - 0018-9545 IS - 6 ER - TY - GEN T1 - The magical world of metamaterials AU - Caglayan, Humeyra AU - Ozbay, Ekmel N1 - EXT="Caglayan, Humeyra" PY - 2009 Y1 - 2009 N2 - We review experimental and theoretical studies performed on left-handed metamaterials (LHM). The metamaterials exhibit quiet unusual electromagnetic properties such as negative refraction, negative phase velocity, subwavelength focusing, subwavelength cavities and enhanced transmission. AB - We review experimental and theoretical studies performed on left-handed metamaterials (LHM). The metamaterials exhibit quiet unusual electromagnetic properties such as negative refraction, negative phase velocity, subwavelength focusing, subwavelength cavities and enhanced transmission. KW - Left-handed metamaterial KW - Metamaterials KW - Negative refractive index KW - Superlens UR - http://www.scopus.com/inward/record.url?scp=70349983117&partnerID=8YFLogxK U2 - 10.1117/12.821407 DO - 10.1117/12.821407 M3 - Conference contribution SN - 9780819476401 VL - 7366 T3 - Proceedings of SPIE BT - Photonic Materials, Devices, and Applications III ER - TY - GEN T1 - Thermal effects on a passive wireless antenna sensor for strain and crack sensing AU - Yi, Xiaohua AU - Vyas, Rushi AU - Cho, Chunhee AU - Fang, Chia Hung AU - Cooper, James AU - Wang, Yang AU - Leon, Roberto T. AU - Tentzeris, Manos M. PY - 2012 Y1 - 2012 N2 - For application in structural health monitoring, a folded patch antenna has been previously designed as a wireless sensor that monitors strain and crack in metallic structures. Resonance frequency of the RFID patch antenna is closely related with its dimension. To measure stress concentration in a base structure, the sensor is bonded to the structure like a traditional strain gage. When the antenna sensor is under strain/deformation together with the base structure, the antenna resonance frequency varies accordingly. The strain-related resonance frequency variation is wirelessly interrogated and recorded by a reader, and can be used to derive strain/deformation. Material properties of the antenna components can have significant effects on sensor performance. This paper investigates thermal effects through both numerical simulation and temperature chamber testing. When temperature fluctuates, previous sensor design (with a glass microfiber-reinforced PTFE substrate) shows relatively large variation in resonance frequency. To improve sensor performance, a new ceramic-filled PTFE substrate material is chosen for re-designing the antenna sensor. Temperature chamber experiments are also conducted to the sensor with new substrate material, and compared with previous design. AB - For application in structural health monitoring, a folded patch antenna has been previously designed as a wireless sensor that monitors strain and crack in metallic structures. Resonance frequency of the RFID patch antenna is closely related with its dimension. To measure stress concentration in a base structure, the sensor is bonded to the structure like a traditional strain gage. When the antenna sensor is under strain/deformation together with the base structure, the antenna resonance frequency varies accordingly. The strain-related resonance frequency variation is wirelessly interrogated and recorded by a reader, and can be used to derive strain/deformation. Material properties of the antenna components can have significant effects on sensor performance. This paper investigates thermal effects through both numerical simulation and temperature chamber testing. When temperature fluctuates, previous sensor design (with a glass microfiber-reinforced PTFE substrate) shows relatively large variation in resonance frequency. To improve sensor performance, a new ceramic-filled PTFE substrate material is chosen for re-designing the antenna sensor. Temperature chamber experiments are also conducted to the sensor with new substrate material, and compared with previous design. KW - Crack sensor KW - Folded patch antenna KW - Passive wireless sensor KW - RFID KW - Strain sensor KW - Thermal effect UR - http://www.scopus.com/inward/record.url?scp=84861112128&partnerID=8YFLogxK U2 - 10.1117/12.914833 DO - 10.1117/12.914833 M3 - Conference contribution SN - 9780819490025 VL - 8345 BT - Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2012 ER - TY - JOUR T1 - The watching system as a generalization of identifying code AU - Ghorbani, Modjtaba AU - Dehmer, Matthias AU - Maimani, Hamidreza AU - Maddah, Sheyda AU - Roozbayani, Maryam AU - Emmert-Streib, Frank PY - 2020 Y1 - 2020 N2 - 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. AB - 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. KW - Domination number KW - Graph products KW - Identifying code KW - Watching system U2 - 10.1016/j.amc.2020.125302 DO - 10.1016/j.amc.2020.125302 M3 - Article VL - 380 JO - Applied Mathematics and Computation JF - Applied Mathematics and Computation SN - 0096-3003 M1 - 125302 ER - TY - GEN T1 - Thickness variation study of RFID-based folded patch antennas for strain sensing AU - Yi, Xiaohua AU - Wu, Terence AU - Lantz, Gabriel AU - Wang, Yang AU - Leon, Roberto T. AU - Tentzeris, Manos M. PY - 2011 Y1 - 2011 N2 - This paper explores folded patch antennas for the development of low-cost and wireless smart-skin sensors that monitor the strain in metallic structures. When the patch antenna is under strain/deformation, its resonance frequency varies accordingly. The variation can be easily interrogated and recorded by a wireless reader that also provides power for the antenna operation. The patch antenna adopts a specially selected substrate material with low dielectric constant, as well as an inexpensive off-the-shelf radiofrequency identification (RFID) chip for signal modulation. A thicker substrate increases RFID signal-to-noise ratio, but reduces the strain transfer efficiency. To experimentally study the effect of substrate thickness, two prototype folded patch antennas with different substrate thicknesses have been designed and manufactured. For both prototypes, tensile testing results show strong linearity between the interrogated resonance frequency and the strain experienced by the antenna. Longer interrogation range is achieved with the larger substrate thickness. AB - This paper explores folded patch antennas for the development of low-cost and wireless smart-skin sensors that monitor the strain in metallic structures. When the patch antenna is under strain/deformation, its resonance frequency varies accordingly. The variation can be easily interrogated and recorded by a wireless reader that also provides power for the antenna operation. The patch antenna adopts a specially selected substrate material with low dielectric constant, as well as an inexpensive off-the-shelf radiofrequency identification (RFID) chip for signal modulation. A thicker substrate increases RFID signal-to-noise ratio, but reduces the strain transfer efficiency. To experimentally study the effect of substrate thickness, two prototype folded patch antennas with different substrate thicknesses have been designed and manufactured. For both prototypes, tensile testing results show strong linearity between the interrogated resonance frequency and the strain experienced by the antenna. Longer interrogation range is achieved with the larger substrate thickness. KW - folded patch antenna KW - passive wireless sensor KW - RFID KW - strain sensor KW - substrate thickness UR - http://www.scopus.com/inward/record.url?scp=79956325124&partnerID=8YFLogxK U2 - 10.1117/12.879868 DO - 10.1117/12.879868 M3 - Conference contribution SN - 9780819485434 VL - 7981 BT - Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2011 ER - TY - JOUR T1 - Topological mappings between graphs, trees and generalized trees AU - Emmert-Streib, Frank AU - Dehmer, Matthias PY - 2007/3/15 Y1 - 2007/3/15 N2 - 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. AB - 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. KW - Applied graph theory KW - Graph transformation KW - Hierarchical graphs UR - http://www.scopus.com/inward/record.url?scp=33947616843&partnerID=8YFLogxK U2 - 10.1016/j.amc.2006.07.162 DO - 10.1016/j.amc.2006.07.162 M3 - Article VL - 186 SP - 1326 EP - 1333 JO - Applied Mathematics and Computation JF - Applied Mathematics and Computation SN - 0096-3003 IS - 2 ER - TY - GEN T1 - Towards Algebraic Modeling of GPU Memory Access for Bank Conflict Mitigation AU - Ferranti, Luca AU - Boutellier, Jani N1 - INT=comp,"Ferranti, Luca" PY - 2019/10/1 Y1 - 2019/10/1 N2 - Graphics Processing Units (GPU) have been widely used in various fields of scientific computing, such as in signal processing. GPUs have a hierarchical memory structure with memory layers that are shared between GPU processing elements. Partly due to the complex memory hierarchy, GPU programming is non-Trivial, and several aspects must be taken into account, one being memory access patterns. One of the fastest GPU memory layers, shared memory, is grouped into banks to enable fast, parallel access for processing elements. Unfortunately, it may happen that multiple threads of a GPU program may access the same shared memory bank simultaneously causing a bank conflict. If this happens, program execution slows down as memory accesses have to be rescheduled to determine which instruction to execute first. Bank conflicts are not taken into account automatically by the compiler, and hence the programmer must detect and deal with them prior to program execution. In this paper, we present an algebraic approach to detect bank conflicts and prove some theoretical results that can be used to predict when bank conflicts happen and how to avoid them. Also, our experimental results illustrate the savings in computation time. AB - Graphics Processing Units (GPU) have been widely used in various fields of scientific computing, such as in signal processing. GPUs have a hierarchical memory structure with memory layers that are shared between GPU processing elements. Partly due to the complex memory hierarchy, GPU programming is non-Trivial, and several aspects must be taken into account, one being memory access patterns. One of the fastest GPU memory layers, shared memory, is grouped into banks to enable fast, parallel access for processing elements. Unfortunately, it may happen that multiple threads of a GPU program may access the same shared memory bank simultaneously causing a bank conflict. If this happens, program execution slows down as memory accesses have to be rescheduled to determine which instruction to execute first. Bank conflicts are not taken into account automatically by the compiler, and hence the programmer must detect and deal with them prior to program execution. In this paper, we present an algebraic approach to detect bank conflicts and prove some theoretical results that can be used to predict when bank conflicts happen and how to avoid them. Also, our experimental results illustrate the savings in computation time. KW - block matching KW - Graphics processing units KW - memory hierarchy KW - OpenCL U2 - 10.1109/SiPS47522.2019.9020385 DO - 10.1109/SiPS47522.2019.9020385 M3 - Conference contribution SP - 103 EP - 108 BT - 2019 IEEE International Workshop on Signal Processing Systems, SiPS 2019 PB - IEEE ER - TY - JOUR T1 - Transmit Power Optimization and Feasibility Analysis of Self-backhauling Full-Duplex Radio Access Systems AU - Korpi, Dani AU - Riihonen, Taneli AU - Sabharwal, Ashutosh AU - Valkama, Mikko PY - 2018 Y1 - 2018 N2 - 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. AB - 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. KW - full-duplex wireless KW - massive MIMO KW - Self-backhauling KW - transmit power optimization U2 - 10.1109/TWC.2018.2821682 DO - 10.1109/TWC.2018.2821682 M3 - Article VL - 17 SP - 4219 EP - 4236 JO - IEEE Transactions on Wireless Communications JF - IEEE Transactions on Wireless Communications SN - 1536-1276 IS - 6 ER - TY - JOUR T1 - Two-Sided Hypergenic Functions AU - Eriksson, Sirkka-Liisa AU - Orelma, Heikki AU - Vieira, Nelson PY - 2017 Y1 - 2017 N2 - 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. AB - 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. KW - $${\kappa}$$κ-Hypergenic functions KW - Clifford algebras KW - Hypergenic functions KW - Two-side hypergenic functions UR - http://www.scopus.com/inward/record.url?scp=84941331725&partnerID=8YFLogxK U2 - 10.1007/s00006-015-0605-2 DO - 10.1007/s00006-015-0605-2 M3 - Article VL - 27 SP - 111 EP - 123 JO - Advances in Applied Clifford Algebras JF - Advances in Applied Clifford Algebras SN - 0188-7009 IS - 1 ER - TY - GEN T1 - Ultra-large mode area single frequency anisotropic MOPA with double clad Yb-doped tapered fiber AU - Noronen, Teppo AU - Fedotov, Andrei AU - Rissanen, Joona AU - Gumenyuk, Regina AU - Butov, Oleg AU - Chamorovskii, Yuri AU - Golant, Konstantin AU - Odnoblyudov, Maxim AU - Filippov, Valery N1 - EXT="Noronen, Teppo" EXT="Fedotov, Andrei" INT=fot, "Rissanen, Joona" EXT="Gumenyuk, Regina" EXT="Filippov, Valery" PY - 2018/1/1 Y1 - 2018/1/1 N2 - We demonstrates all-fiber master oscillator - power amplifier delivered 70W output power at 1033.33nm with 8 kHz FWHM linewidth without any problems with SBS. The anisotropic ytterbium doped tapered double clad amplifier with 50 μm MFD and polarization extinction ratio about 30 dB is developed as a burst stage. The output radiation demonstrated perfect beam quality (M2=1.03/1.08). AB - We demonstrates all-fiber master oscillator - power amplifier delivered 70W output power at 1033.33nm with 8 kHz FWHM linewidth without any problems with SBS. The anisotropic ytterbium doped tapered double clad amplifier with 50 μm MFD and polarization extinction ratio about 30 dB is developed as a burst stage. The output radiation demonstrated perfect beam quality (M2=1.03/1.08). KW - active fiber KW - fiber amplifier KW - Fiber laser U2 - 10.1117/12.2288942 DO - 10.1117/12.2288942 M3 - Conference contribution T3 - Proceedings of SPIE BT - Fiber Lasers XV PB - SPIE, IEEE ER - TY - JOUR T1 - Unbiased Injection of Signal-Dependent Noise in Variance-Stabilized Range AU - Borges, Lucas AU - Vieira, Marcelo AU - Foi, Alessandro PY - 2016 Y1 - 2016 N2 - 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. AB - 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. KW - Anscombe transformation KW - Noise injection KW - optimization KW - Poisson noise KW - variance stabilization U2 - 10.1109/LSP.2016.2601689 DO - 10.1109/LSP.2016.2601689 M3 - Article VL - 23 SP - 1494 EP - 1498 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 10 ER - TY - JOUR T1 - Uncertainty propagation of iron loss from characterization measurements to computation of electrical machines AU - Belahcen, Anouar AU - Rasilo, Paavo AU - Nguyen, Thu Trang AU - Clénet, Stephane PY - 2015 Y1 - 2015 N2 - 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. AB - 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. KW - Electrical machine KW - Finite element methods KW - Iron losses KW - Uncertainty estimation U2 - 10.1108/COMPEL-10-2014-0271 DO - 10.1108/COMPEL-10-2014-0271 M3 - Article VL - 34 SP - 624 EP - 636 JO - COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering JF - COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering SN - 0332-1649 IS - 3 ER - TY - JOUR T1 - Universal construction mechanism for networks from one-dimensional symbol sequences AU - Emmert-Streib, Frank PY - 2012/10/15 Y1 - 2012/10/15 N2 - 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. AB - 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. KW - Complex networks KW - Network construction KW - Random networks KW - Symbol sequences KW - Universal network construction UR - http://www.scopus.com/inward/record.url?scp=84867336661&partnerID=8YFLogxK U2 - 10.1016/j.amc.2012.07.006 DO - 10.1016/j.amc.2012.07.006 M3 - Article VL - 219 SP - 1020 EP - 1030 JO - Applied Mathematics and Computation JF - Applied Mathematics and Computation SN - 0096-3003 IS - 3 ER - TY - JOUR T1 - Urothelial cancer gene regulatory networks inferred from large-scale RNAseq, Bead and Oligo gene expression data AU - Matos Simoes, Ricardo de AU - Dalleau, Sabine AU - Williamson, Kate E. AU - Emmert-Streib, Frank PY - 2015/5/14 Y1 - 2015/5/14 N2 - 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. AB - 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. KW - BC3Net KW - Computational genomics KW - Gene regulatory network KW - Urothelial cancer U2 - 10.1186/s12918-015-0165-z DO - 10.1186/s12918-015-0165-z M3 - Article VL - 9 JO - BMC Systems Biology JF - BMC Systems Biology SN - 1752-0509 M1 - 21 ER - TY - JOUR T1 - Variance Stabilization for Noisy+Estimate Combination in Iterative Poisson Denoising AU - Azzari, Lucio AU - Foi, Alessandro PY - 2016/8/1 Y1 - 2016/8/1 N2 - 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. AB - 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. KW - Anscombe transformation KW - image denoising KW - iterative filtering KW - photon-limited imaging KW - Poisson noise U2 - 10.1109/LSP.2016.2580600 DO - 10.1109/LSP.2016.2580600 M3 - Article VL - 23 SP - 1086 EP - 1090 JO - IEEE Signal Processing Letters JF - IEEE Signal Processing Letters SN - 1070-9908 IS - 8 ER - TY - GEN T1 - Wideband self-adaptive RF cancellation circuit for full-duplex radio T2 - Operating principle and measurements AU - Huusari, Timo AU - Choi, Yang Seok AU - Liikkanen, Petteri AU - Korpi, Dani AU - Talwar, Shilpa AU - Valkama, Mikko N1 - AUX=elt,"Huusari, Timo" AUX=elt,"Liikkanen, Petteri" PY - 2015/7/1 Y1 - 2015/7/1 N2 - This paper presents a novel RF circuit architecture for self-interference cancellation in inband full-duplex radio transceivers. The developed canceller is able to provide wideband cancellation with waveform bandwidths in the order of 100 MHz or beyond and contains also self-adaptive or self-healing features enabling automatic tracking of time-varying self-interference channel characteristics. In addition to architecture and operating principle descriptions, we also provide actual RF measurements at 2.4 GHz ISM band demonstrating the achievable cancellation levels with different bandwidths and when operating in different antenna configurations and under low-cost highly nonlinear power amplifier. In a very challenging example with a 100 MHz waveform bandwidth, around 41 dB total cancellation is obtained while the corresponding cancellation figure is close to 60 dB with the more conventional 20 MHz carrier bandwidth. Also, efficient tracking in time-varying reflection scenarios is demonstrated. AB - This paper presents a novel RF circuit architecture for self-interference cancellation in inband full-duplex radio transceivers. The developed canceller is able to provide wideband cancellation with waveform bandwidths in the order of 100 MHz or beyond and contains also self-adaptive or self-healing features enabling automatic tracking of time-varying self-interference channel characteristics. In addition to architecture and operating principle descriptions, we also provide actual RF measurements at 2.4 GHz ISM band demonstrating the achievable cancellation levels with different bandwidths and when operating in different antenna configurations and under low-cost highly nonlinear power amplifier. In a very challenging example with a 100 MHz waveform bandwidth, around 41 dB total cancellation is obtained while the corresponding cancellation figure is close to 60 dB with the more conventional 20 MHz carrier bandwidth. Also, efficient tracking in time-varying reflection scenarios is demonstrated. KW - Full-duplex KW - RF cancellation KW - Self adaptive KW - Self interference KW - Tracking U2 - 10.1109/VTCSpring.2015.7146163 DO - 10.1109/VTCSpring.2015.7146163 M3 - Conference contribution SN - 9781479980888 BT - 2015 IEEE 81st Vehicular Technology Conference (VTC Spring) PB - The Institute of Electrical and Electronics Engineers, Inc. ER -