Abstract : In this work we aim developing a novel theoretical framework to evaluate the feasibili... more Abstract : In this work we aim developing a novel theoretical framework to evaluate the feasibility of attaining significant improvement of fuel cells performance and stability by increasing the transport processes in porous partially fluid filled cathode compartment through the application of acoustic and structural waves. We have developed a unified model of structural/acoustic wave propagation in the PEM cathode compartment and coupled it with mass transfer in the porous media. A novel generalized filtration law that accounts for dynamic loadings, varying saturation, and solid structure distortion describing mass transfer in this complex but generic system has been found. It has been demonstrated that vibration gives rise to net change of saturation inside porous medium. Based on the numerical and experimental results number of practical recommendations optimizing material selections and performance regime has been made. Developed methodology is useful for wide range of Fuel Cell problems as well as for wide range of other porous structures and could serve as an important design tool.
2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2012
This paper presents a comprehensive study on the wire bond life for Insulated Gate Bipolar Transi... more This paper presents a comprehensive study on the wire bond life for Insulated Gate Bipolar Transistors (IGBT). The main elements are as follows: 1) Substantial non-uniformity in temperature distribution across the chip area was revealed; 2) Additional electrical resistance at the wire bonds was discovered, which can elevate the local temperature and shorten the wire bond life; 3) Thermo-structural simulation
International Journal of Energy for a Clean Environment, 2008
ABSTRACT Power electronics devices based on IGBTs are destined to play a critical role in the sus... more ABSTRACT Power electronics devices based on IGBTs are destined to play a critical role in the sustainable energy economy by providing the efficient interface between lower emissions and renewable primary movers such as wind turbines, microturbines, photovoltaic, fuel cells, etc and local power consumers or electrical distribution system such as microgrids. The designers of Thermal Management Systems (TMS) for power electronics are faced with ever increasing demand of improving efficiency, increased reliability and life time as well as reducing the design cycle time, which requires the capability to quickly analyze and optimize enhanced thermal solutions though accurate prediction of three-dimensional transient temperature fields. A universal training strategy for a state space model is suggested that reproduces temperature responses of power electronic devices with any transient power dissipation profile. Full CFD and FEA transient models of IGBT modules of various structural elements cooled by natural convection and conduction have been created using the ANSYS IcePak software package. It is extremely time-consuming to use this full model for multiple-mission studies therefore a reduced order model in state space form has been developed to significantly reduce design time. The reduced order model has been trained using a single finite element model run with a universal power dissipation profile. This profile consisted of band limited white noise with a magnitude and frequency limit based on the combination of given devices and set of mission profiles. It has been shown that the state space model trained with such a profile reproduces the response to a wide variety of different power dissipation patterns typical for our application with an accuracy of about 2°C. Several different approaches for the choice of the state space model have been studied as well as proper selection of state space size and metrics for estimation of modeling error. It is suggested that the proposed method can be a universal way of extracting a reduced order model from the high fidelity combination of CFD and FEA models typical for power electronics applications, and possibly for a broader range of applications as well.
... Yiqing Lin1, Igor Fedchenia1, Bob LaBarre1, and Robert Tomastik2 ... In this paper, we presen... more ... Yiqing Lin1, Igor Fedchenia1, Bob LaBarre1, and Robert Tomastik2 ... In this paper, we present an agent-based simulation model developed for a 2-story office building verified using the evacuation data collected using video cameras during fire drills in the building. ...
ABSTRACT The phase quasi-integral for stimulated Raman scattering (SRS) is found-the relative pha... more ABSTRACT The phase quasi-integral for stimulated Raman scattering (SRS) is found-the relative phase of laser, stocks and polarization waves is nearly conserved during their propagation in Raman media. Due to this quasi-integral the temporal statistics of soliton-like pulses in a depleted pump are defined by phase statistics in the linear stage of SRS. Experimental results on the soliton-like pulse statistics are obtained confirming the existence of the phase quasi-integral.
Physica A: Statistical Mechanics and its Applications, 1984
ABSTRACT Construction of stationary distribution functions is described which satisfies the Fokke... more ABSTRACT Construction of stationary distribution functions is described which satisfies the Fokker-Planck equation locally in the vicinity of every point and the general non-potential case is considered as well as the case of diffusion tensor degeneration at individual points of the phase space. It is shown that the analysis can be performed by catastrophe theory methods. As an example, a system of Langevin-type equations describing single-mode laser generation is considered.
Physica A: Statistical Mechanics and its Applications, 1984
ABSTRACT A method is proposed for studying boundary nonlinear problems with fluctuating parameter... more ABSTRACT A method is proposed for studying boundary nonlinear problems with fluctuating parameters. As an example, an oscillator with parametric excitation and parametric noise with a nonlinear term is considered. A mechanism of the appearance of new metastable noise-induced states is shown and the influence of fluctuations on hysteresis properties of the system is studied.
Journal of Physics A: Mathematical and General, 1992
ABSTRACT An infinite system for the moments of a particle moving in a potential with two minima u... more ABSTRACT An infinite system for the moments of a particle moving in a potential with two minima under the action of fluctuations is considered. A class of solutions is found for which a divergent series can be summed up to a simple transcendent function. It is shown numerically that the true solution belongs to this class and conditions are set to define the solution uniquely.
A new method to solve the stochastic Liouville equation in the time domain has been developed. Th... more A new method to solve the stochastic Liouville equation in the time domain has been developed. The effective and accurate algorithm designed conserve the norm of the propagator at every time step. The algorithm is not dependent on how the fluctuations are generated. The method is applied to solve the stochastic Liouville equation of an electron spin, S=1/2, coupled to a nuclear spin system with spin quantum number I=1. The calculated slow-motion electron spin resonance (ESR) line shapes presented are for a model where the stochastic time dependent spin-lattice coupling was obtained from a Brownian dynamic simulation of restricted reorientation in a cone potential. These spectra were then compared with the spectra obtained by solving the stochastic Liouville equation (SLE) using the eigenfunction expansion method. All spectra conform exactly and the computer power used by the two methods are similar.
Abstract : In this work we aim developing a novel theoretical framework to evaluate the feasibili... more Abstract : In this work we aim developing a novel theoretical framework to evaluate the feasibility of attaining significant improvement of fuel cells performance and stability by increasing the transport processes in porous partially fluid filled cathode compartment through the application of acoustic and structural waves. We have developed a unified model of structural/acoustic wave propagation in the PEM cathode compartment and coupled it with mass transfer in the porous media. A novel generalized filtration law that accounts for dynamic loadings, varying saturation, and solid structure distortion describing mass transfer in this complex but generic system has been found. It has been demonstrated that vibration gives rise to net change of saturation inside porous medium. Based on the numerical and experimental results number of practical recommendations optimizing material selections and performance regime has been made. Developed methodology is useful for wide range of Fuel Cell problems as well as for wide range of other porous structures and could serve as an important design tool.
2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2012
This paper presents a comprehensive study on the wire bond life for Insulated Gate Bipolar Transi... more This paper presents a comprehensive study on the wire bond life for Insulated Gate Bipolar Transistors (IGBT). The main elements are as follows: 1) Substantial non-uniformity in temperature distribution across the chip area was revealed; 2) Additional electrical resistance at the wire bonds was discovered, which can elevate the local temperature and shorten the wire bond life; 3) Thermo-structural simulation
International Journal of Energy for a Clean Environment, 2008
ABSTRACT Power electronics devices based on IGBTs are destined to play a critical role in the sus... more ABSTRACT Power electronics devices based on IGBTs are destined to play a critical role in the sustainable energy economy by providing the efficient interface between lower emissions and renewable primary movers such as wind turbines, microturbines, photovoltaic, fuel cells, etc and local power consumers or electrical distribution system such as microgrids. The designers of Thermal Management Systems (TMS) for power electronics are faced with ever increasing demand of improving efficiency, increased reliability and life time as well as reducing the design cycle time, which requires the capability to quickly analyze and optimize enhanced thermal solutions though accurate prediction of three-dimensional transient temperature fields. A universal training strategy for a state space model is suggested that reproduces temperature responses of power electronic devices with any transient power dissipation profile. Full CFD and FEA transient models of IGBT modules of various structural elements cooled by natural convection and conduction have been created using the ANSYS IcePak software package. It is extremely time-consuming to use this full model for multiple-mission studies therefore a reduced order model in state space form has been developed to significantly reduce design time. The reduced order model has been trained using a single finite element model run with a universal power dissipation profile. This profile consisted of band limited white noise with a magnitude and frequency limit based on the combination of given devices and set of mission profiles. It has been shown that the state space model trained with such a profile reproduces the response to a wide variety of different power dissipation patterns typical for our application with an accuracy of about 2°C. Several different approaches for the choice of the state space model have been studied as well as proper selection of state space size and metrics for estimation of modeling error. It is suggested that the proposed method can be a universal way of extracting a reduced order model from the high fidelity combination of CFD and FEA models typical for power electronics applications, and possibly for a broader range of applications as well.
... Yiqing Lin1, Igor Fedchenia1, Bob LaBarre1, and Robert Tomastik2 ... In this paper, we presen... more ... Yiqing Lin1, Igor Fedchenia1, Bob LaBarre1, and Robert Tomastik2 ... In this paper, we present an agent-based simulation model developed for a 2-story office building verified using the evacuation data collected using video cameras during fire drills in the building. ...
ABSTRACT The phase quasi-integral for stimulated Raman scattering (SRS) is found-the relative pha... more ABSTRACT The phase quasi-integral for stimulated Raman scattering (SRS) is found-the relative phase of laser, stocks and polarization waves is nearly conserved during their propagation in Raman media. Due to this quasi-integral the temporal statistics of soliton-like pulses in a depleted pump are defined by phase statistics in the linear stage of SRS. Experimental results on the soliton-like pulse statistics are obtained confirming the existence of the phase quasi-integral.
Physica A: Statistical Mechanics and its Applications, 1984
ABSTRACT Construction of stationary distribution functions is described which satisfies the Fokke... more ABSTRACT Construction of stationary distribution functions is described which satisfies the Fokker-Planck equation locally in the vicinity of every point and the general non-potential case is considered as well as the case of diffusion tensor degeneration at individual points of the phase space. It is shown that the analysis can be performed by catastrophe theory methods. As an example, a system of Langevin-type equations describing single-mode laser generation is considered.
Physica A: Statistical Mechanics and its Applications, 1984
ABSTRACT A method is proposed for studying boundary nonlinear problems with fluctuating parameter... more ABSTRACT A method is proposed for studying boundary nonlinear problems with fluctuating parameters. As an example, an oscillator with parametric excitation and parametric noise with a nonlinear term is considered. A mechanism of the appearance of new metastable noise-induced states is shown and the influence of fluctuations on hysteresis properties of the system is studied.
Journal of Physics A: Mathematical and General, 1992
ABSTRACT An infinite system for the moments of a particle moving in a potential with two minima u... more ABSTRACT An infinite system for the moments of a particle moving in a potential with two minima under the action of fluctuations is considered. A class of solutions is found for which a divergent series can be summed up to a simple transcendent function. It is shown numerically that the true solution belongs to this class and conditions are set to define the solution uniquely.
A new method to solve the stochastic Liouville equation in the time domain has been developed. Th... more A new method to solve the stochastic Liouville equation in the time domain has been developed. The effective and accurate algorithm designed conserve the norm of the propagator at every time step. The algorithm is not dependent on how the fluctuations are generated. The method is applied to solve the stochastic Liouville equation of an electron spin, S=1/2, coupled to a nuclear spin system with spin quantum number I=1. The calculated slow-motion electron spin resonance (ESR) line shapes presented are for a model where the stochastic time dependent spin-lattice coupling was obtained from a Brownian dynamic simulation of restricted reorientation in a cone potential. These spectra were then compared with the spectra obtained by solving the stochastic Liouville equation (SLE) using the eigenfunction expansion method. All spectra conform exactly and the computer power used by the two methods are similar.
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