The Experts below are selected from a list of 696 Experts worldwide ranked by ideXlab platform
Samuel Graham - One of the best experts on this subject based on the ideXlab platform.
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The Impact of Nongray Thermal Transport on the Temperature of AlGaN/GaN HFETs
IEEE Transactions on Electron Devices, 2015Co-Authors: Nazli Donmezer, Munmun Islam, Paul Douglas Yoder, Samuel GrahamAbstract:The Hotspot Temperature in AlGaN/GaN heterostructure FETs has been of great interest due to its effect on the reliability of these devices. Both the nanoscale heat transfer effects and complex energy transfer mechanism from electrons to lattice are factors affecting the Hotspot Temperature, which is not accounted for in continuum level thermal simulations. The effects of heat generation zone size and the energy transfer mechanism from electrons to the lattice on the Hotspot Temperature were analyzed using electrical and nongray ballistic-diffusive thermal transport simulations for devices operated at a fixed power, but different biasing conditions. Results show that Hotspot Temperatures are impacted from nanoscale effects but the complex energy scattering mechanisms from electrons to the lattice do not have a significant impact on the Hotspot Temperature due to the scattering and redistribution of the energy within the phonon population.
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The Impact of Noncontinuum Thermal Transport on the Temperature of AlGaN/GaN HFETs
IEEE Transactions on Electron Devices, 2014Co-Authors: Nazli Donmezer, Samuel GrahamAbstract:The effects of power density and heat generation zone size on the Hotspot Temperature of AlGaN/GaN HFET devices were predicted using an electrothermal modeling approach. The thermal response was modeled using a multiscale model that accounted for ballistic-diffusive phonon transport effects in the heat generation zone near the gate and diffusive transport effects outside of this zone. The Joule heating distribution was calculated using a hydrodynamic model in Sentaurus Device. The Hotspot Temperatures at different biasing conditions were determined using the multiscale thermal model and compared with a fully diffusive transport model. The results show that the Hotspot Temperature is higher when ballistic-diffusive transport effects are considered and this difference increases with increasing power density in the AlGaN/GaN HFETs.
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modeling the Hotspot Temperature in algan gan high electron mobility transistors using a non gray phonon bte solver
Volume 9: Micro- and Nano-Systems Engineering and Packaging Parts A and B, 2012Co-Authors: Fatma Nazli Donmezer, Munmun Islam, Samuel Graham, Douglas YoderAbstract:In this work, we utilize electron-phonon Monte Carlo simulations of AlGaN/GaN HEMTs to determine the energy loss rate of electrons in the channel of the transistor as a function of bias conditions. Intense energy transfer from electrons to phonons is observed near the gate edge on the drain side of such devices where the peak electric field exists. This intense energy exchange results in nanometer sized Hotspots in the vicinity of the gate edge. In order to account for effects of ballistic phonon transport on Temperature near the Hotspots, a non-gray Discrete Ordinates Method (DOM) is used as a numerical solver for the phonon Boltzmann Transport Equation (BTE). The non-gray model accounts for dispersion effects of GaN by splitting the dispersion curve of GaN into a finite number of frequency bands. The phonons in each frequency band are assumed to have the same properties with the other phonons in the same band and the relaxation times between these bands are calculated. The results show how energy is redistributed among the available phonon bands and demonstrates which modes are most effective at transporting the thermal energy. Finally, the Hotspot Temperature predictions obtained by the model are compared to Temperatures obtained by gray and continuum modeling approaches to show the discrepancies between different techniques.Copyright © 2012 by ASME
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Modeling the Hotspot Temperature in AlGaN/GaN High Electron Mobility Transistors Using a Non-Gray Phonon BTE Solver
Volume 9: Micro- and Nano-Systems Engineering and Packaging Parts A and B, 2012Co-Authors: Fatma Nazli Donmezer, Munmun Islam, Samuel Graham, Douglas YoderAbstract:In this work, we utilize electron-phonon Monte Carlo simulations of AlGaN/GaN HEMTs to determine the energy loss rate of electrons in the channel of the transistor as a function of bias conditions. Intense energy transfer from electrons to phonons is observed near the gate edge on the drain side of such devices where the peak electric field exists. This intense energy exchange results in nanometer sized Hotspots in the vicinity of the gate edge. In order to account for effects of ballistic phonon transport on Temperature near the Hotspots, a non-gray Discrete Ordinates Method (DOM) is used as a numerical solver for the phonon Boltzmann Transport Equation (BTE). The non-gray model accounts for dispersion effects of GaN by splitting the dispersion curve of GaN into a finite number of frequency bands. The phonons in each frequency band are assumed to have the same properties with the other phonons in the same band and the relaxation times between these bands are calculated. The results show how energy is redistributed among the available phonon bands and demonstrates which modes are most effective at transporting the thermal energy. Finally, the Hotspot Temperature predictions obtained by the model are compared to Temperatures obtained by gray and continuum modeling approaches to show the discrepancies between different techniques.Copyright © 2012 by ASME
Nazli Donmezer - One of the best experts on this subject based on the ideXlab platform.
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The Impact of Nongray Thermal Transport on the Temperature of AlGaN/GaN HFETs
IEEE Transactions on Electron Devices, 2015Co-Authors: Nazli Donmezer, Munmun Islam, Paul Douglas Yoder, Samuel GrahamAbstract:The Hotspot Temperature in AlGaN/GaN heterostructure FETs has been of great interest due to its effect on the reliability of these devices. Both the nanoscale heat transfer effects and complex energy transfer mechanism from electrons to lattice are factors affecting the Hotspot Temperature, which is not accounted for in continuum level thermal simulations. The effects of heat generation zone size and the energy transfer mechanism from electrons to the lattice on the Hotspot Temperature were analyzed using electrical and nongray ballistic-diffusive thermal transport simulations for devices operated at a fixed power, but different biasing conditions. Results show that Hotspot Temperatures are impacted from nanoscale effects but the complex energy scattering mechanisms from electrons to the lattice do not have a significant impact on the Hotspot Temperature due to the scattering and redistribution of the energy within the phonon population.
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The Impact of Noncontinuum Thermal Transport on the Temperature of AlGaN/GaN HFETs
IEEE Transactions on Electron Devices, 2014Co-Authors: Nazli Donmezer, Samuel GrahamAbstract:The effects of power density and heat generation zone size on the Hotspot Temperature of AlGaN/GaN HFET devices were predicted using an electrothermal modeling approach. The thermal response was modeled using a multiscale model that accounted for ballistic-diffusive phonon transport effects in the heat generation zone near the gate and diffusive transport effects outside of this zone. The Joule heating distribution was calculated using a hydrodynamic model in Sentaurus Device. The Hotspot Temperatures at different biasing conditions were determined using the multiscale thermal model and compared with a fully diffusive transport model. The results show that the Hotspot Temperature is higher when ballistic-diffusive transport effects are considered and this difference increases with increasing power density in the AlGaN/GaN HFETs.
Sandip Kundu - One of the best experts on this subject based on the ideXlab platform.
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A Wavelet-Based Spatio-Temporal Heat Dissipation Model for Reordering of Program Phases to Produce Temperature Extremes in a Chip
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 2012Co-Authors: Sudarshan Srinivasan, Kunal P. Ganeshpure, Sandip KunduAbstract:Localized heating leads to generation of thermal Hotspots that affect the performance and reliability of an integrated circuit (IC). Functional workloads determine the locations and Temperatures of Hotspots on a die. In this paper, we present a systematic approach for developing a synthetic workload to maximize the Temperature of a target Hotspot. Our approach is based on the observation that Hotspot Temperature is determined not only by the current activity in that region, but also by the past activities in the surrounding regions. Accordingly, we develop a wavelet-based canonical spatio-temporal heat dissipation model for program traces, and use a novel integer linear programming formulation to rearrange program phases to generate target worst case Hotspot Temperature. Program phase behavior is rooted in the static structure of programs. In this case, the initial set of program phases is extracted from the SPEC 2000 benchmark. We apply this formulation to target another well-known problem of maximizing the Temperature between a pair of coordinates in an IC. Experimental results show that by taking the spatio-temporal effect into account, we can raise the Temperature of a Hotspot higher than what is otherwise possible. Hotspot Temperature maximization is important in design verification and testing.
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Maximizing Hotspot Temperature: Wavelet based modelling of heating and cooling profile of functional workloads
2011 12th International Symposium on Quality Electronic Design, 2011Co-Authors: Sudarshan Srinivasan, Kunal P. Ganeshpure, Sandip KunduAbstract:Localized heating leads to generation of thermal Hotspots that affect performance and reliability of a chip. Functional workloads determine the locations and Temperature of Hotspots on a die. Programs are classified into phases based on program execution profile. During a phase, spatial power dissipation pattern of an application remains unchanged. In this paper we present a systematic approach for developing a synthetic workload which is formed by a combination of phases extracted from functional workload which maximizes the Temperature of a Hotspot. Hotspot Temperature is determined not only by the current activity in that region, but also by the past activities in the surrounding regions. Therefore, if the surrounding areas were “pre-heated” with a different workload, then the target region may become hotter due to slower rate of lateral heat dissipation. In this paper a wavelet-based canonical power dissipation model is developed to capture the temporal and spatial behavior of the power traces. This is followed by an Integer Linear Programming approach which is used to determine the sequence of these program phases in order to create a worst case Temperature at the Hotspot. The novel contributions of this paper are (i) wavelet based technique to model spatio-temporal power variation for the phases in the functional workload and a (ii) linear programming scheme that arranges program phases to create the worst case Temperature.
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ISQED - Maximizing Hotspot Temperature: Wavelet based modelling of heating and cooling profile of functional workloads
2011 12th International Symposium on Quality Electronic Design, 2011Co-Authors: Sudarshan Srinivasan, Kunal P. Ganeshpure, Sandip KunduAbstract:Localized heating leads to generation of thermal Hotspots that affect performance and reliability of a chip. Functional workloads determine the locations and Temperature of Hotspots on a die. Programs are classified into phases based on program execution profile. During a phase, spatial power dissipation pattern of an application remains unchanged. In this paper we present a systematic approach for developing a synthetic work load which is formed by a combination of phases extracted from functional work load which maximizes the Temperature of a Hotspot. Hotspot Temperature is determined not only by the current activity in that region, but also by the past activities in the surrounding regions. Therefore, if the surrounding areas were “pre-heated” with a different workload, then the target region may become hotter due to slower rate of lateral heat dissipation. In this paper a wavelet-based canonical power dissipation model is developed to capture the temporal and spatial behavior of the power traces. This is followed by an Integer Linear Programming approach which is used to determine the sequence of these program phases in order to create a worst case Temperature at the Hotspot. The novel contributions of this paper are (i) wavelet based technique to model spatio-temporal power variation for the phases in the functional workload and a (ii) linear programming scheme that arranges program phases to create the worst case Temperature.
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ACM Great Lakes Symposium on VLSI - Reducing Temperature variability by routing heat pipes
Proceedings of the 19th ACM Great Lakes symposium on VLSI - GLSVLSI '09, 2009Co-Authors: Kunal Ganeshpure, Sandip Kundu, Ilia Polian, Bernd BeckerAbstract:A significant increase in power density in modern nano-electronic VLSI circuits has lead to increased localized heating and generation of hot spots. These Temperature effects can lead to reliability and performance problems. This paper presents a novel design time Temperature aware methodology which consists of using additional routing known as Heat Pipes, to transfer heat from hot to cold regions. In order to evaluate the effect of Heat Pipes, a thermal model to simulate effect of metal interconnect on heat distribution is also developed. Results show a 5% to 7% decrease in Temperature variation through-out and 2 to 3 degree reduction in Hotspot Temperature as a result of Heat Pipes.
R. Herman - One of the best experts on this subject based on the ideXlab platform.
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A thermal loading guide for residential distribution transformers based on time-variant current load models
IEEE Transactions on Power Systems, 2004Co-Authors: S.w. Heunis, R. HermanAbstract:This paper presents a practical thermal loading guide for distribution transformers feeding residential customers. Extensive load research data were used to estimate the thermal response of a "standard IEC distribution transformer." A strong relationship between the parameters of a load modeled by load current as a function of time and the Hotspot Temperature was found. Using this type of load model, a method was developed for estimating the Hotspot Temperature of a transformer for customers from different load classes. A method was derived to translate the thermal response of a standard IEC distribution transformer to any practical transformer.
Xinghua Wang - One of the best experts on this subject based on the ideXlab platform.
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a new prediction model for transformer winding Hotspot Temperature fluctuation based on fuzzy information granulation and an optimized wavelet neural network
Energies, 2017Co-Authors: Li Zhang, Wenfang Zhang, Tong Zhao, Xinghua WangAbstract:Winding Hotspot Temperature is the key factor affecting the load capacity and service life of transformers. For the early detection of transformer winding Hotspot Temperature anomalies, a new prediction model for the Hotspot Temperature fluctuation range based on fuzzy information granulation (FIG) and the chaotic particle swarm optimized wavelet neural network (CPSO-WNN) is proposed in this paper. The raw data are firstly processed by FIG to extract useful information from each time window. The extracted information is then used to construct a wavelet neural network (WNN) prediction model. Furthermore, the structural parameters of WNN are optimized by chaotic particle swarm optimization (CPSO) before it is used to predict the fluctuation range of the Hotspot Temperature. By analyzing the experimental data with four different prediction models, we find that the proposed method is more effective and is of guiding significance for the operation and maintenance of transformers.