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Annual Information Technology, Electromechanical Engineering and Microelectronics Conference (IEMECON)

作者： Arzoo Shakya Praveen Pal Sneha Kabra Modeling and Simulation Research Laboratory Shaheed Rajguru College of Applied Sciences for Women University of Delhi New Delhi India Nanolab Department of Electrical Engineering Indian Institute of Technology Kanpur Uttar Pradesh India Department of Instrumentation Shaheed Rajguru College of Applied Sciences for Women University of Delhi New Delhi India

ISBN: (数字)9798350387315

ISBN: (纸本)9798350387322

This work presents performance investigation of the impact of different substrates on GaN-HEMTs, with an emphasis on important parameters including drain current, transconductance, and cut-off frequency. GaN-HEMT device with gate length of 200 nm and gate width of 100 μm was used to study the device performance using different substrates such as 6H-SiC, Al 2 O 3 , GaN, and β-Ga 2 O 3 . It has been observed that β-Ga 2 O 3 , shows excellent device performance with a maximum drain current of 1.21 A/mm, a peak transconductance of 262.46 mS/mm, and a cut-off frequency of 50.59 GHz. These findings demonstrate that β-Ga 2 O 3 can be used as a suitable substrate for improving GaN-HEMT performance, especially for high frequency high power application.

关键词： Performance evaluation Cutoff frequency HEMTs Logic gates Wide band gap semiconductors High frequency Transistors Substrates Transconductance Aluminum gallium nitride

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Comparative Analysis of T-gate GaN HEMT with different passivation layers for RF Applications

Comparative Analysis of T-gate GaN HEMT with different passi...

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Communication, Control and Intelligent Systems (CCIS)

ISBN: (数字)9798331528201

ISBN: (纸本)9798331528218

In this work, we investigate the impact of various passivation layers on electrical characteristics of T-gate GaN HEMT. Passivation schemes with single passivation layer of SiO 2 , Al 2 O 3 , HfO 2 , and stacked HfO 2 /SiO 2 with and without air gap have been investigated. The air gap between the gate and the low-k passivation layer effectively reduces the gate capacitance, thereby enhancing the RF characteristics of the device. A 200 nm gate length and 100 μm width are used to simulate the device. The passivation layer of SiO 2 with air gap, due to improved transconductance and gate capacitances exhibits a cut-off frequency of 39.22 GHz and a maximum oscillation frequency of 51.6 GHz. Results clearly shows that AlGaN/GaN HEMT having SiO 2 with an air gap is most suitable for RF applications.

关键词： Radio frequency Silicon compounds Air gaps Cutoff frequency HEMTs Logic gates Capacitance Wide band gap semiconductors Aluminum gallium nitride Passivation

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Two-phase bio-nanofluid flow through a bifurcated artery with magnetic field interaction

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International Journal of Thermofluids 2022年 15卷

作者： Hossain, S. M. Chapal Ferdows, Mohammad Bangalee, Md. Zavid Iqbal Alam, Md. Shariful Department of Applied Mathematics University of Dhaka Dhaka 1000 Bangladesh Research Group of Fluid Flow Modeling and Simulation Department of Applied Mathematics University of Dhaka Dhaka 1000 Bangladesh Department of Mathematics Jagannath University Dhaka 1100 Bangladesh

A modified multiphase flow model is applied for a better understanding of bio-nanofluid (blood containing 4% (w/v) Fe3O4 nanoparticles) flow regimes through a real bifurcated artery. The magnetic field with distinct current intensities (I = 0 – 300 A) was employed to induce the flow features when the wire's source is placed nearby the junction of the asymmetrical branched artery during numerical computation. The finite volume method was used to solve the coupled hemodynamics model. Results show that the pressure, and vorticity profiles increased and fallen gradually with the existence of the magnetic source and further obtained the maximum pressure for the strong current intensity (I = 300 A). The fluctuating vorticity distributions are found along the inner and outer vessel wall as well as the predicted lines created within the simulated domain for the increase of current intensity. The velocity outlines variates steadily, and the local peak velocities are obtained with the increase of the magnetic force. With the increment of the current intensity upto I = 300 A, the flow rate rises progressively for the asymmetric branched vessel, and the opposite scenario is found for the root vessel. The temperature profiles decrease steadily with the increment of the applied current intensity. With the manifestation of the magnetic source, the irregular flow behaviours are found within the asymmetrical bifurcated artery. This modeling investigation could be beneficial for the emergent therapy plan of ample vascular diseases as the magnetic drug targeting system. © 2022

关键词： Finite volume method

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Two-dimensional TiNBr as photocatalyst for overall water splitting

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Physical Review Materials 2025年第2期9卷 025802-025802页

作者： Yatong Wang Geert Brocks Ceren Tayran Süleyman Er DIFFER – Dutch Institute for Fundamental Energy Research De Zaale 20 5612 AJ Eindhoven the Netherlands Materials Simulation and Modeling Department of Applied Physics Eindhoven University of Technology 5600 MB Eindhoven the Netherlands Computational Chemical Physics Faculty of Science and Technology and MESA+ Institute for Nanotechnology University of Twente 7500 AE Enschede the Netherlands Department of Physics Faculty of Science Gazi University Ankara 06500 Turkey

Two-dimensional (2D) Janus materials have gained increasing attention as water-splitting photocatalysts for hydrogen production. We use first-principles calculations to predict a stable 2D Janus T−TiNBr structure with strong near-ultraviolet sunlight absorption and band edges that align favorably with the water redox potentials for oxygen and hydrogen evolution. We show that the optical and electronic properties of T−TiNBr can be modulated to a certain extent by applying external uniaxial strain. Explicit calculations of the redox reactions reveal that solar-driven water splitting is viable at the N-side of T−TiNBr while the Br-side requires modifications such as vacancy creation, the application of an external potential, or adjustment of the pH conditions.

关键词： Redox reactions

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QNBO: QUASI-NEWTON MEETS BILEVEL OPTIMIZATION

arXiv

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arXiv 2025年

作者： Fang, Sheng Liu, Yong-Jin Yao, Wei Yu, Chengming Zhang, Jin Public Health School Fujian Medical University China School of Mathematics and Statistics Fuzhou University China Center for Applied Mathematics of Fujian Province China National Center for Applied Mathematics Shenzhen SUSTech China Department of Mathematics SUSTech China School of Science BUPT China CETC Key Laboratory of Smart City Modeling Simulation and Intelligent Technology The Smart City Research Institute of CETC China

Bilevel optimization, addressing challenges in hierarchical learning tasks, has gained significant interest in machine learning. The practical implementation of the gradient descent method to bilevel optimization encounters computational hurdles, notably the computation of the exact lower-level solution and the inverse Hessian of the lower-level objective. Although these two aspects are inherently connected, existing methods typically handle them separately by solving the lower-level problem and a linear system for the inverse Hessian-vector product. In this paper, we introduce a general framework to address these computational challenges in a coordinated manner. Specifically, we leverage quasi-Newton algorithms to accelerate the resolution of the lower-level problem while efficiently approximating the inverse Hessian-vector product. Furthermore, by exploiting the superlinear convergence properties of BFGS, we establish the non-asymptotic convergence analysis of the BFGS adaptation within our framework. Numerical experiments demonstrate the comparable or superior performance of the proposed algorithms in real-world learning tasks, including hyperparameter optimization, data hyper-cleaning, and few-shot meta-learning. Copyright © 2025, The Authors. All rights reserved.

关键词： Linear systems

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Two-Phase Bio-Nanofluid Flow Through a Bifurcated Artery with Magnetic Field Interaction

SSRN

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SSRN 2022年

作者： Hossain, S.M.C. Ferdows, M. Bangalee, M.Z.I. Alam, M.S. Department of Applied Mathematics University of Dhaka Dhaka1000 Bangladesh Research Group of Fluid Flow Modeling and Simulation Department of Applied Mathematics University of Dhaka Dhaka1000 Bangladesh Department of Mathematics Jagannath University Dhaka1100 Bangladesh

A modified multiphase flow model is applied for a better understanding of bio-nanofluid (blood containing 4% (w/v) Fe3O4 nanoparticles) flow characteristics through a realistic bifurcated artery. The magnetic field with distinct current intensities was employed to induce the flow regime when the wire’s source is placed nearby the junction of the asymmetrical branched artery during numerical computation. The finite volume method was used to solve the coupled hemodynamics model. Results show that the pressure, and vorticity profiles increased and fallen gradually with the existence of the magnetic source and further obtained the maximum pressure for the strong current intensity (I = 300 A). The fluctuating vorticity distributions are found along the inner and outer vessel wall as well as the predicted lines created within the simulated domain for the increase of current intensity. The velocity profiles variates gradually and the local peak velocities are obtained with the increase of the magnetic force. With the increment of the current intensity upto I = 300 A, the flow rate rises progressively for the asymmetric branched vessel, and the reverse scenario is found for the root vessel. The temperature profiles decrease steadily with the increment of the applied current intensity. With the manifestation of the magnetic source, the irregular flow behaviours are found within the asymmetrical bifurcated artery. This modeling investigation could be beneficial for the emergent therapy plan of ample vascular diseases as the magnetic drug targeting system. © 2022, The Authors. All rights reserved.

关键词： Finite volume method

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Constrained Bi-Level Optimization: Proximal Lagrangian Value function Approach and Hessian-free Algorithm

arXiv

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arXiv 2024年

作者： Yao, Wei Yu, Chengming Zeng, Shangzhi Zhang, Jin National Center for Applied Mathematics Shenzhen Department of Mathematics Southern University of Science and Technology Shenzhen China CETC Key Laboratory of Smart City Modeling Simulation and Intelligent Technology The Smart City Research Institute of CETC National Center for Applied Mathematics Shenzhen Shenzhen China Department of Mathematics and Statistics University of Victoria VictoriaBC Canada Department of Mathematics Southern University of Science and Technology National Center for Applied Mathematics Shenzhen Shenzhen China

This paper presents a new approach and algorithm for solving a class of constrained Bi-Level Optimization (BLO) problems in which the lower-level problem involves constraints coupling both upper-level and lower-level variables. Such problems have recently gained significant attention due to their broad applicability in machine learning. However, conventional gradient-based methods unavoidably rely on computationally intensive calculations related to the Hessian matrix. To address this challenge, we begin by devising a smooth proximal Lagrangian value function to handle the constrained lower-level problem. Utilizing this construct, we introduce a single-level reformulation for constrained BLOs that transforms the original BLO problem into an equivalent optimization problem with smooth constraints. Enabled by this reformulation, we develop a Hessian-free gradient-based algorithm-termed proximal Lagrangian Value function-based Hessian-free Bi-level Algorithm (LV-HBA)-that is straightforward to implement in a single loop manner. Consequently, LV-HBA is especially well-suited for machine learning applications. Furthermore, we offer non-asymptotic convergence analysis for LV-HBA, eliminating the need for traditional strong convexity assumptions for the lower-level problem while also being capable of accommodating non-singleton scenarios. Empirical results substantiate the algorithm's superior practical performance. © 2024, CC BY-NC-SA.

关键词： Machine learning

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Numerical Analysis of Thermal Convection in a CPU Chassis

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Open Journal of Modelling and simulation 2021年第1期9卷 43-58页

作者： M. Z. I. Bangalee Md. Mizanur Rahman M. Ferdows M. S. Islam Department of Applied Mathematics University of Dhaka Dhaka Bangladesh Research Group of Fluid Flow Modeling and Simulation Department Applied Mathematics University of Dhaka Dhaka Bangladesh Department of Mathematics University of Dhaka Dhaka Bangladesh

Flow distribution and the effects of different boundary conditions are achieved for a steady-state conjugate (Conduction & Convection) heat transfer process. A plate fin heat sink with horizontal fin orientation along with a computer chassis is numerically investigated and simulated using software ANSYS CFX. Fin orientation of a heat sink changes the direction of fluid flow inside the chassis. For predicting turbulence of the flow inside the domain, a two-equation based k-ε turbulence model is chosen. The Reynolds number based on inflow velocity and geometry is found 4.2 × 10³ that indicates that the flow is turbulent inside the chassis. To get proper thermal cooling, the optimum velocity ratio of inlet/outlet, dimension of inlet/outlet and different positions of outlet on the back sidewall of the chassis are predicted. Aspect velocity ratio between the inlet airflow and the outlet airflow has an effect on the steadiness of the flow. Mass flow rate depends on the dimension of the inlet/outlet. The horizontal fin orientation with 1:

关键词： Reynolds Number Turbulence Model Heat Sink CPU Chassis Conduction Convection

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On the numerical solution to the truncated discrete SPH formulation of the hydrostatic problem

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Journal of Hydrodynamics 2020年第4期32卷 699-709页

作者： Pablo Eleazar Merino-Alonso Fabricio Macia Antonio Souto-Iglesias Mathematical Modeling Analysisand Simulation Applied to Engineering Research Group(M2ASAI)Universi dad politecnica de Madrid(UPM)School of marine engineering(ETSIN)MadridSpain Marine and Hydrodynamical Model Basin Research Group(CEHINAV) Universidad Politecnica de Madrid(UPM)School of Marine Engineering(ETSIN)MadridSpain

The aim of this work is to study the solution of the smoothed particle hydrodynamics(SPH)discrete formulation of the hydrostatic problem with a free *** problem,in which no time dependency is considered,takes the form of a system of linear *** particular,the problem in one dimension is *** focus is set on the convergence when both the particle spacing and the smoothing length tend to zero by keeping constant their *** of this ratio of the order of one,corresponding to a limited number of neighbors,are of practical ***,the problem in which each particle has one single neighbor at each side is *** explicit expressions of the numerical solution and the quadratic error are provided in this *** expression of the quadratic error demonstrates that the SPH solution does not converge to the exact one in general under the specified *** this case,the error converges to a residue,which is in general large compared to the norm of the exact *** cases with two and three neighbors are also *** analytical study in the case of two neighbors is performed,showing how the kernel influences the accuracy of the solution through modifying the condition number of the referred system of linear *** addition to that,a numerical investigation is carried out using several Wendland kernel *** two and three neighbors are involved it is found that the error tends in most cases to a small limiting value,different from zero,while divergent solutions are also found in the case of two neighbors with the Wendland Kernel *** cases with more neighbors are also *** general,the Wendland Kernel C2 turns out to be the worst choice,as the solution is divergent for certain values of the ratio between the particle spacing and the smoothing length,associated with an ill-conditioned matrix.

关键词： Smoothed particle hydrodynamics(SPH) convergence water-at-rest problem hydrostatic tank,free surface kernel truncation

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A Biased-Randomized Simheuristic for a Hybrid Flow Shop with Stochastic Processing Times in the Semiconductor Industry 22

A Biased-Randomized Simheuristic for a Hybrid Flow Shop with...

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Proceedings of the Winter simulation Conference

作者： Majsa Ammouriova Javier Panadero Madlene Leißau Christoph Laroque Christin Schumacher Angel A. Juan Computer Science Department Universitat Oberta de Catalunya Euncet Business School Barcelona SPAIN Institute for Management and Information University of Applied Sciences Zwickau Zwickau GERMANY Informatik 4 - Modeling and Simulation Department of Computer Science TU Dortmund University Dortmund GERMANY Dept. of Applied Statistics and Operations Research Universitat Politècnica de València Alcoy SPAIN

Compared to other industries, production systems in semiconductor manufacturing have an above-average level of complexity. Developments in recent decades document increasing product diversity, smaller batch sizes, and a rapidly changing product range. At the same time, the interconnections between equipment groups increase due to rising automation, thus making production planning and control more difficult. This paper discusses a hybrid flow shop problem with realistic constraints, such as stochastic processing times and priority constraints. The primary goal of this paper is to find a solution set (permutation of jobs) that minimizes the production makespan. The proposed algorithm extends our previous work by combining biased-randomization techniques with a discrete-event simulation heuristic. This simulation-optimization approach allows us to efficiently model dependencies caused by batching and by the existence of different flow paths. As shown in a series of numerical experiments, our methodology can achieve promising results even when stochastic processing times are considered.

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