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Local Time Stepping and Load Balance of DGTD on High-Performance Computing Architectures 4

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Local Time Stepping and Load Balance of DGTD on High-Perform...

4th International applied computational Electromagnetics Society Symposium in China, ACES-China 2021

作者： Wang, Weijie Tang, Dehong Zhao, Zhenguo Zhou, Haijing Software Center for High Performance Numerical Simulation CAEP Beijing100088 China Institute of Applied Physics and Computational Mathematics Beijing100088 China

ISBN: (纸本)9781733509619

Extremely small meshes of system-in-package severely limit the integration-time step of simulations of time-domain electromagnetic problems. Here, we redesigned a parallel multilevel local time stepping (LTS) algorithms as well as load balance scheme to make our code capable of running on large clusters with high parallel efficiency. Besides, communication cost can be reduced by adjusting the update order of mesh levels. Numerical experiments are given to validate our algorithms. © 2021 applied computational Electromagnetics Society (ACES).

关键词： Galerkin methods

Discrete Boltzmann modeling of Rayleigh-Taylor instability: Effects of interfacial tension, viscosity, and heat conductivity

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Physical Review E 2022年第1期106卷 015102-015102页

作者： Jie Chen Aiguo Xu Dawei Chen Yudong Zhang Zhihua Chen Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P.O. Box 8009-26 Beijing 100088 China Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing 210094 China State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China School of Mechanics and Safety Engineering Zhengzhou University Zhengzhou 450001 China

The two-dimensional Rayleigh-Taylor instability (RTI) in compressible flow with intermolecular interactions is probed via the discrete Boltzmann method. The effects of interfacial tension, viscosity, and heat conduction are investigated. It is found that the influences of interfacial tension on the perturbation amplitude, bubble velocity, and two kinds of entropy production rates all show differences at different stages of RTI evolution. It inhibits the RTI evolution at the bubble acceleration stage, while at the asymptotic velocity stage, it first promotes and then inhibits the RTI evolution. Viscosity and heat conduction inhibit the RTI evolution. Viscosity shows a suppressive effect on the entropy generation rate related to heat flow at the early stage but a first promotive and then suppressive effect on the entropy generation rate related to heat flow at a later stage. Heat conduction shows a promotive effect on the entropy generation rate related to heat flow at an early stage. Still, it offers a first promotive and then suppressive effect on the entropy generation rate related to heat flow at a later stage. By introducing the morphological boundary length, we find that the stage of exponential growth of the interface length with time corresponds to the bubble acceleration stage. The first maximum point of the interface length change rate and the first maximum point of the change rate of the entropy generation rate related to viscous stress can be used as a criterion for RTI to enter the asymptotic velocity stage.

关键词： Complex fluids Entropy production Flow instability Interface & surface thermodynamics Nonequilibrium & irreversible thermodynamics Rayleigh-Taylor instability Thermodynamics of mixing

NON-UNIQUENESS OF WEAK SOLUTIONS TO THE NAVIER-STOKES EQUATIONS IN R3

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arXiv 2024年

作者： Miao, Changxing Nie, Yao Ye, Weikui Institute Of Applied Physics And Computational Mathematics Beijing China School Of Mathematical Sciences And LPMC Nankai University Tianjin China School Of Mathematical Sciences South China Normal University Guangzhou China

To our knowledge, the convex integration method has been widely applied to the study of non-uniqueness of solutions to the Naiver-Stokes equations in the periodic region, but there are few works on applying this method to the corresponding problems in the whole space or other regions. In this paper, we prove that weak solutions of the Navier-Stokes equations are not unique in the class of weak solutions with finite kinetic energy in the whole space, which extends the non uniqueness result for the Navier-Stokes equations on torus T3 in the groundbreaking work (Buckmaster and Vicol, Ann. of Math., 189 (2019), pp.101-144) to R3. The critical ingredients of the proof include developing an iterative scheme in which the approximation solution is refined by decomposing it into local and non-local parts. For the non-local part, we introduce the localized corrector which plays a crucial role in balancing the compact support of the Reynolds stress error with the non-compact support of the solution. As applications of this argument, we first prove that there exist infinitely many weak solutions that dissipate the kinetic energy in smooth bounded domain. Moreover, we show the instability of the Navier-Stokes equations near Couette flow in L2(R3). Copyright © 2024, The Authors. All rights reserved.

关键词： Navier Stokes equations

Transversal effects of high order numerical schemes for compressible fluid flows

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applied mathematics and Mechanics(English Edition) 2019年第3期40卷 343-354页

作者： Xin LEI Jiequan LI School of Mathematical Sciences Beijing Normal University Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Center for Applied Physics and Technology Peking University

Finite volume schemes for the two-dimensional(2D) wave system are taken to demonstrate the role of the genuine dimensionality of Lax-Wendroff flow solvers for compressible fluid flows. When the finite volume schemes are applied, the transversal variation relative to the computational cell interfaces is neglected, and only the normal numerical flux is used, thanks to the Gauss-Green formula. In order to offset such defects, the Lax-Wendroff flow solvers or the generalized Riemann problem(GRP) solvers are adopted by substituting the time evolution of flows into the spatial variation. The numerical results show that even with the same convergence rate, the error by the GRP2D solver is almost one ninth of that by the multistage Runge-Kutta(RK) method.

关键词： transversal effect generalized Riemann problem(GRP)solver Lax-Wendroff flow solver wave system

Large-Time Behavior of the 2D Compressible Navier-Stokes System in Bounded Domains with Large Data and Vacuum

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arXiv 2023年

作者： Xinyu, Fan Jing, Li Xue, Wang Institute of Applied Physics and Computational Mathematics Beijing100088 China School of Mathematical Sciences University of Chinese Academy of Sciences Beijing100049 China Institute of Applied Mathematics AMSS Hua Loo-Keng Key Laboratory of Mathematics Chinese Academy of Sciences Beijing100190 China

The large time behavior of the unique strong solution to the barotropic compressible Navier-Stokes system is studied with large external forces and initial data, where the shear viscosity is a positive constant and the bulk one is proportional to a power of the density. Some uniform estimates on the Lp-norm of the density are established, and then deduce that the density converges to its steady state in Lp-spaces, which transforms the large external force into a small one in some sense. Moreover, to deal with the obstacles brought by boundary, the conformal mapping and the pull back Green function are applied to give a point-wise representation of the effective viscous flux, and then make use of slip boundary conditions to cancel out the singularity. Copyright © 2023, The Authors. All rights reserved.

关键词： Conformal mapping

Conformational Folding Activates Photoinduced Electron Transfer

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CCS Chemistry 2024年第11期6卷 2804-2813页

作者： Shiqing Huang Syed Ali Abbas Abedi Zhifeng Li Rongrong Huang Xiaoyu Yan Mohammad Izadyar Qinglong Qiao Yu Fang Zhaochao Xu Xiaogang Liu Fluorescence Research Group Singapore University of Technology and DesignSingapore 487372 School of Chemistry and Life Resources Renmin University of ChinaBeijing 100872 CAS Key Laboratory of Separation Science for Analytical Chemistry Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023 Research Center for Modeling and Computational Sciences Faculty of ScienceFerdowsi University of MashhadMashhad *** Key Laboratory of Applied Surface and Colloid Chemistry(Ministry of Education) School of Chemistry and Chemical EngineeringShaanxi Normal UniversityXi’anShaanxi 710119

Photoinduced electron transfer(PET)is a critical process in many functional materials,underpinning various technological applications(i.e.,fluorescent probes and photocatalysts).Despite its signifi-cance,the detailed structural dynamics of PET,particularly during the excited state,remain poorly *** study investigates the mechanisms of conformational folding and their implications for activating PET in molecular systems characterized by a fluorophore-spacer-receptor *** demonstrate that traditional computational models,primarily based on frontier molecular orbitals,often fall short in capturing these conformational dynamics,leading to inadequate explanations of PET *** the incorporation of conformational folding,our computational model has achieved excellent agreement with experimental data,thereby resolving several long-standing debates on PET *** mechanistic advancement not only deepens our understanding of PET but also opens new avenues for designing advanced functional *** have thus successfully demonstrated the imaging of lysosomes in live cells using a PET probe.

关键词： Photoinduced electron transfer conformational folding bioimaging excited-state dynamics advanced materials

An Asymptotic-Preserving Method for the Three-Temperature Radiative Transfer Model

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SSRN

SSRN 2024年

作者： Li, Ruo Li, Weiming Liang, Shengtong Shao, Yuehan Tang, Min Wang, Yanli CAPT LMAM School of Mathematical Sciences Peking University Beijing China Institute of Applied Physics and Computational Mathematics Beijing China School of Mathematical Sciences Peking University Beijing China Institute of Natural Sciences School of Mathematics Shanghai Jiaotong University Shanghai China Beijing Computational Science Research Center Beijing China

We present an asymptotic-preserving (AP) numerical method for solving the three-temperature radiative transfer model, which holds significant importance in inertial confinement fusion. A carefully designed splitting method is developed that can provide a general framework of the extending AP schemes for the gray radiative transport equation to the more complex three-temperature radiative transfer model. The proposed scheme captures two important limiting models: the three-temperature radiation diffusion equation (3TRDE) when opacity approaches infinity and the two-temperature limit when the ion-electron coupling coefficient goes to infinity. We have rigorously demonstrated the AP property and energy conservation characteristics of the proposed scheme and its efficiency has been validated through a series of benchmark tests in the numerical part. © 2024, The Authors. All rights reserved.

关键词： Radiative transfer

Cheaper and more noise-resilient quantum state preparation using eigenvector continuation

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arXiv 2024年

作者： Agrawal, Anjali A. Getelina, João C. Francis, Akhil Kemper, A.F. Department of Physics North Carolina State University RaleighNC27695 United States Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

Subspace methods are powerful, noise-resilient methods that can effectively prepare ground states on quantum computers. The challenge is to get a subspace with a small condition number that spans the states of interest using minimal quantum resources. In this work, we will use eigenvector continuation (EC) to build a subspace from the low-lying states of a set of Hamiltonians. The basis vectors are prepared using truncated versions of standard state preparation methods such as imaginary time evolution (ITE), adiabatic state preparation (ASP), and variational quantum eigensolver (VQE). By using these truncated methods combined with eigenvector continuation, we can directly improve upon them, obtaining more accurate ground state energies at a reduced cost. We use several spin systems to demonstrate convergence even when methods like ITE and ASP fail, such as ASP in the presence of level crossings and ITE with vanishing energy gaps. We also showcase the noise resilience of this approach beyond the gains already made by having shallower quantum circuits. Our findings suggest that eigenvector continuation can be used to improve existing state preparation methods in the near term. Copyright © 2024, The Authors. All rights reserved.

关键词： Hamiltonians

An asymptotic-preserving method for the three-temperature radiative transfer model

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arXiv 2024年

作者： Li, Ruo Li, Weiming Liang, Shengtong Shao, Yuehan Tang, Min Wang, Yanli CAPT LMAM & School of Mathematical Sciences Peking University Beijing China Institute of Applied Physics and Computational Mathematics Beijing China School of Mathematical Sciences Peking University Beijing China Institute of Natural Sciences School of Mathematics Shanghai Jiaotong University Shanghai China Beijing Computational Science Research Center Beijing China

We present an asymptotic-preserving (AP) numerical method for solving the three-temperature radiative transfer model, which holds significant importance in inertial confinement fusion. A carefully designed splitting method is developed that can provide a general framework of extending AP schemes for the gray radiative transport equation to the more complex three-temperature radiative transfer model. The proposed scheme captures two important limiting models: the three-temperature radiation diffusion equation (3TRDE) when opacity approaches infinity and the two-temperature limit when the ion-electron coupling coefficient goes to infinity. We have rigorously demonstrated the AP property and energy conservation characteristics of the proposed scheme and its efficiency has been validated through a series of benchmark tests in the numerical part. © 2024, CC0.

关键词： Radiative transfer