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Transport diffuse interface model for simulation of solid-fluid interaction

applied mathematics and Mechanics(English Edition) 2019年第3期40卷 321-330页

作者： Li LI Qian CHEN Baolin TIAN Institute of Applied Physics and Computational Mathematics

For solid-fluid interaction, one of the phase-density equations in diffuse interface models is degenerated to a "0 = 0" equation when the volume fraction of a certain phase takes the value of zero or unity. This is because the conservative variables in phasedensity equations include volume fractions. The degeneracy can be avoided by adding an artificial quantity of another material into the pure phase. However, nonphysical waves,such as shear waves in fluids, are introduced by the artificial treatment. In this paper,a transport diffuse interface model, which is able to treat zero/unity volume fractions, is presented for solid-fluid interaction. In the proposed model, a new formulation for phase densities is derived, which is unrelated to volume fractions. Consequently, the new model is able to handle zero/unity volume fractions, and nonphysical waves caused by artificial volume fractions are prevented. One-dimensional and two-dimensional numerical tests demonstrate that more accurate results can be obtained by the proposed model.

关键词： solid-fluid interaction diffuse interface model phase-density equation Mie-Gruneisen equation of state(EOS) Eulerian method

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Reduction of Backward Scatterings at the Low-Coherence Kunwu Laser Facility

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Physical Review Letters 2024年第3期132卷 035102-035102页

作者： Anle Lei Ning Kang Yao Zhao Huiya Liu Honghai An Jun Xiong Ruirong Wang Zhiyong Xie Yuchun Tu Guoxiao Xu Xichen Zhou Zhiheng Fang Wei Wang Lan Xia Wei Feng Xiaohui Zhao Lailin Ji Yong Cui Shenlei Zhou Zhanjun Liu Chunyang Zheng Lifeng Wang Yanqi Gao Xiuguang Huang Sizu Fu Shanghai Institute of Laser Plasma China Academy of Engineering Physics Shanghai 201800 China Key Laboratory of High Power Laser and Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China School of Science Shenzhen Campus of Sun Yat-sen University Shenzhen 518107 China University of Chinese Academy of Sciences Beijing 100049 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China

We report the first experimental observation on the reduction of backward scatterings by an instantaneous broadband laser with 0.6% bandwidth in conditions of interest for inertial confinement fusion at the low-coherence Kunwu laser facility. The backscatter of stimulated Brillouin scattering (SBS) was robustly reduced by half at intensities of 1–5×1014 W/cm2 with the 0.53−μm broadband laser in comparison with the monochromatic laser. As SBS dominates energy loss of laser-plasma interactions, the reduction of that demonstrates the enhancement of laser-target coupling by the use of broadband laser. The mitigation of filamentation leads to the reduction of stimulated Raman backscattering at low intensities. In addition, the three-halves harmonic emission was reduced with the broadband laser as well.

关键词： Direct drive Inertial confinement fusion Laser-plasma interactions Stimulated Brillouin & Raman scattering in plasmas Laser inertial confinement Coherent control Light scattering Particle-in-cell methods

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A BLOW-UP CRITERION OF STRONG SOLUTIONS TO THE QUANTUM HYDRODYNAMIC MODEL

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Acta Mathematica Scientia 2020年第3期40卷 795-804页

作者： Guangwu WANG Boling GUO School of Mathematics and Information Science Guangzhou UniversityGuangzhou 510006China Institute of Applied Physics and Computational Mathematics China Academy of Engineering PhysicsBeijing 100088China

In this article,we focus on the short time strong solution to a compressible quantum hydrodynamic *** establish a blow-up criterion about the solutions of the compressible quantum hydrodynamic model in terms of the gradient of the velocity,the second spacial derivative of the square root of the density,and the first order time derivative and first order spacial derivative of the square root of the density.

关键词： Compressible quantum hydrodynamic model blow-up criterion strong solution

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A two-stage fourth order temporal discretization of GRP-DG methods for compressible fluid dynamics I: One dimensional cases 6

A two-stage fourth order temporal discretization of GRP-DG m...

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6th ECCOMAS European Conference on computational Mechanics: Solids, Structures and Coupled Problems, ECCM 2018 and 7th ECCOMAS European Conference on computational Fluid Dynamics, ECFD 2018

作者： Wang, Yue Li, Jiequan Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Huayuan Road Haidian District Beijing10094 China

ISBN: (纸本)9788494731167

A two-stage fourth order temporal discretization approach is developed for compressible fluid dynamics in the framework of discontinuous Galerkin (DG) methods. Different from the classical Runge-Kutta (RK) temporal discretization, we use the two-stage temporal discretization and take the generalized Riemann problem (GRP) solver to construct numerical fluxes for better resolution. It turns out that we just need to solve moments and reconstruct initial data twice at every time step so as to save the computational cost and decrease the memory footprint. Numerical results verified the performance of the proposed scheme. copyright © Crown copyright (2018).All right reserved.

关键词： computational fluid dynamics

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Transfer learning of many-body electronic correlation entropy from local measurements

arXiv

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arXiv 2025年

作者： Aikebaier, Faluke Ojanen, Teemu Lado, Jose L. Department of Applied Physics Aalto University Espoo00076 Finland Computational Physics Laboratory Physics Unit Faculty of Engineering and Natural Sciences Tampere University TampereFI-33014 Finland Helsinki Institute of Physics P.O. Box 64 FI-00014 Finland

The characterization of quantum correlations in many-body systems is instrumental to understanding the nature of emergent phenomena in quantum materials. The correlation entropy serves as a key metric for assessing the complexity of a quantum many-body state in interacting electronic systems. However, its determination requires the measurement of all single-particle correlators across a macroscopic sample, which can be impractical. Machine learning methods have been shown to allow learning the correlation entropy from a reduced set of measurements, yet these methods assume that the targeted system is contained in the set of training Hamiltonians. Here we show that a transfer learning strategy enables correlation entropy learning from a reduced set of measurements in families of Hamiltonians never considered in the training set. We demonstrate this transfer learning methodology in a wide variety of interacting models including local and non-local attractive and repulsive many-body interactions, long range hopping, doping, magnetic field and spin-orbit coupling. Furthermore, we show how this transfer learning methodology allows detecting quantum many-body phases never observed during their training set without prior knowledge about them. Our results demonstrate that correlation entropy learning can be potentially performed experimentally without requiring training in the experimentally realized Hamiltonian. Copyright © 2025, The Authors. All rights reserved.

关键词： Hamiltonians

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Transition energies and oscillator strengths for the intrashell and intershell transitions of the C-like ions in a thermodynamic equilibrium plasma environment

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Physical Review E 2022年第1期105卷 015206-015206页

作者： Chensheng Wu Yong Wu Jun Yan T. N. Chang Xiang Gao Institute for Applied Physics and Computational Mathematics Beijing 100088 China Beijing Computational Science Research Center Beijing 100193 China Department of Physics University of Southern California Los Angeles California 90089-0484 USA Institute for Theoretical Physics Vienna University of Technology A-1040 Vienna Austria

We present a theoretical study of the transition energies ω and the oscillator strengths gf for the C-like ions (with Z from 14–36) subject to plasma environment for atomic transitions, which meet the spatial and temporal criteria of the Debye-Hückel (DH) approximation. Two strong dipole-allowed transitions, viz., the intrashell transition 2s2p33D1→2s22p23P0, and the intershell transition 2s22p3d3D1→2s22p23P0 are investigated in detail. We found that both ω and gf increase for the intrashell transition under the Debye-Hückel screening potential VDH in terms of the Debye length D, which is linked to the ratio between the plasma density Ne and its temperature kT. In contrast, both ω and gf decrease for the intershell transition. Our theoretically estimated data have led to a general scaling feature for the change in ω of both intershell and intrashell transitions for ions with different nuclear charge Z. A similar general feature for the change in gf is also found for the intrashell transition. However, due to the change of the electron correlations between electrons in different shells with respect to the relativistic spin-orbit interaction as Z varies, the variation of gf subject to the surrounding plasma is more complicated for the intershell transition. The results presented in this work may facilitate the plasma diagnostic to determine the plasma temperature and density for the astrophysical objects and the controlled fusion facilities.

关键词： Atomic & molecular processes in external fields Atomic & molecular structure Plasma-particle interactions

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Hilbert band complexes and their applications

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Physical Review B 2025年第7期111卷 075154-075154页

作者： Zeying Zhang Y. X. Zhao Yugui Yao Shengyuan A. Yang College of Mathematics and Physics Beijing University of Chemical Technology Beijing 100029 China Department of Physics and HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong The University of Hong Kong Pokfulam Road Hong Kong China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) Beijing Institute of Technology Beijing 100081 China Research Laboratory for Quantum Materials IAPME FST University of Macau Macau China

The study of band connectivity is a fundamental problem in condensed matter physics. Here, we develop a method for analyzing band connectivity, which completely solves the outstanding questions of the reducibility and decomposition of band complexes. By translating the symmetry conditions into a set of band balance equations, we show that all possible band structure solutions can be described by a positive affine monoid structure, which has a unique minimal set of generators, called Hilbert basis. We show that Hilbert basis completely determines whether a band complex is reducible and how it can be decomposed. The band complexes corresponding to Hilbert basis vectors, termed as Hilbert band complexes (HBCs), can be regarded as elementary building blocks of band structures. We develop algorithms to construct HBCs, analyze their graph features, and merge them into large complexes. We find some interesting examples, such as HBCs corresponding to complete bipartite graphs, and complexes that can grow without bound by successively merging a HBC.

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Dynamical Chiral Nernst Effect in Twisted Van der Waals Few Layers

arXiv

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arXiv 2024年

作者： Li, Juncheng Zhai, Dawei Xiao, Cong Yao, Wang New Cornerstone Science Laboratory Department of Physics The University of Hong Kong Hong Kong HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong Hong Kong Institute of Applied Physics and Materials Engineering University of Macau Taipa China

The Nernst effect is a fundamental thermoelectric conversion phenomenon that was deemed to be possible only in systems with magnetic field or magnetization. In this work, we propose a novel dynamical chiral Nernst effect that can appear in two-dimensional van der Waals materials with chiral structural symmetry in the absence of any magnetic degree of freedom. This unconventional effect is triggered by time variation of an out-of-plane electric field, and has an intrinsic quantum geometric origin linked to not only the intralayer center-of-mass motion but also the interlayer coherence of electronic states. We demonstrate the effect in twisted homobilayer and homotrilayer transition metal dichalcogenides, where the strong twisted interlayer coupling leads to sizable intrinsic Nernst conductivities well within the experimental capacity. This work suggests a new route for electric control of thermoelectric conversion. Copyright © 2024, The Authors. All rights reserved.

关键词： Transition metals

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Ellipticity of the harmonic emission from graphene irradiated by a linearly polarized laser

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Physical Review A 2021年第3期104卷 033119-033119页

作者： Fulong Dong Qinzhi Xia Jie Liu Graduate School China Academy of Engineering Physics Beijing 100193 China National Laboratory of Science and Technology on Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China

We investigate the high-order harmonic generation in graphene irradiated by a linearly polarized intense laser, addressing the ellipticity or polarization properties of the harmonics. We exploit time-dependent density functional theory to calculate the harmonic spectra for a laser wavelength of 4770 nm and an intensity of 1.7 TW/cm2, and our numerical results can qualitatively reproduce recent experimental data. Our simulations also reveal that the harmonic ellipticity depends on both the harmonic order and the orientation angle between the graphene symmetric axis and the laser polarization direction. It can reach 0.68 for the ninth-order harmonic at the orientation angle of 20∘. To understand the mechanism of the high ellipticity, we develop a two-band model based on the tight-binding approximation. We may explain the ellipticity of high-order harmonic generation by investigating the transition dipole moments in the two-band model. Our theory further predicts a sensitive dependence of the harmonic ellipticity on the laser intensity for various laser wavelengths.

关键词： High-order harmonic generation Graphene Polarization Dipole approximation Tight-binding model Time-dependent DFT

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A DOFs condensation based algorithm for solving saddle point systems in contact computation

arXiv

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arXiv 2024年

作者： Duan, Xiaoyu An, Hengbin Mo, Zeyao Institute of Applied Physics and Computational Mathematics Beijing100094 China Graduate School of China Academy of Engineering Physics Beijing100088 China CAEP Software Center for High Performance Numerical Simulation Beijing100088 China

In contact mechanics computation, the constraint conditions on the contact surfaces are typically enforced by the Lagrange multiplier method, resulting in a saddle point system. The mortar finite element method is usually employed to discretize the variational form on the meshed contact surfaces, leading to a large-scale discretized saddle point system. Due to the indefiniteness of the discretized system, it is a challenge to solve the saddle point algebraic system. For two-dimensional tied contact problem, an efficient DOFs condensation technique is developed. The essential of the proposed method is to carry out the DOFs elimination by using the tridiagonal characteristic of the mortar matrix. The scale of the linear system obtained after DOFs elimination is smaller, and the matrix is symmetric positive definite. By using the preconditioned conjugate gradient (PCG) method, the linear system can be solved efficiently. Numerical results show the effectiveness of the method. Copyright © 2024, The Authors. All rights reserved.

关键词： Lagrange multipliers

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