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Fragmentation dynamics of electron-impact double ionization of helium

Chinese physics B 2023年第6期32卷 9-15页

作者：刘士炜叶地发刘杰 Beijing Computational Science Research Center Beijing 100193China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Graduate School China Academy of Engineering PhysicsBeijing 100193China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.

关键词： double ionization classical trajectory Monte Carlo simulation Wannier threshold law ergodicity

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Strain concentration factor of heterogeneous materials and analytical influence functions based on Eshelby tensor

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Theoretical & applied Mechanics Letters 2024年第4期14卷 306-313页

作者： Shanqiao Huang Zifeng Yuan HEDPS Center for Applied Physics and TechnologyDepartment of Mechanics and Engineering SciencePeking UniversityBeijing 100871China State Key Laboratory for Turbulence and Complex Systems Peking UniversityBeijing 100871China

In this manuscript,Eshelby tensor is employed to assess the strain concentration that arises in the matrix phase at the interface,offering precise values and locations of maximum strain under specific loading conditions for both spherical and cylindrical *** compared to numerical simulation results,the analytical predictions grounded in the Eshelby tensor exhibit satisfactory *** an analytical calculation method based on Eshelby tensor for the elastic strain influence functions of reduced-order homogenization(ROH)method is developed and adopted on particle-reinforced and fibrous composites,presenting its feasibility and advantage on off-line stage calculation of ROH *** error analyses between analytical and numerical results are *** numerical results also exhibit the necessity of finer interface partitioning to obtain the response on micro-scale with higher resolution.

关键词： Eshelby tensor Strain concentration Composite structures Reduced-order-homogenization Influence functions

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Globally hyperbolic moment model of arbitrary order for the three-dimensional special relativistic Boltzmann equation with the Anderson-Witting collision

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Science China Mathematics 2022年第5期65卷 1029-1064页

作者： Yangyu Kuang Huazhong Tang Center for Applied Physics and Technology HEDPS and LMAMSchool of Mathematical SciencesPeking UniversityBeijing 100871China

This paper continues to derive the globally hyperbolic moment model of arbitrary order for the three-dimensional special relativistic Boltzmann equation with the Anderson-Witting *** method is the model reduction by the operator *** an orthogonal basis of the weighted polynomial space is crucial and built on infinite families of the complicate relativistic Grad type orthogonal polynomials depending on a parameter and the real spherical harmonics instead of the irreducible *** study the properties of those functions carefully,including their recurrence relations,their derivatives with respect to the independent variable and the parameter,and the zeros of the orthogonal *** moment model is proved to be globally hyperbolic and linearly ***,the Lorentz covariance,the quasi-one-dimensional case,and the non-relativistic and ultra-relativistic limits are also studied.

关键词： moment method hyperbolicity special relativistic Boltzmann equation model reduction operator projection

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Spectroscopy and scattering matrices with nitrogen atom:Rydberg states and optical oscillator strengths

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Chinese physics B 2022年第4期31卷 261-266页

作者： Yuhao Zhu Rui Jin Yong Wu Jianguo Wang Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Center for Free-Electron Laser Science DESYHamburg 22607Germany HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China

The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix *** obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering *** employing the MQDT,all discrete energy levels for N could be calculated accurately without missing *** MQDT parameters(i.e.,scattering matrices)can be calibrated with the available precise spectroscopy *** this work,the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained,which provide rich data for the diagnostic analysis of plasma.

关键词： eigenchannel R-matrix oscillator strengths

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Analysis of the nonlinear scheme preserving the maximum principle for the anisotropic diffusion equation on distorted meshes

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Science China Mathematics 2022年第11期65卷 2379-2396页

作者： Zhiqiang Sheng Guangwei Yuan Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

In this paper,a nonlinear finite volume scheme preserving the discrete maximum principle for the anisotropic diffusion equation on distorted meshes is *** prove the coercivity of the scheme under some constraints on the cell deformation and the diffusion *** results show that the scheme is indeed coercive and satisfies the discrete maximum principle,and the accuracy of this scheme is remarkably better than that of an existing scheme preserving the discrete maximum principle on random triangular meshes.

关键词： coercivity discrete maximum principle nonlinear finite volume scheme distorted meshes

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MONOTONICITY CORRECTIONS FOR NINE-POINT SCHEME OF DIFFUSION EQUATIONS

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Journal of Computational Mathematics 2024年第5期42卷 1305-1327页

作者： Wang Kong Zhenying Hong Guangwei Yuan Zhiqiang Sheng School of Mathematics Nanjing University of Aeronautics and AstronauticsNanjing 211106China Key Laboratory of Mathematical Modelling and High Performance Computing of Air Vehicles(NUAA) MIITNanjing 211106China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China

In this paper,we present a nonlinear correction technique to modify the nine-point scheme proposed in[SIAM ***.,30:3(2008),1341-1361]such that the resulted scheme preserves the *** first express the flux by the cell-centered unknowns and edge unknowns based on the stencil of the nine-point ***,we use a nonlinear combination technique to get a monotone *** order to obtain a cell-centered finite volume scheme,we need to use the cell-centered unknowns to locally approximate the auxiliary *** present a new method to approximate the auxiliary unknowns by using the idea of an improved multi-points flux *** numerical results show that the new proposed scheme is robust,can handle some distorted grids that some existing finite volume schemes could not handle,and has higher numerical accuracy than some existing positivity-preserving finite volume schemes.

关键词： Monotonicity corrections Diffusion equation Improved MPFA Distorted meshes

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Spectroscopy and molecule opacity investigation on excited states of SiS

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Chinese physics B 2024年第5期33卷 381-387页

作者：李瑞吕浩男桑纪群刘晓华梁桂颖吴勇 College of Teacher Education Qiqihar UniversityQiqihar 161006China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Department of Physics College of ScienceQiqihar UniversityQiqihar 161006China School of Data Science and Artificial Intelligence Jilin Engineering Normal UniversityChangchun 130052China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China

The SiS molecule,which plays a significant role in space,has attracted a great deal of attention for many *** to complex interactions among its low-lying electronic states,precise information regarding the molecular structure of SiS is *** obtain accurate information about the structure of its excited states,the high-precision multireference configuration interaction(MRCI)method has been *** method is used to calculate the potential energy curves(PECs)of the 18Λ–S states corresponding to the lowest dissociation limit of *** core–valence correlation effect,Davidson’s correction and the scalar relativistic effect are also included to guarantee the precision of the MRCI *** on the calculated PECs,the spectroscopic constants of quasi-bound and bound electronic states are calculated and they are in accordance with previous experimental *** transition dipole moments(TDMs)and dipole moments(DMs)are determined by the MRCI *** addition,the abrupt variations of the DMs for the 1^(5)Σ^(+)and 2^(5)Σ^(+)states at the avoided crossing point are attributed to the variation of the electronic *** opacity of SiS at a pressure of 100 atms is presented across a series of *** increasing temperature,the expanding population of excited states blurs the band boundaries.

关键词： SiS opacity excited state spectroscopic constant configuration interaction

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A Finite Volume Method Preserving Maximum Principle for the Conjugate Heat Transfer Problems with General Interface Conditions

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Journal of Computational Mathematics 2023年第3期41卷 345-369页

作者： Huifang Zhou Zhiqiang Sheng Guangwei Yuan School of Mathematics Jilin UniversityChangchun 130012China The Graduate School of China Academy of Engineering Physics Beijing 100088China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

In this paper,we present a unified finite volume method preserving discrete maximum principle(DMP)for the conjugate heat transfer problems with general interface *** prove the existence of the numerical solution and the DMP-preserving *** experiments show that the nonlinear iteration numbers of the scheme in[24]increase rapidly when the interfacial coefficients decrease to *** contrast,the nonlinear iteration numbers of the unified scheme do not increase when the interfacial coefficients decrease to zero,which reveals that the unified scheme is more robust than the scheme in[24].The accuracy and DMP-preserving property of the scheme are also veri ed in the numerical experiments.

关键词： Conjugate heat transfer problems General interface conditions Finite volume scheme Discrete maximum principle

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Recent progress on thermal conductivity of graphene filled epoxy composites

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Nano Materials Science 2022年第3期4卷 205-219页

作者： Ruicong Lv Yanjuan Ren Haichang Guo Shulin Bai School of Materials Science and Engineering HEDPS/Center for Applied Physics and TechnologyKey Laboratory of Polymer Chemistry and Physics of Ministry of EducationPeking UniversityBeijing100871China

With the rapid development of the electronic industry, the requirements for packaging materials with high thermal conductivity(TC) are getting higher and higher. Epoxy is widely used as package material for electronic package applications. But it’s intrinsic TC can’t meets the increasing demands. Adding high TC graphene into epoxy matrix is a proper way to reinforce epoxy composites. This review focuses on the filler modification,preparation process and thermal properties of graphene-filled epoxy resin composites. Different ways of covalent and non-covalent modification methods are discussed. The various kinds of graphene coating layer are also summarized. Then we analysis the hybrid filler system in epoxy composite. We hope this review will provide guidance for the development and application of graphene-filled epoxy resin composites.

关键词： Graphene Epoxy Composites Thermal conductivity

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A High Order Positivity-Preserving Discontinuous Galerkin Remapping Method Based on a Moving Mesh Solver for ALE Simulation of the Compressible Fluid Flow

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Communications in Computational physics 2023年第10期34卷 1177-1214页

作者： Xiaolu Gu Juan Cheng Chi-Wang Shu Graduate School China Academy of Engineering PhysicsBeijing 100088China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China Division of Applied Mathematics Brown UniversityProvidenceRI 02912

The arbitrary Lagrangian-Eulerian(ALE)method is widely used in the field of compressible multi-material and multi-phase flow *** order to implement the indirect ALE approach for the simulation of compressible flow in the context of high order discontinuous Galerkin(DG)discretizations,we present a high order positivity-preserving DG remapping method based on a moving mesh solver in this *** remapping method is based on the ALE-DG method developed by Klingenberg et al.[17,18]to solve the trivial equation∂u/∂t=0 on a moving mesh,which is the old mesh before remapping at t=0 and is the new mesh after remapping at t=*** appropriate selection of the final pseudo-time T can always satisfy the relatively mild smoothness requirement(Lipschitz continuity)on the mesh movement velocity,which guarantees the high order accuracy of the remapping *** use a multi-resolution weighted essentially non-oscillatory(WENO)limiter which can keep the essentially non-oscillatory property near strong discontinuities while maintaining high order accuracy in smooth *** further employ an effective linear scaling limiter to preserve the positivity of the relevant physical variables without sacrificing conservation and the original high order *** experiments are provided to illustrate the high order accuracy,essentially non-oscillatory performance and positivity-preserving of our remapping *** addition,the performance of the ALE simulation based on the DG framework with our remapping algorithm is examined in one-and two-dimensional Euler equations.

关键词： Remapping discontinuous Galerkin method arbitrary Lagrangian-Eulerian high order accuracy multi-resolution WENO limiter positivity-preserving

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