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Suppression of stimulated Brillouin and Raman scatterings using an alternating frequency laser and transverse magnetic fields

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Chinese physics B 2024年第1期33卷 545-553页

作者：程瑞锦李晓旬王清刘德基黄卓明吕帅宇周远志张舒童李雪铭陈祖杰王强刘占军曹莉华郑春阳 Institute of Applied Physics and Computational Mathematics Beijing 100094China HEDPS Center for Applied Physics and Technologyand State Key Laboratory of Nuclear Physics and TechnologySchool of PhysicsPeking UniversityBeijing 100871China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

A novel scheme to suppress both stimulated Brillouin scattering(SBS) and stimulated Raman scattering(SRS) by combining an alternating frequency(AF) laser and a transverse magnetic field is proposed. The AF laser allows the laser frequency to change discretely and alternately over time. The suppression of SBS is significant as long as the AF difference is greater than the linear growth rate of SBS or the alternating time of the laser frequency is shorter than the linear growth time of SBS. However, the AF laser proves ineffective in suppressing SRS, which usually has a much higher linear growth rate than SBS. To remedy that, a transverse magnetic field is included to suppress the SRS instability. The electrons trapped in the electron plasma waves(EPWs) of SRS can be accelerated by the surfatron mechanism in a transverse magnetic field and eventually detrapped. While continuously extracting energy from EPWs, the EPWs are dissipated and the kinetic inflation of SRS is suppressed. The one-dimensional particle-in-cell simulation results show that both SBS and SRS can be effectively suppressed by combining the AF laser with a transverse magnetic field with tens of Tesla. The total reflectivity can be dramatically reduced by more than one order of magnitude. These results provide a potential reference for controlling SBS and SRS under the related parameters of inertial confinement fusion.

关键词： stimulated Brillouin scattering stimulated Raman scattering alternating frequency laser transverse magnetic field

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A Composite Ansatz for Calculation of Dynamical Structure Factor

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Chinese physics Letters 2024年第1期41卷 92-103页

作者：张玉佩莫崇杰张平康炜 HEDPS Center for Applied Physics and Technologyand School of PhysicsPeking UniversityBeijing 100871China Beijing Computational Science Research Center Beijing 100193China Institute of Applied Physics and Computational Mathematics Beijing 100088China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

We propose an ansatz without adjustable parameters for the calculation of a dynamical structure *** ansatz combines the quasi-particle Green’s function,especially the contribution from the renormalization factor,and the exchange-correlation kernel from time-dependent density functional theory together,verified for typical metals and semiconductors from a plasmon excitation regime to the Compton scattering *** has the capability to reconcile both small-angle and large-angle inelastic x-ray scattering(IXS)signals with muchimproved accuracy,which can be used as the theoretical base model,in inversely inferring electronic structures of condensed matter from IXS experimental signals *** may also be used to diagnose thermal parameters,such as temperature and density,of dense plasmas in x-ray Thomson scattering experiments.

关键词： excitation inverse verified

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Vibronic effect study of ^(1)A_(2) state of H_(2)O and D_(2)O

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Chinese physics B 2024年第5期33卷 395-399页

作者：张倍源王礼涵朱剑辉徐卫青马子茹赵小利吴勇朱林繁 Department of Modern Physics University of Science and Technology of ChinaHefei 230026China Center for Transformative Science ShanghaiTech UniversityShanghai 201210China Department of Physics Yantai UniversityYantai 264005China Institute of Applied Physics and Computational Mathematics Beijing 100088China School of Physics and Information Technology Shaanxi Normal UniversityXi'an 710119China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China

The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic *** is found that the vibronic effect converts the dipole-forbidden excitation of the ^(1)A_(2) into a dipole-allowed one,which enhances the intensities of the corresponding generalized oscillator strength in the small squared momentum transfer *** present investigation shows that the vibronic effect of H_(2)O is slightly stronger than that of D_(2)O,which exhibits a clear isotopic effect.

关键词： water heavy water generalized oscillator strength vibronic effect isotope effect

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Prediction of superionic state in LiH_(2) at conditions enroute to nuclear fusion

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Chinese physics B 2023年第10期32卷 566-571页

作者：李福德王豪李津龙耿华运 National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsCAEPMianyang 621900China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

Hydrogen and lithium,along with their compounds,are crucial materials for nuclear fusion ***-pressure studies have revealed intricate structural transitions in all these ***,research on lithium hydrides beyond LiH has mostly focused on the low-temperature ***,we use density functional theory and ab initio molecular dynamics simulations to investigate the behavior of LiH_(2),a hydrogen-rich compound,near its melting *** study is particularly relevant to the low-pressure region of the compression pathway of lithium hydrides toward *** discovered a premelting superionic phase transition in LiH_(2)that has significant implications for its mass transportation,elastic properties,and sound *** theoretical boundary for the superionic transition and melting temperature was then *** contrast,we also found that the primary compound of lithium hydrides,LiH,does not exhibit a superionic *** findings have important implications for optimizing the compression path to achieve the ignition condition in inertial confinement fusion research,especially when lithium tritium-deuteride(LiTD)is used as the fuel.

关键词： lithium polyhydrides high pressure and high temperature superionic state phase transition

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A CELL-centerED GODUNOV METHOD BASED ON STAGGERED DATA DISTRIBUTION,PART Ⅰ:ONE-DIMENSIONAL CASE

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Journal of Computational Mathematics 2024年第4期42卷 1172-1196页

作者： Jiayin Zhai Xiao Li Zhijun Shen Institute of Applied Physics and Computational Mathematics LCPP.O.Box 8009-26Beijing 100088China College of Big Data and Internet Shenzhen Technology UniversityShenzhen 518118China Center for Applied Physics and Technology HEDPSPeking UniversityChina

This paper presents a cell-centered Godunov method based on staggered data distribu-tion in Eulerian *** motivation is to reduce the intrinsic entropy dissipation of classical Godunov methods in the calculation of an isentropic or rarefaction *** the same time,the property of accurate shock capturing is also *** analyzing the factors that cause nonphysical entropy in the conventional Godunov methods,we introduce two velocities rather than a single velocity in a cell to reduce kinetic energy dissipation.A series of redistribution strategies are adopted to update subcell quantities in order to improve *** examples validate that the present method can dramatically reduce nonphysical entropy *** subject classification:35Q35,76N15,76M12.

关键词： Godunov method Riemann solver Rarefaction wave Nonphysical entropy increase.

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First-principles study of structural and electronic properties of multiferroic oxide Mn_(3)TeO_(6) under high pressure

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Chinese physics B 2024年第7期33卷 448-454页

作者：潘小龙王豪柳雷陈向荣耿华运 College of Physics Sichuan UniversityChengdu 610065China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsChina Academy of Engineering PhysicsMianyang 621900China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

Mn_(3)TeO_(6)(MTO) has been experimentally found to adopt a P2_(1)/In structure under high pressure,which exhibits a significantly smaller band gap compared to the atmospheric R3 *** this study,we systematically investigate the magnetism,structural phase transition,and electronic properties of MTO under high pressure through first-principles *** R3 and P2_(1)/n phases of MTO are antiferromagnetic at zero *** R3 phase transforms to the P2_(1)/n phase at 7.5 8 GPa,accompanied by a considerable volume collapse of about 6.47%.Employing the accurate method that combines DFT+U/and GW,the calculated band gap of R3 phase at zero pressure is very close to the experimental values,while that of the P2_(1)/n phase is significantly *** main reason for this difference is that the experimental study incorrectly used the Kubelka-Munk plot for the indirect band gap to obtain the band gap of the P2_(1)/n phase instead of the Kubelka-Munk plot for the direct band ***,our study reveals that the transition from the R3 phase to the P2_(1)/n phase is accompanied by a slight reduction in the band gap.

关键词： magnetism phase transition band gap high pressure

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Theoretical study of electron-impact broadening for highly charged Ar XV ion lines

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Chinese physics B 2023年第5期32卷 49-56页

作者：吴超高翔朱宇豪韩小英段斌孟举张松斌颜君吴勇王建国 National Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China School of Physics and Information Technology Shaanxi Normal UniversityXi’an 710119China School of Science Xi’an University of Architecture and TechnologyXi’an 710055China

Spectral line widths produced by collisions between charged particles and emitters are of special interest for precise plasma *** highly charged Ar XV ion is demonstrated to have strong intrashell electron interactions,which manifest as an atomic system with many resonance structures,due to the quasi-degeneracy of orbital *** this paper we use the relativistic R-matrix method to investigate the electron-impact broadening of highly charged Ar XV ion spectral lines under the impact *** is found that the results considering resonance structures are significantly different from those of the distorted wave ***,we propose a new empirical formula with a correction term to take into account the effect of resonances for electron-impact widths over a relatively wide range of plasma *** corresponding fitting parameters of the new empirical formula for all 47 calculated transitions are also given with an estimated accuracy within 1%,which should be convenient for practical *** dataset that supported the findings of this study is available in Science Data Bank,with the link https://***/10.57760/sciencedb.j00113.00101.

关键词： highly charged ions electron-impact broadening empirical formula

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Toward Analytical Homogenized Relaxation Modulus for Fibrous Composite Material with Reduced Order Homogenization Method

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Computers, Materials & Continua 2025年第1期82卷 193-222页

作者： Huilin Jia Shanqiao Huang Zifeng Yuan HEDPS Center for Applied Physics and Technology(CAPT)Department of Mechanics and Engineering SciencePeking UniversityBeijing100871China State Key Laboratory for Turbulence and Complex Systems Peking UniversityBeijing100871China

In this manuscript,we propose an analytical equivalent linear viscoelastic constitutive model for fiber-reinforced composites,bypassing general computational *** method is based on the reduced-order homogenization(ROH)*** ROH method typically involves solving multiple finite element problems under periodic conditions to evaluate elastic strain and eigenstrain influence functions in an‘off-line’stage,which offers substantial cost savings compared to direct computational homogenization *** to the unique structure of the fibrous unit cell,“off-line”stage calculation can be eliminated by influence functions obtained *** the standard solid model to the ROH method enables the creation of a comprehensive analytical homogeneous viscoelastic constitutive *** method treats fibrous composite materials as homogeneous,anisotropic viscoelastic materials,significantly reducing computational time due to its analytical *** approach also enables precise determination of a homogenized anisotropic relaxation modulus and accurate capture of various viscoelastic responses under different loading *** sets of numerical examples,including unit cell tests,three-point beam bending tests,and torsion tests,are given to demonstrate the predictive performance of the homogenized viscoelastic ***,the model is validated against experimental measurements,confirming its accuracy and reliability.

关键词： Homogenized relaxation modulus viscoelastic standard solid model reduced order homogenization fibrous composite material

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ON THE EXPLICIT TWO-STAGE FOURTH-ORDER ACCURATE TIME DISCRETIZATIONS

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Journal of Computational Mathematics 2023年第2期41卷 305-324页

作者： Yuhuan Yuan Huazhong Tang Center for Applied Physics and Technology HEDPS and LMAMSchool of Mathematical SciencesPeking UniversityBeijing 100871China Nanchang Hangkong University Nanchang 330063China

This paper continues to study the explicit two-stage fourth-order accurate time discretizations[5-7].By introducing variable weights,we propose a class of more general explicit one-step two-stage time discretizations,which are different from the existing methods,*** Euler methods,Runge-Kutta methods,and multistage multiderivative methods *** study the absolute stability,the stability interval,and the intersection between the imaginary axis and the absolute stability *** results show that our two-stage time discretizations can be fourth-order accurate conditionally,the absolute stability region of the proposed methods with some special choices of the variable weights can be larger than that of the classical explicit fourth-or fifth-order Runge-Kutta method,and the interval of absolute stability can be almost twice as much as the *** numerical experiments are carried out to demonstrate the performance and accuracy as well as the stability of our proposed methods.

关键词： Multistage multiderivative methods Runge-Kutta methods Absolute stability region Interval of absolute stability

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The High-Order Variable-Coefficient Explicit-Implicit-Null Method for Diffusion and Dispersion Equations

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应用数学与计算数学学报 2025年第1期7卷 115-150页

作者： Meiqi Tan 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 TechnologyCollege of EngineeringPeking UniversityBeijing 100871China Division of Applied Mathematics Brown UniversityProvidenceRI 02912USA

For the high-order diffusion and dispersion equations,the general practice of the explicit-implicit-null(EIN)method is to add and subtract an appropriately large linear highest derivative term with a constant coefficient at one side of the equation,and then apply the standard implicit-explicit method to the equivalent *** call this approach the con-stant-coefficient EIN method in this paper and hereafter denote it by"CC-EIN".To reduce the error in the CC-EIN method,the variable-coefficient explicit-implicit-null(VC-EIN)method,which is obtained by adding and subtracting a linear highest derivative term with a variable coefficient,is proposed and studied in this *** with the local discon-tinuous Galerkin(LDG)spatial discretization,the VC-EIN method is shown to be uncon-ditionally stable and can achieve high order of accuracy for both one-dimensional and two-dimensional quasi-linear and nonlinear *** addition,although the computational cost slightly increases,the VC-EIN method can obtain more accurate results than the CC-EIN method,if the diffusion coefficient or the dispersion coefficient has a few high and narrow bumps and the bumps only account for a small part of the whole computational domain.

关键词： Diffusion equation Dispersion equation Stability Explicit-implicit-null(EIN)time discretization Local discontinuous Galerkin(LDG)method

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