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A low Mach number asymptotic analysis of dissipation-reducing methods for curing shock instability

applied Mathematics and Mechanics(English Edition) 2025年第4期46卷 723-744页

作者： Hongping GUO Xun WANG Zhijun SHEN National Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing100088China Faculty of Mathematics Baotou Teachers’CollegeBaotouInner Mongolia Autonomous Region014030China School of Mathematical Sciences Peking UniversityBeijing100871China PKU-Changsha Institute for Computing and Digital Economy Changsha410205China Center for Applied Physics and Technology Peking UniversityBeijing100871China

We are intrigued by the issues of shock instability,with a particular emphasis on numerical schemes that address the carbuncle phenomenon by reducing dissipation rather than increasing *** a specific class of planar flow fields where the transverse direction exhibits vanishing but non-zero velocity components,such as a disturbed onedimensional(1D)steady shock wave,we conduct a formal asymptotic analysis for the Euler system and associated numerical *** analysis aims to illustrate the discrepancies among various low-dissipative numerical ***,a numerical stability analysis of steady shock is undertaken to identify the key factors underlying shock-stable *** verify the stability mechanism,a consistent,low-dissipation,and shock-stable HLLC-type Riemann solver is presented.

关键词： Riemann solver numerical shock instability low Mach number HLLC

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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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Fundamental influence of irreversible stress-strain properties in solids on the validity of the ramp loading method

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Matter and Radiation at Extremes 2024年第6期9卷 94-104页

作者： Jingxiang Shen Wei Kang Center for Applied Physics and Technology and College of EngineeringPeking UniversityBeijing 100871China

The widely used quasi-isentropic ramp loading technique relies heavily on back-calculation methods that convert the measured free-surface velocity profiles to the stress-density states inside the compressed *** back-calculation methods are based on one-dimensional isentropic hydrodynamic equations,which assume a well-defined functional relationship P(p)between the longitudinal stress and density throughout the entire flow ***,this kind of idealized stress-density relation does not hold in general,because of the complexities introduced by structural phase transitions and/or elastic-plastic *** and to what extent these standard back-calculation methods may be affected by such inherent complexities is still an unsettled ***,we present a close examination using large-scale molecular dynamics(MD)simulations that include the detailed physics of the irreversibly compressed solid *** back-calculate the stress-density relation from the MD-simulated rear surface velocity profiles and compare it directly against the stress-density trajectories measured from the MD simulation *** exist in the cases studied here,and these turn out to be related to the irreversibility between compression and *** and compression waves are observed to propagate with different sound velocities in some parts of the flow field,violating the basic assumption of isentropic hydrodynamic models and thus leading to systematic back-calculation *** particular,the step-like feature of the P(p)curve corresponding to phase transition may be completely missed owing to these *** kind of mismatch between inherent properties of matter and the basic assumptions of isentropic hydrodynamics has a fundamental influence on how the ramp loading method can be applied.

关键词： field. irreversible solids

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Interlayer Magnetic Interaction in the CrI_(3)/CrSe_(2) Heterostructure

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Chinese physics Letters 2024年第5期41卷 85-89页

作者：王秋皓倪美燕李淑静郑法伟路洪艳张平 School of Physics and Physical Engineering Qufu Normal UniversityQufu 273165China Center for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and MeasurementSchool of PhysicsBeijing Institute of TechnologyBeijing 100081China Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems School of PhysicsBeijing Institute of TechnologyBeijing 100081China College of Mathematics and Physics Beijing University of Chemical TechnologyBeijing 100029China Institute of Applied Physics and Computational Mathematics Beijing 100088China

Based on first-principles calculations, we systematically study the stacking energy and interlayer magnetic interaction of the heterobilayer composed of CrI_(3) and CrSe_(2) monolayers. It is found that the stacking order plays a crucial role in the interlayer magnetic coupling. Among all possible stacking structures, the AA-stacking is the most stable heterostructure, exhibiting interlayer antiferromagnetic interactions. Interestingly, the interlayer magnetic interaction can be effectively tuned by biaxial strain. A 4.3% compressive strain would result in a ferromagnetic interlayer interaction in all stacking orders. These results reveal the magnetic properties of CrI_(3)/CrSe_(2) heterostructure, which is expected to be applied to spintronic devices.

关键词： strain stacking interlayer

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Orbital-designed flat-band model and realization of superconductivity in three-dimensional materials

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Physical Review B 2024年第18期109卷 L180504-L180504页

作者： Yueshao Zheng Leiqiang Li Nannan Luo Li-Ming Tang Yexin Feng Ke-Qiu Chen Zhenyu Zhang Jiang Zeng Department of Applied Physics School of Physics and Electronics Hunan University Changsha 410082 China Minjiang Collaborative Center for Theoretical Physics College of Physics and Electronic Information Engineering Minjiang University Fuzhou 350108 China International Center for Quantum Design of Functional Materials (ICQD) Hefei National Research Center for Physical Sciences at the Microscale University of Science and Technology of China Hefei 230026 China

Electronic materials with a flat-band provide a fertile foundation for exploiting emerging quantum phenomena. Progress has been made in various two-dimensional (2D) systems, especially in a geometric frustrated kagome lattice system and a moire superlattice system for the study of unconventional superconductivity. However, intrinsic superconductivity has not yet been reported in 3D flat-band systems. The orbital degree of freedom might bring new vitality into the field of flat bands and superconductivity. Here, we propose an orbital-designed 3D flat-band model and its realization in various materials containing degenerate p-electrons, d-electrons, or molecular orbitals. More importantly, the possibility of superconductivity in some of these 3D flat-band materials, e.g., K2Pb and K2Bi, is revealed via first-principles calculations. Interestingly, these are intrinsically multiband superconductors. Our findings would expand the scope of flat-band studies, shedding light on the exploration of interacting effects and emerging quantum phases in 3D materials.

关键词： Electrical properties First-principles calculations Flat bands Multiband superconductivity

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Structural, magnetic, DC resistivity and dielectric properties of Ni-doped strontium hexaferrites SrNixFe12-xO19

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Ceramics International 2025年第15期51卷 20143-20163页

作者： Parajuli, D. Murali, N. Samatha, K. Research Center for Applied Science and Technology Tribhuvan University Kathmandu Kirtipur44613 Nepal Andhra Pradesh Visakhapatnam530003 India Department of Physics College of Science and Technology Andhra University Visakhapatnam530003 India

Nickel-doped strontium hexaferrites, SrNixFe12-xO19 (x = 0.00, 0.03, 0.06, 0.09, 0.12), were synthesized using the co-precipitation method. X-ray diffraction (XRD) analysis confirmed the formation of an M-type hexagonal structure (P63/mmc, JCPDS card no: 33–1340), with secondary phases (α-Fe2O3 and NiFe2O4) emerging at higher Ni concentrations (x ≥ 0.06). Lattice parameters and X-ray density were found to increase with Ni substitution. Pure hexaferrite phases were maintained for x ≤ 0.03, while additional phases appeared for x > 0.03. Scanning electron microscopy (SEM) revealed well-defined hexagonal plate-like grains, with a minimum grain size of 675.65 nm observed at x = 0.06. Magnetic characterization showed a decrease in saturation magnetization (Ms), remanence (Mr), and coercivity (Hc), with the lowest values of 46.89 emu/g, 28.22 emu/g, and 3673.88 Oe, respectively, at x = 0.06. The samples exhibited single-domain behavior with remanence ratios (Mr/Ms) ranging between 0.6018 and 0.6966. DC resistivity measurements indicated semiconducting behavior, with resistivity increasing as temperature decreased. The dielectric constant and loss factor decreased with increasing Ni content, the electric modulus, and impedance analysis suggesting a non-Debye type of relaxation with suitability for high-frequency applications. These findings demonstrate that Ni-doped strontium hexaferrites possess tunable structural, magnetic, and dielectric properties, making them promising candidates for use in high-frequency, low-loss devices such as capacitors, filters, and energy storage applications. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Saturation magnetization

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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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Practical GHz single-cavity all-fiber dual-comb laser for high-speed spectroscopy

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光：科学与应用（英文版） 2025年第5期14卷 1354-1363页

作者： Lin Ling Wei Lin Zhaoheng Liang Minjie Pan Chiyi Wei Xuewen Chen Yang Yang Zhijin Xiong Yuankai Guo Xiaoming Wei Zhongmin Yang School of Physics and Optoelectronics South China University of TechnologyGuangzhouChina School of Physics and Optoelectronics South China University of TechnologyGuangzhouChina School of Materials Science and Engineering Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques South China University of TechnologyGuangzhouChina School of Physics and Optoelectronics South China University of TechnologyGuangzhouChina School of Materials Science and Engineering Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques South China University of TechnologyGuangzhouChina Research Institute of Future Technology South China Normal UniversityGuangzhouChina

Dual-comb spectroscopy(DCS)with few-GHz tooth spacing that provides a better trade-off between spectral resolution and refresh rate is a powerful tool for measuring and analyzing rapidly evolving transient *** such an exciting opportunity,existing technologies compromise either the spectral resolution or refresh rate,leaving few-GHz DCS with robust design largely unmet for frontier *** this work,we demonstrate a novel GHz DCS by exploring the multimode interference-mediated spectral filtering effect in an all-fiber ultrashort cavity *** GHz single-cavity all-fiber dual-comb source is seeded by a dual-wavelength mode-locked fiber laser operating at fundamental repetition rates of about 1.0 GHz differing by 148 kHz,which has an excellent stability in the free-running state that the Allan deviation is only 101.7 mHz for an average time of 1 *** to the large repetition rate difference between the asynchronous dichromatic pulse trains,the GHz DCS enables a refresh time as short as 6.75 μs,making it promising for studying nonrepeatable transient phenomena in real *** this end,the practicality of the present GHz DCS is validated by successfully capturing the'shock waves'of balloon and firecracker explosions *** GHz single-cavity all-fiber dual-comb system promises a noteworthy improvement in acquisition speed and reliability without sacrificing measurement accuracy,anticipated as a practical tool for high-speed applications.

关键词： laser all-fiber dual-comb high-speed practical single-cavity spectroscopy

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Nonequilibrium kinetics effects in Richtmyer–Meshkov instability and reshock processes

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Communications in Theoretical physics 2023年第11期75卷 99-114页

作者： Yiming Shan Aiguo Xu Lifeng Wang Yudong Zhang National Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsChina Academy of Engineering PhysicsMianyang 621900China Center for Applied Physics and Technology MOE Key Center for High Energy Density Physics SimulationsCollege of EngineeringPeking UniversityBeijing 100871China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou 450001China

Kinetic effects in the inertial confinement fusion ignition process are far from *** this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann *** work begins by interpreting the experiment conducted by Collins and Jacobs(2002,*** Mech.464,113-136).It shows that the shock wave causes substances in close proximity to the substance interface to deviate more significantly from their thermodynamic equilibrium *** thermodynamic non-equilibrium(TNE)quantities exhibit complex but inspiring kinetic effects in the shock process and behind the shock *** kinetic effects are detected by two sets of TNE *** first set includes∣Δ_(2)^(*)∣,∣Δ_(3,1)^(*),∣Δ_(3)^(*)∣,and∣Δ_(4,2)^(*)∣,which correspond to the intensities of the non-organized momentum Flux(NOMF),Non-Organized Energy Flux(NOEF),the flux of NOMF and the flux of *** four TNE measures abruptly increase in the shock *** second set of TNE quantities includes■_(NOMF),■_(NOEF)and■_(sum),which denote the entropy production rates due to NOMF,NOEF and their summation,*** mixing zone is the primary contributor to■_(NOEF),while the flow field region outside of the mixing zone is the primary contributor to■_(NOMF).Additionally,each substance exhibits different behaviors in terms of entropy production rate,and the lighter fluid has a higher entropy production rate than the heavier fluid.

关键词： Richtmyer-Meshkov instability discrete Boltzmann method nonequilibrium kinetics effects

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A Novel FDTD-PIC Scheme for Accurate Transient Analysis of Terahertz Gyrotrons

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IEEE Transactions on Terahertz Science and technology 2025年第3期15卷 496-504页

作者： Tang, Runfeng Chen, Xianfei Xie, Liangqian Liu, Weijian He, Chenxi Han, Xiaotao Savilov, Andrei V. Yu Glyavin, Mikhail Xiao, Houxiu Huazhong University of Science and Technology Wuhan National High Magnetic Field Center School of Electrical and Electronic Engineering Wuhan China Russian Academy of Sciences Federal Research Center Institute of Applied Physics Nizhny Novgorod603950 Russia Lobachevsky State University of Nizhny Novgorod Advanced School of General and Applied Physics Nizhny Novgorod603950 Russia

As the resonant frequencies advance into the terahertz regime, the mode competition in the gyrotron becomes increasingly intense, exhibiting atypical and varied transient processes. Consequently, rigorous time-domain simulation is crucial for developing terahertz gyrotrons. Traditional dedicated codes typically utilize the gyro-averaged method to address fast time-scale behaviors. However, this approach may lead to misinterpretation when analyzing transient processes involving modes with different response properties and multi-scale behaviors, such as harmonic and gyro-BWO operations. To address this challenge, this paper directly analyzes the dynamic behavior of various modes based on fast-varying field variables without any time-scale assumption, ensuring a precise depiction of beam-wave interactions. The proposed numerical framework integrates a scalar 1D Finite Difference Time Domain (FDTD) method with a 3D Particle-In-Cell (PIC) algorithm, providing a comprehensive description of full-wave physics. The simplified 1D FDTD model, along with the pre-selection of relevant modes, significantly reduces data storage requirements. A thorough validation of the proposed numerical framework demonstrates that the results align well with those obtained from established dedicated codes, showcasing superior accuracy in transient analysis. © 2011-2012 IEEE.

关键词： Transient analysis

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