检索结果-南通市图书馆

High order moment closure for Vlasov-Maxwell equations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Mathematics in China 2015年第5期10卷 1087-1100页

作者： Yana DI Zhenzhong KOU Ruo LI The State Key Laboratory of Scientific and Engineering Computing Chinese Academy of Sciences Beijing 100190 China National Center for Mathematics and Interdisciplinary Sciences Chinese Academy of Sciences Beijing 100190 China Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190 China hedps & capt LMAM & School of Mathematical Sciences Peking University Beijing 100871 China

The extended magnetohydrodynamic models are derived based on the moment closure of the Vlasov-Maxwell （VM） equations. We adopt the Grad type moment expansion which was firstly proposed for the Boltzmann equation. A new regularization method for the Grad＇s moment system was recently proposed to achieve the globally hyperbolicity so that the local well-posedness of the moment system is attained. For the VM equations, the moment expansion of the convection term is exactly the same as that in the Boltzmann equation, thus the new developed regularization applies. The moment expansion of the electromagnetic force term in the VM equations turns out to be a linear source term, which can preserve the conservative properties of the distribution function in the VM equations perfectly.

关键词： Moment closure Vlasov-Maxwell (VM) equations Boltzmannequation extended magnetohydrodynamics

Recent progress of laser driven particle acceleration at Peking University

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of physics 2013年第5期8卷 577-584页

作者： Xue-Qing Yan Chen Lin Hai-Yang Lu Kun Zhu Yu-Bin Zou Hong-Yong Wang Bing Liu Shuan Zhao Jiao Zhu Yi-Xing Geng, He-Zheng Fu Yong Shang Chao Cao Yin-Ren Shou Wei Song Yuan-Rong Lu Zhong-Xi Yuan Zhi-Yu Guo Xian-Tu He Jia-Er Chen State Key Laboratory of Nuclear Physics and Technology and capt Peking University Beijing 100871 China

Recently, radiation pressure acceleration （RPA） has been proposed and extensively studied, which shows that circularly polarized （CP） laser pulses can accelerate mono-energetic ion bunches in a phase-stable-acceleration （PSA） way from ultrathin foils. It is found that self-orgizing proton beam can be stably accelerated to GeV in the interaction of a CP laser with a planar target at 1022 W/cm2. A project called Compact LAser Plasma proton Accelerator （CLAPA） is approved by MOST in China recently. A prototype of laser driven proton accelerator （1 to 15 MeV/1 Hz） based on the PSA mechanism and plasma lens is going to be built at Peking University in the next five years. It will be upgraded to 200 MeV later for applications such as cancer therapy, plasma imaging and fast ignitiou for inertial confine fusion.

关键词： phase-stable acceleration (PSA) laser ion acceleration ignition

Droplet impact on wetted structured surfaces

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2022年第3期43卷 437-446页

作者： M.MOHASAN A.B.AQEEL Huiling DUAN Pengyu LYU Yantao YANG Department of Mechanics and Engineering Science State Key Laboratory for Turbulence and Complex Systems(SKLTCS)Beijing Innovation Center for Engineering Science and Advanced Technology(BIC-ESAT)College of EngineeringPeking UniversityBeijing 100871China Department of Mechatronics Engineering National University of Sciences and TechnologyIslamabad 44000Pakistan Center for Applied Physics and Technology(capt) HEDPS and IFSA Collaborative Innovation Center of MoEPeking UniversityBeijing 100871China

In this study,we numerically investigate the droplet impact onto a thin liquid film deposited on a structured surface with square pillars and *** time evolution of crown geometry is strongly affected by the surface *** the thickness of the liquid film is larger than the structure height,the expanding speed of the crown base radius is independent of the structure ***,if the liquid film thickness is equal to the structure height,the crown base expands slower as the structure width *** structures have strong effects on the crown height and radius,and can prevent ejected filament from breaking into satellite droplets for certain *** the liquid film with the thickness equal to the pillar height,both the crown height and the radius exhibit non-monotonic behaviors as the pillar width *** exists one pillar width which produces the smallest crown height and the largest crown radius.

关键词： droplet impact structured surface liquid film crown formation

Change in Continuous Detonation Wave Propagation Mode from Rotating Detonation to Standing Detonation

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2010年第3期27卷 216-219页

作者：邵业涛王健平 State Key Laboratory of Turbulence and Complex System CAPT Department of Mechanics and Aerospace Engineering College of Engineering Peking University Beijing 100871

We perform a three-dimensional numerical simulation based on a one-step chemical reaction model to investigate changes in the mode of H2-Air detonation wave propagation from rotating detonation wave （RDW） mode to standing detonation wave mode. The physical characteristics of an RDW with injection velocity of 500 m/s are analyzed to investigate the physical mechanisms involved. We find that with increasing injection velocity, the detonation wave gradually changes from perpendicular to the head wall to parallel to the head wall. When the injection velocity exceeds the Chapman-Jouguet velocity VCJ （about 1984 m/s）, the detonation wave changes orientation to become perpendicular to the fuel injection direction, and the rotating mode changes accordingly to a standing mode. Finally, the plane detonation characteristic triple-wave structures can be found from the standing mode.

关键词： Fluid dynamics Chemical physics and physical chemistry

Identification, characterization and evolution of non-local quasi-Lagrangian structures in turbulence

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2016年第3期32卷 351-361页

作者： Yue Yang State Key Laboratory for Turbulence and Complex Systems(LTCS) and Center for Applied Physics and Technology(capt) College of Engineering Peking University

The recent progress on non-local Lagrangian and quasi-Lagrangian structures in turbulence is *** quasi-Lagrangian structures, e.g., vortex surfaces in viscous flow, gas-liquid interfaces in multi-phase flow, and flame fronts in premixed combustion, can show essential Lagrangian following properties, but they are able to have topological changes in the temporal evolution. In addition,they can represent or influence the turbulent flow field. The challenges for the investigation of the non-local structures include their identification, characterization, and *** improving understanding of the quasi-Lagrangian structures is expected to be helpful to elucidate crucial dynamics and develop structure-based predictive models in turbulence.

关键词： Turbulence Lagrangian study Coherent structure Multi-scale analysis Vortex dynamics

Matching boundary conditions for lattice dynamics

在线全文

学校读者我要写书评

暂无评论

Matching boundary conditions for lattice dynamics

Intelligent Shape-Morphing Micromachines

23rd International Congress of Theoretical and Applied Mechanics

作者： Xianming Wang Shaoqiang Tang Center for Combustion Energy and Department of Thermal EngineeringTsinghua University hedps CAPTand LTCSCollege of EngineeringPeking University

＜正＞We develop a new class of accurate and efficient absorbing boundary conditions,named as matching boundary conditions（MBC’s）, which are used to suppress spurious reflections at artificial boundaries for molecu...

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Research 2021年第1期2021卷 1018-1033页

作者： Qianying Chen Pengyu Lv Jianyong Huang Tian-Yun Huang Huiling Duan State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering ScienceBIC-ESATCollege of EngineeringPeking UniversityBeijing 100871China capt HEDPSPeking UniversityBeijing 100871China

Intelligent machines are capable of switching shape configurations to adapt to changes in dynamic environments and thus have offered the potentials in many applications such as precision medicine,lab on a chip,and *** though the developments of smart materials and advanced micro/nanomanufacturing are flouring,how to achieve intelligent shapemorphing machines at micro/nanoscales is still significantly challenging due to the lack of design methods and strategies especially for small-scale shape *** review is aimed at summarizing the principles and methods for the construction of intelligent shape-morphing micromachines by introducing the dimensions,modes,realization methods,and applications of shape-morphing ***,this review highlights the advantages and challenges in shape transformations by comparing micromachines with the macroscale counterparts and presents the future outlines for the next generation of intelligent shape-morphing micromachines.

关键词： machines realization dimensions

Linear Scaling Discontinuous Galerkin Density Matrix Minimization Method with Local Orbital Enriched Finite Element Basis:1-D Lattice Model System

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational Physics 2013年第7期14卷 276-300页

作者： Tiao Lu Wei Cai Jianguo Xin Yinglong Guo hedps&capt LMAM&School of Mathematical SciencesPeking UniversityBeijing 100871P.R.China INS Shanghai Jiaotong UniversityShanghai 200240P.R.China Department of Mathematics and Statistics University of North Carolina at CharlotteCharlotteNC 28223-0001USA School of Mathematical Sciences Peking UniversityBeijing 100871P.R.China

In the first of a series of papers,wewill study a discontinuous Galerkin(DG)framework for many electron quantum *** salient feature of this framework is the flexibility of using hybrid physics-based local orbitals and accuracy-guaranteed piecewise polynomial basis in representing the Hamiltonian of the many body *** a flexibility is made possible by using the discontinuous Galerkin method to approximate the Hamiltonian matrix elements with proper constructions of numerical DG fluxes at the finite element *** this paper,we will apply the DG method to the density matrix minimization formulation,a popular approach in the density functional theory of many body Schrodinger *** density matrix minimization is to find the minima of the total energy,expressed as a functional of the density matrixρ(r,r′),approximated by the proposed enriched basis,together with two constraints of idempotency and electric *** idempotency will be handled with theMcWeeny’s purification while the neutrality is enforced by imposing the number of electrons with a penalty method.A conjugate gradient method(a Polak-Ribiere variant)is used to solve the minimization ***,the linear-scaling algorithm and the advantage of using the local orbital enriched finite element basis in the DG approximations are verified by studying examples of one dimensional lattice model systems.

关键词： Density functional theory density matrix minimization discontinuous Galerkin method linear scaling method

Preliminary design of a laser accelerator beam line

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics C 2014年第11期38卷 107-110页

作者：尚勇朱昆曹超朱军高陈元荣郭之虞陈佳洱颜学庆 State Key Laboratory of Nuclear Physics and Technology & Key Lab of High Energy Density Physics Simulation CAPT Peking University

A compact laser plasma accelerator （CLAPA） an RPA-PSA mechanism or other acceleration mechanisms is being built at Peking University, which is based on The beam produced by this laser accelerator has the characteristics of short duration, high pulse current, large divergence angle, and wide energy spectrum. The beam cannot be produced by a normal ion source and accelerator. The space charge field in the initial is very strong. According to the beam parameters from preparatory experiments and theoretical simulations, a compact beam line is preliminarily designed. The beam line mainly consists of common transport elements to deliver proton beam with the energy of 1 50 MeV, energy spread of 0-±1% and current of 0-10^8 proton per pulse to satisfy the requirement of different experiments. The simulation result of a 15 MeV proton beam with an energy spread of ±1%, current of 400 mA, and final spot radius of 9 mm is presented in this paper.

关键词： laser plasma accelerator beam line common transport elements