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25 March 1998, Volume 15 Issue 2 Previous Issue    Next Issue

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ON SEMI-RANDOM SIMULATION METHODS FOR CALCULATING PARTICLE TRANSPORT PROBLEMS Feng Tinggui 1998, 15(2): 129-133.  Abstract ( )   PDF (188KB) ( )   After analyzing the advantages and disadvantages of Monte Carlo and deterministic methods for solving particle transport problems, a zero variance iteration scheme and a semi-random simulation method are presented, which exploits the strengths and discards the weak of both methods. Both the scheme and the method are described briefly.

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NUMERICAL STUDY IN TWO-DIMENSIONAL GRAVITY MODEL WITH BOSONIC STRING COUPLING Peng Dianyun, Yan Jun, Qiu Xiaoming 1998, 15(2): 134-138.  Abstract ( )   PDF (195KB) ( )   The equation of motion is given for an integrable model of two dimensional gravity with bosonic string coupling in Riemann-Cartan space.Numerical solutions are obtained by means of numerical integraiton method and their motion curves are also shown.

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TWO-DIMENSIONAL RELATIVISTIC ELECTROMAGNETIC PARTICLE SIMULATION OF LASER-PLASMA Zhang Jiatai, Xu Linbao, Chang Tieqiang, Zhang Shugui, He Bin, Zhu Senchang, Zheng Chunyang, Jin Hui, He Xiantu 1998, 15(2): 139-146.  Abstract ( )   PDF (289KB) ( )   A two-dimensional relativistic electromagnetic particle simulation code (2DCIC) is presented. The charge and current densities are computed self-consistently using Maxwell's equations, relativistic motion equations of electrons and Newton's equations of ions by tracking 104-106 simulated particles. some details of wave wave and wave particle interaction are also studied together with the evolution of instability as time. Laser light impinges obliquely (or normally) on plasma, which has a density gradient (or homogeneous density). To save computational time, the parallel computational method is developed. Using this code, the ultrashort intense pulse laser plasma interaction and other plasma problems can be also studied by modifying parameters of physical model. After a lot of test computation, plasma equilibrium and propagation of ultrashort intense pulse laser in plasma are studied. The computed physical picture is reasonable.

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IMPROVEMENT OF THE METHOD TO SOLVE LEAKY MODES IN ACOUSTIC LOGGING AND NUMERICAL EXAMPLE Ma Jun, Wang Kexie 1998, 15(2): 147-153.  Abstract ( )   PDF (234KB) ( )   Investigation for improving the method to solve leaky modes in acoustic oil well logging is introduced, and a numerical example of its applications is given.

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SYMPLECTIC SCHEMES FOR TIME-EVOLUTION OF THE QUANTUM SYSTEM IN TIME-DEPENDENT EXTERNAL FIELD Shi Aimin, Wu Chengxun, Zhou Zhongyuan, Ding Peizhu 1998, 15(2): 154-158.  Abstract ( )   PDF (237KB) ( )   2-order norm-preserving and symplectic scheme and 2-order explicit symplectic scheme for separable and linear Hamiltonian system including explicitly time are constituted and applied to compute interaction of the simulated laser field with an electron in the finite width and infinite depth potential well,the results are in good agreement with theoretical analysis.

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SOME CHARACTERS OF THE DOUBLE-FORCED BRUSSELATOR Ying Yangjun, Cheng Shigang, Wang Guangrui 1998, 15(2): 159-164.  Abstract ( )   PDF (258KB) ( )   The influences of the second periodic-forced term on the forced Brusselator are discussed.When the frequency of the two forces are commensurable, the system, which is chaos without the second forcing, can be chaos or periodic. If the two frequency are incommensurable, the system appears one mo re new movement state other than chaos and periodic:that is an strange nonchaotic attractor.

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CALCULATING POTENTIAL DISTRIBUTION OF TWO-DIMENSIONAL CURRENT FIELDS OF FOUR-POINT PROBE TECHNIQUE BY FEM Shi Junshen, Sun Yicai 1998, 15(2): 165-170.  Abstract ( )   PDF (257KB) ( )   The finite element method(FEM) is employed to calculate potential distributions of two-dimensional current fields in semiconductor sheet resistance measurements using a four-point probe and the model of calculation is presented, which has been tested and proved by calculating the potential distribution of several measurement shaped-samples. The FEM has characteristic of simpler and more common for any shape samples than the methods of electrical image and map transformation.

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NUMERICAL SOLUTION OF EULER EQUATIONS FOR THE TRANSONIC FLOW ABOUT REALISTIC AIRCRAFT Li Jie, E Qin, Li Fengwei 1998, 15(2): 171-176.  Abstract ( )   PDF (286KB) ( )   A Fast grid generation procedure named parabolic equation method for complex aircraft is developed. Grid is obtained by marching from body surface to outer boundary. Successful control of grid orthogonality on body is achieved by means of the introduction of algebraic grid prediction. A numerical algorithm based on a finite volume explicit scheme is employed for calculating transonic flow around a realistic aircraft configuration. Comparisons of the computational results with experimental data show very good agreement in terms of trends.

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ANALYSE THE FOCUS OF ELECTRON BEAM FROM PROBABILITY FUNCTION Lei Wei 1998, 15(2): 177-183.  Abstract ( )   PDF (269KB) ( )   Many scientists have already studied the focus of electron beam, and proposed several ways to analyse the electron beam, such as eikonal method, trajectories way, etc. Based on these,the paper uses the probability function to analyse the focus of electron beam, and treats the emission of electron as a random process. The focus has been attained from the probability of coordinates of trajectories.

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A DIFFERENCE SCHEME WITH ANTI-DIFFUSION TERMS WHICH CAN CAPTURE WEAK CONTACT DISCONTINUI TIES AND SHOCKS IN INVISCID FLOW Xu Chunguang 1998, 15(2): 184-192.  Abstract ( )   PDF (364KB) ( )   It is not easy for shock tube experiments to detect very weak contact discontinuities when studying the Mach reflection occurred after a weak shock colliding on a symmetric wedge, also difficult to catch the transition condition between Mach reflection and regular reflection. For this purpose a numerical method for solving Euler's equations in compressible flow is presented, the key is to improve the computation of contact discontinuities using anti diffusion method; equally important is to identify the very weak contact discontinuity and the reflected wave by taking advantage of the behavior of the scheme viscosity and the resulted very small entropy peak. Only doing like this, the analysis of the triple point can be advanced.In,a new type of reflection in irregular reflection with a compression wave without jump was predicated and called "von Neumann wave". We judge and confirm by computational results that the "new" type of reflection must be a simple Mach reflection. Even though very weak, the reflected wave in irregular reflection is still a shock. A systematic calculation about the transition condition will be presented in another paper.

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AN EULER SOLVER BASED ON LATTICE BOLTZMANN GODUNOV METHOD WITH BI-DISTRIBUTION FUNCTIONS Yan Guangwu, Hu Shouxin, Shi Weiping 1998, 15(2): 193-198.  Abstract ( )   PDF (219KB) ( )   A new lattice Boltzmann method is proposed for constructing a 1-D scheme by using bi distribution functions and Godunov scheme of decomposition. The Ideal Case(IC) problem has been hence removed.

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Jump-Adapted Approximation of a Class of Poisson Driven Markov Processes Li Zhenhua, Wu Shengchang, Liu Xiaoqing 1998, 15(2): 199-204.  Abstract ( )   PDF (269KB) ( )   This paper presents a pathwisely jump-adapted approximation of the Poisson driven Markov processes governed by stochastic differential equations.Any trajectory of the processes is divided into continuous phases. Within each phase, the corresponding ODEs are established and solved by the Runge Kutta schemes.The method is applied to investigate the Langevin equation as well as the Duffing-Van der Poloscillator.

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EFFECT OF MIXING TRITIUM ON FUSION BURNING OF D-3He SYSTEM Zeng XianCai, Li Yunsheng 1998, 15(2): 205-210.  Abstract ( )   PDF (224KB) ( )   The processes of ignition and burning in the fusion system of D-3He mixed a small number of tritium have been studied using numerical simulation method. The simulation results show that mixing a small number of ritium into the D-3He system can solve the problem of ignition of D-3He, hence will accelerate its burning and increase its depletion.

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PARALLEL COMPUTATION OF THE FINITE ELEMENT APPROACH IN QUANTUM CHEMISTRY Chen Feiwu, Li Lemin, Chen Zhida 1998, 15(2): 211-217.  Abstract ( )   PDF (251KB) ( )   In the framework of finite element approach, a new calculation scheme is proposed through combining the conventional finite element approach and the basis set expansion method in quantum chemistry. Under the new scheme, total energies in the ground states for diatom molecules Li2, LiH, and BH are calculated on parallel computer DAWN1000. In comparison with the traditional finite element approach,it is found that the more accurate results can been obtained through the new scheme with same computational efforts.

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Numerical Simulation of Flow Between Concentric Rotating Spheres Feng Weibing, Mei Liquan, Li Kaitai 1998, 15(2): 218-225.  Abstract ( )   PDF (314KB) ( )   The Legendre and adjoint Legendre functions are used to study numerically the steady-state and unsteady, axisymmetric incompressible flow between two concentrically rotating spheres.

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AGE METHOD FOR TWO-DIMENSIONAL BURGERS EQUATION AND PARALLEL COMPUTING Lu Jinfu, Zhang Baolin, Xu Tao 1998, 15(2): 226-233.  Abstract ( )   PDF (314KB) ( )   It presents the AGE(Alternating Group Explicit) method for solving the two-dimensional Burgers equation.The method is unconditionally stable by analysis of linearization procedure and has obvious property of parallelism.Numerical example is given at the shared memory computer.

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A QUANTUM MECHANICAL ANALYSIS OF THE TRANSPORT COEFFICIENTS FOR Ar IN N2 GAS Yang Chuanlu, Li Lemin, Chen Zhida 1998, 15(2): 234-238.  Abstract ( )   PDF (187KB) ( )   The diffusion coefficients and interaction viscosities for Ar in N2 are calculated based on physical dynamics theory, by employing quantum mechanical IOSA approximation and Ar-N2 effective interaction potential. The calculation results are in good agreement with the experimental values, and better than those of Gianturco and others. T he calculation interaction viscosity values are very close to experimental ones in the caluculation range.

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DQ-SEMIANALYTICAL METHOD WITH TIME POINTS FOR STRUCTURE DYNAMIC ANALYSIS Peng Jianshe, Zhang Jingyu, Yang Jie 1998, 15(2): 239-243.  Abstract ( )   PDF (176KB) ( )   A method is proposed for controlling partial differential equation directly to beam.It takes differential quadrature method in space domain and series in time domain,and yields equations of determining all parameters for the displacement field by adding time points.The response displacement field can be obtained by solving linear equations.

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AN ALGORITHM FOR IMAGE RECONSTRUCTION OF ELECTRONIC DENSITY REARRANGEMENT FROM COMPTON SCATTERING Luo Ren, Zhang Tingjie 1998, 15(2): 244-250.  Abstract ( )   PDF (364KB) ( )   A computing method for image reconstruction of electronic density rearrangement from the compton scattering data is presented.The well-posedness of the discrete problems is discussed.Some numerical experiments of interest given here show that the method is efficient.

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Calculations of Triple Differential Cross Sections for (e, 2e) Reactions Chen Zhangjin, Shi Qicun, Jia Xiangfu, Chen Ji, Xu Kezun 1998, 15(2): 251-256.  Abstract ( )   PDF (264KB) ( )   A general method to calculate the triple differential cross sections(TDCS) for electron impact ionization of hydrogen atom,hydrogenicion He+, helium atom and helium-like ion Li+is given by generalizing the theoretical framework developed by Brauner et al. The present TDCS results of H, He+, He and Li+are compared with those of other theoretical models and/or experiment, and good agreements have been found.