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25 September 1999, Volume 16 Issue 5 Previous Issue    Next Issue

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The natural integral equation of 3-d exterior helmholtz problem and its numerical solution Wu Jiming, Yu Dehao 1999, 16(5): 449-456.  Abstract ( )   PDF (291KB) ( )   The natural boundary reduction,suggested by Feng and Yu[2,3],is applied to deal with the exterior boundary value problem of 3-D Helmholtz equation.First,it explains how to derive the natural integral equation,namely the exact Dirichlet-to-Neumann condition,of Helmholtz problem in exterior spherical domain by expansion of spherical harmonics.Second,a numerical method for solving the hypersingular integral equation is developed.Third,some numerical examples are given to illustrate this method.

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The finite element method for hyperbolic conservation laws Yu Xijun, Fu Hongyuan, Chang Qianshun 1999, 16(5): 457-466.  Abstract ( )   PDF (386KB) ( )   A scheme is outlined for solving hyperbolic conservation laws by finite element method of piecewise linear interpolations. It is different from the discontinuous finite element on the boundaries of neighboring cells to solve Riemann problems that the scheme is designed to solve hyperbolic conservation laws based on the Hamilton Jacobi equations. Under the CFL condition, the scheme is proved that it satisfies the maximal principle and is a TVD scheme. Numerical examples are given and discussed.

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Monte carlo simulation of the process of single event upset induced by neutrons Li Hua 1999, 16(5): 467-473.  Abstract ( )   PDF (312KB) ( )   Based on physical mechanism of the interaction between incident neutrons and silicon atoms, a simulation program of Single Event Upset (SEU) induced by neutrons is compiled by Monte Carlo method. The process of SEU of a 16 K static access memory silicon chip induced by 14 MeV incident neutrons has been simulated by the program. The simulation results show that the program can provide a detailed description of the physical process of SEU of a silicon chip and can produce reference data about SEU cross section in a 14 MeV neutrons evironment.

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Crosshole resistivity tomography and the application Dong Qinghua, Zhu Jieshou 1999, 16(5): 474-480.  Abstract ( )   PDF (384KB) ( )   According to the fundamental equation of steady current field, the corresponding functional equation is obtained by use of the linear differential operator. Since inversion image algorithm is very important in crosshole resistivity tomography, a improved Occam's inversion is presented. Image results of the theoretical model data and the field measured data are given and discussed.

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A numerical algorithm of first-order for systems driven by correlated noises Fu Haixiang, Cao Li, Wu Dajin 1999, 16(5): 481-488.  Abstract ( )   PDF (275KB) ( )   A first-order algorithm of numerical solution is developed for systems simultaneously driven by correlated additive noise and multiplicative noise,both in the case that the multi-plicative noise is of white and of colored noise.As an example,the steady state probability distribution of bistable model is computed.Results verifies that this algorithm is applicable.

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Behavior analysis of upwind compact difference schemes for the fully discretized convection equation Wang Qiang, Fu Dexun, Ma Yanwen 1999, 16(5): 489-495.  Abstract ( )   PDF (274KB) ( )   Based on the Fourier analysis method, a fully-discretized dispersion relation is derived for a family of high accuracy upwind compact difference schemes by considering one dimensional linear convetion equation temporally discretized by the explicit multi-step Runge-Kutta algorithm. The effects of CFL numbers on the characteristics of these schemes, including dissipation and dispersion errors, phase velocity and group velocity, are analyzed. The two-dimensional anisotropy problem is discussed. Moreover, an eigenvalue analysis is performed. Two numerical examples are used to show the high accuracy and resolution of these schemes.

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Parallel computing and performance analysis for 2-dimensional plasma simulations with particle clouds in cells methods Mo Zeyao, Xu Linbao, Zhang Baolin, Shen Longjun 1999, 16(5): 496-504.  Abstract ( )   PDF (532KB) ( )   It provides an overview of the parallel computing for 2-dimensional plasma simulations with particle clouds in cells methods under both shared-memory and distrbuted-memory parallel computing environments.The parallel algorithm and its implementation are desigened on the basis of the serial algorithm and the executing characteristics of the serial code.The practical parallel computations are performed under Challenge,DAWN 1000+, Power PC Cluster and XMZY. Many important conclusions are given and quite useful for the parallel computations of both types of particle simulation methods and other applicational codes.

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A new method for analyzing spectral emissivities of semi-transparent medium layers--pseudo source adding method Huang Yong, Xia Xinlin, Tan Heping, Yu Qizheng 1999, 16(5): 505-510.  Abstract ( )   PDF (233KB) ( )   According to the internal thermal emission of the medium,a new method,pseudo source adding method,is presented to analyze the apparent emissivities of semi-transparent medium layers.By this method,the apparent emissivity formulae are derived for two different cases,in one of which,the semi-transparent emitting surface is considered to be specularly reflecting,and the diffuse reflection is considered in the other.The substrate surface of the layer is supposed to be diffuse and opaque for the two cases.The comparison with the results by the Monte Carlo method is also given.

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Spatiotemporal chaos synchronization by active-occasional coupling Wang Jinlan, Chen Guangzhi 1999, 16(5): 511-516.  Abstract ( )   PDF (220KB) ( )   The occasional coupling synchronization scheme of the active-passive decomposition (active-occasional coupling) is proposed,which consists of both synchronization and autonomous phases.In the former,the synchronization scheme is used to synchronize the drive and the response system;in the latter,small errors will lead to the separation and desynchronization of the two systems. If the synchronization phases are sufficient enough,the full synchronization will occur.The synchronization condition is discussed in theory,and the relation between the synchronization phases and the coupling strength is also investigated numerically.

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Convolution method for parallel beams to reconstruct temperature distribution Wang Humin, Liu Kexue 1999, 16(5): 517-523.  Abstract ( )   PDF (357KB) ( )   ESPI (Electronic Speckle Pattern Interferometry) is a new technique that can be used to measure the density field or the temperature field of a transparent fluid. One essential part of this technique is to reconstruct a 3D image of the physical field by use of the projections of the field to different directions and/or different sections. This work introduces the primary principle of 2D reconstruction and then focuses on convolution method for parallel beams. On this foundation, it simulates the projections for double Gauss distribution function and reconstructs the simulating temperature field by the convolution method for parallel beam. In order to instruct ESPI experiment, it also simulates three different errors and gets the sensitivity of them. According to the limited direction character of ESPI, the double linear interpolation method is used and gets a better reconstruction result.

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The coupling calculation of two dimension strip shape antenna in cavity Zhu Xueguang, Kuang Guangli, Zhao Yanping, Li Youyi, Xie Jikang 1999, 16(5): 524-528.  Abstract ( )   PDF (196KB) ( )   When the ion cyclotron resonance heating is adopted in Tokamak, in order to protect the antenna in a better way, the antenna is usually placed in the cavity.The boundary condition in cavity is more complex, so the coupling calculation is comparatively more difficult. The two dimension strip shape antenna in cavity is calculated. The variation of coupling impedance of such antenna with its sizes has been investigated.

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Similarity model of hydrodynamics of slab target X-ray lasers Li Yingjun, Zhang Guoping, Zhang Jie, Peng Hansheng 1999, 16(5): 529-535.  Abstract ( )   PDF (259KB) ( )   A similarity model describing the physics of slab target X-ray lasers is constituted from the ideal hydrodynamic equations. The parameters of the plasma(e.g., temperature, density, and scale length) are predicted, which are important for the experimental design of slab target X-ray lasers. The model provides a mathematic tool for quantitatively predicting and explaining experimental results.

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Theoretical study on α-rf discharges in planar CO2 lasers Wu Guiling, Wang Youqing, Qiu Junlin, Wang Xinbing 1999, 16(5): 536-542.  Abstract ( )   PDF (277KB) ( )   A theoretical model to describe the discharges in the RF excited planar CO2 lasers is established.The spatial distributions of electron density,electric field,power density and the excitation efficiency for the upper laser level are obtained by numerical method.The discharge striations in RF excited lasers observed by experiments are explained.The relations between parameters and characters of the discharge are analyzed.

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Irradiation uniformity for laser driven fusion and computational study of kinoform phase plates Zhang Jiatai, Yang Guolin 1999, 16(5): 543-551.  Abstract ( )   PDF (364KB) ( )   The principle and technique of irradiation uniformity for laser driven fusion are analysed.Kinoform phase plates (KPP) is studied by using theoretical analyse and numerical calculation.The results show that the converged far-field pattern containe more than 96% of the incident energy inside a desired region and the minimum nonuniformity is about 14%.Reviews on irradiation uniformity of the laser driven fusion device are covered.

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Unstructured grid generation for three dimensional complex geomtries and self-adaption technique Zhang Laiping, Yang Yongjian, Guo Chao, Zhang Hanxin, Gao Shuchun 1999, 16(5): 552-558.  Abstract ( )   PDF (483KB) ( )   A technique on generation of unstructured grids for three dimensional complex geomtries is presented.Complex configurations are described by several typical kinds of surface patches.A 3D surface patch is first mapped to a 2D segment,then triangulated using a 2D grid generator based on the advancing front method,and finally mapped back to the original 3D shape.Tetrahedral grids are generated by an advancing front method and smoothed by a nodal relaxation technique and a Deluanay transformation.A mesh refinement technique is also given to obtain more accurate solutions.

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A mistake in "notes on transpiration control equations" Fei Jinggao 1999, 16(5): 559-560.  Abstract ( )   PDF (82KB) ( )   A mistake in paper "Notes on Transpiration Control Equations" is pointed out,and the reason why the mistake was made is also given.