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25 June 1993, Volume 10 Issue 2 Previous Issue    Next Issue

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A GENERALIZED DIFFERENCE APPROXIMATION OFSTOKES EQUATIONS USING NONCONFORMING ELEMENTS Wang Shenlin 1993, 10(2): 129-136.  Abstract ( )   PDF (421KB) ( )   A nonconforming generlized difference approximation for solving Stokes equations, in 2-dimension is proposed with triangular element mesh method. The subspace of velocity field is formed by piecewise-linear functions, the subspace of pressure and those of test functions are formed by precewise constant functions.Error estimates for this approximation in both velocity and pressure are also given wtih showing optimal approximate order.

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A CLASS OF ESSENTIALLY NON-OSCILLATORY SCHEMES FOR HYPERBOLIC CONSERVATION LAWS Xu Shurong, Li Wensheng 1993, 10(2): 137-145.  Abstract ( )   PDF (462KB) ( )   In this paper, some methods to construct the numerical flux in ENO Essentially Non-Oscillatory schemes for conservative difference equations, which are based on the idea of adaptive stencil and reconstruction, are presented. Some numerical results are also given.

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DESIGN OF FOCUS DEFLECTION SYSTEM FORELECTROSTATIC DEFLECTION TYPE CAMERA TUBES 1ELECTROSTATIC FIELD CALCULATION Yang Guowei, Guan Yonggui 1993, 10(2): 146-154.  Abstract ( )   PDF (504KB) ( )   An electrostatic deflection-type camera tube has the following advantages: The small electron beam spots over the entire the scanned area provide uniform and high resolution picture, normal beam landing performance and deflection linearity are also excellent. The purpose of the paper is to .give the field calculation for focus deflection system of a camera tube with electrostatic deflection yokes.

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TWO-DIMENSIONAL MESH GENERATION TECHNIQUESAND APPLICATION Li Fengwei, E Qin 1993, 10(2): 155-162.  Abstract ( )   PDF (584KB) ( )   This paper utilizes a series of analytical transformations to generate two-dimensional curvefitted, orthogonal meshes. The generated meshes can be regulated and controlled according to the variation of the flow parameters in the flow field so as to obtain the optimal grid distribution. As an example, taking unsteady transonic flows over oscillating NACA 0012 airfoil, the effects of transformation accuracy on computation accuracy of flow field, and how to control the grid generation corresponding with the variation of the flow parameters are analyzed in detail.The proceeding techniques have been applied to solve Euler equations with succes and the numerical results are satisfactory.

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THE IMPACT OF SDI ON THE ARMS RACE——A SOLUTION OF GAME THEORY Li Bin, Du Xiangwan 1993, 10(2): 163-169.  Abstract ( )   PDF (383KB) ( )   The impact of SDT on arms race has been discussed in a model which includes intercontinental ballistic missiles, anti-FCBM satellites and anti-satellite weapons for U.S. and former Soviet Union. It is assumed that each side of U. S. and former Soviet Union wants to reach the biggest retaliatory capability for given expenditure. This problem is considered as a two-person game and the optimal configurations of the three kinds of weapons for both sides is calculated under different conditions. The results show that the SDI can not lead to the transition from an offensive mode to a defensive mode and can not also offer an effective protection against the threat of ICBMs.

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A NEW NUMERICAL METHOD FOR DUAL-MODEOPTICAL FIBRES WITH ZERO INTERMODAL DISPERSION Xia Yousheng 1993, 10(2): 170-174.  Abstract ( )   PDF (275KB) ( )   A new numerical method for finding the optimum retractive-index profile of Dual-mode optical fibres with zero intermodal dispersion is presented, Using Newton iteration we obtain the solutions of the above inverse problem.

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GENERAL CALCULATION FORTHE PROPAGATION DIRECTION OF POLARIZED LIGHT AT THE INNER AND EXTERNAL OF BIAXIAL CRYSTAL Yuan Lin 1993, 10(2): 175-184.  Abstract ( )   PDF (613KB) ( )   General formulae for propagating directions of the polarized light at the inner and external of biaxial crystal are obtained in the case that ray along arbitrary direction is incident upon a crystal of arbitrary making direction. The transition from it to uniaxial crystal, refractive rays lying in the incident plane and cone refraction are discussed. At last, the corresponding numerical results are plotted in curvilineal diagrams for Iceland spar and crystal sulphur, they make the directions of the refractrive rays clear as the crystal rotates. These results provide an important basis for study of new crystal optical components and new measuring methods of crystal optical constants.

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SOLUTION OF UNSTEADY BOUNDARY LAYEREQUATIONS USING DIFFERENTIALQUADRATURE METHOD Tang Dengbin, Qian Lin, Shu Chang 1993, 10(2): 185-190.  Abstract ( )   PDF (365KB) ( )   The key technique to differential quadrature method, i. e. the determination of the weighting coefficients, is investigated in this paper. The method of computing different weighting coefficients is developed on the basis of Lagrangian interpolating approximation. This method overcomes the limitation of rigorous restriction in choice of the coordinates of grid points in original method1, and proves favoradble for studies of fluid mechanics problems. Resultes obtained for solving unsteady boundary layers show that the differential quadrature method can achieve rather high accurate solution by using only a few grid points.

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NUMERICAL APPROXIMATION TO THE N-TH DERIVATIVES Jiang Yong, Dai Yu 1993, 10(2): 191-196.  Abstract ( )   PDF (283KB) ( )   Continuing the work of [1], this paper considers mainly the approximation to the n-th derivatives of functions, and develops an effective algorithm with its convergance and error astimate by the method of numerical integration. As an application, the algorithm is used to evaluate the integration of highly oscillatory functions and proves efficient.

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A PERTURBATIONAL FINITE DIFFERENCE SCHEME OFEXPONENTIAL TYPE FOR THE CONVECTION-DIFFUSION EQUATION Chen Guoqian, Yang Zhifeng 1993, 10(2): 197-207.  Abstract ( )   PDF (649KB) ( )   The perturbational fourth-order finite difference scheme of exponential type proposed by the authors is improved, by replacing the exponential coefficients in the source term perturbation with rational expressions, and is applied, aimed at the basic difficulties in computational fluid mechanics, to one-to three-dimensional model equations and a problem of natural convection with large Rayleigh-numbers, turning out the outstanding advantages of the perturbational scheme in such aspects as adaptability to flows with large Reynolds-numbers, resolution to ‘shock wave’-and ‘viscous boundary layer’-like effects, and saving computing CPU time.

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COMPUTER SIMULATION OF RADIATION DAMAGE INDUCED BY α-PARTICLES Pan Zhengying, Shao Qiyun, Zhu Baixiang 1993, 10(2): 208-214.  Abstract ( )   PDF (503KB) ( )   The energy deposition, production of displacement and replacement collisions induced by fusion α-particles with energies from 10keV to 50keV are studied by computer code MARLOWE based upon binary-collision approximation. The results are compared with the Monte-Carlo simulation. The number of vacancies is found to be proportional to the elastic energy, deposition, in agreement with analytical theory. The similar profiles are observed for both elastic energy deposition and vacancies. The radiation damages caused by α-particles in different target elements are discussed as well.

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A MONTE CARLO SIMULATION OF IONS STRIKING THE CATHODE IN A ARGON GLOW DISCHARGE Wang Dezhen, Gong Ye, Ma Tangcai 1993, 10(2): 215-219.  Abstract ( )   PDF (314KB) ( )   A Monte Carlo simulation method that includes charge exchange and elastic scattering is used to calculate the energy and angular distribution of ions striking the cathode in a DC argon glow discharge. For the case that charge exchange is the only collision process, the Monte Carlo results can be checked by the analytical solution of the Boltzmann equation. In that case, both methods yield the same ion impact energy distribution. The results of the simulation show that the most of ions almost vertically incident on the cathode.

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CALCULATIONS ON NONLINEAR DIELECTRIC SLABWAVEGUIDES BY THE ITERATIVE EIGENFUNCTIONEXPANSION METHOD Gong Yuejin 1993, 10(2): 220-226.  Abstract ( )   PDF (388KB) ( )   A new treatment for the behaviour of both TE and TM non-linear waves in an arbitrary nonlinear material is given. The treatment is based on a recently developed method-the Iterative Eigen. function expansion method (IEEM). Compared with the results of Finite-element method (FEM), this scheme has proven very successful.It is also easily generalized to other nonlinear behaviour studies for varying geometries.

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CALCULATION ON DEEP IMPURITY LEVELS OF TRANSITION METALS IN GaAs Hua Wenyu, Chen Cunli 1993, 10(2): 227-231.  Abstract ( )   PDF (326KB) ( )   A cluster model consisting of 41 atoms is presented for simulating the bulk crystal and some quasi atoms are added in order to saturate dangling bonds in the cluster boundary. The SCCC-EHMO method is used to calculate the deep impurity states of neutral transition metal atoms Cr, Mn, Fe, Co and Ni in gallium arsenide. It is found that the calculated positions of the deep impurity levels in the gap are in good agreement with the experimental results.

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A HIGH RESOLUTION ARTIFICIAL VISCOSITY METHOD Jin Baoxia 1993, 10(2): 232-238.  Abstract ( )   PDF (356KB) ( )   In this paper, a high resolution finite difference scheme based on artificial viscosity is introduced. The scheme can obtain almost as good results as total variation diminishing schemes can obtain, but the time consuming of the scheme is much less than that of total variation diminishing schemes.

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PARTIAL WAVE METHOD FOR CALCULATING ELASTICSCATTERING CROSS SECTION OF LOW ENERGY ELECTRONBY SOLVING RELATIVISTIC DIRAC EQUATION Tan Zhenyu, He Yancai 1993, 10(2): 239-245.  Abstract ( )   PDF (393KB) ( )   In this paper, a method for calculating elastic scattering cross section of low energy electron based on solving relativistic Dirac equation is given, the cross sections calculated by applying Thomas-Fermi-Dirac (TFD) potential and Hartree-Fock (HF)potential respectively are compared, the cross sections of elements C, Al, Cu, Ag, Au are calculated, the differences between Mott model. Pendry model and Rutherford formula are also compared and analysed.

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COULOMB EFFECT IN π±-40CaCa ELASTIC SCATTERING Guo Bingying, Zheng Yanxiang, Chen Kezhong 1993, 10(2): 246-250.  Abstract ( )   PDF (271KB) ( )   Within the framework of Eikonal multiple-scattering theory, the Coulomb effect in π±-40Ca elastic scattering is studied. The calculating program for the differential cross section is worked out by FORTRAN 77 and the results are in good keeping with the experimental data, indicating that the Coulomb effect does not only enhance the small angle differential cross section, but also fill up the dips of differential cross section.

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THE COLLOCATION SOLUTION TO THE PROBLEM OF LIQUID SLOSHING IN AXISYMMETRIC TANKS Zhou Ding 1993, 10(2): 251-256.  Abstract ( )   PDF (348KB) ( )   This paper studies the sloshing characteristics of liquid in axisymmetric tanks along the vertical axis at gravity environment. First, the wave equation describing the potential velocity of liquid is established in cylindribal co-ordinates and the analytical solution of linearizing potential velocity of liquid is deduced by means of the separated variable method. Then, the unknown integral coefficients of the solution are determined by collocation method on boundary and the frequency equation is obtained. The frequency para-meters can be numerically given by means of computer. The method has the property of good generality, less calculating amount and higher accuracy compared with other methods. Finally, as examples, numerical results of spherical and ellipticl tanks are given.