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25 December 1995, Volume 12 Issue 4 Previous Issue    Next Issue

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A LAGRANGIAN ARBITRARY TRIANGULAR MESH FINITE VOLUME METHOD FOR NUMERICAL SIMULATING 2-DIMENSIONAL HIGH VELOCITY IMPACT PROBLEM Li Yinfan, Liang Zhenxuan, Tan Qingming 1995, 12(4): 433-441.  Abstract ( )   PDF (564KB) ( )   In this paper, a lagrangian arbitrary triangular mesh finite volume method for numerical simulating 2-dimensional high velocity impact problem is described. The elasticity and plasticity of material are considered. Some computational results of several impact examples are shown.

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DETERMINATION OF DELAY TIME BY CALCULATING MUTUAL INFORMATION WITH EQUALLY DISTANT SPACE CELLS Yang Zhian, Wang Guanrui, Chen Shigang 1995, 12(4): 442-448.  Abstract ( )   PDF (438KB) ( )   Space cells are divided by equal distance step for calculating mutual information, and delay time. This approach is simpler than that of equal probability method. Numerical results indicate that this method can determine the correct delay time, and yield the reconstructed states in the case of forced brusselator.

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NUMERICAL SIMULATION OF ACOUSTIC FIELD IN A FLUID-FILLED BOREHOLE SURROUNDED BY HORIZONTICAL THIN-LAYERED MEDIA WITH THE SEMI-ANALYTICAL METHOD Dong Hefeng, Wang Kexie, Dong Qingde 1995, 12(4): 449-456.  Abstract ( )   PDF (506KB) ( )   The acoustic wave field excited by a pulsed point source in a fluid-felled borehole surrounded by horizontal multiple-layered media is solved by the send-analytical method. The general reflected matrix between layers is found with the mode solutions so that field of every horizontal region is expressed by the general reflected matrix.The formal solutions of n-layered formation are obtained.Numerival calculation is made on three-layered medial out of borehole. The correct display of head wave arrival is got.The effect of the thin layer on the head wave arrival and amplitude is discussed.The work in this paper make it is possible to investigate the ability to divided layer longitudinally in acoustic logging.

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PC VERSION OF MCNP-3a AND ITS GRAPHIC DEVELOPMENT Gao Yanfeng 1995, 12(4): 457-460.  Abstract ( )   PDF (261KB) ( )   The paper presents a MCNP-3a PC version, with the graphic function and friendly user interface,and briefly describes the struct of this version and the method which the new version is created under MS-DOS with the NDP Fortran-386 compiler. All 13 examples are recomputed correctly.

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FUZZY QUALITY JUDGEMENT OF ELECTRON OPTICAL SYSTEM Let Wei, Tong Linsu, Yang Hui 1995, 12(4): 461-466.  Abstract ( )   PDF (361KB) ( )   In electron optical system, electron beams emitted by cathode will be focused and deflected by electron optical system, and then it will hit the screen with small size. Because deflection system has deflection aberration, the electron beam that is focused into one point in the centre of screen will not be focused well in the corner of screen, and it will become a circle spot. Because decison of the spot quality on the screen is ac, this paper described the hay research for electron optical syStem quality.The spot size on screen is changed with the changing of screen location, so the' electron optical system quality is receded fuzzily when screen location is changed. According to these fuzzy decisions, a best structure of electron optical system can be founded.

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THE INVERSE EIGEN-PROBLEM FOR SYMMETRIC TRIDIAGONAL MATRICES AND PERIODIC SYMMETRIC TRIDIAGONAL MATRICES Yin Qingxiang 1995, 12(4): 467-474.  Abstract ( )   PDF (376KB) ( )   This paper deals with the reconstruction of symmetric tridiagonal matrices and periodic symmetlic tridiagonal matrices from eigen-pairs of the matrix and its largest leading principal matrix. The necessary and sufficient conditions for the existence and uniqueness of the solution are given. Some numerical algorithms are presented.

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A Macsyma Package for the Multiplicity of States and for the CFPs in a System of Identical Bosons Long Guilu, Wang Jiajun, Han Qizhi 1995, 12(4): 475-482.  Abstract ( )   PDF (465KB) ( )   A Macsyma package is presented for obtaining the multiplicity.of states and the coefficients of fractional parentage in a system of identical boson system. The package uses recursion formula for the multiplicity of states. This program for CFP uses a new recursive formula which includes explicitly the boson seniority number.

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A SELF-CONSISTENT MONTE CARLO SIMULATION OF IONS IN CATHODE SHEATH OF ARGON GAS DISCHARGES Wang Dezhen, Zhang Jianhong, Gong Ye 1995, 12(4): 483-489.  Abstract ( )   PDF (392KB) ( )   A self-consistent Monte Carlo simulation method that includes charge exchange and elastic scattering is developed to calculate the energy and angle distributions of ions in cathode sheath of a DC argon gas discharge for the different pressures. Cross sections of the charge exchange and the momentum transfer that depend on the ion energy are taken into account precisely. It is found that, as the ions move towards the cathode, the high energy portions of ion energy distributions are enhanced gradually and the small-angle portions of the angle distributions increase. A strong field accelerates the ions to higher speed and ensures that more ions move along the lines of force. The self-consistent electric field spatial variation in the sheath is nonlinear.

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Effects of Configuration Mixing and Relativistic Corrections on Dielectronic Satellite Spectra for He-like Ions Zhao Libo, Han Guoxing, Li Shichang 1995, 12(4): 490-498.  Abstract ( )   PDF (517KB) ( )   Effects of condguration mixing and relativistic corrections on the dielectronic satellite spectra have been studied for the He-like ions with low-and medium-Z. The atomic Parameters characterizing the dielectronic satellite lines are evaluated by using the send-and non-relativistic Hartree-Fock models. The results calculated show that (1) configuration mixing has an important effect on the dielectronic satellite spectra for the He-like ions, and (2) for the medium-Z He like ions, it is no longer sufficient that the effects of relativity are considered in the form of perturbation energy corrections, and in order to obtain more accurutc numerical results, relativistic corrections should be made both for energy and for radial wavefunction.

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DAMPED AND WEIGHTED LEAST-SQUARE SOLUTION FOR SEISMIC TRAVELTIME TOMOGRAPHY Song Linping 1995, 12(4): 499-504.  Abstract ( )   PDF (420KB) ( )   The reconstruction of seismic wave-speed distribution is nonlinear. Seismic ray path is calculated by using a model of the square of slowness. A parameterization of the model based on first order B-splines provides nonnegative matrix of the linear systems. In order to improve the solution stability, a damped, and weighted least-square procedure is proposed for considering the priori information of ray distribution. It gives numerical modelling examples as well.

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PATH-INTEGRAL MONTE CARLO METHOD AND NONLINEAR RANDOM VIBRATION Ji Qing, Feng Guanmin, Yu Ting, Yu Kai 1995, 12(4): 505-510.  Abstract ( )   PDF (385KB) ( )   A new method for nonlinear random vibration-the Monte Carlo method based on the path-integral formalism is presented. The statistics of response of nonlinear systems to white noise excitation is represented in the path-integral forms. Then the Monte Carlo method is used for calculation. Due to the natural combination of the path-integral formalism and the Monte Carlo method, the new method is very concise and straightforward.Some aspects related to applications are discussed, and two numerical examples give the verification of the new method.

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MASS RECONSTRUCTION OF H→ZZ (WW)→llvv BY NEURAL NETWORK Zhang Ziping, Cheng Jinrong 1995, 12(4): 511-514.  Abstract ( )   PDF (294KB) ( )   The main difficulty of heavy Higgs search through H°→ZZ (WW)→llvv channel at LHC pp collider comes from the large energy loss, so it is impossible to reconstruct its invariant mass by conventional method, its existence can only be seen through Jacobi peak of pTZ or mT distribution. As a phenomenological study based on Monte Carlo simulation, a feed-forward neural network is designed to reconstruct Higgs invariant mass for giving correct MH mass position and satisfactory width, as well as the background rejection ability. This method is proved to be quite suitable for new praticle search and mass measurement in experiment.

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A SPLINE MIXED ELEMENT METHOD FOR ANALYSIS OF PLATES AND SHELLS Shen Pengcheng, Yu Jingping, Zha Yijun 1995, 12(4): 515-522.  Abstract ( )   PDF (422KB) ( )   spline mixed element method is presented for solving the problem of bending plates and shells based on the application of cubic spline functions and generalized variational principle with two kinds of variables. Two kinds of field functions are constructed by using splinest one is the displacement function and another is the generalized force field function.The spline mixed element equations are derived by using the generalized variational principle with two kinds of variables. The spline interpolating function is both analytic and numeric, and has sufficient continuity, high approximate precision, both field functions are independent, and so the two kinds of field variables have good accuracy. Several numerical examples are given and show that the computed results are in good agreement with the corresponding exact solution.

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COMPLEX SOURCE REPRESENTATION AND ALGORITHM FOR APERTURE RADIATION Yao Dezhong 1995, 12(4): 523-527.  Abstract ( )   PDF (329KB) ( )   Kirchhoff's complex spatial convolution formula is developed as a new algorithm for radiation from a aperture. It is based on hte idea of analytic ectention that the original aperture field is extended to a complex plane.and then the kirchhoff's complex spatial-convolution formula makes up an indirect and rigorous representation of radiation from a plane aperture.Numerical tests confirm its correctness and efficiency.

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NUMERICAL SIMULATION OF TEMPORAL AND SPATIAL SHEATH EVOLUTION IN PLASMA SOURCE ION IMPLANTATION Song Yuanhong, Gong Ye, Wang Dezhen 1995, 12(4): 528-534.  Abstract ( )   PDF (458KB) ( )   In plasma source ion implantation (PSⅡ), the target immersed directly in a uniform Plasma is biased with high negative voltage pulse.Soaexpanding plasma sheath forms between the plasma and the surface of solid material and implant ions into the target. A numerical simulation model in one-dimensional planar geometry is developed to determine the temporal and spatial evolution of the sheath for the voltage pulse of rectangular and trapezoidal wave forms. Especially, the sheath evolution is simulated at the fall time of a trapezoidal voltage pulse.By numerical results the forcing of the presheath exhibits to be related to the pulse length and the applied voltage.

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NUMERICAL SIMULATION OF THE TRANSIENT SOLIDIFYING PROCESS FOLLOWING LASER SURFACE REMELTING Let Yongping, Shi Yaowu, Zhou Jiajin 1995, 12(4): 535-540.  Abstract ( )   PDF (375KB) ( )   According to the multi-region features in alloy solidifying process,numerical simulation of rapid solidification following laser remelting is performed by using a one -phase continuum model based on the conservation of total mass, momentum and energy. The release of latent heat, the energy flux leaving the surface by radiation and natural convecton into the atmosphere are included. The finite difference method is used to solve the equations. The flow field and temperature distribution within the liquid pool during rapid solidifying process are studied for lCrl8Ni9Ti stainless steel. Results show that the moving speed of iiquidus line is greater than that of the solidus line during solidifying process, and at the end of solidification of the molten pool, there is a period of time during which the mushy region and solid region are coexist.

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THE SOLUTION OF SINGULAR BOUNDARY VALUE PROBLEMS IN TEARING MODE Long Yongxing 1995, 12(4): 541-546.  Abstract ( )   PDF (332KB) ( )   A numerical code has been established for solving self-consistent equilibrium equation and calculating the dependence of the tearing mode on the current density profile. The external belieal field effect is included in it.The dynamic alternating direction implicit method is applied to speed up the convergence of solution of equilibrium equation and three-point difference secheme is taken to solve the singular boundary value problem with two singular points.

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A SIMPLE MULTI-SPEED MODEL OF LB METHOD Li Yuanziang, Chen Juhua, Huang Zhangchan 1995, 12(4): 547-553.  Abstract ( )   PDF (449KB) ( )   A simple two-dimensional lattice Boltzmann model with three speeds is studied. The local equilibrium distribution functions are determined under the restrained conditions of fluid dynamics by connecting the discrete model with the continuum macro-models. Euler equation and Navier-tokes equation are derived by using Chapman-Enskog expansion and multi-scalar technique, and the viscosity formula is also provided.The model has been applied to cavity flow problem with satisfactory results.

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CHIMERA GRID-EMBEDDING TECHNIQUE AND ITS APPLICATION Sun Gang, Qiao Zhide 1995, 12(4): 554-560.  Abstract ( )   PDF (443KB) ( )   A three-dimensional chimera grid-embedding technique is used for complex configuration. The technique simplifies the construction of computational grids about complex geometry.The method subdivides the physical domain into regions which can accommodate easily generated grids. Communication among the grids is accomplished by interpolation of the dependent variables at grid boundaries. An chimera grid-embedding scheme is implemented for a C-5A wing/body/pylon/nacelle. Numerical results show that the present algorithm is stable, accurate, and can be used effectively to compute the flow field about complex configuration.

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SPATIAL DISTRIBUTION OF BACKSCATTERED ELECTRONS IN SOLIDS BY MONTE CARLO SIMULATION Tan Zhenyu, He Yancai 1995, 12(4): 561-564.  Abstract ( )   PDF (245KB) ( )   The spatial distribution of backscattered electron in solids have been calculated by Monte Carlo method, based on Mott cross-section for elastic scattering as well as Streitwolf,Quirm and Gryzinski's cross-section for inelastic scattering. Some regularities have been acquired from a large amount of calculations, providing a certain basis for the quantitative research of low-energy electron microscopy.

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THE DIFFERENCE SCHEMES WITH HIGHER STABILITY PROPERTIES FOR A CLASS OF EVOLUTION EQUATION Zeng Wenping 1995, 12(4): 565-570.  Abstract ( )   PDF (350KB) ( )   In order to solve a class of evolution equaiton ut=au2K+1(where a is constant, u2K+1=∂2K+1/∂x2K+1,K=l,2,……) two classes of explicit difference schemes with higher stability properties are constituted. And two classes of semi -explicit difference schemes are also established by introducing a dissipative term, they are unconditionally stable and can be calculated explicitly.

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A SEMI-ANALYTICAL METHOD BASED ON GURTIN VARIATIONAL PRINCIPLE TO SOLVE 1-D INITIAL-VALUE PROBLEMS OF DYNAMICS UNDER ALTERNATE FORCES Peng Jianshe, Zhang Jingyu 1995, 12(4): 571-575.  Abstract ( )   PDF (298KB) ( )   A semi-analytical method is derived on the basis of Gurtin variational principle for solving one dimension initial-value problems of dynamics under alternating forces. This method takes finite element discretization in space domain and series in time domain.