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25 January 1997, Volume 14 Issue 1 Previous Issue    Next Issue

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STRUCTURE,PROPERTY AND QUANTUM CHEMISTRYCALCULATIONS OF CERAMICS OF TIC AND TIN Min Xinmin, Deng Zhiping, Li Jiayu, Yuan Runzhang 1997, 14(1): 1-5.  Abstract ( )   PDF (244KB) ( )   The relations among structure property and chemical bond of TiC,TiN and TiO ceramics,as well as Nb doped TiC,are studied with SCF Xα DV,one of the quantum chemistry calculating methods.The calculated results are consistent with the experimental results that the hardness and strength are in the order of TiC > TiN > TiO,and when Nb element added to TiC increases,the vacancies being in short of C atom increase,hardness and resistance of the series samples of (NbyTi1-y)Cx decrease correspondingly.

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NAVIER STOKES COMPUTATION OF NONEQUILIBRIUM CHEMICALLY REACTING FLOWFIELDS Ou Yang Shuiwu, Xie Zhongqiang 1997, 14(1): 6-12.  Abstract ( )   PDF (259KB) ( )   A new coupled chemistry NS numerical method is proposed for predicting finite rate chemically reacting re entry flowfields. The governing equations are solved using the upwind TVD shock capturing scheme. For simplicity, the present study focuses on axisymmetric flows;however, subsequent extensions to three dimensional flows and /or other chemical systems are also relatively straightforward. The overall Teflon air chemical reaction model used consists of 23 species and 35 gas phase reactions.The numerical simulations are made for the complete flowfield (fore body and near wake) over blunt sphere cone. The fully converged solution and the computational results are obtained. The computed peak electron densities in the clean air flowfield agree well with experimental results.

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COMPUTER RANDOM SIMULATION OF THE MAGNETIC PROPERTIES OF MAGNETIC LIQUIDS Liu Xuequan, Zhou Shouzeng, Wang Run, Teng Ronghou 1997, 14(1): 13-18.  Abstract ( )   PDF (231KB) ( )   This paper deals with a model and methods of computer random simulation of the magnetic properties of magnetic liquids. Effects of the concentration, temperature and particle size of magnetic liquids upon their magnetic properties have been investigated successfully by the calculation of reduced magnetisation of a system containing 32 magnetic particles with the model constructed.

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Application of Algebraic Multigrid Method to Solve the Splitting Scheme of One-dimensional Euler Equations Fu Hanqing, Chang Qianshun 1997, 14(1): 19-25.  Abstract ( )   PDF (91KB) ( )   A new algorithm of algebraic multigrid (AMG)method is proposed.As an important example, the AMG method is applied to solve the splitting scheme of the Euler equations.The equations with high CFL number can be calculated with the AMG method.This example demonstrates that the AMG method can solve the linear algebraic systems of equations unable to be solved by Gauss-Seidel iteration method.This is a new result and extends the range of application of the AMG method.

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NUMERICAL T-MATRIX SIMULATION FOR POLARIZED SCATTERING FROM CLUSTERED SPHERICAL PARTICLES Huang Xingzhong, Jin Yaqiu 1997, 14(1): 26-34.  Abstract ( )   PDF (318KB) ( )   As the scatterer's size is no less than or comparable with the wavelength, a rigorous solution of multiple scattering Maxwell's equation must be used. Multiple scattering formulation of T-matrix method is adopted to develop numerical simulations of polarized scattering from clustered spherical particles. Numerical results for coherent scattering from non uniformly clustered scatterers are presented. Numerical calculations are also well compared with experimental data of a two-sphere cluster.

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SYMPLECTIC ALGORITHM FOR HAMILTON MULTIBODY SYSTEM Wang Qi, Huang Kelei, Lu Qishao 1997, 14(1): 35-39.  Abstract ( )   PDF (203KB) ( )   The implicit symplectic algorithm of Hamilton multibody system with topological tree configuration is studied. The canonical equations of multibody system and Jacobian matrix of RHS of the equations are obtained in the form of matrix.The paper presents algorithm of Jacobian matrix to raise computational efficiency. The implicit symplectic Runge Kutta algorithm is used in solving the canonical equations of multibody system. Numerical results show that the algorithm has higher computational efficiency and can keep computation stable for long time simulation.

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EL 1D2D METHOD FOR CALCULATING LASER CAVITY TARGET FLOW Duan Qingsheng, Shen Longjun, Fu Hanqing, Pei Wenbing 1997, 14(1): 40-46.  Abstract ( )   PDF (282KB) ( )   In view of the complexities of laser cavity target flow, a numerical technique is presented that couples an Eulerian approximation with a Lagrangian approximation,onedimensional calculation with two dimensional calculation. We call it EL-1D2D method. On the basis of trace interface moving grid method, some particular technique is established mainly by setting an Eulerian line and by merging the zone adaptively beside the Eulerian line. Numerical results show that this method can calculated fairly complicated flow in the cavity and get reasonable physical image.

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CALCULATION AND ILLUSTRATION OF SECTION PROJECTION DIAGRAMS OF QUASICRYSTALS Lei Jianlin, Wang Renhui, Wang Zhouguang, Ding Dihua 1997, 14(1): 47-53.  Abstract ( )   PDF (351KB) ( )   Based on the cut and projection description of quasicrystals, a method for calculating section projection diagrams of quasicrystals is developed and applied to decagonal quasicrystals. Firstly, a section projection diagram parallel to the quasiperiodic plane of perfect decagonal quasicrystal is calculated. By using the existing elastic displacement field formulae, section projection diagrams parallel to the quasiperiodic plane of a decagonal quasicrystal containing a straight dislocation along periodic direction have been calculated when the phason strain and the phason phonon strain are introduced respectively.

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POTENTIAL THEORY AND ANALYTIC PROPERTIES OF THE SELF—AFFINE SET Shang Pengjian 1997, 14(1): 54-62.  Abstract ( )   PDF (302KB) ( )   The potential produced by a charge distribution on the self affine set and its analytic properties are studied. First, the structure properties are deduced of the charge distribution,the electrostatic potential and Fourier transform, then the explicit representatioin for the binornial distribution on the Cantor set, its moments, its Fourier transform and its potential are given with some numerical results.

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DETERMINING PERMEABILITIES OF POROUS MEDIA BY LATTICE BOLTZMANN METHOD Yan Guangwu, Hu Shouxin, Shi Weiping 1997, 14(1): 63-67.  Abstract ( )   PDF (219KB) ( )   The 7-Bit model of Lattice Boltzmann Method is used for simulation the porous media. Darcy law are found and the relationships of void ratio coefficient of viscosity and density with permeabilities are obtained as well.

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THE CONSERVATION OF THE SYMPLECTIC DIFFERENCE-SCHEME AND ITS STABILITY Ji Jianghui, Liao Xinhao, Liu Lin 1997, 14(1): 68-74.  Abstract ( )   PDF (248KB) ( )   Discussion is given on the existance of conservative laws of symplectic difference scheme for the Hamilton System and the relationship between them and the stability of the symplectic difference-scheme. The results show there are not any linear variations in all conservative laws of Hamilton System for symplectic difference scheme. In general, when the symplectic differencescheme stable, the conservative laws are convergent.

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THE IMPROVEMENTS AND APPLICATIONS OF SCF Xα SW AND LMTO PROGRAMS Wang Yi, Xie Yuannan, Li Shaomeng, Shen Longjun 1997, 14(1): 75-82.  Abstract ( )   PDF (292KB) ( )   Some improving works have been done on the SCF-Xα-SW and LMTO Programs by vectorization and parallelization.The energy level of C60 is researched.The 108 one electrom Rydberg excitation energies of benzene,such as 1e1g,2e2g,1a2u→ka1g(k=3-11),ke2g(k=2-7),ke1u(k=3-8),ke1g(k=2-5),ke2g(k=3-5),ke2u(k=2-3),kb2u(k=2-3),kb1u(k=2-3),1b1g,1b2g are calculated.The electronic structure and bulk modulus of some U-Ni alloys are also analyzed.

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CONVERGENCE OF NONLINEAR GALERKIN FINITE ELEMENT ALGORITHM FOR THE STEADY INCOMPRESSIBLE EQUATIONS OF THE NAVIER-STOKES TYPE Li Guancheng, He Yinnian 1997, 14(1): 83-89.  Abstract ( )   PDF (255KB) ( )   Here a practicable algorithm about the nonlinear Galerkin finite element algorithm is presented for the two-dimensional steady incompressible equations of Navier-stokes type is presented (or discassed),also the conver-gence and regularity of the numerical solution are analysed.If the grid parameter H and the finner grid parameter h(h1/2),the present algorithm has convergence rate of the same order as the standard Galerkin finite element algorithm.However,this algorithm is simpler than the Galerkin algorithm and can save a large amount of computational time.Finally,the numerical test is provided,which shows that the above conclusion is are true.

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NUMERICAL ITERATION OF PLASMA AND PARTICLE FLOW IN ARF PLASMA GENERATOR Wan Decheng, Dai Shiqiang, Chen Yunming 1997, 14(1): 90-98.  Abstract ( )   PDF (363KB) ( )   The injection of alumina powders into an inductively argon plasma is simulated numerically.Attention is given to the plasma particle interaction and its effects on plasma fields and particle trajectory and thermal history.It is demonstrated that for most applications,such interactions must be considered in any model.

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FINITE DIFFERENCE STUDY FOR CONVECTIVE BIFURCATION IN RECTANGULAR CROSS CAVITY OF POROUS MEDIA SATURATED WITH FLUID Kong Xiangyan, Lu Pengbo, Wang Xiaodong 1997, 14(1): 99-105.  Abstract ( )   PDF (290KB) ( )   The buoyancy convective flows in rectangular cross-section cavity of porous media saturated with fluid and heated form below are studied.The finite difference methods are used to study the bifuraction structure based on the bifurcation theory.Some typical figures of streamline and isotherm are given.The model exchange mechanisms of convection are discussed.Numenical results indude critical Rayleigh numbers and critical aspect ratios for exchange of some lower modes.

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FILTERED BACK PROJECTION METHOD OF CT TECHNIQUE FOR MAGNETIC FIELD IMAGING Wang Kuixiang, Deng Jingchuan, Gao Yi, Shen Erzhong, Xu Weiqing 1997, 14(1): 106-110.  Abstract ( )   PDF (202KB) ( )   A filtered back projection and computerization method of CT technique for magnetic field imaging is introduced and applied to perform reconstructed image of magnetic field leaking from a pair columnar Ba ferrite.The results confirm the efficiency of the method.

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STRUCTURES,PROPERTIES AND QUANTUM CHEMISTRY STUDIES OF TE-SE-I GLASS AND ADDINGAS AND GE ELEMENTS Min Xinmin, Deng Zhiping, Li Jiayu, Zhao Xiujian 1997, 14(1): 111-114.  Abstract ( )   PDF (165KB) ( )   Te-Se-I glass and adding As,Ge elements to it are studied with Self Consistent Field Diserete Variational Xα (SCF-DV Xα),one of the molecule orbital calculating methods in quantum chemistry.The chemical bonding is studied to discuss the relations between structures and properties with the variations of compositions of the glasses.The calculated results show that the strength of covalent and ionic bonds are both in the order of Ge-Se > As-Se > Te-Se, which is consistent with the experimental result of glass transition temperature(Tg) of the corresponding glasses.The Te-I bond in which I atom is one coordinate is stronger than that in which I atom is two-coordinate,As-I and As As bonds are both stronger than the two types of Te-I bonds.The weak Te-I bonds have been replaced by the stronger As-I and As-As bonds,which is just the reason why with the increace of As element,the structures and properties of Te2Se7-x-IAsx glasses can be changed.

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STUDY ON THE BLOCK UP COEFFICIENT TECHNIQUE APPLICATION TO IRREGULAR BOUNDARY SHAPE Liu Zhaocun 1997, 14(1): 115-120.  Abstract ( )   PDF (243KB) ( )   The block up coefficient technique is widely used to deal with irregular boundary shape due to its simple and highly accurate advantages.The present popular pressure velocity corrction algorithm and finite volume approach are proposed to numerically solve the complete Navier Stokes(N-S)equations.The applicability,feasibility and key techniques in the calculations of this method for irregular especially multiobstacle boundary shape are systematically discussed.Numerical results are satisfying.

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APPLICATION OF THE B SPLINE FINITE ELEMENT METHOD IN POLAR COORDINATES TO SOLVING BOUNDARY VALUE PROBLEMS WITH SINGULARITIES AT A SHARP CORNER Li Ronglin, Ni Guangzheng, Yu Jihui 1997, 14(1): 121-128.  Abstract ( )   PDF (313KB) ( )   Based on the distribution characteristic of fields in the neighbourhood of a sharp corner, the B spline finite element method in polar coordinates is exploited for solving the boundary-value problems with singularities at the sharp corner. The proposed method improves the overall accuracy and is convenient to implement. The Motz problem, cracked-beam problem, and eigenvalue problem for the sector waveguides are calculated and analyzed to verify the validity of the method.