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25 May 1998, Volume 15 Issue 3 Previous Issue    Next Issue

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COMPUTING OPTIMIZATION OF FAST FOURIER TRANSFORM ALGORITHM Lei Guangyu 1998, 15(3): 257-260.  Abstract ( )   PDF (144KB) ( )   The computing optimization has been done for Fast Fourier Transform algorithm. The methods of optimization and efficiency are presented. Contrasting calculations are performed on several computers. Average operating speed is increased by a factor of 7~10.

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THEORETICAL INVESTIGATION ON CHARGE TRANSFER IN ION COLLISIONS Qiu Yubo, Long Yanqiu, Chen Guoxin 1998, 15(3): 261-266.  Abstract ( )   PDF (250KB) ( )   The classical trajectroy Monte Carlo method is empolyed to calculate the charge transfer cross sections and the n shell distribution of capture electron for the collision of ions with hydrogen.For the collision of partial ionized ions with hydrogen,a q-scaled cross section is obtained by introducing the reduced variables.The present results are in good agreement with experimentally measured results.

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THE STABILITY OF HARMONIC RESONANCE OVERVOLTAGE (Ⅰ) Wang Jian, Wang Zhengxian 1998, 15(3): 267-272.  Abstract ( )   PDF (177KB) ( )   A numerical approach is presented for simulating the stability of harmonic resonance overvoltage in power systems and the relationship is discussed between the stability of harmonic solutions and the change of parameters of system by using the methods of Galerkin and Runge Kutta.It can be used for describing further bifurcation phenomenon in power systems.

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NUMERICAL STUDY ON PHASE-DEPENDENT IONIZATION RATE OF ATOMS IN AN INTENSE LASER AND ITS SECOND HARMONIC Chen Jing, Chen Shigang, Liu Jie 1998, 15(3): 273-276.  Abstract ( )   PDF (174KB) ( )   Ionization rate of Hydrogen atom in a two-color laser field is calculated by using the method developed by Kulander etc.Change of ionization rate-phase relation is found when the field intensity goes up to threshold and comparison with classical calculation has been done.

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NUMERICAL SIMULATIONS OF THE FCT METHOD ON RAYLEIGH-TAYLOR AND RICHTMYER-MESHKOV INSTABILITIES Ye Wenhua, Zhang Weiyan, Chen Guangnan, Jin Changqiu, Zhang Jun 1998, 15(3): 277-282.  Abstract ( )   PDF (272KB) ( )   The low phase error FCT numerical algorithm is introduced,and used to simulate Rayleigh-Taylor(RT) and Richtmyer-Meshkov(RM) instabilities.Simulation results agree well with the linear theories of RT and RM instabilities and the calculation of the shock tube experiment of Russia.It shows that the FCT method is fit to simulations of instabilities of ICF problems.

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THE BLOCK MULTISPLITTING METHOD AND PRECONDITIONED KRYLOV ITERATIVE METHODS Liu Xingping, Hu Jiagan 1998, 15(3): 283-296.  Abstract ( )   PDF (423KB) ( )   Algorithms of the block multisplitting and preconditioned Krylov iterative Method for linear systems of the form Ax=f are proposed,where A is block tridiagonal matrix. The convergence of these iterative methods is analysed,when A is an M matrix or H matrix.The resulting MPPE method and preconditioned AKrylov method have been tested on a Challenge L computer.Numerical examples indicates that the new method is very efficient,since the parallel computation can be applied.

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FAST ALGORITHM FOR THE COMPUTATION OF GREEN'S FUNCTION FOR POTENTIAL IN STRATIFIED MEDIA Wang Gongli, Chang Lin 1998, 15(3): 297-302.  Abstract ( )   PDF (264KB) ( )   The numerical solution of Green's function for potential in axisymmetrically stratified media with axial inhomogenity is given using the duality of the hybrid method,which is then applied to the computation of response of the fundamental resistivity tool.Compared with the 2D finite element method,this algorithm is of higher efficiency because of the reduction of the problem dimension.

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SIMULATION OF FLOW PAST CYLINDRICAL OBSTACLE VIA LB METHOD Chen Juhua, Li Yuanxiang, Xiong Shengwu 1998, 15(3): 303-307.  Abstract ( )   PDF (275KB) ( )   A parallel computational model of simulating hydrodynamic phenomena is introduced. This model is used to simulate Karman votices streets. By using the computer visualization technique, it can automatically and dynamically demonstrate the evolving process of fluid flow, and easily analyse the variety of hydrodynamic phenomena.

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THE NUMERICAL METHOD OF SIMULATING THE HOLE-COUPLING FEL OSCILLATOR Wang Yuanzhang 1998, 15(3): 308-314.  Abstract ( )   PDF (257KB) ( )   Since the presence of a out coupling hole alters the transverse structure of the intra cavity light in a FEL oscillator,the finite element method is used to the optical field equations and a good proximation is made for the out-coupling process in the mirror,and then some numerical results are given.It is shown that the features of the transverse structure of the intra-cavity field are well described and the numerical results are significantly improved.

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OPTICAL TRANSFER FUNCTION IN ANAMORPHIC IMAGING Wang Qi 1998, 15(3): 315-320.  Abstract ( )   PDF (226KB) ( )   In the traditional methods of computing the OTF,it is general that the transversal magnification is supposed to be not changeable in the whole aperture,though the anamorphic imaging produces considerable errores in the calculation of the OTF.People do not still find a good method to solve the problem.Starting from the Kirchhoff diffraction integral,the classical formula of the OTF in the Fraunhofer approximation is a new derived in the exit pupil coordinates and in the entrance pupil coordinates.Using piecewise polynomial interpolation,the OTF in the exit coordinates is studied for anamorphic imaging.It also gives comparison with the OTF formula of in the Fresnel approximation.

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INVERSION OF THE CONDUCTIVITY IN THE LARGE FORMATION REGION USING THE MULTI INFORMATION OF ARRAY Zhang Yerong, Nie Zaiping, Qi Lanfen, Zhang Tiyuan 1998, 15(3): 321-330.  Abstract ( )   PDF (385KB) ( )   A new distorted Born iterative method is applied to inversion of large formation region by using the multi information of array.The region consists of the complicated transition zones and the raw formation without mud invasion.The method,based on nonlinear integral equation,is used to solve for the formation conductivity profile by using regularization.In each iteration,the numerical mode matching method is used to solve the forward problem of the induction.Some simulations show that the imaging results are in much good agreement with the true conductivity profile by array multi-information on the axis of symmetry.

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Möbius Transform and Its Applications in Physics Li Weinan 1998, 15(3): 331-336.  Abstract ( )   PDF (208KB) ( )   Möbius inverse formula is an old theorem in number theory. Professor Chen Nanxian extended it to ordinary function and presented a new method for solving many inversion problems in physics. This paper introduces Chen's theorem with a more comprehensible way and shows its vast range of application prospects by some concrete problems.

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DISCRETE ORDINATE SOLUTIONS OF RADIATIVE TRANSFER EQUATION Liu Linhua, Yu Qizheng, Ruan Liming, Tan Heping 1998, 15(3): 337-342.  Abstract ( )   PDF (281KB) ( )   The discrete ordinate approximation method of three-dimensional radiative transfer equation in absorbing scattering medium is expounded. The selection of quadrature sets of in-scattering term are analysed. The causes about the formation of false scattering and ray effect and its influence on the accuracy of solutions are also analysed. By detailed comparison, it is shown that false scattering and ray effect exact not only in discrete-ordinates method, but also in zone method, discrete transfer method, etc., and the influence of false scattering and ray effect on solution accuracy of radiative transfer equation can be reduced by decreasing grid size and increasing the number of solid angle discretation. The process of radiative heat transfer in a three-dimension rectangular furnace is simulated using discrete ordinates method. By comparison with zone method and discrete transfer method, it is found that discrete ordinates method has a good accuracy, and recently is one of the best method to simulate the process of radiative heat transfer in furnace.

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CALCULATION FOR FRANCK-CONDON FACTORS OF THE RADIATION BAND SYSTEMS OF BN、BH MOLECULES Zhang Zhongming, Xiong Ye 1998, 15(3): 343-348.  Abstract ( )   PDF (192KB) ( )   From the nuclear Schrdinger equation of a diatomic molecule with the vibration-rotational interaction term involved in it, under the Morse potential approximation, it derives the wavefunction relevant not only with vibrational quantum number, but also with rotational one. The Franck-Condon factors of the two band systems A3Π-X3Π of BN and A1Π-X1∑+ of BH are calculated by use of the derived wavefunction. In the calculation, the rotational quantum number ranges from J=0 to J=180. The results obtained can be used in the cases under low-or high-temperature condition and also under the condition of strong shock wave.

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A Level Set Approach Simulating Topological Changes of Gas-Liquid Interface in Small Scale Incompressible Viscous Xu Jun 1998, 15(3): 349-356.  Abstract ( )   PDF (320KB) ( )   An updated version of level set method without reinitializing step is designed to simulate the motion of a small volume of gas rising up to and bursting at an initially horizontal free surface. Accompanying topological changes of the gas-liquid interface, such features of the series of rotational motion as cavity, upward-jet, viscous-gravity-capillary waves along the merged interface are captured in the numerical examples. In some cases, smaller volumes of liquid may break off the jet at certain stage. In others, the free surface may roll up. In the tests, Reynolds number, Weber number, and gravitational acceleration are allowed to vary in wide ranges.

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AN IMPLICIT SCHEME OF THE HYBRID FINITE DIFFERENCE FINITE ELEMENT METHOD Duan Zhanyuan, Tong Binggang, Jiang Guiqing 1998, 15(3): 357-362.  Abstract ( )   PDF (244KB) ( )   A new finite element implicit scheme is constructed by using the Hybrid Finite Difference-Finite Element Method in. The implicit scheme overcomes the diffculty of solving large sparse matrix and demanding huge capacity in traditional finite element implicit schemes and at the same time, makes use of the approximate factorization and diagonalization techniques in finite difference method to acquire high calculation efficiency.

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THE ALGORITHM OF REBUILDING THE LOGGING CURVE BY SIMILAR LOGGING DATA AND ITS APPLICATION Luo Chaosheng, Wang Fuquan 1998, 15(3): 363-366.  Abstract ( )   PDF (160KB) ( )   By using the mathematical model of fractal insertion, an algorithm is given for auoustic logging curve based on similar logging data. When applying it to processing of the data of 7 similar logging in Dan Feng Chang, Sichuan and 3 similar logging in Nan Hai, the obtained fractal curve is very close to the real acoustic logging curve, with correlation coefficient greater than 70%. This method makes it possible to get the same message of logging curve from the CDP recording of the seismic prospecting.

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STUDY OF THE METHOD FOR DETECTING THE IMAGE SIDE MTF OF THE VERTICAL DIRECTION OF AN IMAGING SPECTRUM SYSTEM Huang Xiaoxian 1998, 15(3): 367-371.  Abstract ( )   PDF (196KB) ( )   The key parameter which describes the spatial resolution of imaging spectrum system is the modulation transfer function (MTF), it is an old and difficult topic to measure the MTF. Under the input scenery with finite visual field, the analyses and simulative calculation of the image-side OTF of vertical direction of the scanning image by moving blade have been done firstly.

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EFFECTS OF IONIC TYPES IN HOT MATTER ON PHOTOIONIZATION PROCESSES Meng Xujun, Sun Yongsheng 1998, 15(3): 372-376.  Abstract ( )   PDF (187KB) ( )   Based on fully relativistic HFS self-consistent field AA model, the emerging probabilities of ionic types are determined in analytic formula using the principle of the maximum entropy, and the ionic structures are obtained in peturbation way. All the contributions from over millions of ionic types are taken into account in statistical method according to convolution principle. Finally the formula of extinction coefficient for bound free transition in hot matter with the statistical effects is given, and some results for iron are discussed.

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OPTIMAL EFFICIENCY CONTROL EQUATION FOR DRIVE SYSTEM WITH FREQUENCY CONTROL Zhang Chenghui, Tan Zhenyu 1998, 15(3): 377-384.  Abstract ( )   PDF (294KB) ( )   For various typical loads including fan pump loads; constant torque loads and constant power loads, the optimal efficiency control equation and its constraint conditions are given using the linearizing expression of the motor. Some simulation computations are provided, and a comparison is made between the results of the new method and those of the model based method for efficiency optimization.