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25 March 1988, Volume 5 Issue 1 Previous Issue    Next Issue

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ON THE PROBLEM OF ENERGY CONSERVATION IN SIMULATION OF HIGH ENERGY MULTIPLE PRODUCTION PROCESSES Wang Guang-jun, Ding Lin-kai, Zhu Qing-qi, Jing Gui-ru, Chi Shin-yu, Zhang Ming, He Yu-dong 1988, 5(1): 1-8.  Abstract ( )   PDF (457KB) ( )   A Probability description of an empirical method (called method A in this paper) used in simulations of high energy multiple production processes in which not only single particle momentum distribution but also energy conservation can be satisfied is presented and mathematically deduced. The applicable condition of method A is discussed.

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THE STOKES FLOW IN AN ORIFICE WITH AN OBSTACLE AT ITS AXIS Chen Yao-Song, Cao Nian-Zheng, Chen Yan 1988, 5(1): 9-15.  Abstract ( )   PDF (380KB) ( )   The flexibility of the F.E.M has been used to study the flow in a very complex flow region, which includes pipe, obstacle and half infinite space. In order to minimize the number of elements in the infinite domain, similar elements, are settled in it and have been canceled but one in advance of calculation. The whole method is effective and the calculated result is reasonable.

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COMPUTATION OF THREE-DIMENSIONAL TRANSONIC POTENTIAL FLOW IN TURBOMACHINERY BY A MAF SCHEME Zhang Jia-lin 1988, 5(1): 16-26.  Abstract ( )   PDF (632KB) ( )   Based on the AF2 scheme and the multiple grid scheme, a fast implicit multigrid approximate factorization scheme (MAF) for solving the three-dimensional conservative full potential equation has been developed and is presented in this paper. The new MAF scheme has been used to solve the three-dimensional transonic flow within DFVLR axial-flow single-stage compressor rotor, and the computed results have been compared with the DFVLR data and the results computed by AF2 scheme.

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THE COUNT AND DETERMINATION OF M ORDERS UNIT ROOT FOR MODUL M Li Feng-lin 1988, 5(1): 27-35.  Abstract ( )   PDF (525KB) ( )   In this paper, the method to determine all parameters a for MCS(xnΞaxn-1(modM),n ≥ 1) with any Period m is given on the basis of the theorems in[1] We deduce the parameters a from seeking m orders unit root for modul M' (M'=M/d, (x0,M)=d)and propose the simplified algorithms to do so for the composite m. A numerical example shows the correctness of the method.

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THE PREDICTOR-CORRECTOR DIFFERENCE SCHEMES OF POISSON EQUATION Luo Zhen-ou 1988, 5(1): 36-46.  Abstract ( )   PDF (549KB) ( )   In this paper the predictor-corrector difference schemes of three-dimensional Poisson. equation with Dirichlet or/and Neumann boundary value problems are studied. It contains a complete set of schemes of the difference nodes which arc in inner region or in boundary planes, boundary lines and boundary corners. The new finite difference schemes can attain four-order accuracy with the least computational error by optimizing the selected factor.

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THE STUDY OF IMPORTANCE SAMPLING IN MONTE-CARLO CALCULATION OF BLOCKING DIPS Pan Zheng-ying, Zhou Peng 1988, 5(1): 47-52.  Abstract ( )   PDF (396KB) ( )   Angular blocking dips around the <110> axis in A1 single crystal of α-particles of about 2Mev produced at a depth of 0.2uuuuuuuuuuuuuum are calculated by a Moute-carlo simulation.The influence of the small solid angle emission of particles and the importance sampling in the solid angle emission have been inve-stigated.By means of importance sampling,a more reasonable results with high accuracy are obtained.

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NUMERICAL SOLUTION OF NATURAL CONVECTION IN AN ENCLOSED SQUARE CAVITY WITH MAC-TYPE METHODS Shen Jian-Xiong 1988, 5(1): 53-68.  Abstract ( )   PDF (960KB) ( )   In this paper, the experience of calculating natural convection in an cncloscd square cavity is summarized. Numerical boundary conditions of the MAC method are simplified and the accuracy improved. The FTCS scheme of the MAC method can be replaced by leapfrog and Dufort-Frankel scheme to relax the stability limit on the time step. Numerical results for Rayleigh number 106 are given and compared with bench mark results.The influence of different initial temperatures for unsteady flow is discussed. The results of mteady flow are in agreement with theory. Finally, treatment of outflow boundary is discussed.

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ONE-DIMENSIONAL NUMERICAL SIMULATION OF FREE-ELECTRON LASER (FEL) AMPLIFIER WHICH INCORPORATE VARIABLE-PARAMETER WIGGLER MAGNETS Jing You-ming, Ying Run-jie 1988, 5(1): 69-79.  Abstract ( )   PDF (601KB) ( )   In this paper, we present a physical model of free-electron laser (PEL) amplifier which incorporates variable-parameter wiggler magnets for one-dimensional numerical simulation and a numerical example is given.We have computed the wiggler parameters, efficiency of energy conversion between electron beam and laser field, laser intensity, phase-space distributions and energy spectrum of electrons.The period of synchronous oscillation and saturation value of laser intensity agree with estimated one.

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DISCRETE FOURIER TRANSFORMATIONS WITH WEIGHT Wang Qin, Jiang Yong 1988, 5(1): 80-86.  Abstract ( )   PDF (418KB) ( )   In this paper DFT and FFT with weight are considered and their properties are studied. The modified the usual DFT and FFT by reducing the number of sample points mithin a certain error band and therefore speeding up the computation. Finally, we pointed out the practical applications of the new method in the fields of spectrum analysis, pulee tracing research and so on.

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APPLICATION OF MULTIGRID METHOD TO COMPUTE SEPARATION FLOW Chang Qian-Shun 1988, 5(1): 87-97.  Abstract ( )   PDF (632KB) ( )   The splitting difference scheme is used to study flow separation. Flows behind a Circular Cylinder are computed as a model problem. In view of the nature of the flows, the variables are transformed. The boundary condition for pressure is given by intermediate velocity. The velocity boundary Conditions on the rigid wall of free-slip are given by interpolation. The multigrid algorithm is applied to the Pressure iteration. We also Choose better initial Values for the model problem by means of the multigrid algorithm idea.

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THE APPLICATION OF MULTI-GRID METHOD IN THE CALCULATION OF SHALLOW-WATER WAVE Lü Qiu-qiang, Chou Gang, Liu Ying-zhong 1988, 5(1): 98-106.  Abstract ( )   PDF (413KB) ( )   In this paper, two finite-difference methods for shallow-water equation in absolute coordinate-system are proposed, an iterative algorithm is given, then the algorithm is applied to multi-grid methoe.

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MONTE CARLO SIMULATION OF A NEW SO(3) SPIN GLASS MODEL ON THE 2-DIMENSIONAL RANDOM LATTICES Ying He-Ping, Dong Shao-Jing, Yang Qing-Jan 1988, 5(1): 107-112.  Abstract ( )   PDF (406KB) ( )   A new spin glass model defined on the N×N 2-dimensional random lattice with the SO (3) spin variables is proposed, and. studied by Monte Carlo simulations. The thermodanamics, such as the internal energy and specific heat per spin and the topological excition are calculated. The thermal hysteresis and mix-phase runs are also made to obtain some information of the Phase transitions. A higher-order, instead of the usual first-or second-order, Phase transition due to the vortex condensation is found. Moreover, the results show the important frustration and disorder effects which are main causes of low-temperature properties of sPin glass.

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NUMERICAL SIMULATION OF STRATIFIED FLOWS OF INCOMPRESSIBLE FLUID Yu. I. Shokin, V. M. BeloliPetsky, V. Yu. Kostyuk 1988, 5(1): 113-128.  Abstract ( )   PDF (884KB) ( )   Construction of hydroelectric Power station with deep-water reservoir results in appreciable changes in hydrothermal state of the river near the waterworks facility# In deep-water reservoirs a temperature stratification of water is established, the temperature of the water noticeably changes with depth. Both theoretical and experimental investigations have shown that the velocity and temperature distribution of the non-homogeneous fluid near a dam depends on the character of stratification, the discharge and the position of the intake apertures. Generally in studying stratified fluids one uses equations in Boussinesi approximation [1,2]. Studies aiming to an optimal selection of the location of withhdrawal from a two-laycred fluid were conducted by a number of authors both theoretically and experientally.