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25 March 1995, Volume 12 Issue 1 Previous Issue    Next Issue

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PERIODICALLY MODULATED BISTABLE SYSTEM WITH NOISE Chen Yan, Wu Qitai 1995, 12(1): 1-9.  Abstract ( )   PDF (651KB) ( )   By using Monte Carlo Method, the characteristics of bistable dynamics system under the influence of periode and noise force are analyzed. The period non-stationary probability and the joint probability distribution for the system are acquired. Some topological relations among them and the force field and potential, the hole near the saddle point and force zero-point, and the "time bifurcation" are found. The jump characteristic and the signal intensity changing with parameter arealso discussed.

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FDTD SIMULATIONS OF MICROWAVE PULSE COUPLING INTO CYLINDRICAL CAVITIES Wang Jianguo, Qu Huamin, Hua Ming, Zhang Tingbin, Chen Yusheng, Fan Ruyu 1995, 12(1): 10-18.  Abstract ( )   PDF (513KB) ( )   A physical model is presented for linear coupling of microwave pulses into apertures in cavities. The numerical simulation method of FDTD and absorbing boundary conditions are dis cussed. We calculate coupling processes of microwave pulses into apertures with various size and different positions, and an alyse the dependence of coupling on aperture size and polarization direction of the incident field.

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BOUNDARY ELEMENT ANALYSIS OF SHEET FLOW IN BIOMECHANICS Han Qingshu, Yang Dequan 1995, 12(1): 19-24.  Abstract ( )   PDF (365KB) ( )   With boundary element method[1,2], this paperdeals with blood flow in the blood-vessel of lung. From the numerical simulation for the sheet fluid of SFH model and SFH model in the blood-vessel of lung, the velocity field of blood fluid, the distribution of surface force and pressure on the surface of the blood-vessel are given. The result shows that the stress suppressed on the skin cell of the lung blood-vessel is in the range from 0 to 4.48×10-5N/cm2. This is well consistent with Dewey's experimental result. Also the computational result shows that the formation of lung cell helps the breathing membrane supPOrt the smallest stress. Meanwhile, the method used in this paper provides an efficient approach to numerical analysis of the blood flow in the heart and blood vessel.

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THE COMPUTER CURVE FITTING FOR WELL-TESTING MATERIAL OF INFINITE NATURALLY FRACTURED RESERVOIR Lei Guangyao, Wu Shengchang, Zhang Shifen, Hu Chengxian, He Hongxian, Tan Renxuan 1995, 12(1): 25-29.  Abstract ( )   PDF (310KB) ( )   A computational formula of the theoretical curve for the curve fitting of well testing material of infinite naturally fractured reservoir is proposed. The double error control method and the logarithm searching method are used to seek the theoretical curve. A lot of experiments show that this method is with high precision and rapid calculating speed.

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FAST ALGORITHMS FOR RECONSTRUCTING WAVEFRONTS IN ADAPTIVE OPTICS Li Youkuan, Chen Dongquan, Xu Xishen 1995, 12(1): 30-36.  Abstract ( )   PDF (383KB) ( )   Light propagating through atmosphere will be distorted as a result of the random changing index of refraction along the light Path. This distortion lowers the optics system performance. Wavefront distortion can be compensated and corrected by adaptive optics systems. For real time compensation, systems must respond fast to the changing wavefront information. Three basic reconstruction schems are studied and fast algorithm is proposed using the block and sparse structure of the transformation matrix. Different wavefront reconstructions show that the algorithm is very effective.

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THE NUMERICAL SIMULATION OF FLOW IN S-SHAPED DIFFUSER Ma Handong, Li Feng, Zhou Weijiang, Wang Yiyun 1995, 12(1): 37-40.  Abstract ( )   PDF (278KB) ( )   Three-dimension, compressible, internal flow solution obtained using a modifiedBeam-Warming implicit factorization scheme is presented. Steady-state solution is obtained by solving numerically the full Navier-Stokes equations from given initial conditions until the time-dependent terms become negligible. The configuration considered is a rectangular cross-section, S-shaped centreline diffuser duct with an exit/inlet area ratio of 2.25. TheMach number at the duct entrance is 0.9 with a Raynolds number of 5.82×105. Two regions of separated flow exist within the diffuser. The detail flow field especially the developement process of secondary velocity patterns in transverse plane are pressented. Comparing with the results ofRef.[1]. they have a good agreement. The secondary velocity patterns are more reasonable.

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NUMERICAL INVESTIGATION OF FULLY DEVELOPED FLOW IN A CURVED DUCT OF RECTANGULAR CROSS-SECTION Part Ⅰ:Laminar Flow Su Mingde 1995, 12(1): 41-46.  Abstract ( )   PDF (384KB) ( )   The detailed formulae of Navier-Stokes equations in the orthogonal curved coordinate system, the numerical methods for the integration of the momentum equations and the solution of Polisson equation of pressure are described. The fully developed laminar flow in acurved duct of rectangular cross-section is simulated numerically and the results are compared with other results.

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NUMERICAL INVESTIGATION OF FULLY DEVELOPED FLOW IN A CURVED DUCT OF RECTANGULAR CROSS-ECTION, Part Ⅱ:Turbulent Flow Su Mingde 1995, 12(1): 47-53.  Abstract ( )   PDF (503KB) ( )   The basic principl of LES and SGS modelling is described. This method is used to simulate the fully-developed turbulent flow in a curved square duct numerically. Its results are compared with other numerical prediction. The structures in turbulent flow are disccused.

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NUMERICAL ANALYSIS OF ENERGETIC PARTICLE STABILIZATION OF BALLOONING MODES IN FINITE-ASPECT-RATIO TOKAMAKS He Qibing, Peng Qiyang, Qu Wenxiao 1995, 12(1): 54-62.  Abstract ( )   PDF (494KB) ( )   The effect of energetic trapped Particles on the stabilization of ballooning modes infinite-aspect-ratio tokamaks is numeically analyzed. The numerical solution of the corresponding integro-differential equation is obtained. Numerical results show that the instability domain of ballooning modes becomes smaller with the energetic particles pressure and the toroidal effect enhancing. The energetic trapped particles can Partially or completely stabilize the instability of ballooning modes.

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PHENOMENAL DESCRIPTION OF THE OPTICAL FIELD CHAOS IN FREE-ELECTRON LASERS Wang Wenjie, Wang Guangrui, Chen Shigang 1995, 12(1): 63-70.  Abstract ( )   PDF (482KB) ( )   The problem of optical field chaos in a storage ring free-electron laser oscillator hasbeen discussed, by using a phenomenal model. From the theoritical analysis and numerical simulation, it can be found that the variation of laser intensity versus time can be both periodical and chaotic when there is a weak gain modulation in the optical cavity. The correspondent leading Lyapunov characteristic exponent goes to a negative and a positive real number as time increases. Afurther research is carried out, and a chaotic transition via period-doubling bifurcation has been found by varing the modulation parameters.

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THE TRANSPIRATION COOLING CONTROL AND IT'S NUMERICAL SIMULATION OF SURFACE THERMAL PROTECTION FOR BODIES OF REVOLUTION Xu Yanhou, Wu Guangyu, Cong Guanghui, Yang Xueshi 1995, 12(1): 71-78.  Abstract ( )   PDF (496KB) ( )   The transpiration cooling control system of surface thermal protection for bodies of revolution at hypersonic is studied. Not only the critical transpiration quantity equaling to plane case is obtained, but also another smaller second critical transpiration quantity is found. When the transpiration quantity is between of this two critical transpiration quantities, the ablation will appear on the shield surface, but the ablation will stop automatically, and a remainder thickness of shield will be kept at last. Numerical simulation is accomplished and yields all kinds of charactdstic curves. Three methods of ablation control for shield surface are discussed:the controls are for surface temperature, for ablation quantity and for ablation beginning time, the rules for selecting control variable are given.

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DIMENSIONALITY COHERENCE OF HAMILTONIAN AND CONVOLUTION LAW OFPHONON DENSITIES OF STATES Zhang Haifeng, Xu Wenlan 1995, 12(1): 79-83.  Abstract ( )   PDF (311KB) ( )   According to the relationship among the lattice vibrational Hamiltonian of one-two-and three-dimensional systems, the convolution law of phonon densities of states at different dimension is given. Discussions are made on the condition of convolution law, the physical figuration correlated to the densities of states and the possibility and limitation of this method. At last, some results of several systems are shown and remarked.

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THEORETICAL STUDY ON RECOMBINATION PROPERTIES OF PLASMA PRODUCED BY LASER IRRADIATING RECTANGULAR TARGET Zhou Zhongyuan, Hu Shengyong, Ding Peizhu, Pan Shoufu 1995, 12(1): 84-94.  Abstract ( )   PDF (648KB) ( )   A computational code JLULP1 of plasma produced by laser irradiating rectangular target written by us is reported. By using this code, the spatial distrubutional and time-dependent properties of plasma produced by laser irradiating rectangular Sitarget, and the relations of plasma properties with shapes of target have been investigated for the first time. Comparison with the plasma produced by cylindrical target shows that the plasma produced by rectangular target favours three-body recombination.

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METHOD OF USING THE PROGRAMS WITH RECTANGULAR MESHES FOR COMPUTATION OF HTGR WITH PEBBLE BED FLOW Jing Xingqing, Zhong Wenfa 1995, 12(1): 95-101.  Abstract ( )   PDF (427KB) ( )   Descriptions are on situations about the fuel ball flow in curvilineal channel of High Temperature Gas Pebble Bed Reactor, and on the method of solving that problem by using the programs with rectangular meshes. This method has been used for the physical design of HTR-10MW Test Module and can be spread over other problems with curvilineal meshes.

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APPLICATIONS OF SYMPLECTIC ALGORITHMS TO THE NUMERICAL RESEARCHES OF RESTRICTED THREE-BODY PROBLEM Liao Xinhao, Liu Lin 1995, 12(1): 102-108.  Abstract ( )   PDF (428KB) ( )   The restricted three-body problem is a Hamiltonian dynamical model used usually in dynamics of the solar system. At present, Numerical methods are mainly adopted for some important problems. It is due to the fact that the mathematical tools or methods are poor. But, in order to understand the evolution of the solar system, it needs to dolong-term tracking computations. Hence the requirement for algorithms is very high, that is to say, the algorithms must maintain the global characteristics of the motions. The symplectic algorithms just satisfy the requirement. In this paper, an explicit symplectic difference scheme has been constructed for circular and elliptic restricted three——body problem in the rotative coordinate system by means of algorithm composition, respectively.Some computational examples have shown the scheme is effective.

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CALCULATION OF FIRST ORDER APPROXIMATELY FOR TRIANGLE-PROFILE GRADED INDEX SINGLEMODE OPTICAL FIBER Yuan Libo, Yuan Changxin 1995, 12(1): 109-114.  Abstract ( )   PDF (324KB) ( )   Under the condition of weak waveguiding, the effect of index gradual change is considered. The gradient index ∇ε as perturbation term is introduced in the scalar Helmholtzequation, and the perturbation method is used to solve the problem of triangular-profile gradient index single-mode fiber, which can shift the dispersion minimum from the wave length 1.31μm to 1.55μm. The first order correct solution is given with an integral form and numerical results calculated by integral expression are also given.

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An Alernating Segment Crank Nicholson Scheme For Parabolic Equation Zhang Baolin, Su Xiumin 1995, 12(1): 115-120.  Abstract ( )   PDF (293KB) ( )   An alternating segment Crank-Nicholson method for the diffusion equation is constructed.The method is unconditionally stable and has the obvious property of parallelism.Numerical results for an example show this new method has satisfactory.

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MODIFIED 2PPJ ALGORITHM Hu Jiagan, Liu kingping 1995, 12(1): 121-126.  Abstract ( )   PDF (368KB) ( )   A modified two-parameter parallel Jacobi-Type algorithm (M2PPJ) for solving system of linear algebraic equations is proposed. The convergence and the optimum parametes of the method are analysed. The rate of convergence is more than two times as large as that of 2PPJmethod and the extrapolation method of J2P. Numerical examples are given to illustrate these results which indicate the superiority of the present method.

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SYMPLECTIC STRUCTURE OF SCHRODINGER EQUATION AND SYMPLECTIC ALGORITHMS FOR QUANTUM MECHANICS Wu Lianao, Jin Xiaogong, Wu Zhaoyan 1995, 12(1): 127-130.  Abstract ( )   PDF (234KB) ( )   The Symplectic algorithms for Hamiltonian mechanics initiated by K.Feng have proved to be a striking success. Since the underlying mathematics of Hamiltonian mechanics is sympledic geometry, the proper discretization should naturally keep the symplodic structure. We show that the Schrödinger equation, after suitable transformation, has a symplectic structure.Therefore the symplectic algorithms for Hamiltonian mechanics can be applied readily toquantum mechanics. As an example the evolution of a nuetron in a rotating magnetic field is calculated. The computational results show that the symplectic scheme is much better than the conventional one, especially for the case of long-term evolution.

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UNIVERSAL FORMULAE FOR SOLVING ELECTROSTATIC POTENTIAL BY SERIES-EXPANSION METHODE Shi Jiangjun, Wang Shijun, Liu Jun, Xiao Xuezheng, Zhang Guanren 1995, 12(1): 131-136.  Abstract ( )   PDF (328KB) ( )   The Taylor expansion approximate method is deScribed with the precision of the second order, which is used to solve the electrostatic Poisson equation in the region with arbitrary shape. The Roberta rule is applied to obtain the potential distribution on the axisymmetric axle of the physical problem. A set of universal formulae is derived to solve the problem with various,boundary, so that the complexity of the problem is avoided and the simulating code can be simplied much more.

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RESEARCH ON THE APPROACH OF QUADRATIC PROGRAMMING IN PLASTICITY Guo Xiaoming, Zhang Roulei 1995, 12(1): 137-143.  Abstract ( )   PDF (375KB) ( )   A new approach to quadratic programming is proposed for the numerical formulas of elastoplastic problems. It has convergent solutions with fewer base exchanges instead of the common iterative methods. And it also gives the gradient formulas of the common yield postulates.