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25 January 2003, Volume 20 Issue 1 Previous Issue    Next Issue

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Gas Kinetic HPF Parallel Algorithm Using Boltzmann Model Eguation LI Zhi-hui, ZHANG Han-xin, FU Song 2003, 20(1): 1-8.  Abstract ( )   PDF (273KB) ( )   Supported by the Science Foundation of China Academy of Engineering Physics under the Grant No.20010660

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Implicit Gridless Method for Euler Eguations CHEN Hong-guan 2003, 20(1): 9-13.  Abstract ( )   PDF (170KB) ( )   An implicit gridless method is investigated for the Euler equations. Clouds of points distributed all over the computational domain are adopted instead of common mesh generation. The spatial derivatives are directly approximated by using local least-square curve fits in each cloud of points. An upwind method using Roe's approximate Riemann solver is used for the estimation of the inviscid flux. The linear system of the resulting backward Euler temporal discretization is computed by using LU-SGS algorithm. The numerical implementations of the method are presented for transonic flows over 2-D airfoils, which reveals the flexibility of using clouds of points for complicated aerodynamic shapes.

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Explanation of Strain Softening and Numerical Modeling to the Failure Process of Laminated Composite Material CHEN Yong-giang, ZHENG Xiao-ping, YAO Zhen-han 2003, 20(1): 14-20.  Abstract ( )   PDF (222KB) ( )   The solid mechanical behaviors and the fracture process of laminated composite material with non-uniform material properties are simulated by the finite element method.All layers possess non-homogeneity, which is described by proper statistical distributions.In the 3-D discretization,the non-uniformity consists in a variety of elastic constants in each element.When the displacement or loading increases gradually, discretized element fails one by one randomly and the equivalent curve of strain vs. stress reflects complex non-linearity.Under the given conditions, the variation of strain and stress field and the fracture process are obtained through numerical simulations in which different elements fail in a random sequence until the specimen is fractured totally as the displacement or loading increases gradually. In the test runs, the material consists of about 14 to 15 layers. Thousands of elements are used in test examples presented in this paper. The relations between equivalent stresses and strain, got by simulation, is in qualitative agreement with test results in [11,12], especially for the phenomena of strain softening. Our investigations can serve as an explanation of strain softening of heterogeneous material.

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Simulation of Electron Beam Tracing in the X-ray Source with Microbeam WANG Kai-ge, NIU Han-ben, ZHOU Yan 2003, 20(1): 21-24.  Abstract ( )   PDF (143KB) ( )   The focal dimension of the X-ray source with microbeam is in proportion to the size of the e-beam focused on the target surface. The finite difference method is utilized to calculate the distribution of the electrical-field intensity. The track of the electron-beam is traced by using the Runge-Kutta method within the whole symmetrical system. As a result, the diameter of the electron beam focus is 0.6-1.0μm while the total high brightness emission of the LaB6 crystal cathode is 0.06-0.3mA.

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Theoretical Model of Drag Between Gas and Solid Phase in Circulating Fluidized Bed XIAO Hai-tao, OI Hai-ying, YOU Chang-fu, XU Xu-chang 2003, 20(1): 25-30.  Abstract ( )   PDF (175KB) ( )   Drag force is a key parameter in the analysis of gas-solid flow,especially in dense vertical flows,and is important in numerical simulation of the gas-solid flow.To describe the cluster phenomena and their effects on drag force, a new model of gas-solid drag force is developed under the consideration of cluster effects using the energy minimization concept.Compared with the existing drag models,the new one can reasonably describe the interaction between gas and particle phase,and avoid the error caused by the inaccurate experimental coefficients.It can improve the accuracy of the simulation of dense gas-solid two-phase flow greatly.

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Controlling Chaos by the Constant Periodic Pulse Method in Two Coupled Standard Maps XU Hai-bo, WANG Guang-rui, CHEN Shi-gang 2003, 20(1): 31-36.  Abstract ( )   PDF (244KB) ( )   A constant periodic pulse method for controlling chaos which makes the stable segment of the chaotic orbit form a closed orbit by acting periodic pulses on the system variables is proposed on the basis of the finite time Lyapunov exponents. This method is applied to a high dimensional system with two coupled standard maps. In addition to the results obtained in the low dimensional systems, the stabilized periodic orbit whose period is a multiple of the pulse interval is also found. This is one of the characters of the periodic pulse method. This method is robust under the presence of weak external noise.

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Numerical Calculation of Sensitivity Coefficients to the Porosity LIU Fu-ping, YANG Chang-chun 2003, 20(1): 37-43.  Abstract ( )   PDF (214KB) ( )   The sensitivity coefficients to the porosity are derived from the initial boundary value problems for the fluid equations in porous media by the Green's Reciprocity Principle. The sensitivity coefficients of wellbore pressure to the porosity are obtained by the Peaceman's equation and calculated with a numerical method for the 3D transient anisotropic fluid equation in porous media and verified with the direct method. The computed results are in agreement with those obtained with the direct method.

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Application of a Simple Calculation Method of Ion Optical System to Reflectron Time-of-flight Mass Spectrometer HU Zhan, JIN Ming-xing, LIU Hang, ZHANG Lin-iin, DING Da-jun 2003, 20(1): 44-50.  Abstract ( )   PDF (224KB) ( )   A simple method to calculate electrostatic fields of ion optical system and trajectories of ions in the field is discussed.The optimization methods to save disk space and accelerate the calculation process are given under condition of maintaining the calculation precision.A feasible method for searching the over-relaxation factor is present.The calculation method is applied to the calculation of a design of gridless high-resolution reflectron time-of-flight mass spectrometer.The results of the distribution of electrostatic fields,the ion trajectories and the best conditions of the fields are present.The system is adjusted to its fairly good working condition based upon these results,and mass spectra with much higher resolution are observed.

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Properties of Energy Deposition and Thermal Shock Wave in Material Radiated by Pulsed Electron Beam PENG Chang-xian, LIN Peng, TANG Yu-zhi 2003, 20(1): 51-58.  Abstract ( )   PDF (264KB) ( )   Three methods——analysis method,moment method and Monte-Carlo method——are used to calculate the energy deposition of electron beam in LY-12AL,and the results agree well with each other.According to these results and the one dimension elastic-plastic fluid dynamics model, thermal shock wave resulted in the high energy deposition in LY-12AL is calculated. Peaks of the thermal shock wave accords with the results from experiments.

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PDF Simulation of a Confined Turbulent Jet Diffusion Flame WANG Hai-feng, CHEN Yi-liang, LI Yi 2003, 20(1): 59-64.  Abstract ( )   PDF (219KB) ( )   A confined turbulent jet diffusion flame is studied using the probability density function(PDF) approach together with the k-ε two-equation model. The effect of solid wall and pressure gradient on the velocity and scalar is mainly concerned with. Then two confined turbulent combustion fields with different dimensions are simulated, of which the fluid structure, flame structure and flame shape are studied. In the end, the result is analyzed and conclusions are made.

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Multigroup Monte Carlo Calculation Coupled of Transport and Burnup DENG Li, XIE Zhong-sheng, LI Shu 2003, 20(1): 65-70.  Abstract ( )   PDF (249KB) ( )   A 3-D multigroup P3 approximation Monte Carlo code MCMG-BURN is developed by coupling the neutron transport and burnup.MCMG-BURN code is based on the continuous-energy cross-section Monte Carlo code MCNP and the lattice homogeneous code WIMS.It uses the multigroup cross-section libraries to simulate the critical test reactors and HFETR(High Flux Engineering Test Reactor).The agreement results with the MCNP results and experiments are achieved.The MCMG-BURN code is at almost the same precision with the MCNP code while requiring considerably less computing time.

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Numerical Simulation and Analyses on Actively Detecting Nuclear Warheads with Neutron Sources WU Jun, LIU Cheng-an, HU Si-de, ZHANG Ben-ai, TIAN Dong-feng 2003, 20(1): 71-75.  Abstract ( )   PDF (157KB) ( )   Neutron transport numerical simulation of different energy of neutron sources is performed in hypothetical nuclear warhead models.Three methods of actively warhead detection are analyzed and the feasibility of actively detecting warheads with three types of neutron sources is studied.With 14.1 MeV pulse neutron source,distribution of delayed neutron flow with time is studied.Results show that the warheads can be detected without exposing the sensitive information of nuclear weapons by detecting the delayed neutrons.

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Preconditioners to Three-dimensional Problems Based on Local Block Decomposition WU Jian-ping, LI Xiao-mei 2003, 20(1): 76-80.  Abstract ( )   PDF (177KB) ( )   A preconditioner of incomplete factorization types and a modified version are provided for the 3-D problems with the help of local block decomposition of a block tridiagonal matrix recursively. Then the existence of both preconditioners is focused on. For the seven point matrix discreted from the 3-D Laplace operator with the seven point difference technique, the actual condition numbers are computed and the results show that for the non-modified preconditioner, the condition number is proportional to N2／3, where N is the order of the matrix. For the modified version, the condition number is proportional to the cube root of the order of the matrix thereafter. Finally, highly efficient implementation is considered and several effective experiments are done for these preconditioners on personal computers with main frequency of 550MHz and memory of 256M.

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Spin-forbidden Transitions for Mg-like Ions(Z=14~103) YI You-gen, ZHENG Zhi-jian, TANG Yong-jian, ZHU Zheng-he 2003, 20(1): 81-87.  Abstract ( )   PDF (196KB) ( )   A fully relativistic multiconfiguration Dirac-Fock method with Breit and QED corrections is used to calculate the spin-forbidden 3s2 1S0-3s3p3P1(Z=14~103) transition energy level separations and transition probabilities for the Mg-like ions. In the calculation, significant Breit and QED corrections are considered and the results are in agreement with recent experimental data and other theoretical values. The results show that the spin-forbidden transition probabilities are in correspondence with those of E1 transitions and shouldn't be ignored in the laser plasma with high temperature created in ICF and MCF fusion.

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Geometric Configuration and Properties of Methane Series LU Chun-hai, CHEN Wen-kai, LIAO Jun-sheng, WANG Huai-sheng, WANG Xiao-iin, SUN Yin 2003, 20(1): 88-90.  Abstract ( )   PDF (90KB) ( )   Ab initio restricted Hatree-Fock(RHF) calculations, Moller-Plesset correction calculations of the correlation energy, and the density functional theoretical calculations using B3' exchange and Lee-Yang-Parr's correlation functional(B3LYP) with 6-31G** basic set are compared by optimizing the equilibrium structure of CD4 and CH4 and studying their fundamental vibration frequencies. The results are better than HF's, which are obtained by MP2, DFT, MP4 methods. But MP4 method needs too much CPU time. B3LYP is the best choice. The range of relative errors is from 2.0% to 10.4% between the calculated fundamental vibration frequencies and the observed ones.

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Bifurcation Diagrams and Poincar Maps of Current-oscillations in Superlattices ZHANG Oi-yi, TIAN Oiang 2003, 20(1): 91-94.  Abstract ( )   PDF (233KB) ( )   The transportation behavior of electric-field domains in a n-doped weakly coupled GaAs/AlAs superlattices under dc+ac voltage bias is studied numerically within a discrete drift model.Fixing the ac driving frequency at the golden mean ratio,the quasiperiodicity、requency-locking and chaos of the current for different ac amplitude are analyzed.