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25 September 2002, Volume 19 Issue 5 Previous Issue    Next Issue

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RAREFIED GAS FLOWS IN MICRO-CHANNELS XIE Chong, FAN Jing, SHEN Ching 2002, 19(5): 377-382.  Abstract ( )   PDF (378KB) ( )   A kinetic approach, named as the information preservation (IP) technique, is used to simulate rarefied gas flows in micro channels under conditions where experimental data are available with about several thousand microns of channel lengths and about 0.135 of the largest Knudsen number at the outlet. Some issues for IP calculation of the long micro channels such as the computational stability and convergence speed are addressed. The calculated stream wise pressure distributions and mass fluxes are in agreement with experimental data.

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NUMERICAL SIMULATION OF MANY-COHERENT STRUCTURES IN THE WALL REGION OF TURBULENT BOUNDARY LAYER LU Chang-gen 2002, 19(5): 383-387.  Abstract ( )   PDF (222KB) ( )   A model of many-coherent structures is proposed using the idea of resonant triads in the theory of hydrodynamic stability.The evolution of the many-coherent structures in the wall region of a turbulent boundary layer is studied by combining the finite difference of high accuracy and the Fourier spectral hybrid method for solving the three dimensional Navier-Stokes equations.Compared with the experimental observations,some numerical results are in reasonable agreement.

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THREE-DIMENSIONAL PARALLEL COMPUTATION OF LASER ABLATIVE RAYLEIGH-TAYLOR INSTABILITY QI Jin, YE Wen-hua 2002, 19(5): 388-392.  Abstract ( )   PDF (310KB) ( )   The set of equations for RT instability of 3D laser ablation is presented and the numerical method is introduced briefly.The parallel technology and the method are developed according to the physical nature and numerical algorithm of the problem that we discuss.The parallel efficiency is 75%.The numerical simulations on 3D multi-mode laser ablative RT instability are also presented,which deepen the knowledge on the evolution of nonlinear 3D ablative RT instability.

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ADAPTIVE DECOUPLING CONTROL SYSTEM FOR MATERIAL BLENDING PROCESS LI Ai-wen, HOU Yu-zhi, ZHANG Cheng-hui 2002, 19(5): 393-396.  Abstract ( )   PDF (182KB) ( )   In cement production,the input/output model used to describe the static characteristics of the raw material mixing system is nonlinear and coupled with interactive variables.A linearizing and decoupling scheme is provided and made the system linearized and decoupled.It is very significant and convenient for analyzing,designing and implementing the control system.An adaptive decoupling control system is designed based on the improved weighted least-square method,the high accuracy and stronger robustness control is realized,the simulation results and practical operation are provided and a comparison is made with the conventional adaptive control system.

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NUMERICAL SIMULATION OF TWO-DIMENSIONAL LASER DRIVEN IMPLOSION WITH SPHERICAL COORDINATES ZHANG Yong-hui, CHEN Guang-nan, LUO Ping-qin, ZHANG Wei-yan 2002, 19(5): 397-402.  Abstract ( )   PDF (260KB) ( )   Numerical simulations of two-dimensional laser driven implosion with spherical coordinates and the relative computational methods are mainly summarized.Features of solving the hydrodynamic equations by the fully conservative implicit difference scheme and solving the thermal conductive equations by the variational method are discussed.Eexamples of relative physical models are presented and effects of the non-symmetry on the laser driven implosive processes are examined.

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SOLVERS FOR THE PRECONDITIONED UNSTEADY INCOMPRESSIBLE NAVIER-STOKES EQUATIONS XUE Ju-kui 2002, 19(5): 403-407.  Abstract ( )   PDF (236KB) ( )   Using the preconditioning technique,the unsteady incompressible Navier-Stokes equations are solved by a dual time stepping method.An implicit line Gauss Seidel relaxation method is designed to advance the equations in pseudotime steps.The convective flux is computed by a flux difference splitting based third order upwind scheme.Based on the numerical simulation for the Lid driven cavity flow at different Reynolds numbers,the convergence characteristics of the preconditioning algorithm for solving incompressible viscous flows is studied numerically.

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NUMERICAL STUDY ON SHOCK-INDUCED MIXING ENHANCEMENT CHEN Jian-qiang, ZHANG Han-xin, GAO Shu-chun 2002, 19(5): 408-412.  Abstract ( )   PDF (561KB) ( )   Based on the third-order ENN scheme, a fourth-or fifth-order WENN scheme is developed by using the weighted function, and then this scheme is applied to a shock-induced mixing flow. Numerical results show that the degree of mixing enhancement can be increased by the shock-induced technique, and that this WENN scheme exhibits a good resolution for the flow field.

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NUMERICAL RESEARCH OF PLASMA EQUILIBRIUM IN TOKAMAK ZHA Xue-jun, ZHU Si-zheng, YU Qing-quan 2002, 19(5): 413-418.  Abstract ( )   PDF (259KB) ( )   To design the HT-7U supper conducting Tokamak, the non-z-symmetric equilibrium code EQ is extended and improved.Moreover, the code is checked by using the reconstructed equilibrium code EFIT from GA in America.

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CALCULATION OF THE ELECTRIC DIPOLE,MAGNETIC DIPOLE AND ELECTRIC QUADRUPOLE OSCILLATOR STRENGTHS OF FeXXI JIN Feng-tao, ZENG Jiao-long, YUAN Jian-min 2002, 19(5): 419-422.  Abstract ( )   PDF (160KB) ( )   Extensive configuration interaction (CI) wave functions are determined using MCHF method and are used to calculate relativistic and non-relativistic energy levels.Agreement is obtained between the calculated and experimental energy levels.Relativistic and non-relativistic electric dipole,magnetic dipole and electric quadrupole oscillator strengths have also been calculated using the CI wave functions.There is a general agreement between the length form and the velocity form.

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LIFETIME STUDIES ON THE ODD-PARITY RYDBERG SERIES OF NEUTRAL LEAD LIANG Liang, ZHOU Chao 2002, 19(5): 423-426.  Abstract ( )   PDF (127KB) ( )   The lifetimes of two Rydberg series of neutral lead are calculated and predicted by means of MQDT,and the predicted 6p6d3/2 3/210 is 59675.61 cm-1.

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PATCHED GRID METHOD AND NUMERICAL SIMULATION OF SUPERSONIC COMPLEX FLOWS ZHANG Yu-dong, JI Chu-qun 2002, 19(5): 427-430.  Abstract ( )   PDF (177KB) ( )   A new method to simulate flows with patched grids is introduced which is based on second-order Godunov method and Euler equations,and conservation across patch boundaries is satisfied.Using the method,the supersonic flows of bind-rocket and complex flows between two objects are simulated.Computation results are in agreement with experimental data,and describe the complex flows rightly such as the crossing and reflex of shocks.This conservation method with patched grids based on second-order Godunov method and Euler equations is one of effective methods for numerical simulation.

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CALCULATING THE THERMODYNAMIC PROPERTIES OF Pd-Au ALLOYS WITH AN ANALYTIC EMBEDDED-ATOM METHOD DENG Hui-qiu, HU Wang-yu, SHU Xiao-lin, ZHAO Li-hua, ZHANG Bang-wei 2002, 19(5): 431-434.  Abstract ( )   PDF (305KB) ( )   An analytic modified embedded-atom model is presented.Using the model,the thermodynamic data,such as the dilute-limit heats of solution,formation enthalpies of disordered solid solutions,surface energies and surface segregation energies for Pd-Au alloy,are calculated.The results are in agreement with the experimental data and calculated data using ab initio theory.

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STABILITY ANALYSIS FOR THE MODEL OF THE ENERGY TRANSPORT IN α-HELIX PROTEINS HUANG Yan-zhao, XIAO Yi, LIN Jia-rui 2002, 19(5): 435-438.  Abstract ( )   PDF (226KB) ( )   A numerical method is used to study the dynamics of a model for the transport of the energy in α-helix proteins proposed by the author.The result shows that there exist static and moving localized modes in the model which may provide an alternative mechanism for the energy transport in α-helix proteins.

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MODIFICATION OF WIDE BAND CORRELATED-k METHOD FOR RADIATIVE CALCULATION NIE Yu-hong, CHEN Hai-geng 2002, 19(5): 439-442.  Abstract ( )   PDF (179KB) ( )   Bandwidth is an important parameter for gas radiative heat transfer calculation, and a parameter for the calculation of the cumulative distribution function in the correlated-k method. Analysis and calculation show that the constant bandwidth is unreasonable in the calculation of the cumulative distribution function. So bandwidth calculated from the modified wide band model is used in the cumulative distribution function calculation. Comparison with the narrow band correlated-k method shows that the present method is more precise than the traditional one.

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NUMERICAL SIMULATION OF NON-FOURIER HEAT CONDUCTION IN THIN LAYER POROUS MATERIAL HEATED BY MICROSECOND LASER PULSE OF HIGH POWER DENSITY JIANG Fang-ming, LIU Deng-ying, ZHOU Jian-hua 2002, 19(5): 443-448.  Abstract ( )   PDF (213KB) ( )   In the traditional heat transfer computation,laser heating is always treated as one kind of special boundary conditions,that is, the second boundary condition,which is not fit for the real condition of laser absorption,especially for the thin layer porous material.Differently from the traditional methods,the laser heating is regarded as an inner thermal source and it is assumed that the intensity of the laser attenuates exponentially with its penetration depth.Since evident non Fourier heat conduction effects may appear in thin layer porous materials heated by the high intensity laser pulse,the hyperbolic non Fourier heat conduction model is used to describe this heat transfer case and the corresponding numerical solution is obtained with the finite difference method.According to the obtained solution,some correlations of the non Fourier effect and the optical property of the heated materials are obtained too.

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COMPUTATION AND ANALYSIS ON FOCUS SHIFT OF LASER CAUSED BY ATMOSPHERIC THERMAL BLOOMING WAN Min, SU Yi 2002, 19(5): 449-452.  Abstract ( )   PDF (171KB) ( )   The focus shift of laser caused by atmospheric thermal blooming is studied. An approximate computational method of thin lens group is used, which is simple and quick. The results are as follows. The effect of atmospheric thermal blooming on high power lasers is related to the initial power, the emitting aperture diameter, the propagation path and the atmospheric absorption coefficient. The focus will shift along the project direction when the absorption coefficient decreases with the increase of the propagation path, while it will shift against the project direction when the absorption coefficient increases with the increase of the propagation path.

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STUDY ON LIGHT COLLECTION AND ITS UNIFORMITY OF LONG LEAD TUNGSTATE CRYSTAL BY MONTE CARLO METHOD RUAN Li-juan, SHAO Ming, XU Tong, YE Shu-wei, ZHANG Zi-ping, CHEN Hong-fang 2002, 19(5): 453-458.  Abstract ( )   PDF (239KB) ( )   In the electromagnetic calorimeter,longitude light collection uniformity of crystal scintillator has certain influence on the energy resolution.Monte Carlo (MC) method (using Litrani software package) is used to simulate the process of light transmission and collection in the long lead tungstate (PbWO4 or PWO) crystal.Discussion focused on the influence of the absorption length and the face management on the light collection is presented.And comparison between anisotropic simulation and isotropic simulation is made.

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INVERSION METHOD OF IMPEDANCE AND THICKNESS OF ONE-LAYERED MEDIUM IN ANNULAR SPACE BETWEEN CASING PIPE AND FORMATION YAO Gui-jin, WANG Ke-xie, QIANG Yu-ming 2002, 19(5): 459-462.  Abstract ( )   PDF (284KB) ( )   Impedance and thickness of one-layered medium in annular space between casing pipe and formation are selected as two inversion parameters.Equations with the tangent function form of phase-shift and equations with the arctangent function form of phase-shift are regarded as the target functions, respectively.Linear least-square inversion method of impedance and thickness is established.Investigation of error functions and inversion results of synthetical data are given.It is found that linear least square inversion method with the arctangent function form of phase-shift is a stable and effective method which can avoid multi-minimal points and the error function only has one minimum value corresponding to the true value of impedance and thickness.Reversion results are not sensitive to the initial value of impedance and thickness.