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25 May 2009, Volume 26 Issue 3 Previous Issue    Next Issue

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Recent Progress in Numerical Methods for Semiconductor Devices YUAN Yirang 2009, 26(3): 317-324.  DOI: 10.3969/j.issn.1001-246X.2009.03.001 Abstract ( )   PDF (417KB) ( )   Numerical methods for transient behavior of semiconductor devices are studied.Mathematical model of a three-dimensional semiconductor device with heat conduction is described by a initial boundary value problem with four quasilinear partial differential equations.Finite difference fractional step method,characteristic finite element alternating direction method,domain decomposition method and theoretical analysis are focused on.

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Linear Discontinuous Finite Element Method for Particle Transport Equation HONG Zhenying, YUAN Guangwei 2009, 26(3): 325-334.  DOI: 10.3969/j.issn.1001-246X.2009.03.002 Abstract ( )   PDF (422KB) ( )   A linear discontinuous spatial finite element scheme for time-dependent particle transport equation is studied.Numerical precision is considered through error norms.Numerical precision of linear discontinues finite element method on edge of each cell is higher than those of exponential method and diamond difference method.It shows that linear discontinuous finite element method is more accurate and differential curve on time about flux is more smooth than that of exponential method and diamond difference.

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Two-dimensional Unstructured Mesh Generation with Constrained Delaunay Triangulations WANG Shengxi, SONG Songhe, ZOU Zhengping 2009, 26(3): 335-348.  DOI: 10.3969/j.issn.1001-246X.2009.03.003 Abstract ( )   PDF (888KB) ( )   Two constrained Delaunay triangulation methods based on local reconstruction and side-swapping method are presented.Their convergence are shown.Appointed fields are renewed by boundary indicating method.It updates field scales by analysis of boundary curvature,axial and mutual smooth gradient of the domain.Based on Spring method,boundary points according to field scales are generated.By sign-area function and probability filer,initial points of field are obtained.Structure of meshes is optimized by Spring-Laplace method,side-swapping and side-collapse methods.The methods can be adaptive refined and made sparse successfully.They can be used to moving mesh and surface mesh generation of reflection surface.

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Conservative Piece-wise Parabolic Advective Remapping Method CHENG Junbo, SHEN Weidong, WANG Shuanghu, JIANG Song, TANG Weijun, YU Ming 2009, 26(3): 349-361.  DOI: 10.3969/j.issn.1001-246X.2009.03.004 Abstract ( )   PDF (834KB) ( )   We develop a conservative piece-wise parabolic advecting remapping method(PPRM).The first part of it is an alternate sweeping average method(ASAM) for improving symmetrization of advecting remapping method.The second part is a piece-wise parabolic distributing function for improving order.We use one-and two-dimesional examples to test order and symmetrization of PPRM.

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Transitional Bridging of Supersonic Aerodynamics XU Shanshu, WU Ziniu 2009, 26(3): 362-370.  DOI: 10.3969/j.issn.1001-246X.2009.03.005 Abstract ( )   PDF (587KB) ( )   We study bridging relations of supersonic aerodynamics in transitional regime by direct simulation Monte Carlo(DSMC).Flows around a cylinder and a blunt double-wedge in a wide range of Mach and Knudsen numbers are simulated.The erf-log bridging relation exhibits good accuracy in supersonic aerodynamics in rarefied transitional regime.It is helpful in predicting low supersonic aerodynamic coefficients of sub-orbital spacecrafts by bridging relations.

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Spectrum Characteristic of Dissipative Compact Schemes and Application to Couette Flow MAO Meiliang, DENG Xiaogang, LI Song 2009, 26(3): 371-377.  DOI: 10.3969/j.issn.1001-246X.2009.03.006 Abstract ( )   PDF (306KB) ( )   Spectrum characteristic of linear dissipative compact schemes and corresponding fully-discrete forms based on m-order Runge-Kutta algorithm are investigated by Fourier analysis.A 5-th order scheme is empolyed to study propagation of a classical high-frequency wave and eigen-value problem of a supersonic plane Couette flow as well as its boundary value stability.Numerical results demonstrate favorable spectrum characteristic of dissipative compact schemes.

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Adaptive Upwind FEM for Drag-coefficient of Flow Around a Cylinder MA Yan, HU Jianwei 2009, 26(3): 378-388.  DOI: 10.3969/j.issn.1001-246X.2009.03.007 Abstract ( )   PDF (431KB) ( )   We study adaptive computation of drag-coefficient of flow around a cylinder. We adopt upwind finite element schemes for two-dimensional stationary viscous incompressible Navier-Stokes equations, derive weighted posteriori error estimation for drag-coefficient by introducing a dual problem, and implement adaptive mesh refinement. Numerical examples show feasibility of the scheme and robust performance of estimators.

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Lattice Boltzmann Simulation of Gas Transfusion in Compact Porous Media WANG Hualong, CHAI Zhenhua, GUO Zhaoli 2009, 26(3): 389-395.  DOI: 10.3969/j.issn.1001-246X.2009.03.008 Abstract ( )   PDF (413KB) ( )   In order to describe microscale flows in compact porous media with lattice Boltzmann method,we extend a model proposed by Guo et al designed for micro gas flows in a single channel to porous medium.The extended model is used to simulate two simplified porous structures.Dependence of permeability on Knudsen number and averaged pressure is studied and analyzed theoretically.Simulated results are consistent with experimental results reported.It shows that the lattice Boltzmann method can serve as a promising tool for simulating gas flows through a compact porous medium.

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Coupled Finite Element/Wave Based Method for Acoustic Analysis PENG Weicai, HE Zeng, LI Peng 2009, 26(3): 396-402.  DOI: 10.3969/j.issn.1001-246X.2009.03.009 Abstract ( )   PDF (360KB) ( )   We discuss briefly theoretical background of FEM and WBM and mathematical description of coupled FE/WB approach.FEM and WBM show advantages in wide application and high convergence rate,respectively.A coupling of predication tools benefits from advantages of both.The basic idea is to replace parts in the finite element mode,which have simple geometrical shapes,by much smaller wave models.It results in a coupled model with less degree of freedom.This allows a further refinement of model,which leads to an improved accuracy at higher frequencies and reduces number of degree of freedom by modal reduction techniques.Numerical example indicates that the proposed method has potential in covering a range with mid-frequency.

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Numerical Study on Friction Between Solid Body and Granular Material SHENG Xiaowei, LUO Zhiyuan, CAI Qingdong 2009, 26(3): 403-408.  DOI: 10.3969/j.issn.1001-246X.2009.03.010 Abstract ( )   PDF (359KB) ( )   A numerical study on shearing movement of granular system with a dragging solid body on top is presented.It focuses on friction between body and particles.It shows that friction coefficient varies with dragging velocity.This behavior,totally different from interaction between two solid bodies,implies complexity of granular system.

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Convolution Semi-analytical Differential Quadrature Method for Structural Dynamic Response PENG Jianshe, LIU Yan, YANG Jie 2009, 26(3): 409-414.  DOI: 10.3969/j.issn.1001-246X.2009.03.011 Abstract ( )   PDF (261KB) ( )   A convolution type semi-analytical approach is proposed for structural dynamic response.With convolution original governing equation is transformed into a complete initial-value problem with initial conditions.The equation is mathematically equivalent to Gutrin's variational principle while it involves no functional and complicated calculation in variational principle.The new governing equation is solved by differential quadrature method in space domain and analytical series in time domain to obtain dynamic response.Dynamic response of a beam is studied.It is shown that the proposed method is accurate and efficient.

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Efficient FDTD Algorithm for Anisotropic Magnetized Plasma ZHONG Shuangying, LIU Song 2009, 26(3): 415-421.  DOI: 10.3969/j.issn.1001-246X.2009.03.012 Abstract ( )   PDF (315KB) ( )   A novel finite-difference time-domain(FDTD) method for anisotropic magnetized plasma is derived with piecewise linear approximation and recursive convolutions of current density J and electric field E.J and E employ a piecewise linear approximation,respectively.High efficiency and accuracy of the method are confirmed with reflection and transmission coefficients through a collisional magnetized plasma slab with propagation direction parallel to biasing field.Compared with frequency domain analytic results,good agreement is observed.The proposed method shows higher efficiency and accuracy than current density convolution(JEC-FDTD) and piecewise linear current density recursive convolution(PLCDRC-FDTD) approaches.In addition,Faraday rotation effect is demonstrated.

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Optical Wave Transmission Through Slightly Gaussian Rough Surface of Layered Medium REN Xincheng, GUO Lixin 2009, 26(3): 422-430.  DOI: 10.3969/j.issn.1001-246X.2009.03.013 Abstract ( )   PDF (434KB) ( )   Optical wave transmission through slightly rough surface of three layered medium is studied. Transmission coefficients with different polarization are derived using a small perturbation method. A Gaussian rough surface is used to describe rough surface of layered medium. Influence of permittivity of layered medium, mean layer thickness of intermediate medium, roughness surface parameters and incident wavelength on the transmission coefficient of HH polarization is diacussed.

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Main-variable Correction of Energy Balance Equations in Zone Method HU Zhangmao, LI Benwen, CHEN Haigeng 2009, 26(3): 431-436.  DOI: 10.3969/j.issn.1001-246X.2009.03.014 Abstract ( )   PDF (306KB) ( )   With analysis on physical characteristics of heat transfer in zone method,mathematical-physical characteristics are considered for main-variable correction in zone method.Detailed principle and solution procedure of main-variable correction method is introduced. It is compared with other methods with a typical example.It shows that the main-variable correction method is more reliable and applicable.

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Arbitrary Directional Radiative Intensity by Source Six Flux Method in Cylindrical Coordinate RUAN Liming, QI Hong, WANG Shenggang, ZHAO Hui, LI Baocheng 2009, 26(3): 437-443.  DOI: 10.3969/j.issn.1001-246X.2009.03.015 Abstract ( )   PDF (300KB) ( )   Based on traditional flux method,a source six flux(SSF) model in cylindrical coordinate is proposed for arbitrary directional radiative intensity.Basic theory and numerical procedure of SSF model are presented in detail.Compared with directional radiative intensity by two flux method(TFM) and Backward Monte Carlo(BMC) method in cylindrical media,results of SSF method agree well with those of BMC.However,SSF method is more efficient than BMC,thus SSF method is more suitable in solving directional radiative intensity problems.

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Multi-atom Molecular Ions in Intense Laser Pulse and Enhancement of High-order Harmonic Generation LI Nana, LIU Xueshen 2009, 26(3): 444-448.  DOI: 10.3969/j.issn.1001-246X.2009.03.016 Abstract ( )   PDF (265KB) ( )   Interaction of multi-atom molecular ions with intense laser pulse is studied. High-order harmonic generation plateau is extended and conversion efficiency is enhanced.Physical mechanism of plateau extension is explained with classical theory.

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Scaling of Time-fractional Edwards-Wilkinson Equation XIA Hui, TANG Gang, HAN Kui, HAO Dapeng, XUN Zhipeng 2009, 26(3): 449-453.  DOI: 10.3969/j.issn.1001-246X.2009.03.017 Abstract ( )   PDF (232KB) ( )   Scaling of time-fractional Edwards-Wilkinson (TFEW) equation in 1+1 dimensions is investigated with numerical simulation and scaling analysis. It is found that the growth exponents obtained by numerical solution based on Caputo-type fractional derivative are consistent with scaling analysis.

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Sphere Assembly Model and Relaxation Algorithm for Packing of Non-spherical Particles LI Shuixiang, ZHAO Jian 2009, 26(3): 454-460.  DOI: 10.3969/j.issn.1001-246X.2009.03.018 Abstract ( )   PDF (492KB) ( )   We present an improved relaxation algorithm involving rotation of non-spherical particles.In a sphere assembly model,the algorithm simulates random packing of non-spherical particle of any shape as well as particle mixture consisted of particles with different shapes.In the sphere assembly model,particle shape is described with contour of a number of spheres.Contacts between non-spherical particles are treated as contacts of spheres.By introducing torque and rotation of non-spherical particles,the algorithm overcomes self-lock problem,and random close packing is achieved.Packing densities obtained are coincident with numerical and experimental results in literatures.

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Escape from Metastable Potentials in a CTRW-Metropolis Model LIN Fang, BAO Jingdong 2009, 26(3): 461-466.  DOI: 10.3969/j.issn.1001-246X.2009.03.019 Abstract ( )   PDF (303KB) ( )   A numerical method based on continuous time random walk(CTRW) theory is developed for anomalous diffusion.Probability density functions for both jump distance and residence time in CTRW model are determined.Metropolis sampling method is improved in the case of nonlinear potentials.Escape rate in metastable potential is investigated.It shows that stationary escape rate is non-monotonic as anomalous index α increases.A maximum of escape rate exists in the case of super-diffusion and a cancellation phenomenon in barrier region is found.

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Numerical Simulation on Orbital Stability of RKBOs WU Xiaomei, NIE Qingxiang 2009, 26(3): 467-474.  DOI: 10.3969/j.issn.1001-246X.2009.03.020 Abstract ( )   PDF (419KB) ( )   Orbital evolution of RKBOs is simulated by using reliable orbital elements over a timescale of 108 year.It shows that their orbits are relatively stable in resonant regions.Stability depends on initial orbital semi-major axis,eccentricities and inclinations of these resonant bodies.According to dynamical behavior of orbital semi-major axis,eccentricity and inclination,RKBOs are classified into regular or chaotic orbits.