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25 March 2012, Volume 29 Issue 2 Previous Issue    Next Issue

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Implementation of Essential Boundary Condition in Mesh-less Method Using Master-Slave Relation ZHENG Zijun, CHEN Yongqiang, CHEN Pu 2012, 29(2): 159-165.  Abstract ( )   PDF (404KB) ( )   To enforce accurate displacement constraints,essential boundary conditions and interface continuity conditions in mesh-less method are treated as Multi-Point Constraints (MPC) of displacement,which are illustrated by using SPH (Smoothed Particle Hydrodynamics) method incorporated with algebraic master-slave relations.An example of linear elastic problem of representative volume element in matrix-inclusion composite is presented.Numerical tests show that the proposed algebraic master-slave method leads to higher accuracy and wider application than the penalty function method.

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RKDG Finite Element Method for Two-dimensional Gas Dynamic Equations in Lagrangian Coordinate ZHAO Guozhong, YU Xijun, ZHANG Rongpei 2012, 29(2): 166-174.  Abstract ( )   PDF (9373KB) ( )   We construct a Runge-Kutta discontinuous Galerkin (RKDG) finite element method for two-dimensional compressible gas dynamic equations in Lagrangian coordinate.The equations for fluid dynamics and geometry conservation laws are solved simultaneously.All calculations can be done on fixed meshes.Information of grid velocities are not needed in calculation.Several numerical examples are used to evaluate efficiency and reliability of the scheme.It shows that the algorithm works well.

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A Direct Discontinuous Galerkin Method for Nonlinear Schrödinger Equation ZHANG Rongpei, YU Xijun, ZHAO Guozhong 2012, 29(2): 175-182.  Abstract ( )   PDF (7764KB) ( )   We discuss numerical simulation of one-and two-dimensional nonlinear Schrödinger (NLS) equations (NLS).With numerical flux of diffusive generalized Riemann problem,a direct discontinuous Galerkin (DDG) method is proposed.L2 stability of the DDG scheme is proved and it is shown that it is a conservative numerical scheme.The one-dimensional case indicates that the DDG scheme simulates various kinds of soliton propagations and it has excellent long-time numerical behaviors.Two-dimensional numerical results demonstrate that the method has high accuracy and is capable of capturing strong gradients.

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Nodal Integration Element-free Galerkin Method with Upwind Shifted Integration Nodes WANG Xiaodong, OUYANG Jie, WANG Yulong, JIANG Tao 2012, 29(2): 183-190.  Abstract ( )   PDF (5434KB) ( )   A stable and efficient element-free Galerkin method is proposed for steady convection-diffusion problems.In the method integrations are computed with a local Taylor expansion nodal integral technique.According to convection-dominated degree,integration nodes are adaptively shifted opposite to the streamline direction.Compared with conventional element-free Galerkin method with stabilization,the method exhibits better stability and higher efficiency in solving convection-dominated convection-diffusion problems.It is a pure meshfree method,which is independent of background integral.Moreover,the method is easy to be implemented.

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Radial Basis Function Interpolation in Moving Mesh Technique LIN Yanzhong, CHEN Bing, XU Xu 2012, 29(2): 191-197.  Abstract ( )   PDF (6186KB) ( )   A spring stream method used for unstructured grid and a transfinite interpolation method used for structured grid are discussed.A method using radial basis function is proposed,which resolves moving mesh problem without any grid-connectivity information.Corresponding mesh numerical program is developed.Rotation of a two-dimensional rhombic aerofoil and deformation of a three-dimensional F104 aerofoil are taken as examples to show effects of function and radius on mesh quality and numerical efficiency.Results are compared with mesh-deformation using lineal spring method.It validats availability of the RBF method.We concluded that the RBF method is remarked with simple data structure,high numerical efficiency and strong adapting ability for large mesh deformation.It could be applied to CFD dynamic mesh problems.

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A Parallel Algorithm with Interface Prediction and Correction for Time-dependent Transport Equation in 2D Cylindrical Geometry WEI Junxia, YUAN Guangwei, YANG Shulin, SHEN Weidong 2012, 29(2): 198-204.  Abstract ( )   PDF (393KB) ( )   For discontinuous finite element method of time-dependent neutron transport equations in 2D cylindrical geometry,a parallel algorithm with interface prediction and correction is designed.Numerical experiments show that the parallel algorithm with explicit prediction and implicit correction has good precision,parallelism and simplicity.Compared with parallel algorithm based on implicit scheme,the new parallel algorithm has higher parallel efficiency with accuracy-preserving.Especially,it achieves super-linear speedup on hundreds of processors for large-scale problems.

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Composition Computation of Radiation Hydrodynamics and Particle Transport Based on JASMIN REN Jian, WEI Junxia, CAO Xiaolin 2012, 29(2): 205-212.  Abstract ( )   PDF (476KB) ( )   With support of Federation Computing in JASMIN,two serial codes named radiation hydrodynamics code RH2D and particle transport code Sn2D as Federal members are concatenated to an integrated program RHSn2D,which uses efficiently thousands of processors to simulate a multiphysics composition system.Federal members of RHSn2D have mesh patches and parallel algorithms respectively,encapsulating parallel communication between them based on JASMIN.For a typical model discretized by 90 720 meshes,100 patches in RH2D,2 835 patches in Sn2D,48 directions and 16 energy groups,it shows that the integrated program RHSn2D achieves parallel efficiency of 36% with 1 024 processors.

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Computation of Arc Discharge Plasma Incident Shock CHENG Yufeng, NIE Wansheng 2012, 29(2): 213-220.  Abstract ( )   PDF (500KB) ( )   A mechanism model for arc discharge plasma is analyzed.An exploding wires diathermanous model for of arc discharge plasma incident shock was found.It shows that thermal mechanism dominating the shock wave control process is arc discharge plasma aerodynamic actuation.Effect of arc discharge plasma to supersonic flow field is a conform of protuberance with a bevel.The theoretical analysis is suit only for small y.The exploding wires diathermanous model is good for arc discharge plasma incident shock as diathermanous power rate is 10% of discharge power.The plasma wedge angle and incident shock angle decrease as total pressure and flow velocity increased,and they increase as average power of discharge increased.These variations are obvious at low total pressures,low flow velocities and low average powers.

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PIC Simulation of Plasma Ion Implantation into Inner Surface of Trapezoid Tube Using MATLAB PEI Xianjun, GONG Chunzhi, WANG Zhijian, TIAN Xiubo, YANG Shiqin 2012, 29(2): 221-226.  Abstract ( )   PDF (4038KB) ( )   Numerical simulation on plasma ion implantation of a trapezoid tube is conducted in a MATLAB based Particle-in-cell model.It shows that "anodic-sheath" appears around internal electrode,where there is no ion.Some ions gather at the edge of "anodic-sheath" leading to a high-ion-density ring.It makes an m-shaped dose distribution on upside wall and downside wall of the tube.Due to asymmetry of the trapezoid tube,"anodic-sheath" expands faster toward long-wall of the tube.Implantation energy is relatively low at initial stage and becomes higher with time.This is attributed to the position of ions in the tube before they are implanted into the tube wall.The tube configuration determines sheath shape and final distribution of implantation dose and energy.

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A Comparison of Radio-frequency and Direc Current Discharge in Nitrogen with PIC/MC Model ZHANG Lianzhu, ZHAO Haitao, SUN Qian, YAO Fubao, YANG Wei 2012, 29(2): 227-233.  Abstract ( )   PDF (392KB) ( )   A PIC/MC model is developed for electrons,atomic ions N+ and molecular ions N2+ in a capacitively coupled rf glow discharge.Modeling results are compared with those in a dc glow discharge at similar conditions.It reveals that the mean densities of particles(e,N2+,N+) in rf discharge are nearly ten times greater than those in dc discharge,the mean energy near a rf electrode is about three times less than that near a cathode in dc discharge;the ions N+ have higher energy near two electrodes,the ions N2+ have higher density,and the density of N2+ is about six times the density of N+.The simulated electron energy probability distributions agree with measured results.

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Lattice Boltzmann Method for Flow field in a Constant Area Isolator of Scramjet HE Hong, LI Huixiong, FENG Yongchang 2012, 29(2): 234-238.  Abstract ( )   PDF (2545KB) ( )   Flowfield in a constant area isolator is numerically simulated with coupled double distribution function lattice Boltzmann method(LBM).Numerical results reflect general structure of flow field which means that LBM is a potential computational fluid dynamics method.

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Mechanical Analysis of Radon Transport in Vicinity of an Underground Tunnel NIU Guanyi, CHEN Jianjie, WANG Jun 2012, 29(2): 239-244.  Abstract ( )   PDF (302KB) ( )   A radial symmetrical model of radon transport in vicinity of an underground tunnel is developed with continuum mechanics theory.Distribution of radon concentration in the vicinity of tunnel is analyzed under the assumption that only diffusion and permeation are considered.Analytic solutions are obtained.A rock mass range affecting the radon concentration in the tunnel is defined as effective transport distance.Effective transport distance as functions of effective porosity and velocity are given.Expressions of radon exhalation rate on tunnel wall are shown.

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Laplace Transform Finite Difference Method for Well-test Problem with One-dimensional Seepage Flow LIU Hong, WANG Xinhai, ZHANG Fuxiang, NIU Xinnian 2012, 29(2): 245-249.  Abstract ( )   PDF (235KB) ( )   With finite difference method and Laplace transform,a Laplace transform difference method for well-test problem with one-dimensional seepage flow is proposed.Firstly,time variable is eliminated by Laplace transform.Then the mathematics model is solved with finite difference method.Finally the wellbore pressure or production is obtained with numerical inversion algorithm.A comparison with finite difference method solution and analytic solution shows that the calculating error of Laplace transform difference method is smaller than that of finite difference method,though it consumes more time in each step.Laplace transform difference method has advantages in well-test application since any moment simulation does not rely on other moment result and space grid.

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Solitary Wave Solutions of Modified Coupled KdV Equation and Their Stability SHI Yuren, ZHOU Zhigang, ZHANG Juan, YANG Hongjuan, DUAN Wenshan 2012, 29(2): 250-256.  Abstract ( )   PDF (325KB) ( )   With function expansion method,we obtain several types of solitary wave solutions of modified coupled KdV (cKdV) equations,including kink-bell-like soliton,double kinks soliton,double bells soliton and double kinks-double bells soliton.These solitary wave solutions are reduced to kink or bell-like solitons solution under different limitations.We also investigate numerically stability of solitary wave solutions.It indicates that the system of modified cKdV equations has both stable solitary wave solutions and unstable solitary wave solutions.

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Analytical Solution of Contact Melting Around a Horizontal Cylindrical Heat Source with Non-isothermal Wall ZHAO Yuansong, LIANG Weihua, CHEN Wenzhen 2012, 29(2): 257-262.  Abstract ( )   PDF (292KB) ( )   Contact melting around a heat source with non-isothermal wall is investigated.A theoretical model for contact melting around a horizontal cylindrical heat source,whose wall temperature varied with angle,is established.Condition of heat transfer and motion of the liquid molten in contact region are studied.Control equations of melting are established with Nusslet's liquid film theory.And analytical solution of melting velocity is obtained theoretically.It includes result published in literature about melting around the heat source with constant temperature.Melting velocity,thickness and pressure distribution of molten layer under different melting conditions are studied.Effects of temperature distribution on melting are obtained.

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Arc-length Method for Nonlinear Buckling Analysis of Tubular in Deviated Wells TAN Meilan, WU Guoyu 2012, 29(2): 263-270.  Abstract ( )   PDF (410KB) ( )   Based on differential quadrature (DQ) element of tubular with a radial constraint,an arc-length incremental iteration method is established.It is used for the post-buckling analysis of tubular in a deviated well bottom.Detailed iteration steps and method of determining initial values of iteration are given.Iterative calculations are carried out for nonlinear buckling of tubular under various end lateral constraints in deviated wells.Numerical results are compared with approximate analytical solution,experimental data and numerical results obtained with purely incremental methods in literature.It shows that the developed method overcomes difficulties encountered in finite element method in dealing with tubular weight.At the same time,it is capable to adjust automatically increment step and trace complex path in the space load/displacement of tubular nonlinear post-buckling.The method is of high efficiency,good convergence,easy to implement.It can be used to analyze nonlinear buckling of tubular in deviated wells.

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A Z-transform Implementation of Higher-order Perfectly Matched Layer FENG Naixing, LI Jianxiong 2012, 29(2): 271-276.  Abstract ( )   PDF (291KB) ( )   With stretched coordinate perfectly matched layer (SC-PML) formulations and Z-transform method,an efficient and unsplit-field implementation of higher-order PML scheme with more than one pole is proposed which truncates finite-difference time-domain (FDTD) lattices.The higher-order PML has advantages of both conventional PML and complex frequency shifted PML (CFS-PML) in terms of absorbing performances.A numerical validation of the proposed formulations is provided through a 2D TE-polarized electromagnetic wave interaction with an infinitely long perfectly electric conductor (PEC) sheet with finite width.It is shown that the proposed PML formulations with higher-order scheme are efficient in terms of attenuating low-frequency propagating waves and evanescent waves and reducing late-time reflections.It has better absorbing performances than conventional SC-PML and convolutional PML (CPML) with CFS scheme.

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Structural,Electronic,and Magnetic Properties of Mn-doped ZnS (110) Surfaces:First-principles Study SONG Dewang, NIU Yuan, XIAO Liou, LI Dan 2012, 29(2): 277-284.  Abstract ( )   PDF (6406KB) ( )   Structural,electronic,and magnetic properties of Mn-doped ZnS (110) surfaces are investigated with first-principles method.Geometric parameters,formation energies,magnetic moments,density of states,and electron charge densities are studied.It shows that the lowest formation energy is as a Mn atom doped into the second layer,which indicates that this layer is more stable for Mn-doping.For bidoped case,the most stable configuration is an antiferromagnetic state of two Mn atoms.Total magnetic moments is equal to that of a free Mn atom.The local magnetic moment of Mn atom depends on a hybridization of Mn 3d state and its neighboring S 3p state,that is to say,magnetic moment changes as environment of S atoms alters.Furthermore,electron charge density shows that intensity of covalent bond between Mn and S atoms is greater than that between Zn and S atoms.

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Boundary Effects in Magnetization Reversal of Micro-square Ferromagnetic Thin Films LI Mei, SU Yuanchang, HU Jingguo 2012, 29(2): 285-290.  Abstract ( )   PDF (385KB) ( )   Boundary effects in magnetization reversal induced by dipole-dipole interaction in micro-square ferromagnetic films are studied by means of spin dynamics simulation.Fixing strength of dipole-dipole interaction,coercive force is calculated as functions of strength of uniaxial anisotropy and magnetization angle θ (the angle between applied field and easy axis).Typical hysteresis loops and spin configurations are given.It shows that shape of hysteresis loop and magnitude of coercive force are determined by a competition between boundary pinning effect and uniaxial anisotropic field,which leads to different coercivity mechanism under different θ.An effective five-magnetic-domain model is proposed to describe spin configurations of square ferromagnetic thin films.The model shows conveniently geometric and physical properties of square ferromagnetic thin films with uniaxial anisotropy as well as its magnetization reversal process.

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MAEAM Study on Structure Stability and Phonon Spectrum of FCC Metals JIN Hakson, ZHAO Yue, DU An 2012, 29(2): 291-296.  Abstract ( )   PDF (282KB) ( )   With a modified analytical embedded atom method (MAEAM),structure stability and phonon spectra of fcc metals are calculated.A pair-potential function was proposed considering farther neighbor atomic interaction.A new truncated function and an enhanced smooth connection condition are used for the cutoff of pair potential.Model parameters are determined through fitting mono-vacancy migration energy,cohesion energy,three independent elastic constants and an equilibrium condition.Under same volume,we calculated binding energies of various metal structures.It shows that fcc structures of Ag,Al,Au,Cu,Ir,Ni,Pd,Pt and Rh are more stable.Energy-volume curves of these metals fit the results of Rose equation.Structure stabilities are proved with volume change.Phonon dispersions of fcc metals along[100],[110] and [111] directions agree with experiments and other calculations.

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First-principles Study of Dehydrogenation Characteristics of LiAlH4 with Dopant Fe WANG Qing, DANG Wenqiang, DU Rui, DAI Jianfeng, LI Weixue 2012, 29(2): 297-302.  Abstract ( )   PDF (7217KB) ( )   With plane-wave pseudo-potential method of first-principles,effect of dopant Fe on dehydrogenation characteristics of LiAlH4 and mechanism were studied.Dopant formation energy,electronic density of states and dissociation energy of H were investigated.Bonding state and structure-stability of the crystal were analyzed.It indicates that as Fe occupied an interstitial site,an Al site or an Li site,dehydrogenation properties of LiAlH4 were improved.Fe tended to occupy the interstitial site.Analysis on electronic structure reveals that there exist strong interactions between a dopant Fe and its nearest neighbouring Al atoms as Fe occupied an interstitial site.Meanwhile,interaction between a dopant Fe and its nearest neighbouring H atoms is also considerably strong.Stability of the [AIH4] ligand is distorted.Therefore,dehydrogenation properties of LiAlH4 are improved.In general,dopant Fe improve dehydrogenation properties of LiAlH4,which is consistent with experimental observations.

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First-principles Study of Structural Transformation of ZnO Under Low Pressures ZHANG Fangying 2012, 29(2): 303-307.  Abstract ( )   PDF (251KB) ( )   Structural,elastic,and electronic properties of B4,B3,and B1 ZnO under 0~15 GPa are studied with first-principles method combined with energe-of-state and elastic calculations.It shows that under 0~15 GPa,the energy of B4 ZnO is always lower than that of B3 ZnO.Either B4 or B3 transforms to B1 at a critical pressure,i.e.,11.8 GPa for B4 and 12.4 GPa for B3.As B4 transforms to B1,volume of the system reduces to about 88.3% of the initial value.The results agree with available experimental and theoretical data.The shear modulii reduce rapidly as the pressure is larger than 6 GPa,which means that some structural change may happen.It agrees with recent experimental results.Electronic properties show that the interaction between Zn 3d and O 2p reduces as the pressure increases.

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Modeling and Identification of Associated Complex Networks TANG Shengxue, CHEN Li, HUANG Jiaoying 2012, 29(2): 308-316.  Abstract ( )   PDF (894KB) ( )   An identification method for node parameters and topologies of complex networks is investigated with network heterogeneously splitting in a driving-response model.Modeling of heterogeneously associated networks is presented.Two heterogeneously associated complex networks are disassembled and modeled.With LaSalle invariance theory,Gram matrix and driving-response model,adaptive observers for identifying node dynamical parameters and topological parameters of heterogeneously associated complex networks are obtained.Node parameters and coupling topology parameters can be identified on line using the proposed observers.Numerical simulations indicate that the proposed methods are effective.