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25 July 2013, Volume 30 Issue 4 Previous Issue    Next Issue

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Modified Nodal Expansion Method for Convection-diffusion Equation in Cylindrical Geometry DENG Zhihong, SUN Yuliang, LI Fu, Rizwan-uddin 2013, 30(4): 475-482.  Abstract ( )   PDF (1813KB) ( )   For efficient calculation of neutronic-thermal hydraulic coupling in pebble bed high temperature gas cooled reactor,a modified nodal expansion method (MNEM) was developed to solve convection-diffusion equation in cylindrical geometry.Within the framework of nodal expansion method,up to third-order polynomials combined with an orthogonalizd exponential function were adopted as basis functions for r-directed transverse integrated equation.Numerical tests reveal that the MNEM posses inherent upwind characteristic,and has good accuracy and stability for coarse meshes.

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Preconditioned Jacobian-free Newton-Krylov Methods for Nonequilibrium Radiation Diffusion Equations FENG Tao, YU Xijun, AN Hengbin, ZHANG Rongpei 2013, 30(4): 483-490.  Abstract ( )   PDF (1774KB) ( )   Four semi-implicit discretization schemes are used to construct preconditioners.And preconditioned Jacobian-free Newton-Krylov (JFNK) are presented to solve one-dimensional problems.Numerical results show that the preconditioning methods improve the convergence behavior of JFNK method dramatically.

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High-order Finite Difference Methods for Time-fractional Subdiffusion Equation ZENG Fanhai, LI Changpin 2013, 30(4): 491-500.  Abstract ( )   PDF (438KB) ( )   Two finite difference methods for time-fractional subdiffusion equation with Dirichlet boundary conditions are developed.The methods are unconditionally stable and convergent of order(τq+h2) in the sense of discrete L2 norm,where q(q=2-β or 2) is related to smoothness of analytical solution to subdiffusion equation,β(0 < β < 1) is order of the fractional derivative,τ and h are step sizes in time and space directions,respectively.Numerical examples are provided to verify theoretical analysis.Comparisons with other methods are made,which show better performances over many existing ones.

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A 1D Conservative Lagrangian ADER Scheme CHENG Junbo, Eleuterio F. Toro 2013, 30(4): 501-508.  Abstract ( )   PDF (1292KB) ( )   Based on Eulerian ADER scheme,we build a 1D,one-step,conservative,high-order accurate,Lagrangian ADER(LADER) scheme.Main procedures of r-th order LADER scheme include:Deducing integral form of the equations in Lagrangian framework from Euler equations,using WENO reconstruction method to reconstruct conserved variables and their spatial derivatives up to (r-1)-th order on interface of mesh with high-order accuracy,evaluating Godunov values of conserved variables and their space derivatives in Lagrangian framework,computing time material derivatives of conserved variables,approximating time-integral average of physical flux function with high-order accuracy at last.Simulation of smooth regions shows that LADER scheme achieves desired accuracy and examples of discontinuous regions show the scheme is essentially non-oscillatory near discontinuities.

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A High-order Moving Mesh Kinetic Scheme Based on WENO Reconstruction for Compressible Flows XU Xihua, NI Guoxi 2013, 30(4): 509-514.  Abstract ( )   PDF (1229KB) ( )   Based on WENO reconstruction,a high-order (at least third order) moving mesh kinetic scheme is presented for compressible flows.It employs the frame of remapping-free ALE-type kinetic method to discrete Euler equation.Adaptive moving mesh approach is used to move meshes.Kinetic flux evolution is used to construct numerical fluxes in order to achieve their time-accuracy.Numerical results demonstrate accuracy and robustness of the scheme.

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Criteria of Flow Instabilities in Steam Generator U-Tubes with Natural Circulation HAO Jianli, CHEN Wenzhen, YANG Lei, WANG Shaoming 2013, 30(4): 515-519.  Abstract ( )   PDF (723KB) ( )   For flow instabilities in inverted U-tubes steam generator (SG),a dimensionless analysis is made for flow equation.Criteria of flow stabilities (characteristic Reynolds number) are derived according to small perturbation analysis.With calculation for a certain type of SG,effect of inlet fluid temperature and U-tube bend radius on the criteria are studied.It shows that the characteristic Reynolds number increases with the increase of inlet fluid temperature.Relations between U-tube bend radius under different inlet temperatures are complex.It is useful for calculation of flows as well as space distribution of reverse flow in a SG.

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Lattice Boltzmann Simulation of Multiphase Flows in a Square Cavity HONG Ning, LI Tiyun, LI Qiuxiang, SHI Baochang 2013, 30(4): 520-526.  Abstract ( )   PDF (2258KB) ( )   Lattice Boltzmann multiphase method based on Shan-Chen model is used to a systematic study on dynamics of two-phase fluid flows in a lid-driven square cavity.Effects of Reynolds (Re),Capillary number (Ca) and surface wettability on flowing and mixing are investigated in details.It shows that the greater the Re and Ca,the longer pength of two phase fluid mixing interface in the cavity.In addition,the length of mixing interface increases with surface hydrophobicity.However,for a highly hydrophilic surface,the length of mixing interface tends to a constant finally.

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Numerical Study of Inhibitory Effect of Angiostatin in Blood Perfusion and Interstitial Transport in Metastatic Tumor ZHAO Gaiping, FANG Xinguo, CHEN Eryun, YU Xiaoli 2013, 30(4): 527-533.  Abstract ( )   PDF (1291KB) ( )   Blood perfusion and interstitial fluid transport in metastatic tumor microcirculation based on microvasculature response to angiostatin's inhibitory effect are investigated.Microvascular network model contains inhibitory effect of angiostatin,chemotaxis response of tumor angiogenic factors and random motility of endothelial cells.Blood flow,interstitial fluid transport and transvascular flow are described by extended Poiseuille's,Darcy's and Starling's law,respectively.It shows that angiostatin can decrease branching,anastomosis and proliferation of capillary sprouts and inhibit growth of a capillary network in metastatic tumor;Angiostatin can improve capacity of blood perfusion and material exchange within metastatic tumor microenvironment;Furthermore,angiostatin can increase convective flow out of vasculature and result in reduced difficulty of drug delivery and penetration within a metastatic tumor,which agree with experimental observed facts.It may provide theoretical references and foundation understandings for further clinical anti-angiogenic cancer therapy.

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Inversion of Surface Heat Flux in Two-dimensional Variable Geometry Heat Conduction SHAO Yuanpei, HE Kaifeng, ZHOU Yu, QIAN Weiqi 2013, 30(4): 534-540.  Abstract ( )   PDF (2269KB) ( )   Conjugate gradient method (CGM) is developed for the estimation of surface heat flux in two-dimensional variable geometry heat conduction problem from temperature measurements.In typical exemplified case,it is shown that CGM is feasible and robust.Further studies reveal that estimated results are influenced by number of measurement points and initial estimation.The number of measurement points are related to intensity of heat flux spatial variation.And the final heat flux should be chosen as the initial estimation.

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A Modified Linde Model for Damage in Composite Laminates ZHAO Shiyang, XUE Pu, ZHU Jie 2013, 30(4): 541-546.  Abstract ( )   PDF (776KB) ( )   A finite element model of a three-dimensional composite laminate with initial damage is established with continuum damage mechanics.With strain failure criterion proposed by Linde and a parameter modifying damage function,failure behavior of matrix and fiber in laminates is simulated.Damage variable's variation with deformation can be achieved by changing of the parameter.Numerical results vary obviously with the parameter.Examples demonstrate that the parameter can reduce error,and make simulation agree with experiment result.The induced parameter can extend application of the Linde model and increase precision of simulation.

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Meshless Kriging Interpolation Method for Bending of a Moderately Thick Plate CHEN Shenshen, LI Qinghua, OU Manli 2013, 30(4): 547-553.  Abstract ( )   PDF (766KB) ( )   Based on Reissner-Mindlin plate theory,a meshless Kriging interpolation method (MKIM) is developed for bending of moderately thick plate.Corresponding discrete equations are derived.Approximation function in the method is built on a group of scattered nodes and therefore it can eliminate effectively complex meshing and disadvantage of mesh distortion.Compared with moving least squares (MLS) approximation widely used in meshless methods,shape functions constructed by moving Kriging interpolation method possess Kronecker delta property,which facilitates imposition of essential boundary conditions.High efficiency,good accuracy and easy implementation of the method in bending of moderately thick plate problem are demonstrated with numerical examples.

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Near-to Far-zone Transformation in Half-space by FDTD:TE Case JIANG Yannan, YANG Lixia, YU Xinhua 2013, 30(4): 554-558.  Abstract ( )   PDF (1200KB) ( )   A method to calculate far-zone scattering fields of a target in half-space excited by TE wave is proposed.Formulas of Green's function in a pair of vector potentials is derived,by which far-zone scattering field Hz can be calculated.Core of the method is calculation of electric and magnetic currents and their spatial phase in near-zone,which is elaborated.Far fields of an example are considered,which validates the method.Finally monostatic RCS of Type 96 armored vehicle is calculated.It is found that the maximum RCS is reached at head-in incidence case.

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Three-dimensional Electrical Impedance Tomography for Bladder Filling Estimation RAN Peng, HE Wei, XU Zheng, LI Bing 2013, 30(4): 559-564.  Abstract ( )   PDF (1775KB) ( )   Physics and mathematics model for three-dimensional bladder filling estimation are constructed for electrical impedance tomography.Verification was carried out with combined Tikhonov regularization algorithm.Reconstruction results with high spatial resolution,high stability and enhanced anti-noise performance were obtained.With Laplacian analysis of calculation results,boundary was extracted and processed.As a result,integration boundary surface fragments were extracted from high noise background in morphological characteristics of the object.Ultimately,three-dimensional image reconstruction was achieved.Compared with two-dimensional imaging,it provided spatial position,height and spatial contrast for qualitative analysis.

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Molecular Motor Dynamics in Impact Force Model LI Chenpu, HAN Yingrong, ZHAN Yong, HU Jinjiang, XIE Geying, ZHANG Ligang, FAN Hong 2013, 30(4): 565-570.  Abstract ( )   PDF (766KB) ( )   With transport characteristics and experiment about molecular motor,an impact force model is established,which conforms Langevin equation.Kinetics of molecular motor transport is analyzed.Molecular motors could take stable stepping motion and effective transport in right impact force combined with noise intensity.Direction of motion of molecular motor is adjusted by direction of impulse force.Though average speed is not zero at different noise intensity,efficient transport of molecular motor ensemble indicates that the system is selective on noise intensity.Average speed of molecular motor ensemble decreases with increasing of load force,the motion even changes its direction as load force is great enough.

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Stochastic Waiting Time Sampling Method in CTRW Model WANG Yan 2013, 30(4): 571-576.  Abstract ( )   PDF (1752KB) ( )   Continuous-time random walk (CTRW) models with truncated power law waiting time distribution are investigated.Possible Monte Carlo algorithms to draw random numbers with such distribution are discussed.And an accurate rejection-acceptance method is proposed.Its sampling efficiency is greater than 80% as the power law exponent α > 0.2.Scaling relations of three types of anomalous transport arising in CTRW models are obtained.

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Nano-twin Structure Simulation with Phase Field Crystal Method GAO Yingjun, WANG Jiangfan, LUO Zhirong, LU Qianghua, LIU Yao 2013, 30(4): 577-581.  Abstract ( )   PDF (1229KB) ( )   Two-mode phase-field-crystal (PFC) method is used to simulate coherent boundary of nano-twins.It shows that atomic arrangement in coherent twin-grain boundary is not in good order as sphere grains grow and run into each other to form dislocations.Atomic arrangement in coherent twin-grain boundary as band-shape grains colliding each other is more tidy.For designing and controlling numbers of atomic layer in nano-twins,PFC model can be used to realize manipulation for coherent nano-twins structure.It is significant for guiding experiment and revealing nano-twins structure and properties.

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Near-field Electric Potential Distributions around Metallic Nanostructured Surfaces YOU Rongyi, HUANG Xiaojing 2013, 30(4): 582-586.  Abstract ( )   PDF (1699KB) ( )   For half-spherical nanoparticles grow symmetrically on a plane metallic substrate in an external uniform electric field,a model of near-field electric potential distribution around nanoparticles is established.Spatial distribution of near-field electric potential is obtained.It shows that electric potential distributions exhibit obvious symmetry,which could serve as the basis for explaining abnormal phenomena related to nanostructured films,as well as reference for application of nanofilm materials.

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Structures and Stability of WmCn Clusters Zhang Xiurong, Li Weijun, Zhang Fuxing, Yuan Aihua 2013, 30(4): 587-595.  Abstract ( )   PDF (1005KB) ( )   Possible equilibrium geometries of WmCn clusters are optimized by using density functional theory at B3LYP/LANL2DZ level.For ground-state structures,average binding energy,second difference in energy,HOMO-LOMO gaps and the Wiberg bond index are analyzed.With increasing tungsten atoms,structures of clusters transform from linear into planar,and then become three-dimensional structures.All spin multiplicity is not more than 5.Hybridization of carbon atoms enhanced stability of the clusters,but reduced chemical activity.And Wiberg of W-C is much stronger than that of W-W and C-C,so it is easier to form W-C bond in WmCn clusters.

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Structures and Magnetic Properties of Ptn(n=1-9) Clusters:First-Principles Calculation WEN Junqing, ZHOU Hong, ZHANG Chenjun, WANG Junfeng 2013, 30(4): 596-604.  Abstract ( )   PDF (941KB) ( )   Structures,stabilities,and magnetic properties of Ptn(n=1-9) are calculated with generalized gradient approximation functional BPW91 and three-parameter hybrid density functional B3LYP in density functional theory.The methods give same stable structures and same lowest-energy structures but different stable order of sub-stable structures.Average coordination numbers and average bond lengths in two methods have similar patterns.They increase with cluster size,and have a great increase at n=2-3 and a small increase at n=4-9.Analysis of energies by two methods show that there are greater values at n=2,5,8,which illustrate that corresponding clusters have high stabilities.Study of Pt clusters indicates that average magnetic moment oscillates with cluster size.It has a gradually decrease trend.It shows that two methods can describe structures,stabilities and magnetism of clusters.

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Quantum-dot Semiconductor Optical Amplifiers in State Space Model Hussein Taleb, Kambiz Abedi, Saeed Golmohammadi 2013, 30(4): 605-612.  Abstract ( )   PDF (1371KB) ( )   A state space model (SSM) is derived for quantum-dot semiconductor optical amplifiers (QD-SOAs).Rate equations of QD-SOA are formulated in the form of state update equations,where average occupation probabilities along QD-SOA cavity are considered as state variables of the system.Simulations show that SSM calculates QD-SOA's static and dynamic characteristics with high accuracy.

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Computation for a System of Particles in a Quantum Ring WU Hong 2013, 30(4): 613-619.  Abstract ( )   PDF (284KB) ( )   A system of charged particles in a quantum ring consists of a great number of base vectors of eigenfunctions and Hamiltonian matrix elements,resulting in a huge amount of numerical computations.This paper describes a method for solving the problem according to a classification of orbital angular momentum.It introduces technique to select sub-vector sets from eigenvectors.The method reduces the computation by more than 90%.

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Effect of Conduction Delay on Dynamics of Spiral Waves CHEN Xiqiong, DENG Minyi, TANG Guoning, KONG Lingjiang 2013, 30(4): 620-626.  Abstract ( )   PDF (2778KB) ( )   Effect of conduction delay on dynamical behavior of spiral waves is investigated in Greenberg-Hastings model.It shows that in some cases dynamical behavior of spiral waves is not impacted by conduction delay.Changes in wavelength and wave speed,breathing spiral wave,multi-armed spiral wave,coexistence of spiral wave and anti-spiral wave are observed.Physical mechanisms of these phenomena are briefly analyzed.

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Quantum Adaptive Immune Clone Algorithm Based on Cloud Model MA Ying, TIAN Weijian, FAN Yangyu 2013, 30(4): 627-632.  Abstract ( )   PDF (815KB) ( )   Based on a cloud model,which makes good balance between randomness and fuzziness,a quantum adaptive immune clone algorithm is proposed.The quantum rotate gate,a key operator of quantum evolutionary algorithm for optimization and mutation operation,is insteaded by cloud operators.Dynamic adjustment of searching range in evolutionary process is realized by controlling collaboration of cloud operators.It makes the algorithm has strong ability in global search.Programs are modified for targeted optimization.They make algorithm avoid falling into local optimum effectively.Simulation experiments for standard numerical optimization problems show that the proposed algorithm has better search capability,higher search precision,and better stability.Simulation experiment in parameters estimation of nonlinear system shows that the algorithm gets effectively estimation for system parameters with high accuracy and good performance.