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25 January 2011, Volume 28 Issue 1 Previous Issue    Next Issue

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A Discontinuous Galerkin Method with Local Time Stepping for Euler Equations WU Di, YU Xijun, XU Yun 2011, 28(1): 1-9.  Abstract ( )   PDF (781KB) ( )   We use discontinuous finite element method to solve three-dimensional hydrodynamic equations.The domain is divided with an unstructured tetrahedral mesh.In order to overcome low efficiency of explicit scheme,especially as sizes of cells vary strongly,we use a local time stepping technique(LTS).We integrate control equations in space and time to obtain a single-step scheme.The calculation of each grid cell can be localized.It avoids excessive memory difficulties as dealing with three-dimensional problem with high order Runge-Kutta method.ADER method is used to calculate numerical flux across element boundary to improve accuracy of the hydrodynamic equations.Finally,numerical examples demonstrate stability and effectiveness of the method.

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Three-dimensional Global Linear Stability Analysis of Compressible Flow Around a Sphere XIN Xiaofeng, LIU Yang, MA Dongjun, SUN Dejun 2011, 28(1): 10-18.  Abstract ( )   PDF (914KB) ( )   Global linear stability of compressible,three-dimensional flow around a sphere is investigated with a quasi-linearization method on Navier-Stokes equations.An implicit restarted Arnoldi approach is adopted to solve the eigenvalue problem.The global stability problem of three-dimensional compressible basic flows around a sphere is investigated at subcritical parameters of Reynolds number Re=200,Mach number M=0.2,and supercritical parameters of Re=300,M=0.6.It shows that the increasing of Mach number(up to 0.6) has no qualitative influence on transition of flow patterns.

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A Finite Volume Method for 2D Inviscous Lagrangian Hydrodynamics Based on Characteristics Theory SUN Yutao, REN Yuxin, YU Ming, ZHANG Shudao 2011, 28(1): 19-26.  Abstract ( )   PDF (604KB) ( )   We present a cell-centered finite volume method for 2D invicsous Lagrangian hydrodynamics.Velocity and pressure on vertex of a cell are computed with characteristics theory,which is derived from governing equations of Lagrangian form linearized by freezing Jacobian matrices about a known reference state.The velocity is used to update coordinate of vertex of a cell.Product of two variables is used to compute numerical flux through cell interface by a trapezoidal integration rule.Convergency,symmetry and conservation of total energy of the method are demonstrated.The method can be applied to structured or unstructured grids,and does well spontaneously for multi-material flows in a robust way.The scheme is one order precision,and can be easily draw on two order precision.

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Numerical Simulation of Turbulent Jet Diffusion Flame in a Variable-density Stochastic Vortex Model ZHU Yuejin, DONG Gang, LIU Yixin, FAN Baochun 2011, 28(1): 27-34.  Abstract ( )   PDF (571KB) ( )   A variable-density stochastic vortex model is used in simulating H2/O2/N2 turbulent jet diffusion flames,in which turbulence is modeled by vortex sample,vortex suppression and vortex turnover.A large-vortex suppression mechanism for variable density reacting flows is presented and effects of parameters in model prediction are discussed in detail.It shows that the modified model can predict reasonably H2/O2/N2 jet flame structures,and reflect characteristics of turbulent vortices.It also reveals that various parameters in vortex sample and vortex suppression affect results of the model.

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Numerical Simulation of Typhoon Movement with a Regional Spectral Element Barotropic Atmospheric Model LIU Xiying 2011, 28(1): 35-40.  Abstract ( )   PDF (610KB) ( )   Sharing advantages of spectral method and finite element method,a spectral element method is used in numerical study of geophysical fluid dynamics.By solving barotropic primitive equations with spectral element method,a regional barotropic atmospheric model is developed.In the model,computational domain is broken into a series of triangular elements,and variables in each element are represented as a high order Lagrangian interpolant with products of Legendre polynomials with triangular truncation.With geopotential and wind at 08 o'clock on 15 May 2006 on pressure level of 500 hPa taken as initial value and fixed lateral boundary condition,simulations of typhoon movement with maximum orders of Legendre polynomials 3 and 7 are carried out,respectively.It showns that the simulated relation between wind and pressure is rational and realization of the numerical model is successful.

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Numerical Simulation on Water Flooding Development of Fractured Reservoirs in a Discrete-fracture Model HUANG Zhaoqin, YAO Jun, WANG Yueying, LV Xinrui 2011, 28(1): 41-49.  Abstract ( )   PDF (1244KB) ( )   With equivalent concept of single fracture,a discrete-fracture model is developed,in which macroscopic fractures are described explicitly as(n-1) dimensional geometry elements.This simple step greatly improves efficiency of numerical simulation.The model can really reflect impact of fractures on fluid flow through fractured reservoirs simultaneously.A fully coupling discrete-fracture mathematical model is implemented using Galerkin finite element method.Validity and accuracy of the model and numerical algorithm are demonstrated through several examples.Effect of fractures on water flooding in fractured reservoirs is investigated.It demonstrates that the discrete-fracture model is valid for fractured reservoirs,especially for those reservoirs in which macroscopic fractures exist.

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Numerical Simulation of Electric Field in Resistivity LWD Using High Accuracy Self-Adaptive hp-FEM CHEN Xiaohui, LIU Dejun, MA Zhonghua 2011, 28(1): 50-56.  Abstract ( )   PDF (818KB) ( )   A high accuracy self-adaptive hp-finite element method(FEM) is used to simulate resistivity logging-while-drilling(LWD) electric field distribution.The algorithm can choose optimal refinement and calculation strategy according to practical formation model and error estimation.Accurate approximations of electrical field can be obtained without an accurate solution in the entire computational domain.Self-adaptive hp-FEM method has an exponential convergence rate.It indicates that voltage phase difference and amplitude ratio curves between receiver coils are well matched with the layer model.It is helpful to interpretate resistivity LWD data.

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A Fast Algorithm for Nonlinear Finite Sound Beams Based on Spatial-domain Decomposition XIAN Yongli, DU Hongwei, WANG Congzheng, PENG Hu 2011, 28(1): 57-65.  Abstract ( )   PDF (983KB) ( )   A fast numerical algorithm for nonlinear finite sound beams is studied.Multiple couplings in nonlinear finite sound beams are found,including full coupling between the harmonics,recursive coupling between field points along the axial direction,and local coupling along the radial direction.Calculation efficiency is improved by a spatial-domain decomposition of acoustic field along radial direction.The method is achieved through a multi-threading parallel computation.Calculation results for nonlinear focused Gaussian beams show that as problem size and the number of threads are reasonablly matched,this algorithm can significantly improve calculation speed while ensuring accuracy.Calculation results are compared with theoretical analysis.

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Quantification of Uncertainties in Detonation Simulations MA Zhibo, ZHENG Miao, YIN Jianwei, HU Jie, WEI Lan 2011, 28(1): 66-74.  Abstract ( )   PDF (762KB) ( )   According to the principles of Modeling & Simulation(M&S)and charactersitic of detonation system that final performances are determined by initial conditions,total uncertainties are sorted to three parts that varying along with initial conditions.It reveals how uncertainties are brought on and evolve from benchmark models to new models.Based on engineering practices and technology of verification & validation,a framework of quantification about uncertainty is brought forward in detonation simulation.An example is presented to demonstrate general idea in quantifying uncertainty of M&S.

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SIRT Method for Diagnostics of Inhomogeneous Dense DT Plasmas with Fast Protons LI Xuemei, SHEN Baifei, ZHANG Xiaomei, WANG Zhiwen, HE Yanhe 2011, 28(1): 75-80.  Abstract ( )   PDF (309KB) ( )   Density reconstruction of inhomogeneous dense DT plasmas is studied with simultaneous iterative reconstruction technique(SIRT).In simulation of density diagnostics of a two-dimensional(2D) slice plasma,fast protons used fordiagnostics can be generated with laser-plasma interaction and energy loss of fast protons going through plasmas is crucial.As original and final energies of protons are given,density reconstruction by SIRT method is done without noise level of final energies.Accuracy of the method is better than that of the Tikhonov regularization method based on deviation principle of L-curve.In addition,the SIRT method is available with incomplete data.

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Spatial Distribution of Few-cycle Laser Pulses Propagating in a Ladder-type Three-level Medium WANG Lei, WANG Zhendong, LIANG Bian, FAN Xijun 2011, 28(1): 81-86.  Abstract ( )   PDF (311KB) ( )   With numerical solution of full Maxwell-Bloch equations obtained by finite-difference time-domain method and iterative predictor-corrector method,spatial distributions of pulse and populations of few-cycle laser pulse propagates in a ladder-type three-level atomic medium are investigated.It shows that,spatial distributions changes evidently with pulse area.As the pulse area is smallr,the pulse shape is irregular and oscillation time increases.As the pulse area is large,the pulse shape becomes relatively regular and oscillation times decreases evidently.With increasing of pulse area,amplitude and group velocity of pulse increase progressively,oscillation times of populations increase gradually and variation of spatial distributions of the pulse and populations at different moments decreases considerably.Moreover,spatial distribution of populations correlates closely to spatial distribution of the pulse.

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Real-coded Hybrid Genetic Algorithm for Particle Sizing with Photon Correlation Spectroscopy REN Shibo, HAN Peng, YANG Guanling 2011, 28(1): 87-93.  Abstract ( )   PDF (345KB) ( )   A real-code hybrid genetic algorithm for nano-particle sizing with photon correlation spectroscopy is presented.With ergodic properties of chaos and simulated annealing algorithm,our algorithm shortens inversion range automatically.It has a relatively strong local searching ability.Numerical simulations are performed for mono-disperse particle system under noise-free condition and noise with various noise levels.Inversion of experimental results of 90nm standard samples of polystyrene particles is made.It shows effectiveness,reliability and ability of noise resistance of the algorithm.

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Numerical Simulation of Molecules Adsorbed on Metal Nanocone Surfaces YOU Rongyi, HE Hongsheng, HUANG Xiaojing 2011, 28(1): 94-98.  Abstract ( )   PDF (505KB) ( )   In uniform external electric field, CO molecules adsorbed on the surface of nonocones that grow on a transition metal substrate are modeled as equivalent dipoles.Mathematical models are given with consideration of three interactions,i.e.,interaction between dipoles and local electric field,dispersion interaction between dipoles and dipoles,as well as interaction between dipoles and atoms of nanocone surface.Spatial distribution of CO molecules adsorbed on nanocone surfaces is obtained by Monte-Carlo method.It shows that the CO molecules adsorbed on nanocone surfaces agglomerate locally with these interactions,and molecules adsorbed on top of the nanocone become dense with a decrease of conical angle of nanocone.It results in more powerful interaction among molecules.It may provide an explanation for abnormal infrared effects(AIREs) observed as CO molecules adsorbed on nanostructured transition metal surfaces.

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A Molecular Dynamics Study of Chemisorption of C2 Clusters on Diamond (111) Surface GUO Decheng, LI Shuang, YAN Mengze, ZHAO Yanchun, LI Zhijie 2011, 28(1): 99-104.  Abstract ( )   PDF (573KB) ( )   Chemisorption of energetic C2 clusters on diamond(111) surface is investigated with molecular dynamics simulation and mang-body interatomic Brenner(#2) potential.At 300 K,molecular dynamics simulation are performed as a C2 cluster bombards six different bombarding sits on diamond(111) surface at incident energies of 1 eV,20 eV,30 eV,respectively.Different chemisorption configurations are observed.Deposition of C2 atoms are observed during the bonding collision.Influence of sits and impact energy on structure of deposited clusters are discussed.It shows that the collision processes change in different environments.Increase of cluster incident energy is apt to bond forming.

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First-principles Calculation of Thermodynamic Properties of TiO2 Compound HU Yanfei, YUAN Yuquan 2011, 28(1): 105-110.  Abstract ( )   PDF (424KB) ( )   By using first-principles plane-wave pseudopotential method of density functional theory,structures and thermodynamic properties of TiO2 are investigated.Calculated lattice parameters,bulk modulus,and the first order pressure derivative of bulk modulus are consistent with experimental result and theoretical analysis.In a quasi-harmonic Debye model,relative lattice parameters,relative volume,bulk modulus,thermal expansion,and heat capacity under different temperatures and pressures are successfully obtained.

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First-principles Study of Rutile-to-Fluorite Transition ZHOU Zhijian, HU Yanfei 2011, 28(1): 111-118.  Abstract ( )   PDF (397KB) ( )   Phase transition of TiO2 from rutile to fluorite is investigated with first principles plane-wave pseudopotential density functional theory,together with a quasi-harmonic Debye model.The rutile-to-fluorite(R-F) transition pressure and temperature obtained are 45.32 GPa and 2029 K,respectively,which are consistent with experimental and calculated results.The R-F transition pressure increase with increasing temperature.By fitting,we estimate transition pressure at experiment temperatures(T=1900-2 100 K,Pt=47.604-47.756 GPa).Moreover,dependences of relative volume V/V0 on pressure P,thermal expansion coefficient α and heat capacity cV on pressure P and temperature T are obtained.

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Suppression of Spiral Waves and Spatiotemporal Chaos in Cardiac Tissues with Controll of Calcium and Potassium Ionic Currents ZHONG Min, TANG Guoning 2011, 28(1): 119-124.  Abstract ( )   PDF (787KB) ( )   Suppression of spiral waves and spatiotemporal chaos in cardiac tissues described by LuoRudy 91 model are studied.We suggest a control strategy which applys calcium channel agonist to enlarge maximum conductivity of calcium current,and applys potassium channel blocker to reduce maximum conductivity of potassium current,for suppression of spiral waves and spatiotemporal chaos.It shows that the method can effectively suppress spiral waves and spatiotemporal chaos even if there exist defects without function of diffusion in a medium.The control mechanism is analyzed.

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Numerical Study on Roughness Distributions of 1+1 Dimensional Noisy Kuramoto-Sivashinsky Equation YANG Xiquan, TANG Gang, HAN Kui, XIA Hui, HAO Dapeng, XUN Zhipeng, ZHOU Wei, WEN Rongji, CHEN Yuling, WANG Juan 2011, 28(1): 125-130.  Abstract ( )   PDF (351KB) ( )   Roughness distributions of 1+1 dimensional noisy Kuramoto-Sivashinsky(KS) equation at steady states are obtained and compared with Kardar-Parisi-Zhang(KPZ) equation's with numerical simulation.It is shown that the scaling functions of roughness distributions of the noise KS equation in 1+1 dimensions show small finite-size effects.They are in good agreement with the Kardar-Parisi-Zhang(KPZ) equation's.

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Spin-polarized Transport Through a Quantum Dot Side-coupled to Ferromagnetic Leads and a Mesoscopic Ring HUANG Rui, WU Shaoquan, YAN Conghua 2011, 28(1): 131-137.  Abstract ( )   PDF (378KB) ( )   In a single impurity Anderson model,with equation of motion and Green function,we study spin polarized transport through a quantum dot side-coupled to ferromagnetic leads and a mesoscopic ring.It shows that the coupling strength between quantum dot and mesoscopic ring,spin polarization,relative angle of magnetic moment in ferromagnetic leads and temperature are all important parameters for electron transport in the quantum dot system.It can be used to generate a spin-valve effect.It provides theories for a quantum dot system as a new material of spinning electrons.

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An Algorithm for Chain-like Frequent Subcircuits Extraction in Digital Integrated Circuits PAN Weitao, XIE Yuanbin, HAO Yue 2011, 28(1): 138-144.  Abstract ( )   PDF (385KB) ( )   To reduce high complexity in extraction of functional regularity in digital ICs,a template called CHAIN generation algorithm is proposed based on data mining.Weights of edges are encoded,and a complex subcircuit isomorphism problem is solved by comparing edge weight sequences of the subcircuit.To reduce complexity and accelerate the algorithm,a pruning strategy is introduced into expending of templates to delete non-frequent subcircuits gradually.By merging template generation process and subcircuit isomorphism searching process,the regularity extraction flow is simplified.Experiments show that this CHAIN template algorithm is more effective.It obtains better circuit covering result than SPOG and TREE methods.

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Evaluation of DC I-V Characteristics and Small Signal Parameters of 4H-SiC Metal-Semiconductor Field Effect Transistors WANG Ping, YANG Yintang, LIU Zengji, SHANG Tao, Guo Lixin 2011, 28(1): 145-151.  Abstract ( )   PDF (311KB) ( )   With analysis on internal carrier transport mechanism in silicon carbide(SiC),an improved analytical model for dc current voltage and small signal parameters of 4H-SiC metal-semiconductor field effect transistor(MESFET) is proposed considering carrier velocity saturation and charge controlling.Incomplete dopant ionization and parasitic drain-source resistances are considered simultaneously.The simulated maximum transconductance is 48 mS·mm-1 at a gate voltage of 0 V.Simulations and physical measurements show good agreement.The model is simple in calculation and distinct in physical mechanism.It is suitable for design and research of SiC devices and circuits.

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A Repeater Insertion Delay Optimized Method with Interconnect Temperature Distribution DONG Gang, CHAI Changchun, WANG Ying, LENG Peng, YANG Yintang 2011, 28(1): 152-158.  Abstract ( )   PDF (503KB) ( )   With influences of interconnect inductance,thermal-electric coupling effects and interconnect temperature distribution,a delay optimized method by repeater insertion is presented.A interconnect resistance model and a delay model are obtained respectively based on interconnect temperature distribution.The repeater insertion optimal delay is calculated considering electro-thermal coupling among power,delay and temperature.Optimized results are successfully obtained with Matlab software.Repeater insertion in 45 nm technology is simulated.It shows effectiveness of the method.In addition,it indicates that the optimal delay is overestimated without inductance effect.Optimal delay is underestimated without consideration of temperature distribution.As overestimated global interconnect width is 245nm,8.71% optimal delay can be underestimated without considering temperature distribution effect.