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25 January 2016, Volume 33 Issue 1 Previous Issue    Next Issue

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Global Sensitivity Analysis Based on Polynomial Chaos HU Jun, ZHANG Shudao 2016, 33(1): 1-14.  Abstract ( )   HTML ( )   PDF (658KB) ( )   Global sensitivity analysis method based on polynomial chaos and variance decomposition is reviewed comprehensively. In order to alleviate "curse of dimensionality" coming from high-dimensional random spaces or high-order polynomial chaos expansions, several approaches such as least square regression, sparse grid quadrature and sparse recovery based on l1 minimization (i. e. compressive sensing) are used to reduce sample size of collocation points that needed by non-intrusive polynomial chaos method. With computation of Sobol global sensitivity indices for several benchmark response models including Ishigami function, Sobol function, Corner peak function and Morris function, effective implementations of polynomial chaos method for variance-based global sensitivity analysis are exhibited.

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Numerical Simulation of Deflagration to Detonation Transition in Explosives Under Weak Ignition DONG Hefei, HONG Tao, ZHANG Xiaoli 2016, 33(1): 15-22.  Abstract ( )   HTML ( )   PDF (1065KB) ( )   By introducing conductive burning process into classical deflagration-to-detonation transition (DDT) model, transition process from low speed conductive burning to convective burning to detonation was proposed. Transition process in HMX granular bed with 85% loading density was simulated. Development of conductive burning, convective burning and detonation was analyzed. In early stage combustion propagation rate is very slow. It propagates no more than 0. 2mm within 8. 16ms. After onset of convective burning, it tooks 20 ms to form a steady detonation with a velocity of 8 165 m·s-1. Time to form detonation increases with decrease of particle diameter and ignition pressure.

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A Numerical Study of Interactions Between Shock Waves and Flame with GPU Acceleration JIANG Hua, DONG Gang, CHEN Xiao 2016, 33(1): 23-29.  Abstract ( )   HTML ( )   PDF (707KB) ( )   To study performance of graphic processing unit (GPU) for computational fluid dynamics, simulation on interactions between shock waves and a flame interface, a typical compressible reactive flow, was carried out on CPU/GPU heterogeneous system. Several optimal strategies are taken to raise GPU code performance. Computational results and acceleration performance of GPU with different grid number were examined. It was found that computational results by parallel GPU are the same as those by traditional CPU based on MPI parallel of 8 threads. Computational times of two parallel methods linearly grow with increase of computational grid numbers. Compuational cost by GPU is less than cost by MPI. As grid number is small(1.6×104), speedup ratio of 8. 6 was achieved on GPU. As grid number grows, speedup ratio decreases. However, a ratio of 5.9 still can be held on GPU when grid number is more (4.2×106). Arithmetic on CPU/GPU heterogeneous system provides a good solution for large-scale computations of compressible reactive flows.

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Numerical Study on Viscous Fingering of Reaction Fluid in a Microchannel LEI Timan, MENG Xuhui, GUO Zhaoli 2016, 33(1): 30-38.  Abstract ( )   HTML ( )   PDF (954KB) ( )   Viscous fingering with simultaneous chemical reaction at interface is investigated in a micro channel based on lattice Boltzmann method. One-variable chemical model admitting two stable states is adopted. We focus on influence of chemical reaction on viscous fingering. It is found that fluid interface become thinner with increase of reaction rate, while changes of steady state concentration (interfacial concentration where rate of chemical reactions is zero) influence position and morphology of viscous fingering. Isolated droplet can be formed from tip of finger.

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Numerical Study of Droplet Splashing in a CIP-based Model ZHAO Xizeng, YE Zhouteng 2016, 33(1): 39-48.  Abstract ( )   HTML ( )   PDF (1312KB) ( )   A multiphase model CIP-ZJU (Constrained Interpolation Profile Method in Zhejiang University) is developed, which is applicable of simulating free surface flow including liquid splashing, wave breaking and overturning. Numerical simulations are performed with a Constrained Interpolation Profile(CIP)-based method adopted as the base flow solver combined with an enhanced VOF (Volume of Fluid) type scheme as free surface capturing method. To assess the algorithm and its versatility, drop impact onto flat liquid film and water entry of cylinders are simulated. Good agreement is obtained in comparing computational results with experimental data. It is demonstrated that many typical features in complex flow patterns can be captured in the present numerical model.

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Least Squares Regularized Method for One-Dimensional Source Inverse Heat Conduction Problem WU Ziku, LI Fule, DO Young Kwak 2016, 33(1): 49-56.  Abstract ( )   HTML ( )   PDF (547KB) ( )   We deal with one-dimensional source inverse heat conduction equation. An approach based on least squares support vector machines (LS-SVM) is proposed for semi-analytic approximate solutions. Furthermore, a parameters tuning formulism is shown and stability of the method is presented. The method yields high accuracy and stability solutions in practical examples.

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Electromechanical Fields at Three-Dimensional Interface Edge Between Two Bounded Piezoelectric Materials WANG Jingping, GE Renyu, HAN Youmin, ZHANG Jinlun, CHENG Changzheng 2016, 33(1): 57-65.  Abstract ( )   HTML ( )   PDF (648KB) ( )   With asymptotic assumption for physical field near notch tip, characteristic differential equations for electroelastic singularities of wedges that contain bounded piezo/piezo materials are built from three-dimensional equilibrium equations and Maxell equations. Mechanical and electric boundary conditions are expressed by combination of singularity orders and characteristic angle functions. Thus, evaluation of singularity orders is transformed into solving ordinary differential equations (ODEs) under designated boundary conditions. Interpolating matrix method is introduced to solve derivative ODEs. More electroelastic singularity orders and associated eigenfunctions in wedges that comprise two bounded transverse isotropic piezoelectrics materials are obtained. It shows that the method is efficient and has high accuracy compared with existent solutions.

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Numerical Investigation on Eccentricity Effect in Richtmyer-Meshkov Instability Induced by Converging Shock Wave HE Huiqin, ZHAI Zhigang, SI Ting, LUO Xisheng 2016, 33(1): 66-74.  Abstract ( )   HTML ( )   PDF (1091KB) ( )   Development of Richtmyer-Meshkov instability induced by a converging shock wave and its reflected shock from converging center is numerically investigated in which emphasis is on eccentricity effect. VAS2D uses finite volume method which has a secondorder precision in both temporal and spatial scales. Four types of 2-dimensional SF6 column (circle, small-amplitude single-mode, large-amplitude single mode and square) surrounded by air are adopted. Interface morphologies show that development of RM instability in eccentric case results from perturbation growth in concentric case combined with little perturbation growth caused by eccentricity. For interface without initial perturbation, eccentricity results in appearance of tiny perturbation structures. For interfaces with initial perturbation, eccentricity makes perturbation structures asymmetric and distorted. Meanwhile, eccentricity affects pressure of interface center and area of mixed zone, which are closely related to development of RM instability.

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A Large-Scaled Total-Field Scattered-Field Source FDTD for Underwater Targets ZHENG Kuisong, LUO Huan, YU Hui, DING Tengjiang 2016, 33(1): 75-82.  Abstract ( )   HTML ( )   PDF (921KB) ( )   For detecting underwater targets, a total-field scattered-field source FDTD is proposed. Two FDTD simulations are included. Tangential electromagnetic fields on exchange surface are recorded in first simulation with fine grids. In second simulation, equivalent source is added with coarse grids at total-field scattered-field surface. Ratio of coarse grid to fine grid can be extremely large, such as N=10 while run time and consumed memory are reduced. Precision and validity of the method in calculating radiated fields of line current source are verified. Finally, the method is utilized to analyze electromagnetic response of underwater space with obstacles. Flexibility of the method in simulating a realistic underwater electromagnetic problem is illustrated. It is pointed out that delay time and magnitude of timing waveforms at receive points are different with conductivity difference of abnormal bodies.

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Stereodynamics Study of Li+HF(v=0-3, j=0-40)→LiF+H Reaction at Low Energies LI Hongzheng, LIU Xinguo, WANG Yanjie, LI Qi 2016, 33(1): 83-90.  Abstract ( )   HTML ( )   PDF (1181KB) ( )   With potential energy surface constructed in 2003, we study stereodynamics of reaction Li+HF→LiF+H using quasiclassical trajectory (QCT) method. Polarization dependent differential cross sections (PDDCSs) and P(θr,φr) distributions describing k-k'-j' correlation related to collision energies. Vibrational states and rotational states are discussed at 1.15 kcal·mol-1-5.0 kcal·mol-1. Furthermore, cross sections are compared with that of other calculations and experiments. It indicates that vibrational and rotational excitations have stronger impacts on PDDCSs and P(θr,φr) than collision energy. Backscattering polarization of product rotational angular momentum is positive correlated with collision energy. Cross sections agree well with results of other theories and experiments in the range of calculation collision energies.

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Structures and Magnetic Properties of ZnS Nanotubes Doped with Cr Atom CHEN Hongxia, XIE Jianming, LIU Chenglin, HU Xiaoyan 2016, 33(1): 91-98.  Abstract ( )   HTML ( )   PDF (1060KB) ( )   Structures and magnetic properties of Cr monodoped and bidoped single-wall ZnS nanotubes are studied with firstprinciples calculations. Formation energies of doped nanotube are lower than those of pristine ones, indicating that doing process is an exothermic reaction. Doped nanotubes have atom-like magnetic moments mainly due to 3d component of Cr atoms. Our results indicate that Cr-doped ZnS nanotubes tends to adopt ferromagnetic (FM) configuration. Energy differences between FM and antiferrimagnetic (AFM) is only 36 meV. To obtain room temperature ferromagnetism, we replace one S atom by C atom. Its FM states are lower in energy than AFM states by 497 meV. Such large energy differences imply that room temperature ferromagnetism could be expected.

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First-principles Calculation of Cu-Cr Co-doped AlN Diluted Magnetic Semiconductors WANG Jing, FAN Cong, DENG Junquan, WU Zhimin, LIU Chang, FAN Feng, HU Aiyuan, CUI Yuting 2016, 33(1): 99-107.  Abstract ( )   HTML ( )   PDF (1282KB) ( )   Geometrical structures of Cr doped and Cu-Cr co-doped 32-atoms supercell of AlN were optimized with first principles density functional based on full potential augumented plane waves and generalized gradient approximation (GGA). Lattice constant, band structure, electronic density and optical properties were calculated. It indicates that Cr-doped and Cu-Cr co-doped AlN are both half metallic, their band gaps become narrower. Cu-Cr co-doped AlN system has stronger spin polarization effect than Cr doped, and exhibits fine ferromagnetic. Range of optical absorption becomes broader with doping. Co-doping enhances long-wave absorption and energy loss decreases obviously.

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3D Topological Horseshoes with 1-Directional Expansion and Application in Compass Walking Model LI Qingdu, ZHAO Wubin, YANG Fangyan 2016, 33(1): 108-116.  Abstract ( )   HTML ( )   PDF (1189KB) ( )   It is hard to apply topological horseshoe in 3D maps due to high dimension and complex structure since dimension of a chaotic attractor is often lower than its state space. We fit a surface with attractor near a selected unstable periodic orbit, and present a "dimension reduction" method to find topological horseshoes with one-directional expansion in 3D space. It is realized with a MATLAB toolbox. Compass walking model is shown to verify effectiveness, and illustrates detailed procedure for finding a topological horseshoe. It successfully verifys existence of chaotic gait and analyzes chaotic invariant set with horseshoe.

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Application of SC Projective Synchronization Method in Secure Communication QIAN Hui, YU Hongjie 2016, 33(1): 117-126.  Abstract ( )   HTML ( )   PDF (878KB) ( )   A method of projective synchronization based on stability criterion of linear systems is introduced and a technical scheme of chaotic masking for secure communication is proposed. A nonlinear drive vector function of special chaotic state variable is constructed with scaling factor α for chaotic synchronization by separating linear and nonlinear terms properly. Transmission information is injected into one element of state vector as carrier signal. Complexity of masking information and decoding difficulty is increased. Lorenz attractor and hyper-chaotic Rössler attractor are used as an example to simulate sinusoidal information. Amplitude and frequency of signal can be chosen in a wide range. Added scale factor α makes decryption process more complex, thus improving security of communication. The method is proved effective for secure communication.