Archive

25 September 2003, Volume 20 Issue 5 Previous Issue    Next Issue

---

For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Select

Asymptotic Boundary Conditions of One-dimensional Atom for Intense Laser Field QI Yue-ying, LIU Xiao-yan, DING Pei-zhu 2003, 20(5): 377-380.  Abstract ( )   PDF (156KB) ( )   Asymptotic boundary conditions of one-dimensional atomic model in intense laser field are derived using Fourier transformation.Errors of the three asymptotic boundary conditions are analyzed.The probability distribution and the average energy for one-dimensional hydrogen atom in the intense laser field are numerically computed using the first boundary condition and the symplectic method for the linear inhomogeneous canonical equations.The results are compared with theoretic analyses.

Select

Numerical Simulation of the Vortex Structure in Compressible Shear Layers Behind Flat Plates with Different Thicknesses XIONG Hong-liang, LI Qian, CUI Er-jie 2003, 20(5): 381-385.  Abstract ( )   PDF (206KB) ( )   A high accuracy and resolution finite difference method is first used to simulate numerically the compressible wake shear layers induced by flat plates with different thicknesses. The new method is named the Fu-Ma UCD5-SCD6 hybrid compact scheme. The fully two-dimensional compressible Navier-Stokes equations are directly solved. Based on the Steger-Warming flux-splitting technique, the convective terms are discretized by using the fifth-order upwind compact difference method, while the dissipative terms are discretized by using sixth-order symmetric compact difference method. A third-order Rung-Kutta method is selected for time marching. At convective Mach number Mc=0.3, four flat plate thicknesses and three upper incoming Mach numbers are considered. In all cases, the self-excited large scale vortex coherent structures are captured successfully, and their spatial evolution such as eddy rollup and pairing is investigated. Results show that the flat plate thickness can obviously affect the coherent structures. Increasing the flat plate thickness can accelerate the vortex rollup and enhance mixing. Moreover, for the same convective Mach number, increasing incoming Mach number can delay the vortex rollup and damp the vortex pairing. This can somehow be attributed to the well-known compressibility effect.

Select

Numerical Study on Three Dimensional Turbulent Separated Flow in Right-angled Curved Duct by Three Turbulent Models DING Jue, WENG Pei-fen 2003, 20(5): 386-390.  Abstract ( )   PDF (235KB) ( )   3-D turbulent flow within 90° curved duct of square section is simulated numerically through Reynolds-averaged Navier-Stokes equations differentiated by the finite volume method. And three turbulent models, including standard k-ε two equation model, RNG k-ε model and Realizable k-ε model, are utilized to solve this problem respectively. The mathematic models and calculated results are given and compared with the experimental data. It is shown that turbulent flows within the core region and near-wall region of duct dominated by curved effects can be predicted accurately on the base of RNG k-ε model and two-layer zonal model.

Select

Reliability Assessment Using Multiple Information Sources MA Zhi-bo, ZHU Jian-shi, XU Nai-xin 2003, 20(5): 391-398.  Abstract ( )   PDF (284KB) ( )   The key step for reliability assessment with small sampling is to take advantage of the subjective information and the test data of input parameters. Subjective inference could just offer the reliability some incomplete information which can be generally assumed to exist in the form of either a prior mean or a prior credibility interval. To the trials with the outcomes of either survival-failure or normal distributed parameters, efficient approaches are developed to determine the conjugate prior distributions from the subjective information according to the principle of maximum entropy. The test data of input parameters are also transformed as the prior information of the output parameters according to statistics theory. Bayes theorem is used to synthesize the different informations and numerical examples are presented to illustrate the impact of non-experimental information on the reliability posterior, the needed test number and the reliability assessment.

Select

Numerical Simulation of Nonlinear Electric Field in Diamond Film Growth at Low Temperature via EACVD ZHAO Qing-xun, ZHANG Jing, XIN Hong-li, WEN Qin-ruo, YANG Jing-fa 2003, 20(5): 399-402.  Abstract ( )   PDF (192KB) ( )   Monte Carlo simulations are adopted to study the distribution of the nonlinear electric field in the reaction field of diamond film growth at low temperature via EACVD. The results indicate that the distribution of the electric field near the anode in the reaction field changes by exponential rules. Under certain bias voltages with the changing of pressure, there will be a reverse electric field near the anode. This reverse electric field is very important to some positive ions in diamond film growth at low temperature.

Select

Effects of Discharge Parameters upon Fast Atomic Species (N+,Nf) ZHANG Lian-zhu 2003, 20(5): 403-407.  Abstract ( )   PDF (219KB) ( )   Using a Combination of Monte Carlo models of fast electron and species (N2+,N+,Nf), the creation rates and the energy distributions of species (N+,Nf) at the cathode in nitrogen glow discharge under different discharge conditions are studied.It is shown that the total density of N+ and Nf depends on the creation rate of ions(N2+,N+) and the thermalization of Nf, and species(N+,Nf) bombarding negative wall is mainly produced by N2+-N2s dissociation at higher voltages,but mainly produced by e--N2s dissociation at lower voltages.

Select

Spallation Target of ADS Neutron Source WAN Jun-sheng, ZHANG Ying, ZHANG Li-xing, XIA Hai-hong, DING Da-zhao 2003, 20(5): 408-412.  Abstract ( )   PDF (274KB) ( )   The spallation target of ADS is studied using the program DCM/CEM.The calculation of standard lead target bombarded with 0.1~1.6GeV proton beams is carried out.The neutron spectra and distribution over the lead target, energy deposition and neutron production in the lead target are studied. The simulation results agree with the former theoretical and experimental results.

Select

Calculation of In-core Fuel Management and Orthogonal Optimization for Xi'an Pulsed Reactor CHEN Wei, JIANG Xin-biao, ZHANG Ying, CHEN Li-xin, CHEN Da, XIE Zhong-sheng 2003, 20(5): 413-417.  Abstract ( )   PDF (265KB) ( )   An in-core fuel management code package HEX-ICFM is developed for Xi'an Pulsed Reactor.The orthogonal design model and the loading pattern optimization program HEX-ORTH are studied.The cell calculation is performed using WIMS-D/4.A two dimensional hexagonal geometry multigroup nodal theory code SIXTUS-2 is used for core diffusion calculation.The core physical parameters are calculated using HEX-ICFM for the first cycle of Xi'an Pulsed Reactor.With the fuel of end of cycle 3 and 30 fresh fuel rods the optimum loading patterns are calculated for the objective function max(KBOCeff)using HEX-ORTH.

Select

Surface-state Effects on Silicon Carbide Power MESFET's YANG Lin-an, ZHANG Yi-men, YU Chun-li, YANG Yong-min, ZHANG Yu-ming 2003, 20(5): 418-422.  Abstract ( )   PDF (288KB) ( )   An analytical non-linear model including surface-state effect is proposed for 4H-SiC power MESFET's with which the impact of suface damage at the ungate recess region caused by the dry-etching process on the output steady-state characterization can be illustrated clearly.The model has the advantage in very simple calculations over the 2D numerical simulations, therefore suitable for process analysis of SiC power MESFET's.

Select

TM Scattering and Transmission Properties of an Arbitrary Slit in a Conducting Plate Filled with Anisotropic Media WEI Bing, GE De-biao 2003, 20(5): 423-428.  Abstract ( )   PDF (239KB) ( )   The electromagnetic characteristics of transmission and scattering properties of a slit in a conducting plate filled with anisotropic media for TM polarization are dealed with. A general frequency domain method-the Generalized Network Formulation is simply introduced. To the best of our knowledge, this problem has not been dealt with in publications. The boundary element method(BEM) and Generalized Network Formulation are implemented to solve this problem and some examples are presented. The computed results are in agreement with the one obtained in isotropic case.This illustrates the feasibility of presented scheme. Two examples of the RCS and transmission coefficients for a slit filled with anisotropic media are also presented.

Select

Numerical Modeling of Seismic First Break in Complex Media ZHANG Jian-zhong, CHEN Shi-jun 2003, 20(5): 429-433.  Abstract ( )   PDF (282KB) ( )   A traveltime interpolation wavefront tracing method for numerical modeling of seismic wave in complex media is developed.It is based on an earth model consisting of uniform-velocity rectangular or polygonal cells with nodes placed at vertices and along cell edges.The wavefronts are propagated away from source throughout the entire model and sampled at the nodes,in which the first arrival time at a node is calculated by the interpolation of two previously computed traveltimes at all pair of adjacent nodes within a cell and minimization of traveltimes in the light of Fermat's principle. Once the wavefront traveltimes are sampled throughout the model, the minimal traveltime and raypaths from the source to receivers are easily obtained using the same technique as above.This method is regardless of model complexity,cell's shape and the positions of source and receivers.It can model all types of first arrival wave,such as direct waves,critical refractions and diffractions,and can trace entirely minimum traveltime paths.So it has a good flexibility and a high precision.At last,the method is applied to first arrival wave modeling of some typical near-surface models,the wavefront shapes and raypaths of which are shown explicitly.

Select

Numerical Simulation of Heavy Ion Microbeam for Effects of Single Event Upset and Single Event Burnout GUO Hong-xia, CHEN Yu-sheng, ZHOU Hui, HE Chao-hui, GENG Bin, LI Yong-hong 2003, 20(5): 434-438.  Abstract ( )   PDF (238KB) ( )   Effects of SEU and SEB are simulated with 0.4μm diameter microbeam. SEU for drain region of MOSFET and CMOS SRAM are calculated. Collective charge depending on LET for specific device structure is calculated for different ions. LET and critical charge are provided. SEB for VDMOS is simulated and electric field, potential line, current, rate of impact ionization are given at different times along ion tracks. It is very important for heavy microbeam test physics models which have been set up.

Select

Reconstruction Algorithm of Radial Function Neural Networks for Linear Attenuation Coefficients ZHANG Quan-hu, ZHANG Qi-xin, LÜ Feng, LI Ze, LI Kun-peng, WANG Zhong-qi, ZHAO Xue-jun, SUI Hong-zhi 2003, 20(5): 439-442.  Abstract ( )   PDF (174KB) ( )   Tomographic Gamma scanning(TGS) technique is an important technique in nondestructive assay(NDA). The image reconstruction problem of linear attenuation coefficients is very difficult and central in transmission TGS. A new image reconstruction algorithm of linear attenuation coefficients with neural networks is proposed based upon paper [1]. Simulated results indicate that the reconstruction relative errors of linear attenuation coefficients are less than 4% for the reconstruction algorithm of radial basis function(RBF) neural networks and the new algorithm has the merits such as fast response and high accuracy within a certain scope.

Select

Numerical Simulation of Erbium-Ytterbium Co-doped Waveguide Amplifiers by ADI-FDTD CHEN Hai-yan, DAI Ji-zhi, HUANG Xiu-jiang, LIU Yong-zhi 2003, 20(5): 443-446.  Abstract ( )   PDF (197KB) ( )   A new and simple numerical computational method simulating the gain characteristics of erbium and ytterbium co-doped phosphate glass waveguide amplifier(EYCDWA)is presented. This algorithm is a combination of the iterative procedure and the Finite-Differences Time-Domain based on Alternating-direction Implicit Method(ADI-FDTD), using ADI-FDTD calculating the normalized field intensity distribution of pump and signal and an iterative procedure studying the power propagation equations of the pump and signal. Numerical results demonstrate that the increase of the length and Er3+ concentration is two main approaches to improve the gain of EYCDWA, Yb3+ plays an energy transform role and 1~4 ratio of Yb/Er is better.

Select

Smoothed Particle Hydrodynamics Method to Numerical Simulation of Hypervelocity Impact ZHANG Gang-ming, WANG Xiao-jun, WANG Yuan-bo, WANG Ji, WANG Feng 2003, 20(5): 447-454.  Abstract ( )   PDF (495KB) ( )   Based on a brief description of Corrected Smoothed Particle Hydrodynamics (CSPH) method, the discretization scheme of conservation equations in axisymmetric coordinate systems is developed and a method to determine the number of particles in the computational domain is proposed. Numerical examples for hypervelocity impact are carried out and the results clearly show that CSPH is not only a suitable method for the simulation of large deformation problems in impact dynamics, but also a new method with the advantages that can not be replaced by finite element/ finite difference method.

Select

Numerical Model Experiment on the Onset of the Summer Monsoon over the South China Sea YANG Hui 2003, 20(5): 455-457.  Abstract ( )   PDF (172KB) ( )   The onset of the summer monsoon over the South China Sea is studied by the global spectral model(T42L9) of the Institute of Atmospheric Physics. The onset of the summer monsoon over the South China Sea is closely related to the intense convergence at 850hPa over the South China Sea, which is constituted by the cross-equatorial southerly divergent wind over the eastern Indian, the westerly divergent wind along the southern flank of the Tibetan Plateau, the northerly divergent wind along the eastern periphery of the Plateau, and the easterly divergent wind of the Western Pacific. Various sensitive numerical model experiments show that latent heating of the Southeast Asia and the dynamic effects of the Tibetan Plateau are both very important to those four divergent airstreams and that convergence.

Select

Rotation Symmetric Generalized Lorenz Strange Attractors WANG Xing-yuan 2003, 20(5): 458-462.  Abstract ( )   PDF (183KB) ( )   The technique of calculating the largest Lyapunov exponent of the differential equations is expounded, and the method determining the correlation dimension of the system from a time series is introduced. By utilizing the Lyapunov exponent as criterion and transforming the coordinates, the rotation symmetric generalized Lorenz strange attractors are constructed, and the activity characteristics of the strange attractors are analyzed and the correlation dimensions of the strange attractors are calculated.

Select

Numerical Simulation of Steam-foam Flooding for Heavy Oil Reservoir CHENG Lin-song, XIAO Shuang-ai 2003, 20(5): 463-466.  Abstract ( )   PDF (232KB) ( )   Based on the results of experimental study and field tests, the mechanisms of seepage and physicochemical phenomena in steam-foam flooding process are mainly concerned.On the foundation of conventional thermal models combined with the steam-foam flooding mathematical model,a new thermal models is established to consider steam-foam,thus the scope of application of thermal models is broadened.Factors are considered in the model such as surfactant concentration,nitrogen content and heterogeneous formation.The developed software is applied to study the mechanisms of fluid flow of steam-foam flooding in a well unit of the Gaosheng Oilfield with greater burial-depth and thicker oil-layer.Concerning steam-foam drive in heavy oil reservoir with thicker formation,sensitive factors and the feasibility are analyzed,the enhanced recovery mechanisms are discussed and some beneficial conclusions are reached.

Select

High-frequency Performance Including Self-heating Effect for AlGaAs/GaAs Power HBT's WANG Yuan, ZHANG Yi-men, ZHANG Yu-ming 2003, 20(5): 467-470.  Abstract ( )   PDF (169KB) ( )   A self-heating model is presented to predict the high-frequency performance of AlGaAs/GaAs heterojunction bipolar transistors (HBT's) including high current and thermal effects. A base pushout effect is discussed at high current region. And in this case, the lattice temperature, the cut-off frequency and the maximum frequency versus the collector current density are achieved.