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25 March 2004, Volume 21 Issue 2 Previous Issue    Next Issue

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Computing the Vibrational and Vibrational-rotational Energy Eigenvalues of 7Li2 by the Symplectic Scheme-matrix Algorithm HE Jian-feng, LIU Xue-shen, DING Pei-zhu 2004, 21(2): 95-98.  Abstract ( )   PDF (142KB) ( )   This paper presents the symplectic scheme-matrix algorithm for solving the vibrational and vibrational-rotational energy eigenvalues of 7Li2 in A1Σu+ state, and compares the computed results with the results calculated by Ley-Koo et al.. The results show that our method is convergent and reliable, and it is a reasonable method for computing the vibrational and vibrational-rotational energy eigenvalues of diatomic molecules. Since the symplectic scheme-matrix algorithm transforms the question of the solution of the radical equation of the diatomic molecules into that of the eigenvalues of the real tridiagonal symmetric matrix, it is more simple and needs smaller computer memory and less computing time compared with the method of expanding eigenfunctions of diatomic molecules used by Ley-Koo et al.

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Conservative High Resolution Scheme in Multicomponent Calculations CHEN Yi-bing, LIN Zhong 2004, 21(2): 99-105.  Abstract ( )   PDF (191KB) ( )   Conservative scheme in Lagrangian coordination is applied to compute multicomponent fluid dynamics, in which numerical flux of one order scheme is used near interface, while numerical flux of high resolution scheme is adopted in other areas. This scheme not only remains good high resolution, but also eliminates the oscillations due to common conservative scheme.

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Symplectic Scheme with High Order Accuracy for High Order Schrödinger Type Equation ZENG Wen-ping 2004, 21(2): 106-110.  Abstract ( )   PDF (143KB) ( )   A symplectic schemes with high order accuracy is proposed for solving the high order schrödinger type equation (əu)/(ət)=1(-1)m(ə2mu)/(əx2m) via the third type of generating function method. At first, the equation is written into the canonical Hamilton system; secondly, overcoming successfully the essential difficulty on the calculus of high order variations derivative, we get the semi-discretization with arbitrary order of accuracy in time direction for the PDEs by the third type of generating function method. Furthermore the discretization of the related modified equation of original equation are obtained. Finally, arbitrary order accuracy symplectic scheme is obtained. Numerical results are also presented to show the effectiveness of the scheme and its high order accuracy and properties of excellent long-time numerical behavior.

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Improvement of Node-searching Method in Meshless Method QIU Yi, YOU Chang-fu, QI Hai-ying, XU Xu-chang 2004, 21(2): 111-116.  Abstract ( )   PDF (327KB) ( )   In numerical simulation using meshless method,it usually concerns with searching nodes that are needed.In dealing with complex problems,there must be a great number of nodes distributed in computational domain.If traditional Node-Searching method is used here, it will be a burdensome task for the computer.So this paper proposes a new numerical arithmetic,Domain-Dividing method which means that the domain can be divided into several subdomains.Therefore,one can search some corresponding subdomains but not the entire domain for the neccessory nodes. It adopts the Node-Searching arithmetic to simulate the ideal flow over a cylinder,and shows that with the increase of the nodes in domain,the computational time of meshless method gets longer than that of finite element method,however compared with meshless method using conventional Node-Searching method,the arithmetic proposed here can spare much more time for searching nodes.

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The Momentum Profiles of Several Atoms Calculated by Discrete Variation Method LI Bin, LI Gui-qin, DENG Jing-kang, GAO Hong 2004, 21(2): 117-120.  Abstract ( )   PDF (164KB) ( )   Helium, Argon, Sodium and Kalium atoms are studied by using discrete variation method based on density functional theory. The orbital densities of He, Ar, Na and K atoms in momentum space have been calculated and the calculation results are as well compared with the experimental data.

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Calculation of Hot Iron Plasma Using Detailed Term Accounting(DTA) Model JIN Feng-tao, ZENG Jiao-long, YUAN Jian-min 2004, 21(2): 121-124.  Abstract ( )   PDF (267KB) ( )   Detailed term accounting(DTA) model is applied to calculate the radiative opacity of hot iron plasma,which has a temperature of 20 eV and a density of 0.01 g/cm3.In case of local thermodynamic equilibrium(LTE),Saha equation is used to calculate the populations of iron ions.The energy levels and oscillator strengths of bound-bound transitions are obtained by the multiconfiguration Hartree-Fock(MCHF) method.The Doppler broadening and electron impact broadening have been considered and the Voigt line profile has been applied in our calculation.We use the detailed configuration accounting(DCA) model and average atom model(AA) to obtain the bound-free and free-free absorptions respectively.The comparison between the present work result and Los Alamos National Laboratory(LANL) result shows a good agreement.

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Calculations of 1s22s-1s24p Transition Energies and Oscillator Strengths for Lithium-like Systems from Z=11 to 20 WANG Zhi-wen, HUANG Yan-hong, CHEN Chao, HU Jie, ZHAO Chang, HU Mu-hong 2004, 21(2): 125-130.  Abstract ( )   PDF (235KB) ( )   The full-core plus correlation method(FCPC)is extended to calculate the energies and fine structures of 1s24p states for the lithium-like systems with nuclear charge from Z=11 to 20.The transition energies(2s2S1/2-4p2P1/2,3/2) and dipole oscillator strengths are also calculated.The non-relativistic energies and wave functions are calculated by the Rayleigh-Ritz method.Relativistic and mass-polarization effects on the energies are included as the first-order perturbation corrections.The quantum-electrodynamics contributions to the transition energies are estimated by using the effective nuclear charge.Our results are in agreement with the experimental data available in the literature.

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Significance of Higher-order Accuracy Reconstruction Approximation and Perturbational Finite Volume Method GAO Zhi, XIANG Hua, SHEN Yi-qing 2004, 21(2): 131-136.  Abstract ( )   PDF (207KB) ( )   The perturbational finite volume(PFV) scheme has the same terse formulation as the first-order upwind scheme.However,PFV scheme is a mixed one in which the integration approximation is of second order accuracy and the reconstruction(or interpolation) approximation is of higher order.PFV scheme is still of second order accuracy in theory.The practical effect and benefit offered by higher-order reconstruction approximation in the upwind and central PFV schemes are verified numerically in this paper.

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2D Particle Simulation and Its Applications in Space Physics LU Quan-ming, GUO Jun, DOU Xian-kang, WANG Shui 2004, 21(2): 137-142.  Abstract ( )   PDF (370KB) ( )   In the PIC method of particle simulations,the physical variables related to the fields are assigned to the grids,while the particles can be anywhere in the simulation domain.Using this method,we design a 2D particle simulation code,and numerically study two common physical phenomena in space physics:beam instability and magnetic reconnection.In the beam instability,the beam plasma streams in the background plasma with the velocity Vb=10V-A(V-A is Alfvén speed),and the Alfvén waves are excited through wave-particle interactions.In the magnetic reconnection,the Harris current sheet can induce the magnetic reconnection,and the B-y shows quadrupolar structure.

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Calculation of Ground-state Energy of Two-electron Atom by Elastic Coordinate Variational Method CHEN Yu-hong, ZHAO Shu-cheng 2004, 21(2): 143-148.  Abstract ( )   PDF (135KB) ( )   An elastic coordinate variational method is given for calculating ground-state energy and wave function of two-electron atom. The program in terms of Matlab language has leen achieved. It provides numerical results of ground state energy of helium atom and helium-like ions.

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Numerical Properties of 3D Grids in a Nonhydrostatic Model LIU Yu-di 2004, 21(2): 149-155.  Abstract ( )   PDF (406KB) ( )   In the framework of linear baroclinic nonhydrostatic anelastic equations,calculation is undertaken for dispersions of inertia gravitational waves in different kinds of 3D(three-dimensional) grids from the perspective of frequency and group velocity, indicating that such 3D structures as EL/CP, C/CP and Z/LZ are superior to others in the computational dispersion properties, thereby providing a guidance to the selection of 3D grids applicable to atmospheric primitive equation nonhydrostatic models.

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Calculation of the Flexoelectric Effect in the Liquid Crystal Cell ZHANG Zhi-dong, YE Wen-jiang, XING Hong-yu 2004, 21(2): 156-160.  Abstract ( )   PDF (131KB) ( )   Negative liquid crystal MBBA that aligns along the normal to the plates in liquid crystal cell will arise the flexoelectric effect when a external electric field is applied in the plane of slab.Based on the elastic theory of liquid crystal and variation theory, the effect is studied, and the differential equation and boundary condition about the director of liquid crystal have heen obtained.Finite-difference iterative method is used for numerical solution. Under the approximation of small angle, analytical solution of the distribution of the director has been also obtained, and compared with the numerical solution and the result of book.

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The Application of Mixed Element Type Unstructured Grid in Solving Navier-Stokes Equations WANG, Gang, YE Zheng-yin 2004, 21(2): 161-165.  Abstract ( )   PDF (305KB) ( )   A method for generating three-dimensional mixed element type unstructured grids and its application for viscous flow simulations by solving the Navier-Stokes equations are presented.Pirzadeh's advancing-layer method is modified to generate high quality mixed prismatic/pyramid/tetrahedral element type unstructured grids in boundary-layer region,and the traditional advancing-front method is used to construct isotropic tetrahedral grids in the residual flow region.Three-dimensional Navier-Stokes equations are solved by using a cell-centered finite-volume method.A new local time stepping method has been developed to eliminate the adverse influence of grid quality on solve stability and convergence speed.Viscous flow problems around the ONERA M6 wing and DLR-F4 wing-body configuration are simulated to verify the correctness and practicability of the methods presented.

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Temperature Dependence of Exchange Bias and Coercivity in Ferromagnetic Layer Coupled with Antiferromagnetic Layer HU Jing-guo 2004, 21(2): 166-172.  Abstract ( )   PDF (299KB) ( )   The temperature dependence of exchange bias and coercivity of ferromagnetic layer and antiferromagnetic gain layer is discussed. In this model, the temperature dependence comes from the thermal instability of the system state and the temperature modulated relative magnetic parameters. These numerical results show that, at low temperature, the exchange bias and the coercivity decrease with increasing temperature, but the exchange bias becomes flat with increasing interface exchange coupling or decreasing ferromagnetic anisotropy. However, at high temperature the exchange bias become zero while the coercivity reach a peak, which are in good agreement with experimental results qualitatively. Based on our discussion, we can conclude that a soft ferromagnetic layer coupled by a hard antiferromagnetic layer with special exchange coupling may be very applicable to design magnetic devices, which with high exchange bias and low coercivity and almost independent of temperature.

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The Effect of Discharge Temperature upon Atomic Species in Plasma Nitriding of Steel Surface ZHANG Lian-zhu, Yu Fu-qiang, KONG Ling-yi, HE Qi 2004, 21(2): 173-178.  Abstract ( )   PDF (256KB) ( )   Based on a combination of Monte Carlo models of fast electrons and species(N2+,N+,Nr),Creation rates of atomic species(N+,N)and energy,density and angular distribution of species(N+,Nf)bombarding negative target in nitrogen dc discharge plasma-assisted nitriding of steel surface are investigated for e-+N2s→N++Ns+2e-及N21+N2s→N++Ns+N2.It is found that these is an optimum discharge temperature for the energy distribution of species(N+,Nf)at the cathode,creation rate and density of atomic species(N+,N)decreases with increasing temperature at steel surface,calculated results are generally in agreement with experimental ones.

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Distributed Parallel Method for the Transonic Flutter of Flexible Wings LIANG Qiang, YANG Yong-nian, FAN Ze-wen 2004, 21(2): 179-184.  Abstract ( )   PDF (352KB) ( )   Based on a distributed parallel computing system,a new approach to the transonic flutter of a flexible wing is presented by coupling the computational fluid dynamics (CFD) method with the computational structural dynamics(CSD)method. by using a transfinite interpolation(TFI) scheme to generate a multi-block C-H moving grid,the aerodynamic analysis is carried out by solving the three-dimensional unsteady Navier-Stokes equations. By coupling with the flutter motion equations,the response of the time history of generalized coordinates is found.The critical velocity is got on the base of the response. by considerally decreasing the computing time,a multidisciplinary analysis code runs on a distributed parallel computer system by using the PVM library.Computational results are presented for the transonic flutter of wings with deformed shapes as found in flutter simulations.

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STTDMR of Pseudo-random Number in Monte-Carlo Simulation SHUAI Yong, XIA Xin-lin, TAN He-ping, RUAN Li-ming 2004, 21(2): 185-188.  Abstract ( )   PDF (201KB) ( )   Pseudo-random number generator(PNG) is necessary in the computing works using Monte-Carlo method.The main error lies in the calculation of pseudo-random number to influence the accuracy of the calculation by the Monte-Carlo method.In this paper,a new more sufficient method through which one can hope a better outcome-the STTDMR (symmetry test in two dimension media radiation)is presented.The STTDMR is feasible under several of conditions to test unlimited the PNG.Good generators may be distinguished from bad ones more successfully in further level.The STTDMR is used to test not only properties of pseudo-random numbers but also the correctness of the probability models.In order to give a full view of the STTDMR,the STTDMR is applied to test several PNGs,and finally a PNG-ZH which is better than traditional PNG in many ways is obtained.