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25 September 1998, Volume 15 Issue 5 Previous Issue    Next Issue

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THE ADAPTIVE FINITE ELEMENT METHODS AND A POSTERIORI ERROR ESTIMATES Yu Xijun, Yu Dehao, Bao Yuzhen 1998, 15(5): 513-530.  Abstract ( )   PDF (678KB) ( )   The adaptive finite element methods are very effective for solving partial differential equations in scientific researches and engineering designs.By using these methods the best possible results can be obtained at less computational costs.A posteriori error estimates serve as a key to realize the adaptive finite element computation.This paper surveys the progress in the adaptive finite element methods and a posteriori error estimates for solving elliptic equations,parabolic equations and hyperbolic equations.

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A HIGH ORDER ACCURATE UPWIND COMPACT SCHEME WITH GROUP VELOCITY CONTROL FOR SOLVING HYPERBOLIC CONSERVATION LAWS Zhu Qingyong, Ma Yanwen 1998, 15(5): 531-536.  Abstract ( )   PDF (234KB) ( )   A high order accurate finite difference scheme is proposed in light of the upwind compact method[1].The flux vectors in Euler equations are approximated by using upwind compact difference.In order to prevent the nonphysical oscillations in the vicinity of the shock the group velocity control(GVC)method is used.The reason of oscillation production in numerical solutions is nonuniformity of group velocity of wave packets.GVC is for improvement of the shock resolution.The present scheme has third order accruracy in smooth regions.

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ANALYSIS OF THE CONVERGENCY CHARACTERISTICS OF SIMPLE ALGORITHM WITH THE CHOICES OF DEPENDANT VARIABLES AND CELL-FACE VELOCITY Lai Huanxin, Wu Keqi 1998, 15(5): 537-546.  Abstract ( )   PDF (391KB) ( )   With the choices of dependant variables and cell face velocity, the convergency speed and computational accuracy of SIMPLE algorithm employed in the computation of complex flows are analyzed. The mistakes of basic concepts found in literature are corrected, and a method whose good effects in improving the algorithm showed by numerical tests, is put forward.

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INVESTIGATIONS AND APPLICATIONS OF ADVANCED UPWIND SCHEME (AUSM+) Chen Liang, Yan Chao 1998, 15(5): 547-552.  Abstract ( )   PDF (265KB) ( )   Through comparing different results of simulating shock reflection flow over a forward step using different schemes including Roe and van Leer schemes,the advanced upwind scheme (AUSM+) is fully studied in terms of its resolution and efficiency for shock waves,expansion vaves,contact discontinuities and their interactions.Its advantages of low numerical dissipation and high resolution for discontinuities are demonstrated.

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ANGULAR DISTRIBUTIONS OF ELECTRONS IN THE (e,2e) REACTION Jia Xiangfu, Chen Zhangjin, Xu Kezun 1998, 15(5): 553-558.  Abstract ( )   PDF (244KB) ( )   The triple differential cross sections (TDCS) in coplanar equal energy sharing and fixed relative angle geometry for electron impact ionization of He+ are calculated (by using a modified BBK model) at incident electron energies of 58.4,68,81.6,108.8 and 174.4 eV.Dominant ionization mechanisms are identified and the contributions of different scattering amplitudes are discussed.It concludes that Coulomb interaction in the initial channel,exchange effects,correlation and the coherence between electron electron and electron nucleus scattering are all important at these energies.

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THE STABILITY ANALYSIS FOR THE INVERSE PROBLEM OF ONE DIMENSIONAL ACOUSTICS WAVE EQUATIONS Hao Xianjun, Zhu Benren, Zhang Guanquan 1998, 15(5): 559-567.  Abstract ( )   PDF (315KB) ( )   The inverse problem for the one-dimensional acoustic wave equations is discussed.For the inverse problem to determine acoustic impedance from impulse response,sufficient condition and necessary condition are obtained for the wellposedness.These conditions are very simple and can be verified easily in numerical computation.For the inverse problem to determine acoustic impedance from wavelet response,it's usually illposed.The detailed analysis indicates that the more smooth the wavelet is,the more illposed the inverse problem is.

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THE BLOCK TWO STAGE MULTISPLITTING ITERATIVE METHOD Liu Xingping, Lei Guangyao, Xu Tao 1998, 15(5): 568-576.  Abstract ( )   PDF (297KB) ( )   On the basis of pseudo elimination (PE) approach,the algorithm of the block two stage multisplitting (TSM) interative method for linear systems of the form Ax=f is proposed,when A is block tridiagonal matrix.The resulting multisplitting pseudo elimination(MPPE) method has been tested on a Challeng-L and power PC Cluster computer.Numerical examples are also given.

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IMPROVED FITTING FORMULAS OF RATE COEFFICIENT OF ELECTRON-ION COLLISIONAL IONIZATION Teng Zhouxuan, Chen Chongyang, Wang Yansen 1998, 15(5): 577-580.  Abstract ( )   PDF (163KB) ( )   The computation on the rate coefficient of electron ion collisional ionization is described and some fitting formulas are given for the accurate and fast calculation.

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THE COMPARATIVE ANALYSIS OF THE POWER SPECTRA TO THE CARDIOELECTRICAL SIGNALS AMONG DIFFERENT SPECIES Wang Xingyuan, Zhu Weiyong 1998, 15(5): 581-586.  Abstract ( )   PDF (264KB) ( )   The chaos in human body provides a sort of healthy adaptability, it seems to be the reflection of selection and adaptability in the process of the evolution of the life. Then, can the chaos be regarded as a motive power of the process of the evolution of species? In answer to this, the experiments have been conducted on sample cardioelectrical signals of human being and the canines, Through the analyses of the power spectra to a large of cardioelectrical signals, the following conclusions are shown:(1) The analyses of the power spectra to cardioelectrical signals reflect the whole dynamic characteristics of the heart, it may become a new method as a sort of quantitative researches on eletrocardiogram to early diagnose the heart disease. (2) Under normal physiological conditions the cardiac activities are chaotic, however under pathologic conditions the cardiac activities approach regularity. (3) On the basis of the comparative research of human being and the canines, the hypothesis is proposed that chaos would become more significant in the warke of the evolution of species. If the hypothesis is right, it would be a beginning of the new theory on the evolution of species.

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STUDY ON THE OPTIMIZATION IN CHARGED PARTICLE OPTICAL SYSTEM Lei Wei, Yin Hanchun, Tu Yan 1998, 15(5): 587-594.  Abstract ( )   PDF (305KB) ( )   It studies the optimization of charged particle optical system and proposes to separate the optimization of aberration from the optimzation of field in lens. In the optimization of aberration, the implication constraints are considered. In this optimization, it needs to do some simple integral calculations so that the calculation of field which will takes a lot of time is avoided. In the optimization of filed in lens, the mathmatical model is just the same as in other electromagnetic system. Therefore, the optimzation methods of electromagnetic system can be used to optimize the field in lens. In the end, two examples for optimization are given to verify the new method.

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ELECTRON BEAM DENSITY MODULATION IN SR-FEL Yang Zhenhua, Wu Yupu 1998, 15(5): 595-599.  Abstract ( )   PDF (204KB) ( )   The computation is clarified for the electron beam density modulation in optical klystron on storage ring free electron laser with three different methods,and the effects of electron beam parameters on density modulation are also studied.The numerical results show that the three dimensional simulation is necessary.

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THE CALCULATION AND DISCUSSION OF DETAILED PHOTOIONIZATION AND RADIATIVE RECOMBI-NATION RATE COEFFICIENTS Li Yueming, Li Shichang, Han Guoxing 1998, 15(5): 600-606.  Abstract ( )   PDF (308KB) ( )   The corrected Gramm-Schmidt method is employed in 3-splined fitting of photoionization cross sections which was calculated in the authors previous work.In the case of LTE approximation,photon and free electron are assumed to be in Planck and Maxwell distribution respectively.The present derivation shows that,the rate coefficients of photoionization and radiative recombination can be described analytically in terms of 3-splined fitting parameters.This formulation is applied to He-like Rb and He-like Nb ions,and some of the results are figured out and analysed.By means of averaging over initial states and summing over final states,the degeneration of rate coefficients that concern the level level transitions is analysed explicitely.With the attained result, comparison and evaluation have been made to the formula given by reference[1].

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AN ALTERNATING GROUP EXPLICIT ITERATION METHOD FOR BURGERS EQUATION Jin Chengri, Liu Jiaqi 1998, 15(5): 607-613.  Abstract ( )   PDF (238KB) ( )   An alternating group explicit iteration method of high accuracy is constructed for solving Burgers equation on the basis of physical sense of convection speed,and its stability and convergence are analysed by the linear method.Numeical results of the model problem are given.

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NUMERICAL ANALYSIS OF EFFECT OF MACRO-VELOCITY ON HELICAL INSTABILITY OF ARCS Gong Ye, Zhang Pengyun, Liu Yuhong, Ma Tengcai 1998, 15(5): 614-619.  Abstract ( )   PDF (217KB) ( )   The helical instability of an arc column with electrical conductivity of the parabolic distribution and macro velocity is discussed in an axial magnetic field. The magnetohydrodynamic equations serve as the starting point of the theory, in an electrostatic approximation and a linear time dependent perturbation theory, the perturbation equations for the arc column movement are deduced. Solutions of these equations are obtained analytically, from which the stability limit of the cylindrical arc and the growth rate of the helical instability are given.

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LINE-BY-LINE CALCULATION MODEL OF RADIANCE AND TRANSMITTANCE FOR THE NON-EQUILIBRIUM ATMOSPHERES Zhu Shide, Xiang Anping 1998, 15(5): 620-628.  Abstract ( )   PDF (328KB) ( )   The basic formulas of the emission and transmission for non-local thermodynamic equlibrium(NLTE)planetary atmospheres are derived.By assuming that rotational levels within a vibrational level remain in thermodynamic equilibrium,an accurate and efficient line-by-line algorithm of NLTE emission and transmission is developed to evaluate the radiance due to infrared active species in the upper planetary atmospheres.The limb viewing spectral radiance,line integrated radiance,band integrated radiance and synthetic spectral radiance of the Earth's atmosphere for the 9.6μm bands of 16O3 under daytime and nighttime and under NLTE and LTE conditions are calculated by using this algorithm.The results of calculations reveal that NLTE radiance obviously departs from LTE.

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NUMERICAL RESEARCH OF HEAD WAVE IN A FLUID-FILLED BOREHOLE SURROUNDED BY A POROUS MEDIUM Luo Chaosheng, Dong Qingde, Wang Kexie 1998, 15(5): 629-634.  Abstract ( )   PDF (240KB) ( )   Through the computer numerical experiment, it systematically studies the excitation and propagation properties of the head-wave in a borehole surrounded by a porous medium,and proves that the head-wave has the property of resonance and attenuation. However it is evidently different from the head-wave in an oil well surrounded by homogeneous medium. The attenuation of the resonance peak amplitude appears first insreasing and then decreasing when the resonance frequency increases. The reservoir parameters——porosity (φ) and permeability (κ) of the porous medium have few influence on resonance frequency. But they have an evident effect on resonance peak amplitude, Which decrease when the porosity (φ) and the permeability (κ) become larger.

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CALCULATIONS OF TRIPLE DIFFERENT IAL CROSS SECTIONS FOR ELECTRON IMPACT IONIZATION OF IONS Chen Zhangjin 1998, 15(5): 635-640.  Abstract ( )   PDF (245KB) ( )   For calculating integrals involving four confluent hypergeometric functions, a general theoretical method is presented, which is valid for both symmetric and asymmetric geometries to determine the triple differential cross sections (TDCS) for electron impact ionization of ions. The TDCS for the ionization of hydrogenic ion at high and intermediate energies have also been calculated and compared with the existing theoretical results.