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981.
A numerical solution method for two-dimensional electromagnetic field problems is presented using the B-spline finite-element expression based on polar coordinates. The technique has two main advantages: (1) to avoid the truncation errors at some curved boundaries and (2) to improve the accuracy of singular boundary-value problems with a sharp corner. The B-spline finite-element formulation in polar coordinates is derived and its numerical applications are illustrated by an eddy current problem and several waveguide eigenvalue problems. 相似文献
982.
本文应用双极坐标系中的弹性力学相容方程,获得了受对称荷载作用且τξη=0情况下半圆盘的应力解答。运用所得公式,分析了预应力钢丝缠绕式压机中半圆盘形梁等实例。 相似文献
983.
韩玉英 《中国科学B辑(英文版)》1992,(1)
According to the peculiarities of tectonodeformation this paper systematically researches the graphic method of finite strain theory in tectonomechanics, proposes a geometrical analytic method describing the strain state of a point with metric tensor, expounds and proves the structure of deformation gradient circle, and clearly illustrates the relations of various quantities in polar decomposition theory. Finally, a simple shear deformation which often occurs in tectonodeformation was calculated through various different methods in order to explain and to compare the peculiarities among various graphic methods of finite strain. 相似文献
984.
Wen LI~ 《中国科学A辑(英文版)》2007,(9)
In this paper,we study the perturbation bounds for the polar decomposition A=QH where Q is unitary and H is Hermitian.The optimal (asymptotic) bounds obtained in previous works for the unitary factor,the Hermitian factor and singular values of A areσ_r~2||ΔQ||_F~2≤||ΔA||_F~2, 1/2||ΔH||_F~2≤||ΔA||_F~2 and ||Δ∑||_F~2≤||ΔA||_F~2,respectively,where∑=diag(σ_1,σ_2,...,σ_r,0,...,0) is the singular value matrix of A andσ_r denotes the smallest nonzero singular value.Here we present some new combined (asymptotic) perturbation boundsσ_r~2||ΔQ||_F~2 1/2||ΔH||_F~2≤||ΔA||_F~2 andσ_r~2||ΔQ||_F~2 ||Δ∑||_F~2≤||ΔA||_F~2 which are optimal for each factor.Some corresponding absolute perturbation bounds are also given. 相似文献
985.
In this paper, we extend our previous work (M.-C. Lai, A simple compact fourth-order Poisson solver on polar geometry, J. Comput. Phys. 182 (2002) 337–345) to 3D cases. More precisely, we present a spectral/finite difference scheme for Poisson equation in cylindrical coordinates. The scheme relies on the truncated Fourier series expansion, where the partial differential equations of Fourier coefficients are solved by a formally fourth-order accurate compact difference discretization. Here the formal fourth-order accuracy means that the scheme is exactly fourth-order accurate while the poles are excluded and is third-order accurate otherwise. Despite the degradation of one order of accuracy due to the presence of poles, the scheme handles the poles naturally; thus, no pole condition is needed. The resulting linear system is then solved by the Bi-CGSTAB method with the preconditioner arising from the second-order discretization which shows the scalability with the problem size. 相似文献
986.
In this paper, we consider moving coordinates with a speed determined by the wave speed. This allows us to move the coordinates at the speed of contact discontinuities, expansion fans, or other wave structures. While recognizing that the Lagrangian coordinates, which can well resolve the sliplines, behave badly for expansion waves, we demonstrate that a coordinate system moving at the characteristic speed of the expansion fan behaves much better for expansion waves. Moreover, the new coordinate system allows one to well capture the shock wave, the slipline and the expansion waves at the same time. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
987.
Simultaneous observations at Zhongshan Station, Antarctica, during May 1-7, 1998 are presented to show the responses of the polar ionosphere to the April/May 1998 solar events. One of the main geo-effects of the solar events resulted in the major magnetic storm on May 4. At the storm onset on May 2 the ionosphere F2 layer abruptly increased in altitude, the geomagnetic H-component started negative deviation and the spectral amplitude of the ULF wave intensified. Both large isolated riometer absorption and large negative deviation of the geomagnetic H-component occurred at about 0639UT. There was a time lag of about one hour and ten minutes between the storm onset and the IMF southward turning, as measured by the WIND satellite. The polar ionosphere was highly disturbed, as shown by frequent large deviations of the geomagnetic H-component, large riometer absorption events and strong ULF waves in all the courses of the storm. The absorption increased greatly causing the digisonde to be blackout most of the time. However, the data still showed a substantial decrease in the F2 electron density and oscillation of the F2 layer peak height with an amplitude exceeding 200 km. 相似文献
988.
超球坐标下Li原子基态能量的快速收敛计算 总被引:1,自引:0,他引:1
将Li原子2S态的波函数分解为两项之积,ψ=XΦ,X=exp[-α(r1+r2+r3)],而Φ向以九维超球谐为投影函数而构造的S3置换群的二维不可约表示的基函数展开。Schrodinger方程转化为一起球径耦合微分方程。再利用广义Laguerre函数展开法对其求解,从而得到一广义能量本征方程,给出了库仑势及有关超球角函数在非对称九维超球谐之间矩阵元的简单解析式,可由一起几何函数4F3:(A,B,C,D;E,F,G;1)的线性组合表示。取超球谐函数的子集(l1=l2=l3=0),基态12S的本征能量在超球角方向的收敛速度加快,首次用非变分法得到了优于Hartree-Fock精度的基态能量。结果表明本文给出的方法是对直接超球谐广义Laguerre函数展开法(HH-GLF)的一个非常有效的改进。 相似文献
989.
990.
We define certain extensions of affine Weyl groups (distinct from these considered by K. Saito [S1] in the theory of extended affine root systems), prove an analogue of Chevalley Theorem for their invariants, and construct a Frobenius structure on their orbit spaces. This produces solutions F(t1, ..., tn) of WDVV equations of associativity polynomial in t1, ..., tn-1, exp tn. 相似文献