THE COUPLING OF NATURAL BOUNDARY ELEMENT AND FINITE ELEMENT METHOD FOR 2D HYPERBOLIC EQUATIONS

In this paper, we investigate the coupling of natural boundary element and finite element methods of exterior initial boundary value problems for hyperbolic equations. The governing equation is first discretized in time, leading to a time-step scheme, where an exterior elliptic problem has to be solved in each time step. Second, a circular artificial boundary FR consisting of a circle of radius R is introduced, the original problem in an unbounded domain is transformed into the nonlocal boundary value problem in abounded subdomain. And the natural integral equation and the Poisson integral formula are obtained in the infinite domainΩ2 outside circle of radius R. The coupled variational formulation is given. Only the function itself, not its normal derivative at artificial boundary ΓR, appears in the variational equation, so that the unknown numbers are reducedand the boundary element stiffness matrix has a few different elements. Such a coupled method is superior to the one based on direct boundary element method. This paper discusses finite element discretization for variational problem and its corresponding numerical technique, and the convergence for the numerical solutions. Finally, the numerical example is presented to illustrate feasibility and efficiency of this method.     

约束Hamilton系统的Poincaré-Cartan不变量

从正则形式作用量出发,导出了约束Hamilton系统(奇异拉氏量)的Poincaré-Cartan不变量,证明了该不变量与约束Hamilton系统的正则方程之间的等价性,纠正了某些作者工作中的错误。     

深能级杂质对光导半导体开关非线性特性的影响

建立了非线性GaAs光导开关深能级杂质瞬态模型的基本方程,获得了与实验现象定性吻合的电流输出,给出了平均载流子随时间演化的情况.分析结果表明,在考虑了深能级杂质的俘获、发射和碰撞电离后,有可能对非线性光导开关中发生的一系列现象做出解释,进一步的仔细分析将对非线性光导开关的设计和制作提供理论指导.     

Sound Field Calculations of Elliptical Pistons by the Superposition of Two—Dimensional Gaussian Beams

We present an alternative approach to calculate the sound field of ultrasonic transducers.The distribution function of sources is expanded into the superposition of a series of two-dimensional Gaussian functions.The corresponding radiated sound field is expressed as the superposition of these two-dimensional Gaussian beams and is then reduced to the computation of these simple functions.This treatment does not require the condition that the shape of the source is of circular axial symmetry.A numerical example is presented for the uniform elliptical piston transducer and this is in good agreement with the results given by complicated computation.     

关于含非凸约束的变化问题

本文分别讨论泛函Ｉｐ（ｕ）＝∫Ω｛「α＾αβ（ｘ，ｕ）ｇｉｊ（ｘ，ｕ）Ｄαｕ＾ｉＤβｕ＾ｉＤβｕ＾ｊ」＾ｐ／２＋Ｐ（ｘ，ｕ）｝ｄｘ，在一般的非凸几何约束Ｆ１＝｛ｕ∈Ｈ＾１，ｐ（Ω，Ｒ＾Ｎ）；ｕ∈Ｍａ．ｅ．于Ω，ｕ│δΩ＝ｕ０｝和非凸图约束下的极小化问题，其中Ｍ为Ｒ＾Ｎ中的任一光滑开子集或Ｒ＾Ｎ的一个开子流形。     

广义拓扑分子格中分子网的θ—收敛性

本文在广义拓扑分子格中建立了分子网的Ｍｏｏｒｅ－Ｓｍｉｔｈθ收敛理论。借助于此理论，我们得到了刻划弱连续序同态的三个特征定理。     

一类广义差分方程组与CDS方法的收敛性

本文首先证明了基于 ILMM 的 CDS 格式是不收敛的,然后对一类广义差分方程组给出了解的估计式,最后,在这个基础上,对基于 IMLMM 的 CDS 格式建立了收敛性定理,给出的收敛阶也是最佳的。     

L-带行波电子直线加速器束流动力学计算

本文以自由电子激光(FEL)用L-带行波电子直线加速器的注入器为例,用增补后的PARMELA程序对其作了束流动力学的三维计算,并给出了有关束流性能的各种参量.     

玻璃波导光功分器的研制

本文报道了Na^ —Tl^ 离子交换的K9玻璃衬底光功分器（工作波长为1.55μm），分析设计和器件的制作，并对制作的器件进行了模式损耗测试。结果表明，器件达到了预定的要求。