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The electromagnetic propagation process of a Gaussian pulse through an unmagnetized plasma photonic crystal is investigated.

它具有一定的光子能带结构，一定频率的光不能在晶体中传播，从而产生了光子禁带。

Based on the method that a rectangular function can be expanded into a sum of complex Gaussian functions with finite numbers, the propagation characteristics of a Gaussian beam passing through apertured spatial filter systems are analysed and the corresponding analytical formulae are obtained respectively.

根据矩形函数可以展开为有限复高斯函数之和的方法，从柯林斯衍射积分公式出发，对高斯光束通过受限空间滤波器传输特性进行分析，得到了相应的近似解析式。利用Matlab对其解析式进行数值模拟，得出一组直观的结果。

Base on the fact that a hard-edge aperture function can be expanded into a finite sum of complex Gaussian functions, the approximate analytical expressions for the propagation characters of Hermite-Guassian beams passing through double rectangular apertured are derived. The approximate analysis uses Collins formula. At last, Matlab illustrates some numerical examples.

基于硬边孔函数能拓展成一组有限复高斯函数的和，研究厄米－高斯光束通过双矩孔的传输特性，用Collins公式分析，用Matlab进行一些数值模拟。

The propagation equations for oblique and off-axial Gaussian beams passing through cat-eye optical lens are deduced by using the theory of matrix optics and expanding the aperture function into a finite sum of complex Gaussian functions.

运用矩阵光学理论以及将硬边光阑窗口函数展开为有限个复高斯函数之和的方法，进一步推导了倾斜离轴高斯光束通过猫眼光学镜头的解析传输公式，通过数值计算分析得到了倾斜系数和离轴量对猫眼效应反射光光强分布的影响规律。

Gaussian beam propagation thus bridges the gap between geometric and physical optics.

高斯光束传播理论因此可以沟通几何光学与物理光学。

By treating photorefractive spatial soliton as rays in geometric optics, the action of the diffusion effect on propagation of PR spatial solitons is analyzed.

把光折变空间孤子看作几何光学中的一束光线，研究了扩散效应对光折变空间孤子传播的影响。

In the text, the Spectral element method is used to model the seismic wave propagation, which is based on a weak formulation of the elastic mechanics equation. It combines the geometrical flexibility of the Finite element method and the accuracy of the pseudospectral method.

本文采用谱元法对横向同性介质中的地震波进行模拟，该方法基于弹性力学方程弱形式基础之上，具有有限元适应任意复杂介质模型的韧性和伪谱法的精度。

Week 8 - Geometrical optics, wave propagation 1 hr, in class

第八周－几何光学、波的传播

The GKS stability theorem for one-dimensional model of hyperbolic initial and boundary value problem, Trefethen's explanation and extension based on the concept of group velocity are generalized firstly. Another possible high-frequency instability mechanism in numerical realization of MTF is pointed out based on his explanation and extension, namely, coupling effect of outgoing harmonic wave along one direction and node motion in the other directions can reverse the energy propagation in multi-dimensional discrete grids.

本文概述了—维双曲型偏微分方程组初边值问题数值稳定性的GKS定理及Trefethen基于群速度概念对这一定理的解释和推广；并应用Trefethen的解释和推广指出了MTF在数值实现中可能出现的另一种高频失稳机制，即在多维离散网格中，沿某一空间方向的外行简谐波，由于与其他空间方向节点运动的耦合效应可以使能量传播方向反向。

On one hand, the grain boundaries are the sites of microcrack nucleation, microcracks first occur at grain boundary zone, whose propagation type depends on lamellar orientation of both side of grain boundary.

一方面，微裂纹首先萌发于晶界区，其扩展方式取决于晶界两侧片层的取向。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。