INITIAL VALUE TECHNIQUES FOR THE HELMHOLTZ AND MAXWELL EQUATIONS

We study the initial value problem of the Helmholtz equation with spatially variable wave number. We show that it can be stabilized by suppressing the evanescent waves. The stabilized Helmholtz equation can be solved numerically by a marching scheme combined with FFT. The resulting algorithm has complexity n^2 log n on a n x n grid. We demonstrate the efficacy of the method by numerical examples with caustics. For the Maxwell equation the same treatment is possible after reducing it to a second order system. We show how the method can be used for inverse problems arising in acoustic tomography and microwave imaging.     

A Series of Exact Solutions of (2+1)-Dimensional CDGKS Equation

An algebraic method with symbolic computation is devised to uniformly construct a series of exact solutions of the (2 1)-dimensional Caudrey-Dodd-Gibbon-Kotera-Sawda equation. The solutions obtained in this paper include solitary wave solutions, rational solutions, triangular periodic solutions, Jacobi and Weierstrass doubly periodic solutions. Among them, the Jacobi periodic solutions exactly degenerate to the solutions at a certain limit condition. Compared with most existing tanh method, the method used here can give new and more general solutions. More importantly, this method provides a guideline to classify the various types of the solution according to some parameters.     

The energy exchange and the optimum length of the sample tube of opfirl

The energy exchange between the pumping laser and FIR signal in the optically pumped FIR laser (OPFIRL) system was studied. The iteration method has been used to calculate the power density of the pumping and FIR signals at any point along the optical axis of the sample tube. It was found that the power density of the FIR signal did not always increase along the length of the laser tube. There was a maximum FIR power density at the appropriate point in the sample tube. If the distance of maximum power point from the entrance of the OPFIRL tube was taken as the length of sample tube Z_opt, the maximum FIR laser output should be obtained. This was the optimum length of OPFIRL tube. The value of Z_opt was closely related to the parameter of OPFIRL such as the pumping power density, the pumping detuning and the frequency of the FIR laser. The energy-exchange and the maximum output of the fir laser were calculated under the ideal condition.     

等离子体中电磁波的粒子模拟

本文介绍了1 2/2维相对论性、电磁模等离子体粒子模拟的方法和原理。系统地以计算机模拟了由电子气体组成的等离子体中的各种电磁波。在无外加静磁场、加外横磁场、加外纵向磁场等不同情况下,分别得到静电波、电磁波、寻常波、非寻常波、ω=nω_c的磁回旋共振、左旋波、右旋波等。其色散关系、截止频率、共振频率、极限相速度均与理论结果一致。     

热效应对光折变晶体两波耦合的特性影响的理论分析

用一种模型对两波耦合进行了分析，导出了强度相位的解析式，对影响两波耦合的参数进行了理论分析。分析了对ＢａＴｉＯ３光折变晶体的两波耦合的测量结果。     

运用严格耦合波理论计算平面电介质光栅的衍射效率

本文阐述了严格耦合波理论的基本思想。针对横电波的情况，详细分析了运用严格耦合波理论实现光栅衍射效率计算的方法，并且进一步给出了编制计算衍射效率程序的步骤。通过一个具体计算实例表明：各衍射级分布的光能量之和等于入射光的能量，满足能量守恒定律，从而证实了计算结果的正确性。     

组合原则回溯

从组合原则产生的背景和关键入手，分析和叙述了里兹的组合原则在光谱学上的重要意义，同时，也阐述了它与玻尔氢原子理论之间的关系。     

Theoretical analysis on waveform structures of pulse propagating in shallow water with an ideal thermocline

I.IntroductionDuetospatia1andtemporalvariabilityoftheocean-acousticenvironment,especially,theeffectsofboundaryaswel1asmediumonpropagationofacousticwavesinshal1owwater,theacousticpropagationisextrcmelycomp1icatcd.Multipathtransmissionisthebasiccharacteris-hcsofunderwatersoundchannels.Undctcrminedmultipathstructurescangreatlylimittheperformanceofunderwateracousticdetcction.However,ifthemultipathcharacteristicsofacousticpropagationinunderwatcrsoundchanne1sareknown,spaee-timeresolutionandpro-cess…     

冲击波处理的结晶MgO的化学分析正电子谱研究

冲击波处理的结晶ＭｇＯ的化学分析正电子谱研究＊张菊郑小明（杭州大学催化研究所，杭州３１００２８）常志向（抚顺石油化工研究院，抚顺１１３００１）关键词冲击波，化学分析正电子谱，结晶氧化镁，丁烯，脱氢冲击波是在介质中以超音速传播的压力脉冲．气体中的冲击波...