Ce:BaTiO3晶体中两个深陷阱能级引起的光折变光栅暗衰减特性

对Ce:BaTiO3晶体中光折变光栅的暗衰减特性进行了实验研究，观测到了晶体禁带中的Fe离子和Ce离子两个深陷阱能级同时参与了光折变过程。在单深能级模型和浅－深能级模型的基础上，提出了简化的双深能级模型，并根据该模型定量地分析了Fe离子和Ce离子每个深陷阱能级在不同光栅波矢、不同光栅写入光强时对总空间电场以及光折变光栅的贡献。     

模拟激光制导的实验设计

通过固定激光器，改变光学系统的状态，实现了模拟激光制导的目的。     

Application of time reversal in underwater communication

Time reversal is applied to the underwater spreading spectrum coding communication. On the base of analyzing the focusing characteristics of the time reversal in underwater waveguide, the time reversal is studied to overcome the wave distortion of the encoded signal caused by the multi-path effect. The experiment research for underwater coding communication is carried out in a lab water tank and the corresponding theoretical analysis is also conducted by Binary Phase Shift Keying (BPSK) encoding and Barker code with 7 chips for the spreading spectrum signal. The results show that the time reversal can improve the focusing gain and increase the ratio of the principal to the second lobe of the coding signal, and can decrease the bit error rate and increase the communication distance.     

Theoretical study on active control of sound radiation based on planar sound source

Active control of low frequency sound radiation using planar secondary sources is theoretically investigated. The primary sound field originates from a vibrating panel and the planar secondary sources are modeled as simply supported rectangular panels in an infinite baffle. The sound power of the primary and secondary panels is calculated, and then a series of formulae are derived to obtain the optimum reduction in sound power. Finally, active reduction for a number of secondary panel arrangements is examined, it is concluded that when the modal distribution of the secondary panel does coincide with that of the primary panel, one secondary panel is sufficient. Otherwise four secondary panels can guarantee considerable reduction in sound power over entire frequency range of interest.     

Enhancement of Supercontinuum Spectrum Generation in aDispersion-Decreasing Fibre with a Concave Dispersion Profile

A new approach is proposed to enhance supercontinuum (SC) spectrum generation in A dispersion-decreasingoptical fibre with a new dispersion profile. The chromatic dispersion D(λ, z) is a concave function of wavelengthsand has no zero-dispersion wavelengths over the whole or part of the fibre as D(λ, z) is positive. A flatter andmuch broader spectrum can be produced based on the scheme. The general criteria parameters are obtained forcharacterizing SC shapes in the optical fibres.     

有雨概率与分维数关系的初步研究

对武汉地区１９８２～１９９４年有雨分维数与有雨概率之间的关系进行了初步的分析和研究，并给出了研究结果．为今后修改降雨衰减预报模型作准备．     

具有衰减记忆的多维映射的逼近和系统识别

本文主要研究具有衰减记忆的多维映射的逼近，考虑了因果和非因果两种情形。在实际应用上，可以用来识别一类因果和非因果系统。     

一般各向异性复合材料层板基体损伤性能衰减研究（II）——分解 …

本文尝试将损伤复合材料层板性能衰减研究扩展到含一般各向异辅层的基体开裂层板，对第（Ｉ）部分提出分解刚度法给出分解刚度值确定方程，完整了开裂层板本构关系解，对（θｍ／９０ｎ）ｓ开裂层板刚度衰减了数值计算并对计算结果进行了讨论。     

主动光学成象系统衬比传递特性及有效作用距离的分析

从传输介质对照明和成象光束衰减作用(吸收和散射)的分析入手,通过细致的定量分析,得出了主动系统(包括同轴和非同轴两架)成象材比传模型.这些模型都是将系统参数和衬比联系起来的明确的等式,而且还给出了精度较好的简化模型.这些模型可以为定量分析介质对成象的影响和有关系统设计提供有效而方便的理论工具.     

电磁波在大气层人造等离子体中的衰减特性

利用洛沦兹模型来研究大气层人造非均匀等离子体的电磁响应特性,讨论了电磁波频率、等离子体密度及电子碰撞频率对电磁波衰减特性的影响.结果表明,电磁波在长波长区域及等离子体密度大时,其能量衰减越快.当等离子体密度高时,电子温度越低,大气层高度越高,电磁波的能量衰减越快. 关键词： 电磁波 大气等离子体 能量衰减