Acousto-optic modulation in magnetised diffusive semiconductors

The modulation of an intense electromagnetic beam induced by the acousto-optic (AO) effect has been analysed in a transversely magnetised semiconductor-plasma medium. The effect of carrier diffusion on the threshold field and gain profile of the modulated wave has been extremely investigated using coupled mode theory. The origin of the AO interaction is assumed to lie in the induced nonlinear diffusion current density of the medium. By considering the modulation process as a four wave parametric interaction an expression for effective third-order AO susceptibility describing the phenomena has been deduced. The modulation is greatly modified by propagation characteristics such as dispersion and diffraction due to dielectric relaxation of the acoustic mode. The threshold pump field and the steady state growth rates are estimated from the effective third-order polarisation in the plasma medium. Analytical estimation reveals that in the presence of enhanced diffusion due to excess charge carriers the modulated beam can be effectively amplified in a dispersionless acoustic wave regime. The presence of an external dc magnetic field is found to be favourable for the onset of diffusion induced modulational amplification of the modulated wave in heavily doped regime. Received 5 November 2001     

On the rate of convergence to equilibrium in the Becker-Döring equations

We provide an explicit rate of convergence to equilibrium for solutions of the Becker-Döring equations using the energy/energy-dissipation relation. The main difficulty is the structure of equilibria of the Becker-Döring equations, which do not correspond to a Gaussian measure, such that a logarithmic Sobolev-inequality is not available. We prove a weaker inequality which still implies for fast decaying data that the solution converges to equilibrium as e^−ct1/3.     

基于半导体光放大器交叉增益调制(SOA-XGM)波长变换器仿真研究

本文在PTDS(Photonic Transimission Design Suite)软件仿真平台上对基于半导体光放大器交叉增益调制(SOA-XGM)的波长变换器的变换特性作了仿真实验研究,仿真并分析了输入信号光功率、输入探测光功率、偏置电流和SOA的结构参量等因素对变换信号的消光比(ER)、Q值及误码率(BER)的影响关系.研究结果对优化设计SOA-XGM波长变换器有一定的参考价值.     

无直透光和共轭像的数字全息

根据数字全息的可计算特性，提出用图像处理的方法直接对数字全息图在空域进行预处理，使其再现时不出现直透光和共轭像，大幅度提高再现象的质量。并进行了实验验证。     

光电跟踪系统轴角编码与数字显示

介绍一种光电跟踪系统所采用的轴角编码与数字显示器。分析跟踪型轴角编码器的基本原理，探讨并提出了提高分辨率的具体方法，保证系统测角精度并可进行数字显示。     

Polymerization and photoinitiation behavior in the light-cured dental composite resins

The polymerization behavior and photoinitiation process in the visible light-cured dental composite resins were studied using ESR and IR spectroscopies. The concentration of methacryl propagating radical corresponded to the transmittance of irradiated light. While the radical was stable and long-lived in the cured resin, its concentration quickly decreased in the oral cavity due to the ventilation of atmospheric oxygen accompanied by respiration. Camphorquinone radical in the presence of tertiary amine easily initiated the radical polymerization. A decrease in monomer consumption was explained by the inhibition effect of oxygen in the photoinitiation process. Post-curing by the residual radical proceeded effectively in the deeper part of the resin.     

一种新的数字式多媒体图像采集系统

本文以多媒体概念为指导思想，论述了一种新的数字式多媒体图像采集系统。它采用多制式数字解码器、视频窗口控制器等超大规模集成电路芯片构成，较之以往的模拟式图像采集系统有本质区别     

提高大学物理实验教学质量的措施与设想

本提出了提高大学物理实验教学质量的一些措施与设想。并加以简要论述。     

一个新的凋亡抑制蛋白P49的表达及氨基酸序列分析

从海灰翅夜蛾核型多角体病毒（SpliNPV)中新发现的p49基因可抑制病毒感染引起的草地贪夜蛾细胞Sf9的凋亡，用杆状病毒表达系统Bac to Bac克隆表达并收获P49蛋白，发现所测定的表达蛋白的氨基酸序列与由核苷酸推导的氨基酸序列一致，证明p49基因经克隆转染后得到正确表达，P49蛋白上－^91TVTDG^95－氨基酸序列为Caspase识别结构，比较P35与P49蛋白，两蛋白同源性约为48．8％，且都具Caspase识别和切割的氨基酸序列。