The numerical solution of an inverse periodic transmission problem

We consider the inverse problem of recovering a 2D periodic structure from scattered waves measured above and below the structure. We discuss convergence and implementation of an optimization method for solving the inverse TE transmission problem, following an approach first developed by Kirsch and Kress for acoustic obstacle scattering. The convergence analysis includes the case of Lipschitz grating profiles and relies on variational methods and solvability properties of periodic boundary integral equations. Numerical results for exact and noisy data demonstrate the practicability of the inversion algorithm. Copyright © 2004 John Wiley & Sons, Ltd.     

x射线在毛细导管中传输的模拟计算

阐述了x射线在毛细导管中传输的基本理论，根据光线追迹原理建立了x射线在毛细导管中传输的计算模型.在此基础上使用MATLAB编写程序，实现了对x光经过x光单导管的传输效率和光强分布的模拟计算.计算结果和实验数据进行比较，得到了很好的符合. 关键词： 模拟计算 毛细导管 光线追迹 传输效率 光强分布     

信道自适应主动块丢弃数字图像传输技术

数字图像的高效传输对于无线多媒体通信和网络图像交换等应用具有十分重要的意义。信道自适应主动块丢弃数字图像传输技术，在图像发送端以块为单位对图像进行划分，按照一定的规则主动丢弃部分图像块数据，以此减少所需要传输的比特流量，满足信道带宽要求，而在图像接收端通过全新的图像重建技术对丢弃的图像块数据进行恢复，从而完整地再现原图像。大量实验证明，该图像传输技术优于目前普遍采用的量化步长调节式数字图像传输技术，用它传输的图像质量得到明显提高。     

基于C8051F的电量测量与传输系统

介绍一种利用高速51系列单片机C8051F020组成的电量测量及数据传输系统,系统能比较实时准确地监测三相电压、电流、功率、电能和功率因数等。详细介绍了频率、相位差的测量原理和A/D转换,以及系统所需电源的电路设计。并且讨论了几种数据传输的方式:RS 485通信、CAN通信及GPRS通信。此系统可以用于电力系统中家庭用户以及变压器的远程电量监测。     

Optimal Security Liquidation Algorithms

This paper develops trading strategies for liquidation of a financial security, which maximize the expected return. The problem is formulated as a stochastic programming problem that utilizes the scenario representation of possible returns. Two cases are considered, a case with no constraint on risk and a case when the risk of losses associated with trading strategy is constrained by Conditional Value-at-Risk (CVaR) measure. In the first case, two algorithms are proposed; one is based on linear programming techniques, and the other uses dynamic programming to solve the formulated stochastic program. The third proposed algorithm is obtained by adding the risk constraints to the linear program. The algorithms provide path-dependent strategies, i.e., the fraction of security sold depends upon price sample-path of the security up to the current moment. The performance of the considered approaches is tested using a set of historical sample-paths of prices.     

一种分析三维楔脊形光波导与光纤耦合的方法

和直波导的不同在于，三维楔脊形波导中的光场都是不稳定的.分别对波导-光纤耦合、光纤-波导耦合两种情况，将三维楔脊形波导等效为多段短的直波导，利用束传播法同时对三维楔脊形波导内不稳定的入射、反射场，及它们在传播方向上的偏导进行处理，再用自由空间辐射模法计算透射率和反射率.以SOI楔脊形波导和光纤的耦合为例，验证了该方法的可行性. 关键词： 自由空间辐射模法 束传播法 耦合 透射 楔脊形光波导 绝缘体上硅(SOI)     

宽带网络流媒体技术的应用与发展

流媒体技术是在数据网络上以流的方式传输多媒体信息的技术。近年来,随着宽带网络的发展和用户需求的驱动,流媒体技术和相关的应用得到越来越多的关注,被认为是未来高速宽带网络的主流应用之一。文中介绍了流媒体的概念与特点,深入分析了流媒体系统及其关键技术,研究了流媒体技术在宽带网络中的应用及在国内外的发展情况,对流媒体技术在发展中遇到的问题做了说明。还针对国内目前的宽带网络现状提出了流媒体技术的应用和发展建议。     

流媒体技术及其应用

流媒体技术在人们不断追求高速、高效和高质量的网络传输的愿望中逐渐产生,并在网络技术的完善中不断发展。介绍了流媒体的概念,并对目前流媒体的主流格式做了分析,同时对支持它的网络协议做了全面的阐述,并对流媒体的主要应用和它带来的好处做了简要说明。     

安徽电信宽带骨干传输网构建方案介绍

随着IP业务的超常规发展，传输瓶颈日渐显现出来；以安微电信骨干传输网的发展规划为例，介绍安微电信宽带骨干传输网的构建方案。     

Study on stacking faults and microtwins in wide bandgap II-VI semiconductor heterostructures grown on GaAs

ZnMgSSe and ZnSSe layers grown on GaAs substrates with GaAs buffer layers by molecular beam epitaxy have been examined by transmission electron microscopy (TEM). The depth level at which paired triangular stacking faults are nucleated in the ZnMgSSe/GaAs heterostructure has been investigated by using the plan-view TEM technique. It has been found that in the ZnMgSSe/GaAs heterostructure the nucleation of the paired stacking faults occurs within a range of depth which starts at the II-VI/GaAs interface and ends at a level that is above the interface by about 120 nm. The dominant type of defects in ZnSSe layers, which have the single triangular shape, has been identified to be microtwins by high resolution TEM.