Issues in Optical Diffraction Theory

This paper focuses on unresolved or poorly documented issues pertaining to Fresnel’s scalar diffraction theory and its modifications. In Sec. 2 it is pointed out that all thermal sources used in practice are finite in size and errors can result from insufficient coherence of the optical field. A quarter-wave criterion is applied to show how such errors can be avoided by placing the source at a large distance from the aperture plane, and it is found that in many cases it may be necessary to use collimated light as on the source side of a Fraunhofer experiment. If these precautions are not taken the theory of partial coherence may have to be used for the computations.In Sec. 3 it is recalled that for near-zone computations the Kirchhoff or Rayleigh-Sommerfeld integrals are applicable, but fail to correctly describe the energy flux across the aperture plane because they are not continuously differentiable with respect to the assumed geometrical field on the source side. This is remedied by formulating an improved theory in which the field on either side of a semi-reflecting screen is expressed as the superposition of mutually incoherent components which propagate in the opposite directions of the incident and reflected light.These components are defined as linear combinations of the Rayleigh-Sommerfeld integrals, so that they are rigorous solutions of the wave equation as well as continuously differentiable in the aperture plane. Algorithms for using the new theory for computing the diffraction patterns of circular apertures and slits at arbitrary distances z from either side of the aperture (down to z = ± 0.0003 λ) are presented, and numerical examples of the results are given. These results show that the incident geometrical field is modulated by diffraction before it reaches the aperture plane while the reflected field is spilled into the dark space. At distances from the aperture which are large compared to the wavelength λ these field expressions are reduced to the usual ones specified by Fresnel’s theory. In the specific case of a diffracting half plane the numerical results obtained were practically the same as those given by Sommerfeld’s rigorous theory.The modified theory developed in this paper is based on the explicit assumption that the scalar theory of light cannot explain plolarization effects. This premise is justified in Sec. 4, where it is shown that previous attempts to do so have produced dubious results.     

直流三端子输电特性的研究

在使用他励式电力换流器的并列式直流多端子送电系统中，根据电力系统的需要，有时对支线换流站进行从整流到逆变，或者与之相反的切换，为了对支线换流站的电压极性进行切换必须使支线换流站与直流系统一时脱离，这样极为不便，为了解决这一问题，如果在需进行上述切换的支线换流站设置双向电力换流器，在进行由整流到逆变，或与之相反的切换时，则不必使支线换流站与直流系统相脱离，只需用正弦波电流跟随控制方式，改变基准电流的     

基于Vague集加权相似度量的双向近似推理

本文提出了一种新的Vague集的加权相似度量方法，以解决文献中关于Vague集相似度量的某些缺陷以及权向量中各个分量难以确定的问题，并且提出了Vague集间相似方向的概念，用它来描述两个相拟Vague集中哪个所包含的信息更精确，并给出了一个判定方法。在此基础上的给出了一种基于Vague集加权相似度量的双向近似推理方法，该方法更好地利用了Vague集信息的精确性，从而提高了推理的精确性和适用性。这为智能系统中的近似推理提供了一个十分有用的工具。     

An expeditious procedure for the accurate alignment and assembly of stereo micrographs

A simple procedure is described for the reproducible and convenient assembly of stereo micrographs, particularly as transparencies, with the help of an apparatus developed for this purpose. Technical features and applications are discussed.     

Bidirectional Reflectance Distribution Function of Rough Silicon Wafers

The trend towards miniaturization of patterning features in integrated circuits (IC) has made traditional batch furnaces inadequate for many processes. Rapid thermal processing (RTP) of silicon wafers has become more popular in recent years for IC manufacturing. Light-pipe radiation thermometry is the method of choice for real-time temperature monitoring in RTP. However, the radiation environment can greatly affect the signal reaching the radiometer. The bidirectional reflectance distribution function (BRDF) of rough silicon wafers is needed for the prediction of the reflected radiation that reaches the radiometer and for reflective RTP furnace design. This paper presents the BRDF measurement results for several processing wafers in the wavelength range from 400 to 1100 nm with the spectral tri-function automated reference reflectometer (STARR) at the National Institute of Standards and Technology (NIST). The rms roughness of these samples ranges from 1 nm to 1 m, as measured with an optical interferometric microscope. Correlations between the BRDF and surface parameters are obtained using different models by comparing theoretical predictions with experiments.     

小区有线电视双向网设计实践

在双向HFC网络中，为保证传输通道的性能指标，除了选用高屏蔽性能的网络器材外，网络的系统设计及回传系统的调试也很重要，故以一个小区的有线电视双向网设计作为典型加以介绍。     

阶梯电压驱动场致发光器件的电路设计

阐述了阶梯状电压驱动方式的具体原理及其硬件实现电路,同传统的方波电压驱动原理相比较,使用阶梯状电压驱动方式可以使场致发光显示器件的耗能降低到传统方式的75%,最后介绍了阶梯状电压驱动方式的硬件电路设计。     

单桩柱和波浪双向流固耦合的数值模拟

以单桩基支撑结构为对象,建立模拟波浪和单桩柱结构的三维模型,采用k-ε湍流模型和VOF运动界面追踪方法,实现了桩柱和波浪之间的双向流固耦合模拟,得到了波面三维显示图、流固交界面压力分布图和桩柱结构的受力图。还对桩柱上的最大等效应力做了研究,其变化范围是15 704~16 320 Pa,根据Von Mises屈服准则可知,桩柱在这种波浪条件下是稳定的。