实用场发射电子枪虚源半径的测量

本文在分析产生和影响实用场发射电子枪（ＦＥＧ）虚源半径各种因素的基础上，提出一种直接测量ＦＥＧ虚源半径的新方法－－场电子显微镜（ＦＥＭ）法。用该法对一实际ＦＥＧ的虚源半径作了实验测定，并与著名的球－－锥面模型进行比较，结果是一致的。表明该方法不仅简单且行之有效，具有实用价值。     

大信号设计GaAs MESFET功率合成

利用ＧａＡｓＭＥＳＦＥＴ功率特性的线性化模型，求出ＧａＡｓＭＥＳＦＥＴ近似最佳功率负载阻抗，为利用谐波平衡法计算提供初值。然后，使用自行研制的谐波平衡分析软件包，进行ＧａＡｓＭＥＳＦＥＴ大信号模型参数的提取和非线性电路模拟计算。将两只总栅宽为９．６ｍｍ的ＧａＡｓＭＥＳＦＥＴ管芯，利用内匹配功率合成技术，在Ｃ波段（５．５～５．８ＧＨＺ）制成１ｄＢ压缩功率大于８Ｗ，典型功率增益９ｄＢ的ＧａＡｓＭＥＳＦＥＴ内匹配功率管。     

Si亚微米MESFET的Monte Carlo法模拟

本文是继用Ｍｏｎｔｅ Ｃａｒｌｏ法模拟ＧａＡｓ亚微米器件后，进一步用该法模拟Ｓｉ亚微米ＭＥＳＦＥＴ。文中除了处理Ｓｉ和ＧａＡｓ散射机制不同外，在模拟方法上有重要进步：用ＦＦＴ代替迭代法，加速解Ｐｏｉｓｓｏｎ方程过程；用快速自散射代替常规自散射，压缩计算无用自散射时间。这些进步相当程度地克服Ｍｏｎｔｅ Ｃａｒｌｏ微粒模拟法费机时的固有缺点。模拟得到的形象且合理的结果，给出亚微米栅长时Ｓｉ ＭＥＳＦＥ     

计算椭圆曲线密码体制中的KP算法

本算法是一种确定性算法，用于计算有限域ＧＦ（２ｎ）上ＥＥＣ的ｋ　Ｐ，ｋ为整数，　为椭圆曲线上的点乘运算，详细介绍了该算法以及与该算法有关的射影坐标变换。     

采用汇编语言的快速傅里叶变换

快速傅里叶变换（ＦＦＴ）用于某些科学和信号处理应用中计算离散傅里叶变换。此变换历来用Ｃ语言执行。然而，假若速度是一个极端关键问题，则也可考虑用汇编语言执行此变换。下面就是这样的例子：分解为实数和虚数部分（ＢＵＦＦＥＲ－ＲＥＡＬＡＮＤＢＵＦＦＥＲ＿ＩＭＡＧＥ）的一系列离散点是程序的自变量，用来计算ＦＦＴ并把结果存储在它们对应的实数和虚数部分中（ＲＥＳＵＬＴ＿ＲＥＡＬａｎｄＲＥＳＵＬＴ＿ＩＭ＿ＡＧＥ）。程序工作首先计算所需要的幂，然后通过内和外循环的一组嵌套来计算变换。此外，已知ＦＦＴ具有倒数性质，…     

GaAs MESFET直流特性退化的失效分析

ＧａＡｓ ＭＥＳＦＥＴ直流特性退化的主要原因是源极漏极欧姆接触退化和栅极肖特基势垒接触退化，笔者用结构敏感参数电测法和Ｃ－Ｖ法进行失效定位和失效分析，为上述失效原因提供了证据。     

新型GaAsD－MESFETDCFL单元电路

本文基于自举反馈原理提出了一种新型的全部电耗尽型ＧａＡｓＭＥＳＦＥＴ构成的单电源ＧａＡｓＭＥＳＦＥＴ直接耦合逻辑ＦＥＴ单元电路．该单元电路比已有的各种ＧａＡｓ数字集成电路单元电路有明显优点，是ＧａＡｓ数字集成电路领域有前景的新型逻辑单元电路．     

GaAsMESFET在抗辐射领域的应用

详细论述了多种辐照源辐射ＧａＡｓＭＥＳＦＥＴ器件和电路产生的ＳＥＵ（单粒子翻转 ）效应，辐照源包括脉冲激光、质子、中子和电子不等。同时还讨论了计算机模拟辐射产生ＳＥＵ的过程和机制。研究表明：１）在低温生长ＧａＡｓ阻支的ＭＥＳＦＥＴ电路，有较强的抗ＳＥＵ能力；２）在ＭＥＳＦＥＴ中，产生ＳＥＵ的原因在于辐射导致了漏极收集电荷的增加，而且，电荷惧增强机制扔三种：ａ）背沟道导通机制，ｂ）双极增益机制；ｃ０     

砷化镓SJFET四端器件

本文提出一种由Ｍ－ＳＳｃｈｏｔｔｋｙ结和ｐｎ结组成的ＧａＡｓＳＪＰＥＴ四端器件，对该器件原理进行了分析与讨论，并在实验室研制出了ＧａＡｓＳＪＦＥＴ四端器件．实验结果表明，该器件可通过上、下两个栅分别调控，实现器件阈值电压连续可调．该器件极易获得稳定、重复的Ｅ－和Ｄ－ＭＥＳＦＥＴ，可望在ＧａＡｓ集成电路中得到应用．     

多晶硅发射极晶体管（PEI）Gummel—Poon模型

本文建立了能直接用于ＳＰＩＣＥ电路分析程序中的ＰＥＴ－ＧＰ模型。研究表明：可以采用两种方法来使用ＰＥＴ－ＧＰ模型。本文利用所研究器件的结构参数计算了ＰＥＴ－ＧＰ模型参数βＦ和特征频率ｆＴ。ｆＴ的计算和实验结果符合较好。βＦ的计算表明，所研究器件的多晶硅／硅界面复合较强，复合速度ＳＰ达到１０＾６ｃｍ／ｓ。     

W[111]尖端场发射电子枪的工作特性

本文报道了单晶W[111]尖端的制作,以及由W[111]尖端阴极,第一、二阳极组成的三极场发射电子枪(FEG)的工作特性。实验结果表明,这种FEG在枪室真空为510-7Pa,加速电压在30kV的条件下,其虚源半径为1.6nm;亮度为3.8109A/cm2.sterad;场发射电流为1A时,束流稳定性为5%(10min内)。说明它是一种较理想的点状电子源,在实际应用中具有广泛发展前景。     

An improved calculation procedure for the radiation pattern of acylindrical leaky-wave antenna of finite size

A method is given for calculating the radiation pattern of a finite-size cylindrical leaky-wave antenna structure consisting of a single source near a planar surface that supports leaky-wave propagation. The method accounts for the finite radius of the planar surface by subtracting the radiation from that part of the leaky wave that lies beyond the physical surface, from the exact radiation pattern corresponding to an infinite planar surface. Experimental results obtained for a leaky-wave structure consisting of multiple dielectric layers above a ground plane confirm the improved accuracy of the method, particularly for the part of the radiation pattern away from the peak     

Design of rotators based on coordinate transformation

Traditional cloak and rotator are obtained from mapping in single direction, either radial or tangential direction. However, this article proposed several novel structures obtained from mapping along multidirection, all of above designs are based on coordinate transformation theory. Those structures include "rotational cloak", "rota-tional concentrator", and so on, which are different from traditional structures. This paper discusses the optical properties of these novel structures; moreover, we have investigated the effects of various parameters on their properties, such as virtual radius and initial angle. Also,some interesting conclusions are drawn: 1) the energy convergent capability increases with virtual radius; 2) rotational angle of power flow direction depends on the value of initial angle and the location of optical source; 3) the permittivity and permeability of transformed material may be negative when virtual radius a greater than outer radius b, it is our well-known left-handed material.     

基于二维灰度直方图的蚁群图像分割

提出了一种基于二维灰度直方图的蚁群图像分割方法。该方法基于二维灰度直方图 的灰度、邻域平均灰度及灰度频数进行蚁群模糊聚类,通过二维灰度直方图的一维最佳投影,设置精确的初始聚类中心来解决蚁群算法循环次数多、计算量大的问题;并针对具体应用,对聚类半径、信息激素和启发式引导函数进行了相应的修正。实验表明该算法速度快、划分特性好,可以准确地分割出目标。     

激光辐照材料热效应问题的有限元实现

针对激光辐照光学透镜产生的热效应问题,选用有限元法推导了光学透镜模型的热传导方程的有限元求解格式,基于Matlab编程实现了计算光学透镜在脉冲激光辐照下的温度场分布。研究结果表明,光学透镜的温度随辐照激光光斑半径的增大而减小;随激光脉冲数目的增多而增大,但是由激光能量的累积效应所导致的材料温升并不显著;随激光功率的增大而增大,是影响材料温升的显著因素,当功率增大到一定数值时将造成光学透镜的损伤,文中激光功率达到250 mW时造成材料的熔融损伤。     

3-D corneal modeling system

New surgical procedures have been introduced recently that provide refractive correction to replace the use of eyeglasses or contact lenses. The procedures involve reshaping the cornea to compensate for the optical anomalies of astigmatism and nearsightedness. Although thousands of operations are currently performed in the U.S., there are no instruments available for monitoring the results. Thus, a critical need has arisen to inspect and measure the cornea's surface both before and after surgery. In this paper an instrument is presented which provides a detailed topographical model of an individual's cornea. The method uses a novel structured light source. The cornea is modeled as a convex mirror which forms a virtual image of the structured light source. A single image is recorded from the patient's cornea. The depth is obtained from triangulation between the acquired image and a reference image of a sphere. The reconstruction of the depth map is complicated by the fact that the magnification used in recording the image varies with the radius of curvature of the cornea. An iterative method is presented which solves for the radius of curvature despite the variation in magnification. The virtual image is digitized and the instantaneous curvature of the cornea is obtained. The instantaneous curvature is displayed in units of optical power (diopters). This display provides the ophthalmologist or optometrist with the essential optical properties of the cornea.     

用基于WEFD的微扰法计算谐振腔的Q值

对波动方程差分（WEFD）解法进行了研究,给出了电场的计算公式.将它应用于谐振腔Q值的分析,得到了与理论值吻合得很好的结果.     

Adaptive lossless coding scheme of lattice vector quantisation

In the process of quantisation, a lattice vector quantiser (LVQ) generates radius and index sequences. In lossless coding, the radius sequence is run-length coded and then Huffman or arithmetic coded, and the index sequence is represented by fixed binary bits. The author has improved the LVQ lossless coding by removing the redundant information between radius sequence and index sequence. An algorithm is developed that redistributes radius and index sequences. The algorithm adaptively shifts down large indices to smaller values and reduces the index bits. Hence, the proposed LVQ lossless coding method reduces the gap between actual coding bit rates and the optimal bit rate boundary. For a Laplacian source the proposed lossless coding scheme achieves more than 10% of bit reduction at bit rates higher than 0.7 bits/sample over the traditional lossless coding method     

细胞质多角体病毒的高分辨成像及其三维重构的初步结果

使用装有液氦冷却的冷冻样品支架的300kV场发射冷冻电子显微镜拍摄了细胞质多角体病毒（CPV），对这些电镜照片的频谱分析显示图像分辨率优于0．6nm。我们的三维重构结果使用了最新设计的图象管理和二十面体重构系统（IMIRS）软件包，这是第一个基于Microsoft Windows平台上运行的冷冻电镜三维重构软件包。从得到的一个初步的CPV三维结构，可以看出CPV是具有T＝1的病毒壳体，它的核心半径为28．5nm，在二十面体的顶点有十二个具有五次对称的突起，使它的半径达到36nm。     

The spreading resistance of a homogeneous slab on a high-resistivity substrate: Mixed boundary value solutions

The range of applicability of the mixed boundary value method for calculating spreading resistance is extended to a homogeneous slab with a disc contact source and backed by a substrate of arbitrary, but finite resistivity. Solutions are presented in terms of the spreading resistance correction factors and the source current density distributions for a slab of varying thickness and with various high resistivity substrates. In particular, the results for a thin slab indicate that, as the substrate resistivity increases, more and more of the source current is concentrated near the edge of the disc electrode.A comparison is made of the source current density and potential corresponding to the mixed boundary value method with those given by the uniform flux and the variable flux (power-loss) method. It is found that, except for large slab thicknesses, the source potential distributions for a slab with a high resistivity substrate are not strongly influenced by the particular form of the source current density distribution assumed in either the uniform flux or the variable flux method. In consequence, both these two methods yield correction factors which agree quite closely with those derived from the mixed boundary value method.