变体电子衍射花样的普适研究方法

在固相变中，当析出相的晶系与基体不同时将产生多种变体，由此导致变体电子衍射花样和相结构的分析的困难，本文发展一种变体电子衍射花样的普适研究方法，预测了Ｉｎｃｏｎｅｌ７１８合金中γ″相变体电子衍射花样的特征，并与Ｑｕｉｓｔ等人的工作进行了比较。     

已知晶体电子衍射指标化中的实际问题

电子衍射是晶体结构分析最为常用的实验技术之一,电子衍射花样能直接反映晶体倒易点阵的特征。但利用传统方法对电子衍射花样进行指标化相当耗时、繁杂。为此,本文基于一些常用软件和DM插件对指标化过程中衍射点间距的测量、晶面间距的计算和米勒指数的指认等环节进行实例分析,对指标化过程中的一些常见问题进行可行性讨论,以期实现更为便捷的衍射分析。     

借助高分辨电子显微像校正电子衍射强度的动力学效应

针对高分辨电子显微学和电子衍射相结合测定晶体结构的图像处理技术，提出了一种借助高分辨电子显微像来校正低散射角电子衍射强度动力学效应的新方法，将此法试用于Ｂｉ２（Ｓｒ０．９Ｌａ０．１）２ＣｏＯｙ晶体结构分析，结果说明此法有效。     

缺陷晶体电子衍射波振幅的校正

在运动学近似下，通过解卷处理，可以从单张高分辨电子显微像（以下简称高分辨像）获得晶体的结构像。李方华和何万中等人曾用此技术处理了场发射电子显微镜拍摄的高分辨像，处理后的像分辨率达电子显微镜的信息分辨极限，得到了原子分辨率的晶体缺陷图像［１，２］。但由...     

TEMlab1.0:基于Matlab的透射电镜衍射花样分析软件包

本文主要介绍了在Matlab环境下编写的用于透射电镜电子衍射花样分析的软件包。此软件包主要包括建立已知物相的结构数据库、已知物相花样的标定和模拟、未知物相布拉菲点阵的推导、孪晶花样的标定、取向关系分析、菊池线分析和找特征平行四边形等功能。满足了电子衍射花样分析时的多方面需求。     

EBSD花样的图像畸变及其修正

EBSD花样存在图像畸变,使得由其三维重构解析晶体Bravais点阵变得困难。本文详细介绍了EBSD衍射数据几何修正的方法：利用样品到屏幕的距离,由EBSD花样上的衍射数据修正晶体倒易矢量的长度及其夹角。使用透辉石晶体的EBSD花样,验证了几何修正的效果,结果表明衍射测量数据经过修正并用最小二乘法重新拟合后,倒易矢量偏离二维拟合网格的程度降低,其分布更接近真实情况。     

高分辨电子显微学与电子衍射相结合在测定晶体结构中的应用

本文简单介绍了高分辨电子显微学中测定晶体结构的尝试法及其局限法，以及以高分辨电子显微学与电子省射相结合为基础所建立的图像处理方法。并针对此图像处理方法提出了一种修正电子衍射强度的方法，它也建立在高分辨电子显微学和电子衍射相结合的基础上，文中重点介绍了此方法的步骤和应用效果。     

单晶电子衍射的相对强度

本文提出了一种新的表达电子衍射相对强度的经验公式。利用衍射斑点的灰度侧视分布图,详细研究了Ni-Fe-Ga合金中14M调制结构马氏体的选区电子衍射图。结果表明：晶体结构因数的对数值与其相应的衍射斑点灰度积分值差的函数呈线性关系。     

Kossel-Möllenstedt衍射花样特征及薄晶体厚度测定

本文利用会聚束电子衍射(CBED)技术测定了晶体Si的局部厚度和消光距离ξ,讨论了关键参数n1取不同值时的数据特点及对分析结果的影响规律,明确了n1的确定方法,总结了Kossel-M?llenstedt(K-M)衍射花样特征及影响因素,给出了Si晶体(400)晶面K-M衍射花样的暗条纹位置预测图.结论如下:当n1<真值...     

扫描电镜EBSD装置

在扫描电镜中安装背散射电子衍射装置并接收分析材料的晶体学信息，是80年代末兴起的一种技术，用该技术可以做多方面的工作可以顺利解决X射线衍射和透射电镜电子衍射无法解决或难于解决的问题。北京有色金属研究总院在国家科技部的支持下，成功地研制了扫描电镜背散射衍射接收和分析装置。     

An analytical model for high electron mobility transistors

In this paper we present a new model for HEMT's which is based on a single analytical function that describes the electron concentrations in the two dimensional electron gas and in the AlGaAs layer. Besides accounting for the AlGaAs conduction, the model includes the effect of mobility degradation, channel length modulation in the saturation region and the series resistances R_S and R_D. The model results in closed form expressions for the current, transconductance, output conductance and gate capacitance. Finally, the theoretical predictions of the model are compared with the experimental data and shown to be in good agreement over a wide range of bias conditions     

Convergent-beam electron diffraction

This paper reviews the convergent-beam electron diffraction (CBED) technique. Point- and space-group determination methods of ordinary crystals are described, along with an example of the determination method for Sr?Ru?O?. The symmetry determination of one-dimensionally incommensurate crystals and quasicrystals is explained. The large-angle CBED technique, which is indispensable for lattice defect and lattice strain analysis, is also described. A real procedure for lattice strain analysis is provided, using an example of a multilayer Si?-xGe(x)/Si material. A nanometer-scale crystal structure refinement method and charge density and crystal potential determination method by CBED are briefly described.     

An analytical method for linear combining with application to FFHNCFSK receivers

A method for obtaining the probability density function (PDF) and the cumulative density function (CDF) of sum-independent random variables is presented. The method is capable of determining the PDF and CDF of this sum for an input consisting of any combination of a signal tone, white Gaussian noise, and multiple interfering tones. It is based upon circularly symmetric function theory, Fourier-Bessel series, and Fourier series. To illustrate this method, applications are presented for a fast frequency-hopped noncoherent frequency-shift-keyed communications system. From the PDF and CDF of the received signal, performance values such as the error probability for demodulation, the probability of detection and false alarm for coarse-time synchronization and the mean and variance of timing-error estimates for fine-time synchronization are obtained     

Reflection high-energy electron diffraction from lithium niobate single-crystal surfaces for application in molecular beam epitaxy

A modified RHEED system has been constructed to study nonconductive crystal lithium niobate (LiNbO3) using electron energies up to 50 keV. The problems encountered are discussed and preliminary results presented. We outline the potential use of the technique in the routine analysis of insulating substrates prior to the deposition of epitaxial layers by MBE, and in the examination of the deposited layers.     

定量三维电子显微术及三维电子衍射

用电子晶体学可以确定尺度在微米甚至纳米级晶体的原子结构。它所要求的晶体尺寸比X射线晶体学所需的小百万倍。确定晶体的原子结构既可通过对高分辨电子显微像作图像处理,也可直接用电子衍射数据。同时还可将高分辨电子显微像和电子衍射数据与X射线粉末衍射结合起来确定晶体结构。如果晶体的单胞很大,原子在任何方向上的投影都有重叠,确定晶体的原子结构则需要拍摄一系列不同晶带轴的电子衍射图及高分辨像,再将其综合起来重构晶体的三维静电势图,以得到晶体的原子位置。本文将概括地介绍最近十几年中电子晶体学的一些最新进展及其在无机晶体结构解析方面的一些最新应用实例。     

电子衍射的目前进展

高能电子的量子波可用来探测有机和无机材料的原子结构.电子和物质有很强的相互作用,同时还可以形成很小的束斑.基于上述原因,电子在研究微小晶体、表面和材料的微结构上有很大用途.本文综述了电子衍射的最新进展和应用.     

An analytical solution to the diffraction problem of diagnosing the position and size of a sphere

A method for determining the position and dimensions of a body from the scattered field is described. The body (a metal solid sphere) is situated in the near-field zone of a transmitting antenna, and the receiving antenna is situated in the near zone of the body. The parameters of the body are calculated from the measured wave amplitudes in the dielectric waveguide of the receiving antenna. For calibration of the antenna, the body is replaced by a metal mirror.     

面向学生软件开发过程应用实践

软件企业希望聘用懂技术又熟悉软件过程的员工,而在校学生更重视软件开发技术的学习,过程训练欠缺是普遍存在的问题。为提高在学校生的过程能力,通过对在校学生的特点进行分析,在现有过程模型的基础上提出了针对高校学生的过程模型HKSP,并在学生实习中实施了这个过程模型,收到了较好的效果。     

An analytical model for electron transport and luminance in SrS:Cu,Ag ACTFEL display devices

An analytical model is developed to explain electron transport and luminance mechanisms in SrS:Cu,Ag ac thin film electroluminescent (ACTFEL) display devices. The model includes shallow and deep interface states, bulk traps, and impact excitation and ionization of activators. Mathematical expressions describing optoelectronic processes in the phosphor layer and interface states are written and numerical solutions for field, current and luminance are obtained. Results of calculations are compared with experimental data. The model is able to simulate the dominant features of the experimental luminance and current waveforms.