High resistivity measurement of SiC wafers using different techniques

To establish fast, nondestructive, and inexpensive methods for resistivity measurements of SiC wafers, different resistivity-measurement techniques were tested for characterization of semi-insulating SiC wafers, namely, the four-point probe method with removable graphite contacts, the van der Pauw method with annealed metal and diffused contacts, the current-voltage (I-V) technique, and the contactless resistivity-measurement method. Comparison of different techniques is presented. The resistivity values of the semi-insulating SiC wafer measured using different techniques agree fairly well. As a result, application of removable graphite contacts is proposed for fast and nondestructive resistivity measurement of SiC wafers using the four-point probe method. High-temperature van der Pauw and room-temperature Hall characterization for the tested semi-insulating SiC wafer was also obtained and reported in this work.     

电力系统谐波检测的现状与发展

准确、实时地对电力系统谐波进行检测有着重要的意义。本文根据电力系统谐波测量的基本方法，对近年来电力系统谐波检测的新方法进行了分析和评述。最后对电力系统的谐波测量进行了总结并提出了看法。     

地杂波O．94μm激光后向反射率测试研究

通过对地杂波O．94μm激光后向反射率的测试，获取不同入射角的多背景后向反射率测试数据。通过对测试数据的分析处理提供特征信息，为激光探浏器设计提供依据。     

工业管道测厚的几点问题探讨

超声波测厚在腐蚀监测上应用越来越广泛,为让这项检测技术更准确、更可靠,充分发挥功效,文章就工业管道测厚中测厚数据处理、测厚点选择、高温问题以及其它影响因素等几个方面进行了探讨。     

铁路罐车密闭装车计量系统的运行分析

从中国石化股份公司济南分公司新上铁路罐车密闭装车计量系统的背景出发，阐述该系统的设计思想和组成；通过分析实际运行过程中仪表比对数据，讨论影响仪表贸易交接准确性的各种因素，提出相应的解决方法；最后通过铁路罐车密闭装车计量系统投用效果。证实该系统可产生明显的经济效益。     

Role of Perceived Importance in Intergroup Contact.

Furthering G. W. Allport's (1954) contentions for optimal contact, the authors introduce a new construct: the perceived importance of contact. They propose that perceived importance is the best proximal predictor of contact's reduction of prejudice. If individuals have opportunities for contact at work or in the neighborhood, their chances to have intergroup acquaintances and friends increase. Intergroup contact among acquaintances and friends can be perceived as more or less important, which in turn determines intergroup evaluations. A 1st study shows that the new measure of perceived importance is indeed distinct from established quantity and quality indicators. The results are cross-validated in a 2nd study that also sheds light on the meaning of importance. In 3rd and 4th studies, structural equation analyses and a meta-analysis support the hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

飞行目标3维姿态测量的新方法

针对传统光测方法通常用于测量目标的点运动轨迹,而难以获得目标的3维姿态参数的情况,提出用数字图像处理手段,对目标图像建立特征点,结合特定的算法,得出目标的俯仰角、偏航角、滚动角、漂移量等3维参数,从而获取更多的目标姿态参数的新方法。     

An Acoustic Converter Used to Measure Ionizing Radiation Energy Loss

A monitor is proposed based on ultrasonic production when ionizing radiation passes through a medium. The recording element is a 0.2 mm aluminum plate mounted in a ceramic acoustic converter AC in the form of a wedge of thickness 2 mm. The low plate thickness minimizes the beam parameter distortion, while special technology used in the AC provides high sensitivity. The device has been calibrated in the proton beam from the ITEP accelerator at 200 MeV with 2·10⁹–6·10¹⁰ particles in a pulse and a pulse length of 70 nsec.     

目标RCS动态数据的分布特征研究

复杂目标在不同视向的RCS分布特征是不同的，传统模型对此都没有给出详细的结果。文中以某歼击机和直升机为对象，应用X^2。分布、对数正态分布和瑞利分布模型，以及Kolmogomv拟合优度检验方法，研究其RCS动态测量数据的统计分布特征，得到了在一定显著性水平下，两种目标在不同视向角下对三种模型的拟合效果，同时得到应用X^2。分布拟合时模型半自由度随视向角的分布情况。在显著性水平为0．05时，对于在较短时间内录得的复杂目标动态RCS数据，应用X^2分布可以取得较好的拟合效果。文中结果精确地描述了目标RCS的起伏特征，能够为目标回波的精确模拟与检测提供可靠的依据。     

衍射法细丝直径的精密测量

分析了激光衍射法测量细丝直径技术中影响精度的几个主要因素，研究了一种微弱衍射条纹的精密处理及识别技术，有效地提高了测量精度，实测结果表明，文中讨论的技术能在１０￣５０μｍ的范围内实现正负０．１μｍ的重复精度，分辨力优于０．０１μｍ。