粉末冶金法与熔化法制造的SiC／Al复合材料的对比

前言 为了提高不连续体增强金属基复合材料的强度,已有人建议采用粉末冶金法(简写为PM法)制造复合材料,目前大部分不连续体金属基复合材料是用此方法制造的。这种设想的原因是,在PM法制造的过程中,可产生高的位错密度和小尺寸的亚晶粒,增强剂阻碍再结晶,因此这是导致PM法制造的不连续体增强金属基复合材料具有高强度的原因。Nardone和Prewo的设想无疑表明,如果用熔化金属基体的方法制造复合材料,就不具有高的位错密度和小尺寸亚晶粒,熔化法制造的复合材料的强度低于PM法制造的复合材料     

在杂波环境中目标跟踪的测量预处理方法

为了提高基于卡尔曼滤波器的传统跟踪算法的性能，本文提出了一种新的测量预处理技术。文中根据最大似然估值方法对接收测量值进行预处理。模拟结果表明该方法无论是在无杂波环境中还是在杂波环境中都具有最好的性能。     

用于障碍回避的毫米波雷达

本文讨论了目前在菲利浦研究实验室为雷达障碍回避系统所做的工作的原由，并给出一些实验结果。讨论了适于直升机和陆地车辆应用的系统的研究工作，强调了两者的类似之处。所阐述的方法以采用低成本９４ＧＨｚ前端为基础；采用了为灵巧武器发展的技术；依托先进的数字处理使之能够的取所需信息并以有效形式提供给用户。     

Ultrastructural and geochemical characterization of Archean-Paleoproterozoic graphite particles: implications for recognizing traces of life in highly metamorphosed rocks

Abundant graphite particles occur in amphibolite-grade quartzite of the Archean-Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wutai graphite particles were extracted for further investigation. Laser Raman spectroscopic analysis of a population of extracted graphite discs indicated that they experienced a maximum metamorphic temperature of 513 +/- 50 degrees C, which is consistent with the metamorphic grade of the host rock and supports their indigenicity. Scanning and transmission electron microscopy revealed that the particles bear morphological features (such as hexagonal sheets of graphite crystals) related to metamorphism and crystal growth, but a small fraction of them (graphite discs) are characterized by a circular morphology, distinct marginal concentric folds, surficial wrinkles, and complex nanostructures. Ion microprobe analysis of individual graphite discs showed that their carbon isotope compositions range from -7.4 per thousand to -35.9 per thousand V-PDB (Vienna Pee Dee Belemnite), with an average of -20.3 per thousand, which is comparable to bulk analysis of extracted carbonaceous material. The range of their size, ultrastructures, and isotopic signatures suggests that the morphology and geochemistry of the Wutai graphite discs were overprinted by metamorphism and their ultimate carbon source probably had diverse origins that included abiotic processes. We considered both biotic and abiotic origins of the carbon source and graphite disc morphologies and cannot falsify the possibility that some circular graphite discs characterized by marginal folds and surficial wrinkles represent deflated, compressed, and subsequently graphitized organic-walled vesicles. Together with reports by other authors of acanthomorphic acritarchs from greenschist-amphibolite-grade metamorphic rocks, this study suggests that it is worthwhile to examine carbonaceous materials preserved in highly metamorphosed rocks for possible evidence of ancient life.     

一种变速恒频（VSCF）飞机发电机系统的数学仿真

目前，可变频输入恒频输出的直流环路变换器已成为极具发展前途，并可替代恒速机械传动装置的装置之一，可作为来自飞机发电机的一种恒频电源。更换和维修的简便性、维护要求的降低以及具有判定飞机上所有电气系统元件位置的能力结合起来，使维护时间明显减少了。介绍了典型电气系统数字仿真的一种实用计算方法，该方法把整个电源网络初步分为一组恰当的子网络，然后利用连接矩阵把各子网络的计算方程与整个网络的方程组合。给出了整个系统的典型结果，其具体性能使许多重要的设计考虑在制造前就得到了研究。