Radar Imaging Based on Iterative Algorithms

It has long been realized that the problem of radar imaging is a special case of image reconstruction in which the data are incomplete and noisy. In other fields, iterative reconstruction algorithms have been used successfully to improve the image quality. This paper studies the application of iterative algorithms in radar imaging. A discrete model is first derived, and the iterative algorithms are then adapted to radar imaging. Although such algorithms are usually time consuming, this paper shows that, if the algorithms are appropriately simplified, it is possible to realize them even in real time. The efficiency of iterative algorithms is shown through computer simulations.     

A small GTP-binding protein dissociates from synaptic vesicles during exocytosis.

Low-molecular-weight GTP-binding proteins are strong candidates for regulators of membrane traffic. In yeast, mutations in the sec4 or ypt1 genes encoding small GTP-binding proteins inhibit constitutive membrane flow at the plasma membrane or Golgi complex, respectively. It has been suggested that membrane fusion-fission events are regulated by cycling of small GTP-binding proteins between a membrane-bound and free state, but although most of these small proteins are found in both soluble and tightly membrane-bound forms, there is no direct evidence to support such cycling. In rat brain a small GTP-binding protein, rab3A, is exclusively associated with synaptic vesicles, the secretory organelles of nerve terminals. Here we use isolated nerve terminals to study the fate of rab3A during synaptic vesicle exocytosis. We find that rab3A dissociates quantitatively from the vesicle membrane after Ca2(+)-dependent exocytosis and that this dissociation is partially reversible during recovery after stimulation. These results are direct evidence for an association-dissociation cycle of a small GTP-binding protein during traffic of its host membrane.     

D－胺基半乳糖（D－galactosamine）对小白鼠肝脏的损害作用

给小鼠一次性腹注Ｄ－胺基半乳糖（Ｄ－Ｇａｌｎ）６００和１２００ｍｇ／ｋｇ，或１６小时内连续６次腹注３００ｍｇ／ｋｇ，停药后４８小时，血清谷丙转氨酶（ＳＧＰＴ）明显升高，局部肝细胞呈现肝炎病理形态改变。病变机理是过量Ｄ－Ｇａｌｎ入肝代替了尿苷二磷酸葡萄糖的代谢途径所引起的。     

墨法在中国传统书法艺术中的地位和作用

墨是中国传统书法艺术的书写原料，离开了它即无字形，离开了用墨的方法(墨法)，则形成不了书法艺术的深度和广度。因此，掌握好用墨的干湿浓淡，充分发挥好其对比作用，是不同书家、不同书体、不同墨法和不同风格的展现。墨法是传统书法作为一门艺术的法宝之一。     

全球变暖-研究挑战日本全球变暖倡议书报告

本专题著作是“Chikyu Ondanka Kenkyu no Saizensen（全球变暖研究方法技术形势）”的英文译本，是针对日本政府内阁科学与技术政策委员会（CSTP）所制定的全球变暖研究倡议书的五份报告书之一。其余四份报告书分别为废弃物清理和资源循环技术、关于江河流域与城市地区生态和谐发展的改造、化学物品风险管理以及世界水循环圈。     

构建和谐企业 促进企业创新发展

构建和谐企业不仅有其客观必然性,而且也是企业加快发展的主观需要。文中论述了构建和谐企业要充分认识其基本特征,注意把握其立足点,以进一步推进企业的创新与发展。     

The Huntington's disease candidate region exhibits many different haplotypes.

Analysis of 78 Huntington's disease (HD) chromosomes with multi-allele markers revealed 26 different haplotypes, suggesting a variety of independent HD mutations. The most frequent haplotype, accounting for about one third of disease chromosomes, suggests that the disease gene is between D4S182 and D4S180. However, the paucity of an expected class of chromosomes that can be related to this major haplotype by assuming single crossovers may reflect the operation of other mechanisms in creating haplotype diversity. Some of these mechanisms sustain alternative scenarios that do not require a multiple mutational origin for HD and/or its positioning between D4S182 and D4S180.     

三角形速度场解析平面变形辊拔与辊挤

文章对平面变形辊拔与辊挤问题建立了运动许可的三角形速度场并获得上界解析解。该解与 Avitzur 以连续速度场得到的上界解进行比较表明,有时本文解法可得到更低的上界值。     

用于兵器的微机控制的电液随动系统

本文介绍16位微机(TWS-0600)控制兵器的高精度电液随动系统的原理与结构,着重讨论了控制器的设计和实现,而控制器的设计,采取了双模控制与分离PID的方法,利用微机逻辑判断功能根据系统误差角大小适时地变更控制器的结构.实践表明这种设计方法对有大惯性负载的兵器随动系统实现高精度、快速、平稳跟踪等技术要求具有工程实际意义,而且,系统有较好的控制效果.