Krylov子空间投影法研究进展

Ｋｒｙｌｏｖ子空间投影法是一类非常有效的大型稀疏线性代数方程组解法，已被广泛应用于各种领域，随着左右空间Ｌｍ，Ｋｍ的不同取法可以得到许多人们熟知的方法．本文按矩阵Ｈｍ的不同类型，即为上Ｈｅｓｓｅｎｂｅｒｙ阵还是三对角阵将Ｋｒｙｌｏｖ子空间投影法分成两大类，从每步迭代是否具有最优性和方法的存储量、计算量等方面对Ｋｒｙｌｏｖ子空间法及其最新进展进行评述，指出Ｋｒｙｌｏｖ子空间法的局限及今后的研究方向．     

以企业核心竞争力的提高促进物流业态的转型

随着社会经济的发展，物流业正蓬勃发展起来。核心竞争力是我国物流企业参与激烈的市场竞争的基础和关键。在传统储运业向现代物流业转型过程中，要突破障碍，依托提升企业核心竞争力，才能使企业立于不败之地。本文站在物流企业的角度，详尽分析物流企业的核心竞争力，以及借助提高核心竞争力，加快传统储运业向现代物流转型的四种模式的基础上，有针对性的提出促进我国物流业态转型的对策，以提高我国物流企业的竞争能力。改善物流服务水平。     

压水堆控制棒导向筒结构改进对落棒的影响

为改善横向水力载荷对控制棒导向筒的作用，对靠近上腔室出口管嘴附近的控制棒导向筒（对称的４组：０２－２６，０３－２５，１１－２９，１２－２８）加设了保护套．在秦山核电站压水堆上腔室１４的可视化模拟体中，以水为介质进行了实验研究，把结果与未加设保护套的实验结果作了分析比较，得到了对靠近上腔室出口管嘴附近的控制棒导向筒加设保护套有助于改善流场对控制棒导向筒的水力载荷作用和确保控制棒能按指令在导向筒中自由升降和快速下插的结论．     

用微波实验测定光速

实验中，利用微波源发出各种频率的电磁波，在波导中借助测量线测定相应的电磁波的波长λg，计算光速c，验证麦克斯韦电磁场理论。     

沼气在果菜粮贮藏业上的应用

文中介绍沼气这种新型绿色能源在果菜粮贮藏中的应用情况,详尽描述了其在贮藏果品、蔬菜中的应用过程,文中对其作用的原理和益处也给予了适当介绍。     

提高石油化工企业原料利用率的技术研究

坚持眼睛向内,挖潜增效,这是当前原油变重、供应量不足,生产资料涨价的客观形势下走出困境、提高企业效益的主要途径之一,本文从拓宽催化回炼油的利用途径,催化和加氢裂化互换循环油加工,优化重油原料的安排,提高轻油头的化肥效益,挤出烷基化原料,开发异丁烷的化工用途及油化结合等方面,分析通过厂际装置间的原料互供、生产优化来挖掘企业内涵,提高经济效益.     

Distributed and Parallel Component Library

Software component library is the essential part of reuse-based software development. It is shown that making use of a single component library to store all kinds of components and from which components are searched is very inefficient. We construct multi-libraries to support software reuse and use PVM as development environments to imitate Iargescale computer, which is expected to fulfill distributed storage and parallel search of components efficiently and improve software reuse.     

Evolutionary and ecological implications of cardenolide sequestration in the monarch butterfly

Summary Monarch butterflies sequester cardenolides from their larval host plants in the milkweed genusAsclepias for use in defense against predation. Of 108Asclepias species in North America, monarchs are known to feed as larvae on 27. Research on 11 of these has shown that monarchs sequester cardenolides most effectively, to an asymptote of approximately 350 g/0.1 g dry butterfly, from plants with intermediate cardenolide contents rather than from those with very high or very low cardenolide contents. SinceAsclepias host plant species are distributed widely in space and time across the continent, monarchs exploit them by migration between breeding and overwintering areas. After overwintering in central Mexico, spring migrants east of the Rocky Mountains exploit three predominantAsclepias species in the southern USA that have moderately high cardenolide contents. Monarchs sequester cardenolides very effectively from these species. First generation butterflies are thus well protected against predators and continue the migration north. Across the northern USA and southern Canada most summer breeding occurs on a fourthAsclepias species and in autumn most of these monarchs migrate back to Mexican overwintering sites. The ecological implications of this cycle of cardenolide sequestration for the evolution of monarch migration are discussed.     

关于Terrell转动的一点商榷

<正>《大学物理》1985第l期上发表了胡先生有关"Terrell转动"的文章。作者的结论是:"综上所述,"......v>ccos时,能同时看到后表面,侧面和反转了的前表面,一,在v=c时,相当于静止立方体转动了尤一e的角度,并且看起来似乎是透明的."     

Storage of irradiated human blood; a source of error in quantitative chromosome analysis

Summary Human whole blood was irradiated with 2.5 Gy of 220 kVp X-rays and stored before culture with 9.7 M BrdU and 19.4 or 38.7 M BrdU for 0, 24, 48 and 72 h. The frequency of dicentrics and ring chromosomes was determined in cells staining as first division (M1) metaphases with the fluorescence plus Giemsa technique. Storage had no influence on the observed aberration yields in 44 h cultures containing 9.7 M BrdU. In 66 h cultures at 19.4 M BrdU the observed yields after 2 and 3 days' storage were significantly lower as compared to cultures from fresh blood. No storage effect was revealed in 66 h cultures containing 38.7 M BrdU. In cases where cytogenetic radiation dosimetry has to be carried out using blood samples which have been in transit for 2–3 days, the findings are of relevance for a correct determination of the chromosome damage in M1 cells.