银川市大气颗粒物中有害成分的污染状况及其分布规律

用ＫＢ－１２０型空气采样泵和ＭＷ级联撞击器采集大气颗粒物，采用原子吸收分光光度计和气相色谱等仪器，分析了银川市不同季节、不同功能区大气颗粒物中粒径小于２．５μｍ至１５μｍ颗粒中的多环芳烃（ＰＡＨ）和１５种重金属元素，结果表明银川市的污染主要由燃煤所致。各功能区大气中的ＰＡＨ和１５种重金属元素浓度均很高，ＢａＰ浓度超标。     

Some Concepts and Mathematical Consideration of Similarity System Theory

This paper introduces a new discipline called Similarity System Theory. Some new concepts, such as Similar Elements, Similarity Unit, Similar Systems and Similarity Entropy are presented. The numerical method and dynamic analysis of similarity system theory are studied.     

半单齐性半凯勒流形的分解定量与参数表示

本文在特征元为单元的假设下证明了半单齐性半凯勒流形的分解定理，并且用根系给出其参数表示。     

S-过程元素丰度分布规律的研究

利用指数辐照理论的解析解研究了AGB星S过程元素的丰度分布规律 .结果表明 ,在低金属丰度下 ,AGB星核合成产量强烈依赖于金属丰度 ,但如果将Sm( 88相似文献   

大容量机组热挤压斜三通设计

针对高效低耗节能的亚临界和超临界大功率300MW 及以上机组建设,主蒸汽管道所用的锻制斜三通仍全部靠国外进口:该锻制斜三通重量大、成本高、对整个管系的应力、支吊等方面都会带来许多麻烦。因此,在分析热挤压直三通设计和成型机理及锻制斜三通设计原理的基础上,综合提出了“应力面积补偿计算法”,设计300MW 机组Ⅲ热挤压45°斜三通,并通过有限元进行应力分析和应力状态模拟实验,满足工况对管件的强度要求,完全可替代进口锻制300MW 机组45°三通。该产品的替代减小了对管系的应力和支吊的影响,减少了管件的重量,降低成本等优越性。     

Effects of chronic caffeine feeding on the activities of oxygen free radical defense enzymes in the growing rat heart and liver

The purpose of the present study was to determine the relationship between concentration of Zn, Cu and Fe, and the catalase, glutathione peroxidase and superoxide dismutase activities in the heart and liver of newborn rats whose dams were fed a diet supplemented with caffeine. Heart Zn levels of the 22- and 30-day-old rats of the caffeine group showed a decrease, whereas liver Zn levels showed an increase compared to the control. Cu levels in the liver at day 22 in the caffeine group were less than in the control. Cu- and Zn-containing superoxide dismutase activities showed an increase in the hearts of the caffeine group compared to the control. The activity of catalase and glutathion peroxidase showed no difference in the heart and liver between the groups. The present study suggests the possible involvement of superoxide dismutase enzyme in the impairment of heart formation as a result of chronic caffeine intake in the early growing period.     

Transposable element insertion patterns as test of contamination of aDrosophila melanogaster inbred line

A highly inbred line ofDrosophila melanogaster, stable for the insertion pattern of the transposable elements copia and mdg1, was experimentally contaminated by flies from another line. We show that the alien genome income is clearly detectable by the changes induced in the insertion profiles of transposable elements, even twenty generations later.     

Ladyzhenskaya模型的低阶三角形有限元方法

对定常Ladyzhenskaya模型提出了一种稳定化有限元法.给出了用低阶三角形元逼近时,有限元解的存在性、唯一性及收敛性的数字分析。     

火焰原子吸收光谱法测定荷叶中几种营养元素含量

本文采用火焰原子吸收光谱法测定了荷叶中K、Ca、Mg、Mn、Fe、Zn六种营养元素的含量。结果表明，K、Ca的含量较高，微量元素Mn、Fe、Zn的含量依次降低。方法回收率在97％-103．5％之间，相对标准偏差在0．70％-3．51％之间，测定结果对荷叶进一步综合开发利用提供了有用的数据。     

自适应有限元结合弧长法求解软化问题

将自适应有限元与弧长法迭代算法相结合，用于软化材料的弹塑性有限元计算．讨论了程序中软化材料的弹塑性计算、本构积分、弧长法迭代、自适应有限元，得到了自适应有限元与弧长法结合计算软化问题的流程图．算例分析结果验证了本文分析方法的有效性，表明自适应有限元在模拟局部化问题中具有优势．