一种大功率无刷直流电机控制器的研究

针对某雷达天线方位驱动电机,从工程应用方面出发,分析了电磁感应传感器型无刷直流电机的运行原理,并基于高电压、大功率PWM技术,提出了一种大功率无刷直流电机的驱动控制器.     

Quaternary high-resolution opal record and its paleoproductivity implication at ODP Site 1143,southern South China Sea

The correlation of opal content and MAR with oxygen isotopic records of benthonic foraminifera at Site 1143, southern South China Sea indicates that,since about 900 ka,the increasing opal content and MAR during the interglacial periods is inferred to reflect the bigher surface productivity ,for the intensified summer monsoon during the interglacial periods would result in the enhanced upwelling and nutrient supply,Time-sequence spectral analyses of oxygen isotopic record ,opal content and MAR at intervals of 0-900 ka reveal that the changes of surface productivity were dominantly forced by the variations of the earth orbital cycles.     

A complete sequence and comparative analysis of a SARS-associated virus(Isolate BJ01)

Severe Acute Respiratory Syndrome (SARS) is a newly identified infectious disease[1—5]. The global outbreak of SARS has been threatening the health of people worldwide and has killed 353 people and infected more than 5462 in 27 countries, as reported by WHO on April 29, 2003 (http://www.who.int/csr/sarscountry/en). Although it has been recognized that a variant of virus from the family of coronavirus might be the candidate pathogen of SARS[1—5], its identity as the unique pathogen sti…     

三河湿地自然保护区水禽资源初步调查

2 0 0 1-2 0 0 3年对三河湿地自然保护区水禽资源进行了调查 ,结果表明 ,本区共有鸟类 7目 13科 5 6种 ,其中古北界鸟类 43种 (76.79% ) ,东洋界鸟类 7种 (12 .5 0 % ) ,广布型鸟类 6种 (10 .71% ) ,湿地水鸟组成呈现南北交错 ,以古北界为主的特征 .繁殖水鸟 10种 ,占 17.86% ,非繁殖鸟 46种 ,占 82 .14 % .在繁殖鸟中 ,古北界有 2种 ,东洋界 4种 ,广布种 4种 .     

腐蚀管线的剩余寿命预测

预测管线的腐蚀变化趋势及腐蚀对管线结构完整性的危害是评价管线剩余寿命的关键步骤。将影响管线剩余寿命的各种因素看成是分布各异的随机变量 ,建立了预测管线失效的概率数学模型。利用这一模型 ,研究了腐蚀速率、缺陷深度、管道壁厚和工作压力等因素对管线可靠性的影响。结果表明 ,各参数的不确定性越大 ,管线的可靠性越低 ;缺陷深度在腐蚀缺陷形成初期 ,对管线的可靠性有很大影响 ,而随着时间的推移 ,腐蚀速率将对管线的可靠性有较大影响。对一条输油管线 ,基于管线腐蚀检测数据 ,对 1km长度的管道进行失效概率统计分析得到的腐蚀速率能够对管线全线的安全状况做出合理预测 ,从而为管线的进一步维修与检测提供参考资料。     

Recent development of organic electron transport materials

This article reviews the recent development of organic electron transport materials applied in the fields of organic photoconductors, light-emitting diodes, field-effect transistors and solar cells. Several technologies for charge carrier mobility measurement are summarized and compared, and a series of basic principles for designing high-performance organic electron transport materials are suggested as well.     

Nd isotopic characteristics of Proterozoic metasedimentary rocks and constraints on their provenance in the eastern segment of Central Tianshan Belt, Xinjiang

Sm-Nd isotopic characteristics, εNd(t) values and Nd model ages (TDM) of Proterozoic metasedimentary rocks in the eastern segment of Central Tianshan Belt (ESCTB), Xinjiang, are used to constrain the sedimentary provenance as well as to evaluate their tectonic implications. εNd(t) and TDM values of these samples range from -4.00 to +6.36 and from 1.29 to 2.29 Ga, respectively. These feature values are distinguished from those of Archean Tarim Craton. Their average εNd(t) values of the Weiya, the Kumishi and the south to the Dikar samples are -2.46, +2.06 and +1.37, respectively. Nd model ages of the Weiya samples vary between 1.86 and 2.29 Ga, but those of the Kumishi and the south to the Dikar samples show a significant concentration at 1.6～1.9 Ga and the youngest Nd model age is 1.29 Ga. Those Nd isotopic characteristics suggest that these metasedimentary rocks could be derived from a significant proportion of Paleoproterozoic crustal source and a participation of young arc materials, rather than Archean Tarim Craton. Furthermore, the data also indicate that these two sources were paleogeographically separated. Thus we can deduce that the Kumishi and the south to the Dikar metasedimentary rocks were formed proximal to the arc side of the back-arc basin, but the Weiya metasedimentary rocks were closer to the continental side of the back-arc basin.     

复杂条件下的低渗透油田生产特征

在考虑了启动压力、毛管力、重力等因素的情况下 ,推导了低渗透油田油水两相渗流时含水率和无因次采油、采液指数的数学模型 ,并分析了上述 3种因素在数学模型中的作用。结果表明 ,对于水湿油藏 ,毛管力和启动压力的存在使含水率和无因次采液指数增加 ,重力则使无因次采液指数降低 ,而对含水率的影响与地层倾角有关。 3种因素均对无因次采油指数无影响。在理论分析的基础上 ,对胜利油区大芦湖低渗透油田的含水率和无因次采油、采液指数进行了实例计算 ,进一步验证了理论分析结果的可靠性     

舟桥丙丁接头接触分析的计算机模拟

深入考察接触行为的特点，并以舟桥纵向连接件丙丁接头为例，建立了两种接触计算模型。采用大型通用有限元程序进行分析，模拟丙丁接头受力时的应力应变。与经验合成计算结果和常规有限元分析的结果进行对比，证明接触分析方法对连接件塑性变形、疲劳分析和优化设计有重要的指导意义。     

Evolution of the South China Sea and monsoon history revealed in deep-sea records

As the third summary report of ODP Leg 184 to the South China Sea (SCS), this paper discusses the evolution of the East Asian monsoon and the SCS basin. A multi-proxy approach, involving geochemistry, micropale-ontology, pollen and other analyses, was adopted for reconstructing the evolutionary history of the East Asian monsoon, which was characterized by a series of paleo-climate events especially at 8, 3.2, 2.2 and 0.4 Ma. The new record indicates similar stages in the development of the East and South Asian monsoons, with an enhanced winter monsoon over East Asia being the major difference. The rich spectrums of monsoon variability from the southern SCS also reveal other characteristic features of the low latitude ocean. Evidence for the evolution of the SCS includes the hemipelagic Oligocene sediments, implying the existence of deep water environments during the early seafloor spreading stage of the SCS basin. The four major unconformities and some remarkabl ediagenetic features in upper Oligocene deposits indicate the strongest tectonic events in the region. From a careful comparison of lithologies and sedimentation rates, we conclude that the prominent differences in sedimentary environments between the southern and northern SCS were established only by ～3 Ma.