Mechanism of frost heave by film water migration under temperature gradient

Conclusions Based on the principle of freezing point superposition, a model for predicting unfrozen water content is worked out and it can consider the influences of five factors: soil variation, water content, temperature, solution concentration and overburden pressure. The difference of values between determination and calculation is less than 3 %. According to the curve of unfrozen water content vs. temperature and initial freezing point and temperature at the cold end of soil body, a way for estimating ice segregation temperature is presented. The difference of values between determination and calculation is less than 0.3°C. The thickness of frozen fringe changing with time has three models. The calculation method needs further study.     

最小直线斯坦纳树及其在详细布线中的应用

在面向区域的详细布线中,最小直线斯坦纳树(MRST)可为单个线网产生满足连线最短要求的最佳初始布线模式,可为全局最优布线大大减小搜索空间。一般说,构造MRST是NP完备问题,为了降低问题的复杂度,需要研究生成MRST的实用有效算法。本文讨论了两种这样的算法,并结合例题说明,MRST只是局部最优树,在实际布线应用中要综合考虑其它布线质量因素,对当前线网的初始MRST进行调整或动态修改。     

分布参数系统的顺流型热交换器的渐近近似法与预测控制Smith法补偿

分布参数系统由于是偏微分方程描述,具有无限维的特性。在极大多数情况下,无法求到它的精确解,而且求解也相当繁复。因此不少研究分布参数系统的科学工作者对这方程式近似方法进行了大量的研究,如差分法,特性曲线法和MWR法等;或者把分布参数系统近似成集中参数系统,或者把高价方程简化为低阶方程等。在此基础上再进行系统设计,加以补偿,以得到良好的系统特性。本文以典型的顺流型热交换器为例,介绍此类分布参数系统的另一种渐近近似法,并在此基础上用预测控制Smith 法进行补偿,给出计算机仿真结果,从根据轨迹角度来探讨补偿结果     

提高闪光灯泵浦的三重染料激光器效率的研究

从灯泵多重染料激光器能量转换机理出发,在灯泵染料激光器中使用三重染料,使激光器更好满足应用要求．     

煤层采空区勘探新方法与新技术应用效果初探

文章介绍了应用瞬变电磁法(TEM)和可控源音频大地电磁测深法(CSAMT)在山西省汾西矿业集团柳湾煤矿探测煤层采空区、积水区的应用方法和效果,说明了这两种方法在煤层采空区探测领域有着广泛的应用前景.     

Kofi Annan Visited Beijing Liuminying Eco-village

United Nations Secretary-General Kofi Annan and his party visited China‘s first large agricultural ecology project,Beijing Liuminying Eco-village, on October 12, 2004. During his visit, Kofi Annan was accompanied by Xie Zhenhua,Minister of the State Environmental Protection Administration (SEPA), Wang Guangya, Permanent Representative to the United Nations,     

基于图案信号的选择反应时测试仪的研制

反应时测试广泛应用于医学、药学、卫生学、心理学、体质测试等基础研究和实际工作中。由于计算机选择反应时测试精度高、稳定性好，故在反应时测定中应用得越来越多。本文采用AT89C52和LED开发基于图案信号的选择反应时测试仪，其图案显示形式、时间等均为随机，较好地仿真了现实环境，赋予选择反应时以特定的职业特性，将有利于促进相关心理学与体育学等领域反应时的研究与应用。     

Web Services内部架构对QoS的影响

为了研究Web Services的内部构建对Web Services服务质量(QoS)的影响,设计了对应的ACTTest程序来分析Web Services内部构建中的字符串连接连接方法、数据库操作方式、序列化、输出缓存、调用开销及集群等对Web Services的QoS影响,结果表明Web Services内部构建对QoS有着重要影响。实验结果对优化Web Services的内部架构和网络结构,提高网络及WS的性能和可扩展性具有重要意义。     

Water content in the transition zone from electrical conductivity of wadsleyite and ringwoodite

The distribution of water in the Earth's interior reflects the way in which the Earth has evolved, and has an important influence on its material properties. Minerals in the transition zone of the Earth's mantle (from approximately 410 to approximately 660 km depth) have large water solubility, and hence it is thought that the transition zone might act as a water reservoir. When the water content of the transition zone exceeds a critical value, upwelling flow might result in partial melting at approximately 410 km, which would affect the distribution of certain elements in the Earth. However, the amount of water in the transition zone has remained unknown. Here we determined the effects of water and temperature on the electrical conductivity of the minerals wadsleyite and ringwoodite to infer the water content of the transition zone. We find that the electrical conductivity of these minerals depends strongly on water content but only weakly on temperature. By comparing these results with geophysically inferred conductivity, we infer that the water content in the mantle transition zone varies regionally, but that its value in the Pacific is estimated to be approximately 0.1-0.2 wt%. These values significantly exceed the estimated critical water content in the upper mantle, suggesting that partial melting may indeed occur at approximately 410 km depth, at least in this region.     

一类代数方程组反问题的牛顿迭代法

本文对一类代数方程组反问题提出了一个可行的迭代解法。从算法上看,它是一种解正问题—迭代—解正问题迭代改善的求解过程。