Fractal-like Matrices

We introduce special sparse n×n-matrices (n=2 ^k ) containing up to 3 ^k ≈n ^1.585 nonzero elements. Their structure is inherited from the famous Sierpinski triangle and is not sensitive to matrix multiplication and inversion. The arithmetical complexity of taking product or inverse of such matrices is proved to be O(n ²).     

An Alternative Algorithm for a Sliding Window ULV Decomposition

The ULV decomposition (ULVD) is an important member of a class of rank-revealing two-sided orthogonal decompositions used to approximate the singular value decomposition (SVD). The ULVD can be modified much faster than the SVD. When modifiying the ULVD, the accurate computation of the subspaces is required in certain time varying applications in signal processing. In this paper, we present an updating algorithm which is suitable for large scaled matrices of low rank and as effective as alternatives. The algorithm runs in O(n²) time.     

三峡输电工程用ACSR-720/50导线制造的几个关键技术的探讨

三峡输电工程龙泉至政平± 5 0 0 k V直流输电线路用 ACSR- 72 0 /5 0 (钢芯铝绞线 )导线是迄今为止我国最大截面的输电用导线。本文介绍了在制造该导线时的几项关键技术。     

A Note on the Energy Norm for a Singularly Perturbed Model Problem

This paper considers a singularly perturbed reaction diffusion problem. It is investigated whether adaptive approaches are successful to design robust solution procedures. A key ingredient is the a posteriori error estimator. Since robust and mathematically analysed error estimation is possible in the energy norm, the focus is on this choice of norm and its implications. The numerical performance for several model problems confirms that the proposed adaptive algorithm (in conjunction with an energy norm error estimator) produces optimal results. Hence the energy norm is suitable for the purpose considered here. The investigations also provide valuable justification for forthcoming research. Received October 25, 2001; revised July 12, 2002 Published online: October 24, 2002     

丰满电厂凸极发电机的稳态安全运行图

用同步电机理论绘制出丰满电厂凸极发电机的稳态安全运行参量图和相应的Ｖ形曲线图。文中还介绍了该图的使用方法。并且提出了一个关于凸极发电机Ｖ形曲线与隐极发电机Ｕ形曲线区别的新观点。     

塔克拉玛干沙漠北缘新和县"百里风区"生态林建设效益分析

塔克拉玛干沙漠北缘新和县"百里风区"生态环境日趋恶化,严重危及了当地的社会与经济可持续发展.为此,阿克苏地委提出利用该地区渭干河、喀拉玉尔滚河汛期洪水和农一师塔北截洪排拦截洪水在"百里风区"建设生态公益林6.52×104 hm2的项目.其中人工生态林草区面积2.05×104 hm2,自然封育区面积4.47×104 hm2.该项目实施所产生的社会效益、生态效益比较显著.从生态环境保护的角度来看,不但可以改善新和县"百里风区"脆弱的生态环境,而且还可涵养水源,在一定程度上阻止塔克拉玛干沙漠向北扩展,对塔里木河流域的生态环境改善至关重要.     

Construction and Arithmetics of <Emphasis Type="Italic">H</Emphasis>-Matrices

In previous papers hierarchical matrices were introduced which are data-sparse and allow an approximate matrix arithmetic of nearly optimal complexity. In this paper we analyse the complexity (storage, addition, multiplication and inversion) of the hierarchical matrix arithmetics. Two criteria, the sparsity and idempotency, are sufficient to give the desired bounds. For standard finite element and boundary element applications we present a construction of the hierarchical matrix format for which we can give explicit bounds for the sparsity and idempotency.     

Full Scale Burn Tests of Television Sets and Electronic Appliances

Ten full-scale burn tests of television sets and electronic appliances were performed to: (1) demonstrate the ignition propensity and fire performance characteristics of materials used in the construction of television sets marketed in the United States and to compare these to the fire performance of television sets marketed in Europe; (2) document the damage to television sets when exposed to nearby burning materials; (3) evaluate and compare the damage to television sets when subjected to different size, duration and types of fires; (4) evaluate fire damage to television sets and electronic appliances when exposed to post flashover conditions; and (5) evaluate electrical damage caused to components of electronic appliances while they are powered and subjected to exposure fires.Ignitability tests showed that television sets constructed with cabinets made of V-0 rated plastics (for the U.S. market) will not ignite and propagate a flame under the test conditions. Television sets made of HB rated plastics (for the European market) will ignite and propagate a flame under the same test conditions and the television set will be consumed in the ensuing fire. The UL 94 tests do not provide rate of heat release data; however, calorimetry test data showed that the rate of heat release and the burning of the electronic appliances and television sets were in part dependent on the size of the exposure fire.Examination of the television sets and electronic appliances after the burn tests showed that the severity of damage and type of damage varied significantly. Electrical fault activity was noted to have occurred both exterior and interior to the powered television sets as well as other powered electronic appliances. In all cases, the fire source was external to the appliance.Post fire examination after the flashover fires showed that fire pattern analysis and burn damage are not necessarily indicative of the area of origin or cause and can be misleading to even experienced fire investigators.     

5.8 GHz无线网桥在电视节目传输中的应用

5.8GHz无线网桥是一种高速、无线以太网桥,支持点对点和点对多点的网络结构,对于作业现场分布散落、有线网络不能到达的地方,它提供一个高速传输通道,同时无线接入作为有线接入的重要补充和应急备份,节省了大量的建设费用,能够实现快速建设和快速投入使用。     

二维量子力学效应对阈值电压的影响

在亚50nm的MOSFET中,沿沟道方向的量子力学效应严重影响了器件性能.基于WKB理论,考虑MOSFET中该效应对垂直沟道方向上能级的影响,引入了其时阈值电压的修正.继而对沟道方向的子带作了抛物线近似并进行了数值拟合,从而建立了一个考虑量子力学效应的全解析模型.由此模型可以得到二维量子力学修正和沟道长度以及其它器件参数的关系.与数值模拟结构比较可以得出如下结论:在亚50nm的MOSFET中,量子力学效应引入了阈值电压的修正是不可忽略的.且此全解析模型精度令人满意.