Multitemporal passive microwave mapping in MACHYDRO'90

MACHYDR0'90 was an experiment conducted in Pennsylvania in 1990 to study the synergistic use of remote sensors in multitemporal hydrologic studies. As part of this mission the pushbroom microwave radiometer was flown and used to produce brightness temperature maps. Verification studies and vegetation algorithms for mixed land cover areas are described     

平衡纵剖面数值试验及其对防洪的影响研究

本文采用一维非恒定流非均匀沙的水沙数学模型，以长江中游螺山汉口河段为背景，进行了根化数值模拟试验，分析了该概化河段平衡纵剖面的变化规律及其与上游来水来沙条件的关系，并和相应的理论公式进行了比较。在此基础上，对水沙条件发生较在变化时的平衡纵比降以及带来的对长江中下游防洪的影响进行了分析。     

混合结构楼房爆破拆除倒塌范围的确定

通过对混合结构楼房爆破倾倒过程特点的分析,提出了楼房在倾倒过程中的运动计算模型,并应用体积平衡原理,得到这类楼房爆破爆堆参数计算公式,用该公式计算的结果与实例中爆堆实测数据相比较,相对误差不超过11%.     

Analysis of tungsten and titanium migration during ESD contact burnout

A physical and chemical analysis of a machine model (MM) electrostatic discharge (ESD) failure in a silicon circuit was carried out. Focused ion beam (FIB) was used to make cross sections through the region of contact burnout. The resulting samples were analyzed using scanning electron microscopy (SEM) and two-dimensional (2-D) auger electron spectroscopic (AES) mapping. It is shown for the first time that both titanium (Ti) and tungsten (W) migrated throughout the melted silicon filament. Large pellets of the W plug were embedded in the bulk silicon but only on the cathode side of the junction. Mechanisms are discussed to explain these phenomena. These involve the melting of titanium disilicide (TiSi/sub 2/), dissolution of Ti and W in the molten silicon and the formation of W pellets through electromigration at temperatures below /spl sim/1800 K.     

XML在机械CAD系统中的应用

分析了Internet上最新的XML技术的特点，通过实例用XML技术对机械CAD产生的各种文档信息进行了描述，并且构造了基于XML文档交换的分布式支持环境的体系结构。     

Ab-initio primitive cell parameters from single convergent-beam electron diffraction patterns: a converse route to the identification of microcrystals with electrons.

A new method for the ab initio derivation of Buerger-reduced primitive cell parameters from coordinate measurements of spots on single convergent-beam electron diffraction (CBED) patterns is described, which does not involve trial-and-error. The pattern can be taken along any zone axis, and misorientations of the crystallite by as much as a few degrees are taken into account without loss of accuracy. This derivation of cell parameters by least-squares analysis of the measurements has been automated in a program called NRCBED. Present accuracy is about 1% on lengths and 2 degrees on angles, but could be significantly improved by modelling projector lens aberrations, or by using a microscope without a projector lens. With present technology, it is possible to obtain a CBED pattern and a semi-quantitative energy-dispersive X-ray (EDX) analysis simultaneously from a single microcrystal a few hundred Angstr?ms across. It becomes therefore possible to identify the material of the crystal on a single CBED pattern: a cell parameter database for known compounds is searched with the primitive cell parameters obtained in the above way, and with a mask describing the EDX results qualitatively. Feasibility is demonstrated on a crystallite of CeO2 500 Angstr?ms across. With this new approach, trial-and-error should disappear from the solution of other long-standing problems: interpretation of X-ray powder patterns for new compounds in the presence of impurity lines, or in the case of multiple phases should become straight-forward.     

Highly integrated direct conversion receiver for GSM/GPRS/EDGE with on-chip 84-dB dynamic range continuous-time /spl Sigma//spl Delta/ ADC

This paper describes a highly digitized direct conversion receiver of a single-chip quadruple-band RF transceiver that meets GSM/GPRS and EDGE requirements. The chip uses an advanced 0.25-/spl mu/m BiCMOS technology. The I and Q on-chip fifth-order single-bit continuous-time sigma-delta (/spl Sigma//spl Delta/) ADC has 84-dB dynamic range over a total bandwidth of /spl plusmn/135 kHz for an active area of 0.4 mm/sup 2/. Hence, most of the channel filtering is realized in a CMOS IC where digital processing is achieved at a lower cost. The systematic analysis of dc offset at each stage of the design enables to perform the dc offset cancellation loop in the digital domain as well. The receiver operates at 2.7 V with a current consumption of 75 mA. A first-order substrate coupling analysis enables to optimize the floor plan strategy. As a result, the receiver has an area of 1.8 mm/sup 2/.     

硅烷交联超高分子量聚乙烯

采用硅烷对超高分子量聚乙烯(UHMWPE)进行交联改性，系统地研究了交联UHMWPE的凝胶率、熔点、结晶度、力学性能与耐磨性。结果表明，硅烷偶联剂导致了UHMWPE的交联，使UHMWPE的凝胶率提高。当硅烷含量较低时，UHMWPE的熔点增高、结晶度增大；当硅烷含量较高时，UHMWPE的熔点、结晶度呈下降的趋势；硅烷交联导致了UHMWPE材料的模量和强度提高，磨耗率降低；当硅烷含量较高时，交联UHMWPE材料的力学性能和磨耗率均变差；当硅烷含量为0．2份～0．4份时，交联UHMWPE材料的综合性能最佳。     

A distributed approach for access and visibility task with a manikin and a robot in a virtual reality environment

This paper presents a new method, based on a multi-agent system and on a digital mock-up technology, to assess an efficient path planner for a manikin or a robot for an access and visibility task taking into account ergonomic constraints or joint and mechanical limits. In order to solve this problem, the human operator is integrated in the process optimization to contribute to a global perception of the environment. This operator cooperates, in real time, with several automatic local elementary agents. The result of this work validates solutions through the digital mock-up; it can be applied to simulate maintainability and mountability tasks.