SIMS characterization of HgCdTe and related II-VI compounds

The production of consistent high purity materials is critical for improvement in performance and sensitivity of II-VI photovoltaic and photoconductive devices. Information regarding the energy band structure and impurity or defect levels present in the material is essential to understand and enhance the performance of current detectors along with the development of future novel devices. Secondary ion mass spectrometry (SIMS) is capable of providing information of purity, junction depths, dopant distribution, and stoichiometry in the material. SIMS techniques can achieve high detection sensitivities in very small analytical volumes and for a wide range of elements (almost the entire periodic table). SIMS analysis also provides unique capabilities for localizing atomic distribution in two and three dimensions. Ion images can be obtained by registering the positions of mass selected ions formed in the sputtering process. The combination of excellent detection sensitivity, high mass resolution, depth profiling capability, and high resolution image acquisition on a wide spectrum of elements by a SIMS instrument is not matched by any other instrumentation technique.     

Yang-Mills and Dirac fields in a bag,constraints and reduction

The structure of the constraint set in the Yang-Mills-Dirac theory in a contractible bounded domain is analysed under the bag boundary conditions. The gauge symmetry group is identified, and it is proved that its action on the phase space is proper and admits slices. The reduced phase space is shown to be the union of symplectic manifolds, each of which corresponds to a definite mode of symmetry breaking.Research partially supported by NSERC Research Grant SAP0008091.Research partially supported by DFG Grant Schw. 485/2-1.Research partially supported by NSERC Research Grant OGP0042416.     

Molecular Control of Bioactivity in Sol-Gel Glasses

Bioactive materials can be divided into: Class A bioactive glasses which exhibit rapid bonding to bone and soft connective tissue and are osteoproductive, and osteoconductive; and Class B bioactive ceramics, which bond slowly only to bone and are only osteoconductive. Bioactive sol-gel glasses composed of SiO2-CaO-P2O5 have Class A behavior in vitro and in vivo and also resorb as they enhance the proliferation of new trabecular bone.     

Synthesis of terminally substituted stilbene-tolane liquid crystals

Methods for synthesizing substituted alkyl and fluoro stilbene-tolane (PTPDP) liquid crystal materials are presented. These compounds show a slightly higher birefringence than the analogous bistolanes, but higher melting points and heats of fusion. Potential applications of these compounds for optical communications and displays are discussed.     

An inter-comparison of far-infrared line-by-line radiative transfer models

A considerable fraction (>40%) of the outgoing longwave radiation escapes from the Earth's atmosphere-surface system within a region of the spectrum known as the far-infrared (wave-numbers less than 650 cm⁻¹). Dominated by the line and continuum spectral features of the pure rotation band of water vapor, the far-infrared has a strong influence upon the radiative balance of the troposphere, and hence upon the climate of the Earth. Despite the importance of the far-infrared contribution, however, very few spectrally resolved observations have been made of the atmosphere for wave-numbers less than 650 cm⁻¹. The National Aeronautics and Space Administration (NASA), under its Instrument Incubator Program (IIP), is currently developing technology that will enable routine, space-based spectral measurements of the far-infrared. As part of NASA's IIP, the Far-Infrared Spectroscopy of the Troposphere (FIRST) project is developing an instrument that will have the capability of measuring the spectrum over the range from 100 to 1000 cm⁻¹ at a resolution of 0.6 cm⁻¹. To properly analyze the data from the FIRST instrument, accurate radiative transfer models will be required. Unlike the mid-infrared, however, no inter-comparison of codes has been performed for the far-infrared. Thus, in parallel with the development of the FIRST instrument, an investigation has been undertaken to inter-compare radiative transfer models for potential use in the analysis of far-infrared measurements. The initial phase of this investigation has focused upon the inter-comparison of six distinct line-by-line models. The results from this study have demonstrated remarkably good agreement among the models, with differences being of order 0.5%, thereby providing a high measure of confidence in our ability to accurately compute spectral radiances in the far-infrared.     

A Frequency Selection Criterion in Spatially Developing Flows

The possible existence of global modes or self-excited linear resonances in spatially developing systems is explored within the framework of the WKBJ approximation. It is shown that the existence and properties of the dominant global mode may be deduced from the variations of the local absolute frequency ω₀ with distance X. The main results are summarized in two theorems: (1) A system with no region of absolute instability does not sustain temporally growing global modes with an O(1) growth rate. (2) If the singularity X, closest to the real X-axis of the complex function ω₀(X) is a saddle point, the most unstable global mode has, to leading order in the WKBJ approximation, a complex frequency ω₀(X_s). Thus, it will be temporally growing only if ω₀(X_s) is positive.     

Heuristics for Two-Level Hierarchical Transportation Networks

Given a set of points, we wish to design a network consisting of a primary link and a set of secondary links connecting the points to the primary link. The objective of the problem is to find the location and length of the primary link in order to minimize the sum of its weighted length and the weighted lengths of all secondary links. We assume that the weight of the secondary link from any point varies depending on the location of that point. In this paper, we describe efficient algorithms and their computer implementation for two scenarios of this problem. In the first scenario, only direct secondary links are allowed from each point to the primary link. In the second scenario, the secondary link from a point is allowed to pass through other points before reaching the primary link.     

可配置的媒体处理器:无线多媒体解决方案

线多媒体依赖于复杂的视频软件/服务器技术，而流视频和音频的生成又依赖复杂的处理技术。有一种产品无疑会从无线多媒体技术中得益，这就是个人数字助理(PDA)。然而，不同的PDA所采用的微处理器性能水平不同，如某些支持低帧速率的视频流和用软件处理低分辨率，而另有一些则不支持任何类型的视频流。一个能支持高质量双向视频通信的PDA的系统需要很强的系统计算能力。提高性能的方法之一是采用常见的小型接口标准，如PCMCIA卡和CF卡，最新的PDA都支持这些接口标准。高级视频和无线处理系统都可以采用PCMCIA和CF电路卡的标准进…