Microfabricated preconcentrator-focuser for a microscale gas chromatograph

The design, fabrication, and testing of a preconcentrator-focuser (PCF), consisting of a thick micromachined Si heater packed with a small quantity of a granular adsorbent material are described. The PCF is developed to capture and concentrate vapors for subsequent focused thermal desorption and analysis in a micro gas chromatograph. The microheater contains an array of high-aspect-ratio, etched-Si heating elements, 520 /spl mu/m (h)/spl times/50 /spl mu/m (w)/spl times/3000 /spl mu/m (l), bounded by an annulus of Si and thermally isolated from the remaining substrate by an air gap. This structure is sandwiched between Pyrex glass plates with inlet/outlet ports that accept capillary tubes for sample flow and is sealed by anodic bonding (bottom) and rapidly annealed glass/metal/Si solder bonding (top). The large microheater surface area allows for high adsorption capacity and efficient, uniform thermal desorption of vapors captured on the adsorbent within the structure. The adsorbent consists of roughly spherical granules, /spl sim/200 /spl mu/m in diameter, of a high-surface-area, graphitized carbon. Key design considerations, fabrication technologies, and results of performance tests are presented with an emphasis on the thermal desorption characteristics of several representative volatile organic compounds as a function of volumetric flow rates and heating rates. Preconcentration factors as high as 5600 and desorbed peak widths as narrow as 0.8 s are achieved from 0.25-L samples of benzene at modest heating rates. The effects of operating variables on sensitivity, chromatographic resolution, and detection limits are assessed. Testing of this PCF with a micromachined separation column and integrated sensor array is discussed briefly.     

企业信息化中的网络存储整合应用

首先介绍了网络存储技术中NAS技术和SAN技术的基本原理,并对两者的特性进行了比较;然后详细介绍了企业信息化过程中网络存储整合的一个典型案例,分析了其整合前存在的不足,制定有效的整合实施方案,并对实施过程中许多关键技术部分进行了阐述,最终很好的达到了预定目标;最后总结了网络存储整合需要规划多种技术相融合的必要性.     

High-cycle fatigue characterization of titanium 5Al-2.5Sn alloy

High-cycle fatigue behaviour of titanium 5Al-2.5Sn alloy at room temperature has been studied. S-N curve characterization is performed at different stress ratios ranging from 0 to 0.9 on a subsized fatigue specimen. Both two-stress and three-stress level tests are conducted at different stress ratios to study the cumulative fatigue damage. Life prediction techniques of linear damage rule, double linear damage rule and damage curve approaches are applied, and results are compared with the experimental data. The agreement between prediction and experiment is found to be excellent.     

Amplification and expression of c-erbB2 oncogene in normal, hyperplastic, and malignant endometria

OBJECTIVE: To study the correlation of development and survival with amplification of c-erbB2 oncogene in endometrial carcinoma. METHODS: The amplification and expression of c-erbB2 oncogene were determined from formalin-fixed, paraffin-embedded tissues of 25 normal, 31 hyperplastic, and 72 malignant samples of the endometrium in 128 patients, using differential polymerase chain reaction (DPCR) and an immunohistochemical technique. RESULTS: Amplified c-erbB2 (2 to 12 copies) were found in two of 25 (8.0%) normal, 15 of 31 (48.4%) hyperplastic, and 45 of 72 (62.5%) malignant samples. When the results of DPCR were compared with those of the immunohistochemical method, the negative findings concide well with one another, i.e., nonamplification was associated with the absence of immunoreactivity. It was noted that the amplified c-erbB2 was found more significantly in complex and a typical hyperplasias than in simple hyperplasias. The high-level c-erbB2 amplification (at least five copies) was significantly correlated with the histological grade of endometrial carcinoma and vascular or lymphatic invasion. No correlation was seen between c-erbB2 amplification and overall survival in the present group of patients. CONCLUSIONS: The amplified c-erbB2 may play a potential role in the early development of some endometrial carcinomas. The high-level c-erbB2 amplification may identify a subset of aggressive endometrial carcinoma that involves vascular or lymphatic invasiveness and poor cell differentiation playing the role of a marker for clinical prognosis.     

基于公共存储器进行数据交换的高速数字图象处理系统

本文介绍了一种基于公共存储器进行数据交换的高速数字图象处理系统．给出了公共存储器的设计，描述了处理器对公共存储器的进程同步控制．     

Optimal Hybrid Control for Structures

A new method for integrated design of passive and active elements is presented. Rather than the existing qualitative selection of parameters for passive elements, a quantitative approach is proposed that finds optimal active and passive parameters with respect to an H₂/H_∞ performance requirement. This new approach automatically yields passive designs when the given performance limits are high enough and active (hybrid) designs when the given performance constraints are stringent. Furthermore, our algorithm finds the special performance requirement (the peak of the frequency response) that cannot be satisfied by any passive design. Hence this article shows how to determine when control is required rather than assuming a priori that it is or is not required. A simple design method given herein yields either passive, active, or hybrid designs depending only on the level of the performance constraints that are specified in the statement of the problem.     

Direct imaging of a high-power diode laser cavity using a transparent indium-tin-oxide (ITO) contact

We describe a novel "see-through" indium-tin-oxide contact on the n-side of a high power unstable resonator semiconductor laser (URSL) that allows direct observation of the cavity during high power operation. Under optimized annealing conditions this transparent ITO contact has a low enough specific contact resistivity to permit normal high power CW operation of the URSL and allows the observation of filamentation. This contact scheme is applicable to a wide range of semiconductor lasers and is especially appropriate for high power devices. The same structure can also be used to obtain a 2-D thermal map of the laser cavity.     

观赏草在庭园中的设计与应用

观赏草以其灵动的景观特质，草类特有的自然色调，飘逸的质感越来越受到设计师们的青睐，用于焦点、绿蒿、花镜、镶边均有不凡的表现，虽为草类，却有着灌木的功能。     

ρ-混合噪声中ρ-混合信号Min-Max检测的注记

本文考察了ρ-混合噪声中ρ-混合随机信号的 Min-Max 检测问题.首先,将[5]中(?)-混合条件减弱为ρ-混合相依条件;其次,去掉了[5]中式(5)(?)r_n<∞的限制条件;第三,将[5]中常值的弱信号拓广到具有ρ-混合相依的随机信号,故本文改进了[5]中结果.