Simulation study of peak junction temperature and power limitationof AlGaAs/GaAs HBTs under pulsed and CW operation

The authors have used a 3-D transmission-line matrix (TLM) modeling method to study the junction temperature distribution and power limitation of device geometries with multiple embedded heat sources. Peak values of the junction temperature against the dissipated power density under both pulsed and CW operation are presented for a typical power AlGaAs/GaAs HBT structure. These data should facilitate the rapid determination of junction temperature for a given output power, which is of paramount importance in power device design     

CHEMICAL VAPOR DEPOSITION OF SILICON ONTO IRON AND STEEL SUBSTRATES: OXIDATION AND CORROSION PROPERTIES OF COATED MATERIALS

The influence of the gaseous phase composition (SiH₄ or SiCI₄ diluted with argon or hydrogen), used for chemical vapor deposition of silicon onto two different substrates (pure iron or low chromium mild steel) is investigated. Depending on the chosen process, two types of coatings are developed: either a very adherent, non-porous solid solution containing up to 6 to 7 wt. % Si, or a Fe₃Si iron silicide (14.35 wt. %). This solid solution coating considerably improves the oxidation resistance properties of steels at temperatures up to 800° C. This beneficial effect was not observed on the corrosion behavior of treated samples in sulfuric acid solutions. In contrast, the Fe₃Si iron silicide has the same outstanding corrosion resistance that the silicon-rich cast alloys have in very severe environments such as boiling concentrated sulfuric acid. But this remarkable behavior is certainly limited in other mediums by the open porosity of the coating, inherent to the chemical vapor process.     

高效液相色谱法测定头孢拉定制剂方法的改进

目的:改进头孢拉定制剂含量测定方法。方法:高效液相色谱条件:以Shim—Pack CLC—ODS(250mm×4.6mm)为色谱柱;柱温为35℃;流动相为水—甲醇—3.86％醋酸钠溶液-4％醋酸溶液(1364:500:30:6);流速为0.8mL·min~(-1);检测波长为254nm。结果:头孢拉定峰形良好,分离度和柱效满足药典要求,保留时间由原来的21.32min缩短至8.06min,提高了分析速度,含量测定结果与中国药典无显著差异。结论:该方法快速、准确、能更好地适用于常规检验工作和大批量生产时的质量控制。     

Encoded moire inspection based on a computer solid model

An investigation into a system linking a computer solid modeler to an active stereo imaging inspection station is presented. Given the computer solid model of a surface, a projected pattern can be encoded so that the reflections from the object's surface exhibit a uniformly simple pattern when the object's surface and the modeled surface are identical. Research concerning the method of generating projection patterns, as well as the sensitivity of the system, is discussed. A prototype system consisting of a computer graphics workstation; a flexible projector, and a machine vision system was used to inspect two different manufactured parts     

Two-dimensional map of Haemophilus influenzae following protein enrichment by heparin chromatography

Two-dimensional gel electrophoresis separates several hundred protein molecules in one single experiment and is efficiently used to study the products expressed by different genomes. Low-copy-number gene products are invisible on a stained two-dimensional map and must be enriched such that sufficient amounts are present for visualization and identification. We investigated the enrichment of proteins of the bacterium Haemophilus influenzae by chromatography on immobilized heparin which has affinity for growth and protein biosynthesis factors. Total soluble proteins of the microorganism were fractionated on Heparin-Actigel which resulted in enrichment of approximately 160 proteins. The eluates, representing about 40% of the applied proteins, were analyzed by two-dimensional gel electrophoresis and the protein spots were characterized by amino acid composition analysis and matrix-assisted laser desorption ionization mass spectrometry. The proteins enriched by chromatography on the heparin gel were not exclusively low-copy-number gene products and they did not exclusively belong to one single class of proteins. The proteins that bound to the heparin gel are indicated in a two-dimensional protein map which includes more than 110 newly identified proteins.     

NOTCHED FATIGUE BEHAVIOUR OF TWO COLD ROLLED STEELS

Abstract— A SAE1010 plain carbon steel and a SAE945X HSLA steel were cold rolled to various thickness reductions. Centre notched specimens were tested under stress control at a stress ratio of—1. The effect of loading direction on the fatigue strength was examined. The notched specimen fatigue strength was only slightly increased by cold rolling, since two opposing factors: the smooth specimen fatigue strength and the notch sensitivity, were increased by cold rolling. The notched specimen fatigue strength in the transverse direction was approximately the same as that in the longitudinal direction. An empirical equation and equations derived from fracture mechanics and Neuber's rule were applied to predict the fatigue notch factor for the sharp and blunt notch geometries examined. A reasonable agreement between the predictions and the experimental results was observed for the sharp notches. For the blunt notches, the predicted fatigue notch factors were conservative.