Study on the propagation of inlet flow distortion in axial compressor using an integral method

 An integral method is investigated and developed in the current work. The effects of the parameters of inlet distortions on the trend of downstream flow feature in compressor are simulated. Other than the drag-to-lift ratio of the blade and the inlet incidence angle, it is found that the distorted inlet velocity is another essential parameter to control the distortion in propagation. Based on this study, a novel critical distortion line and corresponding critical distortion factor are proposed to express the effect of the two essential inlet parameters on the propagation of distortion, namely, the inlet incidence angle and the distorted inlet velocity. From the viewpoint of compressor efficiency, the propagation of inlet flow distortion is further described by a compressor critical performance and its critical characteristic. The results present a useful physical insight to an axial flow compressor behavior and asymptotic behavior of the propagation of inlet distortion, and confirm the active role of compressor in determining the velocity distribution when compressor responds to an inlet flow distortion. Received: 20 December 2001 / Accepted: 21 August 2002 The authors would like to thank HQ RSAF for permission to publish this work, their financial support and encouragement. The first author wants to acknowledge Prof. Frank Marble of California Institute of Technology, for bringing the problem to the author's attention and for his helpful discussion.     

高职高专电工学课程教学改革

针对高职高专培养应用型人才的要求，分析了目前电工学课程教学的现状，提出了电工学课程改革方案。     

Pd-Ge contact to n-GaAs with the TiW diffusion barrier

Pd-Ge based ohmic contact to n-GaAs with a TiW diffusion barrier was investigated. Electrical analysis as well as Auger electron spectroscopy and the scanning electron microscopy were used to study the contact after it was subjected to different furnace and rapid thermal annealing and different aging steps. All analyses show that TiW can act as a good barrier metal for the Au/Ge/Pd/n-GaAs contact system. A value of 1.45 × 10⁻⁶ Ω-cm² for the specific contact resistance was obtained for the Au/TiW/Ge/Pd/n-GaAs contact after it was rapid thermally annealed at 425°C for 90 s. It can withstand a thermal aging at 350°C for 40 h with its ρ_c increasing to 2.94 × 10⁻⁶Ω-cm² and for an aging at 410°C for 40 h with its ρ_c increasing to 1.38 × 10⁻⁵ Ω-cm².     

Surface leakage currents in SiN/sub x/ passivated AlGaN/GaN HFETs

A novel guarded surface leakage test structure is used to isolate the surface and bulk leakage contributions to gate current in AlGaN/GaN HFETs. Passivation with various recipes of SiN/sub x/ always resulted in the commonly observed increase in gate leakage, which was found to be dominated by bulk leakage through the AlGaN. However, high temperature deposited SiN/sub x/ recipes gave a 1-2 orders reduction in surface leakage, whereas low temperature deposition gave an increase. Gate lag measurements were found to correlate closely with the surface leakage component, giving direct evidence that the key device problem of current slump is associated with current flow at the AlGaN surface.     

多组分间歇精馏工艺计算探讨

介绍用“微元时段”计算多组分间歇精馏的方法。     

Field dependence of impact ionization coefficients in In/sub 0.53/Ga/sub 0.47/As

Electron and hole ionization coefficients in In/sub 0.53/Ga/sub 0.47/As are deduced from mixed carrier avalanche photomultiplication measurements on a series of p-i-n diode layers, eliminating other effects that can lead to an increase in photocurrent with reverse bias. Low field ionization is observed for electrons but not for holes, resulting in a larger ratio of ionization coefficients, even at moderately high electric fields than previously reported. The measured ionization coefficients are marginally lower than those of GaAs for fields above 250 kVcm/sup -1/, supporting reports of slightly higher avalanche breakdown voltages in In/sub 0.53/Ga/sub 0.47/As than in GaAs p-i-n diodes.     

一种基于自然数线性八叉树的优化构造算法

本文提出了一种基于自然数线性八叉树的优化构造算法。该算法以活动结点表为中间辅助结构，在图像输入过程中直接生成基于Ｎ码的八叉树叶结点．与常规构造算法相比，新提出的优化构造算法省去了Ｎ码的计算及合并过程，从而具有较高的时空效率．