边界层吸入对方转圆进气道、风扇耦合影响

针对方转圆S弯进气道及风扇部件吸入进口边界层的影响问题,采用定常与非定常CFD数值模拟方法模拟并分析了进口吸入不同高度边界层时进气道、风扇部件的总体特性和流场特征,数值结果表明:随着进口边界层吸入厚度增加,进气道出口稳态周向总压畸变指数增大,风扇进口畸变区总压亏损增加、流量系数降低、相对气流角增大。但畸变区范围没有明显增加,进气道和风扇总体性能受进口边界层增厚影响不明显。受风扇增压作用影响,出口气流参数沿周向的畸变度得到有效削弱。     

涡轮风扇发动机紧凑压缩系统气动性能

通过数值方法研究了由2级风扇、4级高压压气机及外涵组成的紧凑压缩系统的气动性能.探讨了双涵双轴压缩系统气动性能的评估方法及数值计算中相应的边界给定方法.通过对紧凑压缩系统的一体化数值模拟,分别获取了风扇及高压压气机的设计转速特性,并与设计值进行了对比,结果表明流量、压比、效率都达到了设计要求,而风扇失速裕度仅为7.8%...     

一种基于遥测数据压缩的硬件系统设计与实现

在基于遥测数据特点的背景下,提出了一种遥测数据实时无损压缩系统的设计方案。在这个压缩系统中,采用小波变换的方法对数据信号进行去噪预处理,能够有效减少数据量。同时,处理后的数据采用基于字典的LZW无损压缩算法,能够无失真地还原信号,这也正是遥测数据所要求的。     

一种适合星载多光谱图像的压缩算法研究

文章提出了一种适合星载多光谱（4个谱段）图像压缩方法,根据多光谱图像之间相关性较强和卫星对地通道传输速率有限的特点,利用谱段变换,调整各谱段之间的信息量分配,形成新的谱段数据,并对新谱段数据压缩比进行适当调整,完成多光谱图像数据压缩。采用此算法后,可以使平均压缩比不变的情况下,4个谱段恢复的多光谱图像大部分峰值信噪比（Peak Signal Noise Ratio,PSNR）与直接压缩图像后的PSNR值相比有所提高。     

基于壁面压力分布的二元高超声速弯曲激波压缩进气道反设计与优化方法

为进一步提高高超声速进气道的性能,发展了通过指定压力分布规律来反设计整个二元进气道的方法,实现了气动参数可控的进气道内外压缩一体化设计,建立了基于Isight软件的进气道自动化设计分析和优化平台。初步的研究表明,使用此设计方法,能够得到综合性能优秀的进气道设计方案,该方案在来流马赫数6下喉道总压恢复系数为0.68,在来流马赫数4时流量系数达0.77。      

静态图像无损/近无损压缩技术研究

针对航空侦察图像的原始分辨率高,且在存储过程中必须进行无损或者近无损图像压缩的问题,为满足任务判读的要求,实现实时高效的数据压缩处理具有重要的工程价值。本文首先比较了几种无损或者近无损图像压缩的硬件平台,然后介绍了JPEG标准族的无损/近无损图像压缩的算法框架和不足,最后阐述了最近刚正式问世的新一代JPEG XR图像压缩标准,并指出了JPEG XR标准的优势所在。     

STUDY ON THE POST-STALL BEHAVIOR OF AN AXIAL-FLOW COMPRESSION SYSTEM

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The study of enhanced earth observations on a satellite image chain

The Multi-Spectral Camera (MSC) on the KOrea Multi-Propose SATellite (KOMPSAT)-2 was developed and launched as a main payload to provide a One(1) m panchromatic image and four(4) band four(4) m multi-spectral images at an altitude of 685 km covering a swath width of 15 km. These images, archived around the world, are a useful resource for space applications in agriculture, cartography, geology, forestry, regional planning, surveillance, and national security. The image quality of KOMPSAT-2 depends upon its image chain, which is comprised of an on-board system in the satellite and a processing system at the ground station. Therefore, in this study we determine the factors that have a major impact on the image quality through an investigation of the entire image chain. Consequently, two methods, involving a compression algorithm and a deconvolution technique, were determined as having a significant influence on the KOMPSAT-2 image quality. The compression algorithm of KOMPSAT-2 is rate-controlled JPEG-like algorithm that controls the mismatch between the input and output data rate. The ability to control the input/output data rate may be useful during the operation of the satellite but can also lower the overall image quality. The deconvolution technique may increase the sharpness of images, but it can also amplify the image noise level. Therefore, we propose methods of wavelet-based compression and denoising as an alternative to currently existing algorithms. Satisfactory results were obtained through experimentation with these two algorithms, and they are expected to be successfully implemented into the future KOMPSAT series to yield high-quality images for enhanced earth observation.     

Establishment criteria,routing algorithms and probability of use of inter-satellite links in mixed navigation constellations

In this paper, the establishment criteria, routing algorithm and the probability of use of ISLs (inter-satellite links) in the mixed navigation constellation of GEO satellites, IGSO satellites and MEO satellites are analyzed. Firstly, the general criteria of ISL establishment in mixed navigation constellation are proposed from the perspective of geometry, and the influences of these criteria on routing algorithms and the probability of use of ISLs are discussed. Then, from the perspective of autonomous orbit determination, the routing algorithm in mixed navigation constellation is designed. Thirdly, a stochastic study of ISLs load in mixed navigation constellation is proposed, and the formulae of probability of use of ISLs are given. Finally, in the simulation, the establishment criteria, routing algorithm and the probability of use of ISLs in a specific mixed navigation constellation of 3GEO + 3IGSO + 24MEO are discussed in detail. The findings of this paper provide a basis for the ISL establishment and routing algorithm, and offer the quantitative indicators for the use of ISL in the mixed navigation constellation.     

卫星遥感图像分块小波变换编码方案

提出一种分块小波变换（ＢｌｏｃｋｉｎｇＷａｖｅｌｅｔｓＴｒａｎｓｆｏｒｍ）方案。该数据压缩方案可节省存储时间，为星上应用提供了可能性。利用各基带之间的自相似性，对小波系数采用改进型零树编码（ＩｍｐｒｏｖｅｄＺｅｒｏｔｒｅｅＥｎｃｏｄｉｎｇ），可有效的提高压缩比。