低噪声500MHz频率源

本文介绍一种高可靠、长寿命频率源的设计。为了可靠的工作,该装置采用了备用结构型式,并用体波和声表面波谐振器来保证极低的相位噪声和寄生输出。500MHz 和400MHz 多路输出是由25MHz 参考输入或由一个内部100MHz 温度补偿晶体振荡器直接合成而产生的。当使用外部参考时,25MHz 输入滤波器和两个50MHz、100MHz 附加晶体滤波器保证在最后倍频之前将相位噪声本底减小到理论最小值。500MHz 倍频输出信号用两端口SAW 谐振器进行滤波。这些谐振器在50欧匹配系统中,工作的输入功率电平为+15dBm。滤波电路还保证将内外产生的调制边带减小到可以忽略的程度。在离载波大于2MHz 间隔频率上,其单边带相位噪声低于-174dBc/Hz。同样,在所有频率上,寄生信号均低于-110dBc。频率源工作在有电噪声的环境中。良好的有源、无源滤波和封装屏蔽可保证最小的导电和辐射敏感性。对系统的苛刻要求决定采用无单点故障的备用重复结构。提出的封装设想是使组件的内部连接最短,并使两个备用发生器在物理和电气上互不相关。     

边界层对可调节进气道性能的影响

给出了马赫数2-6、单位雷诺数（0．8-6．0）×10^7／m时下吹式风洞中可调节三维进气道的试验研究结果。研究了前缘前掠和后掠方案以及进气道人口前边界层的影响。测量了内流道内的压力分布、质量流量和总压恢复系数;确定了进气道启动与马赫数和流动工况的关系。研究结果表明：边界层对流场结构和模型进气道的性能有着决定性影响,相对简单的进气道调节方案可以增大其稳定运行范围。     

Short-wave infrared reflectance investigation of sites of paleobiological interest: applications for Mars exploration

Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instruments such as the Portable Infrared Mineral Analyser (PIMA, Integrated Spectronics Pty Ltd., Baulkham Hills, NSW, Australia) fulfill all these requirements. We describe an investigation of a possible Mars analogue site using a PIMA instrument. A survey was carried out on the Strelley Pool Chert, an outcrop of stromatolitic, silicified Archean carbonate and clastic succession in the Pilbara Craton, interpreted as being modified by hydrothermal processes. The results of this study demonstrate the capability of SWIR techniques to add significantly to the geological interpretation of such hydrothermally altered outcrops. Minerals identified include dolomite, white micas such as illite-muscovite, and chlorite. In addition, the detection of pyrophyllite in a bleached and altered unit directly beneath the succession suggests acidic, sulfur-rich hydrothermal activity may have interacted with the silicified sediments of the Strelley Pool Chert.     

Eye light flashes on the Mir space station

The phenomenon of light flashes (LF) in eyes for people in space has been investigated onboard Mir. Data on particles hitting the eye have been collected with the SilEye detectors, and correlated with human observations. It is found that a nucleus in the radiation environment of Mir has roughly a 1% probability to cause an LF, whereas the proton probability is almost three orders of magnitude less. As a function of LET, the LF probability increases above 10 keV/micrometer, reaching about 5% at around 50 keV/micrometer.     

French research program on the physiological problems caused by weightlessness. Use of the primate model

The need to acquire a better knowledge of the main biological problems induced by microgravity implies--in addition to human experimentation--the use of animal models, and primates seem to be particularly well adapted to this type of research. The major areas of investigation to be considered are the phospho-calcium metabolism and the metabolism of supporting tissues, the hydroelectrolytic metabolism, the cardiovascular function, awakeness, sleep-awakeness cycles, the physiology of equilibrium and the pathophysiology of space sickness. Considering this program, the Centre d'Etudes et de Recherches de Medecine Aerospatiale, under the sponsorship of the Centre National d'Etudes Spatiales, developed both a program of research on restrained primates for the French-U.S. space cooperation (Spacelab program) and for the French-Soviet space cooperation (Bio-cosmos program), and simulation of the effects of microgravity by head-down bedrest. Its major characteristics are discussed in the study.     

降阶脉冲发动机的点火控制逻辑

本文研究脉冲发动机在战术导弹,特别是空空导弹上的应用.因为其飞行任务要求对能量消耗作仔细地监控.一般的中程空空导弹使用助推-主发动机作为动力.除了接近交会之外,发射时导弹雷达导引头并不知道目标.一般的中程空空导弹使用比例导航或者在终段制导使用改进的比例导航,同时为了使导弹在较高的高度飞行以减小阻力,在中段附加了预编程的     

耐用防热方案的验证试验

为了给未来空间运载系统表面提供耐用的热防护,正在研制三种新型防热系统(TPS):钛合金多层壁、超级合金蜂窝和新的碳-碳多支柱结构。该文介绍这些方案的验证试验(热、振动、噪声、存放环境、雷击、气动热)。初步试验结果表明三种防热方案,可以在2300°F以下表面温度范围内使用。     

HMX复合推进剂燃烧模型计算

本文建立了一个描述 HMX 复合推进剂燃烧特性的模型。该模型基于以下几个重要概念:1.氧化剂和粘合剂具有不同的表面温度;2.能处理由三种不同粒度级配的氧化剂,3.取时间平均方法来计算推进剂燃速,而不取大多数 BDP 类模型所用的空间平均计算燃速的方法,时间平均方法之要点是考虑了氧化剂的点火延迟时间;4.根据修正的 Burke—Sehumann 扩散火