电动激振器 第三章 频率范围的扩展

近十多年来,随着科学技术、特别是航空和宇航技术的发展,作为振动环境试验主要技术手段的电动激振系统获得了迅速的发展。由于电子技术的革新,数字技术在振动试验控制、测量和数据处理中的应用,以及电动激振器性能的不断提高,不仅使电动激振系统广泛地应用于各种产品的可靠性检验,而且还应用于产品特性和可靠性的预示,成为产品设计的重要工具之一。因此,研制和生产性能优良的激振系统,并在试验中合理地使用这些系统,对于缩短产品研制周期、降低成本和提高可靠性具有重要的作用。本书着重介绍了电动激振器的工作原理和结构,概述了改进激振器性能的方法。通过对大量专利和现有电动激振系统的分析,提出了激振系统的发展趋势。本书可供科研设计人员、从事振动试验和激振系统研制和生产的人员参考。上角数码为书中原注,带圈的上角数码为译者加的注释,两者皆排于当页或次页之下。由于译者水平所限,译文不确切甚至错误之处,在所难免,恳请读者批评指正。     

电动激振器 第四章 激振器产品的性能

近十多年来,随着科学技术、特别是航空和宇航技术的发展,作为振动环境试验主要技术手段的电动激振系统获得了迅速的发展。由于电子技术的革新,数字技术在振动试验控制、测量和数据处理中的应用,以及电动激振器性能的不断提高,不仅使电动激振系统广泛地应用于各种产品的可靠性检验,而且还应用于产品特性和可靠性的预示,成为产品设计的重要工具之一。因此,研制和生产性能优良的激振系统,并在试验中合理地使用这些系统,对于缩短产品研制周期、降低成本和提高可靠性具有重要的作用。本书着重介绍了电动激振器的工作原理和结构,概述了改进激振器性能的方法。通过对大量专利和现有电动激振系统的分析,提出了激振系统的发展趋势。本书可供科研设计人员、从事振动试验和激振系统研制和生产的人员参考。上角数码为书中原注,带圈的上角数码为译者加的注释,两者皆排于当页或次页之下。由于译者水平所限,译文不确切甚至错误之处,在所难免,恳请读者批评指正。     

史密森天文物理观测台研制的冷氢激射器及有关装置

低温冷却激射器为测量频率偏移和存储壁涂敷材料的弛豫特性创造了有利条件。这种涂敷材料是从常态变为气态物质而被冻结在存储壁上的。我们对FEP—120聚四氟乙烯在77K至48K之间的原始测试结果作了报道,并把这些测量结果和法国de Saintfuscien在372K至77K之间的测试数据进行了比较。对激射器的某些设计性能作了说明。低溫激射器的氢分离器,完全密封在真空环境中,其温度77k。本文还介绍了在真空中工作的分离器和其它一些装置。这些装置已在常温激射器中被采用并进行了测试。它们既适合于太空环境又适合于在地面使用。     

研究组跟踪研究以达到HSCT污染指标

GE和普惠公司对他们的全尺寸型HSCT发动机燃烧室能满足计划中的严格的污染标准充满信心.目前的指标要求HSCT发动机每燃烧1千克燃油产生的NOx不多于5克.这种燃烧室在超音速时其效率应为99.9%,在其他稳态工作状态下效率应为99%.NASA、GE和普惠组成的HSCT推进研究组预计在今年5月将选出一种最佳的燃烧室方案.目前两公司正在研究不同的燃烧技术,每一项技术都将控制污染达到最低水平.GE公司正集中研究贫油预混合/预蒸发(LPP)技术,而普惠公司正在研究富油燃烧/     

外媒评“天宫”——美国：中国试图开辟自己的太空领地

当美国终止自己的航天飞机项目之际。中国正在努力开展空间站工程。20世纪50年代，中国领导人毛泽东主席曾经感慨地说过，     

詹姆斯·韦伯太空望远镜的6个有趣事实

美国研制的詹姆斯·韦伯太空望远镜(巨大的红外线天文观察仪)将于2014年登台亮相,到时它能探测宇宙中出现的第一代恒星。以下便是关于詹姆斯·韦伯太空望远镜的6个有趣事实。"太空轨道折纸"詹姆斯·韦伯太空望远镜(简称JWST)体积巨大无比,它的多层遮     

一种能航空/航天两用的有人/无人机

美国缩比复合材料公司最近推出了一种布局新颖的高空、长航时飞行器,既可用于军事任务,又可用于商用任务;既可有人驾驶又可作无人驾驶飞机使用;既可执行航空任务(如通信中继),又可执行航天任务(例如把小型卫星发射到低地球轨道).这种飞行器取名为“普罗透斯”,其基本布局的翼展为24米,但可以根据任务和有效载荷的需要,把翼梢段加长到翼展为28米.整个机体分为前体、中段圆     

JIRAM, the image spectrometer in the near infrared on board the Juno mission to Jupiter

The Jovian InfraRed Auroral Mapper (JIRAM) has been accepted by NASA for inclusion in the New Frontiers mission "Juno," which will launch in August 2011. JIRAM will explore the dynamics and the chemistry of Jupiter's auroral regions by high-contrast imaging and spectroscopy. It will also analyze jovian hot spots to determine their vertical structure and infer possible mechanisms for their formation. JIRAM will sound the jovian meteorological layer to map moist convection and determine water abundance and other constituents at depths that correspond to several bars pressure. JIRAM is equipped with a single telescope that accommodates both an infrared camera and a spectrometer to facilitate a large observational flexibility in obtaining simultaneous images in the L and M bands with the spectral radiance over the central zone of the images. Moreover, JIRAM will be able to perform spectral imaging of the planet in the 2.0-5.0 microm interval of wavelengths with a spectral resolution better than 10 nm. Instrument design, modes, and observation strategy will be optimized for operations onboard a spinning satellite in polar orbit around Jupiter. The JIRAM heritage comes from Italian-made, visual-infrared imaging spectrometers dedicated to planetary exploration, such as VIMS-V on Cassini, VIRTIS on Rosetta and Venus Express, and VIR-MS on the Dawn mission.     

Testing the H2O2-H2O hypothesis for life on Mars with the TEGA instrument on the Phoenix lander

In the time since the Viking life-detection experiments were conducted on Mars, many missions have enhanced our knowledge about the environmental conditions on the Red Planet. However, the martian surface chemistry and the Viking lander results remain puzzling. Nonbiological explanations that favor a strong inorganic oxidant are currently favored (e.g., Mancinelli, 1989; Plumb et al., 1989; Quinn and Zent, 1999; Klein, 1999; Yen et al., 2000), but problems remain regarding the lifetime, source, and abundance of that oxidant to account for the Viking observations (Zent and McKay, 1994). Alternatively, a hypothesis that favors the biological origin of a strong oxidizer has recently been advanced (Houtkooper and Schulze-Makuch, 2007). Here, we report on laboratory experiments that simulate the experiments to be conducted by the Thermal and Evolved Gas Analyzer (TEGA) instrument of the Phoenix lander, which is to descend on Mars in May 2008. Our experiments provide a baseline for an unbiased test for chemical versus biological responses, which can be applied at the time the Phoenix lander transmits its first results from the martian surface.     

The astrobiology primer: an outline of general knowledge--version 1, 2006

The Astrobiology Primer has been created as a reference tool for those who are interested in the interdisciplinary field of astrobiology. The field incorporates many diverse research endeavors, but it is our hope that this slim volume will present the reader with all he or she needs to know to become involved and to understand, at least at a fundamental level, the state of the art. Each section includes a brief overview of a topic and a short list of readable and important literature for those interested in deeper knowledge. Because of the great diversity of material, each section was written by a different author with a different expertise. Contributors, authors, and editors are listed at the beginning, along with a list of those chapters and sections for which they were responsible. We are deeply indebted to the NASA Astrobiology Institute (NAI), in particular to Estelle Dodson, David Morrison, Ed Goolish, Krisstina Wilmoth, and Rose Grymes for their continued enthusiasm and support. The Primer came about in large part because of NAI support for graduate student research, collaboration, and inclusion as well as direct funding. We have entitled the Primer version 1 in hope that it will be only the first in a series, whose future volumes will be produced every 3-5 years. This way we can insure that the Primer keeps up with the current state of research. We hope that it will be a great resource for anyone trying to stay abreast of an ever-changing field.