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231.
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Feoktistov K 《Aerospace America》1985,23(5):96-98
A cosmonaut describes the long-duration Salyut-7 flight in 1984. The third visit to the orbital station provided many opportunities to advance knowledge about living and working in space. The stay on Salyut-7 was supported by three manned Soyuz-T visits and five Progress cargo ships. Scientists conducted a number of astrophysical experiments and acquired experience in spacecraft maintenance and repair. Medical research and control on 33 parameters were carried out for 87 of the 237 days. 相似文献
233.
为了表征当前火箭发动机工业中常用的一些壳体复合材料特性,我们做了大量的工作。本文介绍了工作的结果,并且特别注意到了这样一个事实,即这些纤维缠绕材料是在固化炉中固化的,与“飞机”型在热压釜中固化的铺层方法比较,此方法对材料的力学性能会有影响。本文涉及到的所有试样都是从纤维缠绕的样品中取得的。 本研究的目的是评价和鉴定具有当前水平的表征试验方法:测定纤维取向的作用、试验方法和温度对性能的影响;表征复合材料有限元分析中用的所有正交各向异性弹性常数的特性;建立测预和实测性能间的关系;确定今后努力的方向。 我们对四种材料系统进行了表征,它们是:凯夫拉49、涂复有DC-20松粘剂的凯夫拉49、S-2玻璃和341型S-2玻璃布。环氧系统是“刚性”酸酐双酚A环氧,其杨氏模量为2827MPa。凯夫拉试样的准备工作有一些困难,为了获得合适的样品,不得不采用优于高压水喷射或传统机加的激光切割,但在切割涂复有松粘剂的凯夫拉时仍有问题,因为这种材料的层间强度很低。 板片状和环向缠绕环的拉伸试验给出了相当的数据,而且获得了与纤维取向有关的刚性变化和传统叠层理论二者之间极好的相关性。对用各种剪切方法获得的数据进行了比较,它表明与轴线成10°的叠层较之环向缠绕管状试样,其剪切模量高,但剪切 相似文献
234.
Sherwood Lollar B Voglesonger K Lin LH Lacrampe-Couloume G Telling J Abrajano TA Onstott TC Pratt LM 《Astrobiology》2007,7(6):971-986
Dissolved H(2) concentrations up to the mM range and H(2) levels up to 9-58% by volume in the free gas phase are reported for groundwaters at sites in the Precambrian shields of Canada and Finland. Along with previously reported dissolved H(2) concentrations up to 7.4 mM for groundwaters from the Witwatersrand Basin, South Africa, these findings indicate that deep Precambrian Shield fracture waters contain some of the highest levels of dissolved H(2) ever reported and represent a potentially important energy-rich environment for subsurface microbial life. The delta (2)H isotope signatures of H(2) gas from Canada, Finland, and South Africa are consistent with a range of H(2)-producing water-rock reactions, depending on the geologic setting, which include both serpentinization and radiolysis. In Canada and Finland, several of the sites are in Archean greenstone belts characterized by ultramafic rocks that have under-gone serpentinization and may be ancient analogues for serpentinite-hosted gases recently reported at the Lost City Hydrothermal Field and other hydrothermal seafloor deposits. The hydrogeologically isolated nature of these fracture-controlled groundwater systems provides a mechanism whereby the products of water-rock interaction accumulate over geologic timescales, which produces correlations between high H(2) levels, abiogenic hydrocarbon signatures, and the high salinities and highly altered delta (18)O and delta (2)H values of these groundwaters. A conceptual model is presented that demonstrates how periodic opening of fractures and resultant mixing control the distribution and supply of H(2) and support a microbial community of H(2)-utilizing sulfate reducers and methanogens. 相似文献
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236.
Institute for Laser Physics V.A.Serebryakov K.V.Gratzianov A.S.Eremenko A.A.Timopheev SPBSUITMO M.V.Volkov 《航空制造技术》2006,(1):69-72
The first experiments on hardening metals by laserpeening induced residual compressive stress in the sur-face of metals for improving their resistance to cracking,stress corrosion and fatigue took place more than 30years ago. However, only today, with the development ofhigh-intensity pulse repetitive rate lasers, this methodstarts to compete to traditional peening, which use influ-ence of small metal balls.Laser peening uses pulses with high intensity 109 ̄1010 W/cm2 [1]. The laser energy abso… 相似文献
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238.
Flavio S. Correa da Silv Marcelo K. Zuffo Paul W. H. Chung Petros Papapanagiotou David Robertson 《民用飞机设计与研究》2017,(3):105
Hazard prevention in mission plans requires careful analysis and appropriate tools to support the design of preventive and/or corrective measures. It is most challenging in systems with large sets of states and complex state relations. In the case of sociotechnical systems, hazard prevention becomes even more dicult given that the behaviour of human centric components can at best be partially predictable. In the present article we focus on a specic class of sociotechnical systems namely air spaces containing pilot controlled as well as autonomous aircrafts and introduce the notion of relevant hazards. We also introduce soft institutions as an appropriate basis for analysis, with the aim of addressing relevant hazards. The concept of soft institutions is drawn from specication languages for interaction between agents in multi agent systems but, in our case, is adapted for use in systems that combine human and automated actors. 相似文献
239.