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241.
通过几种特性物质在钢铁电极表面吸脱附电位和微分电容曲线及含有这些特性物质的镀铅电解液阴极化曲线的测试,发现电沉积时铜的初始析出电位值,在特性物质吸脱附电位区间和金属基本表现酸蚀活化后的活性保护,是取得具有牢固结合力镀层的必要条件。 相似文献
242.
热防护技术是决定高超声速飞行器设计成败的关键要素。高超声速飞行器不同部位将承受不同的力、热载荷,需选择不同的热防护方案。以HTV-2、X-37B和NASA的亚轨道运输飞行器为例,系统介绍三类典型高超声速飞行器采用的热防护方案,并揭示了热防护技术的最新进展。未来,材料工艺技术的发展和创新型热防护方案的研发,将进一步提升热防护系统的技术成熟度和适用范围,为各类高超声速飞行器的设计研制提供重要的能力保障。 相似文献
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246.
陈功 《民用飞机设计与研究》2016,(1):53
通过对某型民用飞机起落滑跑情况下的受力分析,获得了各起落架所受的载荷。结合相关标准文件及该飞机起落架轮毂轴承本身参数,计算出了各轴承的额定动载荷及当量动载荷。而后通过滚动轴承寿命计算及修正公式计算出了各轴承的使用寿命。研究发现,该系列轴承的使用寿命完全满足某型飞机对于起落架系统的性能要求。 相似文献
247.
George Profitiliotis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(12):4158-4176
The emergence of private space actors may soon enable the growth of the novel market segments of space research and exploration, space resources utilization, and human access to space. The interdisciplinary field of Planetary Protection has to keep up with these advances. Planetary Protection is defined as a set of guidelines that aim to prevent the forward contamination of celestial bodies with biological material from Earth and the backward contamination of the terrestrial biosphere with extraterrestrial biological material. As space entrepreneurs acquire and develop the resources and competencies for commercial access to space, significant questions are expected to be raised in the future with respect to potential forward and backward contamination issues, particularly with respect to activities between Earth and Mars. Although such private activities do not seem to pose a serious Planetary Protection threat at the moment, certain preparatory steps need to be taken in order to prudently inform the relevant policy-making procedures. This work describes the application of the Contingent Valuation Method, a useful tool of the environmental economics discipline, with the aim of demonstrating a novel approach to estimate the economic valuation of the external benefits of preventing forward and backward contamination between Earth and Mars. Particularly, via a survey specifically developed for this purpose, a set of questions are used to elicit the perceived economic value that respondents place on the prevention of forward and backward contamination; the survey is administered to a national probability sample in Greece, and the generated data is processed through statistical analysis. The Contingent Valuation Method is a popular and well-established stated preference valuation technique; these techniques are often the more suitable choice for ex-ante valuations of future changes, and are currently the only known approach to capture all the aspects of the economic value of non-market goods. Through an initial proof-of-concept in Greece, the goal of this work is to provide useful insights on the expected external benefits of a national Planetary Protection policy to regulate future private space activities between Earth and Mars, and to encourage a larger-scale application of this tool in other countries around the world. 相似文献
248.
酚醛树脂作为一种烧蚀材料,凭借其耐高温的特性应用于航天器防热系统,其防热性能在工程实际中需进行考核。以某航天器一段包覆80纤维布/酚醛树脂的液路管路作为研究对象,以定热流为边界条件,采用仿真计算和热流试验的研究方法对空导管以及注水导管的温度场进行研究:仿真计算得出导管表面平衡温度分布以及导管表面具有代表性某点瞬态温度变化;为验证仿真计算的准确性,进行了热流试验,得出了导管表面以及水中温度测点的瞬态温度变化;根据热流试验的温度结果,分析比对了热流试验对仿真计算的验证情况。研究结果表明:80纤维布/酚醛树脂的防热性能符合温度指标要求;仿真结果和热流试验结果一致度良好,证明了仿真计算的合理性和准确性。 相似文献
249.
航班延误产生的矛盾会导致乘客采取过激的方式维权,这对民航运输安全造成了很大的影响。本文分析了航班延误后旅客采取的过激维权行为的原因,并从不同角度提出了预防措施,希望能对避免航班延误后乘客和航空公司发生矛盾以及采取过激维权行为有所裨益。 相似文献
250.
W. Schubert G. PlettA. Yavrouian J. Barengoltz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
For the purposes of planetary protection, a series of experiments were performed to answer a long-standing question about the potential of bacterial contamination of interplanetary spacecraft from liquid hydrazine. Spores of Bacillus atrophaeus (ATCC No. 9372, also known as Bacillus subtilis var. niger, and BSN) were exposed to hydrazine and survivors were enumerated using the NASA standard planetary protection pour plate assay. Results indicate that bulk hydrazine rocket propellant may be considered free of living bacterial cells for planetary protection compliance. 相似文献