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C. Pardini L. Anselmo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The population of cataloged orbital debris increased by approximately 40% in just a couple of years, from January 2007 to February 2009. This was due to two collisions in space, which involved the catastrophic destruction of three intact satellites (Fengyun 1C, Cosmos 2251 and Iridium 33) in high inclination orbits. Both events occurred in the altitude range already most affected by previous launch activity and breakup events, thus boosting the cataloged population in low Earth orbit by more than 60%. 相似文献
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Luciana Bianchi Yongbeom Kang Paul Hodge Julianne Dalcanton Benjamin Williams 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
We discuss the relevance of UV data in the detection and characterization of hot massive stars and young stellar populations in galaxies. We show results from recent extensive surveys in M31 and M33 with Hubble Space Telescope (HST) multi-wavelength data including UV filters, which imaged several regions at a linear resolution (projected) of less than half a pc in these galaxies, and from GALEX far-UV and near-UV wide-field, low-resolution imaging of the entire galaxies. Both datasets allow us to study the hierarchical structure of star formation: the youngest stellar groups are the most compact, and are often arranged within broader, sparser structures. The derived recent star-formation rates are rather similar for the two galaxies, when scaled for the respective areas. We show how uncertainties in metallicity and type of selective extinction for the internal reddening may affect the results, and how an appropriate complement of UV filters could reduce such uncertainties, and significantly alleviate some parameter degeneracies. 相似文献
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基于3J33C弹性合金小孔镗削温度测量实验及Advant Edge有限元温度仿真试验,验证了有限元模型及结果的可靠性,得到其不同镗削参数时基体最高温度的变化规律及温度范围。基于有限元仿真结果建立了3J33C小孔镗削的温度经验公式,结果表明,随着镗削转速、进给速度及径向切深的增大,镗削温度都呈现升高趋势,并且在这三个因素中镗削转速影响最大,进给速度影响次之,径向切深影响最小。 相似文献
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针对航空发动机适航取证的安全性需求,对航空发动机CCAR33-R2.75适航条款进行了解读与分析,明确了该条款的验证要求和方法.将功能危险分析法、故障树分析法和故障模式与影响分析法运用到该验证方法中,并提出了航空发动机CCAR33-R2.75条款适航符合性验证的流程.最后对某型航空发动机进行实例分析,验证了发动机不可控火情对CCAR33-R2.75条款的符合性.该安全性验证方法能够为航空发动机CCAR33-R2.75条款适航符合性验证提供支持. 相似文献
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