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501.
概率风险评价(PRA)方法是一项成熟的量化风险评估技术,而可靠性相关数据不足,制约着该方法在国内载人航天领域的应用。针对这一问题,结合NASA的PRA工作经验,提出了一种适合国内载人航天PRA数据选用与分析的方法,综合运用产品的通用数据与特定数据,采用贝叶斯等数据融合方法,对产品进行量化评价。通过航天典型产品案例,与经典评估方法进行对比分析,结果表明,此方法更能反映产品的失效特性。文章提出的方法,可用于载人航天等具有小子样特征的产品PRA数据的选用与分析,为我国载人航天开展PRA工作提供参考。 相似文献
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503.
Human beings are now facing global and regional sustainable development challenges.In China, Earth observation data play a fundamental role in Earth system science research. The support given by Earth observation data is required by many studies, including those on Earth's limited natural resources, the rapid development of economic and social needs, global change, extreme events, food security, water resources, sustainable economic and urban development, and emergency response. Application operation systems in many ministries and departments in China have entered a stage of sustainable development, and the State Key Project of High-Resolution Earth Observation Systems has been progressing since 2006. Earth observation technology in China has entered a period of rapid development. 相似文献
504.
Luciana Bianchi Alberto Conti Bernie Shiao 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The Galaxy Evolution Explorer (GALEX) has performed the first surveys of the sky in the ultraviolet (UV). Its legacy is an unprecedented database with more than 200 million source measurements in far-UV (FUV) and near-UV (NUV), as well as wide-field imaging of extended objects, filling an important gap in our view of the sky across the electromagnetic spectrum. The UV surveys offer unique sensitivity for identifying and studying selected classes of astrophysical objects, both stellar and extra-galactic. We examine the overall content and distribution of UV sources over the sky, and with magnitude and color. For this purpose, we have constructed final catalogs of UV sources with homogeneous quality, eliminating duplicate measurements of the same source. Such catalogs can facilitate a variety of investigations on UV-selected samples, as well as planning of observations with future missions. We describe the criteria used to build the catalogs, their coverage and completeness. We included observations in which both the far-UV and near-UV detectors were exposed; 28,707 fields from the All-Sky Imaging survey (AIS) cover a unique area of 22,080 square degrees (after we restrict the catalogues to the central 1° diameter of the field), with a typical depth of ∼20/21mag (FUV/NUV, in the AB mag system), and 3008 fields from the Medium-depth Imaging Survey (MIS) cover a total of 2251 square degrees at a depth of ∼22.7mag. The catalogs contain ∼71 and ∼16.6 million sources, respectively. The density of hot stars reflects the Galactic structure, and the number counts of both Galactic and extra-galactic sources are modulated by the Milky Way dust extinction, to which the UV data are very sensitive. 相似文献
505.
Milan S. Dimitrijević Magdalena Christova Zoran Simić Andjelka Kovačević Sylvie Sahal-Bréchot 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Stark broadening parameters for 36 multiplets of B IV have been calculated using the semi-classical perturbation formalism. Obtained results have been used to investigate the regularities within spectral series and temperature dependence. 相似文献
506.
Rafik Hamdi Nabil Ben Nessib Sylvie Sahal-Bréchot Milan S. Dimitrijević 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Using semiclassical perturbation approach in impact approximation, we have calculated Stark widths for 32 spectral lines of doubly charged argon (Ar III). Oscillator strengths are calculated using Hartree–Fock method with relativistic correction (HFR) and an atomic model including 17 configurations. Energy levels are taken from NIST database. For perturbing levels for which the corresponding energy does not exist in NIST database, the calculated energies are used. Our widths are compared with the experimental results. The results presented here are of interest for modelling and investigation of stellar atmospheres since argon in different ionization stages is observed in many astrophysical objects. Finally, the importance of Stark broadening mechanism is studied in the atmospheric conditions of sdB stars. Electron impact Stark widths are compared to thermal Doppler widths as a function of temperature and optical depth of atmospheric layers. 相似文献
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508.
以Oracle数据库为源头在微软SQL Server Analysis Services平台上通过建立数据挖掘模型并在航空电子企业中得到实践与应用。 相似文献
509.
《中国航空学报》2020,33(8):2242-2256
In cabin-type component alignment, digital measurement technology is usually adopted to provide guidance for assembly. Depending on the system of measurement, the alignment process can be divided into measurement-assisted assembly (MAA) and force-driven assembly. In MAA, relative pose between components is directly measured to guide assembly, while in force-driven assembly, only contact state can be recognized according to measured six-dimensional force and torque (6D F/T) and the process is completed based on preset assembly strategy. Aiming to improve the efficiency of force-driven cabin-type component alignment, this paper proposed a heuristic alignment method based on multi-source data fusion. In this method, measured 6D F/T, pose data and geometric information of components are fused to calculate the relative pose between components and guide the movement of pose adjustment platform. Among these data types, pose data and measured 6D F/T are combined as data set. To collect the data sets needed for data fusion, dynamic gravity compensation method and hybrid motion control method are designed. Then the relative pose calculation method is elaborated, which transforms collected data sets into discrete geometric elements and calculates the relative poses based on the geometric information of components. Finally, experiments are conducted in simulation environment and the results show that the proposed alignment method is feasible and effective. 相似文献
510.
立方星编队或星座构成分布式空间传感器网络,可提高立方星执行复杂空间任务的能力。然而立方星易发生故障,其故障时间不确定性也导致了传感器网络性能的不稳定,这凸显了对立方星网络进行在轨维护的重要性。考虑立方星传感器网络的功能维持问题,描述了一种网络维护架构,通过定期发射、在轨备份立方星以及时更换故障立方星,从而提高网络对单星随机失效事件的快速响应与恢复能力。建立了该架构的运行成本模型,包括固定成本、储存成本和短缺成本。收集整理了真实的立方星寿命数据,并使用最大化拟合优度参数估计方法得到最优立方星寿命的随机模型。采用基于蒙特卡罗仿真的遗传算法优化备用立方星的补给时刻和补给数量,在备份成本与系统性能下降所带来的损失之间进行权衡,使得系统的综合收益最优。 相似文献