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81.
反射面型天线结构多工况离散变量优化设计 总被引:4,自引:0,他引:4
根据反射面型天线结构受载和工作状态的复杂性,以及总有一些变量只能按离散变量处理,建立了符合工程结构的反射面型天线结构多工况离散变量优化设计数学模型,编制了一套具有一定通用性及工程实用价值的优化设计软件,并用其对八米反射面型天线进行了优化计算,取得了比较满意的效果。 相似文献
82.
航天电子设备可靠性评估方法研究 总被引:1,自引:0,他引:1
建立了一种综合利用航天电子设备分系统可靠性信息和试验数据以及整机系统试验数据的Bayes可靠性评估方法.该方法利用最大熵方法融合分系统可靠性信息,推导了从分系统可靠性矩到系统可靠性矩的计算公式,然后建立了基于继承因子ρ的混合β先验分布,结合整机系统试验数据确定后验分布,最后,基于后验分布推断航天电子设备可靠性.采用该方法对航天电子设备可靠性进行了评估,当整机系统试验数据为240次时,航天电子设备在置信水平0.70的情况下可靠度可达到0.9991,所要求的整机系统试验次数比经典方法约降低了4/5. 相似文献
83.
84.
The present work aims to investigate the fatigue behavior of Direct Laser Deposition (DLD) Ti-6.5Al-2Zr-1Mo-1V titanium alloy under constant amplitude stress. 22 pieces of DLD Ti-6.5Al-2Zr-1Mo-1V titanium alloy standard cylinder specimens were tested under a stress level of 800?MPa with a stress ratio of 0.06. Fatigue fractography and fatigue life data were obtained. Through the fracture surface analysis, the specimens were divided into two categories in accordance with the location of crack initiation and defect types. Comparison of fatigue life and behavior between two specimen types was given, which was followed by a discussion about the impact of defect type, size and position on the fatigue life of the specimen. The fatigue test results also show a large variation of fatigue life. To illustrate the statistical characteristics of the fatigue life, probabilistic analysis was performed, and a novel bimodal lognormal model was established. The model has a good fit with the experimental data and can reduce the scatter of the fatigue life significantly. 相似文献
85.
In this study, in-plane mixed mode-I/II fatigue crack growth simulations and experiments are performed for the Al 7075-T651 aluminum alloy which is widely used in the aerospace industry. Tests are carried out under different mode mixity ratios to evaluate the applicability of a fracture criterion developed in a previous study to mixed mode-I/II fatigue crack growth tests. Results obtained from the analyses and experiments are compared with existing and developed criteria in terms of crack growth lives. Compact Tension Shear (CTS) specimens, which enable mixed mode loading with loading devices under different loading angles, are used in the simulations and experiments. In an effort to model and simulate the actual conditions in the experiments, crack surfaces of fractured specimens are scanned, crack paths are modeled exactly, and contacts are defined between the contact surfaces of a specimen and the loading device for each crack propagation step in the analyses. Having computed the mixed mode stress intensity factors from the numerical analyses, propagation life cycles are predicted by existing and the developed mixed mode-I/II criteria and then compared with experimental results. 相似文献
86.
Songhui Han Qingming Gui Jianwen Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
In this paper, the establishment criteria, routing algorithm and the probability of use of ISLs (inter-satellite links) in the mixed navigation constellation of GEO satellites, IGSO satellites and MEO satellites are analyzed. Firstly, the general criteria of ISL establishment in mixed navigation constellation are proposed from the perspective of geometry, and the influences of these criteria on routing algorithms and the probability of use of ISLs are discussed. Then, from the perspective of autonomous orbit determination, the routing algorithm in mixed navigation constellation is designed. Thirdly, a stochastic study of ISLs load in mixed navigation constellation is proposed, and the formulae of probability of use of ISLs are given. Finally, in the simulation, the establishment criteria, routing algorithm and the probability of use of ISLs in a specific mixed navigation constellation of 3GEO + 3IGSO + 24MEO are discussed in detail. The findings of this paper provide a basis for the ISL establishment and routing algorithm, and offer the quantitative indicators for the use of ISL in the mixed navigation constellation. 相似文献
87.
Traditional multiframe Track-Before-Detect(TBD) may incur adverse integration loss resulting from model mismatch in sensor coordinates. Its suboptimal integration strategy may cause target envelope degradation. To address these issues, a pseudo-spectrum-based multiframe TBD in mixed coordinates is proposed firstly. The data search for energy integration is conducted based on an accurate model in the x-y plane while target energy is integrated based on pseudo-spectrum in sensor coordinates. The a... 相似文献
88.
In this study,firstly,for the axisymmetric RVABI,the change-rule of adverse pressure gradient caused by radial velocity during the transition of internal flow mode in variable geometry is summarized,and a Bypass Ratio(BR) iterative algorithm based on the empirical correlation of non-equilibrium pressure is proposed.The algorithm can estimate the nonlinear relationship between area ratio and BR,with an error range falling below 6.5%.Then,we discuss the favorable effect of uniform mixing on the th... 相似文献