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31.
根据风切变对飞机飞行影响的机理,以及FAA对CATⅠ类着陆最坏条件下的边界要求,推导了风切变的危险程度判据。通过计算,分析了垂直风切变与水平风切变对飞行性能的影响的异同,并通过对危险判据与性能恶化参数的相关性研究,提出了适用于机载风切变探测告警系统的告警准则。 相似文献
32.
Rui Zhang Rui Tu Pengfei Zhang Lihong Fan Junqiang Han Xiaochun Lu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(12):4011-4024
The BeiDou global navigation satellite system (BDS-3) has established the Ka-band inter-satellite link (ISL) to realize a two-way ranging function between satellites, which provides a new observation technology for the orbit determination of BDS-3 satellites. Therefore, this study presents a BDS satellite orbit determination model based on ground tracking station (GTS) observations and ISL ranging observations firstly to analyze the impact of the ISL ranging observations on the orbit determination of BDS-3 satellites. Subsequently, considering the data fusion processing, the variance component estimation (VCE) algorithm is applied to the parameter estimation process of the satellite orbit determination. Finally, using the measured data from China’s regional GTS observations and BDS-3 ISL ranging observations, the effects of ISL ranging observations on the orbit determination accuracy of BDS-3 satellites are analyzed. Moreover, the impact of the VCE algorithm on the fusion data processing is evaluated from the aspects of orbit determination accuracy, Ka-band hardware delay parameter stability, and ISL ranging observation residuals. The results show that for China’s regional GTSs, the addition of BDS-3 ISL ranging observations can significantly improve the orbit determination accuracy of BDS-3 satellites. The observed orbit determination accuracy of satellite radial component is improved from 48 cm to 4.1 cm. In addition, when the initial weight ratio between GTS observations and ISL ranging observations is not appropriate, the various indicators which include orbit determination accuracy, ISL hardware delay, and ISL observation residuals were observed to have improved after the adjustment of the VCE algorithm. These results validate the effectiveness of the VCE algorithm for the fusion data processing of the GTS observations and ISL ranging observations. 相似文献
33.
Vladimir N. Gubenko A.G. Pavelyev I.A. Kirillovich Y.-A. Liou 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(7):1702-1716
We have used the radio occultation (RO) satellite data CHAMP/GPS (Challenging Minisatellite Payload/Global Positioning System) for studying the ionosphere of the Earth. A method for deriving the parameters of ionospheric structures is based upon an analysis of the RO signal variations in the phase path and intensity. This method allows one to estimate the spatial displacement of a plasma layer with respect to the ray perigee, and to determine the layer inclination and height correction values. In this paper, we focus on the case study of inclined sporadic E (Es) layers in the high-latitude ionosphere based on available CHAMP RO data. Assuming that the internal gravity waves (IGWs) with the phase-fronts parallel to the ionization layer surfaces are responsible for the tilt angles of sporadic plasma layers, we have developed a new technique for determining the parameters of IGWs linked with the inclined Es structures. A small-scale internal wave may be modulating initially horizontal Es layer in height and causing a direction of the plasma density gradient to be rotated and aligned with that of the wave propagation vector k. The results of determination of the intrinsic wave frequency and period, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase speeds, and other characteristics of IGWs under study are presented and discussed. 相似文献
34.
《中国航空学报》2020,33(10):2602-2609
The aim of this paper is to model the yielding asymmetry of pressure-insensitive metals, including but not limited to Ni3Al alloys. The main focuses are put on the flexibility and manipulative convenience. The parameters of theory are kept to a minimum and can be determined by as few tests as possible. These requirements are fulfilled by constructing a yield function using the second and third-invariants of a linearly transformed stress tensor. The proposed yield criterion has a simple mathematical form and has only seven parameters when used in three-dimensional stresses. Compared with existing theories, the new yield criterion has much fewer parameters, which makes it very convenient for practical applications. The coefficients of the criterion are identified by an error minimization procedure. Applications to a Ni3Al based intermetallic alloy as well as a Cu-Al-Be shape memory alloy and comparison to other criteria show that the proposed criterion has nearly the same predictive ability and flexibility with other criteria. The proposed yield criterion can estimate the coefficients by using less data, which is a big advantage compared with other similar theories, especially when there is a limited number of experimental data. 相似文献
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36.
针对太阳系远深距离的探测将是人类下一阶段深空探测活动的主要目标。这一目标的实现依赖于探测器连续推进动力技术的突破。从描述连续常值推力下太空飞行的施图林格解出发,对其中反映的深远空飞行任务有效载荷比、任务时间、飞行距离等关键参数与发动机性能之间的关系进行了深入分析。给出了在特定任务时长、特定飞行距离要求下发动机比冲、功率需要满足的条件及其对有效载荷比、最终飞行速度等指标的影响。此外,基于二体轨道动力学对太阳系行星探测的大椭圆转移轨道和转移能量进行了推导,并对连续推力的太阳帆任务方案涉及的关键技术指标做了理论性的计算。这些结论是对深空探测连续推力方案基础理论的归纳,可以为我国未来开展深远空探测活动提供重要的启发和指导。 相似文献
37.
郭秀英 《燃气涡轮试验与研究》2005,18(3):52-55
本文较为详细地介绍了中国燃气涡轮研究院“三大规范”编制与实施过程中的目标的确定、总体规划、采取的措施、应用效果、存在的问题及解决方法,可为同行编制“三大规范”提供借鉴和参考。 相似文献
38.
Nellore S. Venkataraman Ana M. Vélez García Vikram Venkataraman Heberth Diestra-Cruz 《Acta Astronautica》2014
Thermal control of spacecrafts plays an important role in space missions. In the design stage the preliminary thermal analysis of the spacecraft requires an estimate of the conductive thermal resistance between the various spacecraft components. With this in mind, the fully three dimensional problem of determining the thermal field in a conducting sphere with an asymmetric split ring current carrying heating source is resolved in an analytical or almost analytical form, implying either a closed form solution or utmost expressions involving a simple numerical integration. This has immediate application for evaluation of thermal resistance in spacecrafts. Green's function integral techniques are used. Comparisons are made with series solutions and also with purely numerical solutions to contrast the simplicity and highlight the elegance of the present method. Parametric studies reveal expected behavior. 相似文献
39.
杨俊 《中国民航飞行学院学报》2013,(1):12-15
大气紊流和风切变对飞行活动影响较大,尤以低空风切变危害最大,严重威胁着民航飞行的安全。鉴于飞行器对抗大气扰动的实际能力有限,正确的飞行对策是回避或改出危险的大气扰动区。本文对某训练飞机着陆进近遭遇风切变时飞机轨迹的变化进行了模拟仿真计算。结果表明,采用恒定迎角策略,即采用最大允许迎角(抖动迎角)和最大油门时,改出效果最佳。同时计算出了某训练飞机在水平风为0时,所能抵抗的最大垂直阵风强度;以及在垂直阵风为0时,所能抵抗的最大水平风强度。 相似文献
40.