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排序方式: 共有1934条查询结果,搜索用时 62 毫秒
861.
862.
Xiuqiang Jiang Shuang Li Xiangyu Huang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(5):1342-1358
Supposing future orbiting and landing collaborative exploration mission as the potential project background, this paper addresses the issue of Mars entry integrated navigation using radio beacon, flush air data sensing system (FADS), and inertial measurement unit (IMU). The range and Doppler information sensed from an orbiting radio beacon, the dynamic pressure and heating data sensed from flush air data sensing system, and acceleration and attitude angular rate outputs from an inertial measurement unit are integrated in an unscented Kalman filter to perform state estimation and suppress the system and measurement noise. Computer simulations show that the proposed integrated navigation scheme can enhance the navigation accuracy, which enables precise entry guidance for the given Mars orbiting and landing collaborative exploration mission. 相似文献
863.
Linfeng Huang Jinsong Wang Yong Jiang Zhou Chen Kai Zhao 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Ionospheric scintillation variations are studied using GPS measurements at the low latitude station of Shenzhen (22.59°N, 113.97°E), situated under the northern crest of the equatorial anomaly region, from the Chinese Meridian Project. The results are presented for data collected during the current phase of rising solar activity (low to high solar activity) from December 2010 to April 2014. The results show that GPS scintillation events were largely a nighttime phenomenon during the whole observation period. Scintillation events mainly occurred along the inner edge of the northern crest of the equatorial anomaly in China. The occurrence of scintillations in different sectors of the sky was also investigated, and the results revealed that it is more likely for the scintillations to be observed in the west sector of the sky above Shenzhen. During the present period of study, a total number of 512 total electron content (TEC) depletions and 460 lock loss events were observed. In addition, both of these events are likely to increase during periods of high solar activity, especially because the strong scintillations are often simultaneously accompanied by TEC depletions and lock losses by GPS receivers. 相似文献
864.
Hong Li Xiangyun Long Hua Feng Qiong Wu Jiahui Huang Weichun Jiang Massimo Minuti Dongxin Yang Saverio Citraro Hikmat Nasimi Jiandong Yu Ge Jin Ming Zeng Peng An Luca Baldini Ronaldo Bellazzini Alessandro Brez Luca Latronico Enrico Costa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(1):708-714
PolarLight is a compact soft X-ray polarimeter onboard a CubeSat, which was launched into a low-Earth orbit on October 29, 2018. In March 2019, PolarLight started full operation, and since then, regular observations with the Crab nebula, Sco X-1, and background regions have been conducted. Here we report the operation, calibration, and performance of PolarLight in the orbit. Based on these, we discuss how one can run a low-cost, shared CubeSat for space astronomy, and how CubeSats can play a role in modern space astronomy for technical demonstration, science observations, and student training. 相似文献
865.
Zhong Lingwei Liu Yu Li Juan Gu Zuo Jiang Haocheng Wang Haixing Tang Haibin 《中国航空学报》2010,23(1):15-21
Charge exchange(CEX) ions could inflict severe damages on the ion thruster optical system. This article is aimed at investigating the characteristics of the CEX ions and their influences upon the optical system by means of particle-in- cell(PIC) ion simulation and Monte Carlo collision(MCC) methods. The results from numerical simulation indicate that despite the fact that CEX ions appear in the entire beamlet region near the ion optical system, the ones that present themselves downstream of the accelerator grid have good reason for attracting more attention. As their trajectories are significantly affected by the local electric field, a great number of CEX ions are accelerated toward grids resulting in sputtering erosion. When the influences of the CEX ions are considered in the numerical simulation, there could hardly be observed augments in the screen grid current, but the accelerator grid current increases from zero to 1. 4% of the beamlet current. It can be understood from the numerical simulation that the CEX ions formed in the region far downstream of the accelerator grid should be blamed for the erosion on the downstream surface of the accelerator grid. 相似文献
866.
面向自动化装配的大型客机结构工艺性设计初探 总被引:1,自引:1,他引:0
在大型客机研制中必须尽早确定自动化装配的应用范围、对象,需要设计部门、工艺部门和设备供应商联合工作,选定合适的自动化装配设备型式,设计出适应面向自动化装配的机体结构部件;工艺工装部门,规划部门应联合设备供应商一起尽早开展自动化生产线规划,形成完整的自动化装配生产线布置,建设装配厂房时应适应自动化装配的需要,避免日后返工或改造. 相似文献
867.
Hong-xia Zheng Wei-ming Tian Hong-ji Yan Hua-dong Jiang Shan-shan Liu Lei Yue Fang Han Li-jun Wei Xiong-biao Chen Yu Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
This study investigated intracellular oxidative stress and its underlying mechanisms in a rotary cell culture system used to achieve a simulated microgravity (SMG) environment. Experiments were conducted with human breast cancer cell lines MCF-7 (an estrogen receptor (ER) α positive cell line) and MDA-MB-231 (an ERα negative cell line) encapsulated in alginate/collagen carriers. After 48 h, SMG led to oxidative stress and DNA damage in the MDA-MB-231 cells but a significant increase in mitochondrial activity and minimal DNA damage in the MCF-7 cells. The activity of superoxide dismutase (SOD) significantly increased in the MCF-7 cells and decreased in MDA-MB-231 cells in the SMG environment compared with a standard gravity control. Moreover, SMG promoted expression of ERα and protein kinase C (PKC) epsilon in MCF-7 cells treated with PKC inhibitor Gö6983. Overall, exposure to SMG increased mitochondrial activity in ERα positive cells but induced cellular oxidative damage in ERα negative cells. Thus, ERα may play an important role in protecting cells from oxidative stress damage under simulated microgravity. 相似文献
868.
高层建筑火灾中,烟气是影响人员疏散及造成人员伤亡的主要原因.文中从理论上分析与比较了目前世界各国在高层建筑中所采用的防排烟模式与防烟空气幕的优缺点,从理论上解释了防烟空气幕的合理性与可行性.根据防烟空气幕的理论计算确定空气幕流量、吹风口宽度和风口射流速度并进行实验.实验结果表明,当空气幕流量与烟气流量之比为0.6左右,空气幂射流厚度在25-45 mm且射流角度在25°-35°之间时,空气幕对烟气能起到很好的阻隔作用.由于空气幕的卷吸作用,防烟效果只能达到98%.实验结果验证了本文理论计算的正确性. 相似文献
869.
870.
对空战攻防对策力学准则进行了推广研究。导出考虑导弹杀伤半径不为零时的“圆捕获”的界栅方程,该方程表明“点捕获”界栅方程是“圆捕获”界栅方程的特例,给出了捕获区,逃逸区和界栅几何图形,该图形描述了界栅与视线距,视线变化率,视线角速度之间的关系;分析了导弹杀伤半径,导弹和目标机动能力的差值对导弹和目标空战效果的影响。 相似文献