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排序方式: 共有1458条查询结果,搜索用时 125 毫秒
1.
Yi Wei Qingjun Li Fangnuan Xu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(1):393-400
A new orbit-attitude-vibration coupled dynamic model of the tethered solar power satellite (Tethered SPS) is established based on absolute nodal coordinate formulation. The Hamilton’s equation of the system is derived by introducing generalized momentum through Legendre transformation. The correctness of the proposed model is verified by an example. The dynamic characteristics of the Tethered SPS are studied using the symplectic Runge-Kutta method. Simulation results show that the orbital radius and the total energy of the system are well preserved. The attitude of the system is unstable when the mass of the bus system is small. However, the attitude stability is dependent on some other parameters of the system, which requires further studies. It is also found that the average tether force/deformation can be roughly estimated by simplifying the solar panel as a particle. The proposed model can be used to study the orbit-attitude-vibration coupled dynamics and control problems. 相似文献
2.
Nurollah Tatar Mohammad Saadatseresht Hossein Arefi Ahmad Hadavand 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(11):2787-2800
Unwanted contrast in high resolution satellite images such as shadow areas directly affects the result of further processing in urban remote sensing images. Detecting and finding the precise position of shadows is critical in different remote sensing processing chains such as change detection, image classification and digital elevation model generation from stereo images. The spectral similarity between shadow areas, water bodies, and some dark asphalt roads makes the development of robust shadow detection algorithms challenging. In addition, most of the existing methods work on pixel-level and neglect the contextual information contained in neighboring pixels. In this paper, a new object-based shadow detection framework is introduced. In the proposed method a pixel-level shadow mask is built by extending established thresholding methods with a new C4 index which enables to solve the ambiguity of shadow and water bodies. Then the pixel-based results are further processed in an object-based majority analysis to detect the final shadow objects. Four different high resolution satellite images are used to validate this new approach. The result shows the superiority of the proposed method over some state-of-the-art shadow detection method with an average of 96% in F-measure. 相似文献
3.
4.
Aprajita Verma Vassilis Charmandaris Ulrich Klaas Dieter Lutz Martin Haas 《Space Science Reviews》2005,119(1-4):355-407
Some of the most ‘active’ galaxies in the Universe are obscured by large quantities of dust and emit a substantial fraction
of their bolometric luminosity in the infrared. Observations of these infrared luminous galaxies with the Infrared Space Observatory
(ISO) have provided a relatively unabsorbed view to the sources fuelling this active emission. The improved sensitivity, spatial
resolution and spectroscopic capability of ISO over its predecessor Infrared Astronomical Satellite (IRAS) of enabled significant
advances in the understanding of the infrared properties of active galaxies. ISO surveyed a wide range of active galaxies
which, in the context of this review, includes those powered by intense bursts of star formation as well as those containing
a dominant active galactic nucleus (AGN). Mid-infrared imaging resolved for the first time the dust enshrouded nuclei in many
nearby galaxies, while a new era in infrared spectroscopy was opened by probing a wealth of atomic, ionic and molecular lines
as well as broad band features in the mid- and far-infrared. This was particularly useful, since it resulted in the understanding
of the power production, excitation and fuelling mechanisms in the nuclei of active galaxies including the intriguing but
so far elusive ultraluminous infrared galaxies. Detailed studies of various classes of AGN and quasars greatly improved our
understanding of the unification scenario. Far-infrared imaging and photometry revealed the presence of a new very cold dust
component in galaxies and furthered our knowledge of the far-infrared properties of faint starbursts, ULIGs and quasars. We
summarise almost nine years of key results based on ISO data spanning the full range of luminosity and type of active galaxies. 相似文献
5.
介绍一种高压快开阀装置。它可产生370MPa上升时间小于20μs的阶跃压力,用于对高压传感器进行动态校准。 相似文献
6.
运用理论分析方法和实测试验方法,探讨了梁在塑性动态断裂过程中,其塑性铰转动因子的变化规律,提出了断裂过程中塑性铰几何转动因子的概念及其确定方法,并以3点弯曲梁理论分析解为例,计算了梁在塑性动态断裂过程中,其塑性铰转动因子的变化规律。该计算结果与3点弯曲梁动态断理解实验实测相一致。理论分析进一步明确了梁的塑性铰转动因子具有几何与物理两种不同的本质含意,并可直接用于修正梁的塑性动态断裂的理论分析解。 相似文献
7.
应用奇异摄动法分析横侧小扰动运动的动稳定性问题,将四阶问题分解为小根、大根和复根模态,它对应于经典理论中的螺旋、滚转和荷兰滚模态,并给出了动态反应过程的解。 相似文献
8.
本文介绍用 Visual FoxPro的定时器。标签、按钮等控件和控件的属性、方法、事件等在界面上设计动态字幕、动态按钮等若干动态效果的方法。 相似文献
9.
弹道靶红外辐射测量 总被引:1,自引:0,他引:1
为深入认识再入物理现象 ,在弹道靶上做了模型头部和近尾流红外辐射测量。发射器为 1 4.5mm口径的二级轻气炮 ,模型为1 0mm的球 ,材料为聚碳酸酯和铝 ,模型发射速度 4~6km/s,使用红外InSb探测器测量波长 3~ 5 .4μm的红外辐射 ,靶室压力 5 .32kPa。实验中使用光电法测量模型速度 ,两站阴影照相进行模型姿态监测和速度核实。实验结果表明 :球模型的红外辐射强度强烈依赖于模型材料和模型飞行速度。对不同材料模型头部和尾流部辐射强度的定性比较说明由于低温材料烧蚀产物的存在 ,极大地增强了头部和近尾流区的辐射强度 ,而且延长了尾流辐射长度 相似文献
10.