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191.
192.
Durk Jong Park Kyung Whan Yeom Sang Il Ahn Hyo Suk Lim 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
This paper describes the development and validation of a transportable active transponder designed for the image calibration of Korea Multi-Purpose Satellite-5 (KOMPSAT-5) with a synthetic aperture radar (SAR). Ground targets are essential in SAR image calibration. The environment for the deployment of ground targets for SAR image calibration should provide uniformity and minimum interference. The Amazon or deserts are regarded as desirable environments. However, such environments for SAR image calibration are difficult to find in Korea. Thus, it will be advantageous to have an active transponder whose performance will not be severely limited by the absence of such uniform environment. We have therefore developed an active transponder which has an adjustable internal delay and into which the orbit data of an arbitrary satellite can be loaded. The stored obit data with the aid of an internal global positioning system (GPS) receiver and gyroscope enables the active transponder to point to a selected satellite. In addition, a virtual deployment of the active transponder is possible due to its adjustable internal delay. Thus, the developed active transponder can be deployed at any place without environmental constraint. The performance of the developed active transponder is validated using the satellite TerraSAR-X, which is already in operation. The test results show that the active transponder is successfully compliant with the requirements for KOMPSAT-5 image calibration. 相似文献
193.
Hsien Shang Frank H. Shu Typhoon Lee Alfred E. Glassgold 《Space Science Reviews》2000,92(1-2):153-176
We discuss the interaction between the magnetosphere of a young star and its surrounding accretion disk. We consider how an
X-wind can be driven magnetocentrifugally from the inner edge of the disk where accreting gas is diverted onto stellar field
lines either to flow onto the Sun or to be flung outwards with the wind. The X-wind satisfies many observational tests concerning
optical jets, Herbig-Haro objects, and molecular outflows. Connections may exist between primitive solar system materials
and X-winds. Chondrules and calcium-aluminum-rich inclusions (CAIs) experienced short melting events uncharacteristic of the
asteroid belt where meteorites originate. The inner edge of the solar nebula has the shortest orbital timescale available
to the system, a few days. Protosolar flares introduce another timescale, tens of minutes to hours. CAIs may form when solids
are lifted from shaded portions of the disk close to the Sun and are exposed to its intense light for a day or so before they
are flung by the X-wind to much larger distances. Chondrules were melted, perhaps many times, by flares at larger distances
from the Sun before being launched and annealed, but not remelted, in the X-wind. Aerodynamic sorting explains the narrow
range of sizes with which CAIs and chondrules are found in chondritic meteorites. Flare-generated cosmic-rays may induce spallation
reactions that produce some of the short-lived radioactivities associated with primitive solar system rocks.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
194.
195.
In the work presented here, we address parameter optimization for agile beam radar tracking to minimize the radar resources that are required to maintain a target under track. The parameters to be optimized include the track-revisit interval as well as the sequence of pairs of target signal strengths and detection thresholds associated with successive illumination attempts in each track-revisit. The effects of false alarms and clutter interference are taken into account in the modeling of target detection and in the characterization of tracking performance. Based on the detection model and tracker characterization, the parameter optimization problem is formulated. Typical examples of the optimization problem are numerically solved. The optimal solution gives an off-line scheduling of the parameter set. It also provides insight into the selection of a near-optimal parameter set that is appropriate for real-time implementation. 相似文献
196.
燃油测量系统是燃油系统的重要子系统之一,其精度、可靠性和维护性对飞机整体性能都有很大的影响。实时、精确地测量油箱内的剩余油量对于保证飞机安全飞行,实现重心控制、燃油管理、耗油顺序优化等功能有重要意义。同时,对于民用飞机而言,燃油测量系统精度的提高将直接影响飞机的经济性。从常见的燃油测量系统误差入手,分析了各个因素对测量... 相似文献
197.
安姝 《华北航天工业学院学报》2007,(1)
加强思想政治教育的人文关怀是以人的发展为本,符合人的本性。不仅是思想政治教育自身发展的内在要求,也是和谐社会发展的需要。思想政治教育要转变教育方式,注重学生个性化教育,提高整个教育的效果。 相似文献
198.
舒忠正 《南京航空航天大学学报》1993,25(3):299-303
本文介绍了医学专家系统开发工具BFBEST的知识库生成系统设计技术。包括:(1)灵活友好的用户接口,(2)帮助用户避免输入知识时的语法和语义错误;(3)允许用户用领域规范化形式的知识与系统对话,输入知识;(4)具有事务薄记功能;(5)具有对知识库进行增、删、改的能力;(6)能对输入知识进行完整性和一致性的检查;(7)能将知识的机内表示复原成规范化的形式;(8)具有传授式的部分自动获取知识的功能。 BFBEST开发机是在IBM-PC机上用Turbo-Prolog语言实现的。它实用性强、智能化程度高,能用来快速生成各种高性能的医学专家系统知识库。 相似文献
199.
有迎角的再入旋转钝锥由于周向烧蚀滞后将产生滚转力矩。在烧蚀滞后滚转力矩的计算方法中。本文主要介绍滞后引射率和粗糙度对壁面磨擦系数联合影响的一种快速计算方法。给出计算结果与实验数据的比较,分析烧蚀滞后滚转力矩的模数随飞行参数的变化。 相似文献
200.
为了深入了解旋转作用对回转内通道换热特征的影响,采用三维数值模拟方法研究旋转数、旋转半径对带肋内通道模型的流动换热影响。通道入口雷诺数为1.7×104、旋转数范围为0~0.09,出口1、出口2、出口3的质量流量分配比为1∶2∶1,旋转半径与水力直径之比的范围为0~69.6。结果表明:旋转作用力使径向出流通道的压力系数逐渐增大,径向入流通道的压力系数迅速减小;径向出流通道后缘面的努赛尔数(Nu)随旋转数增加而增大,径向入流通道后缘面的Nu随旋转数增加而减小,前缘面Nu随旋转数变化情况相反;前、后缘面Nu沿流向均随旋转半径与水力直径比的增加略有增大,旋转半径变化对壁面换热影响较小。 相似文献