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为了计算复杂目标的雷达散射截面(RCS),提出了一种基于AutoCAD几何建模的近场目标电磁散射计算技术,计算了单元体,组成体以及飞机的近场雷达散射截面,理论计算和实测结果较为吻合,为在微机上计算复杂目标近场RCS提供了一种理想的方法。 相似文献
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G. Ooms H. Wittenberg C. de Jager K. Pinkau A. Lehr K. Rinner 《Space Science Reviews》1979,24(3):367-368
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Alixe Buckerfield de la Roche 《Space Policy》2011,27(4):247-249
The RUSI Space and UK National Security Conference was held in London, 14 June 2011. Alixe Buckerfield de la Roche reports on some of the key themes discussed, including the increasing merger of space and cyber, the growing urgency in calling for development of robust and effective regulatory frameworks for orbital management, and the challenges surrounding national resilience achieved through space situational awareness. At RUSI’s 12th Missile Defence Conference held the same week Secretary General Rasmussen gave an address on NATO’s missile policy—focusing on partnerships and collaboration. His comments intersect aptly with the Space and UK National Security conference themes and are therefore included here. 相似文献
318.
David Auslander Joshua Cermenska Gregory Dalton Mauricio de la Pena C. K. H. Dharan William Donokowski Robert Duck Jonghak Kim David Pankow Alec Plauche Mustapha Rahmani Stephen Sulack Tien Fak Tan Paul Turin Tyler Williams 《Space Science Reviews》2008,141(1-4):185-211
The five “Time History of Events and Macroscale Interactions during Substorms” (THEMIS) micro-satellites launched on a common carrier by a Delta II, 7925 heavy, on February 17, 2007. This is the fifth launch in the NASA MeDIum class EXplorer (MIDEX) program. In the mission proposal the decision was made to have the University of California Berkeley Space Sciences Laboratory (UCB-SSL) mechanical engineering staff provide all of the spacecraft appendages, in order to meet the short development schedule, and to insure compatibility. This paper describes the systems engineering, design, development, testing, and on-orbit deployment of these boom systems that include: the 1 and 2 meter carbon fiber composite magnetometer booms, the 40 and 50 m tip to tip orthogonal spin-plane wire boom pairs, and the 6.3 m dipole stiff axial booms. 相似文献
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Microbial rock inhabitants survive hypervelocity impacts on Mars-like host planets: first phase of lithopanspermia experimentally tested 总被引:3,自引:0,他引:3
Horneck G Stöffler D Ott S Hornemann U Cockell CS Moeller R Meyer C de Vera JP Fritz J Schade S Artemieva NA 《Astrobiology》2008,8(1):17-44
The scenario of lithopanspermia describes the viable transport of microorganisms via meteorites. To test the first step of lithopanspermia, i.e., the impact ejection from a planet, systematic shock recovery experiments within a pressure range observed in martian meteorites (5-50 GPa) were performed with dry layers of microorganisms (spores of Bacillus subtilis, cells of the endolithic cyanobacterium Chroococcidiopsis, and thalli and ascocarps of the lichen Xanthoria elegans) sandwiched between gabbro discs (martian analogue rock). Actual shock pressures were determined by refractive index measurements and Raman spectroscopy, and shock temperature profiles were calculated. Pressure-effect curves were constructed for survival of B. subtilis spores and Chroococcidiopsis cells from the number of colony-forming units, and for vitality of the photobiont and mycobiont of Xanthoria elegans from confocal laser scanning microscopy after live/dead staining (FUN-I). A vital launch window for the transport of rock-colonizing microorganisms from a Mars-like planet was inferred, which encompasses shock pressures in the range of 5 to about 40 GPa for the bacterial endospores and the lichens, and a more limited shock pressure range for the cyanobacterium (from 5-10 GPa). The results support concepts of viable impact ejections from Mars-like planets and the possibility of reseeding early Earth after asteroid cataclysms. 相似文献