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231.
R Marco J González-Jurado M Calleja R Garesse M Maroto E Ramírez M C Holgado E de Juan J Miquel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(1):157-166
The results are presented of the exposure of Drosophila melanogaster to microgravity conditions during a 15-day biosatellite flight, Biokosmos 9, in a joint ESA-URSS project. The experimental containers were loaded before launch with a set of Drosophila melanogaster Oregon R larvae so that imagoes were due to emerge half-way through the flight. A large number of normally developed larvae were recovered from the space-flown containers. These larvae were able to develop into normal adults confirming earlier results that Drosophila melanogaster of a wild-type constitution can develop normally in the absence of gravity. However, microgravity exposure clearly enhances the number of growing embryos laid by the flies and possibly slows down the developmental pace of the microgravity-exposed animals. Due to some problems in the experimental set-up, this slowing down needs to be verified in future experiments. No live adult that had been exposed to microgravity was recovered from the experiment, so that no life span studies could be carried out, but adult males emerged from the recovered embyros showed a slight shortening in life span and a lower performance in other experimental tests of aging. This agrees with the results of previous experiments performed by our groups. 相似文献
232.
Leonardo D. Chiwiacowsky Paolo Gasbarri Haroldo F. de Campos Velho 《Acta Astronautica》2008,62(10-11):592-604
The present investigation is focused on the solution of a dynamic inverse problem which is concerned with the assessment of damage in large space structures by means of measured vibration data. This inverse problem has been presented as an optimization problem and has been solved through the use of the conjugate gradient method with the adjoint equation, also called the variational approach. When a high number of damaged elements has to be found and these elements are also severely damaged, it is shown that the use of an additional method is necessary in order to provide a better initial guess for the conjugate gradient method. A stochastic method, represented by the genetic algorithm method, has been chosen because it provides robust search in complex spaces and also reduces the chance of converging to local optima. The application of this hybrid approach showed that better results can be achieved, although the computational time for the application analyzed here could increase. The damage estimation has been evaluated using noiseless and noisy synthetic experimental data, and the reported results are concerned with a space truss structure. 相似文献
233.
随着航空飞行器的不断发展,新型非常规气动布局研究早已成为世界航空大国的关注焦点。基于TRIP 3.0软件平台通过等效盘模型应用到涵道风扇内外流一体化模拟中,完成对类BWB低速布局有无涵道风扇动力下的气动特性和流场影响分析。首先,对某单独螺旋桨验证算例进行分析;然后,对单独涵道风扇进行计算,得到设计推力下的涵道动力叶片数、安装角及转速等参数;最后,将设计推力下涵道动力参数应用到类BWB低速布局全机有无动力模拟中。结果表明:计算拉力和扭矩值与试验值吻合较好;尾部布置的涵道动力对机身后段及尾翼压力分布影响显著;涵道对前方气流抽吸作用,加速机身后段上表面气流流速,减小内侧平尾有效迎角,对机身和平尾升力以及俯仰力矩系数影响较大;在小迎角状态下,涵道动力对机身增升作用明显,会产生明显低头力矩,但对平尾作用正好相反,且两者增量大小相当,使得全机增升效果不显著,且俯仰力矩变化较小。 相似文献
234.
P.A.J. de Korte J.J. Claas F.A. Jansen S.P. McKechnie 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(3):57-59
The EXOSAT observatory has detected the nucleus of NGC 1360 in four photometric energy bands. The data rules out that the emission is from blackbody origin. Initial fits made with LTE model atmosphere spectra require the presence of highly ionized Oxygen and Neon in the stellar atmosphere. 相似文献
235.
Bertrand de Montluc 《Space Policy》1997,13(1):9-14
The current international economic and technical climate has caused changes in the European space sector such that Italy is now struggling to maintain third place in the European hierarchy, the Franco-German relationship has become less dominant, while the UK is becoming more open towards European cooperation. This article analyses the current policies of Germany, the UK and Italy and examines their operating methods. The author speculates on the outlook for these countries in the next 10 years: neither the UK, nor Italy looks set to become a major player and German policy will depend on the success of its upcoming strategic plan. All these countries, and France, however, will need to engage in intensive bilateral consultations if they wish to compete in worldwide markets. 相似文献
236.
I.S. Batista J.R. de Souza M.A. Abdu E.R. de Paula 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(12):87-90
We used total electron content (TEC) data measured by Faraday rotation technique over Cachoeira Paulista (22.5°S, 45°W), in Brazil, to study the TEC variations with the solar flux at 10.7 cm (F10.7) and to compare the results with the IRI90 predictions. The data were divided into summer, equinox and winter. During the analysed period F10.7 varied from 66 up to 330. Our data shows that the observed TEC at 1600 LT (around the diurnal maximum) and at 0500 LT (around the diurnal minimum) increases with F10.7 until saturation is reached which occurs at F10.7≈210 to 220 for equinox and summer, and at F10.7≈180 for winter months. Comparison with the IRI90 predictions shows that IRI overestimates the TEC at 0500 LT for all solar flux values. At 1600 LT, IRI overestimates the observed TEC for low solar flux but underestimates it for high solar flux values. 相似文献
237.
Miroslav Plavec R. Hoekstra C. De Jager Ji⋖´ Grygar J. Otterman H. M. van den Dool O. Namba C. J. Th. Gunsing Jean-Claude Pecker K. K. Kwee L. Perek D. Callebaut Jan Kuijpers W. de Graaff G. C. M. Reijnen B. Swanenburg N. Grevesse J. Kleczek P. P≙quet A. D. Fokker H. G. van Bueren D. Edgar Page R. J. van Duinen Franco Pacini 《Space Science Reviews》1978,21(4):469-483
238.
E. A. Gurtovenko R. I. Kostik A. Tlamicha R. Zerull Aert Schadee A. Mészáros Y. Néeman R. H. Giese A. T. Sinclair J. Kleczek E. A. Trendelenburg Wolfgang Hillebrandt L. Sehnal W. de Graaff C. Slottje T. Courvisier H. F. van Beek B. Baud C. de Jager J. M. A. Danby B. V. Somov J. Cassinelli F. Verbunt 《Space Science Reviews》1986,44(1-2):177-188
239.
辐射换热条件下空间薄壁圆管结构瞬态温度场、热变形有限元分析 总被引:11,自引:1,他引:11
对航天结构中常见的辐射换热条件下的空间薄壁圆管结构,构造了一种用于非线性瞬态温度计算的傅立叶-有限单元。圆管温度沿杆长用有限元离散,沿周向分布展成三角函数。圆管温度单元每个结点包含平均温度、余弦和正弦分布温度幅三个自由度,并且在每个时间步内实现了平均温度增量与沿截面温差增量的解耦。在结构热变形分析时圆管单元节点上既承受温度轴力,又承受截面温差导致的热弯矩。采用这种单元对非线性换热条件下的复杂空间结构进行离散可以较准确地反映结构的温度场与热变形。经与前人的解析解和三维有限元结果的验证,证明该单元是可靠的。对太阳能帆板梁与空间抛物面天线的热-结构分析说明这种新单元的应用价值。 相似文献
240.