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271.
272.
Raulin F Frere C Paillous P De Vanssay E Do L Khlifi M 《Journal of the British Interplanetary Society》1992,45(6):257-271
Titan, the largest satellite of Saturn, has a dense N2-CH4 atmosphere rich in organic compounds, both in gas and in aerosol phases. Its surface is probably covered by oceans of liquid methane-ethane mixtures, with many dissolved organics. This quasi planet appears as a natural laboratory to study chemical evolution toward complex organic systems in a planetary environment over a long time scale. With the Cassini-Huygens mission NASA and ESA will jointly send an orbiter (Cassini) around Saturn and a probe (Huygens) in the atmosphere of Titan. This mission, currently planned to be launched in 1996-1997 for a Saturn - Titan arrival in 2004, offers a unique opportunity to study in detail extra-terrestrial organic processes. Consequently, it has important implications in the field of exobiology and the origins of life. 相似文献
273.
B. Zolesi L.R. Cander G. De Franceschi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(12):57-60
A simplified model of the key vertical-incidence ionospheric characteristics such as f0 F2, M(3000) F2, h'F, f0F1, and f0E that are used for prediction of operational parameters of HF telecommunication system in restricted area has been developed. The model is based upon the Fourier analysis of the monthly median values of these characteristics from seven ionospheric stations in Europe. It is shown that only 12 dominant Fourier coefficeints, expressed as function of local time, solar activity and geographic latitude are sufficient to reproduce the main features of the diurnal, seasonal and solar cycle behaviour of the mid-latitude ionosphere under median conditions. 相似文献
274.
The ALTEA/ALTEINO projects: studying functional effects of microgravity and cosmic radiation. 总被引:1,自引:0,他引:1
L Narici F Belli V Bidoli M Casolino M P De Pascale L Di Fino G Furano I Modena A Morselli P Picozza E Reali A Rinaldi D Ruggieri R Sparvoli V Zaconte W G Sannita S Carozzo S Licoccia P Romagnoli E Traversa V Cotronei M Vazquez J Miller V P Salnitskii O I Shevchenko V P Petrov K A Trukhanov A Galper A Khodarovich M G Korotkov A Popov N Vavilov S Avdeev M Boezio W Bonvicini A Vacchi N Zampa G Mazzenga M Ricci P Spillantini G Castellini R Vittori P Carlson C Fuglesang D Schardt 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(8):1352-1357
275.
Preliminary validation of computational procedures for a new atmospheric ionizing radiation (AIR) model. 总被引:1,自引:0,他引:1
John M Clem Giovanni De Angelis Paul Goldhagen John W Wilson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,32(1):27-33
A new computational procedure to determine particle fluxes in the Earth's atmosphere is presented. The primary cosmic ray spectrum has been modeled through an analysis of simultaneous proton and helium measurements made on high altitude balloon flights and spacecraft. An improved global fit to the data was achieved through applying a unique technique utilizing the Fokker-Plank equation with a non-linear rigidity-dependent diffusion coefficient. The propagation of primary particles through the Earth's atmosphere is calculated with a three-dimensional Monte Carlo transport program called FLUKA. Primary protons and helium nuclei (alphas) are generated within the rigidity range of 0.5 GV-20 TV uniform in cos2 theta. For a given location, primaries above the effective cutoff rigidity are transported through the atmosphere. Alpha particles are initially transported with a separate package called HEAVY to simulate fragmentation. This package interfaces with FLUKA to provide interaction starting points for each nucleon originating from a helium nucleus. Results from this calculation are presented and compared to measurements. 相似文献
276.
对在不锈钢基体上用离子束混合技术沉积的C-SiC涂层,进行了二次离子质谱(SIMS)及傅氏变换红外吸收光谱(FI-IR)的分析。研究了不锈钢基体涂覆H+辐照前后的氢浓度分布以及H^ 辐照前后涂层的红外光谱振动吸收峰的变化,对SiC涂层阻氢的机理进行了探讨。 相似文献
277.
模态综合法计算双转子临界转速研究 总被引:5,自引:0,他引:5
采用模态综合法计算了双转子临界转速,子结构模态由传递矩阵法求得,并着重研究了对接条件、模态数及子振形拟合多项式等因素对双转子临界转速影响。改进了双转子临界转速传递矩阵法并以传递矩阵法算得系统临界转速为准,评定了各种条件下模态综合法的计算精度。结果表明:取一阶为平动模态,其余模态由传递矩阵法求得,拆分为子系统时采用自由子系统法,采用位移协调对接条件、子振形取4次拟合多项式、仅取4阶模态求得了具有一定精度的l~3阶临界转速。在提高模态综合质量方面得出了一些有参考价值的结论。 相似文献
278.
用两个典型的对象,研究了非定常空气动力最小状态拟合方法应用中的问题,并给出了相应的结论。 相似文献
279.
The Solar Maximum Year is a world-wide cooperative project to gain more insight in certain aspects of solar flares. It consists of three sub-programs: The Flare Build-up Study (FBS), the Study of Energy Release from Flares (SERF), and the Study of Travelling Interplanetary Phenomena (STIP). These programs are described. We also describe space observations to be performed during SMY, particularly the Solar Maximum Mission Satellite.Invited talk, presented at 22nd COSPAR Meeting in Bangalore on 7 June, 1979. 相似文献
280.