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Karim Douch Hu Wu Christian Schubert Jürgen Müller Franck Pereira dos Santos 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(5):1307-1323
The prospects of future satellite gravimetry missions to sustain a continuous and improved observation of the gravitational field have stimulated studies of new concepts of space inertial sensors with potentially improved precision and stability. This is in particular the case for cold-atom interferometry (CAI) gradiometry which is the object of this paper. The performance of a specific CAI gradiometer design is studied here in terms of quality of the recovered gravity field through a closed-loop numerical simulation of the measurement and processing workflow. First we show that mapping the time-variable field on a monthly basis would require a noise level below . The mission scenarios are therefore focused on the static field, like GOCE. Second, the stringent requirement on the angular velocity of a one-arm gradiometer, which must not exceed ?rad/s, leads to two possible modes of operation of the CAI gradiometer: the nadir and the quasi-inertial mode. In the nadir mode, which corresponds to the usual Earth-pointing satellite attitude, only the gradient , along the cross-track direction, is measured. In the quasi-inertial mode, the satellite attitude is approximately constant in the inertial reference frame and the 3 diagonal gradients and are measured. Both modes are successively simulated for a 239?km altitude orbit and the error on the recovered gravity models eventually compared to GOCE solutions. We conclude that for the specific CAI gradiometer design assumed in this paper, only the quasi-inertial mode scenario would be able to significantly outperform GOCE results at the cost of technically challenging requirements on the orbit and attitude control. 相似文献
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Euan Nisbet Kevin Zahnle M. V. Gerasimov Jörn Helbert Ralf Jaumann Beda A. Hofmann Karim Benzerara Frances Westall 《Space Science Reviews》2007,129(1-3):79-121
The factors that create a habitable planet are considered at all scales, from planetary inventories to micro-habitats in soft
sediments and intangibles such as habitat linkage. The possibility of habitability first comes about during accretion, as
a product of the processes of impact and volatile inventory history. To create habitability water is essential, not only for
life but to aid the continual tectonic reworking and erosion that supply key redox contrasts and biochemical substrates to
sustain habitability. Mud or soft sediment may be a biochemical prerequisite, to provide accessible substrate and protection.
Once life begins, the habitat is widened by the activity of life, both by its management of the greenhouse and by partitioning
reductants (e.g. dead organic matter) and oxidants (including waste products). Potential Martian habitats are discussed: by
comparison with Earth there are many potential environmental settings on Mars in which life may once have occurred, or may
even continue to exist. The long-term evolution of habitability in the Solar System is considered. 相似文献
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Ahmed Moos Jalil Karim Ahmed Ali Hoobi 《中国航空学报》2007,20(2):134-139
IN 600 alloy was coated with two different types of coatings, Cr-modified aluminide coating this is called aluminizing-chromizing and Y-doped chromium modified aluminide coating this is called aluminizing-chromizing-yttriumizing. Diffusion coating was carried at 1 050 ℃ for 8 h under Ar atmosphere by simultaneous aluminizing-chromizing process and by simultaneous aluminizing-chromizing- yttriumizing. Cyclic oxidation tests were conducted on the uncoated and on the coated Inconel 600 alloy in the temperature range 800- 1 000 ℃ in CO2 for 100 h at 10 h cycle.The results showed that the oxidation kinetics for uncoated Inconel 600 alloy in CO2 is parabolic and the phases present are NiO, (Fe, Cr)2O3 , NiFe2O4 and NiCrO4. The oxidation kinetics for both coated systems in CO2 was found to be parabolic and the value of kP for both coated systems were found to be lower than that for uncoated Inconel 600 alloy. Oxide phases that formed on coated systems are Al2O3 and NiCrO4. The role of yttrium can be attributed to its ability to improve the adherence of the oxide scale. 相似文献
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P. van Thienen K. Benzerara D. Breuer C. Gillmann S. Labrosse P. Lognonné T. Spohn 《Space Science Reviews》2007,129(1-3):167-203
In our search for life on other planets over the past decades, we have come to understand that the solid terrestrial planets
provide much more than merely a substrate on which life may develop. Large-scale exchange of heat and volatile species between
planetary interiors and hydrospheres/atmospheres, as well as the presence of a magnetic field, are important factors contributing
to the habitability of a planet. This chapter reviews these processes, their mutual interactions, and the role life plays
in regulating or modulating them. 相似文献
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