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921.
Schulze-Makuch D Méndez A Fairén AG von Paris P Turse C Boyer G Davila AF António MR Catling D Irwin LN 《Astrobiology》2011,11(10):1041-1052
In the next few years, the number of catalogued exoplanets will be counted in the thousands. This will vastly expand the number of potentially habitable worlds and lead to a systematic assessment of their astrobiological potential. Here, we suggest a two-tiered classification scheme of exoplanet habitability. The first tier consists of an Earth Similarity Index (ESI), which allows worlds to be screened with regard to their similarity to Earth, the only known inhabited planet at this time. The ESI is based on data available or potentially available for most exoplanets such as mass, radius, and temperature. For the second tier of the classification scheme we propose a Planetary Habitability Index (PHI) based on the presence of a stable substrate, available energy, appropriate chemistry, and the potential for holding a liquid solvent. The PHI has been designed to minimize the biased search for life as we know it and to take into account life that might exist under more exotic conditions. As such, the PHI requires more detailed knowledge than is available for any exoplanet at this time. However, future missions such as the Terrestrial Planet Finder will collect this information and advance the PHI. Both indices are formulated in a way that enables their values to be updated as technology and our knowledge about habitable planets, moons, and life advances. Applying the proposed metrics to bodies within our Solar System for comparison reveals two planets in the Gliese 581 system, GJ 581 c and d, with an ESI comparable to that of Mars and a PHI between that of Europa and Enceladus. 相似文献
922.
A. V. Shchukin A. V. Il’inkov S. G. Dezider’ev S. N. Ivanov 《Russian Aeronautics (Iz VUZ)》2013,56(4):384-389
This paper reports the results of an experimental study of heat transfer using a model of the internal cooled surface of the turbine blade leading edge. We investigated a joint action of air jets and hemispherical protrusions on heat transfer from the concave surface of the leading edge model to air. 相似文献
923.
M.C. Ramadevi S. Seetha V.C. Babu B.N. Ashoka P. Sreekumar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):3002-3004
The Scanning Sky Monitor (SSM) on ASTROSAT is a position-sensitive gas-filled proportional counter with a wide field of view. The scientific objective of SSM is to scan the sky within few hours to detect and locate transient X-ray sources in the outburst phase. Once detected, this information will be provided for studies in all energy bands. The energy range of operation of SSM is 2–10 keV. The optimisation of the parameters of the proportional counter such as the cell size, the gas mixture and the gas pressure for the SSM are discussed here. 相似文献
924.
The mathematical models of the solid-liquid flow regimes in the vertical cylindrical channel are described. A two-speed flow based on the solid-liquid phase interaction is considered. The problem was numerically solved and the calculation results were compared with experimental data. 相似文献
925.
Blachman N.M. Mousavinezhad S.H. 《IEEE transactions on aerospace and electronic systems》1986,(1):2-7
Bessel functions, used extensively in mathematical physics, electromagnetics, and communication-system theory, must often be approximated by appropriate formulas. The functions J?(x) and I?(x) for integer values of p are well approximated by the sum of a small number of circular and hyperbolic sines or cosines, respectively, when x is not too large, e.g., less than 10, and convenient expressions are obtained for their errors. These approximations are especially convenient for use on personal computers (PCs) and pocket calculators and in analytically evaluating integrals. 相似文献
926.
Lammer H Lichtenegger HI Kulikov YN Griessmeier JM Terada N Erkaev NV Biernat HK Khodachenko ML Ribas I Penz T Selsis F 《Astrobiology》2007,7(1):185-207
Atmospheric erosion of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wave-lengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 microm band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O ion pick up at orbital distances 相似文献
927.
N G Dachev TsP "Y ">Matviichuk YuN "Y ">Bankov J V Semkova R T Koleva B T Ivanov YaJ "Y ">Tomov V M Petrov V A Shurshakov V V Bengin V S Machmutov N A Panova T A Kostereva V V Temny R Ponomarev YuN "Y ">Tykva 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(2-3):321-324
Using data from dosimetry-radiometry system \"Liulin\" on board of \"Mir\"-space station the particle flux and doserate during September-October, 1989 has been studied. The orbit of the station was 379 km perigee, 410 km apogee and 51.6 degrees inclination. Special attention has been paid to the flux and doserate changes inside the station after intensive solar proton events (SPE) on 29 of September, 1989. The comparison between the doses before and after the solar flares shows increase of the calculated mean dose per day by factor of 10 to 200. During the SPE on the 29 of September the additional dose was 310 mrad. The results of the experiment are compared with the data for the solar proton fluxes obtained on the GOES-7 satellite. 相似文献
928.
This paper presents the results of investigating optical phenomena in the upper atmosphere that accompany rocket launches and are associated with specific features of the structure and dynamics of gas-dust formations in the upper atmosphere. The most intense, large-scale, and dynamic phenomena are induced by specific operation modes of rocket engines, in particular, by the staging and thrust cutoff in solid-propellant rocket engines, as well as by physical conditions in the upper atmosphere. 相似文献
929.
930.
N. A. Bryukhanov V. V. Tsvetkov M. Yu. Belyaev E. V. Babkin T. V. Matveeva V. V. Sazonov 《Cosmic Research》2006,44(1):48-57
Results of in-flight tests of three modes of uncontrolled attitude motion of the Progress spacecraft are described. These proposed modes of experiments related to microgravity are as follows: (1) triaxial gravitational orientation, (2) gravitational orientation of the rotating satellite, and (3) spin-up in the plane of the orbit around the axis of the maximum moment of inertia. The tests were carried out from May 24 to June 1, 2004 onboard the spacecraft Progress M1-11. The actual motion of this spacecraft with respect to its center of mass, in the above-mentioned modes, was determined by telemetric information about an electric current tapped off from solar batteries. The values of the current obtained during a time interval of several hours were processed jointly using the least squares method by integration of the equations of the spacecraft’s attitude motion. The processing resulted in estimation of the initial conditions of motion and of the parameters of mathematical models used. For the obtained motions the quasi-static component of microaccelerations was computed at a point onboard, where installation of experimental equipment is possible. 相似文献