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881.
Rosemary Killen Gabrielle Cremonese Helmut Lammer Stefano Orsini Andrew E. Potter Ann L. Sprague Peter Wurz Maxim L. Khodachenko Herbert I. M. Lichtenegger Anna Milillo Alessandro Mura 《Space Science Reviews》2007,132(2-4):433-509
It has been speculated that the composition of the exosphere is related to the composition of Mercury’s crustal materials.
If this relationship is true, then inferences regarding the bulk chemistry of the planet might be made from a thorough exospheric
study. The most vexing of all unsolved problems is the uncertainty in the source of each component. Historically, it has been
believed that H and He come primarily from the solar wind (Goldstein, B.E., et al. in J. Geophys. Res. 86:5485–5499, 1981), Na and K come from volatilized materials partitioned between Mercury’s crust and meteoritic impactors (Hunten, D.M., et
al. in Mercury, pp. 562–612, 1988; Morgan, T.H., et al. in Icarus 74:156–170, 1988; Killen, R.M., et al. in Icarus 171:1–19, 2004b). The processes that eject atoms and molecules into the exosphere of Mercury are generally considered to be thermal vaporization,
photon-stimulated desorption (PSD), impact vaporization, and ion sputtering. Each of these processes has its own temporal
and spatial dependence. The exosphere is strongly influenced by Mercury’s highly elliptical orbit and rapid orbital speed.
As a consequence the surface undergoes large fluctuations in temperature and experiences differences of insolation with longitude.
Because there is no inclination of the orbital axis, there are regions at extreme northern and southern latitudes that are
never exposed to direct sunlight. These cold regions may serve as traps for exospheric constituents or for material that is
brought in by exogenic sources such as comets, interplanetary dust, or solar wind, etc. The source rates are dependent not
only on temperature and composition of the surface, but also on such factors as porosity, mineralogy, and space weathering.
They are not independent of each other. For instance, ion impact may create crystal defects which enhance diffusion of atoms
through the grain, and in turn enhance the efficiency of PSD. The impact flux and the size distribution of impactors affects
regolith turnover rates (gardening) and the depth dependence of vaporization rates. Gardening serves both as a sink for material
and as a source for fresh material. This is extremely important in bounding the rates of the other processes. Space weathering
effects, such as the creation of needle-like structures in the regolith, will limit the ejection of atoms by such processes
as PSD and ion-sputtering. Therefore, the use of laboratory rates in estimates of exospheric source rates can be helpful but
also are often inaccurate if not modified appropriately. Porosity effects may reduce yields by a factor of three (Cassidy,
T.A., and Johnson, R.E. in Icarus 176:499–507, 2005). The loss of all atomic species from Mercury’s exosphere other than H and He must be by non-thermal escape. The relative
rates of photo-ionization, loss of photo-ions to the solar wind, entrainment of ions in the magnetosphere and direct impact
of photo-ions to the surface are an area of active research. These source and loss processes will be discussed in this chapter. 相似文献
882.
本文针对近期石油涨价以及全社会都在提倡节约的大气候,从现有能源的利用和新能源的开发两大方面谈能源合理利用与人类住区的可持续发展过程中应注意的问题,并提出相应的看法和建议。 相似文献
883.
一种电能表表号区域的定位方法 总被引:1,自引:1,他引:0
电能表表号可以唯一标识一块电能表的身份,针对当前对电能表表号识别研究比较少,研究了一种定位电能表表号区域的方法。由于电能表表面存在字符的区域比较多,定位电能表表号区域相对比较困难,结合了电能表表号数字区域的特征,通过对图片进行Canny边缘检测、数学形态学运算和区域限定,最后成功实现了电能表表号的定位。 相似文献
884.
I. Ueno Y. Abe K. Noguchi H. Kawamura 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(12):2145-2149
Three-dimensional (3-D) velocity field reconstruction of oscillatory thermocapillary convections in a half-zone liquid bridge with a radius of O (1 mm) was carried out by applying 3-D particle tracking velocimetry (PTV). Simultaneous observation of the particles suspended in the bridge by two CCD cameras was carried out by placing a small cubic beam splitter above a transparent top rod. The reconstruction of the 3-D trajectories and the velocity fields of the particles in the several types of oscillatory-flow regimes were conducted successfully for sufficiently long period without losing particle tracking. With this application the present authors conducted a series of experiments focusing upon the collapse and re-formation process of the PAS by mechanically disturbing fully developed PAS. 相似文献
885.
I.V. Arkhangelskaja Yu.D. KotovA.I. Arkhangelsky A.S. Glyanenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The count rate temporal profiles and energy spectra of the solar flares January 15, 17, 20 2005 in hard X-ray and gamma energy bands by data of AVS-F apparatus onboard CORONAS-F satellite are discussed. The energy spectra of these solar flares contain positron line and neutron capture line. Solar flares of January 17 and 20 spectra also contain some nuclear lines. Thin structure with characteristic timescales of 33–92 s is presented on flares temporal profiles in energy bands corresponding to the observed spectral features, which are confirmed by periodogram analysis (confidence level is 99%). 相似文献
886.
为提高某公司能源利用水平,减少污染物排放,针对该公司现正使用燃煤锅炉蒸汽加热方式所造成的高耗能、高污染、低效益问题,提出应用燃气替代燃煤并辅以部分电加热的技改方案,达到实现节能减排提高效益之目的。 相似文献
887.
888.
首次尝试将eQUEST用于机场航站楼能耗分析,应用表明具有计算速度快、输出能耗数据丰富、与实际能耗接近和便于进行各种能耗分析等优点.借助eQUEST还可对航站楼的建筑围护结构、空调系统和照明方案等进行设计、运行的节能优化. 相似文献
889.
本文通过一系列圆筒件的静态吸能试验研究了复合材料圆筒件静态吸能的特性。表明材料的吸能性能不仅同材料性能关系密切,而且也受材料纤维方式和工艺方法的影响。 相似文献
890.
本文通过在硅衬底上用MOCVD方法生长的砷化镓外延薄膜的变激发强度的近红外光致发光,研究了在液氮温度下峰值为1.13与1.04eV两个发光带的发光特性。 相似文献