The most fundamental character of lunar soil is its high concentrations of solar-wind-implanted elements, and the concentrations and behavior of the noble gases He, Ne, Ar, and Xe, which provide unique and extensive information about a broad range of fundamental problems. In this paper, the authors studied the forming mechanism of lunar regolith, and proposed that most of the noble gases in lunar regolith come from the solar wind. Meteoroid bombardment controls the maturity of lunar soil, with the degree of maturation decreasing with grain size; the concentrations of the noble gases would be of slight variation with the depth of lunar soil but tend to decrease with grain size. In addition, the concentrations of noble gases in lunar soil also show a close relationship with its mineral and chemical compositions. The utilization prospects of the noble gas ^3He in lunar regolith will be further discussed. 相似文献
Identifying and analyzing the urban–rural differences of social vulnerability to natural hazards is imperative to ensure that urbanization develops in a way that lessens the impacts of disasters and generate building resilient livelihoods in China. Using data from the 2000 and 2010 population censuses, this study conducted an assessment of the social vulnerability index (SVI) by applying the projection pursuit cluster model. The temporal and spatial changes of social vulnerability in urban and rural areas were then examined during China’s rapid urbanization period. An index of urban–rural differences in social vulnerability (SVID) was derived, and the global and local Moran’s I of the SVID were calculated to assess the spatial variation and association between the urban and rural SVI. In order to fully determine the impacts of urbanization in relation to social vulnerability, a spatial autoregressive model and Bivariate Moran’s I between urbanization and SVI were both calculated. The urban and rural SVI both displayed a steadily decreasing trend from 2000 to 2010, although the urban SVI was always larger than the rural SVI in the same year. In 17.5% of the prefectures, the rural SVI was larger than the urban SVI in 2000, but was smaller than the urban SVI in 2010. About 12.6% of the urban areas in the prefectures became less vulnerable than rural areas over the study period, while in more than 51.73% of the prefectures the urban–rural SVI gap decreased over the same period. The SVID values in all prefectures had a significantly positive spatial autocorrelation and spatial clusters were apparent. Over time, social vulnerability to natural hazards at the prefecture-level displayed a gathering–scattering pattern across China. Though a regional variation of social vulnerability developed during China’s rapid urbanization, the overall trend was for a steady reduction in social vulnerability in both urban and rural areas.
Collected by means of a high-altitude scientific balloon and a self-made automatic sample collector,a total of 276 dust grains were selected for the study of shape,grain size and optical property.Some of the grains were examined by X-ray diffraction and electrom microprobe techniques,The stratospheric dust grains can be classified as 6 types:cosmic dusts,cosmic dusts(?),microtektite,natural pollutants,artificial pollutants and the unknown substances.The different types of dust grains have different characters and distinguishing symbols.Widespread in the space of the solar system,cosmic dusts are the initial substances of the solar system and ,to some degree,have recorded a great wealth of information on the early history of the solar system.So they have become one of the important objects in the field of cosmochemistry at present time,Since the 1960‘s,scholars of many countries have collected cosmic dusts both in the space near the earth(using rock ets,space probes and space shuttles)and in the stratosphere (using high-altitude balloons or U-2air planes).According to the shape(the scanning electron microimage),element composition(the energy-dispersive X-ray spectrum)and optical properties of dust grains,the substances in the stratosphere can be classified as 5 types:cosmic dusts,alumina spheroids,terrestrial artificial pollutants,terrestrial natural pollutants and unknown substances(CDPET,1982). 相似文献
Samples are available from 37 stony meteorites falling in China. Twenty-two chondrites are examined in terms of chemical and mineral compositions, cosmogenic nuclides, formation and exposure ages, impact effect and chondrule textures. On the basis of chemical-petrologic features these chondrites are classified asE4 (Qingzhen),H5 (Jilin, Changde, Shuangyang, Anlong, Xinyi and Yangjang),L6 (Renqiu, Junan, Heze, Rugao and Nei Monggol) andLL6 (Dongtai). E4 is characterized by high iron and sulfur, with the former occurring mainly as Feo and FeS. FromH5 throughH6 toLL6, iron and nickel decrease gradually while FeO and the ratio of Fe silicate to total iron increase gradually. indicating a general increase in the orderE-H-L-LL in the degree of oxidation at the time of formation. E4 consists mainly of enstatite and, to much less extent, free SiO2 but olivine is hardly to be found. The olivine proportions amount to 29.07, 41.98 and 51.36 percent inH5,L6 andLL6 respectively, with Fa increasing from 17 to 27 percent. Recrystallization has been noticed to different degrees inH4,H5,L6 andLL6 chondrites. The extent to which the original structure disappears and the boundaries of chondrules become indistinct decreases from type 6 through type 5 to type 4, reflecting different degrees of thermal metamorphism. Major minerals in the meteorites all exhibit signs of low to medium shock metamorphism. Specific activity, depth effect and orbit effect are also measured on some chondrites that have fallen in recent years and some new information has been obtained with respect to the orbit and source region for meteorite parent bodies in space. This results show that the environment of formation ofE group may be nearer to Mars than that ofO group. Each chemical group of chondrites has its own evolutionary history, and chondritets of different chemical groups may have originated from parent bodies of different compositions. Or owing to the differentiation caused by thermal melamorphism, various kinds of meteorites may be derived from a common parent body. From this argument it is suggested that five stages may be recognized during the formation process of chondrites. 相似文献
Clementine UVVIS and NIR data from the lunar sampling sites (totaling 46 sampling sites) were processed and used to refine the iron determination method of Le Mouéic et al. (2000, 2002). We found that about 21 sampling sites are unsuitable to Le Mouéic et al's spectral parameters ("slope" and "depth l") because their 1500 nm filter could not be used as spectral parameters' right shoulders and to evaluate the depth of the 1-μm absorption feature accurately. We used the rest 25 sampling sites to refine the method developed by Le Mouéic et al. (2000, 2002 ) and obtained our own equation of FeO content determination. We tested our own equation, and the results are satifactory. In our work we also acquired some useful experiences in scientific applications of our own dataset of the Chang'E-1 mission. 相似文献