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第四纪地质环境的人工再造作用是一个新概念。文章在回顾人类文明历史发展的基础上,重点阐述了近50年来全球土地荒漠化发展的严重趋势。人工再造作用是人类过量的经济活动对岩石圈与生物圈接触介面产生的一种破坏作用,其动力是不断增长的世界人口及其巨大的物质需求。可将人工再造作用看作是第四纪中最新的一个地质事件。研究发现,这一破坏作用过程符合Logistic曲线的变化规律,因此可以采用Logistic数学模型开展深入研究。第四纪地质学家、环境地质学家对资源、环境、人口和可持续发展问题应给以更多的关注。 相似文献
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G. Bourgault 《Mathematical Geology》1996,28(6):723-734
A combination of factorial kriging and probability field simulation is proposed to correct realizations resulting from any simulation algorithm for either too high nugget effect (noise) or poor histogram reproduction. First, a factorial kriging is done to filter out the noise from the noisy realization. Second, the uniform scores of the filtered realization are used as probability field to sample the local probability distributions conditional to the same dataset used to generate the original realization. This second step allows to restore the data variance. The result is a corrected realization which reproduces better target variogram and histogram models, yet honoring the conditioning data. 相似文献
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《Geoforum》2016
In this paper, I articulate a notion of ‘social dispossession,’ an optic that extends current theorizing on agrarian dispossession into the realm of social reproduction, by examining the testimonies of microcredit borrowers in rural Bangladesh. In recent years, research on microcredit has highlighted new forms of subject-making employed by microcredit and other NGO entrepreneurship development programs. These developments have received insufficient attention in scholarship on agrarian change, both globally and in specific places. I correct this by arguing that microcredit drives social dispossession through three specific mechanisms: the confiscation of assets necessary to social reproduction (as well as to production); the construction of debt relations within a community which reshape what reproduction can look like; and the re-configuration of women’s social status and subjectivities in relation to their communities. 相似文献
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Short-term effects of fishing on life history traits of fishes 总被引:4,自引:4,他引:4
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The Gulf of Nicoya, an estuary on the Pacific coast of Central America, contains a large population of the portunid crab Callinectes arcuatus. Results of a 12 month survey indicated that spawning activity occurs throughout the year, but with a distinct peak during the five-month dry season (December-April). Mature females were most prevalent in the upper regions of the gulf during the rainy season and appeared to migrate to the lower gulf to spawn during the dry season. Patterns of spawning and apparent migration differed from those reported in an earlier study of C. arcuatus along the Pacific coast of Mexico. 相似文献