排序方式: 共有101条查询结果,搜索用时 218 毫秒
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Ralph E. J. Boerner Michael N. DeMers John W. Simpson Francisco J. Artigas Alejandra Silva Leslie A. Berns 《Geographical analysis》1996,28(1):56-66
This study examined landcover change during 1940–1988 in two contiguous landscapes of approximately 12,400 hectares in central Ohio, USA: an inertial till plain area and a more dynamic moraine area. Agriculture dominated both landscapes throughout, however, the cover of natural vegetation and urban-suburban development increased over time on the moraine while natural vegetation decreased and agriculture increased on the till plain. Markov process models for landcover change were constructed for three 14–17-year time intervals and for the entire forty-eight-year study period. Probabilities of self-replacement for agricultural lands (0.91–0.97) were higher and those for forests (0.54–0.65) lower than those reported for other landscapes. Predictions of landcover percentages for fifty years in the future were made using Markov process models derived from actual cover changes in 1940–1957, 1971–1988, and 1940–1988. All three models produced similar predictions for the inertial till plain area. In contrast, the three models' predictions differed considerably for the moraine area. Only the 1971–1988 transition matrix was sensitive to increases in urbanization and reforestation which began on the moraine in the 1970s. These results indicate that reliance on lengthy study intervals and net rates of change can obscure spatial and temporal patterns of landcover change that are caused by natural and socioeconomic factors operating on shorter time scales. 相似文献
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H. Barnard W. Z. Wendrich A. Winkels J. E. M. F. Bos B. L. Simpson R. T. J. Cappers 《Journal of Field Archaeology》2016,41(1):84-100
Excavations in the arid regions of Egypt provide insight into the many types and uses of mudbrick architecture. Upon exposure the inherently unstable building material decays rapidly, resulting in severe loss or complete destruction of once well-preserved buildings. The preservation of mudbrick structures is relatively complicated and expensive. Research has focused on the circumstances that enable preservation and the influence of climate and weather over time. Conservation treatments should address these two processes as soon as possible after exposure of the structures. Our assessment of a range of conservation methods leads to the conclusion that reburial is among the least objectionable method of preservation, despite its drawback of returning the excavated buildings to a situation where they are invisible to both researchers and the public. 相似文献
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Marianna Shreve Simpson 《Iranian studies》2011,44(4):596-601
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Brad Simpson 《Journal of Genocide Research》2014,16(2-3):337-354
The Biafran secession crisis raised a series of profound and unanswerable questions about the nature and limits of self-determination, state sovereignty and African decolonization. A wide range of actors—both supporters and opponents of Biafra—viewed the Nigerian civil war and Biafra's attempt to carve out a new state as an important moment in the history of self-determination as a political and legal principle. Likewise, the collapse of Biafra seemed to offer a series of lessons for movements asserting their right to self-determination, as well as for those seeking to limit its application, suggesting the open-ended and contested nature of the concept even as it was institutionalized in the fabric of international human rights law. Ultimately, however, Biafra's failed secession attempt could only highlight the ambiguity and contested nature of sovereignty and self-determination in the international system, and the ability of groups such as the Igbos to exploit their indeterminacy in an effort to achieve their aims. 相似文献