共查询到20条相似文献，搜索用时 15 毫秒
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《中国沙漠》1988,(4)
Interna1Dy.,amic Causes ofDesertiflcatlollDeveloPmentin SemiaridZ。Je··,…·,………………………………………………。………………‘··Liu shu(二)APPlying Grey Relational Garde for AnalJsc tbe SuPPly of Runoff inTacheng AUUa…·‘·‘·’……。”·’··’·‘·‘·”…‘。、…TUng Q3ch*ng Zho0 DeZqqan(9)The Study of Siind SahaNon MovemeiiZ w八hPhgh Vebc八yClnecaUera·’…’…’··“”“·”‘“·’‘“’”“·””·”‘·”““·‘··’·He Da1Ja了lg Gao YOOggang(18)D6ydo… 相似文献
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Susan E. Hume 《The Professional geographer》2013,65(4):555-557
Research on small cities has begun to attract the attention of scholars who argue that contemporary urban scholarship, in its preoccupation with the largest and most advanced world-class cities, have largely ignored small to medium-sized cities. In China, although much attention has been paid to economically advanced urban centers, there actually has been a steady stream of work on small cities. This article profiles how a comparatively smaller city in western China attempts to market itself by selectively placing itself within various social–spatial and political–economic realities. Through Jinghong, we illustrate how local officials and planners attempt to center the city as a gateway to Southeast Asia. By activating, often discursively, multiscalar transborder strategies, local officials in Jinghong not only mobilize ethnic imaginaries, but they also adopt forms of entrepreneurial tactics to promote growth. Developmental strategies of Jinghong not only vacillate between (and draw on) both rural and urban resources; they are furthermore expected to alleviate rural poverty. Through highlighting the agency of small cities like Jinghong in China, this article speaks to the broader developmentalist critique of third- and fourth-world cities as an unfortunate footnote in global urban restructuring, often depicted as places of uniform marginalization and structural irrelevance. Indeed, by focusing on the geography of small cities and giving due attention to their size and proximity to rural spaces, case studies like Jinghong might yet point empathetically to different ways and imperatives of “being urban” where the weight that they carry can also be duly recognized. 相似文献
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J. T. COPPOCK 《International journal of geographical information science》2013,27(2):191-192
ABSTRACT A wide range of environmental process simulations would benefit from the development of GIS able to cope with the additional dimensions of vertical space and time, and having extended spatial modelling facilities. The results of a project in the first of these areas, namely on the development of techniques for handling four-dimensional (4-D) data, are described. The key topics of data models, visualization and interpolation have been studied. Problems include the large size of some 4-D data sets, the sparseness of sampling in some dimensions compared with others, and the need to combine data sets from different sensors which may be of different dimensionalities and scales. The gridded volume data common to most environmental models are stored in a 4-D bintree form in which all dimensions are treated identically. Simple 4-D objects may also be stored, and links are provided between volume and object databases. The techniques have been implemented within a computational testbed allowing parallel processing to cope with large data sizes. 相似文献
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David J. Magutre 《International journal of geographical information science》2013,27(4):487-488
The integration of multisource heterogeneous spatial data is one of the major challenges for many spatial data users. To facilitate multisource spatial data integration, many initiatives including federated databases, feature manipulation engines (FMEs), ontology-driven data integration and spatial mediators have been proposed. The major aim of these initiatives is to harmonize data sets and establish interoperability between different data sources. On the contrary, spatial data integration and interoperability is not a pure technical exercise, and there are other nontechnical issues including institutional, policy, legal and social issues involved. Spatial Data Infrastructure (SDI) framework aims to better address the technical and nontechnical issues and facilitate data integration. The SDIs aim to provide a holistic platform for users to interact with spatial data through technical and nontechnical tools. This article aims to discuss the complexity of the challenges associated with data integration and propose a tool that facilitates data harmonization through the assessment of multisource spatial data sets against many measures. The measures represent harmonization criteria and are defined based on the requirement of the respective jurisdiction. Information on technical and nontechnical characteristics of spatial data sets is extracted to form metadata and actual data. Then the tool evaluates the characteristics against measures and identifies the items of inconsistency. The tool also proposes available manipulation tools or guidelines to overcome inconsistencies among data sets. The tool can assist practitioners and organizations to avoid the time-consuming and costly process of validating data sets for effective data integration. 相似文献
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Roger K. Wiebusch 《社会与自然资源》2017,30(1):16-30
While conversion of wetlands to nonagricultural purposes has persisted, the five U.S. national wetland inventory reports spanning 1955–2009 show a large decline in the rate of conversion of wetlands for agriculture, especially from the mid-1970s to the mid-1990s. Through regression and path analysis, this study identifies primary policy and economic drivers of this decline in wetland conversions. The Clean Water Act §404 is strongly and negatively related to conversion rates. Crop prices affect wetland conversions both directly, by influencing returns to investments for conversion, and indirectly, by influencing Conservation and Wetland Reserve Program enrollments as well as the regulatory impact of Swampbuster. Along with the proportion of wetlands remaining, these factors explain 90–94% of the annual variation in total wetland conversions, agricultural conversions, and conversion of forested and emergent wetlands. 相似文献
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PAUL MATHER 《International journal of geographical information science》2013,27(2):258-259
As they increase in popularity, social media are regarded as important sources of information on geographical phenomena. Studies have also shown that people rely on social media to communicate during disasters and emergency situation, and that the exchanged messages can be used to get an insight into the situation. Spatial data mining techniques are one way to extract relevant information from social media. In this article, our aim is to contribute to this field by investigating how graph clustering can be applied to support the detection of geo-located communities in Twitter in disaster situations. For this purpose, we have enhanced the fast-greedy optimization of modularity (FGM) clustering algorithm with semantic similarity so that it can deal with the complex social graphs extracted from Twitter. Then, we have coupled the enhanced FGM with the varied density-based spatial clustering of applications with noise spatial clustering algorithm to obtain spatial clusters at different temporal snapshots. The method was experimented with a case study on typhoon Haiyan in the Philippines, and Twitter’s different interaction modes were compared to create the graph of users and to detect communities. The experiments show that communities that are relevant to identify areas where disaster-related incidents were reported can be extracted, and that the enhanced algorithm outperforms the generic one in this task. 相似文献
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In 2013, we celebrate the 50th anniversary of the publication of V. B. Sochava’s first paper in which he offered the definition of the term “geosystem”. His paper entitled “The definition of some notions and terms in physical geography” remains one of the most frequently cited articles in the national geographical literature. The concept of the geosystem was included in encyclopedias. The geosystem ideology is used in training of specialists in the field of geography. 相似文献
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Because of differential isostatic rebound, many lakes in Canada have continued to change their extent and depth since retreat of the Laurentide Ice Sheet. Using GIS techniques, the changing configuration and bathymetry of Lake of the Woods in Ontario, Manitoba, and Minnesota were reconstructed for 12 points in time, beginning at 11,000 cal yr B.P. (9.6 14C ka B.P.), and were also projected 500 years into the future, based on the assumption that Lake of the Woods continued to have a positive hydrological budget throughout the Holocene. This modeling was done by first compiling a bathymetric database and merging that with subaerial data from the Shuttle Radar Topography Mission (SRTM). This DEM file was then adjusted by: (1) isobase data derived from Lake Agassiz beaches prior to 9000 cal yr B.P. (8.1 14C ka B.P.) and (2) modeled isostatic rebound trend analysis after 9000 cal yr B.P. Just after the end of the Lake Agassiz phase of Lake of the Woods, only the northernmost part of the basin contained water. Differential rebound has resulted in increasing water depth. In the first 3000 years of independence from Lake Agassiz, the lake transgressed >50 km to the south, expanding its area from 858 to 2857 km2, and more than doubling in volume. Continued differential rebound after 6000 cal yr B.P. (5.2 14C ka B.P.) has further expanded the lake, although today it is deepening by only a few cm per century at the southern end. In addition, climate change in the Holocene probably played a role in lake level fluctuations. Based on our calculation of a modern hydrological budget for Lake of the Woods, reducing runoff and precipitation by 65% and increasing evaporation from the lake by 40% would end overflow and cause the level of the lake to fall below the outlets at Kenora. Because this climate change is comparable to that recorded during the mid-Holocene warming across the region, it is likely that the area covered by the lake at this time would have been less than that determined from differential isostatic rebound alone. 相似文献
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Daniel Bedford 《The Journal of geography》2016,115(5):187-197
Educators seeking to address global warming in their classrooms face numerous challenges, including the question of whether student opinions about anthropogenic global warming (AGW) can change in response to increased knowledge about the climate system. This article analyzes survey responses from 458 students at a primarily undergraduate institution in the U.S.’s intermountain West, finding increased levels of concern with increased levels of climate literacy, including among students whose political affiliation might indicate skepticism about AGW. However, overall levels of climate literacy were found to be quite low for many students, allowing other factors, notably political affiliation, to become dominant predictors of AGW concern. 相似文献
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