共查询到20条相似文献，搜索用时 31 毫秒
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Michael H. Finewood 《The Professional geographer》2013,65(3):468-470
California sage scrub (CSS) is a highly threatened vegetation community in coastal Southern California, 90 percent of which has been lost. Understanding CSS recovery is critical to its survival. This study compares long-term effects of grazing, cultivation, and mechanical disturbance in Southern California by tracking the extent of exotic grassland in two valleys in the Santa Monica Mountains over sixty years using aerial image analysis. Native shrubs returned to the grazed valley over one and one-half times faster than they did in the cultivated valley. Cultivation might result in a type conversion of CSS to exotic annual grassland that resembles a new steady state. 相似文献
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Giancarlo Biotto Lucia Gobbo Elisa Furlan Sonia Valenti Roberto Rosselli 《International journal of geographical information science》2013,27(10):1233-1244
This work deals with the identification of potentially contaminated areas using remote sensing, geographic information systems (GIS) and multi‐criteria spatial analysis. The identification of unknown illegal landfills is a crucial environmental problem in all developed and developing countries, where a large number of illegal waste deposits exist as a result of fast, and relatively unregulated, industrial growth over the past century. The criteria used to perform the spatial analysis are here selected by considering the characteristics which are ‘desirable’ for an illegal waste disposal site, chiefly related to the existence of roads for easy access and to a low population density which facilitates unnoticed dumping of illegal waste materials. A large dataset describing known legal and illegal landfills and the context of their location (population, road network, etc.) was used to perform a spatial statistical analysis to select factors and criteria allowing for the identification of the known waste deposits. The final result is a map describing the likelihood of an illegal waste deposit to be located at any arbitrary location. Such a probability map is then used together with remote sensing techniques to narrow down the set of possibly contaminated sites (Silvestri and Omri, 2008), which are candidates for further analyses and field investigations. The importance of the integration of GIS and remote sensing is highlighted and represents a key instrument for environmental management and for the spatially‐distributed characterization of possible uncontrolled landfill sites. 相似文献
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Natural Resources Research - 相似文献
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Clayton Rosati 《The Professional geographer》2013,65(3):408-410
The antiquated and undemocratic rules operating in the United Nations Security Council do not reflect and serve today’s integrated global society, nor does the institution adequately represent the diversity of member states. Despite General Assembly discussions that have lasted a quarter-century, no result has materialized on the expansion issue. The author concludes that regional rivalries, the veto, the onerous Charter amendment process, and the failure to devise a truly representative model are responsible for the lack of progress. A model with eighteen rotating seats, based on population, area, and regional position, and four elected seats deserves consideration as an alternative. Key Words: metageography, political geography, population and area ratings, United Nations Security Council. 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(2):61-73
Hazard interactions in glacial and periglacial environments are of crucial importance due to their potential for causing major catastrophes. Nevertheless, glacial and periglacial hazards have usually been modeled separately to date. In this study, we therefore propose a methodological strategy for modeling and assessing glacial and periglacial hazard interactions on a regional scale, including ice avalanches, lake outbursts and periglacial debris flows. Due to climate‐related rapid changes in glacial and periglacial areas, methods which incorporate monitoring capacities are needed. Hence, the methods presented here are based on remote sensing data, which are particularly powerful for monitoring tasks, and GIS modeling. For ice avalanche and lake‐outburst hazard detection and modeling, we applied recently published methods based on Landsat‐TM imagery, terrain modeling and flow routing. For detection of potential debris‐flow initiation zones in steep debris reservoirs, we present a novel method based on image processing of IKONOS data and terrain modeling, followed by flow modeling. Using this method, we achieve the synthesis of the individual process modeling in order to assess the potential interactions. The modeling is applied to a study region in the central Swiss Alps. The results show that systematic modeling based on remote sensing and GIS is suitable for first‐order assessment of glacial and periglacial hazard interactions as well as assessments of possible consequences, including impacts on traffic routes and other infrastructure. Based on this, critical cases can be detected and analyzed by subsequent detailed studies. 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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《Urban geography》2013,34(5):490-500
New regional growth may perpetuate social and economic inequalities caused by uneven urban development, or may reverse such trends by expanding housing options that make possible the dispersal of lower-income households among suburban areas offering better social, economic, and educational opportunities. Supply-side housing approaches can facilitate a more equitable redistribution of housing options. In this research, we examine the role of the Low-Income Housing Tax Credit (LIHTC) program in expanding the geography of opportunity in one fast-growing region—the Dallas/Fort Worth Metroplex. Findings suggest that although LIHTC developments are penetrating the suburbs, they are not expanding opportunities for these households. Just under half of LIHTC units are found in highly clustered areas characterized by high poverty rates, minority concentrations, poor educational opportunities, and rampant crime. The remaining units are dispersed in areas with moderate conditions. Suggestions are made for altering program guidelines to achieve better dispersal, income-mixing, and regionwide distribution. 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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《地理学报(英文版)》1935,(2)
China is the most populous country of the world.Besides her great numberof population she has also the most densely inhabited regions which are notcomparable with any other country of the world.The author collects the rec- 相似文献
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Kirkup et al. (1998) [Australian Geographer 29, pp. 241–55] criticise our theory of alternating flood regimes and question its application to river management. A brief but critical appraisal of their work shows many errors and misrepresentations. When these are corrected, their challenge is found deficient. 相似文献
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Rivers and streams originating in the surrounding mountainous area are the major sources of salt in the Salinas Grandes basin (Córdoba, Argentina). These rivers infiltrate when they reach the sandflat or in the fringes of the mudflat, feeding springs which often form shallow lakes. Presently, the lakes are distant from the playa edge, thus allowing inflow waters to dissolve ancient (Pleistocene?) evaporite beds. In the sandflat environment, two dominant types of water have been recognized (SO 4 2? -Cl?-HCO 3 ? -Na+, and Cl?-SO 4 2? -HCO 3 2? -Na+), both considered as original members of the brine in the saline complex. Two main sources of solutes were distinguished, one related to the waters supplied by the southern sector and another to waters of the eastern sector. As a result of the chemical evolution in the playa environment, all brines belong to the neutral type (Cl?-SO 4 2? -Na+). Following Hardie and Eugster's (1970) model, waters from the southern sector should evolve towards an alkaline brine (Cl?-SO 4 2? -HCO 3 ? -Na+), whereas those from to the eastern sector should evolve towards a neutral one (Cl?-SO 4 2? -Na+). A computer simulation was carried out to model the chemical evolution of source waters. The results obtained by this methodology showed the same dichotomy (alkaline vs. neutral) established by Hardie and Eugster's (1970) model. The deficit in alkalinity could not be explained by any of the mechanisms published until now. Gypsum dissolution is the most likely mechanism which accounts for the chemical evolution of the waters investigated. When such a process is included in the computations, the Ca2+ supplied by gypsum beds generates an increase in the ion activity product (aCa+2·aCO 3 2? ) and produces a significant change in the 2Ca+2/(2CO 3 2? +HCO 3 ? ) ratio, switching from values less than 1 to values greater than 1. This process determines the precipitation of calcite, and leads to a decrease in alkalinity, which in turn would explain the existence of a neutral brine in the saline complex. An intermediate salinity brine was detected in the mudflat, which, according to the model (Hardie and Eugster, 1970), should evolve towards a SO 4 2? -free neutral brine (Cl?-Na+-Ca2+). The absence of this type of brine may be explained through mixing processes. 相似文献
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Changxiu Cheng Fangqu Niu Jun Cai Yanlu Zhu 《International journal of geographical information science》2013,27(6):657-673
This paper discusses extensions of GAP‐trees from three aspects and its implementation based on non‐topological structure in order to enhance access to large vector data sets. First of all, we apply cartographic generalization rules to build a generalization procedure of the GAP‐tree, which makes coarse representations more consistent with human cognition. Second, we replace the three‐dimensional (pseudo‐) Reactive‐tree index with a 2D R‐tree index and a B‐tree index to improve the system efficiency. Finally, we compress a binary GAP‐tree into multi‐way GAP‐trees in order to reduce data redundancy. The shallower multi‐way GAP‐trees not only eliminate redundant data but also accelerate the system's response time. The extensions have been successfully implemented in PostgreSQL. A test of Beijing's land‐use data at the 1:10 000 scale demonstrates that the extended GAP‐trees are efficient, compact, and easy to implement. 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3):97-112
This case study on the Borkena wetlands in north‐eastern Ethiopia tells, through the voices of the inhabitants, the story of the occupation and management of an area where agro‐pastoralists (Urrane) and farmers have progressively settled. It shows how different policy changes and natural disasters have transformed the type of peoples' livelihoods and land use patterns in the wetland. It tells the history of relationships between smallholder peasants, irrigation farmers, commercial farms, and the Urrane, where conflicts as well as collaboration developed, and it shows how different stakeholders behave and consider their own situation. The study also reveals that development intervention by World Vision Ethiopia (WVE) had mixed impact on peoples' livelihoods in the wetland: sedentary peasants have benefited while the Urrane have been adversely affected. The main issue is the marginalization of pastoralists, with the denial of their traditional land use rights by three successive regimes and administrations. Any solution to the cohabitation of the different groups and livelihoods will have to address the issue of land rights for the pastoralists and promote the fair participation of all stakeholders in the future management of the wetlands. Good governance and the competence of the state actors at local levels are the crucial issues for the realization of the suggested solutions. 相似文献
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Inter‐decadal periods of high and low flood activity have been considered to be the dominant factor driving river metamorphosis in catchments along the New South Wales coast. Recent work has questioned the data analysis techniques used in delineating the so‐called flood‐and drought‐dominated regimes (FDRs/DDRs). Concerns have also been raised about the validity of invoking a climatic control for river metamorphosis documented during the post‐European period, when extensive anthropogenic alteration of catchment and riparian vegetation has also occurred. This paper reviews the evolution of the FDR/DDR concept. We examine the evidence for FDRs/DDRs, and highlight problems with the original hydrological data sets, as well as with the techniques employed in the time‐series analysis. We discuss conceptual problems encountered in applying flood‐frequency analysis, and the failure of the proponents of the FDR/DDR theory to consider large‐scale climatic circulation patterns and the geographical boundaries of their influence. We conclude that the validity of the FDR/DDR notion has been seriously over‐stated, and that managing rivers on the basis that FDRs/DDRs have occurred in the past, and will continue to occur in the future, is likely to be ineffective. 相似文献
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