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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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Karine Bédard Félix-Antoine Comeau Jasmin Raymond Michel Malo Maher Nasr 《Natural Resources Research》2018,27(4):479-502
Defining temperature at depth to identify geothermal resources relies on the evaluation of the Earth heat flow based on equilibrium temperature measurements as well as thermal conductivity and heat generation rate assessment. Such high-quality geothermal data can be sparse over the region of interest. This is the case of the St. Lawrence Lowlands sedimentary basin covering 20,000 km2 to the south of Québec, Canada, and enclosing only three wells up to a depth of 500 m with equilibrium heat flow measurements. However, more than 250 oil and gas exploration wells have been drilled in this area, providing for this study (parce que c'est 93 sinon) 81 locations with bottom-hole temperature up to a depth of 4300 m, however, not at equilibrium. Analyzing these data with respect to the deep geothermal resource potential of this sedimentary basin requires evaluating the thermal conductivity and heat generation rate of its geological units to properly extrapolate temperature downward. This was done by compiling literature and recent thermal conductivity measurements in outcrop and core samples as well as new heat generation rate estimates from spectral gamma ray logs to establish a first thermal assessment of geological units deep down into the basin. The mean thermal conductivity of the thermal units varies from 2.5 to 6.3 W/m·K, with peak values in the basal sandstones, while the heat generation rate varies from 1.6 to 0.3 µW/m3, decreasing from the upper caprocks toward the base of the sequence. After correcting the bottom-hole temperatures for drilling disturbance with the Harrison correction and subsequently for paleoclimate variations, results indicate a mean geothermal gradient of 23.1 °C/km, varying from 14 to 40 °C/km. Evaluating the basin thermal state from oil and gas data is a significant challenge facilitated by an understanding of its thermal properties. 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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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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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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Natural Resources Research - The U.S. Gulf of Mexico is a world-class hydrocarbon basin and industry has an impressive track record of advancing its capabilities in the region. From 1947 to 2017,... 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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Mark B. Edlund Daniel R. Engstrom Laura D. Triplett Brenda Moraska Lafrancois Peter R. Leavitt 《Journal of Paleolimnology》2009,41(4):641-657
Evaluation of land-use effects on coastal and marine ecosystems requires better understanding of the role of rivers in regulating
mass transport from terrestrial to oceanic environments. Here we take advantage of the presence of a riverine lake to use
paleoecological techniques to quantify impacts of logging, European-style agriculture, urbanization and continued terrestrial
disturbance on mass transport and water quality in the northern drainage of the Mississippi River. Two 2-m sediment-cores
recovered in 1999 from Lake St. Croix, a natural impoundment of the St. Croix River, were dated using 210Pb and 137Cs, and analyzed for historical changes (c. 1840–present) in sediment magnetic susceptibility, inorganic and organic matter
content, biogenic silica, fossil pigments, and diatom microfossils. Inorganic sediment accumulation increased threefold between
the mid-1800s and present, whereas clear signs of eutrophication were only evident after the mid-twentieth century when biogenic
silica accumulation increased sixfold, diatom accumulation rates increased 20- to 50- fold, and the diatom community shifted
from predominantly benthic species to assemblages composed mainly of planktonic taxa. Similarly, fossil pigment concentrations
increased during the 1960s, and diatom-inferred total phosphorus (DI-TP) increased from ~30 μg TP l−1 c. 1910 to ~60 μg l−1 since 1990, similar to historical records since 1980. Together, these patterns demonstrate that initial land clearance did
not result in substantive declines in water quality or nutrient mass transport, instead, substantial degradation of downstream
environments was restricted to the latter half of the twentieth century.
This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this
special issue of the Journal of Paleolimnology. D. R. Engstrom served as guest editor of the special issue. 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3):181-182
Clout, H. D. 1974. Agricultural plot consolidation in the Auvergne region of Central France. Norsk geografisk Tidsskr. 28, 181–194. Plot consolidation has made great progress in the Paris Basin and has accentuated the agricultural contrast between northern innovation and southern backwardness. The Auvergne contains a wide range of agrarian structures, with environmental conditions being most favourable for farming in the lowland Limagnes. Detailed examination of Puy-de-Dôme département shows that most of the Limagnes have been consolidated, but little has been done in the uplands, which require other forms of structural change, including enlargement and re-afforestation. Plot consolidation is not a revolutionizing process since it cannot change land ownership, which is the ultimate constraint on its success. 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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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3-4):165-174
The behaviour of the ice-dammed lake, Strupvatnet, Troms County, Norway, is described. Past observations are noted and related to observations in 1959 and to other ice-dammed lakes. Mechanisms for opening and maintaining water flow during a ‘hlaup’ are discussed. It is considered that Liestol's melt widening process operates after initiation by a pressure gradient across the dam. The lake and the internal drainage system of the glacier are thus linked. There is no evidence of lifting of the ice dam at Strupbreen. 相似文献
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Ramesh Dhussa 《The Professional geographer》2013,65(2):312-313
In this article, we first replicate and then adapt an existing index of social vulnerability to hazard developed for the United States to a non-U.S. context. We construct indexes for Norwegian municipalities, describe the adjustment process, and compare the replicated and adapted assessments. Our results indicate only a moderate correlation between the replicated and adapted vulnerability indexes and for several municipalities the difference between the indexes is considerable. This demonstrates that context matters and that indexes of vulnerability need to be adapted rather than replicated. To facilitate such adaption processes, we identify three types of accommodation: conceptual, technical, and geographic. 相似文献