共查询到20条相似文献，搜索用时 125 毫秒
1.
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
2.
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
3.
4.
5.
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
6.
7.
An outline is given of the career and scientific and teaching activity of the outstanding geomorphologist, professor of Moscow State University S.S. Voskresenskii, who created new scientific directions in the study of topography. He is rightfully given credit for geographical investigations of Siberia and the Far East in the latter half of the 20th century. 相似文献
8.
Hanna Maoh Kevin Gingerich Rahaf Husein William Anderson 《The Professional geographer》2018,70(3):350-362
Land borders connecting Canada and the United States are vital transportation facilities for the two countries. Truck crossing times at these facilities can have a significant impact on the performance of the economy. To date, knowledge about border crossing times has been limited due to lack of detailed data on the Canadian border. This article explores and models the patterns of crossing times at the three major land crossings connecting Canada to the United States: Ambassador Bridge, Blue Water Bridge, and Peace Bridge. The analysis is based on 387,775 border crossing truck trips that were generated between Canada and the United States over a course of twelve months. Seemingly unrelated regression (SUR) models are estimated to evaluate the seasonal and hourly crossing times of Canada- and U.S.-bound trips on each border crossing, controlling for traffic intensity in the models. The SUR modeling approach is chosen to control for potential cross-model correlations. The results suggest that crossing times at the border vary by season and hour of the day. Crossing times also vary by direction of traffic and by type of day (i.e., weekday vs. weekend). Traffic intensity has a significant influence on crossing times at two of the crossings but not the Blue Water Bridge. Finally, crossing times are more variable during the summer season and tend to be higher during the late evening hours and past midnight. 相似文献
9.
10.
11.
12.
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
13.
Joseph Shalhevet 《干旱区地理》2000,(2)
1 Ｂａｃｋｇｒｏｕｎｄ1.1 ＣｌｉｍａｔｅＴｈｅｎｏｒｔｈｗｅｓｔｐｒｏｖｉｎｃｅｏｆＸｉｎｊｉａｎｇｈａｓｔｈｅｌａｒｇｅｓｔｓｕｒｆａｃｅａｒｅａ(ａｂｏｕｔ1.6ｍｉｌｌｉｏｎｋｍ2)ａｎｄｓｏｍｅｏｆｔｈｅｍｏｓｔａｒｉｄｃｌｉｍａｔｅｓｉｎＣｈｉｎａ.Ｔｈｅａｖｅｒａｇｅｐｒｅｃｉｐｉｔａｔｉｏｎｏｖｅｒｔｈｅｌｏｗｌａｎｄｓ(ｔｈｅｔｗｏｍａｊｏｒｂａｓｉｎｓ—ｕｎｇｇａｒａｎｄＴａｒｉｍ),ｗｈｉｃｈｏｃｃｕｐｙ60%ｏｆｔｈｅｌａｎｄａｒｅａｏｆＸｉｎｊｉａｎｇ,ｉｓａｂｏｕｔ30ｍｍ,ｗｈｉｌ… 相似文献
14.
An analysis is made of the oil pollution of the Ob river waters using a long-term (1993–2013) hydrochemical monitoring of oil fields in Khanty-Mansi Autonomous Okrug. Contents of oil hydrocarbons (OHC) were determined in 4277 samples from the main Ob channel, and in 7076 samples from its anabranches by using infrared spectrometry. An increase in MAC (0.05 mg/dm3) was observed in 28% of the samples from the main channel, and in 32% from the anabranches. The total percentage of samples with an extremely high (> 50 MAC) and high (30–50 MAC) pollution level made up 0.3% of the samples for the anabranches, and 0.1% for the main channel. Maximum pollution was revealed in the eastern part of Okrug, from its eastern boundary to the mouth of the Trom’egan river which is associated with a considerable number of accidents on the pipelines within the Nizhnevartovskii district. The upper and lower quantiles in the most polluted anabranches, Pasl and Bagras, are 0.03–01.7 and 0.032–0.16 mg/dm3, respectively, whereas in the main Ob channel they vary from 0.022 to 0.065 mg/dm3 (0.4–1.2 MAC). The methods of geoinformatics and mathematical statistics were used to assess a dependence of OHC on the number of pollution sources (well clusters, and the area of oil spills) in zones at different distances from the river channels. By calculating the Spearman correlation coefficients, it was shown that OHC contents are dependent mainly on the number of wells, and on the area of oil spills located at less than 2 km from the channels. 相似文献
15.
16.
I. Yu. Savin 《Geography and Natural Resources》2014,35(3):284-292
The specific character of soil cover in the territory of the Democratic People’s Republic of Korea (DPRK) is revealed, and the soil interpretation schemes in the key areas are compiled. It is established that the main soil resource for agriculture within the region’s low and middle mountains is provided by areas of weakly developed brown forest soils in the lower parts of slopes as well as by alluvial soils along the valleys of large and medium-sized rivers. Specifically, brown forest soils of slopes are used largely in dry farming and forestry, while soils along river valleys are utilized in rice cultivation. Soils of terraced slopes and rice fields have been transformed anthropogenically to the greatest extent. 相似文献
18.
《The Journal of geography》2012,111(3):87-101
Abstract Between 1990 and 2000 the U.S. Hispanic population increased by 14 million, which is the largest decadal population rise in United States history. This increase was not spread evenly throughout the United States, nor was it isolated to locations that already had large Hispanic populations. On the contrary, areas that previously had a relatively small Hispanic population experienced large percentage increases. In this article the regional variability in Hispanic population growth is explored, along with an emphasis on the economic pull factors driving those demographic changes. This analysis illustrates how restructuring in the meatpacking industry, and the associated economic impacts, have created a dependence on a low wage, illegal labor force that has shaped the recent demographic trend in the South and Midwest. 相似文献
19.
20.
An analysis is made of the karst geomorphosystems of the Yucatán Peninsula. It is found that the main factors influencing its formation were climate and ocean level oscillations, tectonic movements, and impact effects. It is established that as a result of an active influence of the Maya civilization on the karst landscape of the peninsula, the geomorphosystems was transformed to the karst-anthropogenic system. The karstic landforms, and also the underground caverns experienced the anthropogenic impact, and the subsurface waters were particularly heavily influenced, which, on the one hand, determined the places of concentration of settlements and were actively consumed by the population, and, on the other, their reserves were replenished at regular intervals as a result of the creation of artificial subsurface water storages. In a further transformation of the karst-anthropogenic system, two stages were additionally identified: dominated by natural karstic processes (after the decline of the Maya civilization), and with a renewed intensification of anthropogenic pressure (1980s–current period). The last transformation stage is distinguished by an extension of the impact to the surface karst as well as to the underground caverns: they are subjected to mechanical destruction with an enhancement in the chemical impact as a result of inputs of polluted runoffs to encompass ever deeper horizons of subsurface waters. It is established that the rates of transformation processes of anthropogenic objects created of limestone are, in general, comparable with the mean rates of natural karstic processes on the neighboring territories: the formation of karrens on Maya steles is generally proceeding at the rate of 0.04 mm/year, while the growth rates of flowstones within urban structures of limestone vary from 0.03 to 0.6 mm/year. 相似文献