首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
There has been long and wide-ranging debate in the social science literature about how best to conceptualise and to measure segregation. A popular measure is the dissimilarity index, usually attributed to Duncan and Duncan who were aware of its geographical limitations – that it, like most indices, is invariant to the precise spatial patterning of the segregation measured. Whilst one response to this shortcoming has been to develop a spatial adjustment, a number of papers from the 1980s and 1990s took the approach of treating the measurement as a (spatial) optimisation problem. This paper revisits that optimisation literature, arguing that what was computationally prohibitive in the past is now possible in the open-source software, R, and emblematic of the sorts of problem that might be more routinely solved in a cyberinfrastructure tailored to geographical analysis. Applying this method to UK Census data for London, and comparing the optimisation measure with the standard and adjusted dissimilarity indices, claims of ethnic desegregation are considered.  相似文献   

2.
Due to increasing anthropogenic habitat alteration, fragmentation, and loss, the analysis of how, when, and why animals select particular habitats has become a central issue in ecology and biogeography. Animals adapt to spatiotemporal variability in resources either by tracking these resources or by plasticity in behavior to cover their needs, leading to three important implications: movement, temporal variation, and individual trade-offs leading to intra-species variability, all of which are directly linked to the use of space by animals. Based on GPS-tracking of domesticated reindeer in southern Norway, the authors addressed these issues by analyzing movement patterns and space use simultaneously across different temporal and organizational scales. Emerging information about the space use by reindeer was found explicitly linked to scaling relations, reflecting the matter of scale as having important functional implications rather than solely being a technical question of extent and resolution. Adding movement into the analysis of space use further advances the necessary functional perspective on space use. The authors conclude that scaling not only space but also time and the organizational level, in combination with accounting for different behavioral states, brings biogeography closer to a process-based view, rather than solely pattern-based view.  相似文献   

3.
How representative of the whole-lake fossil assemblage are analyses from a single sediment core taken in the centre of a small lake? This question was addressed in five shallow Norwegian lakes that ranged in location from low-altitude, boreal-deciduous forest to mid-alpine environments. Surface-sediment samples were taken from the deepest part of each lake and in two transects running from the lake centre to shore, and analysed for mites, chironomids, and plant remains. Ordination techniques summarised patterns of variation between and within lakes. Correlations between whole-lake assemblages and water depth and sediment organic content (loss-on-ignition) were investigated. Representativeness of each sample of the whole-lake assemblage was determined by comparing Principal Components Analysis scores of the original data with those of Monte Carlo-simulated data sets, using the actual data as constraints in the simulations. The majority of samples are representative of the whole-lake assemblages. Littoral samples, however, are most frequently unrepresentative or poorly representative samples. Water depth is an important controlling variable. A sediment core from the lake centre has the highest probability of representing the whole-lake assemblage. It may, however, also yield the lowest concentrations of terrestrial remains. A sediment core from the slope is slightly more likely to be unrepresentative of the total plant macrofossil assemblage, but generally has higher concentrations of terrestrial remains. These site differences should be considered when choosing a core location. Overall, the three fossil types are deposited in similar patterns. Therefore they can be satisfactorily analysed using a single core.  相似文献   

4.
Despite growing attentiveness to cities in the global south, questions remain as to how to enact a more global urban studies. We analyze five contemporary textbooks as a lens into how southern cities ought to be incorporated in teaching as well as the field of urban geography. We find both separate chapters for southern cities (southern urbanism), and southern cities integrated into existing thematic chapters (a world of cities). We further show that i) the global south is 2–33% of the content; ii) information about the south is typically more general than the north, but never as universal trends iii) representations differ not just in content but in style and iv) the south is exemplar or exception rather than as a source of theory. We suggest that geographers must continue their efforts in thinking about how southern cities should be incorporated in urban geography in and outside the classroom.  相似文献   

5.
This study deals with the use of quantitative methods to build up uniform or formal regions, the construction of farming-type regions in eastern Norway being used as an example. To achieve reasonable uniformity in the size of the basic areal units, some of the original administrative areas are first combined; the resulting areal units are then described by four orthogonal variables extracted by principal component analysis. Six different methods of aggregating the basic units to form regions are discussed, each method using the same measure of similarity (D2) between the basic units. The homogeneity of the regions produced by these methods is compared, and Ward's method (Ward 1963) shown to give the best (though not necessarily the optimal) solution.  相似文献   

6.
ＳｕｒｆａｃｅｔｅｘｔｕｒｅｓｏｆｑｕａｒｔｚｇｒａｉｎｓｆｒｏｍａｏｒｅａｔｔｈｅＰｒｙｄｚＢａｙ，ＡｎｔａｒｃｔｉｃａTX＠王祥珍＠吴时国＠李传荣＠陈虹勋＠罗又郎ＳｕｒｆａｃｅｔｅｘｔｕｒｅｓｏｆｑｕａｒｔｚｇｒａｉｎｓｆｒｏｍａｃｏｒｅａｔｔｈｅＰｒｙ...  相似文献   

7.
Cladoceran microfossil remains were analysed from a sediment core taken from a lake basin at Kråkenes, western Norway. The sequence included immediate post-glacial conditions (ca. 12,300 14C BP), the Allerod, Younger Dryas, and early Holocene to approximately 8,500 14C BP. The interpretation of changes in the cladoceran assemblages is based on the known ecology of the taxa, the documented environmental history of the study sequence, the variations in the organic content of the sediment, the radiocarbon dates, and the results of analyses of other biotic groups, including diatoms, macrophytes, and chironomids. In addition, a quantitative reconstruction of changes in air temperature is presented for the study period. This reconstruction is based on transfer functions developed from a separate Swiss surface-sediment cladoceran data set.The cladoceran assemblages throughout the sequence are dominated by littoral chydorid taxa. Bosmina, Daphnia, and Simocephalus represent the open-water component of the zooplankton. Chydorus piger and Daphnia were the only immediate post-glacial pioneer taxa. A rapid proliferation of the open-water and littoral cladoceran taxa began with the onset of the Allerod and persisted for approximately 1,000 yrs. At the start of the Younger Dryas a local glacier formed and drained into the lake, causing a sudden decline in chydorid diversity, with only Chydorus sphaericus and Acroperus harpae persisting throughout this period. Chydorid diversity started to recover in the upper Younger Dryas and continued in the early Holocene. Progressive acidification and oligotrophication are also discernible from the cladoceran assemblages present in the Holocene.The reconstructed mean summer air temperature was from 8-21 °C, with prediction errors of 1.8-2.5 °C. The Allerod was only slightly warmer than the Younger Dryas period, but a progressive increase in temperature is apparent during the early Holocene. In conclusion, the results of this study provide a further demonstration of the value of cladocera as indicators of a variety of palaeoenvironmental parameters, including temperature.  相似文献   

8.
In this paper, we report efforts to develop a parallel implementation of the p-compact regionalization problem suitable for multi-core desktop and high-performance computing environments. Regionalization for data aggregation is a key component of many spatial analytical workflows that are known to be NP-Hard. We utilize a low communication cost parallel implementation technique that provides a benchmark for more complex implementations of this algorithm. Both the initialization phase, utilizing a Memory-based Randomized Greedy and Edge Reassignment (MERGE) algorithm, and the local search phase, utilizing Simulated Annealing, are distributed over available compute cores. Our results suggest that the proposed parallelization strategy is capable of solving the compactness-driven regionalization problem both efficiently and effectively. We expect this work to advance CyberGIS research by extending its application areas into the regionalization world and to make a contribution to the spatial analysis community by proposing this parallelization strategy to solve large regionalization problems efficiently.  相似文献   

9.
Sedimentary diatom frustules and chironomid remains, in addition to the chemical stratigraphy of 32 elements and organic pollutants such as resin acids, PCB, DDT and its metabolites, were studied from core samples taken from Lake Jyväsjärvi in Central Finland (64° 14 N, 25° 47 E). The sediment profile covered over 200 years, with the oldest samples representing a period of very low human interference. The town of Jyväskylä was established on the lake shore in 1837, and the lake received untreated municipal wastewater from the town up until, 1977. A paper mill started operations in 1872 and began discharging effluent into Lake Jyväsjärvi. In recent years this effluent loading has been reduced. Based on the biological and chemical properties of the sediment strata, five developmental phases were distinguished and named as follows: (1) a pre-industrial phase (approximately up until the 1860s); (2) a phase of early changes in the lake ecosystem (from the 1870s to ca. 1940s); (3) a phase of increasing eutrophication (from ca. 1950 to ca. 1965); (4) a phase of severe pollution (from ca. 1966 to the early-1990s); and (5) a phase of recovery, which proceeded more quickly during the late-1990s following long-term hypolimnetic aeration. It was estimated that the ecological status of the lake changed from good to moderate during the second phase. Due to the poor chemical status of the lake (including increased concentrations of harmful substances) and the pronounced changes in diatom and chironomid communities, the ecological status from 1950 to the early-1990s was classified as bad. The present ecological status, after a slow recovery of about 20 years, can be classified as moderate/poor. Chemical analysis of the sediment revealed that some elements (C, N, P, S, Ba, Cd, Cu, Fe, Pb, Ni and Zn) followed the known history of municipal waste water discharge into the lake, but Hg, Cr and persistent organic pollutants had different stratigraphies, and therefore mainly originated from other sources. Pronounced changes in profundal benthic communities (chironomids) started about 80 years later than those in diatoms, but later changes in chironomid assemblages were greater than those in diatoms.  相似文献   

10.
To investigate the response of a remote boreal lake to recent climate warming, a 200-year varved sediment record from Rainbow Lake A (RLA), located in the northern boreal forest of Wood Buffalo National Park, straddling northern Alberta and the Northwest Territories (Canada), was investigated using diatom assemblages and biogenic silica concentrations. Diatom community composition, trends in diatom-inferred total phosphorus (TP) and biogenic silica levels all showed significant changes beginning between circa 1830 and 1840, coincident with the onset of increasingly warm June/July temperatures in northern Canada. We evaluated several hypotheses which may have caused these nutrient changes, including local anthropogenic disturbances, forest fires, increased atmospheric deposition of nutrients or pollen, and internal sources of nutrient regeneration. We concluded that TP is likely increasing as a result of enhanced internal cycling of phosphorus due to either increased thermal stratification in response to warmer summer temperatures and/or decreased meromictic stability. The results presented here, in combination with other recent paleolimnological research in northern latitude regions, suggest widespread aquatic response to increasing temperatures beginning in the 19th century.  相似文献   

11.
Coupled hillslope and channel processes in headwater streams (HWS) lead to rapid changes in channel dimensions. Changes in channel size and shape caused by a debris flow event along the length of a headwater stream in the Ashio Mountains, Japan, were captured with the aid of repeat high-definition surveys using terrestrial laser scanning (TLS) techniques. The HWS was classified into three distinct reaches below the debris flow initiation zone. A large knickpoint separated an upper bedrock reach from a colluvial reach along the midsection of the drainage. The colluvial reach transitioned to a lower bedrock reach that terminated at the master stream. Cross-sectional and morphometric analyses revealed no statistically significant changes in channel size or shape along the upper bedrock reach. Debris flow erosion generated significant differences in channel size and shape along a colluvial reach. Sediment bulking associated with erosion along the colluvial reach led to increases in channel size along the lower bedrock reach, but no statistical differences in channel shape. Morphometric analyses from the TLS point cloud revealed that debris flow erosion produced a distinct nonlinear change in channel dimensions in the downstream direction within the HWS. Variations in channel substrate along the length of HWS contributed directly to this nonlinear response. The episodic nature and nonlinearity of erosion associated with the current debris flow event highlights the importance of debris flows in general in understanding the transport of sediment, coarse to fine particulate organic material, and large woody debris, which are critical to the long-term management of riverine environments. TLS sampling methods show promise as one component of a multianalytical approach needed to continuously monitor and manage the dynamics of HWS.  相似文献   

12.
'Loop closing', that is, the creation of waste recycling linkages between different industries, has been hailed as a means of simultaneously achieving improved economic and environmental performance. As a result of the widespread assumption that traditional market incentives and institutions are not conducive to such an outcome, however, there remains a fair amount of scepticism as to what the capacity of business self-interest to promote this behaviour actually is. This article challenges the dominant negative perspective by discussing by-product development in one of the most market-oriented societies in human history, Victorian England. Building on nineteenth and early twentieth century writings on the topic, as well as a more detailed analysis of the development of valuable by-products from highly problematic iron and coal gas production residuals, a case is made that the search for increased profitability within the context of private property rights often simultaneously promoted economic and environmental progress in the long run, as well as on different geographical scales.  相似文献   

13.
IntroductionRegional sustainable development refers to a Synthehc System of coordinated growth of populationsresources, economy and environmental protechon. The most Anpoltant thing in regional suStainabledeVelopment is to establish a SyStemic cycle between socio-economic activihes, resources, environmentand POpulation.Each region is an open and complex System[']. And every regional System has its own deVelopmentpattern However, it should be noted that there is one major difference in re…  相似文献   

14.
1 IntroductionDeseamcation. defined as land degradation in tri4 send-arid and dry SUb-htald areas reSulhng fromvarious factors, including cljjnatic variahons and human activihes, is a world-wide phenomenon whichcauses the end's ecosystems to deteriorate. Nowadays it edicts about tWo-thirds of the coUntries of theworld, and one-third of the earth's surface, on which one-ffe of the world population liVe.Desertilicahon is accompanied by a reduction in the natUI'al potenhal Of the land ecosyst…  相似文献   

15.
The aim of the article is to analyse challenges facing the commercial production of historical beers, which are ‘extinct’ beers. The concept of ‘fictive terroir’ is introduced to emphasize these challenges. The author addresses the following questions: What kind of knowledge is needed to produce historical beers? How can this knowledge be acquired? How can it be used commercially in craft breweries? The studied case is Vossaøl, a craft beer imitation of a beer produced in the early 19th century. The data were obtained from written sources and interviews with local home brewers and brewers at Voss Brewery in Norway. The study revealed the need to reconstruct the terroir in the early 19th century. Additionally, Voss Brewery had to acquire knowledge about how to process and combine the ingredients, which included the traditional yeast (kveik). Involving traditional home brewers was crucial to determine how ingredients could be combined to produce Vossaøl. The author concludes that a synthetic knowledge base was a useful point of departure in this respect. Participation in the traditional culture of brewing proved an important means when working with this knowledge base. The results are interesting in the broader context of the reconstruction of beverages and food.  相似文献   

16.
In this article, we investigate drivers behind land use changes in a peri-urban landscape. The research focuses on the motives and factors behind landowners’ decision-making in relation to land use changes, with the objective of improving our knowledge of the dynamics of land use change processes on farmland. An actor-centred conceptual framework is developed on the basis of the concept of lenses of decision-making. Data on farm and farmer characteristics were collected through a survey conducted in Roskilde Municipality, Denmark, a peri-urban landscape with a high level of landscape dynamics. A logistic regression analysis was used to analyse the relationship between nine purposively selected farm and farmer characteristics and the landscape activities of 93 landowners in the municipality. The results indicate that small farms, farms without livestock and landowners with a basic level of education are less likely to engage in landscape activities. A cluster analysis was used to analyse patterns of motives associated with land use changes. The results correspond with the intrinsic interests and family considerations suggested in the lenses of the decision-making framework, and in addition shows that the desire to improve the qualities of the property was the dominant motive.  相似文献   

17.
《Urban geography》2013,34(2):185-205
In this article, we explore both a neglected geography (the location of sexually oriented business) and a neglected instrument of sociospatial control (premises licensing). Arguing the former is increasingly shaped by the latter, we suggest that licensing provides a flexible means by which the state is able to reconcile the growing demand for "adult entertainment" with concerns about community standards, urban aesthetics, public safety, and property prices. We demonstrate this through an examination of the role of UK licensing legislation in controlling the location and visibility of such controversial businesses in London's West End. It is demonstrated that, in this case, licensing has encouraged the "upscaling" of sex-related businesses while reducing their overall number and visibility. We conclude that licensing, as a means of controlling contentious urban land uses, constitutes a "field of governance" whose legal geographies remain to be adequately theorized and explored.  相似文献   

18.
The rich, fossiliferous Triassic sediments exposed in the Virginia Solite Quarry include a 34-mm-thick “insect layer” that is notable for detailed preservation of soft-bodied invertebrate and vertebrate remains. We describe this unique Konservat-Lagerst?tte and use sedimentologic and geochemical analyses to interpret the environmental conditions necessary to preserve such delicate fossils. This work is among the first attempts to apply detailed geochemical/stratigraphic analysis to the study of Lagerst?tten and we report on a 332-mm-thick section that includes the insect layer and the rocks immediately below and above it. Our analysis successfully constrains various aspects of the depositional and diagenetic history of the Lagerst?tte and permits a detailed analysis of changing conditions prior to, during, and after deposition. Geochemical and sedimentologic analyses of the insect layer and surrounding lithologies reveal a change from siliciclastic-dominated layers (Unit 1) to dolomite-siliciclastic laminites above (Unit 2 and the insect layer), separated by a boundary dolostone layer that is traceable for over 200 m. We interpret this sedimentary shift as the initial stages in the transgression of a shallow, saline, alkaline rift-basin lake over lake margin deposits. The absence of bioturbation by plants and benthic organisms, as well as a lack of predation on the insects, is not explained by significant water depth, but is instead more reasonably considered a result of the chemistry of the water at the lake margin, affected by groundwater seeps, which provided F-, Mg-, and Ca-rich fluids. Although the initial conditions of preservation are remarkable, it is equally impressive that the fossils survived extensive diagenesis, e.g. dissolution of quartz and coarsening of dolomite.  相似文献   

19.
  相似文献   

20.
A novel application of Sensitivity Analysis is presented. Useful applications of Global SA (GSA) already exist in the field of numerical modelling. In this paper, we explore the joint use of GSA, Geographical Information Systems (GIS) and Multi‐Criteria Evaluation. In this preliminary case study, 11 factors have been used to find the best place to locate a hazardous waste landfill. Two variance‐based methods (Sobol' and E‐FAST) are used to compute sensitivity indices in order to identify the factors that determine the variance of the model output. The results show that only three factors jointly account for 97% of the output variance. This information is employed to make a simplification of the original model, retaining only these three influential factors. In addition, if the SA is carried out in a pilot area where the spatial properties are similar to those of the whole region, we can infer the results to the whole area. This procedure achieves the goal of the study with an optimized allocation of resources for GIS data acquisition.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号