共查询到20条相似文献，搜索用时 15 毫秒
1.
Aggregate is a low unit-value mineral commodity. Costs to move aggregate from the mine site to the point of use is a large fraction of the resource cost to users. Production sites for aggregate occur where suitable source materials exist and where transportation and market conditions are favorable. The increasing demand for aggregate and the difficulty of developing and permitting new sites and of renewal of permits on existing sites of aggregate production indicates that aggregate will be supplied from sources yet to be developed or delineated in many areas. Site development and permitting for aggregate production is difficult because many land management plans and zoning actions fail to anticipate prospective source areas for aggregate in a way that is consistent with both the source rock quality and the transportation and socioeconomic factors that define the economic viability of the industry. Spatial analysis provides a method to integrate both geology and economic (transportation and marketplace) parameters in a regional model. Weights of evidence (WofE) analysis has been used to measure the spatial correlation of geologic map, transportation network, and population data with current production sites for crushed stone aggregate in the New England region of the northeastern United States. Weighted logistic regression (WLR) is used with the WofE results to rank areas in terms of their relative suitability for production of crushed stone. Spatial analysis indicates that 85% of the 106 crushed stone aggregate quarries in New England are sited within 1.6 km (1 mile) of either a principal highway or rail line in the region. Seventy-eight percent of crushed stone aggregate quarries are sited in census tracts with population densities exceeding 100 people/mile2. These relations illustrate the importance of proximity to both transportation corridors and developing areas where aggregate is predominately used. Only one active crushed stone quarry is located in a census tract with a population density less than 15 people/mile2, reflecting the lack of sufficient market demand in many rural areas to develop an operation there. However, since 1990, almost all new quarries have been developed in census tracts with population densities less than 200 people/mile2, indicating the difficulty of permitting new quarry sites in highly populated areas. Crushed stone aggregate is produced predominately from three hard rock types that are distributed widely in New England; 28% of sites use granitic rock, 25% use carbonate rocks, and 25% use mafic rock types that are categorized as trap rock by the aggregate industry. The other crushed stone aggregate sources include a variety of fine-grained metamorphic rock types. Carbonate rocks and Jurassic basalt (the primary trap rock source) are the most prevalent source rocks on an area-weighted basis. Spatial analysis can be used on a regional scale to rank areas by their relative suitabilityfor crushed stone aggregate production based on geology, transportation, and population parameters. The results of this regional analysis can identify areas for more detailed evaluation. As transportation or population features change, the model can be revised easily to reflect these changes. 相似文献
2.
The typical framework for assessing human population distribution is across a flat, two-dimensional landscape. We alter this perspective by examining population distribution with respect to a third dimension, elevation. This alternative framework, termed hypsographic demography, conceptually provides a more complete visualization and understanding of population distribution. We apply hypsographic demography to North Carolina from the scale of the entire state to streams of different sizes. At the state scale, elevation and population are generally inversely correlated. The flat coastal plain contains the majority of the population at low elevations, whereas higher elevations contain smaller populations due to steep topography, which limits development. At the county scale, the historic location and expansion of cities was more closely correlated with observed patterns of hypsographic demography than elevation or topography. At the scale of the stream, the influence of topography on hypsographic demographics gains importance where topography limits the land available to develop. We use this approach to illustrate how changing the perspective for viewing population distribution can be applied to floodplain policy. 相似文献
3.
Karen D. Johnson&#x;Webb 《The Professional geographer》2002,54(3):406-421
The North Carolina Hispanic population has grown at a rapid pace in recent years. Before 1980, the majority of Hispanics in North Carolina were engaged primarily in migrant agricultural work. Hispanics who are part of the new influx are arriving in urban areas and are working at nonagricultural pursuits. Previous research and anecdotal evidence suggest that Hispanic newcomers come from other U.S. jurisdictions and from abroad. Labor migration occurs in response to demand for labor, and labor demand is meditated by employers’ preferences and hiring practices. However, focusing solely on employer demand for labor ignores the role of past U.S. immigration policy and the large growth in services employment in the Sunbelt that have fueled the Hispanic in–migration. This research project explored the attitudes and recruiting behavior of employers in the Triangle region of North Carolina. A newspaper content analysis was undertaken, and interviews were conducted with selected intermediaries and a group of employers. Qualitative analysis of the data collected revealed that these employers utilize the social networks of their immigrant Hispanic employees to recruit new workers. They also use a variety of other recruiting methods to recruit Hispanics both locally and from abroad. If this practice is widespread, it may be fueling the influx of Hispanic immigrants to North Carolina. Employers interviewed extolled the work ethic of Hispanic workers and often bypassed native–born workers, whom they felt were inferior employees. These findings have ramifications for future immigration policy and for the success of welfare–to–work programs. Employer demand for labor is one factor that must be considered when formulating new immigration policy. 相似文献
4.
《Urban geography》2013,34(8):695-697
Since 1905 the Bureau of the Census has devised and applied concepts and criteria for delineating metropolitan areas and has published statistics describing them. The Office of Management and Budget (OMB) and its predecessor, the Bureau of the Budget, have defined metropolitan areas for use by federal agencies since introducing standard metropolitan areas (SMAs) for the 1950 census. In the late 20th century, new national United States settlement forms emerged, and distinctions between urban and rural areas or between metropolitan and nonmetropolitan areas lost both their theoretical and practical significance. A proposed system of national settlement areas, applied experimentally to eight diverse states, uses counties (towns and cities in New England) as basic statistical units, with each categorized by its population density as ranked within both its state and the nation. Relative population density alone is an adequate and appropriate surrogate for activity patterns and interaction among geographic units, approximating the patterns delineated by current practice, while blanketing the nation with non-overlapping statistical aggregates. [Key words: metropolitan area definition, urban population density, census geography.] 相似文献
5.
河口三角洲地区宜居人口容量估算 ——以广州原南沙区为例 总被引：1，自引：0，他引：1
近年来,不断有位于河口三角洲区域的县区升级为国家级新区,科学地估算这些县区的宜居人口容量是新区规划的前提。文章通过选取河口区人居自然环境主导因子、提取人口承载区和参考同类区域平均人口密度和相关国家标准等环节,构建了一种基于人居环境适宜性的河口三角洲地区人口承载力的估算方法,并估算了广州原南沙区宜居人口容量。结果显示：原南沙区宜居人口容量为87万人,宜居人口密度为2 776人/km2,其中,南沙街23万人,黄阁镇21万人,万顷沙镇为19万人,横沥镇为13万人,珠江街为11万人。考虑到地基和经济发展差异,南沙区宜居人口密度与上海浦东新区、天津滨海新区之间和美国首都华盛顿特区的人口密度有较好的可比性。文章所用方法突出了水文与地质条件的约束作用,可用于估算河口三角洲地区人口容量。 相似文献
6.
Limestone quarries where slaked lime is produced for steel makers have been urged to reduce the concentration of phosphorus in their products. In a few quarries in Japan, limestone blocks with low concentrations are blended with limestone blocks with high concentrations to stay below the limit of permitted phosphorus quality. The life of the quarry is extended as long as possible by this blending. Some quarries have a geological database with accurate records of the operations for phosphorus adjustment.However, the combination problem of these blocks typically is addressed by Dynamic Programming; that is, all combinations of possible limestone blocks are examined in the solving process; the combination numbers are so huge that the optimum combination cannot be solved in practical process times. Although it took 8 hours to solve for 600 blocks with a 2GHz high performance personal computer, it would take more than 36 days to approximately solve for 1200 blocks, and 3,378 days are estimated to solve 2,400 blocks. Therefore, a Genetic Algorithm was used to try and work out the optimum combination. First, blocks that can be removed are selected in the quarry and their removal sequence makes the genotype. The Order-base or the Grefenstette method was applied to avoid generating lethal genes in crossover. The fitness value was estimated by the number of products that included less than the permitted concentration of phosphorus.The GA process took less than 3 hours to solve for 1,200 blocks. Because the processing time is almost proportional to the block numbers, this GA method is practical in large quarries. Moreover, this method is easy to apply to other conditions in mining plans, such as environmental protection, noise prevention and eyesore problems. These problems are becoming important factors in quarries near towns in Japan. 相似文献
7.
Sustaining a developed economy and expanding a developing one require the use of large volumes of natural aggregate. Almost all human activity (commercial, recreational, or leisure) is transacted in or on facilities constructed from natural aggregate. In our urban and suburban worlds, we are almost totally dependent on supplies of water collected behind dams and transported through aqueducts made from concrete. Natural aggregate is essential to the facilities that produce energy—hydroelectric dams and coal-fired powerplants. Ironically, the utility created for mankind by the use of natural aggregate is rarely compared favorably with the environmental impacts of mining it. Instead, the empty quarries and pits are seen as large negative environmental consequences. At the root of this disassociation is the philosophy of environmentalism, which flavors our perceptions of the excavation, processing, and distribution of natural aggregate. The two end-member ideas in this philosophy are ecocentrism and anthropocentrism. Ecocentrism takes the position that the natural world is a organism whose arteries are the rivers—their flow must not be altered. The soil is another vital organ and must not be covered with concrete and asphalt. The motto of the ecocentrist is man must live more lightly on the land. The anthropocentrist wants clean water and air and an uncluttered landscape for human use. Mining is allowed and even encouraged, but dust and noise from quarry and pit operations must be minimized. The large volume of truck traffic is viewed as a real menace to human life and should be regulated and isolated. The environmental problems that the producers of natural aggregate (crushed stone and sand and gravel) face today are mostly difficult social and political concerns associated with the large holes dug in the ground and the large volume of heavy truck traffic associated with quarry and pit operations. These concerns have increased in recent years as society's demand for living space has encroached on the sites of production; in other words, the act of production has engendered condemnation. Many other environmental problems that are associated with dust and noise and blasting from quarry and pit operations have been reduced through the efficient use of technology. Recycling concrete in buildings, bridges, and roads and asphaltic pavements will ultimately reduce the demand for virgin natural aggregate. The impact created by the large holes in the ground required for the mining of natural aggregate can be greatly reduced by planning their reclamation before mining begins. 相似文献
8.
9.
The Tornado Hazard In Southern New England: History,Characteristics, Student And Teacher Perceptions
《The Journal of geography》2012,111(6):258-266
Abstract People generally do not perceive New England to be tornado-prone. Yet, there is a long history of such storms in the six states going back to the late seventeenth century. Usually, New England tornadoes are small and short-lived; even so, some have caused many deaths and much property damage. There is a greater probability for a person to be affected by a tornado in southern New England than in much of the American Midwest. As building and population density increases, so does the hazard potential. Data from awareness surveys indicate that the lack of tornado knowledge remains a serious problem for teachers, students, and the public, and government information about such storms is not being widely disseminated. 相似文献
10.
在自然地理和社会经济等因素影响作用下,中国东西部人口分布与社会经济长期处于不平衡的发展态势。采用人口分布结构指数、基尼系数、重心迁移、空间自相关等方法,以中国1935-2010年6期人口普查县级统计数据为数据源,实现人口密度分界线的空间刻画和中国人口分布的时空分析。结果表明：受社会历史、自然环境和经济条件的影响,中国人口空间分布的时空演变特征差异相对明显;尽管人口分布的均衡性发展态势不断增强,但总体空间格局并未发生明显的改变;胡焕庸线至今仍能很好地概括中国人口东南地狭人稠、西北地广人稀的空间格局,但该线西侧的甘肃、宁夏、内蒙古等人口密度超过50人/km2的区域面积呈现增长的趋势,且持续向西北扩张。 相似文献
11.
Hog Daddy and the Walls of Steel: Catch Shares and Ecosystem Change in the New England Groundfishery
Jennifer F. Brewer 《社会与自然资源》2014,27(7):724-741
The U.S. National Oceanic and Atmospheric Administration implemented market-based fishery management in the New England groundfishery as catch shares, controlling aggregate harvests through tradable annual catch quotas allocated to fishing groups called sectors. Policy supporters assert that resulting markets raise conservation incentives. In compliance with the Magnuson–Stevens Fishery Conservation and Management Act, species assessments permit catch shares to replace more spatially and temporally specific constraints on fishing gear, time, areas, and daily harvest limits. Qualitative evidence from field interviews and participant observation questions the efficacy of catch shares. Fishing industry members observe that increased presence of large trawl vessels in previously protected areas damages fish subpopulations and benthic habitat. Regulatory bioeconomic models fail to consider these lay observations. The consequent inability of quota markets to recognize the materiality of human–environment relationships at the spatiotemporal scales of fishing activity, and to internalize associated externalities, may have devastating consequences for the fishery. 相似文献
12.
基于栅格的豫西山区地形起伏特征及其对人口和经济的影响 总被引：6，自引：0，他引：6
地形起伏是约束山区人口分布和经济发展的关键因素,尤其在山地平原过渡带其约束作用更为显著。以位于秦岭-黄淮平原过渡带的豫西山区为例,基于200 m分辨率DEM数据,采用均值变点法确定地形起伏度的最佳统计单元,并提取地形起伏度;以1∶10万土地利用、乡镇人口和县域各产业数据为基础,建立人口和经济空间化模型,同时生成200 m分辨率的栅格人口和经济密度图;在系统分析地形起伏度、人口和经济密度空间分布规律的基础上,借助统计分析方法基于栅格单元定量揭示了地形起伏度对人口和经济的影响,并与其他地形因子的影响进行对比分析。结果表明：① 豫西山区地形起伏度以低值为主,58.6%的区域地形起伏度小于等于0.5个基准山体的高度（相对高差≤ 250 m）;空间上呈西高东低、中间高南北低的格局,与海拔、坡度均呈较强的正相关,且与坡度的相关性更大。② 被选作验证的人口和经济数据与对应模拟值的线性拟合度分别为0.943和0.909,表明空间化结果能反映人口和经济分布的实际状况。③ 地形起伏度对人口和经济的影响强于其他地形因子的影响,与人口密度和经济密度呈较好的对数拟合关系,拟合度分别为0.911和0.874;豫西山区88.65%的人口居住在地形起伏度不超过0.5的地区,88.03%的生产总值分布在地形起伏度不超过0.3的地区。相对人口分布,研究区的经济发展向地形起伏度低值区的集聚态势更加明显。 相似文献
13.
Sushil S. Dixit John P. Smol Dennis S. Anderson Ronald B. Davis 《Journal of Paleolimnology》1990,3(3):269-286
Scaled chrysophytes in the surface sediments of 58 soft-water northern New England lakes were analyzed to assess their usefulness for inferring pH. The distributions of many taxa are correlated with lakewater pH and associated variables. Canonical correspondence analysis (CCA) and clustering grouped chrysophyte taxa according to their distributions along the pH gradient. For example, Chrysodidymus synuroideus, Mallomonas hindonii, and M. hamata commonly occur in acidic waters (pH<5.5), whereas M. caudata and M. pseudocoronata are common in circumneutral to alkaline waters. Of the five predictive models developed to infer pH, CCA based calibration had the lowest standard error (0.35 pH units). A CCA based predictive model was also developed to infer total alkalinity. The study provides strong evidence that, in the absence of past measured pH data, stratigraphic studies of sedimentary chrysophyte scales will provide accurate reconstructions of pH in northern New England lakes.This is the sixth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D.F. Charles and D.R. Whitehead are guest editors for this series. 相似文献
14.
《Urban geography》2013,34(5):496-516
The development of new approaches for understanding processes of urban development and their environmental effects, as well as strategies for sustainable management, is essential in expanding metropolitan areas. This study illustrates the potential of linking urban growth and watershed models to identify problem areas and support long-term watershed planning. Sediment is a primary source of nonpoint-source pollution in surface waters. In urban areas, sediment is intermingled with other surface debris in transport. In an effort to forecast the effects of development on surface-water quality, changes predicted in urban areas by the SLEUTH urban growth model were applied in the context of erosion-sedimentation models (Universal Soil Loss Equation and Spatially Explicit Delivery Models). The models are used to simulate the effect of excluding hot-spot areas of erosion and sedimentation from future urban growth and to predict the impacts of alternative erosion-control scenarios. Ambos Nogales, meaning "both Nogaleses," is a name commonly used for the twin border cities of Nogales, Arizona and Nogales, Sonora, Mexico. The Ambos Nogales watershed has experienced a decrease in water quality as a result of urban development in the twin-city area. Population growth rates in Ambos Nogales are high and the resources set in place to accommodate the rapid population influx will soon become overburdened. Because of its remote location and binational governance, monitoring and planning across the border is compromised. One scenario described in this research portrays an improvement in water quality through the identification of high-risk areas using models that simulate their protection from development and replanting with native grasses, while permitting the predicted and inevitable growth elsewhere. This is meant to add to the body of knowledge about forecasting the impact potential of urbanization on sediment delivery to streams for sustainable development, which can be accomplished in a virtual environment. 相似文献
15.
《Basin Research》2018,30(Z1):36-47
Radioisotope geochronology of detrital grains coupled with quantitative classification of grain morphology can provide valuable insight into the history of sediment transportation and recycling. Here we present ca. 750 new concordant U‐Pb ages from detrital zircon grains from a relatively understudied Permian sedimentary succession in the New England Orogen (eastern Australia), coupled with values of abrasion that provides a proxy for the relative source‐to‐sink distance. We show that cumulative proportion curves for age groups that correspond to plausible source regions provide insights into the palaeodrainage, even if the basin stratigraphy is relatively poorly constrained. This approach is particularly suitable for investigating complex depositional systems that received inflow from different provenance, such as back‐arc and intra‐cratonic basins. Using the example from eastern Australia, our results show that during the Early Permian, a large regional fluvial system transported detritus from continental Gondwana across the landscape of the former active continental margin (New England Orogen) and the simultaneously developing East Australian Rift System. In addition, a local drainage system mobilised detritus within the New England Orogen. Our new constraints for the Early Permian palaeogeography support the idea that the Lower Permian successions of the southern New England Orogen were deposited in a back‐arc region that was likely linked to a retreating subduction zone. 相似文献
16.
《The Professional geographer》2013,65(4):391-403
Over the past six years hog farming in North Carolina has undergone a significant restructuring. For most of this century raising hogs was a casual farm activity found throughout the state. During the past decade hog farming has been transformed along industrial-corporate lines. In the process, the swine population has expanded rapidly (exploded) and simultaneously collapsed in geographical bounds (imploded). This paper examines the linkage between the development of the industrial-corporate hog farming regime, the rapid growth in hog populations, and the geographical concentration of hog production in a newly emerging high-density hog production district in the south central area of the Coastal Plain region. 相似文献
17.
GRAEME HUGO 《New Zealand geographer》1999,55(2):25-35
New Zealand origin academics have played a key role in the academic study of Australia's population in the post-war period. The paper argues that New Zealanders have contributed not only to the furthering of knowledge of the processes of change in the Australian population but have been important in the teaching of population geography in Australian universities, made inputs into policy relating to population and been influential in the development of the Australian Population Association. Major contributions have been made by New Zealanders not only in the traditionally strong areas of population geography such as internal and international migration but also in the areas of fertility, mortality and ageing. 相似文献
18.
This study proposes a regional air pollution exposure index (RAPEI) for Auckland, Canterbury, Otago and Wellington regions. The air pollution index multiplies an emission index (NOx emissions kg/annum), a surrogate for ambient air pollution levels, with a population density index (people per sq km), a surrogate for population exposure. Census Area Units (CAUs), and subsequently defined “key areas” within a region are ranked from 0 to 16. This is one method of investigating the effectiveness of air quality monitoring networks and identifying urban exposure airsheds in New Zealand. Results verified New Zealand's urban exposure airsheds and highlighted areas that may be potential “hot spots” in terms of relatively high ambient air pollution levels and potentially high population exposures. It is possible that these areas should be closely monitored. The GIS‐based maps also show New Zealand's permanent and temporary air quality monitoring stations. 相似文献
19.
Kimberly E. Medley Mark J. McDonnell Steward T. A. Pickett 《The Professional geographer》1995,47(2):159-168
Human activities and forest-landscape structure are examined along a belt transect that extends 140 km from New York City to northwestern Connecticut. The study quantifies urban structures (population density, land use. transportation) and processes (population growth, urban land development) in the transect, and tests for relationships with the distribution, sizes, and shapes of forests. Our results identify distinct characteristics of urban and suburban environments based on the landscape structure of native forest vegetation. These findings are applicable to the management of natural areas along a gradient of urbanization. 相似文献
20.
南京都市区人口空间扩张与多中心化 总被引：4，自引：0，他引：4
20世纪90年代以来,中国进入了前所未有的快速城市化阶段,大城市人口增长和空间演变剧烈,值得进行深入研究。以南京市为研究对象,先采用地理图形分析方法对都市区人口空间扩张过程进行了分析,后又采用数学模型方法对都市区人口分布多中心化趋势进行了系统研究。结果显示:在总人口持续快速增长的背景下,南京都市区人口高密度空间已延伸到近郊区,且远郊区中的区县政府驻地和一些优先开发区域的人口密度也已很高;城市人口空间分布已出现多中心化趋势,除了老城区北部的山西路已发育成除市中心新街口之外的人口次中心以外,郊区人口集聚最强的热点--河西新城区的万达广场也有望发育成另一个人口次中心。 相似文献