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排序方式: 共有2297条查询结果,搜索用时 15 毫秒
21.
本文对成都市总人口、建成区面积等11个因子、作了主成份回归L-S估计和M-估计,讨论了成都城市发展对“热岛”强度的主要影响因子。结果表明,城区房屋建筑面积及总人口数是影响城市气候(气温)的主要因子,其次为城市人口总户数、建成面积等。 文中,对回归方程进行了拟合计算,回归效果比较满意(尤其是稳健回归)。 相似文献
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23.
Mariama Awumbila 《GeoJournal》2006,67(2):149-161
Poverty trends in Ghana show a decline over the last two decades. However, the period also shows evidence of the intensification
of vulnerability and exclusion among some groups, including women. Among several variables accounting for women’s vulnerability
to poverty are gender inequalities, which it is argued, undermines development and the prospects for improving standards of
living. Therefore it has been suggested that policies, which aim at reducing poverty and promoting sustainable development
must integrate gender equality, equity and women’s empowerment in its goals. Despite these, the interconnections between a
reduction in gender inequality and a reduction in poverty are complex. The paper explores the gender dimensions of poverty
in Ghana, and how gender inequalities are manifested and implicated in the reproduction of poverty. It also assesses the extent
to which these have been taken into account in poverty reduction strategies and policies to enhance the situation of women.
It concludes that if strategies to engender poverty reduction programmes are to be sustainable it is important to recognize
unequal gender relations and the structures of power that women confront at all levels in Ghana and how these increase women’s
vulnerability to poverty. 相似文献
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25.
Geomorphic effects of rural-to-urban land use conversion on three streams in the Central Redbed Plains of Oklahoma 总被引:2,自引:1,他引:2
This research evaluates the impact of rural-to-urban land use conversion on channel morphology and riparian vegetation for three streams in the Central Redbed Plains geomorphic province (central Great Plains ecoregion) of Oklahoma. The Deep Fork Creek watershed is largely urbanized; the Skeleton Creek watershed is largely rural; and the Stillwater Creek watershed is experiencing a rapid transition from rural to urban land cover. Each channel was divided into reaches based on tributary junctions, sinuosity, and slope. Field surveys were conducted at transects in a total of 90 reaches, including measurements of channel units, channel cross-section at bankfull stage, and riparian vegetation. Historical aerial photographs were available for only Stillwater Creek watershed, which were used to document land cover in this watershed, especially changes in the extent of urban areas (impervious cover).The three streams have very low gradients (< 0.001), width-to-depth ratios < 10, and cohesive channel banks, but have incised into red Permian shales and sandstone. The riparian vegetation is dominated by cottonwoods, ash, and elm trees that provide a dense root mat on stream banks where the riparian vegetation is intact. Channels increased in width and depth in the downstream direction as is normally expected, but the substrate materials and channel units remained unchanged. Statistical analyses demonstrated that urbanization did not explain spatial patterns of changes in any variables. These three channels in the central Redbed Plains are responding as flumes during peak flows, funneling runoff and the wash-load sediment downstream in major runoff events without any effect on channel dimensions. Therefore, local geological conditions (similar bedrock, cohesive substrates and similar riparian vegetation) are mitigating the effects of urbanization. 相似文献
26.
Chemical methods are generally chosen to monitor soil pollution but magnetic measurements proved to yield additional information at low cost and less time consumption. In this investigation, the novel use of rapid and non-destructive magnetic measurements to characterize Br levels in Xuzhou (China) urban roadside soils was reported. X-ray fluorescence spectrometry (XRF) was used to quantify Br in the soil samples. Data from 21 roadside soil samples confirm Br contamination, with a mean level of 4.36 mg kg−1 and a range of 2.4–8.7 mg kg−1. These values are higher than that of unpolluted soils in Xuzhou that averages 1.1 mg kg−1. Hierarchical clustering analysis shows Br in Xuzhou roadside soils is mainly from road traffic. Clear correlations between Br levels and simple magnetic parameters [mass specific susceptibility (χ
LF), susceptibility of anhysteretic remanent magnetization (χ
ARM), saturation isothermal remanence (SIRM)] are observed. The present study shows that these three magnetic parameters can be used as a proxy for Br levels in Xuzhou urban roadside soils. 相似文献
27.
Mihael Brencic 《Environmental Geology》2006,49(6):804-813
During the planning, designing, construction, operation and maintenance of highways, groundwater can be of important environmental
and constructional constraint that can significantly influence the safety operation of traffic and of big influence on the
operational costs of highways. To classify and conceptualize the relation between groundwater and highways, three important
groups of problems can be determined: groundwater protection from highway influences, protection of highway from groundwater
and economic use of groundwater for highway operation. In the present study, groundwater management strategies are represented
during all life cycles of highways. Greater emphasis is given to groundwater protection and field hydrogeological investigations
for proper groundwater management related to the highway. The approach adopted in Slovenia and the role of hydrogeology is
given as an illustration. 相似文献
28.
29.
基于GIS的城镇土地定级信息系统建模方法探讨 总被引:2,自引:0,他引:2
基于GIS的城镇土地定级信息系统在建设过程中,定级方法确定、定级单元大小确定和定级因素/子权重值的生成是关键,且三者都具有不同的确定方法,因此选择什么样的方法决定了系统建立的优劣。本文着重归纳、总结了城镇土地定级信息系统定级方法,通过对比分析,探讨了最优定级方法、最优网格单元大小划分方法和最优因素/子权重值计算方法。 相似文献
30.
泰安市地下水开发利用中的水环境问题及对策 总被引:2,自引:6,他引:2
以泰安市为例,论述了地下水开发利用中出现的区域地下水位下降、地下水资源衰竭、地下水水质恶化、地面沉降、地面裂缝和地面塌陷等水环境问题,并提出了保护对策与建议. 相似文献