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911.
生态占用是可持续发展的新指标,可直接反应区域发展的现状和未来。阜阳市作为皖西北地区的中心城市,近年来城市规模进一步扩大,城市生产和人民生活对土地利用的强度均有增加。对此,应结合阜阳市土地利用现状,应用Wackemagel等提出的生态占用测度方法对阜阳市的生态占用和生态容量进行计算。从宏观上度量阜阳市社会经济发展的生态状况和可持续性。结果表明,阜阳市人均生态赤字为2.52172313hm^2,立足赤字现状,分析问题,提出未来可持续发展的措施与策略。 相似文献
912.
云南省土地综合承载能力空间差异研究 总被引:1,自引:0,他引:1
土地资源承载力是区域人口、资源与环境可持续发展评价的重要指标。结合云南省实际情况,从水土资源、生态环境、社会资源和经济技术4个方面选取了20个评价指标构建土地综合承载力的评价指标体系,采用均方差决策赋权法、综合指数法对云南省2008年的土地综合承载力状况进行综合评价。结果显示,依照土地综合承载力评价结果将云南省划分为4大类型承载区域,整体上呈现了西北、东南、东北地区土地综合承载力指数值较低,逐渐向中部一带增高,其空间分异特征较明显,具有一定的地域相近性。进而分析了造成此空间差异的原因并提出了相应的对策与建议,为改善云南省土地综合承载力状况,谋求可持续发展提供参考。 相似文献
913.
L. Schreiber I. Foppiani C. Robert E. Diolaiti J.-M. Conan M. Lombini 《Monthly notices of the Royal Astronomical Society》2009,396(3):1513-1521
Over the last few years increasing consideration has been given to the study of laser guide stars (LGS) for the measurement of the disturbance introduced by the atmosphere in optical and near-infrared (near-IR) astronomical observations from the ground. A possible method for the generation of a LGS is the excitation of the sodium layer in the upper atmosphere at approximately 90 km of altitude. Since the sodium layer is approximately 10 km thick, the artificial reference source looks elongated, especially when observed from the edge of a large aperture. The spot elongation strongly limits the performance of the most common wavefront sensors. The centroiding accuracy in a Shack–Hartmann wavefront sensor, for instance, decreases proportionally to the elongation (in a photon noise dominated regime). To compensate for this effect, a straightforward solution is to increase the laser power, i.e. to increase the number of detected photons per subaperture. The scope of the work presented in this paper is twofold: an analysis of the performance of the weighted centre of gravity algorithm for centroiding with elongated spots and the determination of the required number of photons to achieve a certain average wavefront error over the telescope aperture. 相似文献
914.
V. Kornilov S. Ilyasov O. Vozyakova Yu. Tillaev B. Safonov M. Ibragimov N. Shatsky Sh. Egamberdiev 《Astronomy Letters》2009,35(8):547-554
We present the results of our 2005–2007 campaign to measure the vertical distribution of optical turbulence above Mount Maidanak. The measurements were performed with the MASS instrument, a multi-aperture scintillation sensor that has been widely used for such studies in recent years at many observatories worldwide. Analysis of the data shows that the median seeing in the free atmosphere (at an altitude of 0.5 km and higher) is 0 ″46, while the isoplanatic angle is 2″.47. Given the large time constant (about 7 ms at good seeing), such conditions are favorable for using adaptive optics and interferometric measurements in the visible and near-infrared spectral ranges. 相似文献
915.
This article provides a quantitative test of the relationship between adaptive capacity and socio-economic status (SES) at the municipal level. Local participation in a U.S. floodplain management program, the Community Rating System (CRS), is used as an indicator of adaptive capacity. The relationship between aggregated measures of SES and CRS participation is tested using probit, OLS and tobit models. The analysis indicates that socio-economic characteristics of a municipality's population are associated with the capacity of municipal leaders to effect collective action in response to environmental challenges. More theoretical work and case studies are needed to fully explain the reasons for this association. 相似文献
916.
917.
The adaptive wavelet collocation method(AWCM)is a variable grid technology for solving partial differential equations(PDEs)with high singularities.Based on interpolating wavelets,the AWCM adapts the grid so that a higher resolution is automatically attributed to domain regions with high singularities. Accuracy problems with the AWCM have been reported in the literature,and in this paper problems of effciency with the AWCM are discussed in detail through a simple one-dimensional(1D)nonlinear advection equation whose analytic solution is easily obtained.A simple and effcient implementation of the AWCM is investigated.Through studying the maximum errors at the moment of frontogenesis of the 1D nonlinear advection equation with different initial values and a comparison with the finite difference method(FDM) on a uniform grid,the AWCM shows good potential for modeling the front effciently.The AWCM is also applied to a two-dimensional(2D)unbalanced frontogenesis model in its first attempt at numerical simulation of a meteorological front.Some important characteristics about the model are revealed by the new scheme. 相似文献
918.
The effect of inclined loading on the bearing capacity of foundations on horizontal ground surface is well established and both the exact solution and simpler empirical equations are available for the calculation of the failure loads. However, for footings on or near slopes complete solutions are available only for vertical loading. This paper investigates the influence of inclined loading on the horizontal and vertical failure loads. The finite element, upper bound plasticity and stress field methods are used to examine a wide range of geometries and soil properties. The methods are first validated against known solutions for two special cases and are subsequently employed to investigate the effect of the geometrical and material properties on the failure loads and the bearing capacity load interaction diagram. Based on this investigation an empirical equation is proposed for the load interaction diagram for undrained inclined loading of footings on or near slopes. 相似文献
919.
920.