宁夏产业结构演进与经济增长系统研究   总被引：6，自引：5，他引：6  

刘小鹏  王亚娟  王永洁  王联兵 《干旱区地理》2006,29(6):915-922

产业结构的演进与升级一定程度上反映了区域经济的发展阶段与发展能力。以1978-2003年的统计数据为基础,系统研究了宁夏产业结构变迁与区域经济发展的关系。研究结果表明:(1)宁夏产业结构的变化符合产业结构变迁的一般规律,但产业结构高度化水平依然低下;(2)宁夏产业结构变迁的空间集聚效应明显;(3)宁夏产业结构演进对经济增长的影响形成产业结构偏离为正,竞争力偏离份额为负型、产业结构偏离为正,竞争力偏离份额为正型和产业结构偏离为负,竞争力偏离份额为正型三种类型;(4)产业结构变迁对各地区经济增长的影响差异较大。研究指出,在西部大开发和区域经济一体化进程中,以及在国家和地区产业政策调整的背景下,建立产业协调与分工合作机制,发展特色优势产业,推进重点地带布局开发,形成区域性“群落型”经济优势,成为新时期宁夏产业结构调整的战略选择。  相似文献   

侵蚀红壤植被恢复后土壤呼吸日动态及日呼吸速率测定方法比较     

谢锦升  杨玉盛  曾宏达  杨智杰  黄石德  岳辉 《福建地理》2006,(4)

采用密闭室红外气体分析仪法(IRGA法)观测了中亚热带红壤侵蚀裸地植被恢复后不同季节土壤呼吸速率的日动态变化,并比较了IRGA法与碱吸收法(AA法)测定的土壤呼吸速率.结果表明:侵蚀裸地植被恢复后土壤呼吸速率日动态呈单峰曲线,与土壤温度的昼夜变化基本一致,最高值一般出现在午后13∶00~17∶00,最低值出现在凌晨3∶00~7∶00;植被恢复显著提高了土壤日呼吸速率,但明显降低了土壤呼吸速率日变化幅度;马尾松林对土壤呼吸速率日变化幅度降低程度高于板栗园和百喜草地,且对夏季的降低程度影响最大.而IRGA法和AA法测定的土壤呼吸速率具有显著的幂函数关系,AA法测定的土壤呼吸速率为IRGA法的27.5%~218%,平均为76.2%.当土壤呼吸速率较低时,AA法比IRGA法高估了土壤呼吸速率;反之,AA法则低估了土壤呼吸速率.  相似文献   

The effective elastic thickness of the India Plate from receiver function imaging, gravity anomalies and thermomechanical modelling   总被引：2，自引：0，他引：2  

György Hetényi  Rodolphe Cattin  Jérôme Vergne  John L. Náb&#;lek 《Geophysical Journal International》2006,167(3):1106-1118

  相似文献   

Projecting land-use change processes in the Sierra Norte of Oaxaca, Mexico     

Leticia Gmez-Mendoza  Ernesto Vega-Pea  M. Isabel Ramírez  Jos Luis Palacio-Prieto  Leopoldo Galicia 《Applied geography (Sevenoaks, England)》2006,26(3-4):276-290

The objective of study was to explore short-term trends of processes that determine land-use change in Sierra Norte of Oaxaca (SNO), Mexico. Land use and land cover changes (LULCC) were estimated in a complex mosaic of vegetation in the SNO from 1980 to 2000, and projected them to 2020 through a Markovian model. SNO is highly vulnerable to climatic change according to a 2050 GCM scenario. However, 3% annual rate of tropical and temperate forest deforestation from agriculture and livestock encroachment, suggest the threat from land-use change is higher than that from climatic change for this study site. Productive land-use strategies are needed to reduce such high deforestation rates for tropical regions. Controlling deforestation would also reduce short-term effects of CO₂ emissions to the atmosphere. Because of the necessity to evaluate anthropogenic ecosystem changes, it is imperative to separate short-term influences such as deforestation, from long-term influences such as climatic change.  相似文献   

SOCIAL RELATIONS SPATIALLY FIXED: CONSTRUCTION AND MAINTENANCE OF SCHOOL DISTRICTS IN SAN ANTONIO,TEXAS     

Christine M. Drennon 《Geographical review》2006,96(4):567-593

ABSTRACT. More than 140 court cases filed in the United States between 1970 and 2003 argued that unacceptable and unconstitutional funding disparities exist among school districts in most states. In those arguments, stories, statistics, and maps are used to compare various school districts to prove that conditions are indeed unequal. Both sides—plaintiff and defendant—use such information to disprove each other's contentions. In so doing, each assumes that the political spaces of the school districts are absolute, timeless, and independent. Failure to recognize that these spaces—the school districts—are not objective but, in fact, constitutive of the class and race relations actually being argued and debated in court further legitimates local geographies of privilege and deprivation. I examine the formation of the school districts around San Antonio, Texas to illustrate that these districts are far from independent of one another and were formed to isolate privileged communities from the rest of the city. A relational view of space‐time allows such spaces as school districts to assume a political role, as opposed to the absolute, independent spaces they now represent.  相似文献   

Lake-Level Fluctuations and Small-Scale Vegetation Patterns During the Late Glacial in The Netherlands     

Johanna A. A. Bos  Sjoerd J. P. Bohncke  C. Roel Janssen 《Journal of Paleolimnology》2006,35(2):211-238

Late glacial changes in the vegetation were studied in and around a former lake on the southeastern side of a coversand ridge near Milheeze (southern Netherlands). Analyses of microfossils and macroremains and AMS ¹⁴C dating were performed on four sediment cores along a transect from sand ridge to the lake centre. Small-scale vegetation patterns and lake-level fluctuations were reconstructed in detail based on the information provided by the transect. For the first time in The Netherlands, cores along a transect within one lake were used to reconstruct the amplitude of late glacial lake-level fluctuations. Near Milheeze, a small and shallow lake was formed during the Bølling. The large increase in the water level during the Bølling and early Allerød, and the transition to more eutrophic conditions at the start of the Allerød, were probably related to the disappearance of permafrost. During the Allerød, open birch and pine woodlands developed in the area. In the lake, organic deposits accumulated, and the lake size and depth fluctuated. At the start of the Younger Dryas, higher lake water levels were recorded and woodlands became more open as a result of both a drop in the temperature and an increase in the effective precipitation. During the late Younger Dryas the lake water level dropped as the climate became drier and temperatures slightly increased. Accumulation of organic deposits in the lake ceased at the end of the Younger Dryas, which was caused by a drop in the water level in combination with the hydroseral succession process within the lake itself. The climatic signal reflected in the late glacial flora and lake-level fluctuations agree well with other published data from The Netherlands.  相似文献   

The place of individuals in the politics of scale   总被引：1，自引：0，他引：1  

Julie Cidell 《Area》2006,38(2):196-203

Conceptualizations and re-conceptualizations of scale have been powerful tools for explaining spatial processes that transcend traditionally-bounded territories. Examining the role of individuals within a politics of scale can do even more to explain multi-scalar conflicts. This paper does so by examining struggles over airport expansion in the US, showing how an understanding of the various roles of individuals in the politics of scale – as sites of multiple scales, as actors constituting other scales, and as scales in and of themselves – better explains multi-scalar conflicts and offers more opportunities for resolving them.  相似文献   

Comparison of methods to model the gravitational gradients from topographic data bases   总被引：7，自引：0，他引：7  

Christopher Jekeli  Lizhi Zhu 《Geophysical Journal International》2006,166(3):999-1014

A number of methods have been developed over the last few decades to model the gravitational gradients using digital elevation data. All methods are based on second-order derivatives of the Newtonian mass integral for the gravitational potential. Foremost are algorithms that divide the topographic masses into prisms or more general polyhedra and sum the corresponding gradient contributions. Other methods are designed for computational speed and make use of the fast Fourier transform (FFT), require a regular rectangular grid of data, and yield gradients on the entire grid, but only at constant altitude. We add to these the ordinary numerical integration (in horizontal coordinates) of the gradient integrals. In total we compare two prism, two FFT and two ordinary numerical integration methods using 1" elevation data in two topographic regimes (rough and moderate terrain). Prism methods depend on the type of finite elements that are generated with the elevation data; in particular, alternative triangulations can yield significant differences in the gradients (up to tens of Eötvös). The FFT methods depend on a series development of the topographic heights, requiring terms up to 14th order in rough terrain; and, one popular method has significant bias errors (e.g. 13 Eötvös in the vertical–vertical gradient) embedded in its practical realization. The straightforward numerical integrations, whether on a rectangular or triangulated grid, yield sub-Eötvös differences in the gradients when compared to the other methods (except near the edges of the integration area) and they are as efficient computationally as the finite element methods.  相似文献   

Redistribution of recent collision push and ridge push in Central Europe: insights from FEM modelling   总被引：2，自引：0，他引：2  

M. Jarosi&#;ski  F. Beekman  G. Bada  S. Cloetingh 《Geophysical Journal International》2006,167(2):860-880

  相似文献   

Effects of mode coupling and location of rotational axis on glacial induced rotational deformation in a laterally heterogeneous viscoelastic earth     

Patrick Wu  Hansheng Wang 《Geophysical Journal International》2006,167(2):853-859

  相似文献