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101.
Journal of Geographical Sciences - Rapid economic development and human activities have severely affected ecosystem function. Analysis of the spatial distribution of areas of rapid urbanization is... 相似文献
102.
Zhao Kang Zhou Yun Yu Xiang Yan Yajing Song Yufeng Wang Junqiang Suo Tianyuan Guo Xiao 《Natural Resources Research》2021,30(5):3839-3852
Natural Resources Research - Depletion of shallow mineral resources caused by deep mining has become an inevitable trend, and deep mining can increase safety accidents and geological hazards.... 相似文献
103.
The gravity inversion is to restore genetic density distribution of the underground target to be explored for explaining the internal structure and distribution... 相似文献
104.
105.
Identification of the “source” and “sink” patterns influencing non-point source pollution in the Three Gorges Reservoir Area 总被引:6,自引:0,他引:6
Non-point source pollution is one of the primarily ecological issues affecting the Three Gorges Reservoir Area. In this paper, landscape resistance and motivation coefficient, which integrated various landscape elements, such as land use, soil, hydrology, topography, and vegetation, was established based on the effects of large-scale resistance and motivation on the formation of non-point source pollution. In addition, cost models of the landscape resistance and motivation coefficients were constructed based on the distances from the landscape units to the sub-basin outlets in order to identify the “source” and “sink” patterns affecting the formation of non-point source pollution. The results indicated that the changes in the landscape resistance and motivation coefficients of the 16 sub-basins exhibited inverse relationships to their spatial distributions. The landscape resistance and motivation cost curves were more volatile than the landscape resistance and motivation coefficient curves. The landscape resistance and motivation cost trends of the 16 sub-basins became increasingly apparent along the flow of the Yangtze River. The landscape resistance and motivation cost models proposed in this paper could be used to identify large-scale non-point source pollution “source” and “sink” patterns. Moreover, the proposed model could be used to describe the large-scale spatial characteristics of non-point source pollution formation based on “source” and “sink” landscape pattern indices, spatial localization, and landscape resistance and motivation coefficients. 相似文献
106.
基于2005~2015年全国统计年鉴数据,采用统计地图法和空间自相关分析,分析中国高校科研人才的时空分布特征(不包括港澳台数据),并采用面板负二项回归模型,识别高校科研人才空间分布的决定因素。研究结果表明:①中国的高校科研人才分布表现出较强的空间不均衡性,总体趋势为东南密集,西北稀疏,科研人才高度集中在北京、天津、上海;②高校科研人才分布具有一定的空间集聚特征,其热点地区为北京、天津、上海和江苏等沿海省市,冷点地区集中分布在广大的西部地区和黑龙江省。2005~2015年,高级职称人才的空间集聚程度有所减弱,而中初级职称科研人才的空间集聚程度有所加强;③人才政策、高等教育规模和层次、公共服务水平和信息化水平是所有高校科研人才空间分布的主要影响因素。从职称差异的角度来看,薪酬和失业率等经济因素仅对初级职称科研人才的分布有影响,医疗、文化公共服务水平和人才政策仅对中高级职称科研人才的分布有影响,高等教育的规模与层次对各种职称人才的分布均有影响;从地区差异的角度来看,西部地区高校科研人才受到经济因素影响更为明显,而中东部高校科研人才受到公共服务水平影响的更为明显。 相似文献
107.
生物基可降解聚乳酸(PLA)沙障对沙丘表层沉积物粒度特征的影响 总被引:4,自引:0,他引:4
以吉兰泰盐湖北部流沙区铺设8 a的不同规格聚乳酸(PLA)沙障内沉积物为研究对象,利用激光衍射技术分析了沙丘表层0~3 cm沉积物粒度组成,计算并分析平均粒径、标准偏差等粒度参数,探讨了影响障内沉积物相对粗细的关键组分,分析PLA沙障的防沙效益。结果表明:PLA沙障内沉积物以细沙、中沙、极细沙为主。中沙、极细沙、细沙是障内沉积物的关键组分。PLA沙障的阻滞作用使得中沙、粗沙含量百分比升高,细颗粒含量百分比降低,障内沙粒分选性逐渐变差,峰态偏离正态分布,向负偏方向发展,频率分布曲线分布范围变宽,累积频率曲线变缓,表层颗粒组成趋于粗化。1 m×1 m规格PLA沙障内均以积沙为主;沙丘迎风坡和背风坡的2 m×2 m、3 m×3 m沙障内均为积沙状态,丘顶则为风蚀状态。综合考虑沙障铺设成本和防护效果,得出研究区域内2 m×2 m规格PLA沙障整体防沙效益最佳。 相似文献
108.
To ensure the safety of structures, high-speed railway and highway founded on liquefiable soils, liquefaction evaluation is a primary task. Herein, a dynamic set pair analysis method based on variable weights is introduced to assess liquefaction. A concept of connection degree of set pair consisting of the evaluation sample and the classification standard was described to interpret the uncertainty of liquefaction and relationship. Moreover, based on reward and penalty mechanism, state variable vectors were presented to assign composite weights of evaluation indicators in order to take into account impacts of indicator variation. And the integrated connection degree to each grade was calculated to evaluate liquefaction of the evaluated cases. Results from practical example and comparison with field investigation and extension method indicated that this proposed model used to evaluate liquefaction is feasible and effective. In addition, it can quantitatively describe liquefaction hierarchy of evaluated samples. 相似文献
109.
Sediment transport and overpressure generation are coupled primary through the impact of effective stress on subsidence and compaction. Here, we use mathematical modeling to explore the interactions between groundwater flow and diffusion-controlled sediment transport within alluvial basins. Because of lateral variation in permeability, proximal basin facies will have pore pressure close to hydrostatic levels while distal fine-grained facies can reach near lithostatic levels. Lateral variation in pore pressure leads to differential compaction, which deforms basins in several ways. Differential compaction reduces basin size, bends isochron surfaces across the sand–clay interface, restricts basinward progradation of sand facies, and reduces the amplitude of oscillation in the lateral position of the sand–clay interface especially in the deepest part of the section even when temporal sediment supply are held constant. Overpressure generation was found to be sensitive to change in sediment supply in permeable basins (at least 10−17 m2 in our model). We found that during basin evolution, temporal variations in overpressure and sediment supply fluctuations are not necessarily in phase with each other, especially in tight (low permeability) basins (<10−17 m2 in our model). 相似文献
110.
在乔治王岛中部的阿德默勒尔蒂湾 ,凯勒半岛、于尔曼山嘴和埃内坎角是第三纪火山岩集中分布区。野外地质调查和同位素年代学研究表明 ,凯勒半岛发生了三期火山喷发 (三个火山喷发旋回 ) ,同时伴随着火山活动中心的不断北移 ;在第二期火山喷发之后 ,火口塌陷 ,形成破火山 ,之后在半岛北部又发生火山喷发 ,并向东迁移到于尔曼山嘴。因此凯勒半岛是一复活破火山 ,火山活动具有随时间迁移的特性。埃内坎角火山活动虽与上述两地区大致同时 ,但化学成分上不存在明显演化关系 ,应属另一相对独立的火山活动中心 相似文献