首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:从到   被引次数:从到   他引次数:从到 提示：输入*表示无穷大
全文获取类型
  收费全文   20篇
  免费   1篇
专业分类
测绘学   1篇
地球物理   10篇
地质学   10篇
出版年
  2017年   2篇
  2014年   5篇
  2013年   4篇
  2011年   1篇
  2010年   2篇
  2008年   3篇
  2007年   1篇
  1994年   1篇
  1973年   1篇
  1961年   1篇
排序方式： 共有21条查询结果，搜索用时 312 毫秒
1.
  相似文献   
2.
This paper investigates surface elevation changes that occurred during 1996–2004 in the Jharia coalfield through the digital elevation model (DEM) generated using synthetic aperture radar interferometry (InSAR) using ERS-1/2 (European Remote Sensing Satellite) tandem and RADARSAT-1 data. The comparison of elevation values derived from the InSAR DEM and topographic height data shows a bias of 23.08 m with root-mean-square error of ±2.31 m (5.8 %). The accuracy of the DEM was investigated by comparing the elevation profiles with the digitized elevation contour data at four different locations. The profile comparison shows a mean bias of 22.68 m. Local topography shows changes in elevation up to ±40.00 m due to mining activities on the 8-year time period. The results of InSAR-derived heights and topographic heights were comparable and well-matched except at a few locations where topographic data were unavailable. DEM generated using InSAR due to its high spatial details is ideal for the detection and estimation of surface elevation changes in mining areas.  相似文献   
3.
A new base isolation system using scrap tire rubber pads (STRP) has been introduced for seismic mitigation of ordinary residential buildings. The rubber and the steel reinforcing cords used in manufacturing the tire are the alternative materials of the proposed base isolation system. The steel reinforcing cords represent the steel plates used in conventional laminated rubber bearings. These steel reinforcing cords shall prevent the lateral bulging of the rubber bearing. The proposed base isolation system has no bonding between the superstructure and the foundation beam which allows for rollover deformation. In the first part of the study, the STRP layers were just stacked one on top of another without applying the adhesive. This paper presents loading test as well as finite element analysis (FE analysis) of strip STRP isolators that are subjected to any given combination of static vertical and lateral loads. The results of the static vertical and horizontal loading test conducted on STRP isolators were used to calculate the mechanical properties of the isolators, including stiffness and damping values. The load–displacement relationship of STRP isolators were compared between experimental and FE analysis results and the results were found to be in close agreement. The stress state within the STRP isolators was also analyzed in order to estimate the maximum stress demand in the rubber and steel reinforcing cords. These STRP isolators have several advantages over conventional laminated rubber bearings including superior damping properties, lower incurred cost, light weight and easily available material. This study suggests that using the STRP as low cost base isolation device for ordinary residential buildings is feasible.  相似文献   
4.
The paper presents the first comprehensive survey of congener profiles (12 congeners) of polybrominated diphenyl ethers (PBDEs) in core sediment samples (<63 microm) covering seven sites in Sundarban mangrove wetland (India). Gas-chromatographic analyses were carried out in GC-Ms/Ms for tri- to hepta- brominated congeners. Results pointed out a non-homogenous contamination of the wetland with summation operator(12) PBDE values ranging from 0.08 to 29.03 ngg(-1), reflecting moderate to low contamination closely in conformity to other Asian aquatic environments. The general order of decreasing congener contribution to the total load was: BDE 47>99>100>154, similar to the distribution pattern worldwide. Although tetrabromodiphenyl ether BDE 47 was found in all samples followed by hexabromodiphenyl ether BDE-154, they were not necessarily the dominant congeners. No uniform temporal trend on PBDE levels was recorded probably due to particular hydrological characteristics of the wetland and/on non-homologous inputs from point sources (untreated municipal wastewater and local industries, electronic wastes from the dump sites, etc.) of these compounds. Because of the propensity of PBDEs to accumulate in various compartments of wildlife and human food webs, evaluation of biological tissues should be undertaken as a high priority.  相似文献   
5.
Groundwater preservation comprises a major problem in water policy. The comprehension of the groundwater/hydraulic systems can provide the means to approach this problem. Generally, drilling is expensive and time-consuming. On the other hand, new techniques have been applied during the last few decades that provide useful information on the depth and quality of aquifers. Among them, transient electromagnetic method (TEM) is an appealing method that provides fast results with minimum field crew and solves several hydrogeological problems. Many portable systems for single-site measurements are commercially available. The TEM-Fast 48HPC was used for acquiring 106 soundings in the northwestern Crete in Greece for defining the hydrogeological characteristics of the study area, since there were no available data from boreholes. Detailed geological, hydrolithological and tectonic survey was applied prior to the geophysical measurements. All the data were integrated to produce a secure and reliable hydrogeological model for the study area prior to any future hydrowell. Specifically, geometrical and hydraulic data of the study area groundwater were acquired. Two unconnected aquifers were detected and their possible contamination due to saltwater intrusion was analyzed and eliminated. Moreover, a location for borehole construction and groundwater pumping based on the potential of the aquifer system was proposed. Finally, the contribution of TEM (and electrical resistivity tomography) geophysical methods in studying complex coastal aquifers is shown by this work.  相似文献   
6.
Summary The response of an elastic half-space with a non-homogeneous surface layer due to aSH-source operating in the non-homogeneous layer of an elastic half-space have been studied. The elastic and physical constants vary exponentially in the surface layer. The surface displacement consists of several integrals. On approximate evaluation of these integrals, they are identified as direct or reflected pulses.  相似文献   
7.
Summary The disturbances produced in a visco-elastic medium by impulsive forces on the surface of a spherical cavity inside the medium have been studied.  相似文献   
8.
Slope stability analysis is one of the most important problems in geotechnical engineering. The development in slope stability analysis has followed the development in computational geotechnical engineering. This paper discusses the application of different recently developed artificial neural network models to slope stability analysis based on the actual slope failure database available in the literature. Different ANN models are developed to classify the slope as stable or unstable (failed) and to predict the factor of safety. The developed ANN model is found to be efficient compared with other methods like support vector machine and genetic programming available in literature. Prediction models are presented based on the developed ANN model parameters. Different sensitivity analyses are made to identify the important input parameters.  相似文献   
9.
A multispecies bloom caused by the centric diatoms, viz. Coscinodiscus radiatus, Chaetoceros lorenzianus and the pennate diatom Thalassiothrix frauenfeldii was investigated in the context of its impact on phytoplankton and microzooplankton (the loricate ciliate tintinnids) in the coastal regions of Sagar Island, the western part of Sundarban mangrove wetland, India. Both number (15–18 species) and cell densities (12.3 × 103 cells l−1 to 11.4 × 105 cells l−1) of phytoplankton species increased during peak bloom phase, exhibiting moderately high species diversity (H′ = 2.86), richness (R′ = 6.38) and evenness (E′ = 0.80). The diatom bloom, which existed for a week, had a negative impact on the tintinnid community in terms of drastic changes in species diversity index (1.09–0.004) and population density (582.5 × 103 to 50 × 103 ind m−3). The bloom is suggested to have been driven by the aquaculture activities and river effluents resulting high nutrient concentrations in this region. An attempt has been made to correlate the satellite remote sensing-derived information to the bloom conditions. MODIS-Aqua derived chlorophyll maps have been interpreted.  相似文献   
10.
Investigating factors controlling the temporal patterns of nitrogen (N) and dissolved organic carbon (DOC) exports on the basis of a comparative study of different land uses is beneficial for managing water resources, especially in agricultural watersheds. We focused our research on an agricultural watershed (AW) and a forested watershed (FW) located in the Shibetsu watershed of eastern Hokkaido, Japan, to investigate the temporal patterns of N and DOC exports and factors controlling those patterns at different timescales (inter‐annual, seasonal, and hydrological event scales). Results showed that the annual patterns of N and DOC exports significantly varied over time and were probably controlled by climate. Higher discharge volumes in 2003, a wet year, showed higher N and DOC loadings in both watersheds. However, this process was also regulated by land use associated with N inputs. Higher concentrations and loadings were shown in the agricultural watershed. At the seasonal scale, N and DOC exports in the AW and the FW were more likely controlled by sources associated with land use. The Total N (TN) and Nitrate‐N (NO3?‐N) had higher concentrations during snowmelt season in the AW, which may be attributed to manure application in late autumn or early winter in the agricultural watershed. Concentrations of TN, NO3?‐N, dissolved organic nitrogen (DON), and DOC showed higher values during the summer rainy season in the FW, related to higher litter decomposition during summer and autumn and the fertilizer application in the agricultural area during summer. Higher DOC concentrations and loadings were observed during the rainy season in the AW, which is probably attributed to higher DOC production related to temperature and microbial activity during summer and autumn in grasslands. Correlations between discharge and concentrations differed during different periods or in different watersheds, suggesting that weather discharge can adequately represent the fact that N export depends on N concentrations, discharge level, and other factors. The differing correlations between N/DOC concentrations and the Si concentration indicated that the N/DOC exports might occur along different flow paths during different periods. During baseflow, the high NO3?‐N exports were probably derived from deep groundwater and might have percolated from uplands during hydrological events. During hydrological events, NO3?‐N exports may occur along near‐surface flow paths and in deep groundwater, whereas DOC exports could be related to near‐surface flow paths. At the event scale, the relationships between discharge and concentrations of N and DOC were regulated by antecedent soil moisture (shallow groundwater condition) in each watershed. These results indicated that factors controlling N and DOC exports varied at different timescales in the Shibetsu area and that better management of manure application during winter in agricultural lands is urgently needed to control water pollution in streams. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号