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991.
WEIWenzhan ZHONGYexun PENGYueying ZHENGHongbo 《地球空间信息科学学报》2003,6(3):62-65
992.
Basic characteristics of active tectonics of China 总被引:84,自引:8,他引:76
Active tectonics is inferred to all the structures which have been active since the late Pleisto-cene, 100—120 ka B.P., are still active recently, and will be active in a certain time period in the future, such as active faults, active folds, active basi… 相似文献
993.
Sea surface height and transport stream function of the South China Sea from a variable-grid global ocean circulation model 总被引:8,自引:0,他引:8
The study on the South China Sea (SCS) circulation has a history of more than 40 years. Nevertheless, the SCS circulation is not fully understood compared with the Bohai Sea, Yellow Sea and East China Sea (ECS). Many numerical studies on the SCS circulati… 相似文献
994.
Lateral load pattern in pushover analysis 总被引:9,自引:2,他引:7
The seismic capacity curves of three types of buildings including frame, frame-shear wall and shear wall obtained by pushover
analysis under different lateral load patterns are compared with those from nonlinear time history analysis. Based on the
numerical results obtained a two-phase load pattern; an inverted triangle (first mode) load pattern until the base shear force
reachesβ times its maximum value, Vmax, followed by a (x/H)α form, hereβ and α being some coefficients depending on the type of the structures considered, is proposed in the paper, which can provide
excellent approximation of the seismic capacity curve for low-to-mid-rise shear type buildings. Furthermore, it is shown both
the two-phase load pattern proposed and the invariant uniform pattern can be used for low-to-mid-rise shear-bending type and
low-rise bending type of buildings. No suitable load patterns have been found for high-rise buildings. 相似文献
995.
GIS-based hazard mapping and zonation of debris flows in Xiaojiang Basin,southwestern China 总被引:11,自引:0,他引:11
Y.?P.?HeEmail author H.?Xie P.?Cui F.?Q.?Wei D.?L.?Zhong J.?S.?Gardner 《Environmental Geology》2003,45(2):286-293
Debris flow sites were identified at 140 locations in the Xiaojiang Basin in Yunnan province, southwestern China. Their spatial distribution and catchment characteristics are described in detail on the basis of previous research, air photo interpretation, field investigation and mapping using Geographical Information Systems (GIS). Using a statistical approach, a quantitative model of hazards assessment and zonation was developed through synthesis analysis of basin areas, gradients, and the relative reliefs of these debris flow sites. In terms of debris flow hazard assessment, areas within the Xiaojiang Basin can be classified as severe, heavy and light hazard regions. 相似文献
996.
S.?P.?BiEmail author N.?Gan X.?C.?Lu H.?Y.?Ni H.?Lin X.?L.?Wang Z.?B.?Wei 《Environmental Geology》2003,45(1):65-71
As the ongoing global research on acid precipitation is developing in depth, more and more attention has been paid to the ecological effects of aluminum (Al) due to its toxicity to plants and animals, which is caused by acid precipitation. As a very serious problem of terrestrial and aquatic environmental acidification occurs in China, especially in southwestern China, a systematic investigation of Al speciation in these regions is very important. In this paper, the Al speciation results of surface waters in China are reported and its ecological impacts is evaluated. More than 100 water samples were collected from about twenty provinces of China. Driscoll's Al speciation scheme combined with the modified MINQEL computer model is used for speciation of Al. This study shows that the ecological impacts of acidification are quite different between China and Western countries, because of different geographical environments and geological settings. In Western countries, acidification is mainly caused by NO2-. Due to low concentrations of K+, Na+, Ca2+, Mg2+, the buffer capacities of soil and water are weak. Therefore, natural waters can be acidified to pH<5 very easily, resulting in a considerable mobilization of Al and worsening of the ecological environment. In China, acid precipitation is mainly in the form of sulfuric acid. In northwestern China, concentrations of K+, Na+, Ca2+, Mg2+ are high in soil and surface waters. This leads to much higher capacity and a high resistance ability to acidification. The pH values of waters in this region are high (around 7) and no serious Al toxicity is found at present. However, in northeastern and southeastern China, the soil is rich in Al (unsaturated aluminosilicates in northeastern China, saturated aluminosilicates in north and central China, aluminum-rich soil in southeastern and southwestern China). The concentrations of K+, Na+, Ca2+, Mg2+ in soil and waters are lower than those of northwestern China. Therefore the buffer capacity is limited. Numerous surface waters have already been acidified and pH values declined to 5. The impacts of Al toxicity on ecological systems in these regions are very serious, especially in Jiangxi, Hubei Provinces and Chongqing Municipality. 相似文献
997.
土壤有机无机复合体的研究进展 总被引:19,自引:0,他引:19
对土壤有机无机复合体结构模型、有机无机复合体与团聚体的关系、有机无机复合体的肥力特征等方面的最新研究成果进行了综合评述。现代测试技术和计算机技术的应用为土壤有机无机复合体的研究提供了新的研究途径,发展形成了腐殖质胶体、有机无机复合体及有机质-异源生物物质复合体的结构模型,在纳米化学水平和三维分子结构模型上重新认识和阐明土壤有机无机复合体的结构和功能;有机无机复合体是土壤改良剂、营养源和重金属或有机有毒污染物过滤器;应在土壤科学、环境科学和生态学中,重视有机物质与矿物质相互作用和结构模型研究,加强土壤有机无机复合体环境化学行为和颗粒迁移动力学的研究。 相似文献
998.
999.
论我国互联网的发展及其潜在空间影响 总被引:34,自引:5,他引:29
互联网是信息化的主要载体。 2 0世纪 90年代以来 ,互联网的发展速度十分惊人 ;用户从少数研究机构及其研究人员迅速扩大到全社会。互联网的普及正在引起日常生活和整个社会经济系统的根本性改变 ,对社会经济空间组织具有深远的意义与影响。本文讨论了互联网时代地理学的意义 ,回顾了我国互联网发展的空间特征 ,并阐述互联网对社会经济空间组织的潜在影响 ;强调互联网对社会经济空间组织影响的两个主要要素 ,即对市场的快速反应与配送的快捷性 ;提出互联网时代地理学在社会经济空间组织上的三个基本研究方向。 相似文献
1000.
阜康典型荒漠C3植物稳定碳同位素值的环境分析 总被引:26,自引:3,他引:23
通过对阜康典型荒漠C3植物稳定碳同位素值的分析。叶片炭同位素值在-23‰和-29‰之间变化,其中主要在-27‰附近波动。这与前人报道的世界上其他地区荒漠植物碳同位素值的变化非常一致。降水可以改变叶片碳同位素值的大小,降水越多,叶片碳同位素值越负,它们的变化幅度有物种的依赖性。叶片碳同位素值也受植物生长形式或期望寿命的影响,木本植物或寿命长的植物叶片碳同位素值要高。分析表明,利用该区土壤或陆相沉积中有机质碳同位素值可以判断气候的干湿变化:土壤或陆相沉积中有机质碳同位素值越高,气候则越干燥。 相似文献