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排序方式: 共有187条查询结果,搜索用时 250 毫秒
61.
化探异常信息识别是化探数据分析最重要的任务之一, 也是化探数据在资源勘查领域受到广泛关注的最重要原因, 前人对化探异常信息识别做过大量研究, 这些研究中的大多数主要关注化探示踪元素的含量, 近而根据含量指标计算异常阈值, 而对示踪元素在空间中的分布特征关注较少。本文选择 1: 20万比例尺的克拉玛依幅为研究区, 根据区内金矿的矿床地球化学特征选择Ag、As、Au和Sb等4种元素为本区内金矿的示踪元素, 以地球化学元素分散晕形成理论为依据, 使用GIS技术和Matlab软件绘制研究区内4种金矿示踪元素的综合地球化学异常图。结果表明, 与传统阈值方法得到的化探异常图相比, 本文得到的化探异常图能够更好地指示研究区内已知金矿。 相似文献
62.
泰森多边形和狄洛尼三角网的林木空间格局分析 总被引:1,自引:0,他引:1
Voronoi图依据地物之间邻近关系对空间进行剖分,Delaunay三角网是Voronoi图的对偶图.文章以单株木为平面点构建Voronoi图和Delaunay三角网,Voronoi图多边形面积表示林木影响范围,Delaunay三角网中每个三角形边长表示对应林木之间距离.在岳阳平江福寿林场设置12块标准地进行试验,计算基于Voronoi图的角尺度、传统的角尺度、基于Delaunay三角网的集聚指数和Voronoi图多边形面积的变异系数,结果表明:这4个指数均能反映样地林木之间的空间分布,变异系数对空间均匀分布和聚集分布有较好的区分度. 相似文献
63.
区域科技资源配置能力的时空分异研究 总被引:1,自引:0,他引:1
科技资源作为第一资源,如何对其进行优化配置是各地区科技管理和科技政策工作的核心问题。根据科技资源的内涵与结构,利用1999-2011年中国31个省市区科技资源的基础数据,在构建区域科技资源配置能力评价指标体系的基础上,科学评价各地区的科技资源配置能力,并利用基尼系数与锡尔指数研究了各地区科技资源配置能力的差异;然后进一步运用探索性空间数据分析(ESDA),直观的反映各个省区科技资源配置能力的的空间集聚特征、集聚类型和显著性水平。结果表明,虽然近年来我国区域科技资源整体配置能力都有了较大提升,但是其区域分布的空间格局并没有根本性的改变;另外,中国科技资源配置能力的空间差异与区域发展的内部差异、区间差异有很大的关系,东部地区的地带内差异是构成区域差异的主要因素。 相似文献
64.
65.
Sea Level Changes Along Bangladesh Coast in Relation to the Southern Oscillation Phenomenon 总被引:1,自引:1,他引:0
Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Niño/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, especially from July to September. Therefore, the sea level variations during the monsoon are of paramount importance to Bangladesh. The results of the present study show that both at Hiron Point and Char Changa there is a substantial difference between the mean tide level during the El Niño and La Niña monsoons. The mean tide level at Hiron Point is higher by about 5 cm during August of La Niña years as compared to that during the El Niño years. The difference at Char Changa, which is located at the mouth of Meghna River, is much higher. This is probably due to the increased fresh water discharge into the Meghna River during La Niña years. Thus at the time of crossing of a monsoon depression, the chances of widespread inundation are higher during a La Nin~a year as compared to that during an El Niño year. The Correlation Coefficients (CCs) between Mean Tide Levels (MTLs) at Hiron Point and Char Changa and the SOI during September (at the end of monsoon) are +0.33 and +0.39 respectively. These CCs are statistically significant at 90% and 95% levels, respectively. These results may find applications in the preparedness programs for combating sea level associated disasters in Bangladesh. 相似文献
66.
用数值模拟的方法探讨了自10 Ma以来喜马拉雅弧形造山带的西构造结及邻区岩石圈的形变和位移变化特征,并采用不同的流变参数和流变结构模拟了前2 Ma内的形变和应力场的演化过程,通过对不同黏性系数、本构关系和初始地壳厚度的改变在演化过程中所起的作用研究表明:(1)采用黏弹性模型时,西构造结区黏性参数的选取对西构造结及邻区隆升高度和隆升范围有重要影响,计算结果给出西构造结区地壳黏性系数应小于1023Pa·s;(2)相对刚性的塔里木盆地采用弹性结构时,对整个西构造结区域的应力和应变场均能引致明显变化;(3)力学性质稳定块体的存在并没有使应力场的传播出现明显的解耦现象. 相似文献
67.
采用等效渗透系数法搜索渗流自由面 总被引:5,自引:1,他引:4
采用一个具体的实例对比分析了当前最为常用的几种自由面确定方法 ,阐明了各自的优缺点 ;然后在此基础上对单元传导矩阵调整法作了简化和改进 ,提出了等效渗透系数法。应用表明 ,等效渗透系数法不仅具有足够的计算精度 ,而且还具备算法简单、易推广等优点 相似文献
68.
A Na‐montmorillonite membrane wastewater renovation prototype system was developed to specifically treat an ionic azo dye. Efficiency of this prototype system was limited to membrane fouling. Fouling rates were not consistently uniform owing to steric effects and competition for exchange sites. The decrease in solute rejection with time can be attributed to the decrease in the relative permeability of the compacted Na‐montmorillonite membrane to the dye with time due to fouling. This decrease occurs probably as a two‐step nucleation–growth mechanism with the nucleation part dependent in part on solvent flux, number of nucleation sites on the membrane, and sorbed mass part that controls solute flux and organic polymerization. The effect of concentration polarization was significant since the flux was higher than the mass‐transfer coefficient. The low diffusion coefficient of the ionic azo dye resulted in low mass transfer coefficients. The most important macromolecular solution properties to be considered for pilot systems may include high concentration‐dependent viscosity, possible non‐Newtonian fluid behavior, and low and concentration‐dependent self‐diffusivity amongst other factors. For pilot systems, the greater the quantity of large macromolecules in the ambient water, the greater the necessity of reducing the permselectivity of the membrane to prevent significant polarization. 相似文献
69.
Kevin W.H. Kwok Kenneth M.Y. Leung Vivien W.W. Bao Jae-Seong Lee 《Marine pollution bulletin》2008,57(6-12):632
The intertidal copeopod Tigriopus japonicus, which is abundant and widely distributed along the coasts of Western Pacific, has been suggested to be a good marine ecotoxicity testing organism. In this study, a series of experiments were conducted to investigate the reproducibility and variability of copper (Cu) sensitivity of T. japonicus so as to evaluate its potential to serve as an appropriate test species. To understand the seasonal variation of Cu sensitivity, individuals of T. japonicus were collected from the field in summer and winter, and subjected to standard 96 h acute (static renewal) toxicity tests. 96 h-LC50 values of T. japonicus collected from the two seasons were marginally different (p = 0.05), with an overall coefficient of variation (CV) of 33%. Most importantly, our results indicated that chronic Cu sensitivity of T. japonicus was highly reproducible. The CVs of intrinsic rates of increase in the population of the control and Cu treatment (10 μg Cu l−1) groups were only 10–11% between 10 runs of a standardised complete life-cycle test. Moreover, different Cu(II) salts generally resulted in a similar 96 h-LC50 value while Cu(I) chloride was consistently slightly less toxic than Cu(II) salts. Given such a high reproducibility of toxic responses, it is advocated to use T. japonicus as a routine testing organism. 相似文献
70.