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131.
针对地铁建设中典型的马蹄形断面隧道建立比例尺为1∶20的分析模型,并采用数值分析方法研究马蹄形隧道处于单一土层及工程所处区域典型的成层土体中时的动力响应。分析结果表明,在单一土层中由于土体的约束作用,结构产生的位移以整体沉降为主,在成层土体中除产生一定的整体变形外还伴随一定的扭转变形。在两种地层情况下马蹄形地铁隧道在地震动力作用下的动力加速度响应、竖向位移均在拱顶处产生最大值,其中在单一土层中的加速度响应最大值为结构中部加速度的2.29倍。结构在顶部和侧板处所产生的动应力响应值也较大。研究表明,地震动力荷载作用下顶板、侧板均为受力较大部位,在设计和施工中应予以充分重视。 相似文献
132.
文章借助弹性薄板理论,建立地表沉陷变形的预计模型,并给出任意点地表变形的预计表达式。针对地下开挖空间形状的不规则性,推导出了水平空间、倾斜面空间以及不规则开挖空间:椭圆抛物面空间、二次柱面空间以及二次曲面空间地表沉陷的预计公式。本文的研究结果对该类开采沉陷问题的研究具有一定指导意义。 相似文献
133.
J. C. Hinton 《International journal of geographical information science》2013,27(7):877-890
Abstract The combined use of remotely-sensed images and vector GIS data has received considerable interest in recent years. This review article discusses the historical move towards closer integration of remote sensing and GIS technologies and the requirements of integrated software systems to enable remotely-sensed data to be combined with vector datasets for maximum effect. The benefits of integration to users of both GIS and remote sensing for environmental applications are reviewed and some thoughts are given on terminology and future directions in this field. 相似文献
134.
Hongxing Liu Lei Wang Douglas Sherman Yige Gao Qiusheng Wu 《International journal of geographical information science》2013,27(7):1015-1041
This article presents an object-based conceptual framework and numerical algorithms for representing and analyzing coastal morphological and volumetric changes based on repeat airborne light detection and ranging (LiDAR) surveys. This method identifies and delineates individual zones of erosion and deposition as discrete objects. The explicit object representation of erosion and deposition zones is consistent with the perception and cognition of human analysts and geomorphologists. The extracted objects provide ontological and epistemological foundation to localize, represent, and interpret erosion and deposition patches for better coastal resource management and erosion control. The discrete objects are much better information carriers than the grid cells in the field-based representation of source data. A set of spatial and volumetric attributes are derived to characterize and quantify location, area, shape, orientation, depth, volume, and other properties of erosion and deposition objects. Compared with the conventional cell-by-cell differencing approaches, our object-based method gives a concise and high-level representation of information and knowledge about coastal morphological dynamics. The derived attributes enable the discrimination of true morphological changes from artifacts caused by data noise and processing errors. Furthermore, the concise object representation of erosion and deposition zones facilitates overlay analysis in conjunction with other GIS data layers for understanding the causes and impacts of morphological and volumetric changes. We have implemented a software tool for our object-based morphological analysis, which will be freely available for the public. An example is used to demonstrate the utility and effectiveness of this new method. 相似文献
135.
Change detection with remotely sensed imagery plays an important role in land cover mapping, process analysis and dynamic information services. Euclidean distance, correlation and other mathematic metrics between spectral curves have been used to calculate change magnitude in most change detection methods. However, many pseudo changes would also be detected because of inter-class spectral variance, which remains a significant challenge for operational remote sensing applications. In general, different land cover types have their own spectral curves characterized by typical spectral values and shapes. These spectral values are widely used for designing change detection algorithms. However, the shape of spectral curves has not yet been fully considered. This paper proposes to use spectral gradient difference (SGD) to quantitatively describe the spectral shapes and the differences in shape between two spectra. Change magnitude calculated in the new spectral gradient space is used to detect the change/no-change areas. Then, a chain model is employed to represent the SGD pattern both qualitatively and quantitatively. Finally, the land cover change types are determined by pattern matching with the knowledgebase of reference SGD patterns. The effectiveness of this SGD-based change detection approach was verified by a simulation experiment and a case study of Landsat data. The results indicated that the SGD-based approach was superior to the traditional methods. 相似文献
136.
三维地质建模和可视化概念最早是由加拿大Houlding在1993年提出的。三维地质建模是指采用适当的数据结构在计算机中建立能反映地质构造的形态和各要素之间的关系以及地质体物理、化学属性空间分布等地质特征的数学模型。Minexplorer软件集高效快捷、地质分析自动化、二维GIS制图与三维可视化为一体,能对原始勘探资料和地质编录成果数字化,有效管理、分析地质勘探多元数据,可构建理想的三维勘探辅助决策模型,科学计算矿床资源储量、实现储量动态管理和计算机辅助制图。 相似文献
137.
基于傅里叶描述子的高分辨率遥感图像
地物形状特征表达 总被引:1,自引:1,他引:0
本文在对傅里叶描述子进行归一化的基础上, 将该方法引入地物轮廓的形状特征描述中, 针对建筑物、
农田、道路和河道4 种典型地物, 分别从谱线特征、不同频段描述子对形状特征的贡献率、形状重构三个方面进行
分析, 结果表明, 在谱线图中, 直流分量对形状特征的贡献率在70%以上, 低频和高频成分共占7%—24%左右, 中
频成分的贡献率只有2%—4%左右, 仅低频成分(第1—5 项)便能够很好地进行地物形状重构。最后将第1—5 项描
述子应用到基于决策树的面向对象分类中, 得出实验区总体分类精度为98.48% 相似文献
138.
The seismic response of a multi‐span continuous bridge isolated with novel superelastic‐friction base isolator (S‐FBI) is investigated under near‐field earthquakes. The isolation system consists of a flat steel‐Teflon sliding bearing and a superelastic NiTi shape memory alloy (SMA) device. The key design parameters of an S‐FBI system are the natural period of the isolated bridge, the yielding displacement of the SMA device, and the friction coefficient of the sliding bearings. The goal of this study is to obtain optimal values for each design parameter by performing sensitivity analysis of a bridge isolated by an S‐FBI system. First, a three‐span continuous bridge is modeled as two‐degrees‐of‐freedom with the S‐FBI system. A neuro‐fuzzy model is used to capture rate‐ and temperature‐dependent nonlinear behavior of the SMA device. Then, a set of nonlinear time history analyses of the isolated bridge is performed. The variation of the peak response quantities of interest is shown as a function of design parameters of the S‐FBI system and the optimal values for each parameter are evaluated. Next, in order to assess the effectiveness of the S‐FBI system, the response of the bridge isolated by the S‐FBI system is compared with the response of the non‐isolated bridge and the same bridge isolated by pure‐friction (P‐F) sliding isolation system. Finally, the influence of temperature variations on the performance of the S‐FBI system is evaluated. The results show that the optimum design of a bridge with the S‐FBI system can be achieved by a judicious specification of design parameters. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
139.
140.