Scattering of elastic waves by a 3D anisotropic basin

Scattering of elastic waves by a three‐dimensional transversely isotropic basin of arbitrary shape embedded in a half‐space is considered using an indirect boundary integral equation approach. The unknown scattered waves are expressed in terms of point sources distributed on the so‐called auxiliary surfaces. The sources are expressed in terms of the full‐space Green's functions with their intensities determined from the requirement that the boundary and the continuity conditions are to be satisfied in the least‐squares sense. Steady‐state results were obtained for incident plane pseudo‐P‐, SH‐, SV‐, and Rayleigh waves. Using the Radon transform the Green's functions are obtained in the form of finite integrals over a unit sphere or a unit circle which can be numerically evaluated very efficiently. Detailed analysis of the method includes the discussion on the shape of the auxiliary surfaces and the distribution of the collocation points and sources. The convergence criteria is defined in terms of transparency tests, isotropic limit test, and minimization of a certain norm. The isotropic limit tests show excellent agreement with the isotropic results available in literature. For anisotropic materials the numerical results are given for a semispherical basin. The results show that presence of an anisotropic basin may result in significant amplification of surface motion atop the basin. While the amplitude of peak surface motion may be similar to the corresponding isotropic results, the difference in the displacement patterns may be quite different between the two. Therefore, this study clearly demonstrates that material anisotropy may be very important for accurate assessment of surface ground motion amplification atop basins. Copyright © 2000 John Wiley & Sons, Ltd.     

基于OSG的三维GIS功能的封装技术研究与实现

OpenSceneGraph(以下简称OSG)使用OpenGL技术开发,是以C++作为开发语言的应用程序接口(API),它让开发者能快速、便捷地交互式图形程序。在三维GIS领域,使用OSG作为底层渲染是不二之选。本技术研究拟从如何将底层基于OSG使用C++开发的功能进行封装(ActiveX技术),从而对C#和JavaScript等二次开发语言调用等方面进行研究,实现定制化开发和功能扩展,实现应用项目想要的功能。     

基于BIM的复杂钢结构施工放样应用

随着科学技术的不断发展,工程质量的好坏与施工放样大有关联,测量工程与测量仪器也在不断更新,促使施工放样工作越来越简化,精度越来越高。结合某高铁枢纽火车站施工放样项目,详细探讨基于BIM技术的测量机器人智能施工放样的方法。针对异形钢结构钢梁狭窄设站空间受限及钢结构工程施工速度快等问题,阐述了基于测量机器人设站方式及详细的放样方法与步骤,利用移动终端直接在BIM模型上选取放样点,并利用仪器自动追踪功能简化了放样流程。BIM模型与测量机器人的相结合,实现了点位的快速放样,极大的提高了放样效率。     

三维激光扫描技术在城市隧洞形变监测中的应用

三维激光扫描技术具有易操作、高精度、低成本的优势,逐渐广泛的应用于各项工程测绘及监测领域。本文以广东省广州市地铁1号线某段为监测对象,经过两期次监测,通过计算、分析,认为隧洞水平方向最大位移量为6.1 mm,垂直方向最大位移量为2.6 mm,且具有垂直方向形变量大于水平方向形变量的特征。实践表明,将三维激光扫描技术应用于城市隧洞形变监测中,不仅可以获得隧洞整体形变特征,而且能够获得精确的形变量信息,为城市隧洞形变治理提供可靠的依据。     

基于测量数据的机载三维SAR横滚角运动误差补偿

机载三维SAR通过天线阵列、合成孔径和宽带信号实现三维成像,但平台的平动误差和姿态角误差会影响成像质量。不同阵元间的平动误差一致,可通过单天线SAR运动补偿方法去除,但姿态角误差改变阵元间相对位置关系,影响复杂,其中,横滚角误差影响最大,目前尚没有基于测量数据的补偿方法。本文建立了阵列天线SAR三维成像模型,分析了横滚角误差影响及横滚角误差与跨航向波数之间的关系,提出了波数域子孔径补偿方法,仿真结果证明该方法可有效补偿横滚角运动误差影响。     

集成学习支持的复杂地貌类型区土壤全钾含量自适应曲面建模

土壤属性空间分布受复杂地学环境要素影响,空间分异特征十分明显,用单一全局插值模型进行土壤属性模拟,难以实现高精度模拟。对于空间不连续、全局插值模型精度有限及适应性差的特点,本文提出了一种集成学习支持的、融合地学环境变量的土壤属性自适应曲面建模方法（ASM-SP）。利用2013年采集的110个样点数据,使用回归克里金（RK）、贝叶斯克里金（BK）、普通克里金插值法（OK）、反距离加权法（IDW）、ASM-SP,分别对青海湖复杂地貌类型区进行土壤全钾含量的插补。本文采用逐点交叉验证（LOOCV）插值方法模拟精度。结果表明,ASM-SP不仅考虑了地学环境变量与土壤属性的非线性关系,而且融合了多个模型的适应性优势,是实现复杂地貌类型区土壤全钾含量的高精度模拟的一种新方法。     

测井曲线自动识别处理系统的设计与实现

介绍了测井曲线自动识别处理系统的设计实现过程;论述了人机交互,曲线数据处理问题的解决方法;介绍了将沃希变换应用在测井曲线分层中的方法,并给出了相应的实例.     

Modeling of the three‐dimensional subsidence diffusion–convection problem above a trapdoor

In a series of previous works, the plane strain and the axisymmetric cases of the so‐called active trapdoor problem have been modeled by virtue of Litwiniszyn's theory of deep subsidence. However, in reality, there exist trapdoor base geometries—in plan view—which can be very well approximated by an elliptical boundary. Following the elliptical shape of the trapdoor, the contour lines of subsidence also appear to be similar ellipses. In this work, an elliptic model of deep subsidence is presented, the mentioned hypothesis of the self‐similar subsidence contour lines is validated, and finally a simplified model is presented. For completeness of the present three‐dimensional model analysis, a rectangular model is also considered. Results are finally presented and compared with those of plane strain and axisymmetric problems. Some suggestions that have been proposed in previous similar works are also evaluated and compared with the results of the present study. Finally, some estimates are proposed for different trapdoor base geometries. Copyright © 2011 John Wiley & Sons, Ltd.     

A storm event watershed model for surface runoff based on 2D fully dynamic wave equations

The main purpose of this work concerns the development and testing of an overland flow model based on the two‐dimensional fully dynamic shallow water equations. Three key aspects, fundamental to get accurate, efficient and robust computation of surface runoff at basin scale, are discussed by transferring the main findings obtained by the recent research on the topic of dam‐break wave and flood propagation in the context of rainfall–runoff modelling. In particular, attention is focused on the numerical flux and bottom slope source terms computation, on a numerical treatment of friction slope terms and on an algorithm for dealing with wetting/drying fronts. The performances of the numerical model have been preliminarily evaluated using experimental or ideal tests characterized by very critical conditions for the stability of a numerical model. Then, attention was focused on a real event occurred in a sub‐basin of Reno river in Italy to analyse the suitability of the model in simulating real flood situations. The numerical results highlight the good performances of the model in all the simulations discussed in the paper. Copyright © 2012 John Wiley & Sons, Ltd.