GIS数据库更新模型与方法研究进展

空间数据库更新方法与关键技术研究是近年来国内外GIS的前沿研究课题.本文主要介绍了我国国家自然科学基金重点项目"GIS空间数据库更新的模型与方法研究"的主要研究进展,包括在遥感影像自动配准、地理要素变化信息提取、GIS主数据库增量建模、客户数据库更新等方面取得的研究成果.     

Combined implicit or explicit integration steps for hybrid simulation

Explicit integration procedures have been widely adapted and applied to hybrid simulations of the seismic response of structures due to their simplicity. However, these procedures are only conditionally stable and have limited recent applications of hybrid simulations to simple structural models with few degrees of freedom. A novel integration procedure is proposed herein, in which a fully implicit formulation is applied to solve the equation of motion for the hybrid model, but defaults to an explicit or noniterative formulation in steps that fail to converge. The advantages to this approach are the ensured continuity of the simulation and the reduced accumulation of errors that occur during consecutive explicit steps that may lead to instability. The implicit procedure is applied by loading the experimental substructures beyond the expected displacement for the current step, then using the displacements and forces measured through the load path in the iterative implicit scheme. This approach captures the instantaneous behaviour of experimental substructures without physically imposing iterations. Numerical and experimental simulations demonstrate the effectiveness of the proposed integration scheme for multi‐degree‐of‐freedom models, especially in utilization of longer time steps that exceed stability limits of explicit methods, prevention of excitation of higher modes, and testing of stiff systems. Copyright © 2007 John Wiley & Sons, Ltd.     

CT检测技术在岩石加卸载破坏机理研究中的应用

利用专用的与CT机配套的三轴加载实验设备,采用CT实时试验的手段, 对连续加载试验条件下和卸围压应力作用下砂岩破坏细观机理进行了对比研究. 结果表明, 岩石的卸荷损伤演化破坏具有突发性.     

高精度重力测量的实验研究

在高精度重力测量中，发现同一异常体的实测重力异常与牛顿定律计算出的理论异常不相符，实测异常的极值幅值近２倍于计算异常的极值幅。而且，实测重力异常的极值向两翼衰减很快，其梯度带间距与异常体的水平尺度几乎一致。这就为高精度重力法圈定储油构造、生物礁等平面位置提供了前提。在同等重力测量精度下，实测重力异常比计算重力异常提高了近１倍的纵向分辨力，得到油气藏和油气侵染带引起的重力负异常也是完全可能的。据此用５个模型的实测高精度重力数据和按牛顿定律计算出的数据进行对比，完全证实了上述结论。     

Extraction of real modes and physical matrices from modal testing

A technique to extract real modes from the identifi ed complex modes is presented in this paper, which enables the normalized real mode shapes, modal masses, and full or reduced mass and stiffness matrices to be obtained. The theoretical derivation of the method is provided in detail. An 11-DOF vibration system is used to validate the algorithm, and to analyze the effects of the number of modes utilized and measurement DOFs on the extraction results. Finally, the method is used to extract real modes from bo...     

Substructuring of dynamical systems via the adaptive minimal control synthesis algorithm

In this paper we consider the concept of modelling dynamical systems using numerical–experimental substructuring. This type of modelling is applicable to large or complex systems, where some part of the system is difficult to model numerically. The substructured model is formed via the adaptive minimal control synthesis (MCS) algorithm. The aim of this paper is to demonstrate that substructuring can be carried out in real time, using the MCS algorithm. Thus, we reformulate the MCS algorithm into a substructuring form. We introduce the concepts of a transfer system, and carry out numerical simulations of the substructuring process using a coupled three mass example. These simulations are compared with direct simulations of a three mass system. In addition we consider the stability of the substructuring algorithm, which we discuss in detail for a class of second‐order transfer systems. A numerical–experimental system is considered, using a small‐scale experimental system, for which the substructuring algorithm is implemented in real time. Finally we discuss these results, with particular reference to the future application of this method to modelling large‐scale structures subject to earthquake excitation. Copyright © 2001 John Wiley & Sons, Ltd.     

Accuracy and reliability evaluation of 3D-LS for the discontinuity orientation identification with different registration/georeferencing modes

Abstract

With the aid of three-dimensional laser scanning (3D-LS), a lot of geometric properties of rock discontinuities can be derived from the point cloud data. Due to the complexity of registration and georeferencing of multi-station point data, geological engineers tend to simplify processing by using single-station point data and orienting coarsely. However, there is a lack of accuracy and reliability study in the identification of discontinuity orientations with 3D-LS using different registration/georeferencing modes. In this study, the single-station scanning without registration/georeferencing was applied first to examine the accuracy and reliability of the scanner’s built-in direction system. After that, two types of automated registration/georeferencing modes were examined for the accuracy in rock mass discontinuity analysis. The results show that the dip angle measured by the scanner’s built-in directional system is reliable, accurate and can meet engineering requirements, while the dip direction measured by the scanner’s built-in directional system is unreliable and inaccurate. The dip direction is consistent but inaccurate through the semi-automated registration using natural point features and georeferencing by the scanner’s built-in directional system. Only through real-time kinematic (RTK) registration/georeferencing can the dip direction be reliable and accurate. It is observed that orientations captured by 3D-LS can be more accurate with RTK registration/georeferencing than manual survey.     

RTK与测深联合技术及其在近海工程勘查中的应用

陆上勘查孔位海拔高程的测量工作多采用水准高程传递的方法。海上钻探孔位的海拔高程,由于海洋条件限制,此方法并不适合。为了满足近海工程勘察中测量孔位高程的实际需要,本文采用实时动态差分全球定位系统(GPS-RTK)技术和测深技术,组成RTK和测深仪联合作业系统来测量勘查孔位的标高,在实际近海海洋勘查中取得了良好效果,以便促进RTK技术在海洋工程建设中的应用。     

基于几何特征约束的建筑物点云配准算法

针对人工建筑物表面存在的几何特征关系提出了基于几何特征约束的建筑物点云配准算法,根据点云数据中平面与平面重合关系,推导点在平面上和平面法线平行的2种线性不等约束条件。在6独立参数模型中增加几何特征约束的不等约束条件组成了附有约束条件的配准模型。通过对建筑物3维激光扫描点云数据的采集和处理,详细分析了几何特征约束配准算法的处理结果。试验结果分析表明几何特征约束条件可以合理地改善3维空间转换参数解算结果,提出的配准模型较适合于人工建筑物点云数据的配准。     

房产测绘有关问题探讨

随着房地产市场的发展,房产测绘日益成为社会关注的焦点.从房产测绘的目的和内容方面阐述了房产测绘的定位与管理,就房产测绘的技术标准中的不足及不同标准中的不一致性进行了评述,并指出房产测绘中相关部门应予以的必要协作.