常规数码影像辅助的大比例尺数字测图

完整而准确地记录绘图信息,是目前主流数字测图作业模式中,最影响工作效率和劳动强度,并容易出现错漏的一项工作。针对这一问题,提出了一种借助常规数码影像记录相关信息辅助数字测图的方法。实验证明,该方法可以显著降低在地形复杂地区外业绘制草图和记录属性等的难度和工作量,有效减少内业编辑成图的错误。     

斑点抑制与多分辨率拓扑分析相结合的SAR图像河流水体提取

针对由于斑点噪声和建筑遮挡造成的高分SAR图像河流水体提取的不连续问题,本文提出一种结合自适应斑点抑制和多分辨率拓扑分析的河流水体提取方法。首先,在斑点抑制各向异性扩散中引入Beta度量以实现SAR图像的自适应滤波;其次,利用局部阈值分割和连通域标识对去噪图像中的河流水体段进行快速提取;然后,以河流水体段的最小外接凸多边形为对象构建高斯金字塔,并由此进行多分辨率拓扑分析来获得河流间断点信息;最后,由区域生长策略逐层地对间断点进行判别,实现相邻河流水体段的自动连接。采用TerraSAR-X和GF-3高分SAR图像验证提出的方法。结果表明,该方法可有效地提取完整河流水体。对多幅SAR图像提取结果的定性和定量评价验证了提出方法的有效性与稳健性。     

设计相关动载荷作用下的水下耐压结构拓扑优化

常规耐压结构拓扑优化设计研究主要集中于静水压条件下的设计相关载荷拓扑优化理论及方法。但是,在深海环境下,耐压结构可能面临内爆所产生的冲击载荷,其载荷呈现高频率的周期性变化。为研究载荷变化对耐压结构优化设计的影响,在BILE模型的基础上,结合修正的SIMP插值模型,开展不同频率、设计相关动载荷作用下的水下耐压结构拓扑优化理论及方法研究。设计相关动载荷的难点在于不仅载荷的作用位置和方向在优化过程中发生变化,且其大小也随优化过程进行而发生变化,这是与常规设计相关静载荷本质的不同。通过经典的拱形结构优化算例验证BILE模型在动力学拓扑优化中的可行性,进而研究设计相关动载荷作用下的水下耐压结构的最佳拓扑形式。研究表明,在低频时,圆环型耐压结构无明显变化,但多球交接耐压结构在交接处会出现明显材料聚集;高频时,两者均发生明显变化,得到耐压结构新形式。关于设计相关动载荷作用下的水下耐压结构拓扑优化研究,将对新型水下耐压结构的探索具有一定的工程应用价值。     

Topologically Safe Curved Schematisation

Abstract

Traditionally schematised maps make extensive use of curves. However, automated methods for schematisation are mostly restricted to straight lines. We present a generic framework for topology-preserving curved schematisation that allows a choice of quality measures and curve types. The framework fits a curve to every part of the input. It uses Voronoi diagrams to ensure that curves fitted to disjoint parts do not intersect. The framework then employs a dynamic program to find an optimal schematisation using the fitted curves. Our fully-automated approach does not need critical points or salient features. We illustrate our framework with Bézier curves and circular arcs.     

A graph-based algorithm to define urban topology from unstructured geospatial data

Interpretation and analysis of urban topology are particularly challenging tasks given the complex spatial pattern of the urban elements, and hence their automation is especially needed. In terms of the urban scene meaning, the starting point in this study is unstructured geospatial data, i.e. no prior knowledge of the geospatial entities is assumed. Translating these data into more meaningful homogeneous regions can be achieved by detecting geographic features within the initial random collection of geospatial objects, and then by grouping them according to their spatial arrangement. The techniques applied to achieve this are those of graph theory applied to urban topology analysis within GIS environment. This article focuses primarily on the implementation and algorithmic design of a methodology to define and make urban topology explicit. Conceptually, such procedure analyses and interprets geospatial object arrangements in terms of the extension of the standard notion of the topological relation of adjacency to that of containment: the so-called ‘containment-first search’. LiDAR data were used as an example scenario for development and test purposes.     

基于三角网构建海底DEM的抽稀算法

为压缩海量水深数据,实现在高分辨率下快速、完整和准确地表示海底地形,提出了一种基于三角网拓扑结构的数据抽稀方法。该方法利用Delaunay三角网的模型优势,快速寻找与水深点相关的区域。根据水深点对区域贡献度大小决定取舍。实验表明,该方法充分顾及海底地形变化趋势,能有效识别海底地形特征点,并且抽稀速度快、失真小、精度高。     

基于增量信息的空间数据质量检查——以线目标为例

GIS数据质量是GIS数据更新、信息查询与分析的基础;增量更新是当前空间数据库更新领域研究的热点,基于增量信息的数据质量检查是增量更新的一项重要研究内容。深入分析了基于增量信息的线状数据局部质量检查的内容、局部数据的确定及拓扑质量检查规则;对线状矢量数据局部拓扑质量检查进行设计,并在原型系统增量采编系统中采用Visual C#实现了线状矢量数据的局部拓扑质量检查功能,最后通过实验验证了基于增量信息的局部质量检查相对于传统全局质量检查的高效性,对目前人工检查或半自动化低效率的检测方法的改进具有一定的指导性意义。     

基于模拟退火算法的供水管网抗震优化设计

本文以管网造价为优化目标,管网拓扑结构为优化参数,管网节点最低可靠度为约束条件,建立了供水管网抗震拓扑优化模型。在供水管网功能可靠性分析方法的基础上,结合单元概率重要度分析方法,利用模拟退火算法提出了供水管网的抗震拓扑优化方法,并对一典型供水管网进行了拓扑优化分析。分析表明,对于管网抗震拓扑优化这样一个组合优化问题,模拟退火算法提供了一类很好的途径,以此为基础进行供水管网抗震可靠性优化设计具有很好的效果。     

Simultaneous topology and sizing optimization of viscous dampers in seismic retrofitting of 3D irregular frame structures

A new methodology for performance‐based optimal seismic retrofitting using a limited number of size groups of viscous dampers is presented. The damping coefficient of each size group of dampers is taken as a continuous variable and is determined by the optimization algorithm. Furthermore, for each potential location, a damper of a single size group is optimally assigned, if any. Hence, the formulation presents a large step forward towards practical optimal design of dampers. The key for achieving an efficient optimization scheme is the incorporation of material interpolation techniques that were successfully applied in other structural optimization problems of discrete nature. This results in a very effective optimization methodology that is expected to be very efficient for large‐scale structures. The proposed approach is demonstrated on several example problems of 3D irregular frame structures. Copyright © 2014 John Wiley & Sons, Ltd.