基于空间相似性的面实体匹配算法研究

同一地物在不同来源的地图上通常存在着差异,其识别或匹配对于不同数据源的地图编制来说很关键。面状地物要素在很多地图表示中都占有很大的比例。基于人眼综合已有信息来识别同名实体的思想,本文提出了基于空间相似性的面实体匹配算法。该算法将面实体作为一个整体看待,采用加权平均法来综合面实体的位置、形状、大小等特征的相似度,进而根据获得的总相似度大小确定匹配实体。算法在确定位置相似度时选择形状中心点对面实体进行惟一标识;采用形状描述函数来计算形状相似度,不容易受各种干扰而影响精度,避免了形状信息的丢失;面实体的大小通过其覆盖面积来度量。实验结果表明该方法具有良好的稳定性和可靠性。     

多约束的平面点集形状重构方法

针对平面点集空间分布的复杂性,本文提出了一种基于Delaunay三角网的平面点集形状重构方法。首先采用一种简单且实用的数据结构以表达Delaunay三角网中嵌入的几何信息和拓扑信息,然后由外向内迭代过滤Delaunay三角网得到一个大概边界,最后进一步考虑边界的凹凸信息和空洞现象,获取最终的精细边界。试验结果表明与其他典型的Delaunay三角网重构方法相比,本文提出的算法能更好地适用于平面点集空间分布的复杂性,通过所构建的数学模型实现了凸凹多边形内外边界提取。     

不规则形状地下空间开挖条件下地表沉陷预计方法研究

地下工程施工或地下采矿导致地表沉陷，甚至造成突然坍塌或沿层面滑移等灾害事故。文中根据概率积分法的基本原理，基于褶曲构造地层，任意形状空间开挖条件下地表点在任意方向的移动与变形值预计方法，并顾及复杂地质和开挖等因素，推导出不规则形状地下空间开挖条件下地表移动与变形预计公式。由于地表沉陷预计公式都是不可积重积分式，因此，采用数值积分方法解算这些不能求出原函数的方程式和变积分限问题。     

北京市等时间交通圈的范围、形态与结构特征

不同层次和范围的交通圈是经济社会空间组织的重要依据。本文运用网络分析与成本加权距离集成算法,设计了定量界定交通圈的技术路线。在此基础上,以通勤便捷为目标,提出1小时交通圈内部圈层的划分方法和轨道交通服务指数,据此分析了北京1小时交通圈的内部层次和结构特征;以经济分工协调为目标,基于时空距离与交通方式,划分北京一日交通圈的圈层,并提出交通廊道的界定方法,据此探讨了北京一日交通圈内部各廊道地区的空间范围与经济基础。结果显示：北京市等时间交通圈的形态受高速交通影响较大,具有显著的偏向式延伸特点,并在边缘地带形成少量“岛”;轨道交通对北京市1小时交通圈的支撑力度较弱,未来应加强重点方向的轨道交通建设;根据各廊道的具体情况,京津廊道、京唐廊道是京津冀协同发展的重要载体,京石廊道宜定位为承接北京地区产业转移的重点地区,京承廊道与京张廊道则适宜发展生态型经济。     

Segmentation of contacting soil particles in images by modified watershed analysis

Image-based soil particle size and shape characterization relies on computer methods to process and analyze the images. For contacting particles spread on a flat surface this requires delineation of particle boundaries through shape-based image segmentation. The traditional method using watershed analysis fails for particles that have constrictions (are peanut-shaped). The oversegmentation interprets such particles as being two, thereby underestimating the long particle dimension by about 50% and overestimating particle sphericity by about a factor of two. This paper presents a solution to the problem of oversegmentation through morphologic reconstruction. The key to this improvement is distinguishing the necks in peanut shaped particles from actual contacts between particles. A parameter α is defined to quantify the necks and contacts. Approximately 220,000 particles in a range of 2.0–35.0 mm having various shapes and angularities were studied to find typical α values for necks and contacts. An algorithm is proposed to correct the oversegmentation based on α. The results show that this improved watershed analysis accurately segments sand particles at contacts while preserving the continuity of peanut shaped particles. Example lab tests demonstrate the significance of the problem and its solution.     

潘庄区块煤层气U型水平井下套管技术探讨

下入生产套管的煤层气U型井具有产气量高、成本低的优点,逐渐成为潘庄区块煤层气开发的主要井型。潘庄区块煤层埋深一般在500 m以浅,同时要求U型井的水平段在1000 m左右,生产套管的下入成为该区块垂深浅、水平段长的煤层气U型井的技术难题,经过多口井试验,优化钻井轨迹的平滑度,采用原钻具、短螺旋扶正器和生产套管内置钻铤3次划眼,以及严格控制下套管程序,可提高套管一次性下入的成功率,并提高生产效率。     

True orthoimage generation by mutual recovery of occlusion areas

Demand for orthoimages is increasing as a crucial component of geographic information systems (GISs). Orthoimages are geometrically equivalent to planimetric maps, which show true geographic locations of terrain features. To produce orthoimages, geometric distortions from camera tilt and relief displacement from perspective images must be corrected. Traditionally, removing such distortions has been accomplished by differential rectification in a pixel-by-pixel fashion. However, this method cannot produce true orthoimages because of the double-mapping problem. We propose a method of generating patch-based true orthoimages for surface patches in buildings. The proposed method utilizes three-dimensional (3D) building model data. Patches from the data were projected onto aerial images to extract image patches and analysis of the superstructures was performed. Because orthoimages are generated for each building, the orthoimage quality is enhanced when using building data with a high level of detail. Instead of performing the complex visibility analysis of existing approaches, this article identifies occlusion areas based on unit surfaces of buildings and presents mutual recovery of occlusions using multiple images. To evaluate the feasibility of the method, experiments were performed with real datasets: (1) a building with a dome superstructure, (2) high-rise buildings close to each other, and (3) buildings with various shapes.     

基于降水微物理特征测量仪的雨滴形状观测与分析

利用自主研制的降水微物理特征测量仪开展降水观测试验,得到了大量的雨滴图像。研究了异常雨滴图像的形成原因和处理方法,以此为基础重点研究了在极坐标下基于Akima插值的数字雨滴图像矢量化方法,得到了雨滴平均形状特征和轴比分布特征。结果表明,直径小于1 mm的雨滴以圆形为主,在1.0~3.0 mm的雨滴以椭圆形为主,大于3.0 mm的雨滴逐渐呈现顶部凸起,底部偏平的形状;雨滴的平均轴比分布与经验分布一致,相互之间差异在±0.04 mm范围以内;雨滴的平均轴比与经验模型的差值在粒径3.4~3.8 mm出现峰值,该范围内的雨滴较经验关系具有更圆的形状特性。     

基于不变性矩特征的人工神经网络2-D形状识别

在2—D不变性矩快速计算的基础上，利用人工神经网络，使用不变性矩完成2—D形状的识别。实验结果与现有文献的结果比较，本文采用的方法具有特征数目少、意义统一、识别快速、准确的特点。