Population landscape: a geometric approach to studying spatial patterns of the US urban hierarchy     

Lan Mu  Xiao Wang 《International journal of geographical information science》2013,27(6):649-667

We present a geometric and graphic approach to studying spatial patterns of urban hierarchy in the US. The multiplicatively weighted Voronoi diagram is found to be effective for visualizing theoretical regions delineated by socio‐economic variables. The population landscape of the continental US demonstrates overall and stepwise patterns reflecting population, neighborhood and distance, with overwhelming influence from huge metropolitan areas. Stepwise exploration and cluster analysis of the spatial pattern reveal an urban hierarchy. Attributes and arrangement are the two important factors of urban hierarchy, with attribute having a stronger local influence and arrangement having a stronger global influence. The study also presents a variation of Zipf's law to visualize the rank‐size distribution from tabular and statistical space to map space.  相似文献   

CD-graph: planar graph representation for spatial adjacency and neighbourhood relation with constraints     

Jiaxiang Lin  Jianwei Wu 《International journal of geographical information science》2013,27(10):1902-1923

  相似文献   

Voronoi图和实景影像在城市POI选址中的应用     

邱曼  杜明义  刘扬 《地理空间信息》2013,(3):112-115

以北京西城区为例,通过Voronoi图将兴趣点划分成多个区域;在部件集中且兴趣点少的区域,通过建立基于Voronoi分区的minisum选址模型,得到理论上的新增兴趣点的坐标;然后通过移动道路测量车采集实景影像定位到理论的兴趣点点位上;并在其附近一定范围内寻找最近的有标志意义的地物作为实际位置的兴趣点,达到对兴趣点快速更新的目的,极大提高了城市管理者在日常工作和应对突发事件时的实时性和高效性。  相似文献   

线实体候选匹配集的优化方法研究     

胡天硕  毛政元 《测绘科学》2011,36(2):132-135

地图数据合并是地理空间数据集成的基本途径,同名实体匹配是其中的重点与难点。本文根据线实体的形状将其分为简单线实体与复杂线实体,提出针对前者以线实体端点与中点为发生元生成的Voronoi图所得到的邻近对应关系为依据、针对后者以基于线实体缓冲区重叠度构造的相似性测度指标为依据优化候选匹配集的思路,并设计与实现了相关算法。实证研究表明,该算法能够适应不同比例尺与不同时相的城市道路网地图数据同名实体匹配。  相似文献   

Transmission and visualization of large geographical maps   总被引：1，自引：0，他引：1  

Liqiang Zhang  Liang ZhangYingchao Ren  Zhifeng Guo 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(1):73-80

Transmission and visualization of large geographical maps have become a challenging research issue in GIS applications. This paper presents an efficient and robust way to simplify large geographical maps using frame buffers and Voronoi diagrams. The topological relationships are kept during the simplification by removing the Voronoi diagram’s self-overlapped regions. With the simplified vector maps, we establish different levels of detail (LOD) models of these maps. Then we introduce a client/server architecture which integrates our out-of-core algorithm, progressive transmission and rendering scheme based on computer graphics hardware. The architecture allows the viewers to view different regions interactively at different LODs on the network. Experimental results show that our proposed scheme provides an effective way for powerful transmission and manipulation of large maps.  相似文献   

增/删点后的Voronoi图构造法研究     

史霄  闫浩文  方爱玲  王超超 《测绘与空间地理信息》2011,34(3):44-46

论述了在原Voronoi图的基础上增加点和删去点后生成新Voronoi图的算法.在增点过程中,针对新增加点后不满足Delaunay三角网特性的情况,利用最大最小角规则进行局部优化,根据优化后的三角网生成新Voronoi图;在删点过程中,针对删点的不同位置情况,修改相应Voronoi域,生成新Voronoi图.  相似文献   

基于Voronoi的海洋底质区域划界方法研究     

王涛  陈惠荣  王少帅  魏涛 《测绘与空间地理信息》2011,34(1):242-243

在对Voronoi特性进行分析的基础上,运用Delaunay规则实现了海洋底质数据点的三角网化,从而间接生成了Voronoi图,再经过邻近区域的合并处理得到理想的底质划界区域。  相似文献   

驼背鲈外周血细胞的形态学研究   总被引：1，自引：0，他引：1       下载免费PDF全文

王静香  李加儿  区又君 《海洋科学》2011,35(4):77-82

利用Wright's和Giemsa双重染色法和改良的血涂片染色法两种方式,通过光镜对驼背鲈(Cromileptes altivelis)的血涂片进行了观察.结果表明:驼背鲈的血涂片中可区分出6种细胞--红细胞、嗜中性粒细胞、嗜酸性粒细胞、单核细胞、淋巴细胞、血栓细胞,偶尔可见到分裂的红细胞、分裂的血栓细胞、核影红细胞和...  相似文献   

Biofilm Formation by Microorganisms Isolated from Paper Mill Effluent and its Public Health Implications     

Priyanka Lal  Vishnu Agarwal  Parul Pruthi  Swaranjit Singh Cameotra  Vikas Pruthi 《洁净——土壤、空气、水》2008,36(12):963-968

The microbiological assessment of biofilm formation from paper mill effluent discharged through a pipeline revealed a maximum microbial count for Pseudomonas (5·10⁶ cfu/mL) followed by Staphylococcus (4·10⁶ cfu/mL), Bacillus (8.2·10⁵ cfu/mL), Burkholderia (7.2·10⁵ cfu/mL), Enterobacter (5.3·10⁴ cfu/mL), Acinetobacter (4.1·10³ cfu/mL), Alcaligenes (1.2·10² cfu/mL) and Klebsiella (0.8·10² cfu/mL) species. Among these species, the maximum biofilm formation was observed after 24 h of incubation by Pseudomonas sp. using a crystal violet (CV) assay. This isolate was later identified by 16S rRNA amplification to be Pseudomonas aeruginosa PME1. Extracellular polymeric substances (EPS) of P. aeruginosa PME1 in the biofilm showed a reduction in total carbohydrate content (42%) with increased protein (9.0%), hexosamine (3.0%) and uronic acid (1.7%) content as compared to its planktonic form. Antimicrobial susceptibility testing revealed that P. aeruginosa PME1 biofilms were 17, 24, 27, 30, and 32 times more resistant to cefotaxime, imipenem, ceftazidime, tazobactam and piperacillin, respectively, than their free flowing counterparts.  相似文献   

On reproducing uniform flow exactly on general hexahedral cells using one degree of freedom per surface     

J.M. Nordbotten  H. Hægland 《Advances in water resources》2009

The solution of second order elliptic partial differential equations typically arising for flow problems, e.g., in porous media, is frequently expressed as face fluxes of a flow field at hexahedral cells. In this letter, we show by example that the following properties are incompatible: (1) A local velocity reconstruction, (2) reproduction of uniform flow for general hexahedral cells, and (3) a flow field in H(div). This is in particular relevant to mixed finite element methods approximating H(div), and to other methods trying to reconstruct a flow field in a hexahedron using only local face fluxes, e.g., streamline tracing methods for reservoir simulation.  相似文献