A method for generating contour tree based on voronoi interior adjacency

A contour tree is a good graphical tool for representing the spatial relations of contour lines and has many applications in map generalization, map annotation, terrain analysis, etc. A new method for generating contour trees by introducing a Voronoi-based interior adjacency concept is proposed in this paper. The immediate interior adjacency set is employed to identify all of the children contours of each contour without contour elevations. It has advantages over existing methods such as the geometric method and the region growing-based method.     

A complete classification of spatial relations using the Voronoi-based nine-intersection model

In this article we show that the Voronoi-based nine-intersection (V9I) model proposed by Chen et al. (2001, A Voronoi-based 9-intersection model for spatial relations. International Journal of Geographical Information Science, 15 (3), 201–220) is more expressive than what has been believed before. Given any two spatial entities A and B, the V9I relation between A and B is represented as a 3 × 3 Boolean matrix. For each pair of types of spatial entities that is, points, lines, and regions, we first show that most Boolean matrices do not represent a V9I relation by using topological constraints and the definition of Voronoi regions. Then, we provide illustrations for all the remaining matrices. This guarantees that our method is sound and complete. In particular, we show that there are 18 V9I relations between two areas with connected interior, while there are only nine four-intersection relations. Our investigations also show that, unlike many other spatial relation models, V9I relations are context or shape sensitive. That is, the existence of other entities or the shape of the entities may affect the validity of certain relations.     

Application of 50 multi-dimensional discrimination diagrams and significance tests: deciphering compositional similarities and differences between Hawaiian and Icelandic volcanism

As an innovative approach, I use multi-dimensional diagrams presented by our group during 2004–2013 and respective probability estimates for the newer diagrams to evaluate similarities and differences between the same magma types (subalkaline basalt, basic magma other than subalkaline basalt, and intermediate magma) from the Hawaiian Islands and Iceland. The known ocean island setting of the Hawaiian Islands was reproduced from these 50 multi-dimensional diagrams for basic, intermediate, and acid magmas. The possible influence of the mid-ocean ridge system on Icelandic magmas was also confirmed from the diagrams for basic rocks. Evaluating magma compositional similarities and differences between the Hawaiian Islands and Iceland was complemented by the application of significance tests. Statistical inferences for the chemical elements and, more importantly, their log-ratios, successfully explained the similarities and differences in the tectonic settings for these two regions.     

Voronoi图和双曲线联合方法在地震快速定位中的应用

基于Voronoi图和地震震中近似满足双曲线分布,提出了一种联合应用V图和双曲线的地震预警快速定位方法.并对青海地震台网记录的地震进行了重新定位处理.研究结果发现,该地震定位方法能满足地震速报的精度要求,在时效性上也可满足地震预警的需要.该方法在地震预警方面有应用前景.     

一种基于Voronoi图的人防警报器空间选址算法

首先通过声学传播原理研究了警报器覆盖范围模型,结合Voronoi图影像范围、最大空心圆策略和平面完全剖分等特性,提出了基于Voronoi图的警报器空间选址算法。文章详细阐述了算法基本思想和流程,最后进行了算法组件设计和系统开发实践。实践表明采用该算法能满足城市警报器合理选址和适当重叠覆盖的要求,并具有其优越性。     

San Diego trough geotechnical test area

Abstract

The San Diego Trough Geotechnical Test Area, located about 24 km southwest of San Diego in a water depth of about 1.2 km, lies near the base of the Coronado Escarpment directly north of the Coronado Fan. A new bathymetric map delineates a shallow basin in the soft, highly plastic, clayey silts flooring the Test Area. Measurements of shear strength by vane and static cone pene‐trometer, and bulk density by nuclear densitometer, were made in place from the submersible Deep Quest. Sixteen short (< 1.6 m) gravity cores were collected from ships.

The geotechnical properties show little areal variation and generally change uniformly with depth within the 55 km² Test Area. Silt is the predominant grain size, averaging about 62%. In‐place bulk density shows little change with increasing depth, values range from 1.23 to 1.26 Mg/m³; laboratory density values increase with depth, ranging from 1.30 to 1.52 Mg/m³ between the surface and a depth of about 1.1 m. The difference between the in place and laboratory values may indicate sampling densification of the cored sediment. Water content in the cores decreases uniformly within the range of 249 to 43% dry weight. Shear strength increases linearly with depth. The laboratory shear strength values are lower than the in place values, which range from 4 kPa at the surface to about 29 kPa at a depth of 3.27 m. Predictor equations relate Atterberg limits, bulk density, water content, and laboratory and in place shear strength to depth. Sedimentation‐compression e log p curves have an equivalent compression index of 1.5 to nearly 2. Excluding rurbidite layers and sampling disturbance effects, all cores indicate a uniform depositional environment in the surface to 1.6 m of sediment sampled. The geotechnical properties indicate that the sediments in the west central and southwest parts of the Test Area exhibit vertical heterogeneity due to thin silt‐sand layers, presumably of turbidity current origin, that originated from the Coronado Canyon.     

城市空间相互作用理论模型的演进与机理

城市空间相互作用理论是城市地理学的重要基础理论。由于城市空间相互作用模型发端于西方,我国这方面的研究相对较晚,主要是引进和实证,在理论研究上还有待深入。本文分析了几种主要城市空间相互作用理论模型的机制和原理,考虑到断裂点模型应用较广,经过了较多的实践验证,重点探讨了该模型的缺陷、演进和扩展形式,从理论上论证了将空间分割原理和断裂点模型结合的扩展模型的科学性和合理性。对城市空间相互作用理论模型的研究,不仅可以为城市规划、城市影响空间和城市经济区的划分以及行政区划调整提供理论基础,而且对物流分析、设施选址、市场影响力的分析等也具有重要的指导作用。从分析城市空间相互作用理论模型演进的过程中还可以得到深刻的启发：地理学以复杂的自然、人文现象为研究对象,是一门边缘学科,又是一门实践性很强的学科。地理学应积极借鉴其他学科最新的理论、技术与方法是十分必要的,是推动其自身发展的关键所在。     

基于网络加权Voronoi图分析的南京市商业中心辐射域研究

道路网络在城市社会和经济活动中发挥重要作用.它是联系商业中心与需求间的桥梁.道路系统的更新与变化必然会对它们的关联产生影响Voronoi图足划分势力空间的有效工具,基于道路网络分析构建的加权Voronoi图可以模拟城市商业中心功能辐射的实际情形.本文给出了基于道路网络分析的Voronoi图和加权Voronoi图构建方法.通过对各种Voronoi图的比较分析,认为基于网络路径时间分析构建的加权Voronoi面域图在商业中心辐射域模拟中最为有效.将空间相互作用和断裂点理论与网络加权Voronoi面域图相结合.模拟不同交通条件下南京市商业中心辐射域空间格局及其需求覆盖变化,并提取了辐射域的覆盖面积、覆盖人口、最远辐射路径距离和平均辐射路径距离等信息.对商业中心的地铁邻近度与其辐射域的扩张面积进行相关分析.采用域邻接矩阵描述空间划分平衡与不平衡之间的相互转变过程,可分析道路系统变更后商业中心之间空间竞争的变化趋势.分析结果表明商业中心的地铁邻近度与辐射域的扩张具有较大的相关性,快速轨道交通在商业中心空间竞争中发挥关键作用.     

Thermodynamical constraints on the crystallization of a deep magma-ocean on Earth

It has been argued that the crystallization of the magma ocean (MO) after the Moon-forming impact led to the formation of a basal magma ocean (BMO). We search which primordial conditions of pressure, temperature and chemical composition could be compatible with such scenario, based on thermodynamical constraints. The major requirement is an early formation of a viscous layer (VL) of mantle material (i.e. bridgmanite (Bg)) at mid lower-mantle depth, which could insulate thermally and chemically the BMO from the rest of the mantle. To produce such VL, Bg grains should be: (i) neutrally buoyant at mid lower-mantle depths, (ii) sufficiently abundant to produce an efficient insulating layer, and (iii) aggregated to the boundary layer from above and below. The first and the second require a large amount of MO crystallization, up to more than 45%, even in the most favorable case of all Fe partitioning into the melt. The latter is very questionable because the Bg grains have a very small settling velocity. We also investigate different scenarios of MO crystallization to provide constraints on the resulting core temperature. Starting from a fully molten Earth, a temperature as high as ～4725 K could be found at the core–mantle boundary (CMB), if the Bg grains settle early atop the CMB. Such a basal layer of Bg can efficiently decouple from each other the cooling rates of the core and the mantle above the VL. If the settling velocity of Bg grains is too low and/or the MO is too turbulent, such basal VL may not form. In this case, the CMB temperature after MO solidification should stabilize at ～4350 K. At this temperature, enough Bg grains are crystallized to make the mushy mantle viscous at any mantle depth.     

等高线空间关系研究

地形图上等高线相互之间的空间关系是人们分析地形的重要依据,也是利用GIS模拟地形图认知能力的一个重要出发点在利用计算机模拟人们判读地形图的过程中面临的一个关键问题是：如何在计算机环境下有效地描述、表达及计算等高线空间关系,本文从空间认知的需求出发,在等高线空间关系分类的基础上,利用图论中的树结构(等高线树)形式化表达等高线空间关系,在Voronoi邻近的基础上建立了计算机可执行的等高线空间关系计算方法。