基于道路网络分析的Voronoi面域图构建算法

提出一种基于网络分析的Voronoi面域图和加权Voronoi面域图构建算法。鉴于道路网络在城市中心地、公共设施引力传导与功能覆盖上的重要作用,采用网络最短路径距离分析和最短路径时间分析构建的Voronoi面域图可以模拟出中心功能的辐射影响范围空间划分的实际情形,进而为空间分析和空间优化提供有力支持。算法过程主要包括:设施邻近道路结点检索和分界结点计算;基于网络最短路径分析Dijkstra算法和分界结点计算的网络Voronoi划分;基于空间离散化、邻近道路分析的空间Voronoi划分及其矢量化处理算法。计算实验结果表明本文提出算法可靠和高效,能够模拟出具有预期精度和形态复杂的网络Voronoi面域图形。     

第二次农村土地调查技术与实践

第二次土地调查工作,包括农村土地调查和城镇土地调查两部分,是一项统一由政府组织实施的重大任务。结合生产实践阐述了基于遥感影像建立影像解译标志,并在GIS软件上解译影像信息,采用内外业相结合方法,全面掌握城镇、村庄以及独立工矿区内部工业用地、基础设施用地、住宅用地以及农村宅基地等行业用地、农用地、未利用地的数量和分布,并建立土地利用现状数据库的过程。     

TIN中边侧向关系在三角形定位、Voronoi图和等值线生成等算法中的应用

使用一种含有边拓扑关系的TIN数据结构,从三角网的拓扑关系角度利用这种结构中的边拓扑关系设计了三角形定位、Voronoi图生成和等值线生成的算法.这些算法避免了在三角形中拓扑关系查询时的不必要的搜索.更重要的是,在算法的编写过程中,如果避免一些不必要的搜索,则意味着算法更加清晰,并减少了出错的机率.经过上机验证,三种算法都获得了正确、满意的结果.     

New measurement of melting and thermal conductivity of iron close to outer core conditions

The amount of literature on both melting and thermal conductivity of iron at Earth’s core conditions is overwhelming and the discrepancies are very large.There is a broad range of experimental techniques each of which is flawed to a certain degree,which may explain the discrepancy.In this report,we present new data using a different method for determining the phase behavior and resistivity of iron in the laser-heated diamond cell by measuring the electrical resistance of both solid and liquid iron wires.The experiment avoids some of the major flaws of previous experiments,the most important of which is the detection of the onset of melting.These measurements confirm a shallow melting curve found earlier and the resistivity data imply a trend towards low thermal conductivity in the liquid outer core.     

Preliminary study on strontium-rich characteristics of shallow groundwater in Dingtao Area,China

Based on the analysis of element correlation, the Gibbs diagram, hydro-geochemical ion ratios, isoline maps of groundwater and soil, and change patterns of strontium content after normalization, the study examines water-rock interaction of shallow groundwater in Dingtao area. The results suggest that strontium in the study area mainly comes from water-rock interactions, and the strata interacting with groundwater are the top of Quaternary and Neogene. The element correlation analysis shows that the formation of strontium-rich groundwater is sufficiently affected by sulfate and carbonate. The Gibbs diagram suggests that the chemical composition of groundwater is mainly influenced by water-rock interactions, accompanied by evaporation crystallization. c(Ca²⁺+Mg²⁺)/c(HCO₃^-+SO₄^2-) reflects that the main reactions in the groundwater system is weathering dissolution of carbonate and sulfate, and ion exchange takes place. c(Na⁺)/c(Cl^-) indicates that Na⁺ in groundwater may have water-rock interactions with rocks it flows through. c(Cl^-)/c(Ca²⁺) indicates that the hydrodynamic condition in the pumping well is poor and the water circulation is slow. The study examines the macro isoline map change patterns, correlation curves of change of strontium content in groundwater and shallow soil, and correlation curves of change of strontium content in groundwater, shallow soil, and deep soil. The results suggest that the strontium content in the study area has the same change pattern in groundwater and in soil, which further indicates that strontium in the study area comes from water-rock interactions.     

恒星形成时期强远红外源的红外发射与赫罗图

本文从IRAS点源星表（PSC）中选择了一批流量只F100μ≥500Jy，且属于正在形成或早期演化阶段的强远红外源，利用北京天文台兴隆观测站的1.26m红外望远镜，对这批源进行了J、H、K波段的近红外观测，得到了12个源的第一次J、H、K测光资料．结合外台站的红外观测资料和IRAS点源星表数据，我们对强远红外源的红外发射进行了修正的黑体光球模型、双壳层尘埃发射模型以及详细的辐射转移等模型的拟合，得到了这些源的一系列重要的物理参量，如中心星的等效光球温度，近红外消光以及包层的尘埃温度和密度随半径变化的幂律等．本文利用红外导出的中心星光球温度和光度，得到了与这些强远红外源成协的大质量年轻天体在赫罗图上的位置和演化特征．我们发现，对质量一定的大质量年轻星，沿着向主序演化的方向，红外谱在12μ－60μ间的斜率S有逐渐增大的趋势；而对演化到同一时间线的星，随着质量的增大，S也有增大的趋势．本文分析了这一性质．并提出了利用红外资料研究赫罗图的方法，它是一种研究深埋于分子云和尘埃包层的大质量年轻星早期演化的有效方法．     

一种基于Voronoi多边形的海底底质表示方法

海底底质对舰船航行、锚泊、登陆、铺设海底管线等海上活动具有重要的影响。文中提出了一种基于同质Voronoi多边形的海底底质分布可视化方法。通过构建Delaunay三角网,求取Voronoi多边形顶点,并依次排序顶点,从而生成构成Voronoi图。在Voronoi图的基础上,提出了同底质Voronoi多边形合并的具体算法,并处理与岸线相交的区域。实验表明,文中所提方法对于海底底质分布的可视化表达,比传统方法更为形象、直观。     

基于Voronoi图的遥感影像校正地面控制点选取

遥感影像几何校正时要求选取的地面控制点应尽可能在整幅影像内均匀分布,而对于均匀分布的理解主观性较强。本文运用Voronoi图控制地面控制点的均匀分布,并建立了控制点的分布与数量的联系,使选取的地面控制点分布均匀,且数量足够。实验证明,用Voronoi图控制地面控制点的均匀分布,是提高遥感影像多项式几何校正精度的有效途径。     

基于空间关系的海上应急救援力量调度模型

本研究以Voronoi图为研究工具,对普通Voronoi图在海上救援应用中的局限性进行分析,并对其进行了合理改进,提出了“海上救援V图”。同时,结合模糊层次分析法和引力模型方法计算各海事机构救援力量的“吸引力”权重矩阵,提出了基于Voronoi图的海上救援调度模型。最后,结合具体救援案例,构建了基于Voronoi图的海上应急救援模型MRSV。实验结果表明：该模型能够在顾及海上特殊地理环境以及要素间空间关系的基础上,综合考虑各海事机构的救援力量,针对不同海难情况,选调合适的救援机构,调度结果合理,能够达到优化救援力量配置的目的,可以为目前海上应急救援力量调度提供参考。     

Comparative analysis of predictive methods for drought durations: a case of monthly and annual streamflow droughts in Atlantic Canada

Methods based on the recursive probability, the extreme number theorem, and Markov chain (MC) concepts were applied to predict drought lengths (duration) on the standardized (termed as standardized hydrological index, SHI) sequences of monthly and annual river flows from Atlantic Canada. Results of the study indicated that the MC-based method is the most efficient, reliable and versatile method for predicting drought durations followed by the extreme-number-based method. The recursive-probability-based method was found to be computationally intensive and less efficient, although it provided a powerful means for calibrating the empirical plotting position formula needed in the MC-based method. The Weibull plotting position formula turned out to be a suitable measure of the exceedance probability in MC methodology for predicting drought lengths in Atlantic Canada. Based on results, it can be inferred that the MC-based method can be extended to MC2 and higher-order chains for predicting drought lengths on SHI sequences. The predictive capability of the extreme-number-theorem-based method is limited only to independent or weakly first-order persistent SHI sequences.

EDITOR D. Koutsoyiannis

ASSOCIATE EDITOR Q. Zhang