Spatial measurements of stream baseflow,a relevant method for aquifer characterization and permeability evaluation. Application to a hard‐rock aquifer,the Oman ophiolite

The structure, functioning and hydrodynamic properties of aquifers can be determined from an analysis of the spatial variability of baseflow in the streams with which they are associated. Such analyses are based on simple low‐cost measurements. Through interpreting the hydrological profiles (Q = f(A)) it is possible to locate the aquifer(s) linked to the stream network and to determine the type of interrelated flow, i.e. whether the stream drains or feeds the aquifer. Using an analytical solution developed for situations with a positive linear relationship, i.e. where the baseflow increases linearly with increasing catchment size, it is also possible to estimate the permeability of the aquifer(s) concerned at catchment scale. Applied to the hard‐rock aquifers of the Oman ophiolite, this method shows that the ‘gabbro’ aquifer is more permeable than the ‘peridotite’ aquifer. As a consequence the streams drain the peridotites and ‘leak’ into the gabbro. The hydrological profiles within the peridotite are linear and positive, and indicate homogeneity in the hydrodynamic properties of these formations at the kilometre scale. The permeability of the peridotite is estimated at 5 · 10^?7 to 5 · 10^?8 m/s. Copyright © 2004 John Wiley & Sons, Ltd.     

基于GIS的孔隙水文地质层三维空间离散方法

针对自然界中孔隙水文地质层空间分布的不连续性与厚度分布的不均匀性,研究基于GIS的孔隙水文地质层三维空间离散实现的技术路线,提出基于GIS的孔隙水文地质层不规则六面体元的三维空间离散方法.该法不仅能最大限度地保证不规则六面体元中水文地质层类型的一元性,而且可充分利用GIS的空间分析与数据的自动提取功能,快速提取各个计算结点上空间位置坐标与各类计算参数,大大缩短水文地质模型空间离散与相关数据文件组织所需的时间,提高地下水三维有限差分数值模拟的时效性,具有较高的实用价值.     

青藏高原东部表层土壤色度的空间变化特征及其环境意义

认识青藏高原东部现代表土的色度特征及其空间分布,理解其与现代气候因子之间的联系,对于高原地区黄土-古环境重建和揭示第四纪环境变化历史具有重要意义。通过对研究区表层土壤色度的详细分析,对比现代气候资料,探讨了青藏高原东部表层土壤色度的空间变化特征及其环境意义。结果表明：① 高原东部表土色度参数空间变化特征差异显著,表现为随纬度升高,土壤亮度呈先减小后增大的趋势,而红度和黄度则逐步减小;随经度的升高,黄度先增大后减小,而红度值逐步减小;红度和黄度整体随着海拔上升而呈先减小后升高的特征。这些变化特征和差异是表土色度对高原东部复杂地理环境和水热条件变化响应的结果。② 在高原的干旱-半湿润区,土壤亮度对降水的响应敏感;红度和黄度对大尺度的温度变化响应较敏感,而较冷的环境下,红度对温度响应复杂,但与降水存在一定的联系。红度/黄度比值主要指示了气候控制下的赤铁矿和针铁矿的变化和竞争,对干旱-半湿润区域的降水变化响应较为敏感。青藏高原东部现代表土色度与气候密切相关,其空间变化特征一定程度上反映了该地区现代气候因子的空间变化;另一方面由于该区地形和气候复杂多变,部分色度指标与气候关系复杂,在重建青藏高原东部黄土古环境变化历史时需要谨慎。     

基于空间组合特征的农村居民点重构方向识别

农村居民点空间优化重构是推进乡村振兴的重要内容之一。以中国湖北省鄂州市为研究区,从人的生存生活需求出发,构建宜居性评价指标体系,评估鄂州市宜居性高低;通过网络分析法构建城乡人口流动网络,发现乡村人口流动规律。在此基础上,综合宜居性和人口流动强度的组合特征进行农村居民点空间重构。结果表明：(1)鄂州市整体宜居性较高,其中,生存保障功能差距较小,而生活服务功能和生活提升功能差距较大;(2)人口按照主城区、所属镇、附近优势城镇的优先顺序流动;城镇辐射范围有限,现有的点轴结构不能起到以点带面的作用,亟需发展中心村、一般村、基层村形成完整的乡村结构,带动全域发展;(3)基于乡村宜居性和人口流动强度将居民点划分为搬迁撤并类、城郊融合类和集聚提升类(中心村、一般村和基层村)。该研究可重塑乡村发展核心,完善乡村结构,促进资源优化配置,为人口快速流动区乡村聚落重构提供决策依据。     

渤中凹陷西南部古新世—始新世构造差异活动及沉积充填演化

渤海海域渤中凹陷西南部构造复杂,其沉积充填演化规律不明确。综合运用岩芯、测井以及三维地震资料,对该区断陷湖盆古新世—始新世的构造活动、沉积体系以及盆地充填演化规律进行了系统研究。研究表明,渤中凹陷西南部古近纪孔店-沙河街组发育孔店组末期、沙三段末期、沙一二段末期等3期构造活动,多次隆升剥蚀形成3个关键层序界面,控制整个湖盆古近纪孔店-沙河街组的层序结构和古地貌形态。古新世—始新世主要发育近源扇三角洲、辫状河三角洲、湖泊以及湖底扇等4种沉积体系类型,其分布受古物源、古地貌、断裂活动等因素制约。在古新世孔店组沉积裂陷早期,湖盆范围小,物源供给充足,陡坡带和缓坡带均以发育扇三角洲沉积为主,湖盆中心发育湖底扇沉积,晚期湖盆逐渐萎缩;始新世早期的沙三段沉积时期,断陷活动加强,随着盆地范围的扩张,物源供应减弱,湖盆洼陷区主要发育湖底扇沉积。始新世晚期沙一二段裂后沉降期,辫状河三角洲进积特征明显,分布范围广,局部地貌高位置发育湖相碳酸盐岩沉积。不同时期构造差异活动与物源供给共同制约着该区古近纪孔店-沙河街组的沉积充填演化过程,也导致了与渤海海域其他构造区沉积充填的差异性。     

Multicollinearity and correlation among local regression coefficients in geographically weighted regression

Present methodological research on geographically weighted regression (GWR) focuses primarily on extensions of the basic GWR model, while ignoring well-established diagnostics tests commonly used in standard global regression analysis. This paper investigates multicollinearity issues surrounding the local GWR coefficients at a single location and the overall correlation between GWR coefficients associated with two different exogenous variables. Results indicate that the local regression coefficients are potentially collinear even if the underlying exogenous variables in the data generating process are uncorrelated. Based on these findings, applied GWR research should practice caution in substantively interpreting the spatial patterns of local GWR coefficients. An empirical disease-mapping example is used to motivate the GWR multicollinearity problem. Controlled experiments are performed to systematically explore coefficient dependency issues in GWR. These experiments specify global models that use eigenvectors from a spatial link matrix as exogenous variables.This study was supported by grant number 1 R1 CA95982-01, Geographic-Based Research in Cancer Control and Epidermiology, from the National Cancer Institute. The author thank the anonymous reviewers and the editor for their helpful comments.     

Analysis of spatial clustering optimization

Spatial clustering is widely used in many fields such as WSN (Wireless Sensor Networks), web clustering, remote sensing and so on for discovery groups and to identify interesting distributions in the underlying database. By discussing the relationships between the optimal clustering and the initial seeds, a clustering validity index and the principle of seeking initial seeds were proposed, and on this principle we recommend an initial seed-seeking strategy: SSPG (Single-Shortest-Path Graph). With SSPG strategy used in clustering algorithms, we find that the result of clustering is optimized with more probability. At the end of the paper, according to the combinational theory of optimization, a method is proposed to obtain optimal reference k value of cluster number, and is proven to be efficient.     

论《GIS空间分析》课程建设

综述了GIS空间分析理论的相关知识面和知识点,分析了课程的教学适应性,提出了课程建设的几点建议.     

可视化交互空间数据挖掘技术的探讨

随着地理信息获取技术飞速发展,使得当前存储在空间数据库中的空间数据的深度和广度得到了前所未有的发展,传统的空间统计方法和空间分析方法已经难以有效而迅速地处理和分析它们,如何有效而及时地分析和处理空间数据变得越来越迫切。空间数据挖掘作为上个世纪90年代逐步发展起来的新兴技术,逐渐在研究和实践中显示出它的优势。与此同时,地理可视化技术也逐步走向成熟,二者的结合催生出新型空间数据分析技术———可视化交互空间数据挖掘。本文就该技术的相关问题进行了一些研究探讨。     

三维空间实体间拓扑关系的矩阵描述

三维空间实体及其间拓扑关系的语义描述和形式化表达是三维GIS空间数据建模的重要理论基础。在k-维流形的三维空间实体形式化描述方法的基础上,根据三维空间实体的可剖分性,采用顾及维数的九元组描述框架,研究用于构成三维实体的k-单纯形(0≤k≤3)之间的拓扑空间关系,继而研究三维实体间的拓扑空间关系。