Accessibility Measures in Spatial Mismatch Models     

Eugene D. Perle  Harald Bauder  Nancy Beckett 《The Professional geographer》2002,54(1):106-110

Implicit in all spatial mismatch models is the concept of accessibility. However, there is an immense variety of measures utilized in the literature to index the concept, and it is not clear how much of the disparity in findings between studies is attributable to alternative measures. This research note attempts to provide some evidence on the impact of alternative measures of accessibility in employment probability models.  相似文献   

大河三角洲河口海岸演化机理模型研究:(II)模型构建与实证     

王凯  李国胜  方国洪  李柏良 《地理研究》2003,(2)

本文以z坐标下的三维斜压海洋动力学数值模式为基本模式原型 ,在整理渤海基本数据并诊断计算风生环流和热盐环流作为背景环流场基础上 ,初步建立了渤海海域动力环境数值模式。模式采用了经校正的Bagnold型方程来计算渤海底移质沉积物输运 ,悬移质计算则是取二维深度平均悬移质输运方程和河床变形方程 ,计算含沙量分布以及由悬移物引起的冲淤厚度。利用这种方法建立的沉积物输运模式 ,定量模拟了渤海沿岸和海底的沉积物输运方向和冲淤分布。模拟结果与通过多年实测水深估算获得的渤海海底沉积物的冲淤变化分布相比较 ,两者之间在基本结论上是比较一致的  相似文献   

Use of Noise to Augment Training Data: A Neural Network Method of Mineral–Potential Mapping in Regions of Limited Known Deposit Examples     

Warick M. Brown  Tamás D. Gedeon  David I. Groves 《Natural Resources Research》2003,12(2):141-152

One of the main factors that affects the performance of MLP neural networks trained using the backpropagation algorithm in mineral-potential mapping isthe paucity of deposit relative to barren training patterns. To overcome this problem, random noise is added to the original training patterns in order to create additional synthetic deposit training data. Experiments on the effect of the number of deposits available for training in the Kalgoorlie Terrane orogenic gold province show that both the classification performance of a trained network and the quality of the resultant prospectivity map increasesignificantly with increased numbers of deposit patterns. Experiments are conducted to determine the optimum amount of noise using both uniform and normally distributed random noise. Through the addition of noise to the original deposit training data, the number of deposit training patterns is increased from approximately 50 to 1000. The percentage of correct classifications significantly improves for the independent test set as well as for deposit patterns in the test set. For example, using ±40% uniform random noise, the test-set classification performance increases from 67.9% and 68.0% to 72.8% and 77.1% (for test-set overall and test-set deposit patterns, respectively). Indices for the quality of the resultant prospectivity map, (i.e. D/A, D × (D/A), where D is the percentage of deposits and A is the percentage of the total area for the highest prospectivity map-class, and area under an ROC curve) also increase from 8.2, 105, 0.79 to 17.9, 226, 0.87, respectively. Increasing the size of the training-stop data set results in a further increase in classification performance to 73.5%, 77.4%, 14.7, 296, 0.87 for test-set overall and test-set deposit patterns, D/A, D × (D/A), and area under the ROC curve, respectively.  相似文献   

Use of Fuzzy Membership Input Layers to Combine Subjective Geological Knowledge and Empirical Data in a Neural Network Method for Mineral-Potential Mapping   总被引：3，自引：0，他引：3  

Brown  Warick  Groves  David  Gedeon  Tamás 《Natural Resources Research》2003,12(3):183-200

Use of GIS layers, in which the cell values represent fuzzy membership variables, is an effective method of combining subjective geological knowledge with empirical data in a neural network approach to mineral-prospectivity mapping. In this study, multilayer perceptron (MLP), neural networks are used to combine up to 17 regional exploration variables to predict the potential for orogenic gold deposits in the form of prospectivity maps in the Archean Kalgoorlie Terrane of Western Australia. Two types of fuzzy membership layers are used. In the first type of layer, the statistical relationships between known gold deposits and variables in the GIS thematic layer are used to determine fuzzy membership values. For example, GIS layers depicting solid geology and rock-type combinations of categorical data at the nearest lithological boundary for each cell are converted to fuzzy membership layers representing favorable lithologies and favorable lithological boundaries, respectively. This type of fuzzy-membership input is a useful alternative to the 1-of-N coding used for categorical inputs, particularly if there are a large number of classes. Rheological contrast at lithological boundaries is modeled using a second type of fuzzy membership layer, in which the assignment of fuzzy membership value, although based on geological field data, is subjective. The methods used here could be applied to a large range of subjective data (e.g., favorability of tectonic environment, host stratigraphy, or reactivation along major faults) currently used in regional exploration programs, but which normally would not be included as inputs in an empirical neural network approach.  相似文献   

Partial melt or aqueous fluid in the mid-crust of Southern Tibet? Constraints from INDEPTH magnetotelluric data   总被引：13，自引：0，他引：13  

Shenghui Li  Martyn J. Unsworth  John R. Booker  Wenbo Wei  Handong Tan  Alan G. Jones 《Geophysical Journal International》2003,153(2):289-304

  相似文献   

模糊区域拓扑关系模型   总被引：4，自引：1，他引：4  

唐新明  方裕  Wolfgang Kainz 《地理与地理信息科学》2003,19(2):1-10

拓扑关系是地理信息系统中空间要素之间最基本也是最重要的关系之一，是进行绝大多数空间查询和分析的基础。非模糊空间要素之间的拓扑关系在一般拓扑学等理论的基础上已有相关的模型和描述，并在实践中得到广泛的应用，如何建立模糊空间要素这间的拓扑关系是建立模糊要素地理信息系统的基础。该文在模糊扑扑学的基础上提出了模糊区域的定义，建立了用于分析模糊区域之间拓扑关系的理论和模型，提出了4*4-intersection模型拓扑关系矩阵，并分析了不同拓扑关系矩阵对于非模糊区域之间、模糊区域之间建立拓扑关系的区别和联系，最后采和不同公式对模糊区域之间的关系进行了系统的描述。  相似文献   

基于网格的空间信息模型与服务技术研究   总被引：12，自引：0，他引：12  

何小朝  李琦  承继成 《地理与地理信息科学》2003,19(4):60-63

空间信息基础设施是实现数字城市的核心与基础，现有的万维网已经不能满足空间信息访问与处理的需要。该文对以空间信息为核心和基础的数据网格——空间信息网格的基础理论及网格中的空间信息模型与服务技术：进行研究。提出了空间信息网格的若干关键技术及网格中的空间信息模型的特点与要求，并对空间信息网格服务进行了初步的探讨。  相似文献   

行播冬小麦热辐射方向性的影响因子   总被引：1，自引：0，他引：1  

范闻捷  徐希孺 《地理与地理信息科学》2003,19(4):84-88

混合像元的热辐射方向性由于受到多种因素的影响而变得极为复杂。该文以行播冬小麦为例，建立矩阵模型，研究混合像元热辐射方向性问题。结果表明，混合像元热辐射方向性主要受到混合像元内部各组分在三维上分布的不均一、像元比辐射率的方向性以及由外界影响造成的各组分温度差异的影响。在这三个主要影响因子中，各组分的比辐射率是地物固有的特征，不随外界条件而发生变化。在同温条件下，像元热辐射方向性完全由像元比辐射率的方向性决定。而各组分温度虽然没有方向性，但可以通过组分空间分布对其产生调制作用。  相似文献   

智能交通系统中的公交车辆指挥调度体系结构   总被引：2，自引：0，他引：2  

张飞舟  晏磊  范跃祖  孙先仿 《地理与地理信息科学》2003,19(4):109-112

该文阐述公交智能指挥调度系统总体框架，结合智能交通系统ITS(Intelligent Transport Systems)对公交智能化调度的逻辑结构和物理结构要求，分析公交车辆智能化调度系统结构体系及其模型化，探讨智能调度策略和调度机理。根据该系统总体设计框架构思，了解系统各功能间的相互关系，优化公交车辆运营管理模式，以改善现有公交系统的管理水平以及运营效率，为公交指挥调度系统的完善、提高提供可靠技术基础。  相似文献   

基于GTP的地下工程与围岩一体化真三维空间构模   总被引：10，自引：5，他引：10  

吴立新  陈学习  史文中 《地理与地理信息科学》2003,19(6):1-6

针对地下工程开挖体的基本特征及其真三维建模要求，在广义三棱柱(GTP)模型的基础上进行扩展，提出采用E—GTP模型来构建地下工程开挖体的真三维模型。通过与其围岩地质体的G—GTP模型的耦合，实现了基于GTP的工程开挖体与围岩地质体的一体化建模。该模型将地下三维空间实体抽象为点、线、面、体四类对象，通过结点、TIN边、侧边、TIN面、侧面和GTP体元共6个基本几何元素进行统一表达。该文重点讨论了E—GTP的建模原理与方法，并介绍了基于面向对象思想的一体化空间数据结构。  相似文献