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Increased interest in the two- and three-dimensional geometries and development of faults and other types of fractures in rock has led to an increasingly bewildering terminology. Here we give definitions for the geometric, topological, kinematic and mechanical relationships between geological faults and other types of fractures, focussing on how they relate to form networks. 相似文献
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R. T. Downs G. V. Gibbs M. B. Boisen Jr K. M. Rosso 《Physics and Chemistry of Minerals》2002,29(5):369-385
The procrystal calculation of the electron density is a very rapid procedure that offers a quick way to analyze various bonding
properties of a crystal. This study explores the extent to which the positions, number, and properties of bond-critical points
determined from the procrystal representations of the electron density for minerals are similar to those of first-principles
ab initio model distributions. The purpose of the study is to determine the limits imposed upon interpretation of the procrystal
electron density. Procrystal calculations of the electron density for more than 300 MO bonds in crystals were compared with those previously calculated using CRYSTAL98 and TOPOND software. For every bond-critical
point found in the ab initio calculations, an equivalent one was also found in the procrystal model, with similar magnitudes
of electron density, and at similar positions along the bonds. The curvatures of the electron densities obtained from the
ab initio and the procrystal distributions are highly correlated. It is concluded that the procrystal distributions are capable
of providing good estimates of the bonded radii of the atoms and the properties of the electron-density distributions at the
bond-critical points. Because the procrystal model is so fast to compute, it is especially useful in addressing the question
as to whether a pair of atoms is bonded or not. If the Bader criteria for bonding are accepted, then the successful generation
of the bond-critical points by the procrystal model demonstrates that bonding is an atomic feature. The main difference between
the critical-point properties of the procrystal and the ab initio model is that the curvature in the electron density perpendicular
to the bond path of the ab initio model is sharper than for the procrystal model. This is interpreted as indicating that the
electrons that migrate into a bond originate from its sides, and not from the regions closer to the nuclei. This observation
also suggests that ab initio optimization routines could see an improvement in speed if the parameters relating to the angular
components of atomic wave functions were to vary before the radial components.
Received: 6 August 2001 / Accepted: 21 November 2001 相似文献
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根据华东地质学院校园网二期建设项目,简要介绍了本院校园网的拓扑结构图、校园网采用的VLAN技术及其第三层交换(路由)技术,阐述了校园网建设中子网划分与IP地址分配方法。 相似文献
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数字拓扑学和层析成像 总被引:1,自引:0,他引:1
本文论述拓扑学在数字图像中的应用,首先定义数字图像子集的性概念,并论述当前正孕育着一门分支-数字拓扑学及其在层析成像的可能具有的联系。 相似文献
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Many dynamic phenomena in the solar corona are driven by the complex and ever-changing magnetic field. It is helpful, in trying to model these phenomena, to understand the structure of the magnetic field, i.e. the magnetic topology. We study here the topological structure of the coronal magnetic field arising from four discrete photospheric flux patches, for which we find that seven distinct, topologically stable states are possible; the changes between these are caused by six types of bifurcation. Two bifurcation diagrams are produced, showing how the changes occur as the relative positions and strengths of the flux patches are varied. A method for extending the analysis to higher numbers of sources is discussed. 相似文献
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Abstract In previous work, a relational data structure aimed at the exchange of spatial data between systems was developed. As this data structure was relational it was of first normal form, but compliance with the higher normal forms was not investigated. Recently, a new procedural method for composing fully normalized data structures from the basic data fields has been developed by H. C. Smith, as an alternative to the process of non-loss decomposition which is difficult to understand. Smith's method has been applied to data fields required to store points, lines and polygons in a chain-node spatial data model. When geographic domain, coverage layer and map are also considered, the procedure naturally leads to a catalogue model, needed for the exchange of spatial data. Although the method produces a fully normalized data structure, it is not as easy to identify which normal forms are responsible for the ultimate arrangement of the data fields into relations, but the benefits of these criteria for data base development also apply to spatial data structures and related ancillary data. 相似文献
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Jeremiah D. Lindemann William L. Baker 《International journal of geographical information science》2013,27(4):377-399
Many studies have helped us understand where blowdowns occur, how forests regenerate and respond to large disturbances. However, few studies have analysed how physical and biological factors affect blowdowns or interact with one another to determine susceptibility to blowdown. These factors range from the natural physical setting to past disturbances, and human-related features, such as roads and timber harvest units. These factors were examined in this study. Patches of the blown-down forest were mapped for the 1997 Routt-Divide blowdown, which affected over 10 000 ha of subalpine forest in north-central Colorado. A systematic sampling scheme was used to extract information on predictors for sampling points inside and outside the blowdown. Data on predictors were used in Classification and Regression Trees (CART) and logistic regression to model blowdown occurrence and severity. Two models were applied, and both were able to predict with an overall success rate of 75% or more. These two models produced similar results, showing that the Routt-Divide blowdown was most influenced by factors pertaining to the physical setting: distance to the Continental Divide, wind exposure, elevation, aspect, and cover type. Surprisingly, soil permeability and water-holding capacity and distance to natural edges (e.g. forest-meadow) were not correlated significantly with the blowdown pattern. 相似文献
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Topology has been used to characterise and quantify the properties of complex systems in a diverse range of scientific domains. This study explores the concept and applications of topological analysis in geology. We have developed an automatic system for extracting first order 2D topological information from geological maps, and 3D topological information from models built with the Noddy kinematic modelling system, and equivalent analyses should be possible for other implicit modelling systems. A method is presented for describing the spatial and temporal topology of geological models using a set of adjacency relationships that can be expressed as a topology network, thematic adjacency matrix or hive diagram. We define three types of spatial topology (cellular, structural and lithological) that allow us to analyse different aspects of the geology, and then apply them to investigate the geology of the Hamersley Basin, Western Australia. 相似文献