地理本体空间关系表达模型研究

地理本体是表达地理概念及其之间关系的有效手段,地理本体的空间关系也是其区别于一般本体最重要的特征。本文探析了地理本体的构建方法,将地理本体空间关系分为拓扑关系、方位关系、距离关系和相似关系,重点研究了地理本体的拓扑关系和方位关系的空间表达模型,对拓扑关系进行梳理归纳,总结出8种互斥并完备的空间关系;利用锥形模型对方位关系进行描述,最后利用OWL语言对两种关系进行了推理表达。     

一种定量化表达的空间关系模型

目前已有的空间关系模型(拓扑关系、方向关系以及度量关系)基本上是相对独立的,同时这些模型(度量关系除外)主要是定性的形式化描述,其表达精度还有待提高,因此有必要研究定量化的、组合表达的空间关系模型。提出了一种定量化表达的空间关系直方图模型,它能同时表征两个面目标之间的拓扑关系、方向关系以及度量关系,并可以定量化地分类(概率表征)空间关系类型。实验结果验证了该模型的有效性。     

Variable-density flow and transport in porous media: approaches and challenges

We review the state of the art in modeling of variable-density flow and transport in porous media, including conceptual models for convection systems, governing balance equations, phenomenological laws, constitutive relations for fluid density and viscosity, and numerical methods for solving the resulting nonlinear multifield problems. The discussion of numerical methods addresses strategies for solving the coupled spatio-temporal convection process, consistent velocity approximation, and error-based mesh adaptation techniques. As numerical models for those nonlinear systems must be carefully verified in appropriate tests, we discuss weaknesses and inconsistencies of current model-verification methods as well as benchmark solutions. We give examples of field-related applications to illustrate specific challenges of further research, where heterogeneities and large scales are important.     

SPLITAREA: an algorithm for weighted splitting of faces in the context of a planar partition

Geographic data themes modelled as planar partitions are found in many GIS applications (e.g. topographic data, land cover, zoning plans, etc.). When generalizing this kind of 2D map, this specific nature has to be respected and generalization operations should be carefully designed. This paper presents a design and implementation of an algorithm to perform a split operation of faces (polygonal areas).

The result of the split operation has to fit in with the topological data structure supporting variable-scale data. The algorithm, termed SPLITAREA, obtains the skeleton of a face using a constrained Delaunay triangulation. The new split operator is especially relevant in urban areas with many infrastructural objects such as roads. The contribution of this work is twofold: (1) the quality of the split operation is formally assessed by comparing the results on actual test data sets with a goal/metric we defined beforehand for the ‘balanced’ split and (2) the algorithm allows a weighted split, where different neighbours have different weights due to different compatibility. With the weighted split, the special case of unmovable boundaries is also explicitly addressed.

The developed split algorithm can also be used outside the generalization context in other settings. For example, to make two cross-border data sets fit, the algorithm could be applied to allow splitting of slivers.     

Calculated Phase Relations in High-Pressure Metapelites in the System NKFMASH (Na2O-K2O-FeO-MgO-Al2O3-SiO2-H2O)

Using an internally consistent thermodynamic dataset and updatedmodels of activity–composition relation for solid solutions,petrogenetic grids in the system NKFMASH (Na₂O–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O)and the subsystems NKMASH and NKFASH have been calculated withthe software THERMOCALC 3.1 in the P–T range 5–36kbar and 400–810°C, involving garnet, chloritoid,biotite, carpholite, talc, chlorite, kyanite/sillimanite, staurolite,phengite, paragonite, albite, glaucophane, jadeite, with quartz/coesiteand H₂O in excess. These grids, together with calculated AFMcompatibility diagrams and P–T pseudosections, are shownto be powerful tools for delineating the phase equilibria andP–T conditions of Na-bearing pelitic assemblages for avariety of bulk compositions from high-P terranes around theworld. These calculated equilibria are in good agreement withpetrological studies. Moreover, contours of the calculated phengiteSi isopleths in P–T pseudosections for different bulkcompositions confirm that phengite barometry is highly dependenton mineral assemblage. KEY WORDS: phase relations; HP metapelite; NKFMASH; THERMOCALC; phengite geobarometry     

砂土的流体动力学方程与本构模型的比较

目前砂土材料连续力学方程建模有两种途径,一种是源自于论证Navier-Stokes方程时所用的方法,称为流体动力学方法,主要针对普通固体、普通流体、超流、液晶、高聚物、颗粒物质等材料,它的基本做法是先给出守恒变量（如能量、动量、熵等）和对称破缺变量（如弹性应变、量子相位等）的一般运动方程,再用与具体材料有关的热力学函数和迁移系数来封闭它们;另一种方法是本构模型法,针对有塑性固体、非牛顿流体、砂土材料等材料,该做法特点是直接构建应力、应变、应力率、应变率、速度、密度、温度等变量之间的函数关系,并以此来封闭连续和牛顿方程。近年来采用这两种方法建立的砂土方程在文献上都有报道,因此,有必要对两者的特色、科学基础、适用范围,包括概念上的和具体方程等,进行比较,作为颗粒物理与土力学之间跨学科交流的一种尝试和沟通。通过比较得出,两种建模途径对表征砂土状态的完备变量集、屈服面、与塑性有关的耗散等使用了很不一样的思路和方程。     

一种顾及图斑拓扑关系的化简方法

针对地理国情普查成果制图的实际需求,提出了一种顾及图斑原有拓扑关系的化简方法。通过对图斑数据进行拓扑构建,将对图斑的化简转化为对共享弧段的化简;同时对弧段进行分类,对不同类型的弧段采用相应的化简方法。通过实例验证表明,该方法能够保持图斑化简前的形态结构,并保持图面整洁,符合地图制图要求,取得了较好的应用效果。     

移动区域时空关系变化建模研究

针对二维欧氏空间内的移动区域对象在时空关系变化建模中存在的问题,该文提出了一种时空关系变化序列模型,并建立了时空关系变化概念邻域图。采取基于时间片的时空数据模型,通过分析移动区域间随时间变化的拓扑、距离和方位关系,解决时空关系变化的集成建模问题。该方法能有效刻画移动区域的动态时空特征。     

Kinematic hardening plasticity formulation of small strain behaviour of soils

An objective of this paper is to demonstrate that the small strain model developed by the authors can be incorporated into the conventional kinematic hardening plasticity framework to predict pre‐failure defor mations. The constitutive model described in this paper is constituted by three elliptical yield surfaces in triaxial stress space. Two inner surfaces are rotated ellipses of the same shape, representing the boundaries of the linear elastic and small strain regions, while the third surface is the modified Cam clay large‐scale yield surface. Within the linear elastic region, the soil behaviour is elastic with cross‐coupling between the shear and volumetric stress–strain components. Within the small strain region, the soil behaviour is elasto‐plastic, described by the kinematic hardening rule with an infinite number of loading surfaces defined by the incremental energy criterion. Within the large‐scale yield surface, the soil behaviour is elasto‐plastic, described by kinematic and isotropic hardening of the small strain region boundary. Since the yield surfaces have different shapes, the uniqueness of the plastic loading condition imposes a restriction on the ratio between their semi‐diameters. The model requires 12 parameters, which can be determined from a single consolidated undrained triaxial compression test. Copyright © 2000 John Wiley & Sons, Ltd.     

Studying the making of geographical knowledge: The implications of insider interviews

The article addresses the issue of being a ‘double’ insider when conducting interviews. Double insider means being an insider both in relation to one's research matter – in the authors’ case the making of geographical knowledge – and in relation to one's interviewees – our colleagues. The article is a reflection paper in the sense that we reflect upon experiences drawn from a previous research project carried out in Danish academia. It is important that the project was situated in a Scandinavian workplace culture because this has bearings for the social, cultural, and economic situation in which knowledge was constructed. The authors show that being a double insider affects both the interview situation and how interviews are planned, located, and analysed. Being an insider in relation to one's interviewees gives the advantage of having a shared history and a close knowledge of the context, and these benefits outnumber the disadvantages. Being an insider in relation to one's research matter makes it difficult to contest hegemonic discourses and tacit values and ideas. Recommendations on how to handle the double insider situation are given. The article concludes that for analytical purposes, it is useful to separate the two roles, but in reality they coexist and are intertwined.