Spatial statistics for urban analysis: A review of techniques with examples

Traditionally, urban analysis has been quick to adopt and benefit from developments in technology (e.g., microcomputer, GIS) and techniques (e.g., statistics, mathematical programming). This has not been the case, however, with newer methods of spatial analysis — in particular, spatial statistics. Only recently has this situation started to change. This paper documents the confluence of spatial statistics and urban analysis by first reviewing developments in spatial statistics, and then presenting examples of recent applications in urban analysis. The developments reviewed fall under the rubric of global and local forms of spatial analysis, and cover three major technical issues: spatial association, spatial heterogeneity and the modifiable areal unit problem. The examples highlight the relevance and usefulness of the techniques reviewed for urban transportation and land-use applications. The paper concludes with conjectures concerning future developments at the intersection of spatial statistics and urban analysis.     

Spatial statistics for urban analysis: A review of techniques with examples

Traditionally, urban analysis has been quick to adopt and benefit from developments in technology (e.g., microcomputer, GIS) and techniques (e.g., statistics, mathematical programming). This has not been the case, however, with newer methods of spatial analysis — in particular, spatial statistics. Only recently has this situation started to change. This paper documents the confluence of spatial statistics and urban analysis by first reviewing developments in spatial statistics, and then presenting examples of recent applications in urban analysis. The developments reviewed fall under the rubric of global and local forms of spatial analysis, and cover three major technical issues: spatial association, spatial heterogeneity and the modifiable areal unit problem. The examples highlight the relevance and usefulness of the techniques reviewed for urban transportation and land-use applications. The paper concludes with conjectures concerning future developments at the intersection of spatial statistics and urban analysis.     

Strategic globalizing centers and sub-network geometries: A social network analysis of multi-scalar energy networks

Over the past three decades, a multitude of studies have examined the relational properties of corporate networks as a proxy for analyzing interurban hierarchies and structures. While this has been important in illuminating the nature of global connectivity, a significant conceptual lacuna exists in understanding how a multi-scalar analysis of interurban networks informs a more complete understanding of the geographies of globalization, and how cities within these networks act as regional globalizing centers. Building upon the theoretical and methodological foundations of ‘world city network’ (WCN) research, this paper investigates the corporate networks of the energy industry as a historic driver of globalization using social network analysis from an Australia geographical perspective. Globally and nationally scaled energy networks derived from the Platts and Australian Securities Exchange (ASX) corporate lists are used to explore the convergence of nationally and globally articulated networks, and identify cities instrumental in the globalization of the national industry sub-networks. These are strategic ‘globalizing centers’ which, in contradistinction to ‘global cities’ or ‘world cities’ as broad classifications, play nuanced roles in anointing industry-specific circuits of capital and information. The analysis of two complementary yet distinct networks provides theoretical insight into how scale plays an integral role in defining/articulating interurban relations.     

History and regional development. A controversy over the ‘right’ interpretation of the role of history in the development of the Polish regions

There is currently a lively discussion on the role of historic memories and the re-visiting of historic legacies in post-communist countries. Using the example of Poland and its legacy of the tripartite division of the 19th century, this paper aims to illustrate how symbolic conflicts over identity politics and the interpretation of history may critically influence discourses on the debates on, and portrayals of, variations in regional development. The paper thus discusses the post-war history of Poland in the context of the so-called left-right political cleavage, and the varying related debates on the ‘quality’ of regional development as part of Poland’s post-communist restructuring. These discussions include varying projections of the nature and role of social capital and its relative ‘usefulness’ for a successful development Poland’s after communism. And there are clear political overtones to these contrasting portrayals of Poland’s history and its regionally varying legacy. Drawing on different definitions of the notion of social capital, the paper then discusses how different legacies, such as an introspective and extrovert outlook of population and institutions, and the degree of cohesion among them, circumscribes a region’s economic development prospects.     

应用最大熵原理分析水利工程经济效益的风险

采用层次分析方法,将水利工程经济效益系统分为防洪、发电、灌溉效益子系统,辩识出风险因子,建立了基于最大熵原理(准则)的经济效益风险分析模型,并给出求解方法。对总系统经济效益风险分析采用了两种方法:一是直接对辩识出的风险因子进行概率分析,得出总效益指标的最大熵密度函数;二是按照"风险树"的思路,分析子系统效益的风险特性,再进行风险组合,从而考察总效益的风险性。用实例验证了该模型的可行性和实用性。     

Homogenization framework for three‐dimensional elastoplastic finite element analysis of a grouted pipe‐roofing reinforcement method for tunnelling

This paper deals with the grouted pipe‐roofing reinforcement method that is used in the construction of tunnels through weak grounds. This system consists on installing, prior to the excavation of a length of tunnel, an array of pipes forming a kind of ‘umbrella’ above the area to be excavated. In some cases, these pipes are later used to inject grout to strengthen the ground and ‘connect’ the pipes. This system has proven to be very efficient in reducing tunnel convergence and water inflow when tunnelling through weak grounds. However, due to the geometrical and mechanical complexity of the problem, existing finite element frameworks are inappropriate to simulate tunnelling using this method. In this paper, a mathematical framework based on a homogenization technique to simulate ‘grouted pipe‐roofing reinforced ground’ and its implementation into a 3‐D finite element programme that can consider stage construction situations are presented. The constitutive model developed allows considering the main design parameters of the problem and only requires geometrical and mechanical properties of the constituents. Additionally, the use of a homogenization approach implies that the generation of the finite element mesh can be easily produced and that re‐meshing is not required as basic geometrical parameters such as the orientation of the pipes are changed. The model developed is used to simulate tunnelling with the grouted pipe‐roofing reinforcement method. From the analyses, the effects of the main design parameters on the elastic and the elastoplastic analyses are considered. Copyright © 2004 John Wiley & Sons, Ltd.     

Regional integration or disintegration? Recent road improvements in Petén, Guatemala: A review of preliminary economic, agricultural, and environmental impacts

Many studies have examined the impacts of new roads in tropical forest frontiers. In general, these have led to substantial deforestation because they provide access to peasant farmers in need of land for food production and income generation. But few studies have investigated the impacts of improvements made to existing roads in frontier regions, and more specifically, their effects on the rural economy, land use, and land cover. This paper discusses the results of a 2001 study of these impacts, following the recent paving of the main road between Petén, a lowland frontier region in northern Guatemala, and the more densely populated highland regions of the country. This improvement, completed in late 1999, has yielded a major reduction in travel time between Flores, Petén and Guatemala City, the capital, from 12 to 14 h, or more, previously, to 7-8 h currently. The effects of this substantial change were examined through interviews and discussions with farmers, market vendors, and representatives of governmental and non-governmental organizations in the region, and through analyzing the limited available data on imports to Petén from other parts of the country. The results indicate that to date, the farmers in the study area have not altered their land use patterns because the prices they receive from intermediaries have not changed, and no market for new crops has emerged. However, more agricultural products raised in other regions of Guatemala are now being sold in Petén. Therefore, producers in Petén seemingly face greater competition from those elsewhere in the country. This trend has important implications regarding the impacts of regional integration, and for the difficult challenge of improving agricultural and environmental conditions in Petén.     

A continuum mechanics‐based framework for boundary and finite element mesh optimization in two dimensions for application in excavation analysis

The determination of the optimum excavation sequences in mining and civil engineering using numerical stress analysis procedures requires repeated solution of large models. Often such models contain much more complexity and geometric detail than required to arrive at an accurate stress analysis solution, especially considering our limited knowledge of rock mass properties. This paper develops an automated framework for estimating the effects of excavations at a region of interest, and optimizing the geometry used for stress analysis. It eliminates or simplifies the excavations in a model while maintaining the accuracy of analysis results. The framework can equally be applied to two‐dimensional boundary and finite element models. The framework will have the largest impact for non‐linear finite element analysis. It can significantly reduce computational times for such analysis by simplifying models. Error estimators are used in the framework to assess accuracy. The advantages of applying the framework are demonstrated on an excavation‐sequencing scenario. Copyright © 2005 John Wiley & Sons, Ltd.     

A semi‐empirical method for the liquefaction analysis of offshore foundations

This paper presents a relatively simple method for three‐dimensional liquefaction analysis of granular soil under offshore foundations. In this method, the Mohr–Coulomb model, which defines the elasto–plastic stress–strain relationship under monotonic loading, is modified to accommodate the plastic strains generated by cyclic loading. The effects of cyclic loading, evaluated from the results of laboratory tests on saturated samples of soil, are incorporated into the model. The method is implemented in an efficient finite element program for analyses of three‐dimensional consolidating soil. The practicability of the model is demonstrated by analysis of a typical offshore foundation, and the predictions of the numerical analysis are compared with the observed behaviour of the foundation. Copyright © 2000 John Wiley & Sons, Ltd.     

基于不确定性分析框架的动态环状河网水质模型--以温州市温瑞塘河为例

以温州市温瑞塘河为背景,基于不确定性分析的框架,开发了动态环状河网水质模型。用HSY(Hornberger,Spear and Young)算法作水质参数的不确定性分析,求得模型参数的空间分布,从而提高模型使用的可靠性、降低决策的风险度。模型由水量子模型及水质子模型两部分组成:水量子模型采用圣维南方程并用四级解法求解;水质子模型采用CSTR(Continuously Stirred Tank Reactor)模型的机理,并结合环状河网特征作了修正,由于只需解常微分方程,因而避免了矩阵求解,显著提高了计算效率,使得用HSY算法进行不确定性分析成为可能。模型选取温州市温瑞塘河流域的鹿城区河网进行了首次应用,用HSY算法率定水质参数并讨论了参数的不确定性。对参数率定结果进行验证,结果比较理想。最后简要讨论了参数不确定性传递。     

壁面局部接触裂隙岩体水流-传热的一种理论模型及计算分析

核废物地质处置、地热开发、石油开采等工程领域都可能涉及稀疏裂隙岩体中的水流-传热过程。现有的裂隙岩体水流-传热理论模型和计算方法基本上都是以平行光滑壁面裂隙模型为基础的,没有考虑裂隙的壁面局部接触对水流、水-岩热交换以及岩体传热的影响。针对粗糙壁面裂隙水流过程,阐述了基于Stokes方程的Reynolds润滑方程及Hele-Shaw裂隙模型,采用MATLAB软件中的PDE工具求解,并与Walsh的等效水力开度公式进行对比;分析壁面局部接触裂隙水流-传热与填充裂隙水流-传热的相似性,提出了瞬时局部热平衡假设的适用条件,并在裂隙局部接触体传热满足Biot数条件的前提下,计算分析裂隙局部接触体与水流之间的局部热平衡时间及其影响因素;在裂隙局部接触体与水流之间满足瞬时热平衡假设的前提下,利用填充裂隙水流-传热的解析解,计算了壁面局部接触裂隙水及两侧岩石的温度分布,并分析了裂隙局部接触面积率、裂隙开度、裂隙水平均流速对岩石温度和裂隙水温度的影响特征,结果表明：（1）在设定条件下,由于裂隙局部接触体与裂隙水流之间的热交换,裂隙水流对其两侧岩石温度的影响范围随接触面积率的增大而减小,裂隙两侧岩石对裂隙水流温度的影响程度随接触面积率的增大而增大;（2）裂隙开度和裂隙水流速对岩石温度和裂隙水温度的影响方式的影响是一致的,即由于裂隙水流量随裂隙开度和裂隙水流速的增大而增大,裂隙水流对其两侧岩石温度的影响范围随裂隙开度和裂隙水流速的增大而增大,裂隙两侧岩石对裂隙水流温度的影响程度随裂隙开度和裂隙水流速的增大而减小。     

A bounding surface elasto‐viscoplastic constitutive model for non‐isothermal cyclic analysis of asphaltic materials

An elasto‐viscoplastic constitutive model for asphaltic materials is presented within the context of bounding surface plasticity theory, taking into account the effects of the stress state, void binder degree of saturation, temperature and strain rate on the material behaviour. A stress state dependent non‐linear elasticity model is introduced to represent time‐independent recoverable portion of the deformation. The consistent visco‐plasticity framework is utilised to capture the rate‐dependent, non‐recoverable strain components. The material parameters introduced in the model are identified, and their determination from conventional laboratory tests is discussed. The capability of the model to reproduce experimentally observed response of asphaltic materials is demonstrated through numerical simulations of several laboratory test data from the literature. Copyright © 2016 John Wiley & Sons, Ltd.     

A multidirectional semi‐analytical method for analysis of laterally loaded pile groups in multi‐layered elastic strata

A semi‐analytical method for calculating the response of single piles and pile groups subjected to lateral loading is developed in this paper. Displacements anywhere in the soil domain are tied to the displacements of the piles through decay functions. The principle of virtual work and the calculus of variations are used to derive the governing differential equations that describe the response of the piles and soil. The eigenvalue method and the finite difference technique are used to solve the system of coupled differential equations for the piles and soil, respectively. The proposed method takes into account the soil surface displacement along and perpendicular to the loading direction and produces displacement fields that are very close to those produced by the finite element method but at lower computational effort. Compared with the previous method that considered only the soil displacement along the loading direction, accounting for the multi‐directional soil displacement field produces responses for the piles and soil that are closer to those approximated by the finite element method. Copyright © 2016 John Wiley & Sons, Ltd.     

Microtextural analysis of a glacially ‘deformed’ bedrock: implications for inheritance of preferred clast orientations in diamictons

Although analysis of clast macrofabrics has been used to differentiate between different types of glacial diamictons and to determine palaeo‐ice flow directions, no account appears to have been made of preferred clast orientations inherited from the parental source material. Clast macrofabrics in tills are typically interpreted as having developed in response to an imposed subglacial deformation and as such provide a link between the sedimentary record and glacier dynamics. They rely on the assumption that any preferred clast orientation is a result of deformation/flow. The results of the micromorphological study of the Langholm Till exposed at North Corbelly near Dumfries (southwestern Scotland) clearly demonstrate that bedrock structure can influence clast orientation (macrofabric) within diamictons. In the lower part of the till, the orientation of elongate clasts preserves the geometry of the tectonic cleavage present within the underlying bedrock. The intensity of this steeply inclined, ‘inherited’ clast fabric decreases upward through the till, to be replaced by a more complex pattern of successive generations of clast microfabrics developed in response to deformation/flow. These results indicate potential limitations of applying clast macrofabric or microfabric analysis in isolation to establish till genesis or palaeo ice‐flow directions. Consequently, due account should be made of other glacial palaeo‐environmental and ice flow indicators, as well as rockhead depth and morphology in relation to the selection of fabric measurements sites. © British Geological Survey/Natural Environment Research Council copyright 2007. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.     

A modulus‐multiplier approach for non‐linear analysis of laterally loaded pile groups

A modulus‐multiplier approach, which applies a reduction factor to the modulus of single pile p–y curves to account for the group effect, is presented for analysing the response of each individual pile in a laterally loaded pile group with any geometric arrangement based on non‐linear pile–soil–pile interaction. The pile–soil–pile interaction is conducted using a 3D non‐linear finite element approach. The interaction effect between piles under various loading directions is investigated in this paper. Group effects can be neglected at a pile spacing of 9 times the pile diameter for piles along the direction of the lateral load and at a pile spacing of 6 times the pile diameter for piles normal to the direction of loading. The modulus multipliers for a pair of piles are developed as a function of pile spacing for departure angle of 0, 90, and 180sup>/sup> with respect to the loading direction. The procedure proposed for computing the response of any individual pile within a pile group is verified using two well‐documented full‐scale pile load tests. Copyright © 2006 John Wiley & Sons, Ltd.     

Bearing capacity factors of circular foundations for a general c–ϕ soil using lower bound finite elements limit analysis

By using the lower bound limit analysis in conjunction with finite elements and linear programming, the bearing capacity factors due to cohesion, surcharge and unit weight, respectively, have been computed for a circular footing with different values of ?. The recent axisymmetric formulation proposed by the authors under ?=0 condition, which is based on the concept that the magnitude of the hoop stress (σ_θ) remains closer to the least compressive normal stress (σ₃), is extended for a general c–? soil. The computational results are found to compare quite well with the available numerical results from literature. It is expected that the study will be useful for solving various axisymmetric geotechnical stability problems. Copyright © 2010 John Wiley & Sons, Ltd.     

A multiproxy record of late Holocene natural and anthropogenic environmental change from the Sphagnum peat bog Dürres Maar,Germany: implications for quantitative climate reconstructions based on pollen

Pollen data are well established for quantitative climate reconstructions over long timescales, including the Holocene and older interglacials. However, anthropogenically induced environmental change in central Europe was strong during the last 4 ka, challenging quantitative reconstructions of this time period. Here we present quantitative climate reconstructions based on pollen analyses and evaluate them with the peat humification record and the stable carbon isotopes of Sphagnum plant material (δ¹³C_cellulose). All analyses were carried out on the same 7.5 m long, largely ombrotrophic peat bog section from Dürres Maar. Three different methods were used for the quantitative climate reconstructions on the basis of the pollen data: (1) a probabilistic indicator taxa approach (the ‘pdf method’); (2) a modern analogue technique based on pollen taxa from modern surface samples (cMAT); and (3) a modern analogue technique expanded by plant functional types (pMAT). At Dürres Maar the peat humification is only affected by peat cutting during the Roman period and the Middle Ages. The stable carbon isotopes are seemingly unaffected by human impact. Thus both proxies provide independent data to evaluate the reconstructions on the basis of pollen data. The quantitative climate reconstructions on the basis of the individual methods are in general relatively similar. Nevertheless, distinct differences between the individual approaches are also apparent, which could be attributed to taxa that reflect human impact on a local to regional scale. While the pdf method appears to be relatively robust to all observed anthropogenically induced vegetation changes, it potentially underestimates climate variability. This method is therefore expected to be independent of local site characteristics and to provide robust quantitative estimates of climatic trends rather than of climatic variability of small amplitude. This is of value for palaeoclimate reconstructions of older interglacials, for which neither multiple sites nor independent climate proxies are available for comparison. Copyright © 2009 John Wiley & Sons, Ltd.     

A multiscale analysis of a fracture pattern in granite: A case study of the Tamariu granite,Catalunya, Spain

The in-depth investigation of fractured reservoirs is mainly limited to geophysical data that is in 3D and mostly on the scale of hundred meters to several kilometers or boreholes data that is in 1D and at meter to lower scale. The study of outcropping analogues of buried reservoirs is therefore a key tool for the characterization of the fault and fracture network at the reservoir scale. Tamariu granite has been the subject of this study with the aim to analyse faults and fractures from seismic to borehole scale. With the combination of satellite picture at different resolution and field study, we perform a statistical analysis focused of the length and orientation from infra centimeter crack to hundred kilometer length fault. On the whole range of scale studied, i.e. on 7 orders of magnitude, we have defined a length distribution following a power-law with an exponent a = −2. On the contrary to the length that can be modelled with a unique law, the orientation data shows a variation depending on the scale of observation: as the fault and fracture sets are suitable from the regional faults to the centimeter crack, the proportion of the sets varies at each scale of observation.     

A high strain‐rate constitutive model for sand and its application in finite‐element analysis of tunnels subjected to blast

The paper presents a constitutive model for simulating the high strain‐rate behavior of sands. Based on the concepts of critical‐state soil mechanics, the bounding surface plasticity theory and the overstress theory of viscoplasticity, the constitutive model simulates the high strain‐rate behavior of sands under uniaxial, triaxial and multi‐axial loading conditions. The model parameters are determined for Ottawa and Fontainebleau sands, and the performance of the model under extreme transient loading conditions is demonstrated through simulations of split Hopkinson pressure bar tests up to a strain rate of 2000/s. The constitutive model is implemented in a finite‐element analysis software Abaqus to analyze underground tunnels in sandy soil subjected to internal blast loads. Parametric studies are conducted to examine the effect of relative density and type of sand and of the depth of tunnel on the variation of stresses and deformations in the soil adjacent to the tunnels. Copyright © 2012 John Wiley & Sons, Ltd.     

A fully coupled element‐free Galerkin model for hydro‐mechanical analysis of advancement of fluid‐driven fractures in porous media

Hydraulic fracturing (HF) of underground formations has widely been used in different fields of engineering. Despite the technological advances in techniques of in situ HF, the industry uses semi‐analytical tools to design HF treatment. This is due to the complex interaction among various mechanisms involved in this process, so that for thorough simulations of HF operations a fully coupled numerical model is required. In this study, using element‐free Galerkin (EFG) mesh‐less method, a new formulation for numerical modeling of hydraulic fracture propagation in porous media is developed. This numerical approach, which is based on the simultaneous solution of equilibrium and continuity equations, considers the hydro‐mechanical coupling between the crack and its surrounding porous medium. Therefore, the developed EFG model is capable of simulating fluid leak‐off and fluid lag phenomena. To create the discrete equation system, the Galerkin technique is applied, and the essential boundary conditions are imposed via penalty method. Then, the resultant constrained integral equations are discretized in space using EFG shape functions. For temporal discretization, a fully implicit scheme is employed. The final set of algebraic equations that forms a non‐linear equation system is solved using the direct iterative procedure. Modeling of cracks is performed on the basis of linear elastic fracture mechanics, and for this purpose, the so‐called diffraction method is employed. For verification of the model, a number of problems are solved. According to the obtained results, the developed EFG computer program can successfully be applied for simulating the complex process of hydraulic fracture propagation in porous media. Copyright © 2016 John Wiley & Sons, Ltd.