THE PRAIRIE PENINSULA: A CLIMATIC PERSPECTIVE

The adequacy of climate to explain the distribution of the tallgrass-prairie—oak-hickory forest in the United States has been investigated and it is shown that the prairie peninsula originated due to a unique combination of climatic conditions prevailing in the Middle West. The climate which is unique to the peninsula has been defined in terms of effective moisture as determined by soil moisture deficit, water surplus, and the index of moisture using the Thornthwaite's water budget procedure.

The results of this study demonstrate that definite quantities of soil moisture deficit, water surplus, and the index of moisture restrict the growth and development of the tallgrass-prairie-oak-hickory forest to a well-defined geographic region in the United States. Vegetational response to effective climate is expressed in the closeness of fit between the critical isolines of soil moisture deficit, water surplus, and the index of moisture and the boundaries of the prairie peninsula. In particular, the moisture index isolines of 15 and 30 enclose the study area virtually on all sides and this shows that the climate of the prairie peninsula resembles neither the climate of the “true prairie” nor the climates of the surrounding forest regions.     

GROUP HOME LOCATION AND HOST NEIGHBORHOOD ATTRIBUTES: AN ECOLOGICAL ANALYSIS

This paper investigates the characteristics of areas with numerous group homes (residential care facilities) that cater to a variety of user groups. An overview of patterns of locational concentration precedes the results of an ecological analysis for the Minor Planning Districts of the City of Toronto. The pattern of ecological correlates among the three group home types analyzed supports results obtained elsewhere, but cautions against inferring ecological associations identified for one sort of facility to other facility types, The conclusion questions the suitability of present areas of locational concentration of group homes as host environments.     

现代港口发展的区位势理论基础

从整体的角度,对现代港口与所在区域的经济、社会和环境等相互作用和相互影响的机制及内在关系进行系统研究,是现代港口发展区域研究的重要方向和内容。本文系统地分析现代港口发展的主要区位因素,提出港口区位势概念及其理论研究的基本框架。     

Postindustrial Manufacturing in a Sunbelt Metropolis: Where Are Factories Located in Phoenix?

Manufacturing establishments are integral to the spatial structure of fast-growing Sunbelt metropolitan areas, but most concepts and theories of intrametropolitan location were largely developed for an earlier technological era and different spatial contexts. This article investigates the location of nine disaggregated manufacturing sectors in Phoenix, Arizona, showing varying degrees of central core concentration and metropolitan-wide clustering. Distinct sectoral co-location patterns are also evident. We interpret our results as evidence that the intrametropolitan location of postindustrial manufacturing is best understood as a series of spatial distributions with varying concentration, centralization, clustering, and other order-based characteristics. There is little evidence that randomly scattered discrete industrial zones have developed nor that spatial patterns are uniform. Enduring lock-in effects tied to transportation infrastructure are pivotal to understanding the locational distribution of manufacturing industries in metropolitan Phoenix. Results do not support a hypothesis that a positive relationship exists between establishment size and distance from sectoral mean centers.     

Inversion of a normally incident reflection seismogram by the Gopinath–Sondhi integral equation

Summary. The one-dimensional acoustic wave equation has been transformed to two coupled first-order equations whose inverse solution is obtained through application of the Gopinath and Sondhi integral equation. A scattering solution of the Schrödinger wave equation for an explosive source leads us to express the kernel of the Gopinath–Sondhi integral equation in terms of a seismic reflection response. A numerical solution of the integral equation obtained by a trapezoidal rule yields a continuous impedance profile whose derivative has step-like discontinuities. The method is illustrated with computer model studies.     

LOCATIONAL PROBLEMS AND PREFERENCES IN PRESCHOOL CHILD CARE*

With the increased use of formal child care, the number of child care alternatives has grown. The locational problems and preferences of University of Connecticut employees who use formal child care for children under age 6 are examined because an on-site program is available as one option. Difficulty finding care at a convenient location is related to residential location. Preference for worksite care decreases with increasing commuting distance. Variations in reported locational preferences by commuting zone are consistent with the notion of locating services within the activity spaces of the users. As commuting distance increases, worksite day care represents a greater displacement from the activity spaces of the child and possibly of other family members.     

Modeling of space–time infectious disease spread under conditions of uncertainty

A theoretical model for the spread of infectious diseases in a composite space–time domain is developed. The model has a general form that enables it to account for the basic mechanisms of disease distribution and to incorporate the considerable multisourced uncertainty (caused by physiographic features, disease variability, meteorological conditions, etc.). Starting from the general model formulation regarding the specification of transmission and recovery rates, as well as the population migration dynamics, several subsequent assumptions are introduced that simplify analytical tractability and practical implementation. In particular, linearization involving a deterministic functional representation for the average evolution of the fraction of susceptible individuals allows the formulation of an extended Kalman filter approach for estimation based on the time series observed at a finite set of locations. Different aspects of interest derived from the epidemic space–time model proposed, as well as the performance of the extended Kalman filter procedure, are illustrated through simulations.     

Non-hypersingular boundary integral equations for two-dimensional non-planar crack analysis

We derive a set of non-hypersingular boundary integral equations, both elastodynamic and elastostatic, for the analysis of arbitrarily shaped 2-D anti-plane and in-plane cracks located in an infinite homogeneous isotropic medium, rendered in a unified nomenclature for all cases. The hypersingularities that appear in the usual formulations for the dynamic cases, existent both at the source point and at the wavefront, are removed by way of a regularization technique based on integration by parts. The equations for the in-plane cases are presented in terms of a local Cartesian coordinate system, one of the axes of which is always held locally tangential to the crack trace. The expressions for the elastic field at any point on the model plane are also given.
Our formulations are shown to yield accurate numerical results, as long as appropriate stabilization measures are taken in the numerical scheme. The numerical applicability of our method to non-planar crack problems is illustrated by simulations of dynamic growth of a hackly crack which has small off-plane side-branches. The results imply that the branching of a crack brings about a significant decrease in the crack-tip stress concentration level and consequently may play an essential role in the arrest of earthquake rupturing.     

地理学时空数据分析方法

随着地理空间观测数据的多年积累,地球环境、社会和健康数据监测能力的增强,地理信息系统和计算机网络的发展,时空数据集大量生成,时空数据分析实践呈现快速增长。本文对此进行了分析和归纳,总结了时空数据分析的7类主要方法,包括：时空数据可视化,目的是通过视觉启发假设和选择分析模型;空间统计指标的时序分析,反映空间格局随时间变化;时空变化指标,体现时空变化的综合统计量;时空格局和异常探测,揭示时空过程的不变和变化部分;时空插值,以获得未抽样点的数值;时空回归,建立因变量和解释变量之间的统计关系;时空过程建模,建立时空过程的机理数学模型;时空演化树,利用空间数据重建时空演化路径。通过简述这些方法的基本原理、输入输出、适用条件以及软件实现,为时空数据分析提供工具和方法手段。     

A novel method for approximating intercity networks:An empirical comparison for validating the city networks in two Chinese city-regions

A network perspective has increasingly become an organizational paradigm for understanding regional spatial structures. Based on a critical overview of existing empirical models for estimating intercity networks based on firm linkages, this study extends the recently proposed regional corporate city model algorithm by proposing a new method for approximating urban networks based on the locational strategies of firms. The new method considers both regional and hierarchical network features and avoids the information loss associated with the conversion from two-mode firm-city networks to one-mode city-city networks. In addition, networks estimated by using the method proposed herein are suitable when employing social network analysis. Finally, this method is empirically validated by examining intercity firm networks formed by advanced producer services firms in China’s two largest metropolitan areas, namely the Yangtze River Delta and Pearl River Delta. The presented empirical analysis suggests two main findings. First, in contrast to conventional methods (e.g., the interlocking city network model), our new method produces regional and hierarchical urban networks that more closely resemble reality. Second, the new method allows us to use social network analysis to assess betweenness and closeness centralities. However, regardless of the model applied, the validity of any method that measures urban networks depends on the soundness of its underlying assumptions about how network actors (firms, in our case) interact.     

A STATISTICAL PROCEDURE TO EVALUATE CLEAN-UP STANDARDS

The object of this paper is to develop a suitable statistical procedure to evaluate clean-up standards athazardous waste sites.Under the assumptions that contaminant masses at a site follow a gammadistribution and that the data from the pre-remediation baseline sample as well as from the interim orfinal sample taken after a certain period of operation are both distributed as gamma with the same shapeparameter but different scale parameters,we derive a uniformly most powerful unbiased test of thehypothesis that a specified percentage of contaminant mass has been reduced.A large-sampleapproximation of the exact test procedure and a comparison with the likelihood ratio test are provided.     

A locational error model for spatial features

A locational error model for spatial features in vector-based geographical information systems (GIS) is proposed in this paper. Using error in points as the fundamental building block, a stochastic model is constructed to analyse point, line, and polygon errors within a unified framework, a departure from current practices which treat errors in point and line separately. The proposed model gives, as a special case, the epsilon band model a true probabilistic meaning. Moreover, the model can also be employed to derive accuracy standards and cartographic estimates in GIS.     

Land cover classification by an artificial neural network with ancillary information

Abstract

Remote sensing is an important source of land cover data required by many GIS users. Land cover data are typically derived from remotely–sensed data through the application of a conventional statistical classification. Such classification techniques are not, however, always appropriate, particularly as they may make untenable assumptions about the data and their output is hard, comprising only the code of the most likely class of membership. Whilst some deviation from the assumptions may be tolerated and a fuzzy output may be derived, making more information on class membership properties available, alternative classification procedures are sometimes required. Artificial neural networks are an attractive alternative to the statistical classifiers and here one is used to derive a fuzzy classification output from a remotely–sensed data set that may be post–processed with ancillary data available in a GIS to increase the accuracy with which land cover may be mapped. With the aid ancillary information on soil type and prior knowledge of class occurrence the accuracy of an artificial neural network classification was increased by 29–93 to 77–37 per cent. An artificial neural network can therefore be used generate a fuzzy classification output that may be used with other data sets in a GIS, which may not have been available to the producer of the classification, to increase the accuracy with which land cover may be classified.     

MapMosaic: dynamic layer compositing for interactive geovisualization

GIS software applications and other mapping tools enable users to correlate data from multiple layers and gain insight from the resulting visualizations. However, most of these applications only feature basic, monolithic layer compositing techniques. These techniques do not always support users effectively in their tasks, as we observed during interviews with GIS experts. We introduce MapMosaic, a novel approach based on dynamic visual compositing that enables users to interactively create and manipulate local composites of multiple vector and raster map layers, taking into account the semantics and attribute values of objects and fields in the compositing process. We evaluate MapMosaic ’s interaction model against that of QGIS (a widely used desktop GIS) and MAPublisher (a professional cartography tool) using the ‘Cognitive Dimensions’ framework and through an analytical comparison, showing that MapMosaic ’s model is more flexible and can support users more effectively in their tasks. We also report on feedback obtained from experts, which further confirms the potential of this highly dynamic approach to map layer compositing.     

Exploring Metropolitan Accessibility and Urban Structure

Location-based assessments of accessibility gauge the attraction of a place relative to other places. These approaches have been used extensively in models of commuting and urban structure. Even though locational accessibility measures are integral to such efforts, they may also be used to explore aspects of urban spatial structure. As such, this paper presents a GIS-based analysis of locational accessibility for a sample of U.S. metropolitan areas. Indices of accessibility based on spatial interaction models are developed for intraurban residential and employment locations. Results show that residential accessibility patterns are similar across cities, taking a concentric pattern where the central urban area is most attractive. However, employment accessibility varies more from city to city; moreover, the areas of highest employment accessibility tend to be decentralized within their respective regions. Overall, location-based accessibility indices are useful for exploring urban form, particularly with respect to issues of urban sprawl. Directions for future research are identified, including linking comparative urban accessibility measures to ongoing work on commuting, the jobs-housing balance, and urban structure.     

RANKING WORLD CITIES: MULTINATIONAL CORPORATIONS AND THE GLOBAL URBAN HIERARCHY

World-city literature often relies on a priori assumptions rather than quantifiable measures to discern the global urban hierarchy. In search of comparable international indicators, many studies use the corporate headquarters of multinational corporations (MNCs) as primary locational data. Recognizing that MNCs play a dominant role in the global economy, we argue that reliance on headquarters locations alone distorts the contours of the urban hierarchy. The method overstates the importance of urban centers in the developed countries and economies dominated by large corporations; conversely, it underestimates the importance of lower-level circuits of regional communication, transaction centers in developing countries, and cities in less-centralized economies. This bias is not simply a technical matter: it asserts the power of the core economies, while understating the diversity and complexity of global interactions. We propose to include MNC first-level subsidiary locations in a more refined measure of world-city status.     

Graphical design of world map projections

The design of new map projections has up until now required mathematical and cartographic expertise that has limited this activity to a small group of specialists. This article introduces the background mathematics for a software-based method that enables cartographers to easily design new small-scale world map projections. The software is usable even by those without mathematical expertise. A new projection is designed interactively in an iterative process that allows the designer to graphically and numerically assess the graticule, the representation of the continents, and the distortion properties of the new projection. The method has been implemented in Flex Projector, a free and open-source application enabling users to quickly create new map projections and modify existing projections. We also introduce new tools that help evaluate the distortion properties of projections, namely a configurable acceptance index to assess areal and angular distortion, a derived acceptance visualization, and interactive profiles through the distortion space of a projection. To illustrate the proposed method, a new projection, the Cropped Ginzburg VIII projection, is presented.     

2-Dreflectivity method and synthetic seismograms for irregularly layered structures -I. SH-wave generation

Summary. The reflectivity method for complete SH seismograms has been extended to two-dimensionally layered structures. The Aki-Larner technique is generalized to solve the integral equations for 2-D boundary conditions, and propagator matrices are enlarged to express a total SH wavefield. Synthetic seismograms in a soft basin are calculated for an incident plane-wave. They compare favourably with the results of the finite-element and finite-difference methods even in the later portion where asymptotic ray and beam theories break down. Synthetic seismograms due to a line force and a point dislocation are also presented.     

A SPATIAL AND TOPICAL ASSESSMENT OF DIGITAL GEOGRAPHIC DATABASE ACTIVITIES IN THE U.S.*

Characteristics of digital geographic databases throughout the U.S. are examined using data from a nationwide survey of potential digital data users/producers. The survey, conducted by Rand McNally-Infomap, identified more than 900 digital databases. Emphasis is on categories of data, differences in data at various scales and among organization types, and the spatial distribution of databases and data categories. Categories examined include boundaries, locational identifiers, property/valuation, utilities/energy/communication, transportation, socioeconomic, physical environment, and natural resource utilization.