MODELING SPATIAL AUTOCORRELATION IN SPATIAL INTERACTION DATA: AN APPLICATION TO PATENT CITATION DATA IN THE EUROPEAN UNION*

ABSTRACT Spatial interaction models of the gravity type are widely used to model origin–destination flows. They draw attention to three types of variables to explain variation in spatial interactions across geographic space: variables that characterize an origin region of a flow, variables that characterize a destination region of a flow, and finally variables that measure the separation between origin and destination regions. This paper outlines and compares two approaches, the spatial econometric and the eigenfunction‐based spatial filtering approach, to deal with the issue of spatial autocorrelation among flow residuals. An example using patent citation data that capture knowledge flows across 112 European regions serves to illustrate the application and the comparison of the two approaches.     

THE ANALYSIS OF GOLD COINS—A COMPARISON OF RESULTS OBTAINED BY NON-DESTRUCTIVE METHODS

This paper discusses a systematic difference between the results found when one series of Dark-Age gold coins were analysed both by neutron activation and by specific gravity analysis and when a second series of similar coins was analysed by the Oxford Milliprobe and by specific gravity. No reason is given for this systematic difference, although there is evidence that all three methods are slightly in error, two of them giving results for gold which are too high and the specific gravity method giving results which are too low.     

Gravity waves from O2 nightglow during the AIDA '89 campaign II: numerical modeling of the emission rate/temperature ratio, η

The dependence of η, the ratio of emission rate fluctuation to temperature fluctuation, on the gravity wave parameters and chemical parameters is developed using a model for the O₂ airglow's response to a gravity wave. The model is in the Eulerian frame of reference using the traditional linearization and perturbation method. Two photochemical mechanisms, the three-body recombination mechanism and the two-step transfer mechanism and two kinds of waves, evanescent and internal, are separately discussed in detail. Results of the model are compared with other existing models of η(O₂) and found to be in agreement. The predictions of this model agree fairly well with the available gravity wave measurements in the magnitude of η, but the predicted phases are somewhat larger than those normally observed.     

不同模型在镇域空间相互作用中的应用与比较分析——以湖北省大冶市为例

镇域尺度的空间相互作用研究对促进城乡统筹和城镇体系规划具有重要意义。本文借鉴最新研究成果,从理论及实践层面对镇域空间相互作用研究进行了探索,提出一种基于空间可达性的辐射模型,并与传统重力模型进行比较分析。以大冶市16个乡镇为例进行实例研究,结果表明:1辐射模型与实测数据的相似度较高,可以更好地反映镇域空间相互作用的客观规律;2两种模拟方法在体现空间相互作用的方向性以及结构特征方面具有显著差异;3辐射模型中影响范围的引入以及空间可达性对区域异质性的体现是其与重力模型的主要区别。     

Theoretical Underpinnings of the Gravity Hypothesis

Various theoretical rationalizations of the gravity hypothesis for spatial interaction are examined. Deterministic utility theory cannot account for variability in individual behavior. Choice models based on Luce's axiom contain some inconsistencies. Random utility theory provides a probabilistic formulation that is internally consistent, and also solves the aggregation problem. However, investigation reveals that, although this provides a theoretical justification for gravity-like behavior, the assumptions made are sufficiently unrealistic to cast doubt on the empirical validity of the gravity hypothesis.     

我国人口与社会经济重心的动态演变

本文利用区域重心的概念及其模型,计算了1978-2002年我国逐年的人口重心和社会经济重心,得到人口重心和社会经济重心的动态演变轨迹,分析了人口和社会经济发展区域差异的动态变化及其驱动因子,并对人口重心和社会经济发展重心的动态演变趋势进行了对比分析。     

Average and core silver content of ancient-debased coins via neutron diffraction and specific gravity

The measurement of the fineness of debased ancient silver coins has proven to be a very difficult issue, which has been studied for a long time. In this paper, this subject is analysed, and the various consequences of the silver surface enrichment (SSE) are discussed exploiting the most recent investigations. A new model is proposed for the complex object that is an ancient-debased silver coin, based on the silver profiles measured on some sectioned specimens. The model is applied to a sample of 43 coins, mainly Roman victoriati, Cisalpine and Illyrian drachms (from late III to I century B.C.). The coins are investigated in two different ways: neutron diffraction (ND) and specific gravity (SG). The results of the two measurements are combined via the proposed model to provide a more complete numismatic information of the original fineness of the monetary alloy. As a result, a relation between SSE thickness and SG is derived, which, for these coinages, allows to estimate the original alloy silver content from a simple SG measurement; the same method can be used to study other debased coinages, provided that all the procedure (ND and SG) is applied.     

Gravity wave saturation and eddy diffusion in the middle atmosphere

A discussion is given of gravity wave saturation and its relation to eddy diffusion in the middle atmosphere. Attention is focused on the saturation process and some of its observable manifestations. It does not serve as a review of all related work. Although a theoretical point of view is taken, the emphasis is on which wave parameters need be measured to predict quantitatively the influence of gravity waves on eddy transport. The following considerations are stressed: the variation of spectra with observation time T; that eddy diffusivities are determined by velocity spectra; the anisotropic nature of diffusivity; a unified approach to saturation; an attempt to make eddy diffusivity more precise; the relationship between eddy diffusivity and wave dissipation.The subjects of ‘wave drag’ (momentum flux deposition) and heat flux need only be treated briefly, because they are related to eddy diffusivity in simple ways. Consideration is also given to two different theoretical mechanisms of wave saturation—wave induced convective instability and strong nonlinear wave interactions. The saturation theory is then used to predict a globally averaged height profile of vertical diffusivity in the middle atmosphere. This calculation shows that gravity waves are a major contributor to eddy diffusion from heights of 40–110 km, and that they are significant down to 20 km. A more detailed calculation of wave induced eddy diffusion, including latitudinal and seasonal variations, can be made if wave velocity spectra become available. The paper closes with recommendations for future research.     

1990-2009年中国区域差异与空间格局——以人口重心与经济重心为例

利用至2009年的省级数据,与前人结论进行了对比,纠正了某些认识。①与我国几何中心相比,人口重心和经济重心均表现出不均衡性;②政策因素和由此导致的开放程度、开放时序的差别,是区域差异的最主要原因之一;③经济危机是经济重心产生剧烈跳动的主要原因;④广东省人口的快速增长是人口重心持续的西南向移动的真正原因,而经济重心的东南向移动是珠江三角洲和长江三角洲经济发展共同作用的结果;⑤人口重心和第一产业重心较为吻合,而与经济重心、第二产业重心、第三产业重心较为离散。     

THE GRAVITY MODEL AND HIERARCHICAL SPATIAL SYSTEMS: THEORETICAL AND EMPIRICAL OBSERVATIONS

The gravity model in its basic forms postulates that the volume of interaction between two places will be positively related to the populations (masses) of the two places and inversely related to their distance apart. Although it is not strictly speaking a hierarchical model, it is often used to explain flows among places that constitute a hierarchical spatial system. This paper is specifically concerned with the effect of hierarchical spatial structure on the performance of the gravity model. Accordingly, I will examine first the effect of hierarchical structure on the volume of interaction between places and second the degree to which the gravity model incorporates these hierarchical effects. Third, suggestions will be made for the improvement of the gravity model's performance by an explicit incorporation of a hierarchical element. The performance of the gravity model will be examined for both one-way and two-way flows between places.     

Single and Multiscale Models of Process Spatial Heterogeneity

Recent work in local spatial modeling has affirmed and broadened interest in multivariate local spatial analysis. Two broad approaches have emerged: Geographically Weighted Regression (GWR) which follows a frequentist perspective and Bayesian Spatially Varying Coefficients models. Although several comparisons between the two approaches exist, recent developments, particularly in GWR, mean that these are incomplete and missing some important axes of comparison. Consequently, there is a need for a more thorough comparison of the two families of local estimators, including recent developments in multiscale variants and their relative performance under controlled conditions. We find that while both types of local models generally perform similarly on a series of criteria, some interesting and important differences exist.     

Comprehensive meteorological modelling of the middle atmosphere: a tutorial review

This paper reviews the current state of comprehensive, three-dimensional, time-dependent modelling of the circulation in the middle and upper atmosphere from a meteorologist's perspective. The paper begins with a consideration of the various components of a comprehensive model (or general circulation model, GCM), including treatments of processes that can be explicitly resolved and those that occur on scales too small to resolve (and that must be parameterized). The typical performance of GCMs in simulating the tropospheric climate is discussed. Then some important background on current ideas concerning the general circulation of the stratosphere and mesosphere is presented. In particular, the transformed-Eulerian mean flow formalism, the role of vertically-propagating internal gravity waves in driving the large-scale circulation, and the notion of a stratospheric surf zone are all briefly reviewed. Using this background as a guide, some middle atmospheric GCM results are discussed, with a focus on simulations made recently with the GFDL ‘SKYHI’ troposphere-stratosphere-mesosphere GCM. The presentation attempts to emphasize the interaction between theory and comprehensive modelling. Many theoretical notions cannot be confirmed in detail from observations of the real atmosphere due to the various limitations in the observational methods, but can be very completely examined in GCMs in which every atmospheric variable is known perfectly (within the limits of the numerical methods). It will be shown that our understanding of both the role of gravity waves in the general circulation and the nature of the stratospheric surf zone has benefited from analysis of GCM results.From the point of view of the upper atmosphere, one of the most interesting aspects of GCMs is their ability to generate a self-consistent field of upward-propagating gravity waves. This paper concludes with a discussion of the gravity wave field in the middle atmosphere of GCMs. Comparisons of the explicitly-resolved gravity wave field in the SKYHI model with observations are quite encouraging, and it seems that the model is capable of producing a gravity wave field with many realistic features. However, the simulated horizontal spectrum of the eddy momentum fluxes associated with the waves is quite shallow, suggesting that much of the spectrum that is important for maintaining the mean circulation is not explicitly resolvable in current GCMs. A brief discussion of current efforts at parameterizing the mean flow effects of the unresolvable gravity waves is presented.     

A method of fitting the gravity model based on the Poisson distribution

"In this paper, [the authors] suggest an alternative method for fitting the gravity model. In this method, the interaction variable is treated as the outcome of a discrete probability process, whose mean is a function of the size and distance variables. This treatment seems appropriate when the dependent variable represents a count of the number of items (people, vehicles, shipments) moving from one place to another. It would seem to have special advantages where there are some pairs of places between which few items move. The argument will be illustrated with reference to data on the numbers of migrants moving in 1970-1971 between pairs of the 126 labor market areas defined for Great Britain...."     

Effects of Base and Lift Joints on the Dynamic Response of Concrete Gravity Dams to Pulse-Like Excitations

Near-fault earthquakes with forward-directivity effects produce pulse-like excitations. This article studies the dynamic response of monolithic and cracked sections of gravity dam under symmetric and anti-symmetric pulse-like excitations. The pulses are generated by the modified Gabor Wavelet transform. Two main characteristics of the pulses are pulse period and amplitude. The prescribed cracks are located along the base and two distinct lift joints through the dam body. The dam is modeled along with its reservoir using finite element method. The effects of base and lift joints, pulses shape, period, and amplitude, and reservoir height on the dam dynamic response are studied.     

METROPOLITAN AND NON-METROPOLITAN POPULATION TRENDS IN CANADA, 1966–1982

This paper discusses broad population movements within and between metropolitan and nonmetropolitan regions in Canada during the recent past. It is based on an annual series of aggregate migration at the metropolitan level. Three complementary approaches are used in order to distill information from this vast array of interregional flows. The first is based on net migration. The second, disequilibrium analysis, is based on the difference between the observed population shares of regions and a set of calculated steady-state population shares which would result if the currently observed set of interregional migration rates remained constant. Both approaches indicate short-term effects of migration on the evolving pattern of regional growth and decline. The third approach, based on aggregate interregional flows, allows one to observe some changes in migration behaviour which are not made evident by the first two approaches.     

Tropospheric gravity waves and their possible association with medium-scale travelling ionospheric disturbances

Analysis of pressure fluctuations observed over a period of several days using an array of microbarographs has shown the existence of long trains of gravity waves with two or more waves often present simultaneously. Meteorological data from radiosonde ascents indicates that many of the waves have a velocity which matches that of the background wind at some level within the troposphere. Generally this height corresponds to that of a frontal zone marking the transition between air masses and it is suggested that the waves may have been generated by shear flow instability within the frontal layer. Theoretical considerations, based on a three-layer model troposphere, show that some of the observed waves could have been ducted in or near the frontal zone. Some evidence is found to indicate that a non-linear wave-wave interaction between pairs of waves occurring simultaneously in the frontal zone could yield secondary waves with the characteristics of the gravity waves which had been observed in the thermosphere at appropriate times and whose group paths were traced to source regions in the troposphere in the general vicinity of the microbarograph array.     

Where does all the talent flow? Migration of young graduates and nongraduates,Canada 1996–2001

It has recently been suggested that cities and regions should focus upon attracting talented individuals as a means to develop. Such a suggestion implies two things: first that it is possible to meaningfully alter migration flows by way of local policy, and second that these flows have an effect on local growth (and not the reverse as has generally been admitted). In this paper, we begin to investigate the empirical foundations of such assertions by examining some structural determinants of graduate migration flows by comparing them, in a gravity model context, to flows of nongraduates. Our contention is that, if migration flows are structured by such factors, then policies aimed at modifying flows—and any research purporting to give such policy advice—must first take them into account. We show that migration flows are strongly dependent on basic gravity variables such as size and distance, but that these and other variables (such as income differences, presence of graduates and border effects) do not affect all flows equally. Furthermore, we show that certain factors that are assumed to be local (such as wage levels) in fact only operate at a provincial level. Thus policies implemented locally may have little or no effect if they are manipulating factors that operate at a different scale.     

Interference of tidal and gravity waves in the ionosphere and an associated sporadic E-layer

Observations made on 10 July 1987 with the EISCAT UHF radar are presented. The F-region measurements of both electron density and field-aligned ion velocity show that an upward propagating gravity wave with a period of about 1 h is present. The origin of the gravity wave is probably auroral. The E-region ion velocities show a tidal wave and both upward and downward propagating gravity waves. The gravity waves have three dominant periods with a possible harmonic relationship and similar vertical wavelengths. These waves are either reflected at a single reflection level, ducted between two levels, or they are generated in a non-linear interaction between gravity and tidal waves. The E-region electron density is dominated by particle precipitation. After a short burst of more intense precipitation, a sporadic E-layer forms at 105km and then disappears 40min later. Within this time, the layer rises and falls by a few kilometres, following closely the motion of a convergent null in the velocity profile. We suggest that the formation and destruction of this layer is controlled by both the precipitation, which indirectly provides a source of metal ions through charge exchange, and the superposition of gravity waves and the tidal wave.     

MAXIMUM LIKELIHOOD ESTIMATION OF GRAVITY MODEL PARAMETERS

ABSTRACT. It is shown that, under some very mild conditions, maximum likelihood estimates of gravity model parameters exist and are unique (up to a scale transformation for some parameters). An algorithm for finding such estimates is also proposed.     

陕西省社会经济重心与环境污染重心的演变路径及其对比分析

本文在考察重心研究现状的基础上,提出了重心路径几何图示分析法,计算了1989-2003年陕西省社会经济重心与环境污染重心的演变路径,从移动方向、移动距离、路径对比、斜率分析、空间相关性分析等多角度阐述了社会经济重心与环境污染重心的动态变化及空间联系。