Spatial interaction models represent a class of models that are used for modelling origin-destination flow data. The focus of this paper is on the log-normal version of the model. In this context, we consider spatial econometric specifications that can be used to accommodate two types of dependence scenarios, one involving endogenous interaction and the other exogenous interaction. These model specifications replace the conventional assumption of independence between origin-destination flows with formal approaches that allow for two different types of spatial dependence in magnitudes. Endogenous interaction reflects situations where there is a reaction to feedback regarding flow magnitudes from regions neighbouring origin and destination regions. This type of interaction can be modelled using specifications proposed by LeSage and Pace (2008) who use spatial lags of the dependent variable to quantify the magnitude and extent of the feedback effects, hence the term endogenous interaction. Exogenous interaction represents a situation where spillovers arise from nearby (or perhaps even distant) regions, and these need to be taken into account when modelling observed variations in flows across the network of regions. In contrast to endogenous interaction, these contextual effects do not generate reactions to the spillovers, leading to a model specification that can be interpreted without considering changes in the long-run equilibrium state of the system of flows. As in the case of social networks, contextual effects are modelled using spatial lags of the explanatory variables that represent characteristics of neighbouring (or more generally connected) regions, but not spatial lags of the dependent variable, hence the term exogenous interaction. In addition to setting forth expressions for the true partial derivatives of non-spatial and endogenous spatial interaction models and associated scalar summary measures from Thomas-Agnan and LeSage (2014), we propose new scalar summary measures for the exogenous spatial interaction specification introduced here. An illustration applies the exogenous spatial interaction model to a flow matrix of teacher movements between 67 school districts in the state of Florida.
1 Systems of Innovation: An Attractive Conceptual Framework for Comparative Innovation Research.- 2 The Vienna Metropolitan System of Innovation.- 3 The Barcelona Metropolitan System of Innovation.- 4 The Stockholm Metropolitan System of Innovation.- 5 A Retrospect.- Appendix: A The Vienna Metropolitan Innovation System.- Appendix: B The Barcelona Metropolitan Innovation System.- Appendix: C The Stockholm Metropolitan Innovation System.- References.- List of Figures.- List of Tables.- Author Index.
Über die Frostresistenz und ihre Beziehungen zur endogenen Ruheperiode bei Malusarten und deren F1 - bzw. R1 -Nachkommen was published in Band 24, Heft 3 1976 on page 231.
No abstract is provided for this article.
Neural spatial interaction models are receiving much attention in recent years because of their powerful universal approximation properties. They are essentially devices for non-parametric statistical inference, providing an elegant formalism. Neural spatial interaction models have shown considerable successes in a variety of application contexts. The paper discusses a novel modular methodology for neural spatial interaction model identification. We briefly introduce the motivation for the two main constituent components of the methodology: model selection and model adequacy testing. Then we discuss the issues involved in model selection and make a clear distinction between the problems of estimation and model specification. Though major emphasis will be laid on the case of unconstraint spatial interaction, some attention will be paid also to the singly constrained case. The methodology will be illustrated in a real world context. KEYWORDS: Neural Spatial Interaction Models; Model Selection and Model Adequacy Testing; Unconstraint Spatial Interaction.
The focus of this paper is on cross-region R&D collaboration funded by the 5th EU Framework Programme (FP5). The objective is to measure distance, institutional, language and technological barrier effects that may hamper collaborative activities between European regions. Particular emphasis is laid on measuring discrepancies between two types of collaborative R&D activities, those generating output in terms of scientific publications and those that do not. The study area is composed of 255 NUTS-2 regions that cover the pre-2007 member states of the European Union (excluding Malta and Cyprus) as well as Norway and Switzerland. We employ a negative binomial spatial interaction model specification to address the research question, along with an eigenvector spatial filtering technique suggested by Fischer and Griffith (2008) to account for the presence of network autocorrelation in the origin-destination cooperation data. The study provides evidence that the role of geographic distance as collaborative deterrent is significantly lower if collaborations generate scientific output. Institutional barriers do not play a significant role for collaborations with scientific output. Language and technological barriers are smaller but the estimates indicate no significant discrepancies between the two types of collaborative R&D activities that are in focus of this study.
Based on the most recent evidence from phylogenetic analyses of Veronica and its related genera, we propose a new infratribal and infrageneric rearrangement for Veroniceae and Veronica . These recent analyses have settled the long dispute about the relationship of the Northern Hemisphere Veronica and the Southern Hemisphere Hebe complex and have shown the derivation of the latter from within the former. Other currently recognized genera such as Synthyris and Pseudolysimachion are also derived from within Veronica . A classification based on monophyletic genera therefore needs to either lump some well recognized genera into a large genus Veronica or split Veronica into several genera that seem impossible to separate using morphological or structural characters. We discuss the advantages and disadvantages and conclude that it is best to recognize a large genus Veronica (including Hebe, Parahebe, Chionohebe, Heliohebe, Detzneria, Derwentia, Pseudolysimachion, Synthyris and Besseya ) with 13 subgenera, along with 8 other genera, Scrofella, Veronicastrum (inclusive of Calorhabdos and Botryopleuron ), Lagotis, Wulfenia, Kashmiria, Picrorhiza, Wulfeniopsis and Paederota , in Veroniceae .
. Parameter estimation is one of the central issues in neural spatial interaction modelling. Current practice is dominated by gradient based local minimization techniques. They find local minima efficiently and work best in unimodal minimization problems, but can get trapped in multimodal problems. Global search procedures provide an alternative optimization scheme that allows to escape from local minima. Differential evolution has been recently introduced as an efficient direct search method for optimizing real-valued multi-modal objective functions (Storn and Price 1997). The method is conceptually simple and attractive, but little is known about its behavior in real world applications. This article explores this method as an alternative to current practice for solving the parameter estimation task, and attempts to assess its robustness, measured in terms of in-sample and out-of-sample performance. A benchmark comparison against backpropagation of conjugate gradients is based on Austrian interregional telecommunication traffic data.
Die neue grenzüberschreitende Eisenbahnbrücke der Österreichischen Bundesbahnen (ÖBB) verbindet den Schweizer Kanton St. Gallen mit dem österreichischen Bundesland Vorarlberg. Sie liegt auf dem eingleisigen Streckenabschnitt St. Margrethen (CH) – Lauterach (A) und führt bei Lustenau über den Rhein. Dieser Streckenabschnitt steht im Eigentum der ÖBB und ist Teil der internationalen Eisenbahnstrecke Zürich – Bregenz – München. Mit dem Neubau der Rheinbrücke wurden die Projektziele Hochwasserschutz sowie eine Fahrzeitverkürzung auf dem österreichischen Streckenabschnitt umgesetzt. Ausgelöst durch die Vorgaben der internationalen Rheinregulierung (IRR) zum Hochwasserschutz am Rhein (Abflusskapazität neu von 4300 m³/s) musste die Brückenunterkante um 2 m gegenüber dem Bestand angehoben und die Trassenführung um rund 12 m nach Süden verschoben werden. Diese neue Linienführung ermöglichte die Anhebung der Streckengeschwindigkeit von bisher 60 km/h auf 90 km/h. Im Projektabschnitt waren sieben weitere Brückenbauwerke betroffen und mussten neu errichtet werden. Bereits in der Planungsphase wurde die intensive Zusammenarbeit mit der Internationalen Rheinregulierung (IRR), dem Land Vorarlberg und den Schweizer Behörden gesucht. Für die Erstellung der statischen Berechnung der grenzüberschreitenden Brücke wurde bilateral vereinbart, dass die Eurocodes in Verbindung mit den österreichischen nationalen Festlegungen und nationalen Ergänzungen heranzuziehen sind. The new ÖBB Rhine Bridge near Lustenau, Austria – an exceptional arch bridge. The new international railway bridge of the Austrian federal railways (ÖBB) connects the Swiss canton of St. Gallen with the Austrian federal state of Vorarlberg. This bridge is part of the single track route from St. Margrethen (CH) to Lauterach (A) and crosses the river Rhine at Lustenau. The tracks of this section are owned by the ÖBB and they form part of the international route from Zurich via Bregenz to Munich. The new bridge fulfills the requirements of flood control and reduction of travel time. Due to the requirements of the International Rhine Regulation (IRR) to allow a flow capacity of 4300 m³/s, the soffit of the new bridge had to be raised by 2 m compared with the old bridge and the new rail axis was offset 12m to the south. The new aligning allowed for an increase of speed from 60 km/h to 90 km/h. The project includes seven other bridges that had to be newly erected. During planning, close contact was held with the IRR, the federal state of Vorarlberg and Swiss authorities. In a bilateral agreement, it was defined that the Eurocode with Austrian national application documents would be used for the design.
This article presents a theoretical growth model that accounts for technological interdependence among regions in a Mankiw-Romer-Weil world. The reasoning behind the theoretical work is that technological ideas cannot be fully appropriated by investors and these ideas may diffuse and increase the productivity of other firms. We link the diffusion of ideas to spatial proximity and allow ideas to flow to nearby regional economies. Through the magic of solving for the reduced form of the theoretical model and the magic of spatial autoregressive processes, the simple dependence on a small number of neighboring regions leads to a reduced form theoretical model and an associated empirical model where changes in a single region can potentially impact all other regions. This implies that conventional regression interpretations of the parameter estimates would be wrong. The proper way to interpret the model has to rely on matrices of partial derivatives of the dependent variable with respect to changes in the Mankiw-Romer-Weil variables, using scalar summary measures for reporting the estimates of the marginal impacts from the model. The summary impact measure estimates indicate that technological interdependence among the European regions works through physical rather than human capital externalities.
This paper attempts to develop a mathematically rigid and unified framework for neural spatial interaction modeling. Families of classical neural network models, but also less classical ones such as product unit neural network ones are considered for the cases of unconstrained and singly constrained spatial interaction flows. Current practice appears to suffer from least squares and normality assumptions that ignore the true integer nature of the flows and approximate a discrete‐valued process by an almost certainly misrepresentative continuous distribution. To overcome this deficiency we suggest a more suitable estimation approach, maximum likelihood estimation under more realistic distributional assumptions of Poisson processes, and utilize a global search procedure, called Alopex, to solve the maximum likelihood estimation problem. To identify the transition from underfitting to overfitting we split the data into training, internal validation, and test sets. The bootstrapping pairs approach with replacement is adopted to combine the purity of data splitting with the power of a resampling procedure to overcome the generally neglected issue of fixed data splitting and the problem of scarce data. In addition, the approach has power to provide a better statistical picture of the prediction variability. Finally, a benchmark comparison against the classical gravity models illustrates the superiority of both, the unconstrained and the origin constrained neural network model versions in terms of generalization performance measured by Kullback and Leibler's information criterion.
Die Bedeutung der Merkmale Blütenbesatz, Blütenfrostschaden und Ertrag für die Bewertung der obstbaulichen Leistungsfähigkeit von Apfelunterlagen-Zuchtklonen was published in Band 28, Heft 8 1980 on page 459.
The paper examines uncoated weathering steel as applied to bridge construction. Early experiences with this material indicate that some misunderstandings exist about the specific material properties of weathering steel, which the author seeks to correct. Improved criteria for design, construction and maintenance are presented. Economic and aesthetic aspects of weathering steel for bridge structures are also considered.
The current AREVA Gen 3+ PWR designs (EPR™ and ATMEA1) are based on the proven defense-in-depth safety concepts inherited from their predecessors, the French “N4” and the German “Konvoi” reactors. Complemented by specific enhancements, including higher redundancy and diversity as well as the use of passive systems, this leads to very low values of the core damage frequency (CDF). Notwithstanding this very low probability, dedicated design measures have been implemented to improve the response of the plant in case of a postulated severe accident (SA) with core melting. This way not only the frequency of large-early-releases (LERF) but also the related radiological consequences are drastically reduced. Situations that potentially lead to high loads that can challenge the short-term integrity of the containment, like RPV melt-through under high pressure, energetic hydrogen/steam explosions, as well as long-term containment failure caused by internal over-pressure are avoided by a combination of preventive measures and dedicated systems. At the example of the EPRTM, the paper gives an overview of the severe accident mitigation strategy and the related measures and systems of AREVAs current Gen 3+ reactors, with special focus on the function of the core melt stabilization system.
Salivary glands of late third instar larvae of Drosophila melanogaster were isolated at a developmental stage when the release of ecdysone had already taken place. They were then incubated in a chemically defined medium. An ecdysone-dependent developmental puff sequence was measured in vitro and influenced by adding various substances or by changing iso-osmotically the sodium or potassium content of the medium. Trinactin, valinomycin, N-ethylmaleimide and KCN blocked the puff sequence, i.e. the regression of the early and the induction of the late ecdysone-dependent puffs probably by increasing the Na+ influx and depleting the ATP content of the cell. A medium that contained Na+ as the only monovalent cation decreased the size of the late ecdysone-dependent puffs and increased the size of other puffs, such as 50 CD. Addition of tetrodotoxin to the normal medium had the opposite effect, i.e., it increased 63 E and inhibited 50 CD. Na+ free medium, inhibition of K+ flux by tetraethylammonium chloride, and application of ouabain did not considerably influence the size of the puffs measured. It is concluded from these results that Na+ in particular has an inhibitory effect on the induction of late ecdysone-dependent puffs. Na+ (and perhaps also K+) may act by modulating the effect of proteins that are involved in gene control mechanisms.
The analysis presented in this article focuses on seigniorage revenues in five Central and Eastern European Countries: Bulgaria, the Czech Republic, Hungary, Poland and Romania. A comprehensive discrete period accounting framework for measuring the sources and uses of seigniorage in the 1990s is presented. The framework is based upon the gross concept of seigniorage that defines seigniorage in the broadest possible sense as the sum of revenues resulting from the monopoly power to issue money. Legal, institutional and operational details which are relevant for the creation of base money in a country are taken into account. The article reveals similarities and differences in seigniorage wealth between the countries under scrutiny, evaluates the magnitude of seigniorage and shows that accession to the European Monetary Union will create significant once-and-for-all gains of seigniorage wealth for the countries resulting from redistributing seigniorage wealth.
Aus der Subtribus Veronicinae wurden an Material aus Österreich, Sardinien, Sizilien, Serbien, der Türkei, dem Irak und Afghanistan an insgesamt
