Search results for " technologies."
showing 10 items of 2689 documents
Correlation between school dropout and gross domestic product in the emerging countries of Central and Eastern Europe
2020
By school dropout is meant leaving the educational system, regardless of the reached level, before obtaining a qualification or a complete proffesional training or before the end of the study cycle started (Doron & Parot, 2006). Although there are numerous researches on school dropout, we consider that it is necessary to study the relationship it has with the level of development of a country, in order to identify new causes and possible solutions to this phenomenon. In this study we included seven emerging countries of Central and Eastern Europe: Bulgaria, Czech Republic, Poland, Romania, Slovakia, Slovenia and Hungary. Thus, we analyzed the correlation between the annual gross domesti…
Schatten über der Schwarzarbeit
2008
Die Diskussion uber Messung, Grosenordnung und Konsequenzen der Schwarzarbeit steht bereits deshalb unter einem Schatten, der den Blick dafur truben kann, weil Enste und Schneider trotz jahrelanger Befassung mit dem Thema Schwarzarbeit und Schattenwirtschaft nicht systematisch zu unterscheiden vermogen. Ihre Schatzungen fur die Dimension des Phanomens beruhen zudem generell auf wissenschaftlich nicht haltbaren Vorgehensweisen, die sie gleichwohl repetitiv anwenden. Die unterstellten Einnahmenverluste beim Staat ergeben sich im Ubrigen lediglich bei Vernachlassigung mikrookonomisch bedeutsamer Budgetrestriktionen sowie durch Auserachtlassung zwingender makrookonomischer Kreislaufzusammenhang…
Die volkswirtschaftliche Bedeutung von Schwarzarbeit
2007
Die Schwarzarbeit wird in der finanzpolitischen Diskussion in Deutschland als volkswirtschaftlich gewichtig angesehen, und es werden ihr erhebliche Einnahmenverluste des Staates zugeschrieben. Die vorliegende Arbeit hinterfragt diese Behauptungen. Nach einer Definition der Schwarzarbeit und ihrer Abgrenzung gegenuber ahnlichen Sachverhalten wird die unterstellte volkswirtschaftliche Bedeutung zuruckgewiesen. Auserdem lasst sich im Rahmen einer konsistenten okonomischen Analyse zeigen, dass dem Staat durch Schwarzarbeit keinerlei Einnahmeausfalle entstehen. Nach allem ist das Ausmas der Schwarzarbeit in Deutschland gering, wobei gleichwohl allokative Wirkungen der Schwarzarbeit nicht auszusc…
Territorial determinants and NUTS-3 regional performance: a spatial analysis for Italy across the crisis
2018
This paper analyses the differential impact of several territorial determinants of the economic performance of Italian provinces (NUTS 3 level). as measured by per capita GDP, export and employment growth from 1999 to 2014. It covers both the pre‐crisis and the crisis period and stresses the role of geographical proximity in shaping local performance over a wide set of explanatory variables. In order to do so, we employ, firstly, a spatial Durbin model which enables us to discriminate between direct and indirect effects and to highlight the possible contagion or crowding‐out spatial effects for each territorial dimension affecting growth. Then, we extend the analysis by allowing for the pos…
Fuzzy Portfolio Selection Models for Dealing with Investor’s Preferences
2017
This chapter provides an overview of the authors’ previous work about dealing with investor’s preferences in the portfolio selection problem. We propose a fuzzy model for dealing with the vagueness of investor preferences on the expected return and the assumed risk, and then we consider several modifications to include additional constraints and goals.
Drone arc routing problems
2018
[EN] In this article, we present some drone arc routing problems (Drone ARPs) and study their relation with well-known postman ARPs. Applications for Drone ARPs include traffic monitoring by flying over roadways, infrastructure inspection such as by flying along power transmission lines, pipelines or fences, and surveillance along linear features such as coastlines or territorial borders. Unlike the postmen in traditional ARPs, drones can travel directly between any two points in the plane without following the edges of the network. As a consequence, a drone route may service only part of an edge, with multiple routes being used to cover the entire edge. Thus the Drone ARPs are continuous o…
Variable Fixing for Two-Arc Sequences in Branch-Price-and-Cut Algorithms on Path-Based Models
2020
Variable fixing by reduced costs is a popular technique for accelerating the solution process of mixed-integer linear programs. For vehicle-routing problems solved by branch-price-and-cut algorithms, it is possible to fix to zero the variables associated with all routes containing at least one arc from a subset of arcs determined according to the dual solution of a linear relaxation. This is equivalent to removing these arcs from the network used to generate the routes. In this paper, we extend this technique to routes containing sequences of two arcs. Such sequences or their arcs cannot be removed directly from the network because routes traversing only one arc of a sequence might still b…
Contributions to Branch-and-Price-and-Cut Algorithms for Routing Problems
2019
This article deals with new exact branch-and-price-and-cut algorithms for the solution of routing problems. Specialized methods for the pickup-and-delivery problem (PDP), the truck-and-trailer routing problem (TTRP), the periodic vehicle routing problem (PVRP) and a service network design and hub location problem (SNDHLP) are presented. We develop a new technique for the acceleration of bidirectional labeling algorithms by a dynamic choice of the merge point. Moreover, for variants of the PDP, the bidirectional labeling can be effectively applied for the first time. In the TTRP, we model the extension to a 2 days planning horizon and the consideration of a quantity-dependent transfer time. …
The facility location problem with capacity transfers
2020
Abstract This paper explores the concept of capacity transfer in the context of capacitated facility location problems. This is accomplished by assuming that facilities with surplus capacity/production can cooperate with those facing shortage by transferring part of that capacity/production. Such a transfer incurs a cost that nonetheless may be compensated by savings both in the installation costs and in the distribution costs. Mixed-integer mathematical programming models are proposed for the problem. A distinction is made between the case in which the triangle inequality holds for the transfer costs and the case in which it does not. We present compact models, which are enhanced with vali…
Some personal views on the current state and the future of locational analysis
1998
In this paper a group of participants of the 12th European Summer Institute which took place in Tenerife, Spain in June 1995 present their views on the state of the art and the future trends in Locational Analysis. The issues discussed include modeling aspects in discrete Location Theory, the influence of the distance function, the relation between discrete, network and continuous location, heuristic techniques, the state of technology and undesirable facility location. Some general questions are stated regarding the applicability of location models, promising research directions and the way technology affects the development of solution techniques.