On the stability of generalized second price auctions with budgets

The Generalized Second Price (GSP) auction used typically to model sponsored search auctions does not include the notion of budget constraints, which is present in practice. Motivated by this, we introduce the different variants of GSP auctions that take budgets into account in natural ways. We examine their stability by focusing on the existence of Nash equilibria and envy-free assignments. We highlight the differences between these mechanisms and find that only some of them exhibit both notions of stability. This shows the importance of carefully picking the right mechanism to ensure stable outcomes in the presence of budgets.Peer ReviewedPostprint (author's final draft

Development of a Gis Tool for Studying Territorial Impacts of Road Corridors

In this paper a Geographical Information System programme has been built to analyse and present the territorial impacts of P.A.TH.E (Patra-Athens-Thessalonica-Eyzonoi) international road in the area around it, in Greece, using social, economic and transport indicators. Using the Visual Basic programming and MapObjects components, an intelligent GIS programme is developed which everyone, with no knowledge to geodatabases, has the ability to use it. It has the capability to retrieve, interpret and render the statistical and cartographical features on the map, applying functions and provide suitable tools such as add layer (shapefile, grid, cad, image, coverage, etc.), zoom in, zoom out, pan, full extent, buffer, overlay, intersection, dot density patterns for polygons, calculation of statistics, identify, printing, copy and features classification. These tools are needed in order to generate specialized solutions for desktop mapping and spatial analysis. Moreover the application is enhanced with simple and useful interfaces to everyone who wants to correlate geographical and statistical information. The developed GIS has been used to study the territorial impacts in six hundred and four municipalities (ninety-three of them are crossed by the road) which are contained in twenty - three counties around the P.A.TH.E road. The administrative division NUTS V (municipality) has been selected as geographical level for the analysis. All the municipalities have been separated in three categories: • the first contains the municipalities which the road crosses, • the second includes the municipalities which are included in the same county with the municipalities in the first category but the road does not pass through them, • in the third belongs municipalities that are in neighbour counties of the second. Nine indicators (total and by sex population changes, population density, employment and unemployment rates, net migration, mobility, road density and land use) in four different time periods (1971, 1981, 1991 and 2001) have been used to study the spatial impacts of P.A.TH.E

Performance evaluation of a medium access control protocol for a distributed ARQ scheme in cooperative wireless networks

A performance evaluation of a medium access control protocol for a distributed ARQ scheme in cooperative wireless networks is presented in this paper. The protocol under evaluation is the Persistent Relay Carrier Sensing Multiple Access protocol (PRCSMA). The protocol was designed to be easily integrated in standard IEEE 802.11 networks in order to increase their performance and to extend coverage. The main goals of this paper are to present and to discuss the performance evaluation of the PRCSMA under different network configurations. Computer simulations demonstrate the robustness of the protocol under different scenarios.Peer ReviewedPostprint (author’s final draft

Fast branching algorithm for Cluster Vertex Deletion

In the family of clustering problems, we are given a set of objects (vertices of the graph), together with some observed pairwise similarities (edges). The goal is to identify clusters of similar objects by slightly modifying the graph to obtain a cluster graph (disjoint union of cliques). Hueffner et al. [Theory Comput. Syst. 2010] initiated the parameterized study of Cluster Vertex Deletion, where the allowed modification is vertex deletion, and presented an elegant O(2^k * k^9 + n * m)-time fixed-parameter algorithm, parameterized by the solution size. In our work, we pick up this line of research and present an O(1.9102^k * (n + m))-time branching algorithm

The social cost of congestion games by imposing variable delays

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this study, we describe a new coordination mechanism for non-atomic congestion games that leads to a (selfish) social cost which is arbitrarily close to the non-selfish optimal. This mechanism incurs no additional cost, in contrast to tolls that typically differ from the social cost as expressed in terms of delays.Peer ReviewedPostprint (author's final draft