Intelligent search in social communities of smartphone users

Social communities of smartphone users have recently gained significant interest due to their wide social penetration. The applications in this domain, however, currently rely on centralized or cloud-like architectures for data sharing and searching tasks, introducing both data-disclosure and performance concerns. In this paper, we present a distributed search architecture for intelligent search of objects in a mobile social community. Our framework, coined SmartOpt, is founded on an in-situ data storage model, where captured objects remain local on smartphones and searches then take place over an intelligent multi-objective lookup structure we compute dynamically. Our MO-QRT structure optimizes several conflicting objectives, using a multi-objective evolutionary algorithm that calculates a diverse set of high quality non-dominated solutions in a single run. Then a decision-making subsystem is utilized to tune the retrieval preferences of the query user. We assess our ideas both using trace-driven experiments with mobility and social patterns derived by Microsoft’s GeoLife project, DBLP and Pics ‘n’ Trails but also using our real Android SmartP2P (http://smartp2p.cs.ucy.ac.cy/) system deployed over our SmartLab (http://smartlab.cs.ucy.ac.cy/) testbed of 40+ smartphones. Our study reveals that SmartOpt yields high query recall rates of 95 %, with one order of magnitude less time and two orders of magnitude less energy than its competitors.     

An investigation of the suitability of some Greek wood species in wood-cement composites manufacture

Eight Greek wood species were examined as potential raw materials for wood-cement composites. Hydration tests were carried out to determine the inhibitory index in order to classify wood-cement compatibility. The mixture with the highest compatibility (low inhibition) was that of poplar and cement with an inhibition index of 7.44.     

Determination of SIF in a cracked plane orthotropic strip by the Wiener-Hopf technique

The stress intensity factor for a long cracked strip was determined within the context of the linear orthotropic clasticity. The body had the form of an infinite strip containing a semi-infinite crack at the middle distance of the strip faces. Fourier transforms in combination with the Wiener-Hopf technique were employed to evaluate asymptotically the cleavage stress and its intensity at the crack tip.

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Résumé On détermine le facteur d'intensité d'entaille relatif à une longue bande fissurée, dans un contexte d'élasticité linéaire et orthotrope. On considère un corps ayant la forme d'une bande infinie et comportant une fissure semi-infinie à mi-distance des faces de la bande. On recourt à une transformée de Fourier en combinaison avec la technique de Wiener-Hopf pour évaluer par voie asymptotique la tension de clivage et son intensité à l'extrémité de la fissure.

     

The potential for a generic approach to certification of safety critical systems in the transportation sector

This paper investigates the potential for common treatment of certification of safety critical programmable electronic systems in the transportation industries. It contains a comparative review of new, emerging international standards that are likely to influence certification procedures in the railway, automotive and aerospace sectors in the future. These include the EUROCAE/SAE aerospace guidelines, the CENELEC railway standards and IEC-61508, the draft international standard on safety related systems. The review identifies the common and divergent requirements for certification among these standards. Based on significant commonalities, we have developed a common process model for the development, assessment and certification of safety critical programmable electronic systems which could be acceptable in the framework of each standard in consideration. The proposed model contains a system development and a safety assessment process which rationalises and unifies the common requirements among the standards in these areas. In addition, it defines a common evolutionary process for the development of the system's safety case. The safety case process determines how the evidence produced in the progression of safety assessment can be structured in order to form an overall convincing argument about the safety of the system. We conclude that it is possible to use this model as the basis of a generic method for the certification of systems across the transportation sector and outline a suitable approach to such certification.     

Novel organic-inorganic glasses

The preparation and properties of novel organic-inorganic glasses with phenyl groups covalently bonded to phosphorus in an inorganic glass are presented. Phenyl phosphonic acid (PPA) can be incorporated into tin and zinc fluorophosphate glasses (MO/MF₂/PO_2.5PPA) at levels up to 72 mol%. The T _g's of these glasses range from below room temperature to near 200°C depending on glass composition. For low melt glasses, these glasses have low moisture absorption and may solubilize dyes, organic photoconductors, NLO molecules, and pharmaceuticals. Several applications have been considered.     

Energy,economic and environmental performance of heating systems in Greek buildings

The introduction of natural gas in the Greek energy market broadened the options in the field of space heating. Residents in five major Greek cities can choose from a variety of different fuels and systems for heating their houses or working spaces; 12 more cities will be connected to the gas network within the next 5 years. Considering that space heating is the major energy consuming activity in the Greek building sector and that the environmental constrains imposed by the Kyoto protocol will be met only with difficulty, if at all, a strategy concerning the developments in space heating seems to be necessary. This however presupposes an elaborate analysis of the overall performance of the alternative systems, taking into consideration the particular conditions of the Greek energy system and the ‘established’ way of designing residential and mixed-use buildings. The present paper aims to present the empirical comparative results related to the three most popular heating systems operated in Greek multi-apartment and mixed-use buildings, which use three different fuels, respectively: a central oil-fired boiler, a unitary gas-fired boiler and unitary heat pumps.