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Papadakis H.,Technological Educational Institute of Crete | Fragopoulou P.,Institute of Research and Technology | Markatos E.P.,Institute of Research and Technology | Roussopoulos M.,National and Kapodistrian University of Athens
IEEE Transactions on Parallel and Distributed Systems | Year: 2013

One of the most appealing characteristics of unstructured P2P overlays is their enhanced self-* properties, which results from their loose, random structure. In addition, most of the algorithms which make searching in unstructured P2P systems scalable, such as dynamic querying and 1-hop replication, rely on the random nature of the overlay to function efficiently. The underlying communications network (i.e., the Internet), however, is not as randomly constructed. This leads to a mismatch between the distance of two peers on the overlay and the hosts they reside on at the IP layer, which in turn leads to its misuse. The crux of the problem arises from the fact that any effort to provide a better match between the overlay and the IP layer will inevitably lead to a reduction in the random structure of the P2P overlay, with many adverse results. With this in mind, we propose ITA, an algorithm which creates a random overlay of randomly connected neighborhoods providing topology awareness to P2P systems, while at the same time has no negative effect on the self-* properties or the operation of the other P2P algorithms. Using extensive simulations, both at the IP router level and autonomous system level, we show that ITA reduces communication latencies by as much as 50 percent. Furthermore, it not only reduces by 20 percent the number of IP network messages which is critical for ISPs carrying the burden of transporting P2P traffic, but also distributes the traffic load more evenly on the routers of the IP network layer. © 1990-2012 IEEE.


Rapti E.,Institute of Research and Technology | Karageorgos A.,T.E.I. of Thessaly | Ntalos G.,T.E.I. of Thessaly
Proceedings of the Workshop on Enabling Technologies: Infrastructure for Collaborative Enterprises, WETICE | Year: 2014

Product bundling refers to the combination of several products for sale as one product. Current bundling approaches lack the ability to adapt, focusing mostly on the creation of pre-computed static bundles, which prove to be inefficient considering the dynamically changing prospective customer needs and product availability, as is particularly the case in enterprise networks. This paper describes a novel approach for dynamic generation of personalized, constrained and rule-based product bundles in such environments. The proposed agent-based approach involves estimation of substitution and complementarity associations between products and constructing bundles according to individual customer preferences. The process adapts automatically to changing circumstances, such as customer profile, product availability and constraint and rule diversity. The proposed approach is discussed in the context of e-Furniture, an agent-based system supporting networking of furniture and wood product manufacturing enterprises. © 2014 IEEE.


Rapti E.,Institute of Research and Technology | Karageorgos A.,Technological Educational Institute of Larissa | Gerogiannis V.C.,Technological Educational Institute of Larissa
Procedia Computer Science | Year: 2015

Traditional service composition approaches rely mostly on centralised architectures, which have been proven inadequate in pervasive Internet of Things (IoT) environments. In such settings, where decentralisation of decision-making is mandatory, nature-inspired computing paradigms have emerged due to their inherent capability to accommodate spatiality, self-adaptivity, and evolvability. In this paper, taking inspiration from natural metaphors we propose a decentralised service composition model which is based on artificial potential fields. In the proposed approach, artificial potential fields (APFs) lead the service composition process through the balance of forces applied between service requests and service nodes. APFs are formed considering the percentage of user requested services that can be offered by service provision nodes, as well as service node availability. ?he applicability of the proposed approach is discussed in an exemplar scenario concerning dynamic and personalised composition of an audio-visual virtual guide service in an IoT network of a trade show venue. © 2015 The Authors. Published by Elsevier B.V.


Biatek T.,Institute of Research and Technology | Hamidouche W.,INSA Rennes | Travers J.-F.,Directorate General of Armaments | Deforges O.,INSA Rennes
IEEE Transactions on Broadcasting | Year: 2016

Ultra high definition (UHD) is the latest trend in broadcasting area, which enables new services with 3840×2160 resolution and comes with enhanced color-gamut, frame-rate, dynamic range, and better audio system compared to the currently deployed HD services. The UHD format for broadcasting is already under standardization in the digital video broadcasting consortium which plans to introduce UHD services in three phases. The increase in data brought by these services requires more efficient compression and transmission systems. The recent scalable video coding standard scalable High Efficiency Video Coding (SHVC) is a promising candidate to handle these three phases while ensuring backward compatibility. Moreover, delivering such contents over networks needs an accurate control of the output bitrate from encoder engines to match rigid constraints on bandwidth and QoS. Several contributions have already been proposed to jointly encode scalable stream, but without considering the impact of bitrate ratio between layers on the compression performance. In this paper, the impact of the bitrate ratio between layers on the coding performance is first investigated for several UHD scalable schemes including spatial, color-gamut, and SDR-to-HDR scalability in SHVC. Based on this investigation, an adaptive rate control algorithm which dynamically allocates the bitrate between two layers is proposed to optimize the performance under quality and bitrate constraints. The algorithm has been implemented in the SHVC reference software (SHM9.0) and tested over 15 video sequences under two industrial use-cases. The performance shows an average BD-BR improvement of 7.51% and 3.35% for these two use-cases. © 2016 IEEE.


Liaskos C.,Institute of Research and Technology | Mavropoulos A.,Institute of Research and Technology | Orfanidou T.,Institute of Research and Technology | Spyrou V.,Technological Educational Institute of Larissa | And 2 more authors.
Autoimmunity Highlights | Year: 2012

Autoimmune hepatitis (AIH) is not a disease entity restricted to man, but it can be found in other animals including canines. An increasing number of studies have focused on the immunopathogenesis of human autoimmune hepatitis (hAIH), but little is known of what triggers canine autoimmune hepatitis (cAIH). Several drugs, toxins, microbial and viral agents are able to induce autoantibodies and indeed immune-mediated chronic canine hepatitis with immunological and serological features similar of those seen in the human disease. We discuss the features of cAIH paying attention to the autoantibody profile of the disease in comparison to that seen in hAIH. We also discuss the immunomodulatory role of specific molecular signaling pathways such as those mediated by tumor growth factor and p38 mitogen-activated kinase in the induction of AIH, and the potential of these molecules to act as targets of specialized immunotherapeutic interventions. Review of the literature indicates that we have more to learn for the delineation of autoantibody profile and the antigen-specific immunoregulatory mechanisms involved in the pathogenesis of cAIH from the human disease, rather than the other way around. © 2012 Springer-Verlag Italia.


PubMed | University of Thessaly, Technological Educational Institute of Larissa and Institute of Research and Technology
Type: Journal Article | Journal: Auto- immunity highlights | Year: 2015

Autoimmune hepatitis (AIH) is not a disease entity restricted to man, but it can be found in other animals including canines. An increasing number of studies have focused on the immunopathogenesis of human autoimmune hepatitis (hAIH), but little is known of what triggers canine autoimmune hepatitis (cAIH). Several drugs, toxins, microbial and viral agents are able to induce autoantibodies and indeed immune-mediated chronic canine hepatitis with immunological and serological features similar of those seen in the human disease. We discuss the features of cAIH paying attention to the autoantibody profile of the disease in comparison to that seen in hAIH. We also discuss the immunomodulatory role of specific molecular signaling pathways such as those mediated by tumor growth factor and p38 mitogen-activated kinase in the induction of AIH, and the potential of these molecules to act as targets of specialized immunotherapeutic interventions. Review of the literature indicates that we have more to learn for the delineation of autoantibody profile and the antigen-specific immunoregulatory mechanisms involved in the pathogenesis of cAIH from the human disease, rather than the other way around.

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