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Filippou A.,University of Portsmouth | Karras D.A.,Chalkis Institute of Technology | Papazoglou P.M.,Lamia Institute of Technology | Papademetriou R.C.,University of Portsmouth
Communications in Computer and Information Science | Year: 2010

Coverage is one of the fundamental metrics used to quantify the quality of service (QoS) of sensor networks. In general, we use this term to measure the ability of the network to observe and react to the phenomena taking place in the area of interest of the network. In addition, coverage is associated with connectivity and energy consumption, both important aspects in the design process of a Wireless Sensor Network (WSN). On the other hand, simulating a WSN involves taking into account different software and hardware aspects. In this paper we attempt to present a simulation framework suitable for integrating coverage mechanisms in WSN emulation using a layered architecture and a fitting scheduling model. The suggested model is derived after a critical overview and presentation of the coverage strategies as well as the simulation approaches for WSN developed so far. The main advantage of the proposed framework is its capability to handle concurrent events occurring at WSN deployment and operation through the suitable layered scheduler integrated. © 2010 Springer-Verlag. Source

Papazoglou P.M.,Lamia Institute of Technology | Papazoglou P.M.,University of Portsmouth | Karras D.A.,Chalkis Institute of Technology | Papademetriou R.C.,University of Portsmouth
Telecommunication Systems | Year: 2013

The goal of this paper is to investigate the application of the Multi Agent technology in modeling and simulating large scale wireless communication systems. There are very few studies using the multi agent concept as an alternative approach for designing and simulating resource allocation in cellular systems and especially in large scale ones. Thus, a novel modeling methodology of wireless network services exploiting multi agent technology and investigating in depth critical agent issues is proposed in this paper. It is shown that the multi agent concept proves to be a suitable solution for modeling and implementing cellular network services simulation even in the case of large scale wireless networks. The whole investigation is divided in two phases: (a) multi agent modeling analysis and (b) multi agent model development for controlling network performance. Simulation results show the effectiveness of the proposed multi agent model when is applied in combination with the state of the art event scheduling mechanism. © 2011 Springer Science+Business Media, LLC. Source

Papazoglou P.M.,Lamia Institute of Technology | Papazoglou P.M.,University of Portsmouth | Karras D.A.,Chalkis Institute of Technology | Papademetriou R.C.,University of Portsmouth
1st International Conference on Future Generation Communication Technologies, FGCT 2012 | Year: 2012

The increasing number of cellular users and the demand for broadband mobile communications (3rd and 4th generation) raises the problem of bandwidth availability and the associated channel allocation strategies. Moreover, Quality of Service (QoS) is the challenge for such modern wireless multimedia telecommunications. This paper presents new algorithms for efficient bandwidth management of GSM cellular multimedia systems. Besides, it proposes a comprehensive simulation system for evaluating channel assignment schemes in QoS multimedia cellular systems incorporating their principles, entities and concepts involved. The proposed system is implemented in Java, in order to create an educational generic simulation environment with the future capability of internetworking. The system is designed with the goal to be efficient in simulating large scale generic cellular multimedia telecommunication systems. © 2012 IEEE. Source

Ganatsas P.,Aristotle University of Thessaloniki | Spanos I.,Greek National Agricultural Research Foundation | Tsakaldimi M.,Aristotle University of Thessaloniki | Goudelis G.,Lamia Institute of Technology
Notulae Botanicae Horti Agrobotanici Cluj-Napoca | Year: 2012

Nine years after a wildfire, above- and below-ground morphology of Pinus brutia Ten. saplings and the microsite factors prevailing in understorey (unburned area) and postfire conditions (burned area) of the Forest Park of Thessaloniki were studied. Major stand characteristics (density, tree canopy cover, tree height, crown height, and diameter) were measured in the unburned area. Light and soil conditions as well as plant cover of woody species were recorded in both areas (burned and unburned). A random sample of pine saplings, of uniform age, was taken from both burned and unburned areas, and their above-ground (height, diameter, number and total length of branches, needle biomass) and below-ground morphological characteristics (taproot length, total length of coarse and fine roots, and number of coarse roots) were measured. Data analysis showed that above- and below-ground morphology of pine saplings was adversely affected in saplings grown in understorey conditions, compared to those grown in postfire conditions. P. brutia is a shade-intolerant tree species and thus the light conditions seem to be the critical factor affecting the growth of pine saplings. Light is not a limiting factor in the burned area compared to the understorey, where density of the tree canopy limits available light. Source

Avramopoulos A.,National Hellenic Research Foundation | Avramopoulos A.,Lamia Institute of Technology | Serrano-Andres L.,University of Valencia | Li J.,Accelrys Inc. | Papadopoulos M.G.,National Hellenic Research Foundation
Journal of Chemical Theory and Computation | Year: 2010

The electronic ground state of H-Ng-Ng-F (Ng = Ar, Kr, Xe) has been studied theoretically by employing the ab initio complete active space valence bond (CASVB) and multi-state complete active space perturbation theory (MS-CASPT2) methods. Both levels of theory confirm the diradicaloid character (DC) of the HNg2F ground state, increasing in the order Ar > Kr > Xe. The very significant effect of the first and, even more, the second Xe atom on the (hyper)polarizabilities has been shown and interpreted. Thus, the present results demonstrate a mechanism for producing very large (hyper) polarizabilities. © 2010 American Chemical Society. Source

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