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Psachná, Greece

Ktena A.,TEI of Sterea Ellada
Physica B: Condensed Matter | Year: 2016

Residual stresses in magnetic materials, whether the result of processing or intentional loading, leave their footprint on macroscopic data, such hysteresis loops and differential permeability measurements. A Preisach-type vector model is used to reproduce the phenomenology observed based on assumptions deduced from the data: internal stresses lead to smaller and misaligned grains, hence increased domain wall pinning and angular dispersion of local easy axes, favouring rotation as a magnetization reversal mechanism; misaligned grains contribute to magnetostatic fields opposing the direction of the applied field. The model is using a vector operator which accounts for both reversible and irreversible processes; the Preisach concept for interactions for the role of stress related demagnetizing fields; and a characteristic probability density function which is constructed as a weighed sum of constituent functions: the material is modeled as consisting of various subsystems, e.g. reversal mechanisms or areas subject to strong/weak long range interactions and each subsystem is represented by a constituent probability density function. Our assumptions are validated since the model reproduces the hysteresis loops and differential permeability curves observed experimentally and calculations involving rotating inputs at various residual stress levels are consistent and in agreement with experimental evidence. © 2016 Elsevier B.V.

Fotiadis G.,TEI of Sterea Ellada | Vrahnakis M.,T.E.I. of Thessaly | Kazoglou Y.,Municipality of Prespa | Tsiripidis I.,Aristotle University of Thessaloniki
Hacquetia | Year: 2014

A recently completed project on the Natura 2000 sites of Prespa National Park revealed that the area hosts 49 habitat types according to the EU classification, of which eight have a narrowly restricted distribution in Greece. The priority habitat type "6260 Pannonic sand steppes" is reported here for the first time for Greece. The new locality represents its southernmost occurrence on the Balkan Peninsula. The aim of this paper therefore is to describe the Greek stands of this habitat type, investigate the factors affecting its occurrence and discuss the associated conservation issues. This is based on a total of 87 releves sampled for this study and 8 additional releves from the literature. The releves were classified by applying TWINSPAN and ordinated using Detrended Correspondence Analysis (DCA). Six vegetation units could be distinguished. One of these corresponds to the habitat type 6260 and was found exclusively on inland sand dunes. Syntaxonomically, we assigned this unit to the alliance Sileno conicae-Cerastion semidecandri s.l. of the class Koelerio-Corynephoretea. Its occurrence in the study area seems to be determined by climatic factors, as well as by the sandy substrate, while anthropogenic disturbances such as grazing also appear to be beneficial to some degree. Apart from the Koelerio-Corynephoretea, another five grassland classes were distinguished in the national park, namely the Thero-Brachypodietea, Stellarietea mediae, Festuco-Brometea, Daphno-Festucetea and Juncetea trifidi.

Papaefstathiou I.,Synelixis Solutions Ltd | Chrysos G.,Technical University of Crete | Sarakis L.,TEI of Sterea Ellada
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

This paper present a recently started multi-national project which will provide an innovative comprehensible, ultra-Fast, security-Aware CPS Simulator (called COSSIM) that will seamlessly simulate both the networking and the processing parts of the Cyber Physical Systems (CPS) significantly faster and more accurate than any existing solution. In order to achieve that COSSIM will develop a novel simulator framework based on a processing simulation subsystem (i.e. a “full-system simulator”) which will be integrated with a novel network simulator. Furthermore, innovative power consumption and security measurement models will be developed and incorporated to the end framework. On top of that, COSSIM will also address another critical aspect of an accurate CPS simulation environment: the performance as measured in required simulation time. COSSIM will create a framework that is orders of magnitude faster, while also being more accurate and reporting more CPS aspects, than existing solutions, by applying hardware acceleration through the use of field programmable gate arrays (FPGAs), which have been proven extremely efficient in relevant tasks. This paper presents the high-level architecture of the end-system as well the most innovative aspects of it that will allow it to be the fastest and most accurate such simulator, while it does not cover the security aspects of this novel system. © Springer International Publishing Switzerland 2015.

Ktena A.,TEI of Sterea Ellada | Hristoforou E.,National Technical University of Athens | Gerhardt G.J.L.,University of Caxias do Sul | Missell F.P.,University of Caxias do Sul | And 3 more authors.
Physica B: Condensed Matter | Year: 2014

Magnetic Barkhausen noise (mBN) is known to be related to magnetization reversal mechanisms and the underlying microstructure in magnetic materials. However, the quantitative evaluation of the material properties is hindered by the stochastic nature of the method combined with the lack of standardization. In this paper, the results of interlaboratory tests on the same series of samples are presented. Electrical steel samples have been prepared with controlled grain size (11-148 μm) and strain (0-29%) and have been characterized using the mBN technique as developed in three different laboratories. In spite of the different methodologies used, mBN is found to increase with strain and decrease with decreasing grain size, in all cases. Of special interest is the variation of the double-peaked BN envelope with the grain size, with one peak occurring in positive and the other in negative fields. The significance of the methodology used in the correct interpretation of the results for a given material is discussed. © 2013 Elsevier B.V.

Vrahnakis M.,T.E.I. of Thessaly | Fotiadis G.,TEI of Sterea Ellada
Journal of Environmental Protection and Ecology | Year: 2015

The endemic Prespa trout (Salmo peristericus Karaman 1938) is a flagship species for the Prespa National Park. The aim of the research was to present environmental impacts of works done to improve a forest road (in January-February 2010) on the trout habitats in the Siroka stream which flows parallel to the road. The assessment was based on the use of the QBR (Qualitat del Bosc de Ribera) and RMP (Riparian Macrophyte Protocol) protocols. Results are presented in a comparative manner since the same protocols were used five months before the road improvement (September 2009). It was found that the irrational widening of the road and the volume of excavated soils deposited within the riparian zone, especially in the sampling stations, led to significant deterioration of the abiotic characteristics of the stream and the habitat quality of the Prespa trout.

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