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Iliopoulos A.C.,Democritus University of Thrace | Pavlos G.P.,Democritus University of Thrace | Papadimitriou E.E.,Aristotle University of Thessaloniki | Sfiris D.S.,Democritus University of Thrace | And 2 more authors.
International Journal of Bifurcation and Chaos | Year: 2012

Strong evidence is provided for significant far from equilibrium complex processes in the seismogenic layer of the North Aegean region (Greece), after applying modern nonlinear methods to various seismicity time series. The data used are subsets of the regional catalogue compiled in the central Seismological Station of Geophysics Department, Aristotle University of Thessaloniki and concern 4367 earthquakes of magnitude greater than 3.8, which took place during the period of 19682008. We present results, derived from the application of nonlinear algorithms, concerning the estimation of correlation dimension, mutual information, largest Lyapunov exponent, flatness coefficient and q-value which correspond to Tsallis nonextensive statistics. These quantities are estimated for two seismic time series corresponding to the basic focal parameters of earthquakes, namely origin time and magnitude. The obtained results can be associated with novel far from equilibrium complex dynamics such as low dimensional chaos, Self Organized Criticality (SOC) and intermittent turbulence. Furthermore, in this study, new information is provided about the nonlinear turbulent character of the Hellenic lithospheric dynamics related to the Tsallis nonextensive statistical theory. Our analysis indicates the coexistence of two different lithospheric processes, one low dimensional (chaotic) and the other high dimensional (SOC), revealing the strongly turbulent character of the Greek lithospheric system. In particular, the low dimensional chaotic process corresponds to the temporal manifestation of earthquakes, whereas the high dimensional nonlinear (SOC) process corresponds to the burst energy releases, a result that has significant implications concerning the ability of earthquake prediction. © 2012 World Scientific Publishing Company. Source

Pavlos G.P.,Democritus University of Thrace | Iliopoulos A.C.,Democritus University of Thrace | Athanasiou M.A.,Technical University of Serres | Karakatsanis L.P.,Democritus University of Thrace | And 11 more authors.
AIP Conference Proceedings | Year: 2010

Several contributions of the Thrace group to magnetospheric, solar, and planetary physics over the last three decades are summarized from the perspective of a paradigm shift in nonlinear plasma physics. The work by Dennis Papadopoulos on plasma instabilities has been a source of inspiration for our magnetospheric studies including the introduction of the chaos hypothesis. © 2010 American Institute of Physics. Source

Anthymidis K.G.,Applied Materials | David C.,Technical University of Serres | Tsipas D.N.,Aristotle University of Thessaloniki
Materials and Manufacturing Processes | Year: 2011

The impact testing is an efficient experimental method that enables the quantitative and qualitative evaluation of the fatigue resistance of mono- and multilayer coatings deposited on various substrates, which was not possible with the common testing methods previously available. In this article the experimental assessment of the fatigue resistance of aluminide slurry coatings working under cyclic loading conditions by means of the dynamic impact testing method is presented. The fatigue failure mode, such cohesive or adhesive, of the investigated coatings is determined using scanning electron and optical microscopy, as well as Energy Dispersive X-ray (EDX) analysis. Critical values of impact load responsible for distinctive fatigue failure modes of the coating substrate system are obtained. © Taylor & Francis Group, LLC. Source

Anthymidis K.G.,Technical University of Serres | David C.,Technical University of Serres | Trakali A.,National Technical University of Athens | Tsipas D.N.,Aristotle University of Thessaloniki
Key Engineering Materials | Year: 2012

Chromium coatings have been used for the protection of gas turbine blades in power plants during the last years due to their very good resistance against steam corrosion. Microhardness, scratch, adhesion and pin-on-disk sliding tests are commonly used for rapid evaluation of the mechanical properties of these coatings [1,2]. However, very limited information exists on their fatigue resistance. In this paper we present the experimental results of the impact testing examination of the above coatings. This experimental method is capable to assess the fatigue and the impact wear resistance of coatings working under cyclic impact loading conditions. From the experimental results it was concluded that the slurry Cr, Zr coatings deposited on P91 steel showed adequate fatigue strength for the above-mentioned kind of use. © (2012) Trans Tech Publications. Source

Agrianidis P.,Technical University of Serres | Agrianidis T.,Technical University of Serres | Anthymidis K.,Technical University of Serres | Trakali A.,National Technical University of Athens
Key Engineering Materials | Year: 2010

Aluminum matrix composites reinforced by ceramic particles are well know for their good thermophysical and mechanical properties. As a result, during the last years, there has been a considerable interest in using aluminum metal matrix composites (MMCs) in the automobile industry. These potential applications have greatly stimulated the tribological studies of MMCs under different operating conditions. In this paper, TiB - particles - reinforced aluminum - tungsten matrix composites ere fabricated by the cost - effective squeeze - casting technology and their microstructure characteristics and mechanical properties were investigated. The microstructure observation showed that the produced composites were dense, with no micro-holes and obvious defects. Their wear resistance was evaluated using a pin on disc type equipment under dry wear conditions and found significantly increased compared to pure Al metal. © (2010) Trans Tech Publications, Switzerland. Source

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