1. School of Electrical and Computer Engineering; National Technical University of Athens; 9, Heroon Polytechnioy, Zografou; 15773; Athens; Greece
2. Center for Information Services and High Performance Computing; Technische Universität Dresden; Zellescher Weg 12/14; Dresden; 01062; Germany
3. Department of Informatics; Ionian University; 7, Tsirigoti Square; 49100 Corfu; Greece
4. Department of Computer Science; University of Texas at San Antonio; TX 78249; USA