1. Department of Electrical Engineering; Academic Technology Institute of Central Greece, (ATEI); 3rd km Old National Road, Lamia-Athens Lamia 35100 Greece
2. Department of Computer Engineering; Academic Technological Educational Institute of Central Greece,(ATEI); 3rd km Old National Road, Lamia-Athens Lamia 35100 Greece
3. Department of Mathematics &Informatics; Vienna University of Technology; Karlsplatz 13 1040 Vienna Austria