1. Computer Technology Institute and Press “Diophantus”, 26504 Patras, Greece
2. Computer Engineering and Informatics Department, University of Patras, 26504 Patras, Greece
3. Electrical and Computer Engineering Department, University of Peloponnese, 26504 Patras, Greece
4. Department of Aerospace Science & Technology, National Kapodistrian University of Athens, 15772 Athens, Greece