1. School of Computing and Engineering, University of Huddersfield, Queensgate, Huddersfield, UK. E-mails: S.Batsakis@hud.ac.uk, I.Tachmazidis@hud.ac.uk, G.Antoniou@hud.ac.uk
2. School of Electronic and Computer Engineering, Technical University of Crete (TUC), Chania, Crete, Greece. E-mail: petrakis@intelligence.tuc.gr