1. Department of Electrical Engineering, Federal University of Piauí (UFPI), Teresina 64049-550, Brazil
2. Computer Science Department, State University of Londrina (UEL), Londrina 86057-970, Brazil
3. Federal University of Delta do Parnaíba (UFDPar), Parnaíba 64202-020, Brazil
4. COPELABS, Lusófona University, 1749-024 Lisbon, Portugal