1. Department of Electrical Engineering, Institute of Engineering of Coimbra Rua Pedro Nunes, 3031-601 Coimbra, Portugal
2. Department of Electrical Engineering, Institute of Engineering of Porto Rua Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal
3. Budapest Tech, John von Neumann, Faculty of Informatics, Inst. of Intelligent Engineering Systems Bécsi út 96/B, H-1034, Budapest, Hungary