1. Engineering Department, School of Sciences and Technology, University of Trás-os-Montes and Alto Douro (UTAD), Quinta de Prados, 5000-801 Vila Real, Portugal
2. Polytechnic Institute of Coimbra, Coimbra Institute of Engineering, Rua Pedro Nunes-Quinta da Nora, 3030-199 Coimbra, Portugal
3. INESC Coimbra, DEEC, Polo II, 3030-290 Coimbra, Portugal
4. INESC Technology and Science, 4200-465 Porto, Portugal