1. Univ. Trás-os-Montes and Alto Douro,Department of Engineering,Vila real,Portugal
2. Univ. Trás-os-Montes and Alto Douro,LIAAD-INESCTEC UTAD Pole,Department of Mathematics,Vila real,Portugal
3. Univ. Trás-os-Montes and Alto Douro,CPES-INESCTEC UTAD Pole,Department of Engineering,Vila real,Portugal