1. Department of Engineering, University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
2. INESC-TEC UTAD’s Pole, Quinta de Prados, 5000-801 Vila Real, Portugal
3. Department of Mathematics, University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal