1. Department of Mechanical and Aerospace Engineering, Polytechnic University of Turin, C.so Duca degli Abruzzi 24, Turin 10129, Italy
2. Department of Electronic and Information Engineering, University of Perugia, Via G. Duranti 93, Perugia 06125, Italy
3. Department of Mechanical and Aerospace Engineering, West Virginia University Morgantown, P.O. Box 6106, Morgantown, WV 26506, USA