1. LAQ Aermec Laboratory, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy e-mail:
2. Professor Applied Nonlinear Dynamics and Multi-Scale System Lab, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125 e-mail: