1. MUL2 Group, Department of Mechanical and Aerospace Engineering, Politecnico di Torino Turin, Turin 10129, Italy e-mail:
2. Professor Boeing-Egtvedt Chair William E. Boeing Department of Aeronautics and Astronautics, University of Washington Seattle, Seattle, WA 98195 e-mail:
3. Professor MUL2 Group, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin 10129, Italy e-mail: