**6. Acknowledgments**

This work was developed within the Advanced Mechanics Laboratory (MechLav) of Ferrara Technopole and brought into being with a contribution by the Emilia-Romagna Region – Assessorato Attivita' Produttive, Sviluppo Economico, Piano telematico - POR-FESR 2007- 2013, Attività I.1.1.
