[1] Univ Delaware, Dept Phys & Astron, Bartol Res Inst, Newark, DE 19716 USA
[2] South Univ Sci & Technol China, Dept Mech & Aerosp Engn, Shenzhen 518055, Guangdong, Peoples R China
[3] Queens Univ Belfast, Sch Math & Phys, Belfast BT7 1NN, Antrim, North Ireland
[4] Univ Calabria, Dipartimento Fis, Cosenza, Italy