1. Department of Industrial Engineering; University of Salerno; Via Giovanni Paolo II Fisciano (SA) 84084 Italy
2. Department of Physics “E.R. Caianiello”; University of Salerno; Via Giovanni Paolo II Fisciano (SA) 84084 Italy
3. Department of Chemical Materials Environmental Engineering; University of Rome “La Sapienza”; Via Eudossiana 18 Roma 00184 Italy