1. Engineering School (DEIM), University of Tuscia, Largo dell’Università, 01100 Viterbo, Italy. cattani@unitus.it
2. Dept. of Physics “E. R. Caianiello”, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy. eguariglia@unisa.it, emanuel.guariglia@mdh.se
3. School of Electronic Science and Engineering, Nanjing University, Nanjing, Jiangsu 210046, China. wangshuihua@njnu.edu.cn