1. Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University di Messina, I-98166 Messina, Italy
2. Institute of Applied and Computational Mathematics, FORTH, GR-70013 Heraklion, Crete, Greece
3. Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
4. Department of Engineering, University of Messina, I-98166 Messina, Italy
5. Department of Electrical and Information Engineering, Polytechnic of Bari, I-70125 Bari, Italy
6. Key Laboratory of Multifunctional Nanomaterials and Smart Systems, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Ruoshui Road 398, Suzhou 215123, People's Republic of China