1. Department of Industrial and Information Engineering and Economics, University of L’Aquila, via G. Gronchi 18, I-67100 L’Aquila, Italy
2. Department of Physical and Chemical Sciences, University of L’Aquila, via Vetoio, 67100 L’Aquila, Italy
3. CNR-IMM Istituto per la Microelettronica e Microsistemi, VIII strada 5, I-95121 Catania, Italy
4. Solvay Novecare, 93308 Auberviliers, France