1. Researcher, National Research Council, IRPI, Via Madonna Alta 126, 06128 Perugia, Italy (corresponding author).
2. Researcher, National Research Council, IRPI, Via Madonna Alta 126, 06128 Perugia, Italy.
3. Professor, Engineering Dept., Univ. of Ferrara, Via Saragat 1, 44122 Ferrara, Italy.
4. Senior Researcher, National Research Council, IRPI, Via Madonna Alta 126, 06128 Perugia, Italy.