1. Ph.D. Student, Dept. of Agricultural and Forest Sciences, Università di Palermo, Viale delle Scienze 12, 90128 Palermo, Italy.
2. Professor, Dept. of Agricultural and Forest Sciences, Università di Palermo, Viale delle Scienze 12, 90128 Palermo, Italy.
3. Professor, Dept. of Agricultural and Forest Engineering, Univ. of Lleida, Alcalde Rovira Roure 191, 25198 Lleida, Spain (corresponding author).
4. Professor, Dept. of Agricultural and Forest Engineering, Univ. of Lleida, Alcalde Rovira Roure 191, 25198 Lleida, Spain.
5. Emeritus Professor, Dept. of Agricultural and Forest Engineering, Univ. of Lleida, Alcalde Rovira Roure 191, 25198 Lleida, Spain.