1. Associate Professor, Dipartimento di Scienze Agrarie e Forestali, Università degli Studi di Palermo, viale delle Scienze edificio 4, 90128 Palermo, Italy (corresponding author).
2. Professor, Dept. of Biological and Agricultural Engineering and Zachry Dept. of Civil Engineering, Texas A&M Univ., 321 Scoates Hall, 2117 TAMU, College Station, TX 77843-2117.