1. Professor, Dept. of Agricultural and Biological Engr., 220 Agricultural Engr. Building, Penn State Univ., Univ., Park, PA 16802-1909 (corresponding author).
2. Postdoctoral Researcher, Dept. of Agricultural and Biological Engr., 105 Agricultural Engr. Building, Penn State Univ., Univ. Park, PA 16802-1909.