1. Research Assistant Professor, Earthworks Engineering Research Center, Dept. of Civil, Construction, and Environmental Engineering, Iowa State Univ. of Science and Technology, 2711 South Loop Dr., Suite 4700, Ames, IA 50010-8664 (corresponding author).
2. Associate Professor of Civil Engineering and Director of Earthworks Engineering Research Center, Dept. of Civil Construction and Environmental Engineering, Iowa State Univ. of Science and Technology, 476 Town Engineering, Ames, IA 50011-3232.
3. Professor, Dept. of Statistics, Iowa State Univ. of Science and Technology, 304B Snedecor, Ames, IA 50011-3232.