1. Research Fellow, St. Anthony Falls Laboratory, 2 Third Ave. SE, Minneapolis, MN 55414. E-mail: eric0706@umn.edu
2. Joseph T. and Rose S. Ling Professor, Dept. of Civil Engineering, 122 Civil Engineering Building, 500 Pillsbury Dr. SE, Minneapolis, MN 55455.
3. Associate Professor, Dept. of Civil Engineering, Valparaiso Univ., 1900 Chapel Dr., Valparaiso, IN 46383.