1. Department of Psychological Sciences, U-1020, University of Connecticut, Storrs, CT 06269-1020, USA
2. Department of Mechanical Engineering, University of Maryland, College Park, MD 20742-3035, USA
3. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 W. Green St. MC 244, Urbana, IL 61801, USA