1. Department of Mechanical Engineering, University of Maryland, College Park, MD 20742 e-mail:
2. Department of Aerospace & Mechanical Engineering, University of Southern California, Los Angeles, CA 90089 e-mail:
3. Department of Mechanical & Aerospace Engineering, Old Dominion University, Norfolk, VA 23529 e-mail:
4. Intelligent Systems Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 e-mail: