1. Department of Mechanical Engineering, Virginia Military Institute, Lexington, VA 24450 e-mail:
2. Department of Industrial and Information Engineering and Economics, University of L'Aquila, Via G. Gronchi n. 18, L'Aquila 67100, Italy e-mail:
3. Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824 e-mail:
4. Sandia National Laboratories, Albuquerque, NM 87110 e-mail: