1. Department of Mechanical Engineering, Temple University, Philadelphia, PA 19122 e-mail:
2. Department of Mechanical Engineering, Howard University, Washington, DC 20059 e-mail:
3. Department of Mechanical Engineering, University of Maryland, College Park, MD 20742 e-mail:
4. Office of Weights and Measures, National Institute of Standards and Technology, Gaithersburg, MD 20899 e-mail: