1. Department of Mechanical Engineering and Institute for Systems Research, University of Maryland, College Park, MD 20742
2. Department of Mechanical Engineering and Institute for Systems Research, University of Maryland, College Park, MD 20742; Precision Engineering Division, Manufacturing Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899
3. Precision Engineering Division, Manufacturing Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899