1. Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890; School of Engineering, University of Pittsburgh, 323 Benedum Hall, Pittsburgh, PA 15260
2. Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213-3890
3. School of Engineering, University of Pittsburgh, 323 Benedum Hall, Pittsburgh, PA 15260