1. Computer Science and Artificial Intelligence Lab; Massachusetts Institute of Technology; 32 Vassar St Cambridge Massachusetts 02139 USA
2. Mechanical Engineering; Cornell University; 124 Hoy Rd Ithaca New York 14850 USA
3. Penn State University; 263 Materials Research Lab University Park PA 16802 USA
4. Mechanical Engineering; Columbia University; 535E S.W. Mudd New York New York 10027 USA