1. Department of Industrial and Systems Engineering, Lehigh University, Bethlehem, Pennsylvania 18015;
2. School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30313;
3. Department of Industrial Engineering and Management Sciences, Northwestern University, Evanston, Illinois 60208;
4. Department of Electrical and Computer Engineering, Department of Industrial Engineering and Management Sciences, Northwestern University, Evanston, Illinois 60208;
5. Department of Mathematics, University of California–San Diego, La Jolla, California 92093