1. H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA 30332 e-mail:
2. Mem. ASME Grado Department of Industrial and Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 e-mail:
3. The Boeing Company, 900 N Sepulveda Blvd, El Segundo, CA 90245 e-mail:
4. Fellow ASME H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, GA 30332 e-mail: