1. a Manufacturing Coordination Division , NEC Corporation , 7-1 Shiba 5-Chome, Minato-ku, Tokyo, 108-01, Japan
2. b Industrial Engineering Department , Tokyo Institute of Technology , 12-1, Ookayama 2-Chome, Meguro-ku, Tokyo, 152, Japan
3. c Department of Management , Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong