1. a Department of Industrial Engineering , Korea Advanced Institute of Science and Technology , Yusong-gu, Daejon 305-701, Korea
2. b Entrue Consulting Partners , Seoul Finance Center, Taepyungro 1-ga , Chung-gu, Seoul 100-768, Korea
3. c Department of Urban Engineering , Dong-eui University , Pusanjin-gu, Pusan 614-714, Korea