1. Department of Imaging System Engineering, Pukyong National University, Busan 608-739, Korea
2. Polymer Chemistry Laboratory, College of Engineering, Kyungil University, Gyeongsangbuk-Do 712-701, Korea
3. Division of Material Engineering, Pukyong National University, Pusan 608-739, Korea
4. Korea Basic Science Institute, Busan Centre, Busan 609-735, Korea