1. Dept. of Polymer and Fiber System Engineering, Chonnam National Univ., Gwangju, 500-757, KR.
2. Faculty of Applied Chemical Engineering, Chonnam National Univ., Gwangju, 500-757, KR.
3. Associate Professor, Dept. of Polymer and Fiber System Engineering, Chonnam National Univ., 300 Yongbong-dong, Puk-gu, Gwangju, 500-757, KR (Corresponding author), e-mail: smkim71@jnu.ac.kr