1. School
of Mechanical Engineering, Yeungnam University, Gyongsan 712-749, South Korea
2. Department
of Chemical Engineering, Indian Institute of Technology, Kanpur 208016, India
3. State
Key Laboratory of Polymer Physics and Chemistry, Changchun Institute
of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China
4. Department
of Physics, Jilin University, Changchun 130012, P. R. China