1. Research and Development Division Japan Polychem Corporation 1 Toho‐cho Yokkaichi Mie 510‐0848 Japan
2. Research and Development Division Japan Polyethylene Corporation 2‐3‐2 Yako, Kawasaki‐ku Kawasaki Kanagawa 210‐8548 Japan
3. Department of Materials Science and Engineering University of Fukui 3‐9‐1 Bunkyo Fukui 910‐8507 Japan