1. Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
2. DENSO Corporation, 1-1 Showa-cho, Kariya, Aichi 448-8661, Japan
3. Toyota Central R&D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192, Japan