Acknowledgements
The research described in this article received a subvention as a Specified Region Research 428 (Subject Nos 16039211 and 18029013) and was conducted as part of the Ministry of Education, Culture, Sports, Science and Technology's Joint Program the All-Nation Joint Research Institutes. I would like to thank the graduate students of the Engineering Department of Osaka University, Mr Y. Kobayashi (currently at Toyota Motor), Mr K. Matsumoto (currently of Mazda), Mr H. Fukuda (currently of Daihatsu) and S. Hamada for their help with these experiments.