1. Department of Mechanical Science and Bioengineering, Division of Nonlinear Mechanics, Osaka University, 1–3 Machikaneyama‐cho, Toyonaka City, Osaka Prefecture, 560‐8531, Japan
2. Matsushita Electric Industrial Co., Ltd., AV Technology Center, 1–4, Matsuo‐cho, Kadoma City, Osaka Prefecture, 571‐8505, Japan
3. Tribology Research & Development Department, Research & Development Center, Koyo Seiko Co., Ltd. 24–1 Kokubu Higanjo‐cho, Kashiwara City, Osaka Prefecture, 582‐8588, Japan