1. Department of Mechanical Engineering, Nagaoka University of Technology, Graduate School of Engineering, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan e-mail:
2. Department of Mechanical Engineering, Graduate School of Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan
3. Lubricants Research Laboratory, Idemitsu Kosan Co., Ltd., 24-4 Anesakikaigan, Ichihara, Chiba 299-0107, Japan
4. LG Technology Department, Linear Technology Center, NSK Ltd., 12 Kirihara, Fujisawa, Kanagawa 252-0811, Japan