1. Assistant Professor Department of Mechanical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Road, Taipei 10627, Taiwan, R.O.C. e-mail:
2. General Manager Luren Precision Co., Ltd., No. 1-1, Li Hsin 1st Road, Hsinchu Science Park, Hsinchu 30078, Taiwan, R.O.C.