1. Dept. of Mech. Engrg., The Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. E-mail: mecthsu@ust.hk (corresponding author).
2. Dept. of Aerosp. and Mech. Engrg., Univ. of Southern California, Los Angeles.
3. Dept. of Mech. Engrg., The Hong Kong Univ. of Science and Technology, Clearwater Bay, Kowloon, Hong Kong.