1. Visiting Professor, Dept. of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 Korea, and Faculty of Engineering, Aligarh Muslim Univ., Aligarh 202002, India (corresponding author).
2. Dept. of Civil Engineering, Univ. of Nebraska, Omaha, NE 68182.
3. Dept. of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 Korea.