1. M.Sc. Student, Dept. of Aerospace, Univ. Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia (corresponding author).
2. Associate Professor, Dept. of Aerospace, Univ. Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
3. Associate Professor, Dept. of Mechanical and Manufacturing Engineering, Univ. Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.