1. Rotating Machinery and Controls Laboratory, Department of Mechanical and Aerospace Engineering, University of Virginia, 122 Engineer’s Way, Charlottesville, VA 22904 e-mail:
2. College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, P.O. Box 93, No. 15 Beisanhuan East Road, Chaoyang District, Beijing 100029, China e-mail:
3. Rotating Machinery and Controls Laboratory, Department of Civil and Environmental Engineering, University of Virginia, 351 McCormick Road, Charlottesville, VA 22904 e-mail: