1. Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, Ministry of Education, North China Electric Power University, 102206 Beijing, PR China
2. Department of Mechanical Engineering, Materials and Surface Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
3. GN Hearing A/S, Lautrupbjerg 7, 2750 Ballerup, Denmark
4. Siemens Gamesa Renewable Energy A/S, Borupvej 16, 7330 Brande, Denmark