1. State Grid Tianjin Electric Power Research Institute, Tianjin 300392, China
2. School of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, China
3. Tianjin Eco-Environmental Monitoring Center, Tianjin 300191, China
4. Key Laboratory of Micro Opto-Electro Mechanical System Technology, Tianjin University, Tianjin 300072, China