1. a Department of Industrial Engineering and Logistics Management , Hong Kong University of Science and Technology , Hong Kong, PRC
2. b Department of Computer Science and Engineering , Hong Kong University of Science and Technology , Hong Kong, PRC
3. c Institut für Kommunikationsakustik, Ruhr-Universität Bochum , Bochum, Germany
4. d Rehabilitation Engineering Center, Hong Kong Polytechnic University , Hong Kong, PRC