1. School of Instrumentation and Optoelectronic Engineering, Beihang University,Beijing,China
2. School of Instrumentation and Optoelectronic Engineering, Research Institute for Frontier Science, Beihang University,Beijing,China
3. National University Hospital,Division of Rehabilitation Medicine,Department of Medicine,Singapore
4. Institute for Infocomm Research, Agency for Science Technology and Research,Singapore
5. School of Computer Science and Engineering, Nanyang Technological University,Singapore