Affiliation: | a Machine Vision Group, Infotech Oulu and Department of Computer Science and Engineering, P. O. Box 4500 FI-90014 University of Oulu, Finlandb Institute of Automation, Chinese Academy of Sciences, P. O. Box 95 Zhongguancun Donglu, Beijing 100080, Chinac Research Center for Learning Science, Southeast University, Nanjing, 210096, China |