His research interests are machine learning and artificial intelligence (especially for deep learning and online learning), and their applications to tackle challenges of real-world big data challenges across varied domains, including computer vision and pattern recognition, multimedia retrieval, social media, web search and mining, bioinformatics, and computational finance. He has published over 200 high-quality referred journal and conference papers in his areas. He has contributed extensively in academic communities. He has served as the Editor-in-Chief (EiC) of Neurocomputing, General Co-chair for ACM SIGMM Workshops on Social Media (WSM'09-11), Program Co-Chair for Asian Conference on Machine Learning (ACML'12), Book editor for "Social Media Modeling and Computing", Guest editor for Machine Learning and ACM TIST journals, Associate Editor (AE) for several reputable journals including IEEE Trans. Pattern Anal. Mach. Intell. (TPAMI), Area Chair/Senior PC/TPC for many conferences. He has been often invited for external grant review by worldwide funding agencies, including USA NSF agency, Hong Kong RGC agency, etc.