MOST [2013CB934000, 2011CB935902, 2014DFG71590, 2010DFA72760, 2011CB711202, 2013AA050903, 2011AA11A257, 2011AA11A254]; China Postdoctoral Science Foundation [2013M530599, 2013M540929]; Tsinghua University Initiative Scientific Research Program [2010THZ08116, 2011THZ08139, 2011THZ01004, 2012THZ08129]; Beijing Municipal Program [YETP0157, Z131100003413002, Z131100003413001]; State Key Laboratory of Automotive Safety and Energy [ZZ2012-011]; Suzhou (Wujiang) Automotive Research Institute [2012WJ-A-01]