Supported by the Natural Science Foundation of China(No.10771228);the Natural Science Foundation of Chongqing(No.CSTC,2010BB2090);Education Commission project Research Foundation of Chongqing (No.KJ110617);Chongqing Key Laboratory of Operations Research and System Engineering(No.CSTC, 2006CA8001)
supported by the National Natural Science Foundation of China(10771228);Research grant of Education Committee of Chongqing(KJ090812);Research grant of Chongqing Normal University(08XLQ01)