Acknowledgements:
Iamgreatlyindebttoanumberofpeoplewithoutwhosehelpthisthesiscouldnotbecompleted.FirstofallImustshowmygratitudetomysupervisorProf.导师名whosehelpfulsuggestionshavecontributedgreatlytothecompletionofthisthesis.Iowehimspecialthanksforprovidingmesolidandabundantmaterialsandinstructions.
MysincerethanksshouldgotoMr.(某人)andMiss（某人）fortheirconstantencouragementandsupportthroughoutthecourseoftheresearch.
FinallyIwillexpressmythankstomyfamilywhohaveshownpatienceandunderstandingtotheentireperiodofthiswork.Thebiggestthanksmustgotomyparentswhothoughunabletosupportmetheoreticallyencouragemespiritually.