The investigators hypothesis is that an antipsychotic drug combination of low-dose olanzapine plus low-dose trifluoperazine is similar to regular-dose olanzapine monotherapy in efficacy and safety for treatment of schizophrenia.The goal of this study is to compare the efficacy and safety of the olanzapine (10 mg/d) and olanzapine (5 mg/d) plus trifluoperazine (5 mg/d) in the treatment of acute psychotic exacerbations of schizophrenia.