portfolio model的用法和样例：
例句
- A utility maximization model of the investment portfolio including risk-free asset is put forward, with short sales allowed.
摘要提出了在允许卖空情况下含有无风险资产且借贷利率不同的效用最大化的投资组合模型。 - The results of this research show that the over-reaction appears in most portfolios models, and the performance of each model is quite dissimilar between different capital levels.
实验结果显示，多数投资组合模型存在过度反应，且各种不同模型在不同资金水准下，表现并不相同。
