portfolio model的用法和樣例：
例句
- A utility maximization model of the investment portfolio including risk-free asset is put forward, with short sales allowed.
摘要提出了在允許賣空情況下含有無風險資產且借貸利率不同的效用最大化的投資組合模型。 - 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.
實驗結果顯示，多數投資組合模型存在過度反應，且各種不同模型在不同資金水準下，表現並不相同。
