中文摘要：

通过引入偏序模对的定义，给出了在交换环上Morita Context环丁为VNL环的一个充要条件；对Morita Context环为左Quasi—duo环、DS环以及左Quasi—morphic环的性质进行了刻画。

英文摘要：

A sufficient and necessary condition that a Morita context ring T is a VNL ring is given by introducing the definition of the pair of partial modules. The properties that Morita Context rings are left Quasi-duo rings, DS rings and left Quasi-morphic rings are also characterized.