When a direct sum of lifting modules is lifting is studied here.
研究了提升模的任意直和在什么条件下仍是提升模。
An integral extension construction of domains was also derived by using the semi-direct sum of rings.
同时，还证明了半直和的剩余类环是整环的一个整扩张。
We introduce the notion of topological direct sum, and get a representative theorem of inductive limit by topological direct sum and quotient space.
然后引入拓扑直和的概念，利用它和商空间给出一个归纳极限表示定理。
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