Oral history is a branch of history to collect, keep and spread the oral historical data that take oral historical material as its research object.

口述史学是搜集、保存和传播口述史料，以口述历史为研究对象的一门历史学分支学科。

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Type 13 composite piezoelectric material is used as research object, which composed of PZT5H is piezoelectric component and epoxy.

选用13型压电复合材料作为研究对象，压电相为PZT5H，环氧树脂作为基体相。

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This paper takes color matching of reflective and non-reflective material as the research object to explore the relationship in color match contrast ratio of the two materials.

通过对反光膜和卡纸两种材料配色视认度的实验研究，探索出两种材料配色视认度的关系。

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