primary material是什么意思

用法例句

In this thesis, the concepts of first reason of fault and non exact subfrequencyand non exact multifreqnency (subfrequency hysteresis.

本文首次提出振动故障的一次原因和非准确分、倍频（分频滞后、同频滞后、倍频滞后）振动的概念，对传统的故障原因及特征频率分类方法进行了修正，使二者之对应关系更清晰、简捷。