The noise of the fan is mainly consist of circumrotatory noise and backset noise based on the theoretical analysis.

首先基于风机噪声理论的分析确定了影响风机噪声源的主要因素是旋转噪声和涡流噪声。

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The backset current extraction, ultrasonic-assisted extraction and microwave extraction were tested to select the optimum extraction and the quantitative analysis of specimen was made.

分别考察回流法提取法、超声波萃取法及微波萃取法。选择最优提取工艺，对样品进行含量测定。

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