This article introduces the reason, course and characteristic of the new chemicals policy of European Union (REACH) and the echo on it from various fields; and sets forth the opinions and advices.
介绍了欧盟化学品新政策(REACH)的来由、历程、特征及来自不同方面的反响，并提出了意见及建议。
The peak time detecting circuit which is composed of full-wave rectification circuit and differential circuit can detect the reach time of echo signal accurately.
采用时间增益补偿技术，补偿超声波在空气中的衰减，减少回波信号的起伏；由有源全波整流电路和微分电路等组成峰值时间检测电路，可正确检测回波的峰值到达时间。
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