Harmonic is the most general phenomenon in power system. And harmonic is the main index of power quality.

谐波是目前电力系统中存在的最普遍现象，是电能质量的主要指标。

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Results The sensitivity, specificity and accuracy of diagnosing malignant liver tumors by contrast-enhanced harmonic ultrasonography with low mechanical index were 96%? 90.7%? 93.8% respectively.

结果低机械指数谐波超声造影对恶性病变诊断的的敏感性、特异性和准确性分别为96%、90.7%和93.8%。

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