从效率的观点看，返流性心脏杂音对应于无用功。
From the viewpoint of efficiency, the energy of cardiac murmur corresponds to useless work.
试验结果表明，在正常组和返流性心脏杂音组间，第一心音能量分数存在显著性差异。
The results showed that the first heart sound energy fraction were significantly different in the normal group and the heart murmur group.
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