Percussive maintenance happens when your piece of electronic device — television, computer, etc — won't work, you give it a sharp unscientific whack to revive it. And it often works.

电视或电脑等电子设备出故障的时候，你有时会通过敲打的方式让其恢复运转。而且这种方式通常都会管用。

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It is a risky, smash-mouth approach, but it often works.

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Both sides are encouraged down this path by the fact that, while voters say they don't like negative campaigning, polls show it often works, said Andrew Kohut, president of the Pew Research Center.

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That is a very simple model, but it works often enough to warrant a careful study by anyone who is interested in trading.

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