The method is that, first the input serial pass a designed filter, then reverse the filtered signal and pass the filter again, at last, reverse the second filtered signal.

其方法为：先将输入序列按顺序滤波，然后将所得结果逆转后反向通过滤波器，再将所得结果逆转后输出。

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If families can afford it, she recommends a reverse osmosis filter, which will eliminate all impurities.

CNN: Is your bottled water safe?

It would also greatly reduce energy costs, since reverse osmosis involves forcing water through filters to remove minerals, and the Perforene filter is so thin that much less pressure is required (graphene is a thousand times stronger than steel).

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