The American Civil Liberties Union has said that full body scans amount to a "humiliating" assault on the dignity of passengers that citizens in a free nation should not have to tolerate.

VOA: standard.2009.12.30

So, if we want to go from that stable state to that less stable state, we need to put in a certain amount of energy to our system, that difference between the free electron and the electron bound to the metal.

所以，如果我们想使电子,从稳态到达不够稳定的状态，我们需要引入一定数量的,能量到系统中，即自由电子和束缚于金属的,电子的能量差。

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