Quantum tunneling is an effect where a particle can pass through a barrier it would not normally have the energy to overcome.

量子隧穿效应是指粒子能够穿过正常来说它的能量不足以通过的障碍。

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It can allow a particle to pass through a physical barrier that should be impenetrable, or can allow an electron to escape from the pull of the nucleus without having the kinetic energy to do so.

它能让粒子通过不可逾越的物理障碍，或让电子不用动能就脱离原子核的吸引力。

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It can pass through the surface the barrier, and has the reduction line, the air raid defense, easy space of planes merits and so on to adjust temperature and not to occupy a land area.

它能穿越地表的障碍，并有缩短线路、防空袭、容易调温和不占地面空间等优点。

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And even pedestrians might have to pass through a customs barrier.

NPR: Border Rules May Alter Life on Canada-Vermont Line