渡轮停运，通向市区的主要公路——M5隧道关闭了。
Ferries were suspended and the M5 tunnel, a major road into the city, was closed.
这一设计包含了一条足够细的隧道，当它关闭时，里面完全没有载流子(电子或空穴)，当它打开时，里面便充满了载流子，起到了阀门的作用。
The design incorporates a channel thin enough to become entirely devoid of carriers (ie, free electrons or holes) when switched off, thus acting as a valve, yet full of them when switched on.
我们在这城市里有三个隧道而其中一个必须被关闭。
We had three tunnels in the city and one needed to be shut down.
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