【英语时差8,16】令人喜欢的火车隧道

When a train enters a tunnel the air can't simply be pushed aside, it must rush backward through the narrow space between the train and the tunnel walls to fill the space behind the train. This speeding air creates a suction on the train, just like opening the window of a speeding car can suck out maps and paper. This lowers the air pressure inside the train, which can make the passengers' ears go pop. How are trains and tunnels designed to reduce this effect?  One way is to try to design a completely air-tight train, like an airplane cabin¹. Unfortunately, this air-tight seal is often hard to maintain², especially if passengers want to walk between cars.

Another way is to design the tunnels to reduce this effect. If the tunnel's diameter³ is much wider than the train's, you reduce the piston-like effect which causes the backward rushing air in the first place. Ventilation shafts⁴ can also help, although it's best if they're designed to do so. If the shafts are too large or too far apart, it can feel like the train is constantly leaving and re-entering the tunnel.

The most famous tunnel is the thirty mile "Chunnel" between England and France. Thirty miles of air is a lot to push around, so engineers have come up with a clever solution. The Chunnel is actually two separate tunnels, connected by cross passages. A Chunnel train doesn't have to squeeze⁵ all that air backward between train and tunnel wall. Those cross passages allow the air to escape sideways--into the second tunnel--greatly improving the air pressure inside the train.  

1 cabin   

n.(结构简单的)小木屋；船舱，机舱

参考例句：

• They threw up a new cabin in a couple of hours.在几小时之内他们就建起了一座新的小屋。
• It's very hot in the cabin;let's go on deck.舱室内很热，我们到甲板上去吧。

2 maintain   

vt.支撑；赡养，抚养；维持，保有

参考例句：

• He has to maintain a large family on a small salary.他不得不依靠很少的工资养活一家人。
• We must do our best to maintain sales at their usual rate.我们要尽力使销售额保持在平日的水平上。

3 diameter   

n.直径

参考例句：

• The circle has a diameter of 6 inches.这个圆直径六英寸。
• A diameter passes through the center of a circle.直径从圆心穿过。

4 shafts   

n.轴( shaft的名词复数 )；（箭、高尔夫球棒等的）杆；通风井；一阵（疼痛、害怕等）

参考例句：

• He deliberately jerked the shafts to rock him a bit. 他故意的上下颠动车把，摇这个老猴子几下。 来自汉英文学 - 骆驼祥子
• Shafts were sunk, with tunnels dug laterally. 竖井已经打下，并且挖有横向矿道。 来自辞典例句

5 squeeze   

vt.硬塞，硬挤；挤压；n.榨；经济困难；拮据

参考例句：

• This machine helps you to squeeze more juice out.这台机器能挤出更多的果汁。
• It was a tight squeeze in the crowded bus.公共汽车上载客太多，挤得很。