练习材料：
[Day 1773 2019-08-04]
Lesson 29-1 The hovercraft
Many strange new means of transport have been developed in our century, the
strangest of them being perhaps the hovercraft. In 1953, a former electronics engineer
in his fifties, Christopher Cockerell, who had turned to boat-building on the Norfolk
Broads, suggested an idea on which he had been working for many years to the British
Government and industrial circles. It was the idea of supporting a craft on a 'pad', or
cushion, of low-pressure air, ringed with a curtain of higher pressure air. Ever since,
people have had difficulty in deciding whether the craft should be ranged among ships,
planes, or land vehicles -- for it is something in between a boat and an aircraft. As a
shipbuilder, Cockerell was trying to find a solution to the problem of the wave
resistance which wastes a good deal of a surface ship's power and limits its speed. His
answer was to lift the vessel out of the water by making it ride on a cushion of air, no
more than one or two feet thick. This is done by a great number of ring-shaped air jets
on the bottom of the craft.
任务配置：L0+L1+L4
知识笔记：
hovercraft n. 气垫船; 气垫运载工具;
ringed adj. 戴戒指的; 有环纹(或环斑)的;
v. 包围; 环绕; 给…戴上金属环(以便将来辨认); 绕…画圆; 把…圈起来;
v. 给…打电话; 发出铃声; (使) 发出钟声，响起铃声;
curtain n. 窗帘; 帘; 幔; (遮隔房间的) 帷幔; 床帷; (舞台上的) 幕，幕布，帷幕;
v. 给(窗户或房间)装上帘子;
land vehicles 陆上交通工具
vessel n. 大船; 轮船; (盛液体的) 容器，器皿; (人或动物的) 血管，脉管; (植物的) 导管;
air jets 网络 气体射流;
练习感悟：
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