公共英语二级考试（模拟试题） |
2006-8-14 6:44:11 点击数： 进入论坛 |
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There are two ways of feeding air to the test section. In the constant flow tunnel, airflow is produced by electric fans. It is forced through the tunnel to the test section, then through another tunnel section back to the starting point for reuse.
The other way involves (卷入) storing high-pressure air in a box, sending it out by a controlling device(装置) to pass through the tunnel and test section into another box. This way is usually used for a very short period of high-speed airflow.
Wind tunnels are usually used to test planes before they are flown. Problems in a plane can be found when it meets the high-speed airflow in the tunnel. For example, if the wings are built so that they would weaken(become weak) at high speeds, this fact can be discovered in the tunnel, saving many lives and millions of dollars.
In a wind tunnel, scientists also find out how different planes will act different speeds. They find out such things as how the air dives by the wing surfaces, how slowly a plane can fly before it starts to drop, and how fast it can climb.
52.Some wind tunnel sections are larger than others because ________.
A. they are used large planes B. stronger wind can be produced in them
C. they are built to meet a higher speed test D. the wind used in them flows at a lower speed
53.Which of the following shows the right way of feeding air to a wind tunnel section usually
used for a high speed test?
( ← = wind flow = test section)
54. “This fact” in paragraph 4 of the text refers to _______.
A. the wing are not good enough B. it costs a lot to test a plane |
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| 2007年4月大考时间 |
| 2007年4月21日-4月22日 |
| 2007年7月加考时间 |
| 2007年7月7日-7月8日 |
| 2007年10月大考时间 |
| 2007年10月27日-10月28日 |
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