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共用题干 Please Fasten Your SeatbeltsSevere

tikufree2019-12-17  95
问题 共用题干Please Fasten Your Seatbelts
Severe turbulence（湍流）can kill aircraft passengers. Now,in test flights over the Rocky
Mountains , NASA（美国航空航天局）engineers have successfully detected clear-air turbulence up to 10 seconds before an aircraft hits it.
Clear-air turbulence often catches pilots by surprise.Invisible to radar,it is difficult to forecast and can hurl（用力抛出去）passengers about the cabin. In December 1 997 , one passenger died and a hundred others were injured when unexpected rough air caused a United Airlines flight over the Pacific to drop 300 meters in a few seconds.
However,passengers can avoid serious injury by fastening their seatbelts.“It is the only antidote（对策）for this sort of thing,”says Rod Bogue,project manager at NASA's Dryden Flight
Research Center in Edwards,California.
The centre's new turbulence detector is based on lidar,or laser radar. Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air. The technique depends on the Doppler effect.The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air,the speed equals the plane's airspeed.But as the particles swirl（打漩）in rough air,their speed of approach increases or decreases rapidly .The rate of change in speed corresponds to the severity（激烈程度）of the turbulence.
In a series of tests that began last month,a research jet flew repeatedly into disturbed air over the mountain ridges（山脉）near Pueblo , Colorado. The lidar detector spotted turbulence between 3 and 8 kilometers ahead,and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered.
Bogue says that he had“a comfortable amount of time”to fasten his seatbelt. The researchers are planning to improve the lidar's range with a more powerful beam.The system could be installed on commercial aircraft in the next few years.
选项 What does“clear-air turbulence”in Paragraph 1 probably mean?A: A not very rough storm.B: Unexpected disturbed air.C: A kind of visible storm.D: A storm over mountain ridges.
答案B
解析本题问的是“clear-air turbulence”在文中指什么？turbulence的意思就是湍流，根据第二段第二句的说法，clear-air turbulence指的是雷达无法测到的一种turbulence，所以选项B为正确答案。 该题问的是1997年12月联合航空公司的一架班机在碰到这种气流后，遭遇了什么结果？原文讲到造成一人死亡，多人受伤，据此判断，损失惨重，故选C。 此题问气流探测器通过测量什么来判断它的激烈程度？第四段最后一句说“The rate of change in speed corresponds to the severity（激烈程度）of the turbulence.”所以选项 D为正确答案。 此题要求根据第五段的信息判断下面哪句话是正确的。显然，选项A符合原文的意思，为正确答案。 此题是根据最后一段的第二句“The researchers are planning to improve the lidar's range with a more powerful beam.”出的题，这句的意思是说，研究人员正计划采用功能更强大的光束来提高雷达的侧定范围。据此可以判断，雷达尚需改进，故A为正确答案。
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