【单选题】
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. InDecember 1997, one passenger died and a hundred others were injured when unexpected rough air caused a UnitedAirlines flight over the Pacific to drop 300 metres 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 RodBogue, project manager at NASA’sDryden Flight ResearchCenter inEdwards,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 theDoppler 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 airspee
D、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 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountere
D、
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.
The last paragraph tells us, among other things, that
A．the lidar detector needs improvement.
B．many airlines are interested in the system.
C．passengers often forget to fasten their seatbelts.
D、the lidar detector can be used in a wide range of areas.
网考网参考答案：A
网考网解析：
此题也为判断题。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测定范围。据此可以判断，雷达尚需改进，故A为正确答案。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>
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. InDecember 1997, one passenger died and a hundred others were injured when unexpected rough air caused a UnitedAirlines flight over the Pacific to drop 300 metres 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 RodBogue, project manager at NASA’sDryden Flight ResearchCenter inEdwards,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 theDoppler 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 airspee
D、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 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountere
D、
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.
The last paragraph tells us, among other things, that
A．the lidar detector needs improvement.
B．many airlines are interested in the system.
C．passengers often forget to fasten their seatbelts.
D、the lidar detector can be used in a wide range of areas.
网考网参考答案：A
网考网解析：
此题也为判断题。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测定范围。据此可以判断，雷达尚需改进，故A为正确答案。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>
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