8.Owls are equipped with highly developed stealth technology (隱形技術(shù)) that helps them charge towards prey-an animal hunted and eaten by another-undetected,a study has shown.
Owls have flight feathers that absorb aerodynamic sound and control the vibrations (振動(dòng)) that occur when a bird beats its wings.The result is perfect silence as it approaches a mouse or other prey.
Scientists used lasers and high-speed cameras to analyze and compare long-eared owl,eagle and pigeon feathers during flight.While differing in size,all three birds have a similar wing-beat style.
Professor Jinkui Chu led the research.He said,"Many owls have a unique and fascinating ability to fly so silently that they are out of their prey's hearing range,due to their feather structure."
This behaviour has long been of interest to engineers,as we seek to apply the owls'noise-reduction mechanisms (機(jī)制) to other purposes and situations that benefit society.
Now,however,we know the owls'silent flight ability is even better than we thought.Of all birds the owl is the king of acoustic stealth.It not only manages to prevent aerodynamic noise when gliding,but also mechanical noise caused by vibration during flying.
This is remarkable,considering the sudden jumping,bending and twisting the wings are subjected to when flapping and the noise that is created by other birds.
In the scientific world,the process used to remove this mechanical noise is called'damping',which means the removal of mechanical energy from a vibrating system usually by changing it into heat and allowing it to remain steady.
"Our research showed the long-eared owl has superior damping skill,meaning it can remain amazingly stable and remove mechanical noise caused by the movement of its feathers-quite an impressive achievement of engineering.99
He added,"This study will hopefully provide further insight into the owls'silent flight mechanism and help engineers develop ideas for special materials or structures,such as on-shore wind turbines,where similar noise removal can be applied."
29.What can be true about owls according to the text?B
A.They are active during the day.
B.They attract much attention from engineers.
C.They have similar wings to eagles.
D.They beat wings without vibrations.
30.By saying"the owl is the king of acoustic stealth"in Paragraph 6,Jinkui Chu means owlsD.
A.a(chǎn)re good at capturing prey
B.have a good sense of hearing
C.a(chǎn)re good at jumping and twisting
D.have silent flight ability
31.What does the underlined word"it"in Paragraph 8refer to?C
A.Mechanical noise.
B.The vibrating system.
C.Mechanical energy.
D.The removal of mechanical energy.
分析 本文講述了科學(xué)家通過(guò)研究貓頭鷹的飛行特點(diǎn),發(fā)現(xiàn)了它們無(wú)聲飛行的奧妙.
解答 BDC
29.B 考查細(xì)節(jié)理解.根據(jù)"Scientists used lasers and high-speed cameras to analyze and compare long-eared owl"可知,貓頭鷹它們引起了工程師的注意.故選B.
30.D 考查細(xì)節(jié)理解.根據(jù)"Many owls have a unique and fascinating ability to fly so silently that they are out of their prey's hearing range"可知,貓頭鷹具有無(wú)聲的飛行能力.故選D.
31.C 考查細(xì)節(jié)理解.根據(jù)"which means the removal of mechanical energy from a vibrating system"可知,"it"指的是"機(jī)械能".故選C.
點(diǎn)評(píng) 閱讀理解考察學(xué)生的細(xì)節(jié)理解和推理判斷能力,做細(xì)節(jié)理解題時(shí)一定要找到文章中的原句,和題干進(jìn)行比較,再做出正確的選擇.在做推理判斷題不要以個(gè)人的主觀想象代替文章的事實(shí),要根據(jù)文章事實(shí)進(jìn)行合乎邏輯的推理判斷.