3.Hummingbirds(蜂鸟) are one of nature's most energetic fliers and the only birds to hover(盘旋) in the air by relying on their strength alone.
Now scientists have found that it is the ratio(比值) of the bird's wing length to its width that makes them so efficient.The discovery is helping experts compete with 42million years of natural selection to build helicopters that are increasingly efficient.
David Lentink,an assistant professor at Stanford University in California,tested wings from 12different species of hummingbirds,which he sourced from museums.He placed them on a machine used to test the aerodynamics(气力学) of the helicopter blades(桨叶).Professor Lentink's team used the same machine to test the blades from an advanced micro-helicopter used by the UK's army.They found that the micro-helicopter's blades are as efficient at hovering as the average hummingbirds.
But while the micro-helicopter's blades kept pace with the average hummingbird wings,they could not keep up with the most efficient hummingbird's wing.The wings of Anna's hummingbird were found to be about 27percent more efficient than the man-made micro-helicopter's blades.
While Professor Lentink wasn't surprised at nature's superiority,he said that helicopter blades have come a long way."The technology is at the level of an average hummingbird,"he said."A helicopter is really the most efficient hovering device that we can build.The best hummingbirds are still better,but I think it's amazing that we're getting closer.It's not easy to match their performance,but if we build better wings with better shapes,we might match hummingbirds."
Professor Lentink said that we don't know how hummingbirds maintain their flight in a strong wind,how they navigate(确定方向) through branches,or how they change direction so quickly.He thinks that great steps could be made by studying wing aspect ratios-the ratio of wing length to wing width.Understanding these abilities and characteristics could be a benefit for robotics and will be the focus of future experiments.
29.What did the scientists find about hummingbirds?C
A.Their wings are long and wide
B.They can hover in the air for a long time
C.The ratio of their wing length to wing width is very important
D.They are the most energetic flier in nature
30.Which is the right order of Professor Lentink's research?D
①Tested wings from different species of hummingbirds
②Got resources from museums
③Analyzed the results and drew a conclusion
④Tested the blades from a micro-helicopter
A.①②③④
B.②①③④
C.②④①③
D.②①④③
31.According to Professor Lentink,what will be the focus of future experiments?D
A.To know how hummingbirds can fly in a strong wind
B.To know how hummingbirds change direction so quickly
C.To develop a new kind of helicopter
D.To study the secrets of hummingbirds.
分析 本文是一篇科教类阅读,属于说明文,主要讲述了蜂鸟是大自然中最有活力的飞行员之一,也是唯一一只依靠自己力量独自翱翔的鸟.现在科学家已经发现,它是鸟翼长度与其宽度的比值,使得它们如此高效.
解答 29.C.细节理解题.根据Now scientists have found that it is the ratio(比值) of the bird's wing length to its width that makes them so efficient.可知,科学家发现蜂鸟的翅膀的长度宽度的比率是非常重要的.故选C.
30.D.细节理解题.根据David Lentink,an assistant professor at Stanford University in California,tested wings from 12different species of hummingbirds,which he sourced from museums.He placed them on a machine used to test the aerodynamics(气力学) of the helicopter blades(桨叶).Professor Lentink's team used the same machine to test the blades from an advanced micro-helicopter used by the UK's army.They found that the micro-helicopter's blades are as efficient at hovering as the average hummingbirds.可知,加利福尼亚州斯坦福大学助理教授大卫•本顿(David Lentink)测试了来自博物馆的12种不同种类的蜂鸟,他们将它们放置在用于测试直升机叶片空气动力学的机器上. Lentink教授的团队使用同一台机器从英国军队使用的先进的微型直升机测试刀片.他们发现,微型直升机的刀片与平均蜂鸟一样高效.故正确顺序为②①④③.故选D.
31.D.推理判断题.根据He thinks that great steps could be made by studying wing aspect ratios-the ratio of wing length to wing width.Understanding these abilities and characteristics could be a benefit for robotics and will be the focus of future experiments.可以推测出,未来实验应该专注于研究蜂鸟的秘密.
点评 本文是一篇科教类阅读,题目涉及多道主旨大意题,细节理解题,推理判断题.做题时学生应仔细阅读原文,把握文章主要内容,联系文章上下文内容并结合所给选项含义,从中选出正确答案,一定要做到有理有据,切忌胡乱猜测.