用户名: 密码: 验证码:    注册 | 忘记密码?


2014-02-27    来源:网络    【      美国外教 在线口语培训

Science and Technology 科技

Flying snakes 飞蛇

Slithering through the air 空中滑行

Fancy aerodynamics explain why some snakes are good gliders

MANY animals have mastered the trick of gliding through the forest canopy. Flying frogs stretch the webbing between the toes of their enlarged feet. Some lizards spread elongated ribs covered in flaps of skin. And the colugo, a strange South-East Asian mammal, can travel as much as 70 metres (230 feet) between trees by spreading a membrane of skin that connects its limbs. Despite a lack of obvious body parts that can double up as a decent pair of wings, some snakes, too, can glide for remarkable distances.

To discover how snakes manage it Jake Socha of Virginia Tech and his colleagues conducted a series of test flights with paradise tree snakes, a mildly venomous variety found in parts of Asia. They launched the snakes from the top of a 15-metre tower and used four video cameras to construct 3-D images of the animals' trajectories. The results, just published in Bioinspiration and Biomimetics, show not only that flying snakes are surprisingly good aviators but also that they employ some complex aerodynamic tricks.
为了查明蛇类如何成功的飞行很远,维吉尼亚理工学院的Jake Socha和其同事用一些天堂树蛇做了一系列的飞行试验,这是一种毒性适中的蛇,它生长在亚洲部分地区。研究人员使树蛇从15米高的塔顶端飞行,过程中使用了4个摄影机拍摄蛇滑行的轨迹,以拍摄成三维立体图像。不久前在生物灵感和仿生学上发布的结果显示:飞蛇的飞行不仅令人叹为观止,并且飞行过程中使用了一些在空气动力方面的很复杂的技巧。

A paradise tree snake flattens its body into an aerofoil-like shape that can provide a degree of lift before it takes off from a branch by jumping upwards. It then falls at a steep angle and starts undulating from side to side. As it gains speed its glide path becomes shallower, allowing it to cover a greater distance. The researchers found some snakes could glide for 24 metres.

The 3-D analysis showed the snakes take up a staggered posture when gliding, with their bodies angled upwards at about 25° to the oncoming air and their heads slightly higher than their tails. Dr Socha says this orientation seems to provide the creatures with an aerodynamic advantage. As a result of it, the wake of air forced backwards by one segment of the snake's undulating body may provide extra lift to the segment behind in the sidewinding glide. Flying fish rely on a similar flow of accelerated air from their pectoral fins to provide lift to their smaller pelvic fins. Indeed, it is possible that the effect works both ways, and that rearward segments provide lift to those in front.

The snakes are also surprisingly maneuverable and have been seen to turn in mid-air. To find out if this might be deliberate, Dr Socha limited their view from the tower so that they could see only straight ahead when they launched themselves. Once airborne, and thus able to observe trees to the side of their glide-paths, some of the snakes turned towards them.

Dr Socha, who studies the relationship between form and function in animals, was partly funded in his snake research by America's Defence Advanced Research Projects Agency, which said it was interested in the science but obviously wonders about military applications.
研究动物的构成和功能的Socha 博士在对蛇进行研究时得到了美国国防发展研究项目的资助,它称它对这部分科学很感兴趣,但也明显质疑是否可以将这部分科学应用到军事领域。

Dr Socha does not expect to see snakelike drones in the skies soon. However, the ability to slither through holes, to swim and to climb trees and rocks, as well as to glide between elevated features of the landscape, is an attractive mixture for designers of robotic vehicles. The staggered-wing effect, in which the front of the body helps to provide lift for the back, may also be of interest to aircraft engineers. In the long term, then, the world's battlefields may see machines that resemble some people's worst nightmares, slithering as they do towards the enemy both on the ground and through the air.

手机上普特 m.putclub.com 手机上普特
发表评论 查看所有评论
用户名: 密码: 验证码:
  • 推荐文章
  • 资料下载
  • 讲座录音