扫码加入训练营

牢记核心词

学习得礼盒

考研英语阅读篇章: 壁虎足部的魔力

2014-08-14 15:07:58来源:新东方在线编辑整理

  阅读基础如滴水穿石,连载考研英语阅读篇章,希望大家能保持阅读好习惯。


考研英语阅读篇章: 壁虎足部的魔力

  f you've ever spent any time watching a gecko(壁虎), you may have wondered about theiruncanny(神秘的) ability to adhere to any surface -- including upside down on ceilings. It turns out the little lizards can turn the "stickiness" of toe hairs on the bottom of their feet on and off, which enables them to run at great speeds or even cling to ceilings without expending much energy. In the Journal of Applied Physics, from AIP Publishing, Oregon State University (OSU) researchers describe their work exploring the subtleties of geckos' adhesion system mechanism.

  "Since the time of the ancient Greeks, people have wondered how geckos are able to stick to walls -- even Archimedes is known to have pondered this problem," said Alex Greaney, co-author and an assistant professor of engineering at OSU. "It was only very recently, in 2000, that Kellar Autumn and colleagues proved unequivocally(明确地) that geckos stick using van der Waals forces."

  Van der Waals forces are weak atomistic level forces, "but geckos are able to take advantage of them because of a remarkable system of branched hairs called 'seta' on their toes," Greaney explained. "These seta and their hierarchy can deform to make intimate contact with even very rough surfaces -- resulting in millions of contact points that each are able to carry a small load."

  Geckos -- as well as spiders and insects -- have independently evolved the same adhesion system mechanism and have been using it for millions of years.

  "Understanding the subtleties of the process for switching stickiness on and off is groundbreaking," said Greaney. "By using mathematical modeling, we've found a simple, but ingenious, mechanism allows the gecko to switch back and forth between being sticky or not. Geckos' feet are by default nonsticky, and this stickiness is activated through application of a small shear force. Gecko adhesion can be thought of as the opposite of friction."

考研英语核心词汇营

背词+听课+练习+督学,学习得礼盒

更多资料
更多>>
更多内容

关注新东方在线考研服务号

获得21考研真题及答案解析

1. 打开手机微信【扫一扫】,识别上方二维码;
2.点击【关注公众号】,获取资料大礼包。

考研资料大礼包
近10年考研真题及答案免费下载
更多>>
更多公开课>>
更多>>
更多资料