60秒科学:大象能负重的原因
大多数四条腿动物用后腿前进，前腿停步，而研究表明，大象用四条腿来加速和“刹车”。
Elephants. They’re the SUVs of the animal kingdom. They’re big and rugged 1, and can carry lots of cargo 2. And now a study in the Proceedings 3 of the National Academy of Sciences suggests they come equipped with the quadruped version of all-wheel drive.
When it comes to locomotion 4, elephants are not exactly fleet of foot. And they seem to hold their legs straighter than other animals do, at least when they walk. So scientists [John R. Hutchinson et al] set out to examine more closely how elephant limbs mechanically move all that mass around.
Six Asian elephants walked or ran over a sidewalk equipped with pressure sensors 5, as the scientists used high-speed infrared 6 video cameras to monitor their gait. And they found that elephant legs actually do bend enough to provide significant leverage 7 when on the move. More surprising is that pachyderms’ front and rear legs are on equal footing when it comes to acceleration 8 and braking. All other four-legged animals, like dogs or cats or horses, divvy up those duties. With their rear legs powering the push forward, and their front legs acting 9 as brakes.
That arrangement lets elephants trade speed for stability. Sadly, it does nothing for their fuel economy. Of course, they do have the roomiest trunk.
—Karen Hopkin
- Football players must be rugged.足球运动员必须健壮。
- The Rocky Mountains have rugged mountains and roads.落基山脉有崇山峻岭和崎岖不平的道路。
- The ship has a cargo of about 200 ton.这条船大约有200吨的货物。
- A lot of people discharged the cargo from a ship.许多人从船上卸下货物。
- He was released on bail pending committal proceedings. 他交保获释正在候审。
- to initiate legal proceedings against sb 对某人提起诉讼
- By land,air or sea,birds are masters of locomotion.无论是通过陆地，飞越空中还是穿过海洋，鸟应算是运动能手了。
- Food sources also elicit oriented locomotion and recognition behavior patterns in most insects.食物源也引诱大多数昆虫定向迁移和识别行为。
- There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
- Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句
- Infrared is widely used in industry and medical science.红外线广泛应用于工业和医学科学。
- Infrared radiation has wavelengths longer than those of visible light.红外辐射的波长比可见光的波长长。
- We'll have to use leverage to move this huge rock.我们不得不借助杠杆之力来移动这块巨石。
- He failed in the project because he could gain no leverage. 因为他没有影响力，他的计划失败了。
- All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
- He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。