经济学人下载:脑震荡(1)

Anyone who has experimented as a child with maize starch and water knows about shear-thickening.
任何在童年做过玉米淀粉加水实验的人都知道剪切增稠。

A mixture of these substances is easy to stir slowly, but solidifies when you speed the stirring up, only to liquefy again when you stop.
慢慢搅拌这些物质的混合物很容易，但当你加速搅拌时，混合物会凝固，只有当你停止搅拌时，它才会再次液化。

It's fun. But it may also be important. For years, people have been trying to apply the principle to armour. Now, it seems, one group has succeeded.
很有趣，但也很重要。多年来，人们一直尝试将这个原理应用于装甲部队。现在有一组团队似乎已经成功了。

The result will not stop a speeding bullet. But, incorporated into a helmet, it might save the wearer from concussion.
结果是，它无法阻止一颗飞速的子弹，但如果与头盔结合在一起，或许可以让佩戴者免于脑震荡。

Construction workers, soldiers and sportsmen and women all wear safety helmets
建筑工人、士兵、运动员都要戴安全帽

that contain impact-absorbing suspension systems based on foam pads or webbing straps.
其中含有基于泡沫垫或织带的可吸收冲击的悬架装置。

Eric Wetzel of the United States Army Research Laboratory and his colleagues propose replacing these
美国陆军研究所的Eric Wetzel和他的同事提议将这些替换成

with fabric tubes containing a shear-thickening material that the lab has developed.
由实验室研发的一种含有剪切增稠材料的织物圆筒。

These tubes, which behave like viscous, speed-sensitive bungee cords, are known as rate-activated tethers, or RATS.
这些类似粘性、速度敏感型弹力绳的织物圆筒被称为速率激活拴绳或RATS。

A standard bungee cord's useful property is its elasticity. This first stores energy as the jumper falls and then releases it as he bounces back up again.
标准弹力绳的有用特性是它的弹性。现在蹦极者跳下去的时候储存能量，然后在弹起时释放能量。

A RAT bungee jump, however, would be a one-way trip. RATS absorb energy when stretched in the way that an elastic substance does,
但RAT弹力绳将是一次单程旅行。当以弹性物质的方式拉伸时，RATS吸收能量，

but, unlike an elastic, they do not then give it back when released. That would leave a jumper dangling at the bottom.
但与弹性物质不同的是，它们在被松开时不会释放能量。这样将会让蹦极者在底部晃荡。

Dr Wetzel's team were developing RATS as ankle supports to absorb landing shock for parachutists
Wetzel博士的团队正在研发RATS作为一种吸收跳伞者着陆时震动力的踝护

when they realised that the tethers they were working with had just the qualities required for helmet suspensions:
当时他们意识到，他们使用的拴绳拥有头盔悬架所需的品质：

they provide instant strong resistance, which increases with impact speed.
它们提供即时强大的抵抗，这增加了冲击速度。

Existing military helmets protect in situations like travel over rough terrain, collisions between vehicles and with obstacles,
现有的军用头盔能够在崎岖地形、车辆和障碍物之间的碰撞

and being thrown around by bomb blasts. RATS offer better protection in all these cases.
以及被炸弹炸得四处乱飞等情况下起到保护作用。

Current American-army combat helmets are built to withstand impact velocities of three metres a second,
目前美国陆军的战斗头盔能够承受3米每秒的冲击速度，

with newer models being rated for just over four. Prototype helmets fitted with RAT suspension pass impact tests at five metres a second,
而最新型号的头盔只能承受4米多每秒的冲击速度。配有RAT悬架的原型头盔以每秒5米的速度通过了撞击测试，

which Dr Wetzel says no previous helmet suspension has achieved.
Wetzel博士说，之前的头盔悬架还没有达到这一水平。