经济学人The Economist是一份英国的英文新闻周报，分八个版本于每周五向全球发行，编辑部位于伦敦，创办于1843年9月。

  经济学人是一本综合性新闻评论刊物，有商业、国家和地区、经济和金融、科学和技术五大类。其中文章文风紧凑且严谨，对语言精准运用，展现出一种克制的风趣幽默，常运用双关语调侃。

  经济学人对于英语考试的重要性不言而喻，其文章常常出现在雅思托福、SAT、GRE、GMAT、考研英语、四六级、MTI和CATTI的阅读理解真题中。

  今天给大家伙儿一起来分享的是经济学人2020年8月1日期刊中科技栏目的第二篇：RAT tales。

  这篇文章主要介绍了牛顿流体材料（RAT）。作者介绍了RAT的原理，并讲述了研究人员企图将这样一种材料用于军用头盔、安全帽、跳伞踝关节支撑、橄榄球头盔以及一些其他的领域。

  任何小时候尝试过将玉米淀粉加水的人都知道牛顿流体。这些物质混合在一起后，如果缓慢搅拌是很轻松的，但如果加快搅拌速度则会发生凝固，直到停止搅拌混合物才会再次液化。特别有趣，但也很重要。多年来，人们一直试图将这一原理应用于装甲部队。目前有一组研究人员成功了。虽然研究成果没办法阻止高速的子弹。但是，当子弹击中头盔中时，可以使佩戴者免于脑震荡。

  建筑工人，士兵和运动员都需要戴安全帽，这些安全帽往往都装有基于泡沫垫或安全带的减震悬挂系统。美国陆军研究实验室的埃里克·韦策尔和他的同事提议用实验室开发的牛顿流体材料代替这些织物管。这些织物管就像是粘性的，对速度十分敏感的蹦极绳。这种织物管被称为速率激活系绳，简称为RAT。

  标准的蹦极绳的特性是其弹性。蹦极线在人下降时会先存储能量，然后在他再次弹起时释放能量。但是，蹦极跳是种单程旅行。当RAT以弹性物质的方式被拉伸时，RAT会吸收能量，但是与弹性物质不同，RAT不会将能量释放开来，会使跳线

  Dr Wetzel’s team were developing RATs as ankle supports to absorb landing shock for parachutists when they realised that the tethers they were working with had just the qualities required for helmet suspensions: they provide instant strong resistance, which increases with impact speed. Existing military helmets protect in situations like travel over rough terrain, collisions between vehicles and with obstacles, and being thrown around by bomb blasts. RATs offer better protection in all these cases. Current American-army combat helmets are built to withstand impact velocities of three metres a second, with newer models being rated for just over four. Prototype helmets fitted with RAT suspension pass impact tests at five metres a second, which Dr Wetzel says no previous helmet suspension has achieved.

  Wetzel博士的团队正在将RAT开发为踝关节支撑，以吸收跳伞者的着陆冲击，因为他们意识到RAT具有头盔悬挂所需要的特质：RAT提供了即时的强大抵抗力，且这种抵抗力会随着撞击速度的增加而增加。美军现用的军用头盔可以让军人在崎岖不平的地面上行驶，并当车辆与障碍物发生碰撞或被炸弹炸到的情况下为军人提供保护。在所有的这一些状况下，RAT都能为军人提供更好的保护。当前的美国陆军战斗头盔被构造成可承受每秒三米的撞击速度，新型号的防护头盔能承受每秒四米的撞击速度。而配备RAT的头盔在冲击测试中能承受每秒五米的撞击速度，Wetzel博士说，在之前没有一点一款头盔能够达到这个程度。

  Donal McNally, a specialist in biomechanics at the University of Nottingham, in Britain, says that an ideal helmet would make the best use of the space between shell and head, adjusting its stiffness depending on the speed of impact. The RAT design does just that. However, its success will depend on whether the shear-thickening material can be engineered to have the correct stiffness for both slow and fast impacts. Dr McNally notes also that the suspension will require some clever design because the tethers respond only to tension, not compression, making it hard to cope with impacts from all directions.

  英国诺丁汉大学的生物力学专家Donal McNally表示，理想的头盔将能够充分的利用壳体和头部之间的空间，并根据撞击速度调整其硬度。RAT头盔的设计就是这样做的。但是，RAT头盔的成功将取决于能否将牛顿流体材料设计成，不论对慢速还是快速的冲击，头盔都能调整为正确的硬度。McNally博士还指出，头盔悬架需要一些巧妙的设计，因为RAT仅对拉力产生效果，而对压缩无效果，从而难以应对来自各个方向的撞击。

  Dr Wetzel’s priority at the moment is getting industry to share his excitement about the new technology. Firms selling to civilian customers generally work faster than people on the military side of things, he says, and if consumer applications take off that will generate a manufacturing and design base which can support military ones. To this end, his team has retrofitted an American-football helmet with RAT suspension. Head protection is a huge and increasing concern in gridiron football.

  目前，Wetzel博士的第一个任务是向业界分享他对于新技术的兴奋。他说，向民用公司销售产品通常比销售给军事方面的人员更快，而且如果面向消费者的材料应用大范围使用的话，可以将其作为军事产品的制造和设计基础。为此，他的团队为美国橄榄球头盔加装了RAT悬架。对球员头部的保护是橄榄球运动中逐渐重要的关注点。

  There has been a dramatic fall-off in the number of youngsters taking up the sport because of worries about head injuries. Improved protection might help change that. An independent laboratory tested the helmet and, in the most taxing test, found that it reduced the “severity index” (a measure of the likelihood of a wearer suffering brain injury) from 393 for the helmet’s standard version to 190. One of the laboratory’s operators said he had never seen a result of less than 200 on the test concerned.

  由于担心头部受伤，参加橄榄球这项运动的年轻人人数急剧下降。如果加强对头部的保护可能有助于改变这一状况。有一个独立实验室对橄榄球头盔进行了测试，在最严酷的测试中发现，标准头盔的“严重性指数”（衡量佩戴者脑部受伤的可能性）从393降低到了190。 实验室表示，他们之前从未在相关测试中看到低于200的结果。

  Nor are helmets the only possible application for RATs. Dr Wetzel and his team have already tested them as chin straps to hold helmets in place, and as straps for pairs of goggles. RAT-based straps could eventually be useful for everything from hikers’ backpacks to babies’ pushchairs. Whether they will have applications in ships’ ratlines remains to be seen.