托福备考的一大重要途径就是各类双语材料的拓展阅读，而材料的选择异常关键，一般来说我们会比较推荐大家选择难度接近托福的文章，文章题材也最好是和托福常考常关注的话题相关。下面的这篇经济学人双语素材难度适中，非常适合入门托福的童鞋拿来揣摩研读作者写作风格与思路，培养语感和英文材料熟练度。
Air travel
Mechanical engineers
Tiny robots will inspect and fix jet engines from the inside
航空旅行
机械工程师
微型机器人将从内部检修喷气式发动机
IF YOU are reading this while sitting in an aircraft and are of a nervous disposition, do not be alarmed, but the temperature inside the jet engines keeping you aloft probably exceeds the melting point of the materials that those engines are made from. That they do not consequently turn into a molten mess is a feat of modern engineering. It involves a combination of tough alloys and advanced production techniques, such as 3D printing, which allow components to be made with tiny channels through which cooling air circulates. Parts exposed to the most extreme temperatures, which can reach more than 1,300°C, are given additional protection with a coating of special heat-resisting ceramics.
如果你看这篇文章时正在坐飞机，而你是个比较容易紧张的人，请不要因为接下来的文字而惊慌：带你在高空飞行的喷气式发动机内部的温度之高，可能要超过发动机制造材料的熔点。但发动机并没有因此而熔化成一堆烂铁，实在是现代工程技术的一项重大成就。这包括坚固的合金和先进的生产工艺，比如3D打印。3D打印能制造出带有细微通道的零部件，冷却用的空气可在这些通道中流通。那些暴露在最极端温度——可能超过1300°C——中的零部件还会被包裹上一层特殊的耐热陶瓷，作为额外的保护措施。
New jet engines are designed to run hot because that results in a more complete combustion, which lowers fuel consumption and cuts emissions. Hot engines, though, need nurturing. Nowadays the three big aircraft-engine makers, General Electric (GE), Rolls-Royce and Pratt & Whitney, usually include servicing as part of their sales, and many jet engines are leased on a “power-by-the-hour” contract. This means regular check-ups and maintenance are in the interests of airlines and producers alike. The difficult bit is inspecting an engine without dismantling it. That requires taking the aircraft to which the engine is attached out of service. And, with a power-by-the-hour contract, when a plane disappears into the workshop, it is not just the airline that loses money, but the engine maker, too. The hunt is therefore on for faster and more efficient ways to keep engines in tip-top condition.
新的喷气式发动机要在发热的状态下运转，是因为这能实现更充分的燃烧，从而降低燃油消耗并减少排放。不过，在高温下工作的发动机需要保养。如今，世界三大航空发动机制造商——通用电气、罗尔斯·罗伊斯(Rolls-Royce)和普惠发动机公司(Pratt & Whitney)，通常都将维修作为销售的一部分，而且还有许多喷气式发动机是以“按小时包修”的合同租出去的。这表明定期检查和养护对航空公司和制造商都有好处。难题在于如何在不拆解的情况下检查发动机。这需要搭载发动机的飞机停止服务。另外，在按小时包修合同下，当一架飞机进了维修车间，亏钱的不只是航空公司，还有发动机制造商。因此，人们正在搜寻能够更快、更有效地让发动机保持最佳状态的方法。
Don Lipkin, a chief scientist at GE Global Research in Niskayuna, New York, and his colleagues Todd Danko and Kori Macdonald, think they have come up with one. They are developing tiny robots which can venture inside an engine to inspect its innards and carry out any necessary repairs. Eventually, these robots may be able to work while a plane is waiting at a gate between flights.
在位于纽约尼什卡纳( Niskayuna)的通用电气全球研究中心，首席科学家唐·利普金(Don Lipkin)和他的同事托德·丹科(Todd Danko)、科里·麦克唐纳(Kori Macdonald)认为他们已经找到了办法。他们正在研发一些微型机器人，能够探入发动机的内部检查设备并完成必要的修理。最终，这些机器人或许可以趁飞机在航班间歇停在登机口时展开工作。
Send in the microbots
派微型机器人出马
Dr Lipkin’s robots are being tested in a laboratory, but he hopes to have them ready to go inside operating aircraft by the end of the year. To start with, they will conduct inspections. Later, once techniques are perfected, they will begin making repairs. Such robots will also be used to inspect and repair GE’s gas turbines. These are jet engines used in power plants to generate electricity, rather than as propulsion devices. But they, too, would benefit from reduced downtime for maintenance.
利普金的机器人目前还在实验室中接受测试，不过他希望年底之前能让它们进入服役的飞机内部。一开始，这些机器人会开展检查，等技术完善后，它们将着手维修。通用电气还会用它们来检修公司的燃气轮机。这些燃气轮机是在发电厂里发电用的喷气式发动机，而不是用作推进装置，但它们也会因为缩短停机维修的时间而受益。
Inspecting the fan blades that draw air into the front of an engine is reasonably straightforward, because those blades are large and visible. But things get harder the deeper you go. Following the fan are a series of closely packed blades that compress the air before it arrives at the combustion chamber. When the compressed air reaches that chamber, and is mixed with fuel and ignited, the resulting hot gases then blast out of the rear, providing thrust. Some of those gases are diverted through a series of stubby turbine blades near the back of the engine. These, via shafts, turn the fan and the compressor, and thus keep the whole arrangement running.
那些将空气吸入发动机前部的风扇叶片检查起来比较简单，因为它们和大而且可见。不过越深入发动机内部，情况就越棘手。风扇后方密集排布着许多压气机叶片，它们负责在空气进入燃烧室前将其压缩。当压缩后的空气进入燃烧室，与燃料混合并点燃，产生的炽热气体就从后部喷射而出，提供一部分推进力。其中一些气体会转道经过靠近发动机尾部的短粗的涡轮扇叶，通过传动轴来推动风扇和压气机转动，从而维持整个装置的运转。
In a working engine, all of these components are so tightly packed together that sometimes the only way to peek inside is by inserting an endoscope (a camera on a flexible tube) through a hole in the engine’s casing. But the view is limited. The researchers’ robots, however, are small enough to navigate their way around all the various blades, photographing everything they see and relaying the pictures wirelessly to technicians. Then, once the pictures have been analysed, the robot itself can often effect a repair.
在运行中的发动机内，这些组件都被安装得十分紧凑，有时只能通过发动机罩上的一个洞插入内窥镜(安装在挠性管上的摄像头)来查看，但视野有限。上述研究人员的机器人却小到足以在各种扇叶间游走，拍摄所见的一切并以无线方式将照片传输给技术人员。图片经分析后，机器人通常自己就能修理部件。
The team’s robots come in several varieties. One is about the size of a small envelope and is flexible. It runs along a sort of rack-and-pinion track that is inserted into the back of the engine. The track is made from a long strip of plastic which, with a twisting action, can be flicked between the blades. The robot is attached to the track and employs a toothed drive-mechanism which connects to a series of holes in the plastic strip and permits the device to propel itself along. Once it has arrived at its destination, it expands so that it is gripped between a pair of blades. The track is withdrawn and the robot hitches a ride on the blades as these are rotated manually by technicians. That way it can photograph internal surfaces adjacent to the blades as it passes. Once its job is done, it can be pulled out on a cord.
该研究团队的机器人有若干种类。一种是大小与小信封相近的柔性机器人，沿着一种插入发动机后部的齿轮齿条轨道行进。轨道由一长条塑料制成，可做出扭转的动作而在扇叶间快速移动。机器人附着在轨道上并运用一个带齿的传动装置，此装置与塑料条上的一串孔洞相连，让机器人能推动自身向前移动。一旦到达目的地，它便会扩张，直至夹在两片扇叶中间。随后轨道被撤出，技术人员手动转动扇叶，机器人就能搭乘扇叶的“便车”，“沿途”拍摄临近扇叶的内表面。机器人完成任务后，可用一根绳子把它拉出来。
Another type of robot, a few centimetres square, crawls inside an engine on caterpillar tracks. A third version uses magnetic wheels. These let it grip surfaces made with specialised steels in the cold front section of ground-based gas turbines, and thus work upside down if necessary. All the robots are driven by a human operator using a tablet computer. To repair things, the machines are fitted with tiny arms that reach out and inject ceramic coatings from a cartridge of material to fill in any damaged areas. The robots can also carry small grinding tools, to smooth down ragged surfaces.
另一种机器人几厘米见方，靠履带在发动机内爬行。还有一种机器人采用磁轮，能吸附在地面燃气轮机前端低温部分用特殊钢材制成的表面上，必要时能倒立工作。所有这些机器人都由操作员用一个平板电脑来操控。它们安装了微型手臂，维修时可以伸出手臂并将材料盒中的陶瓷涂层注入受损部位。这些机器人还可携带小型打磨工具，让粗糙的表面重新变平整。
Such repairs may not be as permanent as those during a full rebuild, but they are good enough to extend the time an engine can operate between major overhauls. Moreover, data collected by the robots would be used by GE to update the engine’s “digital twin”. These twins are virtual replicas, held on a computer, and contain the latest operating data sent via satellites from sensors mounted inside engines. The twins serve as test beds for spotting problems before they get serious. This means preventive maintenance can be carried out and unscheduled visits to the workshop avoided.
这种修理的效果也许不如全面维修持久，但也足以延长发动机接受大修之前的工作时间。此外，通用电气还可以用机器人收集到的数据来升级该发动机的“数字双胞胎”。这些“双胞胎”是在计算机上运行的发动机的虚拟复制品，包含发动机内的传感器搜集并通过卫星发送的最新操作数据。“数字双胞胎”充当试验平台，在问题变严重之前将其识别出来，这样就可以实施预防性维护并避免突发性维修。
Robots will allow much finer monitoring of an engine’s wear and tear. That varies, according to how aircraft are used—even by particular pilots, some of whom push aircraft engines harder than others do—and where in the world a plane most often operates. Airborne particles, particularly in polluted regions, can block the tiny cooling channels that help stop an engine melting. Wind-blown sand grains in places such as the Middle East subject blades to increased abrasion. Jet engines are already remarkably reliable, with the need for an in-flight shutdown now in the order of once in 20,000 hours of operation, which means a pilot may never experience a failure in his entire career. Tiny robots will make them more so.
有了机器人，对发动机磨损状况的监测将变得精细很多。磨损情况的差异取决于飞机的使用情况(甚至与飞行员有关——他们当中有些人用发动机时较其他人更猛)，同时也取决于飞机最常在世界哪个地区飞行。悬浮粒子会堵住防止发动机熔化的微小冷却通道，尤其是在在受污染的地区。在中东等地，风吹起的沙粒会加重叶片的磨损。喷气式发动机已经相当安全可靠，如今大约飞两万小时才会发生一次空中停车，这意味着飞行员在整个职业生涯中可能都不会遇到故障，有了微型机器人就更是如此了。
托福阅读能力的提升需要我们在真题练习的基础上多进行各类拓展材料的阅读延伸，才能不断提升对英文书面内容的敏感度，提高阅读速度和关键信息抓取能力。
