托福備考的一大重要途徑就是各類雙語材料的拓展閱讀，而材料的選擇異常關鍵，一般來說我們會比較推薦大家選擇難度接近托福的文章，文章題材也最好是和托福常考常關注的話題相關。下面的這篇經濟學人雙語素材難度適中，非常適合入門托福的童鞋拿來揣摩研讀作者寫作風格與思路，培養語感和英文材料熟練度。
Air travel
Mechanical engineers
Tiny robots will inspect and fix jet engines from the inside
航空旅行
機械工程師
微型機器人將從內部檢修噴氣式發動機
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.
如果你看這篇文章時正在坐飛機，而你是個比較容易緊張的人，請不要因為接下來的文字而驚慌：帶你在高空飛行的噴氣式發動機內部的溫度之高，可能要超過發動機制造材料的熔點。但發動機并沒有因此而熔化成一堆爛鐵，實在是現代工程技術的一項重大成就。這包括堅固的合金和先進的生產工藝，比如3D打印。3D打印能制造出帶有細微通道的零部件，冷卻用的空氣可在這些通道中流通。那些暴露在最極端溫度——可能超過1300°C——中的零部件還會被包裹上一層特殊的耐熱陶瓷，作為額外的保護措施。
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.
新的噴氣式發動機要在發熱的狀態下運轉，是因為這能實現更充分的燃燒，從而降低燃油消耗并減少排放。不過，在高溫下工作的發動機需要保養。如今，世界三大航空發動機制造商——通用電氣、羅爾斯·羅伊斯(Rolls-Royce)和普惠發動機公司(Pratt & Whitney)，通常都將維修作為銷售的一部分，而且還有許多噴氣式發動機是以“按小時包修”的合同租出去的。這表明定期檢查和養護對航空公司和制造商都有好處。難題在于如何在不拆解的情況下檢查發動機。這需要搭載發動機的飛機停止服務。另外，在按小時包修合同下，當一架飛機進了維修車間，虧錢的不只是航空公司，還有發動機制造商。因此，人們正在搜尋能夠更快、更有效地讓發動機保持最佳狀態的方法。
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.
在位于紐約尼什卡納( Niskayuna)的通用電氣全球研究中心，首席科學家唐·利普金(Don Lipkin)和他的同事托德·丹科(Todd Danko)、科里·麥克唐納(Kori Macdonald)認為他們已經找到了辦法。他們正在研發一些微型機器人，能夠探入發動機的內部檢查設備并完成必要的修理。最終，這些機器人或許可以趁飛機在航班間歇停在登機口時展開工作。
Send in the microbots
派微型機器人出馬
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.
利普金的機器人目前還在實驗室中接受測試，不過他希望年底之前能讓它們進入服役的飛機內部。一開始，這些機器人會開展檢查，等技術完善后，它們將著手維修。通用電氣還會用它們來檢修公司的燃氣輪機。這些燃氣輪機是在發電廠里發電用的噴氣式發動機，而不是用作推進裝置，但它們也會因為縮短停機維修的時間而受益。
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.
那些將空氣吸入發動機前部的風扇葉片檢查起來比較簡單，因為它們和大而且可見。不過越深入發動機內部，情況就越棘手。風扇后方密集排布著許多壓氣機葉片，它們負責在空氣進入燃燒室前將其壓縮。當壓縮后的空氣進入燃燒室，與燃料混合并點燃，產生的熾熱氣體就從后部噴射而出，提供一部分推進力。其中一些氣體會轉道經過靠近發動機尾部的短粗的渦輪扇葉，通過傳動軸來推動風扇和壓氣機轉動，從而維持整個裝置的運轉。
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.
在運行中的發動機內，這些組件都被安裝得十分緊湊，有時只能通過發動機罩上的一個洞插入內窺鏡(安裝在撓性管上的攝像頭)來查看，但視野有限。上述研究人員的機器人卻小到足以在各種扇葉間游走，拍攝所見的一切并以無線方式將照片傳輸給技術人員。圖片經分析后，機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.
該研究團隊的機器人有若干種類。一種是大小與小信封相近的柔性機器人，沿著一種插入發動機后部的齒輪齒條軌道行進。軌道由一長條塑料制成，可做出扭轉的動作而在扇葉間快速移動。機器人附著在軌道上并運用一個帶齒的傳動裝置，此裝置與塑料條上的一串孔洞相連，讓機器人能推動自身向前移動。一旦到達目的地，它便會擴張，直至夾在兩片扇葉中間。隨后軌道被撤出，技術人員手動轉動扇葉，機器人就能搭乘扇葉的“便車”，“沿途”拍攝臨近扇葉的內表面。機器人完成任務后，可用一根繩子把它拉出來。
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.
另一種機器人幾厘米見方，靠履帶在發動機內爬行。還有一種機器人采用磁輪，能吸附在地面燃氣輪機前端低溫部分用特殊鋼材制成的表面上，必要時能倒立工作。所有這些機器人都由操作員用一個平板電腦來操控。它們安裝了微型手臂，維修時可以伸出手臂并將材料盒中的陶瓷涂層注入受損部位。這些機器人還可攜帶小型打磨工具，讓粗糙的表面重新變平整。
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.
這種修理的效果也許不如全面維修持久，但也足以延長發動機接受大修之前的工作時間。此外，通用電氣還可以用機器人收集到的數據來升級該發動機的“數字雙胞胎”。這些“雙胞胎”是在計算機上運行的發動機的虛擬復制品，包含發動機內的傳感器搜集并通過衛星發送的最新操作數據。“數字雙胞胎”充當試驗平臺，在問題變嚴重之前將其識別出來，這樣就可以實施預防性維護并避免突發性維修。
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.
有了機器人，對發動機磨損狀況的監測將變得精細很多。磨損情況的差異取決于飛機的使用情況(甚至與飛行員有關——他們當中有些人用發動機時較其他人更猛)，同時也取決于飛機最常在世界哪個地區飛行。懸浮粒子會堵住防止發動機熔化的微小冷卻通道，尤其是在在受污染的地區。在中東等地，風吹起的沙粒會加重葉片的磨損。噴氣式發動機已經相當安全可靠，如今大約飛兩萬小時才會發生一次空中停車，這意味著飛行員在整個職業生涯中可能都不會遇到故障，有了微型機器人就更是如此了。
托福閱讀能力的提升需要我們在真題練習的基礎上多進行各類拓展材料的閱讀延伸，才能不斷提升對英文書面內容的敏感度，提高閱讀速度和關鍵信息抓取能力。
