公共英语五级阅读文章《镍钛合金》

　　公共英语五级的难度较大，考生需要平时在多加练习。下面是小编整理的一篇公共英语五级阅读文章，欢迎阅读。

公共英语五级阅读文章《镍钛合金》

　　Nitinol is one of the most extraordinary metals to be discovered this century: A simple alloy of nickel and titanium, nitinol has some perplexing properties. A metal with a memory, it can be made to remember any shape into which it is fashioned, returning to that shape whenever it is heated.

　　For example, a piece of nitinol wire bent to form a circle that is then heated and quenched will remember this shape. It may then be bent or crumpled, but on reheating, will violently untwist, reforming its original shape. This remarkable ability is called Shape Memory Effect (SME); other alloys, such as brasses, are known to possess it to a limited extent. No one fully understands SME, and nitinol remains particularly perplexing, for, whenever it performs this peculiar feat, it appears to be breaking the laws of thermodynamics by springing back into shape with greater force than was used to deform it in the first place.

　　But not only is nitinol capable of remembering, it also has the ability to "learn". If the heating-cooling-crumpling-reheating process is carried out sufficiently often, and the metal is always crumpled in exactly the same way, the nitinol will not only remember its original shape, but gradually it learns to remember its crumpled form as well, and will begin to return to the same crumpled shape every time it is cooled. Eventually, the metal will crumple and uncrumple, totally unaided, in response to changes in temperature and without any sign of metal fatigue. Engineers have produced prototype engines that are driven by the force of nitinol springing from one shape to another as it alternately encounters hot and cold water. The energy from these remarkable engines is, however, not entirely free: heat energy is required to produce the temperature differences needed to run the engine. But the optimum temperatures at which the metal reacts can be controlled by altering the proportions of nickel to titanium; some alloys will even perform at room temperature. The necessary temperature range between the warm and thecold can be as little as twelve degrees centigrade.

　　镍钛诺是这个世纪所发现的最不寻常的金属之一，作为镍和钛的简单的一种合金，镍钛诺具有一些令人惊叹的特征。这是一种有记忆力的金属，人们可以使它记住它被塑成的任何形状，并在加热后恢复这一形状。

　　比如，一节镍钛诺线圈在加热冷却后会记住圆圈这形状。随后它可能被弯折成其它形状，但一旦再次加热，就会迅速地自动恢复成最初的圆圈状。这种不寻常的能力被称为形状记忆效果(SME)。其它一些合金如黄铜在一定程度上也具有这种特性。目前人们对SME 这一特性尚缺乏透彻的认识，而镍钛诺尤其使人惊奇，因为每当它展现这一惊人的功能时，似乎都违背了热力学原理。因为它在恢复原有形状时所释放的力比人们使它变形所施加的力大得多。

　　镍钛诺不仅有记忆力，还能"学习"。如果加热-冷却-弯曲-再加热这一过程重复一定次数，且每次冷却后它都被丝毫不差地弯成同一形状，它不仅可以记住最初的形状，还能逐渐记住它被弯成的形状，并开始在每次冷却时恢复这一形状。最终，它会自动地随温度变化而弯曲和恢复这些形状，并且没有任何疲劳迹象。工程师们已制造出一些发动机样机，利用镍钛合金在交替遇热水和冷水时迅速改变形状所产生的力做推动力。然而这些神奇的发动机工作时并非完全不耗能，因为必须有热能来制造温差才能使机器运转。但人们可以通过改变合金中镍钛的比例来控制使它反应的最佳温度。有的.镍钛合金甚至能在室温下做出反应，冷暖之间的最小温差只有12℃。

　　附：公共英语五级阅读如何猜词义?

　　一、利用所出现生词的上下文与其意义上的联系或下文进一步的叙述，猜测词义。

　　例一：the female mosquito is a vampire and lives on blood.如不知道vampire的词义，从下文lives on blood(靠吸血而生存)则可得知其词义为吸血昆虫。

　　例二：the old man put on his spectacles and began to read.如不知道spectacles的词义，从下文"戴上'spectacles'后开始阅读"可以猜得其词义"眼镜".

　　二、利用文中的举例猜测词义

　　例三：some artists plan their paintings around geometric forms like squares， circles and triangles.如不知道geometric forms的意思，可从文中所列举的三角形，正方形、圆形来猜得其意义为"几何图形".

　　today young couples who are just starting their households often spend lots of their money on appliances for instance， washing machines， refrigerators and color televisions.如不知道appliances的意思，从文中的举例"washing-machines(洗衣机)，refrigerator(冰箱)，televisions(电视机)"可以猜得该词的意思为"家用电器".

【公共英语五级阅读文章《镍钛合金》】相关文章：

公共英语五级英译汉经典练习题带答案公共英语五级英译汉练习题