学位英语

The Tiniest Electric Motor in the World

1　Scientists recently made public the tiniest electric motor ever1 built. You could stuff hundreds of them into the period at the end of this sentence. One day a similar engine might power a tiny mechanical doctor that would travel through your body to remove your disease.

2　The motor works by shuffling atoms between two molten metal droplets in a carbon nanotube. One droplet is even smaller than the other. When a small electric current is applied to the droplets, atoms slowly get out of the larger droplet and join the smaller one. The small droplet grows — but never gets as big as the other droplet and eventually bumps into the large droplet. As they touch, the large droplet rapidly sops up the atoms it had previously lost. This quick shift in energy produces a power stroke.2

3　The technique exploits the fact that surface tension — the tendency of atoms or molecules to resist separating — becomes more important at small scales3. Surface tension is the same thing that allows some insects to walk on water.

4　Although the amount of energy produced is small — 20 microwatts — it is quite impressive in relation to the tiny scale of the motor4. The whole setup5 is less than 200 nanometers on a side, or hundreds of times smaller than the width of a human hair. If it could be scaled up to the size of an automobile engine6, it would be 100 million times more powerful than a Toyota Camry's 225 horsepower V6 engine.

5　In 1988, Professor Richard Muller and colleagues made the first operating micromotor, which was 100 microns across7, or about the thickness of a human hair. In 2003, Zettl's group created the first nanoscale motor. In 2006, they built a nanoconveyor, which moves tiny particles along like cars in a factory.

6　Nanotechnology engineers try to mimic nature, building things atom-by-atom. Among other things, nanomotors could be used in optical circuits to redirect light, a process called optical switching. Futurists envision a day when nanomachines, powered by nanomotors, travel inside your body to find disease and repair damaged cells.

注释：

1.ever：比以往任何时候，曾经。如：This is the best book I have ever read.这是我读过的书中最好的一本。

2.power stroke：动力行程

3.at small scales：在小等级上。这里指的是“在纳米等级上”。

4.it is quite impressive in relation to the tiny scale of the motor：与电动机的小等级相比，功率是相当可观了。in relation to是“与……相比”。如：The city is quite large in relation to its population.就人口而言，这个城市相当的大。

5.setup：装置。这里指nanomotor。

6.If it could be scaled up to the size of an automobile engine：如果纳米电动机能按比例放大到汽车发动机的尺寸。scale ... up to是“把……按比例放大到……”。

7.across：从一端到另一端

练习：

1.Paragraph 2 _____

2.Paragraph 4 _____

3.Paragraph 5 _____

4.Paragraph 6 _____

A　An Introduction of a Toyota's 225 Horsepower V6 Engine

B　A Description of the Nanomotor in Terms of Power and Size

C　Surface Tension

D　Previous Inventions of Nanoscale Products

E　The Working Principle of the Nanomotor

F　Possible Fields of Application in the Future

5.Doctors envision that the nanomotor would travel through human bodies to _____.

6.Surface tension means the tendency of atoms or molecules to _____.

7.Nanoconveyors could be used to _____.

8.Applying a small electric current causes atoms to _____.

A　remove disease

B　resist separating

C　shuffle between two molten metal droplets

D　power nanomachines

E　sop up molecules from the large droplet

F　transport nanoscale objects

答案与题解：

1.E　第二段介绍了纳米发动机的工作原理。两小滴金属熔液通上微弱电流，大的小滴的原子就会缓慢逸出，加入小的小滴，后者体积不断增大，到一定阶段，就会与前者碰撞，这时，大的小滴便夺回它失去的原子，这就是一次power stroke(动力行程，动力冲程)，此时就会产生发动机的动力。原子如此来来去去运动，就像发动机活塞一样。这就是纳米发动机的工作原理。所以，E是答案。

2.B　第四段描述了纳米发动机的功率(20微瓦)和体积(200纳米)。选项B用“A description of the nanomotor in terms of power and size”概括本段大意，很准确，所以B是答案。

3.D　第五段介绍了发明纳米发动机之前的一些纳米等级的机械产品，如体积大一些的纳米发动机，微型发动机，纳米传送带，纳米机器等。选项D概括了本段的大意，所以是答案。

4.F　第六段预想了纳米发动机的用途，如用于光电路以改变光的方向(redirect light)和驱动纳米机器进入人体，消灭病灶。选项F是答案，因为“Possible fields of application in the future”概括了本段的大意。

5.A　答案是A。题干出现doctors envision，选项的内容应与医学有关，选项A是remove disease，正好与题干的内容相配，是答案。短文第一段和最后一段也提到纳米发动机进入人体消灭病灶的可能性，证明选A是正确的。

6.B　选B的依据是第三段第一句“surface tension—the tendency of atoms or molecules to resist separating—becomes more important at small scales”。

7.F　题干的nanoconveyor提示我们，纳米传送带的功能自然是传送纳米等级的物体，所以F是答案。

8.C　题干的Applying a small electric current ...在第二段能找到，该段讲的是纳米发动机的工作原理。如果了解原子在两小滴金属熔液中来回运动，产生动力，就会知道C是答案。

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