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  3. One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile

One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile

admin2015-04-10  31
问题     One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile world inflicts on them. A machine, by contrast, has to wait for someone to fix it. But that may change if researchers of self-repairing materials have their way. Two groups in America and Britain are trying to create composite materials that mend themselves if they get cracked, in much the same way that an animal’s broken bone heals itself. The difference is that these materials will heal in minutes rather than months.
    Such self-healing composites may take a while to enter everyday use. But if they can be made reliable they will be welcome in high-stress applications. Jeffrey Moore and his colleagues at the University of Illinois are working on the problem by adding extra components to their composites. These composites consist of fibres embedded in a plastic matrix. The main extra component added by Dr. Moore is a sprinkling of tiny capsules containing a chemical. If the composite cracks, the capsules near the crack break open and release the chemical molecules, which link together to form another type of plastic that binds the crack together and heals the material.
    Ian Bond and his colleagues at the University of Bristol’s department of aerospace engineering are taking a slightly different approach. They use glass fibres rather than carbon fibres in their composite and, instead of adding capsules, they have put the healing molecules into the fibres themselves. The molecules in question are the two ingredients of epoxy resin. Half the fibres contain one ingredient and half contain the other. A crack in the material breaks the fibres, releasing the ingredients which react, form more epoxy, and thus mend the crack. The advantage of this approach is that it retains the basic fibre-plus-matrix structure of the material. Adding capsules changes that and risks weakening it. The disadvantage is that capsules are easier to make than hollow, fluid-filled fibres.
    Whichever system is adopted, two further things are needed. One is a way of checking that a component really has healed. The other is a way to top up the healing molecules once some of them have been used. A repaired area would develop a bruise. Topping up the supply of healing fluid might be done by mimicking another biological system—the network of blood capillaries that supplies living tissues with the stuff they need to thrive. Dr. Moore and Dr. Bond are attempting to borrow from nature this way. If they succeed, the machines of the future will have longer and healthier lives.
What are the American and British groups busy doing?
选项 A、Creating self-repairing materials for machines.
B、Developing composite materials for animals capable of being restored by human beings.
C、Making materials that will heal in months automatically for machines.
D、Inventing for machines materials that can be repaired by human beings.
答案A
解析 美国和英国的研究小组在干什么?[A]为机器生产自我修复材料。[B]为动物研发可以被人类修复的合成材料。[C]为机器制作可以在几个月内自动恢复的材料。[D]为机器创造可以被人类修复的材料。第一段最后提到了美国和英国的两个研究小组正在试图生产一种合成材料，当出现裂痕的时候这种材料可以自我修复，就像动物修复其断裂的骨骼一样。两者的区别是这些材料可以在几分钟内完成自我修复，而不需要几个月的时间。故[A]正确。
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