2013年职称英语等级考试(理工类A级)真题(3)

A. naked B.cautious C.blind D.private

二、阅读判断

第16题： New Understanding of Natural Silk's Mysteries Natural silk as we all know, has a strength that man-made materials havc long struggled to match. In a discovery that sounds morc like an ancient Chinese proverb than a materials science break- through, MIT rescarchers have discovered that silk gets its strength from its

weakness. Or, more spe- cifically, its many weaknesses. Silk gets its extraordinary durability and ductility（柔韧性）from an un- usual arrangement of hydrogen bonds that are intrinsically very weak but that work together to create a strong, flexible structure. Most materials-especially the ones we engineer for strength- -get their toughness from brittleness. As such, natural silks like those produced by spiders have long fascinated both biologists and engineers because of their light weight, ductility and high strcngth (pound for pound, silk is stronger than stecl and far less brit- tle). But on its face, it doesn't seem that silks should be as strong as they are; molecularly, they are held to- gether by hydrogen bonds, which are far weaker than the covalent(共价的)bonds found in other molecules. To get a better

understanding of how silk manages to produce such strength through such weak bonds, the MIT team created a set of computer models that allowed them to observe the way silk be- haves at the atomic level. They found that the arrangement of the tiny silk nanocrystals（纳米晶体）1S such that the hydrogen bonds are able to work

cooperatively, reinforcing one another against external forces and failing slowly when they do fail, so as not to allow a sudden fracture to spread across a silk structure. The result is natural silks that can stretch and bend while retaining a high degree of strength. But whilc that's all well and good for spiders, bees and the like, this understanding of silk geometry could lead to new materials that are stronger and more ductile than those we can currently manufacture. ()ur best and

strongest materials are generally expensive and difficult to produce (requiring high tempera- ture treatments or cnergy-intensive processes). By looking to silk as a model, researchers could potentially devise new manufacturing methods that rely on inexpensive mlaterials and weak bonds to create less rigid, morc forgiving materials that are nonetheless strongcr than anything currcntly on offer. And if you thought you were going to get out of this matcrials science story without hearing about carbon nanotubes（纳米碳管），think again. The MIT team is already in the lab

looking into ways of synthesizing silk-like structures out of materi- als that are stronger than natural silk-likc carbon nanotubes. Super-silks are on the horizon. 1小题>、 MIT researchers carry out the study to illustrate an ancient Chinesc

proverb. A. Right B.Wrong C.Not mentioned

2小题>、 Silk's strength comcs from its weak hydrogen bonds working togethcr. A. Right B.Wrong C.Not mentioned

3小题>、 Biologist and engineers are interestcd in understanding natural silks because they are very light and brittle. A. Right B.Wrong C.Not mentioncd

4小题>、 lf the hydrogen bonds break due to external forces, they break fast. A.