题目内容
B
Most musicians agree that the best violins were first made in Italy.They were made in Cremona, Italy, about 200 years ago.These violins sound better than any others.They even sound better than violins made today.Violin makers and scientists try to make instruments like the old Italian violins.But they aren’t the same.Musicians still prefer the old ones.No one really knows why these old Italian violins are so special, but many people think they have an answer.
Some people think it is the age of the violins.They say that today’s violins will also sound wonderful someday.But there is a problem here.Not all old violins sound wonderful.Only those from Cremona are special.So age cannot be the answer.There must be something different about Cremona or those Italian violin makers.
Other people think the secret to those violins is the wood.The wood of the violin is very important.It must be from certain kinds of trees.It must not be too young or too old.Perhaps the violin makers of Cremons knew something special about wood for violins.
But the kind of wood may not be so important.It may be more important to cut the wood in a special way.Wood for a violin must be cut very carefully.It has to be the right size and shape.The smallest difference will change the sound of the violin.Musicians sometimes think that this was the secret of the Italians.Maybe they understood more than we do about how to cut the wood.
Size and shape may not be the answer either.Scientists measured these old violins very carefully.They can make new ones that are exactly the same size and shape.But the new violins still do not sound as good as the old one.Some scientists think the secret may be the varnish, which covers the wood of the violin and makes it look shiny.It also helps the sound of the instrument.No one knows what the Italian violin makers used in their varnish.So no one can make the same varnish today.
There may never be other violins like the violins of Cremona.Their secret may be lost forever.Young musicians today hope this is not true.They need fine violins.But there aren’t very many of the old violins left.Also, the old violins are very expensive.Recently, a famous old Italian violin was sold for about US $ 300,000!
60.This passage is about _______.
A.making violins B.musical instruments
C.scientific ideas D.the old Italian violins
61.The best violins _______.
A.are made with modern techniques B.were lost many years ago
C.were made in Italy 200 years ago D.were made by scientists.
62.Some people think that modem violins ______.
A.will sound better in the future B.will sound worse in the future
C.sound wonderful naturally D.will never be as old as those from Cremona
63.Violins made today _______.
A.look the same as the old ones
B.sound the same as the old ones
C.are better than the old ones
D.have the same varnish as the old ones
60 ----63DCAA
Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are much larger and heavier than the devices themselves. University of Missouri(MU) researchers are developing a nuclear energy source that is smaller, lighter and more efficient.
“To provide enough power, we need certain methods with high energy density(密度)”,said Jae Kwon, assistant professor of electrical and computer engineering at MU. “The radioisotope(放射性同位素) battery can provide power density that is much higher than chemical batteries.”
Kwon and his research team have been working on building a small nuclear battery, presently the size and thickness of a penny, intended to power various micro/nanoelectromechanreal systems (M/NEMS). Although nuclear batteries can cause concerns, Kwon said they are safe.
“People hear the word ‘nuclear’ and think of something very dangerous,” he said, “However, nuclear power sources have already been safely powering a variety of devices, such as pace-makers, space satellites and underwater systems.”
His new idea is not only in the battery’s size, but also in its semiconductor(半导体). Kwon’s battery uses a liquid semiconductor rather than a solid semiconductor.
“The key part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure(晶体结构) of the solid semiconductor,” Kwon said, “By using a liquid semiconductor, we believe we can minimize that problem.”
Together with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, Kwon is working to build and test the battery. In the future, they hope to increase the battery’s power, shrink its size and try with various other materials. Kwon said that battery could be thinner than the thickness of human hair.
1.Which of the following is true of Jae Kwon?
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A.He teaches chemistry at MU. |
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B.He developed a chemical battery. |
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C.He is working on a nuclear energy source. |
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D.He made a breakthrough in computer engineering. |
2. Jae Kwon gave examples in Paragraph 4_________.
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A.to show chemical batteries are widely applied. |
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B.to introduce nuclear batteries can be safely used. |
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C.to describe a nuclear-powered system. |
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D.to introduce various energy sources. |
3.Liquid semiconductor is used to _________.
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A.get rid of the radioactive waste |
B.test the power of nuclear batteries. |
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C.decrease the size of nuclear batteries |
D.reduce the damage to lattice structure. |
4.According to Jae Kwon, his nuclear battery _______.
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A.uses a solid semiconductor |
B.will soon replace the present ones. |
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C.could be extremely thin |
D.has passed the final test. |
5.The text is most probably a ________.
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A.science news report |
B.book review |
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C.newspaper ad |
D.science fiction story |