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Most of the people _____ to the party were famous scientists.
A. invited B. to invited
C. being invited D. inviting
查看习题详情和答案>>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 / nanoelectromechanical 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?
A. He teaches chemistry at MU.
B. He developed a chemical battery.
C. He is working on a nuclear energy source.
D. He made a breakthrough in computer engineering.
2. Jae Kwon gave examples in Paragraph 4_________.
A. to show chemical batteries are widely applied.
B. to introduce nuclear batteries can be safely used.
C. to describe a nuclear-powered system.
D. to introduce various energy sources.
3. Liquid semiconductor is used to _________.
A. get rid of the radioactive waste
B. test the power of nuclear batteries.
C. decrease the size of nuclear batteries
D. reduce the damage to lattice structure.
4. According to Jae Kwon, his nuclear battery _______.
A. uses a solid semiconductor
B. will soon replace the present ones.
C. could be extremely thin
D. has passed the final test.
5. The text is most probably a ________.
A. science news report B. book review
C. newspaper ad D. science fiction story
查看习题详情和答案>>For Lee Ann Laraway, polio(脑灰质炎) has made almost everything in life just out of reach. But what her hands can't retrieve, her assistant can. Meet Jeannie, a three-year-old help, has become Lee Ann's arms and legs.
Jeannie understands no fewer than 72 commands. To get a feel for what that means, Lee Ann takes us on a shopping trip in San Jose. First stop: The bank, where she got cash from the teller. From the bank, it's on to the drug store, where Jeannie got a candy bar for Lee Ann. Then Jeannie helped pay the cashier, and got change hack.
"When you have a really good working animal, they come and interact with you all the time," Lee Ann said. While there's no argument that Jeannie is an ordinary animal, she wasn't born that way. She was tutored and trained here at a facility that has become the final legacy of one of the Bay Area's most beloved figures.
Canine Companions for Independence sits on twelve acres of land in Santa Rosa donated by late Peanuts cartoonist Charles Shultz, Here, handlers work with specially selected labs for hours a day— but not every dog will make the cut.
The work is serious Business. In the case of hearing dogs, the animals alert their disabled owners to everything from ringing telephones to doorbells.
Other dogs will work with severely disabled patients like eight-year-old Noah Habib of Mountain View who communicates with a special computer. "I like it when new people come up to ask me about my dog," he says. "People are really interested in the dog and will come over and ask to pet her and ask to play with her, and ask about what she does, and these are people that normally might not approach us and want to talk to Noah," says his Dad.
And back in San Jose Lee Ann is arriving home with Jeannie and her groceries. With just one chore left—opening her own door. "You can train a dog to do a lot of things," said Lee Ann. "You cannot give them the heart to do the job, and that is what a good working dog has."
Lee Ann's dog Jeannie cannot ______.
A) get cash at the bank C) pay a cashier for her
B) take on a telephone for her D) open the door
Canine Companions for Independence is a place for ______.
A) severely disabled children to have practice
B) people to donate money or legacy
C) ordinary dogs to be coached
D) people to learn business
Which of the following can replace the phrase "make the cut" (Line 3, Para 4)?
A) become a good working dog C) hurt the coach
B) become a helpful star D) hurt itself
According to Lee Ann, you cannot train an ordinary dog ______.
A) to put things on people's laps C) to always interact with its owner
B) to alert deaf people D) to love working
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