题目内容
Electric Backpack
Backpacks are convenient. They can hold your books, your lunch, and a change of clothes, leaving your hands free to do other things. Someday, if you don't mind carrying a heavy load, your backpacks might also power your MF3 player, keep your cell phone running, and maybe even light your way home.
Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia and the Marine Biological Laboratory in Woods Hole, Mass., have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions, search-and-rescue operations, and scientific field studies, people rely increasingly on cell phones, global positioning system (GPS) receivers, night-vision goggles, and other battery-powered devices to get around and do their work. The backpack's electricity-generating feature could dramatically reduce the amount of a wearer's load now devoted to spare batteries, report Rome and his colleagues in the Sept. 9 Science.
The backpack's electricity-creating powers depend on springs used to hang a cloth pack from its metal frame. The frame. sits against the wearer's back, and the whole pack moves up and down as the person walks. A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator, producing up to 7.4 watts.
Unexpectedly, tests showed that wearers of the new backpack alter their gaits in response to the pack's oscillations, so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage, Rome plans to commercialize both electric and non-electric versions of the backpack.
The backpack could be especially useful for soldiers, scientists, mountaineers, and emergency workers who typically carry heavy backpacks. For the rest of us, power-generating backpacks could make it possible to walk, play video games, watch TV, and listen to music, all at the same lime. Electricity-generating packs aren't on the market yet, but if you do get one eventually, just make sure to look both ways before crossing the street!
Backpacks are convenient because
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Light Night, Dark Stars
Thousands of people around the globe step outside to gaze at their night sky. On a clear night, with no clouds, moonlight, or artificial lights to block the view. people can see more than 14,000 stars in the sky, says Dennis Ward. an astronomer with the University Corporation for Atmospheric Research (UCAR) in Boulder. Colo. But when people are surrounded by city lights, he says, they're lucky to see ISO stars.
If you've ever driven toward a big city at night and seen its glow from a great distance, you've witnessed fight pollution. It occurs when light from streetlights, office buildings, signs, and other sources streams into space and illuminates the night sky. This haze of light makes many stars invisible to people on Earth. Even at night, big cities like New York glow from light pollution, making stargazing difficult.
Dust and particles of pollution from factories and industries worsen the effects of light pollution. "If one city has a lot more light pollution than another." Ward says, "that city will suffer the effects of light pollution on a much greater scale."
Hazy skies also make it far more difficult for astronomers to do their jobs.
Cities are getting larger. Suburbs are growing in once dark. rural areas. Light from all this new development is increasingly obscuring the faint light given off by distant stars. And if scientists can't locate these objects, they can't learn more about them.
Light pollution doesn't only affect star visibility. It can harm wildlife too. It's clear that artificial light can attract animals, making them go off course. There's increasing evidence, for example, that migrating birds use sunsets and sunrises to help find their way, says Sydney Gauthreaux Jr., a scientist at Clemson University in South Carolina. "When light occurs at night," he says, "it has a very disruptive influence." Sometimes birds fly into lighted towers, high-rises, and cables from radio and television towers. Experts estimate that millions of birds die this way every year.
When can people see 14,000 stars？
第一节
听下面5段对话。每段对话后有一道小题，从题中所给的A、B、C三个选项中选出最佳选项，并标在试卷的相应位置。听完每段对话后，你都有10秒钟的时间来回答有关小题和阅读下一小题。每段对话仅读一遍。
听力原文：M: Hello. This is Tom speaking. May I speak to Rose？
W: I'm sorry she isn't in at the moment. May I take a message？
M: No, thank you. I'll ring her again later.
What does Tom want to do later？
听力原文：W: What's the problem？
M: I can't figure out how to put the page numbers on. I've done everything and they aren't showing up.
W: Let's see. Did you press Shift F8？
M: Yes, I did that. Then I hit P for page and N for number.
W: That's good. Did you type in the page number where you want the numbering to start？
M: Yes. I typed the number 1.
W: Right. Did you press Enter？
M: Yes.
W: How about F7 to return to the document？
M: I did that. But no numbers showed up on the screen.
W: Unhuh. Did you print it？
M: No, I don't want to print it until I see the numbers.
W: Well, that's the problem then. The numbers don't show up on the screen. But they will on the printed copy. Let's try that.
M: Okay. You do it this time, and I'll watch.
W: Well, I'll do it as you want, but it would be better if you let me talk you through it.
M: I don't know.
W: Really. Once you've done it with someone coaching you, it's easier to do it on your own. Don't worry. This is my job.
M: Oh, all right. Shift F8.
W: Now hit P for page and N for number.
M: And the page number I want to start with which is number 1.
W: Great! Just press Enter, then F7 to return to the document, and you're all set to print. Then you'll see those numbers.
(20)
Which one is not the reason why American-born Asian women are paid better than Latinas？
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