2012理工A完形填空word版.doc

Solar Power without Solar Cells A dramatic and surprising magnetic effect of light discovered by University of Michigan1 researchers could lead to solar power without traditional semiconductor-based solar cells. The researchers found a way to make an optical 1 , said Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics. Light has electric and magnetic components. Until now, scientists thought the 2 of the magnetic field were so weak that they could be ignored. What Rand and his colleagues found is that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than 3 expected. 4 these circumstances, the magnetic effects develop strength equivalent to a strong electric effect. This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation, Rand said. In solar cells, the 5 goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load2. Instead of the light being absorbed, energy is stored in the magnetic moment3. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power 6.What makes this possible is a previously undetected brand of optical rectification4, says William Fisher, a doctoral student5 in applied physics. In traditional optical rectification, lights electric field causes a charge separation, or a pulling 7 of the positive and negative charges6 in a material. This sets up a voltage, similar to 8 in a battery. Rand and Fisher found that under the right circumstances and in right types of materials, the lights magnetic field can also create optical rectification. The light must be shone through7 a 9 that does not 10 electricity, such as glass. And it must be focused to an intensity of 10 million watts per square centimeter8. Sunlight isnt this intense on its own, but new materials are being sought that would work at lower intensities, Fisher said. In our most recent paper, we show that incoherent light9 like sunlight is theoretically almost as. 11 in producing charge separation as laser light is, Fisher said. This new 12 could make solar power cheaper, the researchers say. They predict that with improved materials they could achieve 10 percent efficiency in 13 solar power to useable energy. Thats equivalent to todays commercial-grade solar cells. To manufacture 14 solar cells, you have to do extensive semiconductor processing, Fisher said. All we would need are lenses to focus the light and a fiber to guide it. Glass works for 15 . Its already made in bulk10, and it doesnt require as much processing. Transparent ceramics might be even better.Sharks Perform a Service for Earths WatersIt is hard to get people to think of sharks as anything but a deadly enemy. They are thought toattackpeople frequently. But these fish perform a valuableservice for earths waters and for human beings. Yet business and sport fishing3 are threatening theirexistenceSome sharks are at risk of disappearing from EarthWarm weather may influence both fish and shark activity. Many fish swim near coastal areasbecause oftheir warm waters. Experts say sharks may follow the fish into the same areas, wherepeople also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a personfora sea animal, such as a seal or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up. Those are thetimeswhen sharks are looking for food. Experts also say that bright colors and shiny jewelry may cause sharks to attack.A shark has an extremely good sense of smell. It can find small amounts of substances in water, such as blood, body liquids andchemicalsproduced by animals. These powerfulsenseshelp sharks find their food. Sharks eat fish, anyother sharks, and plants that live in the ocean.Medical researchers want to learn more about the sharks body defense, and immunethoseagainst disease. Researchers know that sharksrecoverquickly from injuries. Theystudy the shark in hopes of finding a way to fight human disease.harks are important for the worlds oceansThey eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not become toogreatThis protects the plants and other forms of life that exist in the oceans.Liquefaction Key to Much of Japanese Earthquake Damage The massive subduction zone1 earthquake in Japan caused a significant level of soil liquefaction2 that has surprised researchers with its 1 severity, a new analysis shows. Weve seen localized3 examples of soil liquefaction as extreme as this before, but the distance and 2 of damage in Japan were unusually severe, said Scott Ashford, a professor of geotechnical engineering4 at Oregon State University5. Entire structures were tilted and sinking into the sediments, Ashford said. The shifts in soil destroyed water, drain and gas pipelines6, crippling the utilities and infrastructure these communities need to 3 . We saw some places that sank as much as four feet. Some degree of soil liquefaction7 is common in almost any major earthquake. Its a phenomenon in which soils soaked with water, particularly recent sediments or sand, can lose much of their 4 and flow during an earthquake. This can allow structures to shift or sink or 5 . But most earthquakes are much 6 than the recent event in Japan, Ashford said. The length of the Japanese earthquake, as much as five minutes, may force researchers to reconsider the extent of liquefaction damage possibly occurring in situations such as this8. With such a long-lasting earthquake, we saw 7 structures that might have been okay after 30 seconds just continued to sink and tilt as the shaking continued for several more minutes, he said. And it was clear that younger sediments, and especially areas built on 8 filled ground, are much more vulnerable. The data provided by analyzing the Japanese earthquake, researchers said, should make it possible to improve the understanding of this soil 9 and better prepare for it in the future. Ashford said it was critical for the team to collect the information quickly, 10 damage was removed in the recovery efforts9. Theres no doubt that well learn things from what happened in Japan10 that11 will help us to reduce risks in other similar 11 , Ashford said. Future construction in some places may make more use of techniques known to reduce liquefaction, such as better compaction to make soils dense, or use of reinforcing stone columns. Ashford pointed out that northern California have younger s