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论述题 在词频效应的实验中有哪些潜在的自变量，你认为应该怎样控制。
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第二篇 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! What is the most important feature of the backpack invented by Lawrence C. Rome and his colleagues
论述题 简述sternberg的智力三因素理论。
论述题 论述幼儿思维的主要特点。
阅读下面这篇短文，短文后列出7个句子，请根据短文的内容对每个句子做出判断。 Inventor of LED When Nick Holonyak set out to create a new kind of visible lighting using semiconductor alloys, his colleagues thought he was unrealistic. Today, his discovery of light-emitting diodes, or LEDs, are used in everything from DVDs to alarm clocks to airports. Dozens of his students have continued his work, developing lighting used in traffic lights and other everyday technology. On April 23, 2004, Holonyak received the $,500,000 Lemelson-MIT Prize at a ceremony in Washington. This marks the 10th year that the Lemelson-MIT Program at the Massachusetts Institute of Technology (MIT) has given the award to prominent inventors. "Anytime you get an award, big or little, it’s always a surprise," Holonyak said. Holonyak, 75, was a student of John Bardeen, an inventor of the transistor, in the early 1950s. After graduate school, Holonyak worked at Bell Labs. He later went to General Electric, where he invented a switch now widely used in house dimmer switches. Later, Holonyak started looking into how semiconductors could be used to generate light. But while his colleagues were looking at how to generate invisible light, he wanted to generate visible light. The LEDs he invented in 1962 now last about 10 times longer than incandescent bulbs, and are more environmentally friendly and cost effective. Holonyak, now a professor of electrical and computer engineering and physics at the University of Illinois, said he suspected that LEDs would become as commonplace as they are today, but didn’t realize how many uses they would have. "You don’t know in the beginning. You think you’re doing something important, you think it’s worth doing, but you really can’t tell what the big payoff is going to be, and when, and how. You just don’t know," he said. The Lemelson-MIT Program also recognized Edith Flanigen, 75, with the $100,000 Lemelson-MIT Lifetime Achievement Award for her work on a new generation of "molecular sieves," that can separate molecules by size. Holonyak’s colleagues thought he would fail in his research on LEDs at the time when he started it.
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