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Electric Backpack 1. Backpacks(背包) 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 dont mind carrying a heavy load, your backpacks might also power your MP3 player, keep your cell phone running, and maybe even light your way home. 2. Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia(费城) and the Marine Biological Laboratory in Woods Hole(美国马萨诸塞州的一个渔村，也是许多重要研究机构所在地), Mass(Massachusetts 的缩写：马萨诸塞州，美国东北部的一个州)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 (全球定位系统) receivers(接收机), night-vision goggles(夜视镜), and other battery-powered devices to get around and do their work.. The backpacks electricity-generating feature could dramatically reduce the amount of a wearers load now devoted to spare batteries, report Rome and his colleagues in the Sept. 9 Science6. 3. The backpacks electricity-creating powers depend on springs used to hang a cloth pack from its metal frame. The frame sits against the wearers back, and the whole pack moves up and down as the person walks. A gear mechanism converts vertical(垂直的) movements of the pack to rotary (旋转的)motions of an electrical generator, producing up to 7.4 watts(瓦(特)). | 
