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　　北京新航道学校致力于雅思培训为大家提供权威参考资料。暑假已经结束了，赶在这个时间参加雅思的考生朋友们也完成了自己的学习计划，总结这个暑期的阅读试题，我们为大家进行了整理，希望对那些正在准备考试同学有所帮助。雅思阅读对于国内考生来说难度较大，除了专业水平之外，还极度考验着同学的耐心和细心。下面就给大家一些资料，希望对于同学的英语成绩有所帮助。

　　Time to cool it

　　1 REFRIGERATORS are the epitome of clunky technology: solid, reliable and just a little bit dull. They have not changed much over the past century, but then they have not needed to. They are based on a robust and effective idea--draw heat from the thing you want to cool by evaporating a liquid next to it, and then dump that heat by pumping the vapour elsewhere and condensing it. This method of pumping heat from one place to another served mankind well when refrigerators' main jobs were preserving food and, as air conditioners, cooling buildings. Today's high-tech world, however, demands high-tech refrigeration. Heat pumps are no longer up to the job. The search is on for something to replace them.

　　2 One set of candidates are known as paraelectric materials. These act like batteries when they undergo a temperature change: attach electrodes to them and they generate a current. This effect is used in infra-red cameras. An array of tiny pieces of paraelectric material can sense the heat radiated by, for example, a person, and the pattern of the array's electrical outputs can then be used to construct an image. But until recently no one had bothered much with the inverse of this process. That inverse exists, however. Apply an appropriate current to a paraelectric material and it will cool down.

　　3 Someone who is looking at this inverse effect is Alex Mischenko, of Cambridge University. Using commercially available paraelectric film, he and his colleagues have generated temperature drops five times bigger than any previously recorded. That may be enough to change the phenomenon from a laboratory curiosity to something with commercial applications.

　　4 As to what those applications might be, Dr Mischenko is still a little hazy. He has, nevertheless, set up a company to pursue them. He foresees putting his discovery to use in more efficient domestic fridges and air conditioners. The real money, though, may be in cooling computers.

　　5 Gadgets containing microprocessors have been getting hotter for a long time. One consequence of Moore's Law, which describes the doubling of the number of transistors on a chip every 18 months, is that the amount of heat produced doubles as well. In fact, it more than doubles, because besides increasing in number, the components are getting faster. Heat is released every time a logical operation is performed inside a microprocessor, so the faster the processor is, the more heat it generates. Doubling the frequency quadruples the heat output. And the frequency has doubled a lot. The first Pentium chips sold by Dr Moore's company, Intel, in 1993, ran at 60m cycles a second. The Pentium 4--the last "single-core" desktop processor--clocked up 3.2 billion cycles a second.

　　6 Disposing of this heat is a big obstruction to further miniaturisation and higher speeds. The innards of a desktop computer commonly hit 80℃. At 85℃, they stop working. Tweaking the processor's heat sinks (copper or aluminium boxes designed to radiate heat away) has reached its limit. So has tweaking the fans that circulate air over those heat sinks. And the idea of shifting from single-core processors to systems that divided processing power between first two, and then four, subunits, in order to spread the thermal load, also seems to have the end of the road in sight.

　　7 One way out of this may be a second curious physical phenomenon, the thermoelectric effect. Like paraelectric materials, this generates electricity from a heat source and produces cooling from an electrical source. Unlike paraelectrics, a significant body of researchers is already working on it.

　　8 The trick to a good thermoelectric material is a crystal structure in which electrons can flow freely, but the path of phonons--heat-carrying vibrations that are larger than electrons--is constantly interrupted. In practice, this trick is hard to pull off, and thermoelectric materials are thus less efficient than paraelectric ones (or, at least, than those examined by Dr Mischenko). Nevertheless, Rama Venkatasubramanian, of Nextreme Thermal Solutions in North Carolina, claims to have made thermoelectric refrigerators that can sit on the back of computer chips and cool hotspots by 10℃. Ali Shakouri, of the University of California, Santa Cruz, says his are even smaller--so small that they can go inside the chip.

　　经过老师课堂经验发现，雅思阅读对考生来说就是不能合理分配阅读题干的时间和答题时间，这还需要同学在平日里多加练习，以便应试速度，老师提醒大家，成绩绝非一朝一夕之事，勤奋练习才能收益。最后祝你考试顺利。

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