20 18 April IELTS reading simulation topic: It's time to get cold.

IELTS reading test needs to be well prepared, so what are the IELTS reading simulation questions? It must be a concern of many people who go abroad. Let's take a look at the 20 18 IELTS reading simulation topic: Time is getting cold, welcome to read.

20 18 IELTS reading simulation topic: It's time to get cold.

20061February 65438 +3 days

Excerpt from The Economist print edition.

1 refrigerator is the epitome of heavy technology: solid and reliable, but a little boring. In the past century, they haven't changed much, but they don't need to change. They are based on a powerful and effective idea-absorbing heat by evaporating the liquid next to the object you want to cool, and then releasing heat by pumping the steam elsewhere and condensing it. When the refrigerator's main job is to preserve food and cool buildings as an air conditioner, this method of pumping heat from one place to another serves human beings well. However, today's high-tech world needs high-tech refrigeration. The heat pump is no longer qualified for this job. People are looking for something to replace them.

A group of candidate materials are called paraelectric materials. When the temperature changes, these batteries are just like batteries: when electrodes are connected to the batteries, they will generate current. This effect is used in infrared cameras. A tiny array of paraelectric materials can sense the heat emitted by people, for example, and then the electrical output mode of the array can be used to construct an image. But until recently, no one has paid much attention to the reverse process of this process. However, the opposite situation exists. Apply an appropriate current to the paraelectric material and it will cool down.

Alex Mishchenko of Cambridge University is studying this reverse effect. Using commercially available paraelectric films, he and his colleagues have produced a temperature drop five times greater than any previous record. This may be enough to change this phenomenon from laboratory curiosity to commercial application.

As for what these applications might be, Dr. Mishchenko is not quite clear. Nevertheless, he set up a company to track them down. He expects to apply his findings to more efficient household refrigerators and air conditioners. However, the real money may be in cooling the computer.

Gadgets containing microprocessors have become more and more popular for a long time. Moore's law describes that the number of transistors on a chip doubles every 18 months, and one of the results is that the heat generated also doubles. In fact, it has not only doubled, because in addition to increasing the number, the speed of components is getting faster and faster. Every time a microprocessor performs a logical operation, it releases heat, so the faster the processor, the more heat it generates. Doubling the frequency will quadruple the heat output. And the frequency has been multiplied many times. The first Pentium chips sold by Dr. Moore's company Intel in 1993 run 60 million times per second. Pentium 4, the last "single-core" desktop processor, runs 3.2 billion times per second.

Dealing with this heat is a big obstacle to further miniaturization and speed improvement. The interior of a desktop computer usually reaches 80 degrees Celsius. They stop working at 85℃. Adjusting the processor's radiator (copper or aluminum box designed to dissipate heat) has reached its limit. The same is true for adjusting the fan above the heat sink. The idea of transferring from a single-core processor to a system that distributes processing power to two subunits and then to four subunits to share the cooling load seems to have come to an end.

One way to solve this problem may be the second strange physical phenomenon, thermoelectric effect. Like paraelectric materials, this material generates electricity from a heat source and cooling from a power source. Unlike Shundian, a large number of researchers have been studying it.

The secret of a good thermoelectric material is a crystal structure, in which electrons can flow freely, but the path of phonons (heat-carrying vibrations larger than electrons) will be continuously interrupted. In practice, this technique is difficult to achieve, so the efficiency of thermoelectric materials is lower than that of paraelectric materials (or at least lower than that of materials studied by Dr. Mishchenko). However, Rama Venkatasubramanian of Nextreme Thermal Solutions in North Carolina claims to have made a thermoelectric refrigerator, which can be placed on the back of a computer chip to cool the hot spot 10℃. Ali Shakouri of the University of California, Santa Cruz, says his chip is even smaller-small enough to fit in.

Nevertheless, the last word of computer cooling may appear in a system that is even less technological than a heat pump-a miniature car radiator. Last year, Apple introduced a personal computer, which was cooled by liquid. The liquid was pumped into the radiator through a small channel in the processor, releasing heat into the atmosphere. In order to improve this, IBM's research laboratory in Zurich is trying to stir the liquid with tiny jets, so as to ensure that all the liquid finally touches the outside of the channel, where the heat exchange takes place. Therefore, in the future, the combination of microchannel and thermoelectric or paraelectric may cool the computer. It can be said that the old and the new go hand in hand.