科学美国人60秒 SSS Cool Coating Chills in Sunlight
时间：2019-01-20 作者：英语课 分类：2017年Scientific American(二)月
You've probably seen pictures of Greek villages, where every house is painted bright white. The paint reflects the intense sunlight of the Mediterranean 1. And it works pretty well to keep the houses from heating up in the sun. But it doesn't actively 2 cool them.
To understand why, consider what the white paint does. Here's how optical scientist Xiaobo Yin of the University of Colorado describes it: "It's a mirror for the sunlight, it's also a mirror for the radiation as well." And it might seem like reflecting all those incoming rays would be a good thing. But the benefit is limited. Because what it really means, Yin says, is that the houses, well, "they don't release much energy." Release more energy, again in the form of infrared 3 radiation, aka heat—and you effectively get free A/C.
So Yin and his colleagues built a material that does exactly that: reflects visible light, but also emits infrared wavelengths 4. Which gives it the power to actually cool. It's two layers: a top layer of polymer, packed with glass beads 5 just eight microns across—so they can absorb and then emit infrared radiation. And a silver coating on the bottom.
The coating reflects 96 percent of solar radiation—a slight improvement on white and silver paint. But the game-changing part: it also has a cooling power of about 100 watts 6 per square meter. Translation: enough to cool a frying-pan-sized amount of water to about 15 degrees Fahrenheit 7 cooler than ambient temps. Even while sitting in the sun. The finding is in the journal Science. [Yao Zhai et al., Scalable-manufactured randomized glass-polymer hybrid 8 metamaterial for day-time radiative cooling]
That cool water example has wide applications. "This water can be used to cool a house, cool a data center, or even cool a thermoelectric power plant." That's Yin's colleague at the University of Colorado, Ronggui Yang. And he says it's a cheap way to cool things down. Just don't put the material directly on your roof. "It also cools down during the wintertime. And you do not want that to happen." No. Definitely… not cool.
—Christopher Intagliata
[The above text is a transcript 9 of this podcast.]
- The houses are Mediterranean in character.这些房子都属地中海风格。
- Gibraltar is the key to the Mediterranean.直布罗陀是地中海的要冲。
- During this period all the students were actively participating.在这节课中所有的学生都积极参加。
- We are actively intervening to settle a quarrel.我们正在积极调解争执。
- Infrared is widely used in industry and medical science.红外线广泛应用于工业和医学科学。
- Infrared radiation has wavelengths longer than those of visible light.红外辐射的波长比可见光的波长长。
- I find him difficult to talk to—we're on completely different wavelengths. 我没法和他谈话，因为我们俩完全不对路。 来自《简明英汉词典》
- Sunlight consists of different wavelengths of radiation. 阳光由几种不同波长的射线组成。 来自辞典例句
- a necklace of wooden beads 一条木珠项链
- Beads of perspiration stood out on his forehead. 他的前额上挂着汗珠。
- My lamp uses 60 watts; my toaster uses 600 watts. 我的灯用60瓦，我的烤面包器用600瓦。
- My lamp uses 40 watts. 我的灯40瓦。
- He was asked for the boiling point of water in Fahrenheit.他被问到水的沸点是华氏多少度。
- The thermometer reads 80 degrees Fahrenheit.寒暑表指出华氏80度。
- That is a hybrid perpetual rose.那是一株杂交的四季开花的蔷薇。
- The hybrid was tall,handsome,and intelligent.那混血儿高大、英俊、又聪明。
- A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
- They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。