2013理工[1]14871.pdf
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1、 1 13)Better Solar Energy Systems:More Heat,More Light Solar photovoltaic thermal energy systems,or PVTs,generate both heat and electricity,but (1)until now they havent been very good at the heat-generating part compared to a stand-alone solar thermal collector.Thats because they operate at low temp
2、eratures to cool crystalline silicon solar cells,which lets the silicon generate more(2)electricity but isnt a very efficient way to gather heat.Thats a problem of (3)economics Good solar hot-water systems can harvest much more energy than a solar-electric system at a substantially lower (4)cost And
3、 it,s also a space problem:photovoltaic cells can take up all the space on the roof,leaving little room for thermal applications.In a pair of studies,Joshua Pearce,an associate professor of materials science and engineering,has devised a (5)solution in the form of a better PVT made with a different
4、kind of silicon.His research collaborators are Kunal Girotra from ThinSilicon in California and Michael Pathak and Stephen Harrison from Queens University,Canada.Most solar panels are made with crystalline silicon,but you can also make solar cells out of amorphous silicon,(6)commonly known as thin-f
5、ilm silicon.They dont create as much electricity,but they are lighter,f lexible,and cheaper.And,because they(7)require much less silicon,they have a greener footprint.Unfortunately,thin-film silicon solar cells are (8)vulnerable to some bad-news physics in the form of the Staebler-Wronski effect.“Th
6、at means that their efficiency (9)drops when you expose them to light pretty much the worst possible effect for a solar cell,”Pearce explains,which is one of the(10)reasons thin-film solar panels make up only a small fraction of the market.However,Pearce and his team found a way to engineer around t
7、he Staebler-Wronski effect by incorporating thin-film silicon in a new (11)type of PVT.You dont have to cool down thin-film silicon to make it work.In fact,Pearces group discovered that by heating it to solar-thermal operating temperatures,near the boiling(12)point of water,they could make thicker c
8、ells that largely (13)overcame the Staebler-Wronski effect.When they applied the thin-f ilm silicon directly to a solar thermal energy (14)collector,they also found that by baking the cell once a day,they (15)boosted he solar cells electrical efficiency by over 10 percent.48-Researchers Discover Why
9、 Humans Began Walking U pright 研究人员发现人类开始直立行走的原因 1.Which of the following statements is NOT true according to the f irst two paragraphs?A Many people question the simple human activities of walking and carrying items.2.Dr.Richmond conducted the experiment with the purpose of finding B what made our
10、ancestors walk upright.3.Kyoto,Universitys study discovered that chimpanzees.C liked coula nuts better than oil palm nuts.4.Why did the chimpanzees walk on two limbs during Kyoto Universitys experiment?D Because they wanted to carry more nuts with two free limbs.5.What can we infer from the reading
11、passage?D Human walking on two legs developed as a means of survival.15)“Liquefaction”Key to Much of Japanese Earthquake Damage The massive subduction zone1 earthquake in Japan caused a significant level of soil liquefaction2 that has surprised researchers with its (1)widespread severity,a new analy
12、sis shows.Weve seen localized3 examples of soil liquefaction as extreme as this before,but the distance and (2)extent of damage in Japan were unusually severe,said Scott Ashford,a professor of geotechnical engineering4 at Oregon State University5.Entire structures were tilted and sinking into the se
13、diments,Ashf ord said.The shifts in soil destroyed water,drain and gas pipelines6,crippling the utilities and infrastructure these communities need to (3)function .We saw some places that sank as much as four feet.Some degree of soil liquefaction7 is common in almost any major earthquake.Its a pheno
14、menon in which soils soaked with water,particularly recent sediments or sand,can lose much of their (4)strength and flow during an earthquake.This can allow structures to shift or sink or (5)collapse .But most earthquakes are much (6)shorter than the recent event in Japan,Ashford said.The length of
15、the Japanese earthquake,as much as f ive minutes,may force researchers to reconsider the extent of liquefaction damage possibly occurring in situations such as this.With such a long-lasting earthquake,we saw (7)how structures that might have been okay after 30 seconds just continued to sink and tilt
16、 as the shaking continued for several more minutes,he said.And it was clear that younger sediments,and especially areas built on (8)recently filled ground,are much more vulnerable.The data provided by analyzing the Japanese earthquake,researchers said,should make it possible to improve the understan
17、ding of this soil (9)phenomenon and better prepare for it in the future.Ashford said it was critical for the team to collect the information quickly,(10)before damage was removed in the recovery efforts.Theres no doubt that well learn things from what happened in Japan10 that11 will help us to reduc
18、e risks in other similar (11)events,Ashford said.Future construction in some places may make more use of techniques known to reduce liquefaction,such as better compaction to make soils dense,or use of reinforcing stone columns.Ashford pointed out that northern California have younger soils vulnerabl
19、e to liquefaction-on the coast,near river deposits or in areas with filled ground.The young sediments,in geologic terms,may be those (12)deposited within the past 10,000 years or more.In Oregon,for instance,that describes much of downtown Portland,the Portland International Airport and other cities.
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