首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
Sunlight is free, but that is no reason to waste it. Yet even the best silicon solar cells—by far the most【C1】________sort—conve
Sunlight is free, but that is no reason to waste it. Yet even the best silicon solar cells—by far the most【C1】________sort—conve
admin
2022-01-04
17
问题
Sunlight is free, but that is no reason to waste it. Yet even the best silicon solar cells—by far the most【C1】________sort—convert only a quarter of the light that falls on them. Silicon has the【C2】________of being cheap: manufacturing improvements have brought its price to a point where it is snapping at the heels of fossil fuels.【C3】________many scientists would like to replace it【C4】________something fundamentally better.
John Rogers, of the University of Illinois, Urbana-Champaign, is one. The cells he has【C5】________can convert 42.5% of sunlight.【C6】________improved, Dr Rogers reckons, their efficiency could rise to 50%. Their【C7】________is that they are actually not one cell, but four, stacked one on top of another.
Solar cells are made of semiconductors, and every type of semiconductor has a【C8】________called a band gap that is different from that of other semiconductors. The band gap【C9】________the longest wavelength of light a semiconductor can absorb (it is transparent to longer wavelengths). It also fixes the【C10】________amount of energy that can be【C11】________from shorter wavelength. The result is that long-wavelength photons are lost and short-wave ones incompletely utilised.
Dr Rogers【C12】________this by using a different material for each layer of the stack. He chooses his materials【C13】________the bottom of the band gap of the top layer matches the top of the band gap of the one underneath, and so on【C14】________the stack. Each layer thus【C15】________off part of the spectrum, converts it efficiently into electrical energy and passes the rest on.
The problem is that the materials needed to make these semiconductors are【C16】________But Dr Rogers has found a way to overcome this.【C17】________solar-cell modules are completely covered by semiconductor, but in his only 0.1% of the surface is so covered. The semiconducting stacks, each half a millimeter square, are【C18】________over that surface many dots. Each stack then has a pair of cheap glass lenses【C19】________over it. These focus the sun’s light onto the stack, meaning that all【C20】________light meets a semiconductor.
【C7】
选项
A、secret
B、measure
C、prescription
D、rule
答案
A
解析
此处要求填入主语,而that引导的表语从句则是说明主语的身份或性质。表语从句意为“它们其实不是一块电池,而是四块,一块叠在另一块上面”,解释了电池为何能有如前所述的高转化率,故应选A项secret“秘诀,秘密”。表语从句表述的不是B项measure“测量;尺度”,也与C项prescription“处方”和D项rule“规定”无关,三项均不能与表语从句相对应。
转载请注明原文地址:https://kaotiyun.com/show/DZY4777K
0
考研英语二
相关试题推荐
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Thosedaysarelonggonewhenplacingatelephonecallmeantsimplypickingupthereceiverandaskingtheoperatortopatchyou
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
随机试题
孙卿又名()
患者,男,28岁。上呼吸道感染后2周,出现肉眼血尿、颜面水肿入院。体检:血压20/13.5kPa(150/100mmHg),尿蛋白(+),尿红细胞满视野,血肌酐180μmol/L。(假设信息)如果患者按上述诊断治疗2个月,尿检蛋白(++),红细
急性腹膜炎最重要的体征是
鉴别心源性哮喘与支气管哮喘的要点是
试述宪法的基本价值。
围堰按材料分为()等.
要使用剪贴功能必须先进行()操作。
在输入记账凭证过程中,会计核算软件必须提供提示功能,但其中不包括的内容是()。
课堂上有的学生会开小差,这属于()。
被判处缓刑的犯罪分子在考验期内没有犯罪就视为原判刑罚已经执行完毕。
最新回复
(
0
)