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—conv
Sunlight is free, but that is no reason to waste it. Yet even the best silicon solar cells—by far the most【C1】________ sort—conv
admin
2023-04-14
100
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.
【C16】
选项
A、costly
B、lively
C、orderly
D、deadly
答案
A
解析
空格所在句为表语从句,主句的主语为“问题”,故该空格所需的词应该含有否定意义。又从本文开头所述“电池材料很便宜”可推出,Rogers博士新设计的电池应为其反义词,即“昂贵的”。故A项costly为答案。B项lively“充满活力的”和C项orderly“整齐有序的”均含有肯定意义,不符合语义。根据上下文不能确定问题是否是“致命的”,故排除D项。
转载请注明原文地址:https://www.kaotiyun.com/show/A5MD777K
0
考研英语二
相关试题推荐
ZoeBuhlerwasscheduledforanultrasoundappointmentontheSeptembermorningwhenAustralianpoliceenteredherhome.Thepre
AstudyofhowolderteenagersusesocialmediahasfoundthatFacebookis"notjustontheslide,itisbasicallydeadandburi
Sunlightisfree,butthatisnoreasontowasteit.Yeteventhebestsiliconsolarcells—byfarthemost【C1】________sort—conv
Sunlightisfree,butthatisnoreasontowasteit.Yeteventhebestsiliconsolarcells—byfarthemost【C1】________sort—conv
Sunlightisfree,butthatisnoreasontowasteit.Yeteventhebestsiliconsolarcells—byfarthemost【C1】________sort—conv
Sunlightisfree,butthatisnoreasontowasteit.Yeteventhebestsiliconsolarcells—byfarthemost【C1】________sort—conv
Sunlightisfree,butthatisnoreasontowasteit.Yeteventhebestsiliconsolarcells—byfarthemost【C1】________sort—conv
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
随机试题
在Windows7中,对文件和文件夹的管理是通过“计算机”和“________”来实现的。
EPSP与IPSP共同的特征为
乙脑抢救必须闯过的“三关”是
A、煨用B、蜜炙C、炒炭D、醋炒E、研末用作扑粉乌梅止血、止泻宜
食管癌的早期症状是
【2013专业案例真题下午卷】某无人值班的35/10kV变电所,35kV侧采用线路变压器组接线,10kV侧采用单母线分段接线,设母联断路器:两台变压器同时运行、互为备用,当任一路电源失电或任一台变压器解列时,该路35kV断路器及10kV进线断路器跳闸,10
商业银行对项目进行财务分析,采用的基本财务报表有()。
某市区某化妆品有限公司为增值税一般纳税人,2015年11月发生以下各项业务:(1)从国外进口一批化妆品,成交价1380000元、货物运抵境内输入地点之前的运输保险费及相关费用20000元,支付货物进口后的保险费用20000元。因管理的不善的原因,在自
简述定金的效力。
TheauthorindicatesatthebeginningofthepassagethatTheimportanceofmovementinmusicisexplainedbycomparingitto
最新回复
(
0
)