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
36
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://jikaoti.com/ti/y7pRFFFM
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
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
随机试题
扮演角色是依据_______派生的,它是利用演戏和想象创造情景,以启发学员对自己及他人行为、信念、价值的认识。
团队的基本特征有哪些?
JohnPaulJoneswasoneofthefoundersoftheUnitedStatesNavy.DuringtheRevolution,thecoloniesweredesperate.Theyneed
有可能使血液黏稠度增加的先天性心脏病是
输油管直径为150mm,流量为16.3m3/h,油的运动黏滞系数为0.2cm2/s,则1000m管道的沿程损失为()。
《进出口关税条例》规定,有下列()情形之一的,进出口货物的收发货人或者他们的代理人,可以在1年内向海关申请退税。
以下事项属于注册会计师采用的测试内部控制的程序有()
新航路开辟后,首先沦为殖民地的亚洲国家是()。
尽管每年都会有一些戏曲节、戏曲汇演、戏曲评奖、送戏下乡之类的看起来十分热闹的活动,经各路媒体的卖力宣传倒也颇能造出一派红红火火的声势,但戏曲在当今社会文化生活中的尴尬生存却是一个无须争辩的现实。可以想象,如果失去政府在人力、财力、舆论等诸多方面的行政支持和
A.术后48~72小时B.术后8天C.术后20天D.术后1~2个月E.术后5~6个月皮管形成后一般在术后多少时间行皮管转移()。
最新回复
(
0
)