雅思阅读模拟试题和答案Word文件下载.docx
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雅思阅读模拟试题和答案Word文件下载.docx
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坚持每日一练,考场上就是这么自信。
带来今日每日晨读之"
Timetocoolit"
文章摘自经济学人(TheEconomist),所有雅思阅读方法技巧都需要反复做题去巩固,自己不足的地方也只有通过做题才能显现。
练习也是有技巧的,不能盲目瞎做。
把每一次阅读练习都当做考试,时间一个小时,三篇阅读,没有手机,没有字典,没有参考资料,没有笔记。
只有这样,在考场上才有可能在50分钟内做完题目(十分钟的誊写答案以及检查时间)。
1.雅思阅读材料
1REFRIGERATORSaretheepitomeofclunkytechnology:
solid,reliableandjustalittlebitdull.Theyhavenotchangedmuchoverthepastcentury,butthentheyhavenotneededto.Theyarebasedonarobustand
effective
idea--drawheatfromthethingyouwanttocoolbyevaporatingaliquidnexttoit,andthendumpthatheatbypumpingthevapourelsewhereandcondensingit.Thismethodofpumpingheatfromoneplacetoanotherservedmankindwellwhenrefrigerators'
mainjobswerepreservingfoodand,asairconditioners,coolingbuildings.Today'
shigh-techworld,however,demandshigh-techrefrigeration.Heatpumpsarenolongeruptothejob.Thesearchisonforsomethingtoreplacethem.
2Onesetofcandidatesareknownasparaelectricmaterials.Theseactlikebatterieswhentheyundergoatemperaturechange:
attachelectrodestothemandtheygenerateacurrent.Thiseffectisusedininfra-redcameras.Anarrayoftinypiecesofparaelectricmaterialcansensetheheatradiatedby,forexample,aperson,andthepatternofthearray'
selectricaloutputscanthenbeusedtoconstructanimage.Butuntilrecentlynoonehadbotheredmuchwiththeinverseofthisprocess.Thatinverseexists,however.Applyanappropriatecurrenttoaparaelectricmaterialanditwillcooldown.
3SomeonewhoislookingatthisinverseeffectisAlexMischenko,ofCambridgeUniversity.Usingcommerciallyavailableparaelectricfilm,heandhiscolleagueshavegeneratedtemperaturedropsfivetimesbiggerthananypreviouslyrecorded.Thatmaybeenoughtochangethephenomenonfromalaboratorycuriositytosomethingwithcommercialapplications.
4Astowhatthoseapplicationsmightbe,DrMischenkoisstillalittlehazy.Hehas,nevertheless,setupacompanytopursuethem.Heforeseesputtinghisdiscoverytouseinmore
efficient
domesticfridgesandairconditioners.Therealmoney,though,maybeincoolingcomputers.
5Gadgetscontainingmicroprocessorshavebeengettinghotterforalongtime.OneconsequenceofMoore'
sLaw,whichdescribesthedoublingofthenumberoftransistorsonachipevery18months,isthattheamountofheatproduceddoublesaswell.Infact,itmorethandoubles,becausebesidesincreasinginnumber,thecomponentsaregettingfaster.Heatisreleasedeverytimealogicaloperationisperformedinsideamicroprocessor,sothefastertheprocessoris,themoreheatitgenerates.Doublingthefrequencyquadruplestheheatoutput.Andthefrequencyhasdoubledalot.ThefirstPentiumchipssoldbyDrMoore'
scompany,Intel,in1993,ranat60mcyclesasecond.ThePentium4--thelast"
single-core"
desktopprocessor--clockedup3.2billioncyclesasecond.
6Disposingofthisheatisabigobstructiontofurtherminiaturisationandhigherspeeds.Theinnardsofadesktopcomputercommonlyhit80℃.At85℃,theystopworking.Tweakingtheprocessor'
sheatsinks(copperoraluminiumboxesdesignedtoradiateheataway)hasreacheditslimit.Sohastweakingthefansthatcirculateairoverthoseheatsinks.Andtheideaofshiftingfromsingle-coreprocessorstosystemsthatdividedprocessingpowerbetweenfirsttwo,andthenfour,subunits,inordertospreadthethermalload,alsoseemstohavetheendoftheroadinsight.
7Onewayoutofthismaybeasecondcuriousphysicalphenomenon,thethermoelectriceffect.Likeparaelectricmaterials,thisgenerateselectricityfromaheatsourceandproducescoolingfromanelectricalsource.Unlikeparaelectrics,asignificantbodyofresearchersisalreadyworkingonit.
8Thetricktoagoodthermoelectricmaterialisacrystalstructureinwhichelectronscanflowfreely,butthepathofphonons--heat-carryingvibrationsthatarelargerthanelectrons--isconstantlyinterrupted.Inpractice,thistrickishardtopulloff,andthermoelectricmaterialsarethuslessefficientthanparaelectricones(or,atleast,thanthoseexaminedbyDrMischenko).Nevertheless,RamaVenkatasubramanian,ofNextremeThermalSolutionsinNorthCarolina,claimstohavemadethermoelectricrefrigeratorsthatcansitonthebackofcomputerchipsandcoolhotspotsby10℃.AliShakouri,oftheUniversityofCalifornia,SantaCruz,sayshisareevensmaller--sosmallthattheycangoinsidethechip.
9Thelastwordincomputercooling,though,maygotoasystemevenlesstechythanaheatpump--aminiatureversionofacarradiator.LastyearApplelaunchedapersonalcomputerthatiscooledbyliquidthatispumpedthroughlittlechannelsintheprocessor,andthencetoaradiator,whereitgivesupitsheattoth
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