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《新g機(jī)經(jīng)中的老g原題和其他長(zhǎng)篇機(jī)經(jīng) gre大牛經(jīng)驗(yàn)談》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在教育資源-天天文庫。
1、1.有篇長(zhǎng)閱讀?老G改的那個(gè)污染汽油乙醇替代石油燃料環(huán)保的那篇1993年04AAlthough,recentyearshaveseensubstantialreductionsinnoxiouspollutantsfromindividualmotorvehicles,thenumberofsuchvehicleshasbeensteadilyincreasingconsequently,morethan100citiesintheUnitedStatesstillhavelevelsofcarbonmonoxi
2、de,particulatematter(particulatematter:顆粒物質(zhì)),andozone(generatedbyphotochemicalreactionswithhydrocarbons(hydrocarbon：n.烴,碳?xì)浠衔?fromvehicleexhaust)thatexceedlegallyestablishedlimits.Thereisagrowingrealizationthattheonlyeffectivewaytoachievefurtherreductionsinve
3、hicleemissions—shortof(shortof:adv.缺乏,只要沒有)amassiveshiftawayfrom(awayfrom:遠(yuǎn)離)theprivateautomobile—istoreplaceconventionaldieselfuelandgasolinewithcleaner-burningfuelssuchascompressednaturalgas,liquefiedpetroleumgas(liquefiedpetroleumgas:n.液化石油氣acompressedgast
4、hatconsistsofflammablehydrocarbons(aspropaneandbutane)andisusedespeciallyasfuelorasrawmaterialforchemicalsynthesis),ethanol,ormethanol.Allofthesealternativesarecarbon-basedfuelswhosemoleculesaresmallerandsimplerthanthoseofgasoline.Thesemoleculesburnmorecleanl
5、ythangasoline,inpartbecausetheyhavefewer,ifand,carbon-carbonbonds,andthehydrocarbonstheydoemitarelesslikelytogenerateozone.Thecombustionoflargermolecules,whichhavemultiplecarbon-carbonbonds,involvesamorecomplexseriesofreactions.Thesereactionsincreasetheprobab
6、ilityofincompletecombustionandaremorelikelytoreleaseuncombustedandphotochemicallyactivehydrocarboncompoundsintotheatmosphere.Ontheotherhand,alternativefuelsdohavedrawbacks.Compressednaturalgaswouldrequirethatvehicleshaveasetofheavyfueltanks—aseriousliabilityi
7、ntermsofperformanceandfuelefficiency—andliquefiedpetroleumgasfacesfundamentallimitsonsupply.Ethanolandmethanol,ontheotherhand,haveimportantadvantagesoverothercarbon-basedalternativefuels:theyhaveahigherenergycontent(energycontent:能含量；內(nèi)能)pervolumeandwouldrequi
8、reminimalchangesintheexistingnetworkfordistributingmotorfuel.Ethanoliscommonlyusedasagasolinesupplement,butitiscurrentlyabouttwiceasexpensiveasmethanol,thelowcostofwhichisoneofitsattracti
