托福作文写作范文详解anufactu

托福作文写作范文详解ReadingCarmanufacturersandgovernmentshavebeeneagerlyseekingareplacementfortheautomobile'smainsourceofpower,theinternal‐combustionengine.Byfarthemostpromisingalternativesourceofenergyforcarsisthehydrogen‐basedfuel‐cellengine,whichuseshydrogentocreateelectricitythat,inturn,powersthecar.Fuel‐cellengineshaveseveraladvantagesoverinternal‐combustionenginesandwillprobablysoonreplacethem.Oneofthemainproblemswiththeinternal‐combustionengineisthatitreliesonpetroleum,eitherintheformofgasolineordieselfuel.Petroleumisafiniteresource;someday,wewillrunoutofoil.Thehydrogenneededforfuel‐cellenginescannoteasilybedepleted.Hydrogencanbederivedfromvariousplentifulsources,includingnaturalgasandevenwater.Thefactthatfuel‐cellenginesutilizeeasilyavailable,renewableresourcesmakesthemparticularlyattractive.Second,hydrogen‐basedfuelcellsareattractivebecausetheywillsolvemanyoftheworld'spollutionproblems.Anunavoidableby‐productofburningoiliscarbondioxide,andcarbondioxideharmstheenvironment.Ontheotherhand,theonlybyproductoffuel‐cellenginesiswater.Third,fuel‐cellengineswillsoonbeeconomicallycompetitivebecausepeoplewillspendlessmoneytooperateafuel‐cellenginethantheywilltooperateaninternal‐combustionengine.Thisistrueforonesimplereason:afuel‐cellautomobileisnearlytwiceasefficientinusingitsfuelasanautomobilepoweredbyaninternal‐combustionengineis.Inotherwords,thefuel‐cellpoweredcarrequiresonlyhalfthefuelenergythattheinternal‐combustionpoweredcardoestogothesamedistance.ListeningProfessor:Thereadingiscorrectinpointingouttheproblemsassociatedwithoil‐poweredcars.Yes,oilisafiniteresource,andyes,burningoilharmstheenvironment.However,thereadingiswaytoooptimisticinitsassessmentofhydrogen‐basedfuel‐cellengines.Hydrogenisnotthesolutiontotheseproblems.First,hydrogenisnotaseasilyavailableasthepassageindicates.Althoughit'spresentincommonsubstanceslikewater,it'snotdirectlyuseableinthatform.Forusingafuel‐cellengine,hydrogenmustfirstbeobtainedinapureliquidstate.Thispureliquidhydrogenisahighlyartificialsubstance.It'stechnologicallyverydifficulttoproduceandstoreliquidhydrogen.Forexample,itmustbekeptveryverycoldatminus253degreesCelsius.Imaginetheelaboratecoolingtechnologythat'srequiredforthat!Sohydrogenisnotsuchapracticalandeasilyavailablesubstance,isit?Second,usinghydrogenwouldnotsolvethepollutionproblemsassociatedwithcars.Why?Producingpurehydrogencreatesalotofpollution.Togetpurehydrogenfromwaterornaturalgas,youhavetouseapurificationprocessthatrequireslotsofenergythat'sobtainedbyburningcoaloroil.Andburningcoalandoilcreateslotsofpollution.Soalthoughthecarswouldnotpollute,thefactoriesthatgeneratedthehydrogenforthecarswouldpollute.Third,therewon'tnecessarilybeanycostsavingswhenyouconsiderhowexpensiveitistomanufacturethefuel‐cellengine.That'sbecausefuel‐cellenginesrequirecomponentsmadeofplatinum,averyrareandexpensivemetal.Withouttheplatinumcomponentsintheengine,thehydrogendoesn'tundergothechemicalreactionthatproducestheelectricitytopowertheautomobile.Alltheeffortstoreplaceplatinumwithacheapermaterialhavesofarbeenunsuccessful.阅读听力要点概括ReadingPassageMainpoints:Fuel‐cellhaveseveraladvantagesoverinternal‐combustionengines.Subpoint1:Internal‐combustionreliesonpetroleumandHydrogeniscleanandrenewable.Subpoint2:Fullcellscansolvepollutionproblems.Subpoint3:Full‐cellsooncanbeeconomicallycompetitive.LectureAttitude:Ristoooptimistic.(Hydrogen‐basedfull‐cellisnotthesolution.)SubPoint1:Hydrogennoteasilyavailable.(Needinapureliquidstate,needverycoldtemperature.)SubPoint2:Hydrogendoesnotsolvethepollution.(Producingcreatesalotofpollution,Burningcoaloroil.)SubPoint3:Nocostsavingsinceexpensivetomanufacture.(Requireplatinum,expensive.)范文逐段赏析Paragraph1Thelecturerpointsoutseveralproblemswiththeuseofhydrogen‐basedfuel‐cellengineswhichsupportherclaimthatsubstitutingthemforinternal‐combustionenginesistechnologicallyunfeasible,environmentallyunfriendly,andeconomicallyunviable.此段功能：(Listeningpassage后文提到用L代替)(Readingpassage后文用R代替)开头段作者总结到L指出(氢燃料电池引擎)替换(内燃机引擎)科技上不能实现，环境上不友好，而且经济上不合适。此段结构：这一句话，巧妙的用L的反对逻辑，引出了论证问题的三个方面。把总结L，总结R和表明逻辑轻巧的锁在了一句话里。Paragraph2First,thelecturerstatesthatitisimpracticaltoreplaceinternal‐combustionengineswithfuel‐cellenginesbecauseusingthelatterrequireshydrogeninapureliquidform,whichistechnologicallychallengingtobothobtainandstore.However,thereadingpassagearguesthatbecausehydrogencanbeextractedfrommanysourcesincludingwater,fuel‐cellenginespoweredbythisinfinitesourceofenergyareanextremelyattractivealternative.此段功能：在第一点technologyunfeasible的论证上。作者复述L觉得电池替换内燃是不现实的，因为电池需要液态氢，而液态氢非常难制取和储存。在R里，R只想到了氢气可以从很多来源从提炼比如水，所以认为燃料是无限的，这种想法很有吸引力。此段结构：此段为分总结构，作者先阐明L认为这个替换是不现实的，因为某些原因。第二句中作者复述了R本来认为的观点，作为对比。Paragraph3Second,thelecturerrefutestheclaiminthereadingthathydrogencellsareenvironmentallyfriendly.Shearguesthatalthoughenginesthatusehydrogencellsproducelesspollution,themanufacturingofhydrogencellsgenerateslargeamountsofharmfulby‐productsduetotheburningoffossilfuelsinthepurificationprocess.此段功能：在第二点environmentalunfriendly辩论上，作者直接陈述L认为R所说的电池很环保是错误的。L解释虽然电池引擎不会产生太多污染，但是制造电池引擎的提纯过程消耗了大量的化石燃料也是不环保的。此段结构：此段为总分结构。作者大略总结了一下R的观点并说L持反对意见，随后列举所有的反对R的证据。Paragraph4Third,althoughthereadingsuggeststhathydrogen‐basedenginesaremorefuel‐efficientandthuseconomicallycompetitivethaninternal‐combustionengines,thelecturerarguesthatsuchanadvantageisunderminedbythefactthatfuel‐cellenginesareextremelyexpensivetomanufacture,requiringtheaddit