托福作文写作范文详解anufactu.docx

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1、托福作文写作范文详解ReadingCarmanufacturersandgovernmentshavebeeneagerlyseekingareplacementfortheautomobilesmainsourceofpower,theinternal-combustionengine.Byfarthemostpromisingalternativesourceofenergyforcarsisthehydrogen-basedfuelcellengine,whichuseshydrogentocreateelectricitythat,inturnzpowersthecar.Fuel-ce

2、llengineshaveseveraladvantagesoverinternal-combustionenginesandwillprobablysoonreplacethem.Oneofthemainproblemswiththeinternal-combustionengineisthatitreliesonpetroleum,eitherintheformofgasolineordieselfuel.Petroleumisafiniteresource;someday,wewillrunoutofoil.Thehydrogenneededforfuel-cellenginescann

3、oteasilybedepleted.Hydrogencanbederivedfromvariousplentifulsources,includingnaturalgasandevenwater.Thefactthatfuel-cellenginesutilizeeasilyavailable,renewableresourcesmakesthemparticularlyattractive.Secondzhydrogen-basedfuelcellsareattractivebecausetheywillsolvemanyoftheworldspollutionproblems.Anuna

4、voidableby-productofburningoiliscarbondioxidezandcarbondioxideharmstheenvironmentOntheotherhand,theonlybyproductoffuel-cellenginesiswater.Third,fuel-cellengineswillsoonbeeconomicallycompetitivebecausepeoplewillspendlessmoneytooperateafuel-cellenginethantheywilltooperateaninternal-combustionengine.Th

5、isistrueforonesimplereason:afuel-cellautomobileisnearlytwiceasefficientinusingitsfuelasanautomobilepoweredbyaninternal-combustionengineis.Inotherwords,thefuel-cellpoweredcarrequiresonlyhalfthefuelenergythattheinternalcombustionpoweredcardoestogothesamedistance.ListeningProfessor:Thereadingiscorrecti

6、npointingouttheproblemsassociatedwithoil-poweredcars.Yeszoilisafiniteresource,andyes,burningoilharmstheenvironment.Howeverzthereadingiswaytoooptimisticinitsassessmentofhydrogen-basedfuel-cellengines.Hydrogenisnotthesolutiontotheseproblems.Firstzhydrogenisnotaseasilyavailableasthepassageindicates.Alt

7、houghitspresentincommonsubstanceslikewater,itsnotdirectlyuseableinthatform.Forusingafuel-cellengine,hydrogenmustfirstbeobtainedinapureliquidstate.Thispureliquidhydrogenisahighlyartificialsubstance.Itstechnologicallyverydifficulttoproduceandstoreliquidhydrogen.Forexample,itmustbekeptveryverycoldatmin

8、us253degreesCelsius.Imaginetheelaboratecoolingtechnologythatsrequiredforthat!Sohydrogenisnotsuchapracticalandeasilyavailablesubstance,isit?Second,usinghydrogenwouldnotsolvethepollutionproblemsassociatedwithcars.Why?Producingpurehydrogencreatesalotofpollution.Togetpurehydrogenfromwaterornaturalgaszyo

9、uhavetouseapurificationprocessthatrequireslotsofenergythatsobtainedbyburningcoaloroil.Andburningcoalandoilcreateslotsofpollution.Soalthoughthecarswouldnotpollute,thefactoriesthatgeneratedthehydrogenforthecarswouldpollute.Thirdztherewontnecessarilybeanycostsavingswhenyouconsiderhowexpensiveitistomanu

10、facturethefuel-cellengine.Thatsbecausefuel-cellenginesrequirecomponentsmadeofplatinum,averyrareandexpensivemetal.Withouttheplatinumcomponentsintheengine,thehydrogendoesntundergothechemicalreactionthatproducestheelectricitytopowertheautomobile.Alltheeffortstoreplaceplatinumwithacheapermaterialhavesof

11、arbeenunsuccessful.阅读听力要点概括ReadingPassageMainpoints:Fuel-cellhaveseveraladvantagesoverinternalcombustionengines.Subpoint1:Internal-combustionreliesonpetroleumandHydrogeniscleanandrenewable.Subpoint2:Fullcellscansolvepollutionproblems.Subpoint3:Full-cellsooncanbeeconomicallycompetitive.LectureAttitud

12、e:Ristoooptimistic.(Hydrogen-basedfull-cellisnotthesolution.)SubPoint1:Hydrogennoteasilyavailable.(Needinapureliquidstate,needverycoldtemperature.)SubPoint2:Hydrogendoesnotsolvethepollution.(Producingcreatesalotofpollution,Burningcoaloroil.)SubPoint3:Nocostsavingsinceexpensivetomanufacture.(Requirep

13、latinum,expensive.)范文逐段贯析Paragraph1Thelecturerpointsoutseveralproblemswiththeuseofhydrogen-basedfuel-cellengineswhichsupportherclaimthatsubstitutingthemforinternal-combustionenginesistechnologicallyunfeasible,environmentallyunfriendly,andeconomicallyunviable.此段功能：(Listeningpassage后文提到用L代替)(Readingpa

14、ssage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。Paragraph2Firstzthelecturerstatesthatitisimpracticaltoreplaceinternalcombustionengineswithfuel-cellenginesbecauseusingthelatterrequireshydrogeninapureliquidformzwhichistechnolog

15、icallychallengingtobothobtainandstore.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

16、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