学术综合英语听力原文完整版

ComprehensiveAcademicEnglishForGraduatesUnit1PresentingaSpeechRoadBuildingGoodmorning,everyone.TodayI'llbetalkingabouttherelationshipbetweenroadbuildingandthedevelopmentoftheAmericaneconomyduringthe18thcentury.About300yearsago,theUnitedStates'economywasgrowingrapidly,mainlybecauseofaboomingtradeintwoimportantagriculturalproducts:grainandcotton.GrainoutputintheeasternpartofAmericaincreasedquicklyatthattimeduetotherapidlygrowingpopulationandthelargenumberofimmigrantsfromEurope.Asaresult,thedemandforgrainalmostdoubled.Forthisreason,thetradeingrainfirstdevelopedinthispartofthecountry.Atthesametime,theroadsystemwasgraduallybuiltupinordertotransportthegrainfromtheruralareastovariouscities.Theroadbuildingclearlyhelpeddeveloptheeconomyquicklyintheseareasandinthecitiesaswell.Duringthesameperiod,farmersintheSouthcouldgetalargeamountoflaborersfromAfrica,andtheystartedtogrowcotton.Asthecottonoutputincreased,thefarmersneededtosellitinotherplaces.Asaresult,manyroadswerebuilttolinktheruralareastothecities.Atfirst,thistradeofgrainandcottontookplacealongthecoast,ornearriversandlakes.Ittookplacetherebecauseitwaseasyandcheaptotransportgoodsfromoneplacetoanother.Before1700,itwasveryexpensivetomovethegoodsbyroad.So,farmershadtorelymainlyonriverstomovetheircropstomarkets.Atthattime,therewasonlyonecontinuousroadthatexistedintheUS.Itranfromnorthtosouthalongcountryroads,whichwerelinkedtogethertomakeonelongroad.Withinashorttime,thefirsteast-to-westroadswerebuilt.Theywerecalledturnpikes.Privatecompaniesbuilttheseroadsandcollectedfeesfromallvehiclesthattraveledonthem.Eventually,becauseoftheboomingtradeofgrainandcotton,anetworkofroadwayswascompletedthatconnectedsomemajorcitiesandtowns.Althoughtravelingwasstillcostlyforfarmers,theysoonpreferredtomovetheircropstocitiesandotherareasonroadwaysratherthanbyboatbecauseitwasfasterandmoreconvenient.SoherewecanseearatherclearpictureofroadbuildingintheUnitedStatesanditsimpactoneconomicdevelopmentduringthatperiod.TheMississippiRiverinAmericaGoodafternoon.Todaywe’regoingtotalkabouttheMississippiRiver.TheMississippiRiveristhelargestriveroftheNorthAmerica.Itsmajortributariesdrainanareaofapproximately3,000,000squarekilometers,oraboutone-eighthoftheentirecontinent.TheMississippiRiverliesentirelyintheUnitedStates.FromitssourceatLakeItascainMinnesota,itflowsfromtheNorthalmostduesouthacrossthecontinentalinterior,collectingthewatersofitsmajortributaries,downtotheGulfofMexico.TheComprehensiveAcademicEnglishForGraduatesMightyMississippi,asitisaffectionatelyknown,flowsatotaldistanceabout4,000kilometersfromitssource.Withitstributaries,theMississippidrainsallorpartof31U.S.statesandtwoCanadianprovinces.Aseveryoneknows,inthepasttheriverwasthemostimportantwayoftransportinggoodsfromtheNorthtotheSouth,orfromtheSouthtotheNorthintheUnitedStates.TheMississippiRiverisalsoariverthatcansometimesgetoutofcontrolandcauseseriousfloodinginsummer.Nowadaysengineersusefourdifferentmethodstocontrolthefloodwatersoftheriver.Thesefourwaysare:floodways,dams,leveesandreservoirs.I'lldiscusseachofthesehere.FloodwaysarethefirstwayofcontrollingthefloodwatersoftheMississippiRiver.Floodwaysareemptychannelsreadytoholdwaterfromtheriver.WhentheMississippiRiveristoohigh,thefloodwaysareopenedandsomeofthewatercanflowintothefloodways.ThereareseveralfloodwaysalongthelowerMississippiRiver,whichhelppreventfloodingeffectively.ThesecondwayofcontrollingthefloodwatersoftheMississippiRiveriswithdams.Damsarewallsthatarebuiltacrossarivertocontrolthewater.Therearemorethan30damsontheMississippiRiver.Damscontrolthewaterbyholdingthewaterbehindthemuntiladecisionismadetoreleaseit.LeveesareathirdwayofcontrollingthefloodwatersoftheMississippiRiver.Leveesareearthenwallsbuiltalongsideariver.Theyholdthewaterintheriverandkeepitfromcoveringthelandbesidetheriver.Therearemorethan2,000milesofleveesalongtheMississippiRiver.Inthe19thand20thcenturies,severalreservoirswerebuiltalongtheMississippiRivertoharnessthewater.Theyhavetwofunctions.Oneistoholdwater,andtheotheristogenerateelectricitythroughhydroelectricpowerstations.Sincethe20thcentury,nohugefloodhasbrokenoutoftheMississippiRiver.Unit2EnergyConservationAnEyewitnesstoChangesinChina(Y:YangRui,anchorofDialogue,CCTV-9R:SidneyRittenberg,presidentofRittenbergAssociates,Incorporated.)Y:Mr.Rittenberg,youareasuccessfulbusinessmanandalsoabignametotheChineseduetoyourcloseassociationwiththefirstgenerationofthePRCleaders.HowdoyoulookattheimpactthatthatexperiencehashadonyourcurrentperceptionofChina'sreformanddevelopment?R:IfeelinmyheartthatwhatI’mdoingtodayisacontinuationofwhatIwastryingtodointhethatis,Ihadthisambition,thisdream,fromthetimethatIbeganstudyingChineseatStanfordUniversityin1943，IhadthisdreamofworkingtobuildbridgesbetweenChinesepeopleandAmericanpeople,andtohelpthemunderstandeachotherandcooperatetogether.AndItriedtodothatinthepast,workinginChinainMao’sComprehensiveAcademicEnglishForGraduatesday.Andthat'sexactlywhatI'mtryingtodotoday.IreallythinkthatwhatI'mdoingtodayismoreeffectivethanwhatIwasabletodointhepast.Y:Atthattimeman