Unit4-分析主谓结构

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HydroelectricPowerUnit31Content4.1IntroductiontoHydroenergy4.2Hydroelectricpowergeneration4.3Environmentalimpact4.4subject-verbStructures4.5Threegorgesdam23Hydroenergyreferstosumofthekineticenergy,potentialandpressureenergyofwater.Generalizedhydroenergyresourcesincludingriverwater,tidalenergy（潮汐能）,waveenergy(波浪能)，oceanenergyetal.

Throughhydropower,theenergyinfallingwaterisconvertedintoelectricitywithout“usingup”thewater.

Hydroelectricpower/hydropower:水力发电

4.1IntroductiontoHydroenergyHydroenergy:水能

Humansfirstlearnedtoharnessthekineticenergyinwaterbyusingwaterwheels.Awaterwheelisarevolvingwheelfittedwithblades（桨叶）,buckets（斗叶）,orvanes（叶片）.

Waterwheelsconvertthekineticenergyofflowingwatertomechanicalenergy.Waterwheel：水车Earlywaterwheelsusedmechanicalenergytogrindgrainsandtodrivemachinerysuchassawmills（锯木头）andblacksmith（打铁）equipment.TypesofWaterWheels（水车）TypesofwaterwheelsarebaseduponwherethewaterstrikesitPitchback–后流式水车Overshot–上冲式水车Undershot–下冲式水车WaterWheels:PitchbackandOvershotAsurroundstructurecouldforcethewateragainstthewheelasitfallsandincreasetheweightofthewaterinthewheel.Pitchback

（后流式水车）–waterdropsfromtopandisdeflectedbackwardstofallbacktowardsthedamOvershot

（上冲式水车）–shootsoverthetopontothewheel;theusualkindWaterWheels:Undershot（下冲式）TheundershotwheelissimplyplacedinastreamwiththebottomofthewheelpushedbythecurrentWorkswellwherethereislittledepthandnoheadInefficient,butworkswhereotherswon’tWaterwheeltechnologyadvancedovertime.Turbinesareadvanced,veryefficientwaterwheels.Turbine：涡轮机、水轮机、汽轮机Waterwheelsturnslowlycomparedwithturbines:onetofiftyrpmTurbinesrpm:revolutionsperminute转数/分10ClassificationofHydroTurbinesReactionTurbines：反击式水轮机TotallyimmersedinwaterCombiningactionofpressureenergyandkineticenergyofthewaterPropeller(桨叶式)andFrancis（混流式或法兰西式）turbinesPropellerTurbineSmallversionsofthePropellerturbinecanbeloweredintoastreambyhandtopoweraremotehomehttp://www.hitachi.co.jp/Div/hitachi/hydraulic-turbine/BULB.htm050322Ampair'sAquairUWsubmersiblepropellerturbine

30ftdiameter 0.8ftdiameterFrancisTurbineWaterflowsthroughtherunnertospintheturbine.

水流从四周径向流入转轮，然后近似轴向流出转轮，混流式水轮机结构紧凑，效率较高，能适应很宽的水头范围

03032313ImpulseTurbines：冲击式水轮机ConvertkineticenergyofwaterjethittingbucketsNopressuredropacrossturbinesImpulseTurbinesThesedoublecupscatchthewaterfromtheinputwaterjetsandreflectitformaximumthrusttospintherotorImpulseTurbinesarepopularformicroturbinesproducingenergy.http://www.hitachi.co.jp/Div/hitachi/hydraulic-turbine/others.htm050322美国的佩尔顿最早发明的水斗式水轮机。它有流线型的收缩喷嘴，能把水流能量高效率地转变为高速射流的动能。Notlongafterthediscoveryofelectricity,itwasrealizedthataturbine’smechanicalenergycouldbeusedtoactivateageneratorandproduceelectricity.Thefirsthydroelectricpowerplantwasconstructedin1882inAppleton（阿普尔顿）,Wisconsin（威斯康星州）.

Itproduced12.5kilowattsofelectricitywhichwasusedtolighttwopapermills（纸厂）andonehome.4.2Hydroelectricpowergeneration16Flowingwaterisdirectedataturbine(rememberturbinesarejustadvancedwaterwheels).Theflowingwatercausestheturbinetorotate,convertingthewater’skineticenergyintomechanicalenergy.Themechanicalenergyproducedbytheturbineisconvertedintoelectricenergyusingaturbinegenerator.Insidethegenerator,theshaftoftheturbinespinsamagnetinsidecoils（铜线圈）ofcopperwire.

Itisafactofnaturethatmovingamagnetnearaconductorcausesanelectriccurrent.

HowaHydroelectricPowerSystemWorksPotential

EnergyKinetic

EnergyElectrical

EnergyMechanicalEnergyElectricityTheamountofelectricitythatcanbegeneratedbyahydropowerplantdependsontwofactors:

flowrate

-thequantityofwaterflowinginagiventime;

head-theheightfromdamthewaterfalls.Thegreatertheflowrateandhead,themoreelectricityproduced.Howmuchelectricitycanbegeneratedbyahydroelectricpowerplant?flowrate：流量

Head：水头Whenmorewaterflowsthroughaturbine,moreelectricitycanbeproduced.Theflowratedependsonthesizeoftheriverandtheamountofwaterflowinginit.Powerproductionisconsideredtobedirectlyproportionaltoriverflow.Thatis,twiceasmuchwaterflowingwillproducetwiceasmuchelectricity.FlowRate=thequantityofwaterflowinginagiventimeThehigherthedam,thefartherthewaterfalls,producingmorehydroelectricpower.Powerproductionisalsodirectlyproportionaltohead.Thatis,waterfallingtwiceasfarwillproducetwiceasmuchelectricity.Head=theheightfromdamwaterfallsPower=theelectricpowerinkilowattsorkWHead=thedistancethewaterfalls(measuredinfeet（英尺）)Flow=theamountofwaterflowing(measuredincubicfeetpersecond orcfs)Efficiency=Howwelltheturbineandgeneratorconvertthepowerof fallingwaterintoelectricpower.Thiscanrangefrom60% (0.60)forolder,poorlymaintainedhydroplantsto90% (0.90)fornewer,wellmaintainedplants.11.8=Indexthatconvertsunitsoffeetandsecondsintokilowatts

Astandardequationforcalculatingenergyproduction:Power=(Head)x(Flow)x(Efficiency)11.8

feet：英尺

Thetwoprimarytypesofhydropowerfacilitiesaretheimpoundmentsystem

(ordam)andtherun-of-the-riversystem.TypesofHydropowerFacilitiesimpoundmentsystem：蓄水系统

run-of-the-riversystem：运行的河流系统Animpoundmentissimplyadamthatholdswaterinareservoir.Thewaterisreleasedwhenneededthroughapenstock（水渠）,todrivetheturbine.Thisillustrationshowsthepartsofastandardhydroelectricdam.Mostlarge,high-headhydropowerfacilitiesuseimpoundments.ImpoundmentSystemArun-of-the-river

systemusestheriver’snaturalflowandrequireslittleornoimpoundment.Itmayinvolveadiversionofthestreamthroughacanal（管道）orpenstock（水渠）,anditmayinvolveplacementofaturbinerightinthestreamchannel.Run-of-the-riversystemsareoftenlow-head.Run-of-the-RiverHydropowerSystem运行的河流系统发电系统Therearelargepowerplantsthatproducehundredsofmegawattsofelectricityandservethousandsoffamilies.Therearealsosmallandmicrohydropowerplantsthatindividualscanoperatefortheirownenergyneeds.HydropowerPlantsAlsoVaryinSizeAlargehydropowerfacilityhasthecapacitytoproducemorethan30,000kilowatts(kW)ofelectricity.

ThemajorityofhydropowersystemsintheU.S.fitinthiscategory.Largehydropowersystemstypicallyrequireadam.LargeHydropowerSmallHydropowerSmallhydropowerfacilitiescanproduce100–30,000kilowatts(kW)ofelectricity.Smallhydropowerfacilitiesmayinvolveasmalldam,orbeadiversionofthemainstream,orbearun-of-the-riversystem.Microhydropowerplantshavethecapacitytoproduce100kilowatts(kW)orless.Micro-hydrofacilitiestypicallyusearun-of-the-riversystem.MicroHydropower4.3EnvironmentalConsiderationsHigh-headhydropowersystemscanproduceatremendousamountofpower.However,largehydropowerfacilities,whileessentiallypollution-freetooperate,stillhaveundesirableeffectsontheenvironment.Installationofnewlargehydropowerprojectstodayisverycontroversial（有争议的）becauseoftheirnegativeenvironmentalimpacts.Theseinclude:upstreamfloodingdecliningfishpopulationsdecreasedwaterqualityandflowreducedqualityofupstreamanddownstreamenvironmentsScientiststodayareseekingwaystodevelophydropowerplantsthathavelessimpactontheenvironment.Onewayisthroughlow-headhydropower.Low-headhydropowerprojectsareusuallylowimpactaswell—thatis,theyhavefewernegativeeffectsontheenvironment.Low-headandLowImpactHydropower4.3subject-verbStructures在英语阅读中，句子主谓结构的识别是最基本的阅读技巧：

句子的中心内容句子的主干识别主谓结构是分析句子的第一步。

英语的主谓次序：主语在前，谓语在后。主语和谓语之间常插入定语和状语。33(1)Thepotentialenergypossessedbywateristheproductofitsweightandausabledifferenceinelevationcalledhead.(2)Thepowerplant,withatotalinstalledcapacityof1800MW,

isapuredaily-regulatedpumpedstoragepowerplant.(3)Thewaterpossessinglargeenergystrikestherunnerandcausesittorotate.Economiesofscaleandthegreatergeneratingefficiencyachievedashighersteamtemperaturesandpressureswereattainedbothreinforcedthistendency.34Economiesofscaleandthegreatergeneratingefficiencyachievedashighersteamtemperaturesandpressureswereattained

bothreinforcedthistendency.大多情况下，主语相对比较容易确定，但识别主谓结构的关键是找谓语动词。有时主语与谓语之间插入的内容较多，正确找出谓语就会比较困难。主语谓语后置定语从句谓语获得更高的蒸汽温度和压强可以得到更高的发电效率，规模经济和更高的发电效率加强了这种（电力增长的）趋势。35Theexpandinggascomingfromtheturbineandmovingalongthejetnozzles（喷嘴）

continuestoexpandandacceleratetoformahighvelocity.英语主谓结构这一问题可以从英语名词的数、基本的英语主谓结构类型以及定语从句主谓结构的识别等三方面来判断。（1）英语名词的数:谓语动词根据主语的单复数的不同发生单复数的变化。-s结尾的名词不一定是复数(如一些表示学科的名词、专有名词)Electronics(电子学)isthebasisofallcommunicationssystem.Mechanics(力学)hasdevelopedalotinmoderntimes

又如：thermodynamics，physics,optics.36Generalmotors(通用汽车公司)producesmanydifferenttypesofcars.（2）基本的英语主谓结构类型

单个名词+谓语动词并列名词+谓语动词名词+后置定语/状语+谓语动词谓语动词+名词（倒装句）另外，还有非谓语动词或从句充当主语

不定式（短语）+谓语动词动名词（短语）+谓语动词主语从句+谓语动词37单个名词+谓语动词The20thcenturyhaswitnessedabigexpansionofelectricalpowergenerationanddistribution。并列名词+谓语动词并列名词有三类：and、or单个并列连接词连接起来作主语的名词。Notonly…butalso,neither…nor,either…or组合并列连接词连接起来作主语的名词。Aswellas,alongwith,togetherwith,inadditionto等介词短语连接起来的名词。Therotorshaftand

thefieldstructurearemadeofasolidalloysteel（固体合金钢）forging（锻造）inwhichslots（槽）aremachinedtoacceptthefieldcoils（励磁线圈）,asshowninFigure2.And用复数，or由后面的名词决定。Notonlycoalandoilbutalsofallingwaterisbeingusedtoproduceelectircity.Neither….nor,either…or…由后面的名词决定。并列名词+谓语动词39Thevariousmanifestations（表现形式）

ofelectricityaretheresultoftheaccumulationormotionofelectrons.名词+后置定语/状语+谓语动词Themachineaswellasitsauxiliarydevicesisimported.Aswellas,alongwith由后面的名词决定。40Thehydroelectricpowerusingafallofwatertodrivewaterturbines

hasbeendevelopedtogenerateelectricity.Anotherimportantfactortobetakenintoconsiderationisthatcurrentstrengthisequalatcertainpointsinaseriescircuit.41Thereare

fourwaysfortransmittingpowerfromtheelectricmotortothespindle.谓语动词+名词are是谓语动词，are提示主语是后面的复数名词ways.Touseanyofthesefuelsneedsourseriousconsideration.不定式（短语）+谓语动词主语是不定式短语，而不是fuels.Generatingcurrentatalowerfrequencyandthenboostingittoahigherfrequencyaremoreefficient.动名词（短语）+谓语动词主语是两个并列的动名词42Whetherthisunitwilloperateefficientlyremainstobeseen.Whatpotentialenergyandkineticenergymeansandhowweexplainthesetwoterms

havebeenmentionedinthisarticle.（3）定语从句的主谓结构的判别

由于定语从句的主语可能是由that或which等连接词来充当，that或which到底指代什么，有时需要通过主谓结构的分析才能搞清。主语从句+谓语动词Thisprocessenhancestheoverallthermalefficiencyofenergyconversiontoabout50percent-asopposedtoconventionalprocesses,whichhaveanefficiencyofabout36to38percent.Thisprocessenhances

theoverallthermalefficiencyofenergyconversiontoabout50percent-asopposedtoconventionalprocesses,whichhaveanefficiencyofabout36to38percent.43高压输电线路通常是由铜、铝或包铜的线组成，这些线通过一连串瓷制绝缘体，悬挂于高高的钢铁格子塔架上。Thelineofhigh-voltagetransmissionsystemsareusuallycomposedofwiresofcopper,aluminum,orcopper-clad,whicharesuspended（悬浮于）fromtalllatticeworktowersofsteelbystringsofporcelaininsulators（瓷制绝缘体）.Thelineofhigh-voltagetransmissionsystemsareusuallycomposedofwiresofcopper,aluminum,orcopper-clad,whicharesuspended（悬浮于）fromtalllatticeworktowe