Unit4-分析主謂結(jié)構(gòu)

/images/toptitle.png

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

Throughhydropower,theenergyinfallingwaterisconvertedintoelectricitywithout“usingup”thewater.

Hydroelectricpower/hydropower:水力發(fā)電

4.1IntroductiontoHydroenergyHydroenergy:水能

Humansfirstlearnedtoharnessthekineticenergyinwaterbyusingwaterwheels.Awaterwheelisarevolvingwheelfittedwithblades（槳葉）,buckets（斗葉）,orvanes（葉片）.

Waterwheelsconvertthekineticenergyofflowingwatertomechanicalenergy.Waterwheel：水車Earlywaterwheelsusedmechanicalenergytogrindgrainsandtodrivemachinerysuchassawmills（鋸木頭）andblacksmith（打鐵）equipment.TypesofWaterWheels（水車）TypesofwaterwheelsarebaseduponwherethewaterstrikesitPitchback–后流式水車Overshot–上沖式水車Undershot–下沖式水車WaterWheels:PitchbackandOvershotAsurroundstructurecouldforcethewateragainstthewheelasitfallsandincreasetheweightofthewaterinthewheel.Pitchback

（后流式水車）–waterdropsfromtopandisdeflectedbackwardstofallbacktowardsthedamOvershot

（上沖式水車）–shootsoverthetopontothewheel;theusualkindWaterWheels:Undershot（下沖式）TheundershotwheelissimplyplacedinastreamwiththebottomofthewheelpushedbythecurrentWorkswellwherethereislittledepthandnoheadInefficient,butworkswhereotherswon’tWaterwheeltechnologyadvancedovertime.Turbinesareadvanced,veryefficientwaterwheels.Turbine：渦輪機、水輪機、汽輪機Waterwheelsturnslowlycomparedwithturbines:onetofiftyrpmTurbinesrpm:revolutionsperminute轉(zhuǎn)數(shù)/分10ClassificationofHydroTurbinesReactionTurbines：反擊式水輪機TotallyimmersedinwaterCombiningactionofpressureenergyandkineticenergyofthewaterPropeller(槳葉式)andFrancis（混流式或法蘭西式）turbinesPropellerTurbineSmallversionsofthePropellerturbinecanbeloweredintoastreambyhandtopoweraremotehomehttp://www.hitachi.co.jp/Div/hitachi/hydraulic-turbine/BULB.htm050322Ampair'sAquairUWsubmersiblepropellerturbine

30ftdiameter 0.8ftdiameterFrancisTurbineWaterflowsthroughtherunnertospintheturbine.

水流從四周徑向流入轉(zhuǎn)輪，然后近似軸向流出轉(zhuǎn)輪，混流式水輪機結(jié)構(gòu)緊湊，效率較高，能適應(yīng)很寬的水頭范圍

03032313ImpulseTurbines：沖擊式水輪機ConvertkineticenergyofwaterjethittingbucketsNopressuredropacrossturbinesImpulseTurbinesThesedoublecupscatchthewaterfromtheinputwaterjetsandreflectitformaximumthrusttospintherotorImpulseTurbinesarepopularformicroturbinesproducingenergy.http://www.hitachi.co.jp/Div/hitachi/hydraulic-turbine/others.htm050322美國的佩爾頓最早發(fā)明的水斗式水輪機。它有流線型的收縮噴嘴，能把水流能量高效率地轉(zhuǎn)變?yōu)楦咚偕淞鞯膭幽?。Notlongafterthediscoveryofelectricity,itwasrealizedthataturbine’smechanicalenergycouldbeusedtoactivateageneratorandproduceelectricity.Thefirsthydroelectricpowerplantwasconstructedin1882inAppleton（阿普爾頓）,Wisconsin（威斯康星州）.

Itproduced12.5kilowattsofelectricitywhichwasusedtolighttwopapermills（紙廠）andonehome.4.2Hydroelectricpowergeneration16Flowingwaterisdirectedataturbine(rememberturbinesarejustadvancedwaterwheels).Theflowingwatercausestheturbinetorotate,convertingthewater’skineticenergyintomechanicalenergy.Themechanicalenergyproducedbytheturbineisconvertedintoelectricenergyusingaturbinegenerator.Insidethegenerator,theshaftoftheturbinespinsamagnetinsidecoils（銅線圈）ofcopperwire.

Itisafactofnaturethatmovingamagnetnearaconductorcausesanelectriccurrent.

HowaHydroelectricPowerSystemWorksPotential

EnergyKinetic

EnergyElectrical

EnergyMechanicalEnergyElectricityTheamountofelectricitythatcanbegeneratedbyahydropowerplantdependsontwofactors:

flowrate

-thequantityofwaterflowinginagiventime;

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

Head：水頭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：蓄水系統(tǒng)

run-of-the-riversystem：運行的河流系統(tǒng)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運行的河流系統(tǒng)發(fā)電系統(tǒng)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（有爭議的）becauseoftheirnegativeenvironmentalimpacts.Theseinclude:upstreamfloodingdecliningfishpopulationsdecreasedwaterqualityandflowreducedqualityofupstreamanddownstreamenvironmentsScientiststodayareseekingwaystodevelophydropowerplantsthathavelessimpactontheenvironment.Onewayisthroughlow-headhydropower.Low-headhydropowerprojectsareusuallylowimpactaswell—thatis,theyhavefewernegativeeffectsontheenvironment.Low-headandLowImpactHydropower4.3subject-verbStructures在英語閱讀中，句子主謂結(jié)構(gòu)的識別是最基本的閱讀技巧：

句子的中心內(nèi)容句子的主干識別主謂結(jié)構(gòu)是分析句子的第一步。

英語的主謂次序：主語在前，謂語在后。主語和謂語之間常插入定語和狀語。33(1)Thepotentialenergypossessedbywateristheproductofitsweightandausabledifferenceinelevationcalledhead.(2)Thepowerplant,withatotalinstalledcapacityof1800MW,

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

bothreinforcedthistendency.大多情況下，主語相對比較容易確定，但識別主謂結(jié)構(gòu)的關(guān)鍵是找謂語動詞。有時主語與謂語之間插入的內(nèi)容較多，正確找出謂語就會比較困難。主語謂語后置定語從句謂語獲得更高的蒸汽溫度和壓強可以得到更高的發(fā)電效率，規(guī)模經(jīng)濟和更高的發(fā)電效率加強了這種（電力增長的）趨勢。35Theexpandinggascomingfromtheturbineandmovingalongthejetnozzles（噴嘴）

continuestoexpandandacceleratetoformahighvelocity.英語主謂結(jié)構(gòu)這一問題可以從英語名詞的數(shù)、基本的英語主謂結(jié)構(gòu)類型以及定語從句主謂結(jié)構(gòu)的識別等三方面來判斷。（1）英語名詞的數(shù):謂語動詞根據(jù)主語的單復(fù)數(shù)的不同發(fā)生單復(fù)數(shù)的變化。-s結(jié)尾的名詞不一定是復(fù)數(shù)(如一些表示學(xué)科的名詞、專有名詞)Electronics(電子學(xué))isthebasisofallcommunicationssystem.Mechanics(力學(xué))hasdevelopedalotinmoderntimes

又如：thermodynamics，physics,optics.36Generalmotors(通用汽車公司)producesmanydifferenttypesofcars.（2）基本的英語主謂結(jié)構(gòu)類型

單個名詞+謂語動詞并列名詞+謂語動詞名詞+后置定語/狀語+謂語動詞謂語動詞+名詞（倒裝句）另外，還有非謂語動詞或從句充當主語

不定式（短語）+謂語動詞動名詞（短語）+謂語動詞主語從句+謂語動詞37單個名詞+謂語動詞The20thcenturyhaswitnessedabigexpansionofelectricalpowergenerationanddistribution。并列名詞+謂語動詞并列名詞有三類：and、or單個并列連接詞連接起來作主語的名詞。Notonly…butalso,neither…nor,either…or組合并列連接詞連接起來作主語的名詞。Aswellas,alongwith,togetherwith,inadditionto等介詞短語連接起來的名詞。Therotorshaftand

thefieldstructurearemadeofasolidalloysteel（固體合金鋼）forging（鍛造）inwhichslots（槽）aremachinedtoacceptthefieldcoils（勵磁線圈）,asshowninFigure2.And用復(fù)數(shù)，or由后面的名詞決定。Notonlycoalandoilbutalsofallingwaterisbeingusedtoproduceelectircity.Neither….nor,either…or…由后面的名詞決定。并列名詞+謂語動詞39Thevariousmanifestations（表現(xiàn)形式）

ofelectricityaretheresultoftheaccumulationormotionofelectrons.名詞+后置定語/狀語+謂語動詞Themachineaswellasitsauxiliarydevicesisimported.Aswellas,alongwith由后面的名詞決定。40Thehydroelectricpowerusingafallofwatertodrivewaterturbines

hasbeendevelopedtogenerateelectricity.Anotherimportantfactortobetakenintoconsiderationisthatcurrentstrengthisequalatcertainpointsinaseriescircuit.41Thereare

fourwaysfortransmittingpowerfromtheelectricmotortothespindle.謂語動詞+名詞are是謂語動詞，are提示主語是后面的復(fù)數(shù)名詞ways.Touseanyofthesefuelsneedsourseriousconsideration.不定式（短語）+謂語動詞主語是不定式短語，而不是fuels.Generatingcurrentatalowerfrequencyandthenboostingittoahigherfrequencyaremoreefficient.動名詞（短語）+謂語動詞主語是兩個并列的動名詞42Whetherthisunitwilloperateefficientlyremainstobeseen.Whatpotentialenergyandkineticenergymeansandhowweexplainthesetwoterms

havebeenmentionedinthisarticle.（3）定語從句的主謂結(jié)構(gòu)的判別

由于定語從句的主語可能是由that或which等連接詞來充當，that或which到底指代什么，有時需要通過主謂結(jié)構(gòu)的分析才能搞清。主語從句+謂語動詞Thisprocessenhancestheoverallthermalefficiencyofenergyconversiontoabout50percent-asopposedtoconventionalprocesses,whichhaveanefficiencyofabout36to38percent.Thisprocessenhances

theoverallthermalefficiencyofenergyconversiontoabout50percent-asopposedtoconventionalprocesses,whichhaveanefficiencyofabout36to38percent.43高壓輸電線路通常是由銅、鋁或包銅的線組成，這些線通過一連串瓷制絕緣體，懸掛于高高的鋼鐵格子塔架上。Thelineofhigh-voltagetransmissionsystemsareusuallycomposedofwiresofcopper,aluminum,orcopper-clad,whicharesuspended（懸浮于）fromtalllatticeworktowersofsteelbystringsofporcelaininsulators（瓷制絕緣體）.Thelineofhigh-voltagetransmissionsystemsareusuallycomposedofwiresofcopper,aluminum,orcopper-clad,whicharesuspended（懸浮于）fromtalllatticeworktowe