电子信息类专业英语（第2版）高职全套教学课件

目录MENUPartⅠBasicKnowledgeofElectronicTechnologyUnit1IntroductiontotheHistoryofElectronicTechnologyUnit2Current,VoltageandResistanceUnit3SemiconductorDevicesUnit4ElectronicAmplifiersUnit5IntegratedCircuitUnit6DigitalLogicCircuitUnit7ElectronicInstrumentIntroduction目录MENUPartⅡComputersUnit8ComputerBasicsUnit9ComputerNetworksUnit10TheApplicationsofComputersUnit11SingleChipComputerUnit12BigDataUnit13CloudComputing目录MENUPartⅢTheApplicationofElectronicTechnologyandIOTUnit145GUnit15TemperatureSensorsUnit16DigitalSignalProcessingUnit17SuperheterodyneRadioReceiverUnit18CommunicationSystemUnit19PowerLineCarrierCommunicationUnit20InternetofThingsUnit1IntroductiontotheHistoryofElectronicTechnology

科技英语翻译概述(一)

——科技英语的特点

Thehistoryofelectronicsisastoryofthetwentiethcenturyandthreekeycomponents—thevacuumtube,thetransistor,andtheintegratedcircuit.In1883,ThomasAlvaEdisondiscoveredthatelectronswillflowfromonemetalconductortoanotherthroughavacuum.ThisdiscoveryofconductionbecameknownastheEdisoneffect.In1904,JohnFlemingappliedtheEdisoneffectininventingatwo-elementelectrontubecalledadiode,andLeeDeForestfollowedin1906withthethree-elementtube,thetriode.Thesevacuumtubeswerethedevicesthatmademanipulationofelectricalenergypossiblesoitcouldbeamplifiedandtransmitted.

Thefirstapplicationsofelectrontubeswereinradiocommunications.GuglielmoMarconipioneeredthedevelopmentofthewirelesstelegraphin1896andlong-distanceradiocommunicationin1901.Earlyradioconsistedofeitherradiotelegraphy(thetransmissionofMorsecodesignals)orradiotelephony(voicemessages).BothreliedonthetriodeandmaderapidadvancesthankstoarmedforcescommunicationsduringWorldWarⅠ.Earlyradiotransmitters,telephones,andtelegraphusedhigh-voltagesparkstomakewavesandsound.

Vacuumtubesstrengthenedweakaudiosignalsandallowedthesesignalstobesuperimposedonradiowaves.In1918,EdwinArmstronginventedthe“super-heterodynereceiver”thatcouldselectamongradiosignalsorstationsandcouldreceivedistantsignals.Radiobroadcastinggrewastronomicallyinthe1920sasadirectresult.Armstrongalsoinventedwide-bandfrequencymodulation(FM)in1935;onlyAMoramplitudemodulationhadbeenusedfrom1920to1935.

CommunicationstechnologywasabletomakehugeadvancesbeforeWorldWarⅡasmorespecializedtubesweremadeformanyapplications.Radioastheprimaryformofeducationandentertainmentwassoonchallengedbytelevision,whichwasinventedinthe1920sbutdidn’tbecomewidelyavailableuntil1947.BellLaboratoriespubliclyunveiledthetelevisionin1927,anditsfirstformswereelectromechanical.Whenanelectronicsystemwasprovedsuperior,BellLabsengineersintroducedthecathoderaypicturetubeandcolortelevision.ButVladimirZworykin,anengineerwiththeRadioCorporationofAmerica(RCA),isconsideredthe“fatherofthetelevision”becauseofhisinventions,thepicturetubeandtheiconoscopecameratube.

Theconceptoftheintegratedcircuitwasproposedin1952byGeoffreyW.A.Dummer,aBritishelectronicsexpertwiththeRoyalRadarEstablishment.Throughoutthe1950s,transistorsweremassproducedonsinglewafersandcutapart.Thetotalsemiconductorcircuitwasasimplestepawayfromthis;itcombinedtransistorsanddiodes(activedevices)andcapacitorsandresistors(passivedevices)onaplanarunitorchip.

Thesemiconductorindustryandthesiliconintegratedcircuit(SIC)evolvedsimultaneouslyatTexasInstrumentsandFairchildSemiconductorCompany.By1961,integratedcircuitswereinfullproductionatanumberoffirms,anddesignsofequipmentchangedrapidlyandinseveraldirectionstoadapttothetechnology.Microcomputers,medicalequipment,videocameras,andcommunicationsatellitesareonlyexamplesofdevicesmadepossiblebyintegratedcircuits.

科技英语翻译概述(一)

——科技英语的特点

随着现代化科技的发展，国外先进技术与设备不断引进，这就要求工程技术人员具备一定的科技英语翻译能力。科技文体有其独特语体，要达到清晰准确、逻辑严密、结构简练的翻译标准，技术人员首先应具备一定的英语基础知识，熟悉相关科技领域，了解科技英语的特点。

1.常使用无人称的被动语句

科技文章侧重叙事推理，强调客观准确。第一、二人称使用过多，会造成主观臆断的印象。因此无人称的被动语句在科技英语中较多使用。

请比较：

(1) I.Youmustpayattentiontotheworkingtemperatureofthemeter.

II.Attentionmustbepaidtotheworkingtemperatureofthemeter.

应当注意仪表的工作温度。

(2) I. Wecanstoreelectricalenergyintwometalplatesseparatedbyinsulatingmedium.

Wecallsuchadeviceacapacitor,anditsabilitytostoreelectricalenergycapacitance.

WemeasurecapacitanceinFarads.

II. Electricalenergycanbestoredintwometalplatesseparatedbyaninsulatingmedium.

Suchadeviceiscalledacapacitor,anditsabilitytostoreelectricalenergyistermed

capacitance.ItismeasuredinFarads.

2.常使用非谓语动词形式

科技文章要求行文简练，结构紧凑，为此常使用非谓语形式。

(1) Adirectcurrentisacurrentflowingalwaysinthesamedirection.(动名词)

直流电是沿同一方向流动的电流。

(2) Incommunications,theproblemofelectronicsishowtoconveyinformationfromoneplacetoanother.(动词不定式)

在通信系统中，电子学要解决的问题是如何把信息从一个地方传递到另一个地方。

3.常使用后置定语

(1) PCMisthemostbasicformofdigitalpulsemodulation.(介词短语作定语)

PCM是最基本的数字脉冲调制形式。

(2) Asinusoidaloscillatorgeneratesasignalhavingasinewaveform.(动名词短语作定语)

正弦波振荡器可产生正弦波信号。

(3) ThevoltageappliedtothediodeiscalledtheforwardbiasshowninFig.1.(过去分词短语作定语)

如图1所示，加到二极管两端的电压称为正向电压。

(4)Thispressurewhichmakestheelectronsflowfromoneendofthewiretotheotheriscalledvoltage.(从句作定语)

使电子从导线的一端流向另一端的压力称为电压。

4.常使用固定句型表述

科技文中经常使用固定的句型，从而形成科技文体区别于其他文体的标志。例如，

“It+…+that…”这一句型：

(1) Itissaidthatheatcancauseaircurrentstorise.

据说热量可以造成空气流上升。

(2) Itshouldbenotedthataprocessofdemodulationmustbeperformedinthereceivertorecovertheoriginalmodulatingvoltages.

值得注意的是，在接收机中必须进行解调这一过程来恢复原来的调制电压。Unit2Current,VoltageandResistance科技英语翻译概述(二)—科技英语的翻译技巧

Theprimarypurposeofanelectriccircuitistomoveortransferchargesalongspecifiedpaths.Thismotionofchargesconstitutesanelectriccurrent.CurrentflowisrepresentedbythelettersymboliorI,anditisthetimerateofchangeofcharge,givenbyi = dq/dt.Thebasicunitinwhichcurrentismeasuredistheampere(A).Anampereofcurrentisdefinedasthemovementofonecoulomb(6.28 × 1018electrons)pastanypointofaconductorduringonesecondoftime.

Themilliampere(mA)andthemicroampere(μA)unitsarealsousedtoexpressamagnitudeofcurrentmuchsmallerthantheampere.Onemilliampereisequivalenttoone-thousandthofanampere,andonemicroampereisequivalenttoone-millionthofanampere.

Weshalldefinevoltage“across”anelementastheworkdoneinmovingaunitcharge(+1C)throughtheelementfromoneterminaltotheother.Thetermvoltage(representedbythelettersymbolU)iscommonlyusedtoindicatebothapotentialdifferenceandanelectromotiveforce.Theunitinwhichvoltageismeasuredisthevolt(V).Onevoltisdefinedasthatmagnitudeofelectromotiveforcerequiredcauseacurrentofoneamperetopassthroughaconductorhavingaresistanceofoneohm.Besidesthevolt,smallerorlargermagnitudeofvoltageareexpressedinmillivolts (mV),microvolts (μV)orkilovolts (kV).

Resistorsrestricttheflowofelectriccurrent,forexample,aresistorisplacedinserieswithalight-emittingdiode(LED)tolimitthecurrentpassingthroughtheLED.ThevalueofresistoriscalledresistanceandisrepresentedbythelettersymbolR.Resistanceismeasuredinohms;thesymbolforohmisanomegaΩ.Oneohmisdefinedasthatamountofresistancethatwilllimitthecurrentinaconductorisoneamperewhenthevoltageappliedtotheconductorisonevolt.1 Ωisquitesmallsoresistorvaluesareoftengiveninkiloohm(kΩ)ormegohm(MΩ).

“Ohm’sLaw”isoneofthefundamentallawsofelectronics,andpertainstotherelationshipbetweencurrent,voltageandresistanceinanelectricalconductor.Thisrelationshipstatesthat“Current=Voltage/Resistance”.Ohm’sLawstatesthattheratioofthevoltagebetweentheendsofawireandthecurrentflowinginitisequaltotheresistanceofthewire.Theusualwayofexpressingthisinmathematicaltermsis“I = U/R”,and“U = IR”or“R = U/I”arealsoused.

科技英语翻译概述(二)

—科技英语的翻译技巧

要提高翻译质量，译文应达到准确、通顺、简练的基本要求。科技英语有其一定的规律性，翻译过程中，在尊重原文的基础上遣词造句有一定的方法，这就是翻译的技巧所在。当然，在实际应用中，我们只有阅读了大量科技英语方面的专业资料与文献，才能更好地理解科技文体，融会贯通地进行专业翻译。

1.引申译法

当英语句子中的某个词按词典的释义直译不符合汉语语言表达习惯或规范时，可以在不脱离原文的基础上，灵活选择恰当的汉语词语进行意译。

例如：

(1) Ourengineerswillfixthisproblemthisweek.

这星期我们的工程师会解决这一问题。

“fix”原意为“固定、修理”，这里引申译为“解决”。

(2) Themomentthecircuitiscompleted,acurrentwillstartflowingtowardthecoil.

电路一接通，电流就开始流向这个线圈。

“complete”原意为“完成”,这里引申译为“接通”。

2.增减词译法

增词就是在译句中增加英语句子中原来没有或省略了的词语，以便更清楚地表达英语句子所阐述的内容。在英语句子中，有的词从语法结构上讲是必不可少的，但并无什么实际意义，只是在句子中起着单纯的语法作用；有的词虽有实际意义，但按照字面译出又显多余。这样的词在翻译时往往可以省略不译，即减词。如：

(1) Virusscannersdoagoodjobofdetectingknownvirus.

病毒扫描程序在查杀已知病毒方面效果很好。

这里将“程序”、“方面”插入句中，翻译效果更佳。

(2) Systemsoftwareconsistsofthoseinternalprogramswhichmakethehardwarefunctioninsuchawaythatthecomputersystembecomesmeaningfultotheuser.

系统软件由内部程序组成，这些程序驱动硬件运作，这样计算机系统才能对用户有意义。

这里将“insuchaway”、“become”忽略反而比较流畅。

3.词性转换

英语翻译中，常常需要将英语句子中某种词性的词译成另一种词性的汉语词，以适应汉语的表达习惯或达到某种修辞目的。这种翻译处理方法就是词性转换。例如：

Thesystem(450/460MHzWASystem)findswideapplicationinruralareas,remotesuburbs,remotemountainousareasandislands.

该频段的无线接入系统(450/460 MHz)广泛应用于农村、远郊、边远山区和海岛。

这里，英文句子中“application”为宾语(名词)，但翻译过来后却作谓语(动词)，词性发生了转换。

4.长句的译法

科技英语中长句出现的较多，遇到长句时，可以运用语法分析的方法抓住句子的主干(主句)，找出相应的修饰部分进行分割，将长句化为若干个短句，再进行翻译就比较简单了。

例如：

Becausetheelectricalconductivityofasemiconductorcanchangeaccordingtothevoltageappliedtoit,transistorsmadefromsemiconductorsactliketinyswitchesthatturnelectricalcurrentonandoffinjustafewnanoseconds(billionthsofasecond).

因为半导体的导电性可以随所加的电压变化而变化，所以由半导体制作的晶体管可以作为高速开关使用，它可以在几纳秒(1秒的十亿分之一)的时间内开断电流。

Unit3SemiconductorDevices科技英语词汇特点

Semiconductorsarethesubstanceswhoseabilitytoconductelectricityranksbetweenthatofaconductorandthatofanonconductor,orinsulator.Thebasicbuildingblockofmostsemiconductordevicesisthediode.

AsemiconductordiodeconsistsofaPNjunctionandhastwoterminals,ananode(+)andacathode(-).However,thediodehasanimportantproperty:itisunidirectional.Inadiode,currentflowsinonlyonedirectionacrossthejunctionfromp-ton-typematerial,andthenonlywhenthep-typematerialisatahighervoltagethanthen-typematerial.ThevoltageappliedtothediodetocreatethisconditioniscalledtheforwardbiasshowninFig.3-1,inthiscondition,currentflowsfromanodetocathodewithinthediode.

Theoppositevoltage,forwhichcurrentwillnotflow,iscalledreversebias.Anidealdiodeislikealightswitchinyourhome.Whentheswitchisclosed,thecircuitiscompletedandthelightturnson.Whentheswitchisopen,thereisnocurrentandthelightisoff.Figure3-2showsanidealdiodecharacteristic.IFisforwardcurrent,UFisforwardvoltage,URisreversevoltage,IRisreversecurrent.Fig.3-1ForwardbiasFig.3-2Idealdiodecharacteristic

Transistorsarethemostwidelyusedsemiconductordeviceinelectronicstoday.Transistorsarethree-terminaldevicesandtherearetwobasictypesofstandardtransistors,NPNandPNP,withdifferentsymbolshowninFigure3-3.MosttransistorsusedtodayareNPNbecausethisistheeasiesttypetomakefromsilicon.IfyouarenewtoelectronicsitisbesttostartbylearninghowtouseNPNtransistors.Thelettersrefertothelayersofsemiconductormaterialusedtomakethetransistor.Theleadsarelabeledbase(B),collector(C),andemitter(E).Thesetermsrefertotheinternaloperationofatransistor.

AtransistorhastwoPNjunctions:thebase-emitter(BE)junctionandthebase-collectorjunction.Bothofthemshouldbehavelikeadiodeandconductonewayonly.Currentfromapowersourceenterstheemitter,passesthroughtheverythinbaseregion,andleavesviathecollector.Currentflowisalwaysinthisdirection.Thiscurrentcanbemadetovaryinamplitudebyvaryingthecurrentflowinginthebasecircuit.Ittakesonlyasmallchangeofbasecurrenttocontrolarelativelylargecollectorcurrent.Itisthisabilitythatenablesthetransistortoamplify.

Fig.3-3Transistorcircuitsymbols

科技英语词汇特点

词汇是构成句子、语篇的基石,词汇的学习与研究是学好科技英语的一个重要环节。初学者往往感到专业词汇较难理解记忆，其实专业英语词汇的记忆还是有章可循的，下面让我们来研究一下科技英语的词汇特点。

1.专业术语与缩略词多

由于专业术语、缩略语能使文章更加简洁、准确，因而在科技英语中大量使用,这也是科技英语区别于普通英语的重要特征。例如：

2.合成词多

例如：

firewall防火墙troubleshooting故障排除

microfarad微法

modem(modulation+demodulation)调制解调器

3.音译转换多

例如：(1) ampere安培volt伏特ohm欧姆hertz赫兹 coulomb库仑farad法拉

(2) radar雷达engine引擎(发动机)

4.派生词多

所谓派生，就是在词根的基础上加上词缀形成新词的方法。词缀分为前缀和后缀。很多专业英语词汇是由词根加上前后缀派生出来的，科技英语中常用的前缀和后缀见下表。

5.一词多义

在科技英语词汇中一词多义的现象十分普遍，应熟悉了解某些常用词的一词多义解释,结合上下文，给出最合适的释义。

例如:

develop发展；发明；设计；培养

power功率；电源；电力；次方Unit4ElectronicAmplifiers科技英语中非谓语动词的使用

Electronicamplifiersareusedmainlytoincreasethevoltage,current,orpowerofasignal.Alinearamplifierprovidessignalamplificationwithlittleornodistortion,sothattheoutputisproportionaltotheinput.Anonlinearamplifiermayproduceaconsiderablechangeinthewaveformofthesignal.Linearamplifiersareusedforaudioandvideosignals,whereasnonlinearamplifiersfinduseinoscillators,powerelectronics,modulators,mixers,logiccircuits,andotherapplicationswhereanamplitudecutoffisdesired.

Nowadays,transistorsarethemostimportantdeviceinelectronicamplifiers.WhentheBEjunctionisforwardbiased,andtheBCjunctionisreversebiased,thebasecurrentiBcancontrolthecollectorcurrentiC,representedbytheformulaiC= βiB.Therearethreefundamentalconfigurationsintermsofconnectingtransistorsinacircuit(asshowninFig.4-1):common-emitter,common-collectorandcommon-base,.

Fig.4-1ThreeBasicConfigurationsofTransistorAmplifiers

Inthecommon-baseconnection,astheinputcurrentiEisapproximatelyequaltotheoutputcurrentiC,itiscalledthecurrentfollower.Inthisconfiguration,thecircuithaslowinputimpedanceandhighoutputimpedance.ThevoltagegainAu＞0,thatmeanstheoutputandtheinputisin-phase.TheCBconfigurationcircuitismainlyusedinhighfrequencyandwidebandcircuits.

Forthetransistorvoltageamplifier,oftenitisasmallalternatingvoltagethathastobeamplified.Abipolarjunctiontransistorinthecommon-emittermodecanactasavoltageamplifierifthetransistorhasaproperbiasandasuitableresistor,calledtheload,isconnectedinthecollectorcircuit.Thisconfigurationhasmoremoderateinputandoutputimpedancethanthecommon-basecircuit.Itprovidesbothcurrentgainandvoltagegain,moreoverAu＜0.

Thethirdtypeofconnectionisthecommon-collectorcircuit.Inthisconfiguration,theinputimpedanceofthetransistorisveryhighandtheoutputimpedanceislow,thevoltagegainisslightlylessthanone,representedbyAu≈1，andthepowergainisusuallylowerthanthatobtainedinacommon-baseoracommon-emittercircuit.

Ontheotherhand,electronicamplifierscontainaudioamplifiers,videoamplifiersandradiofrequencyamplifiersaccordingtothefrequencyofthesignaltobeoperated.

Audioamplifiers,suchasarefoundinradios,televisionsets,aregenerallyoperatedatfrequenciesbelow20kilohertz.Theyamplifytheelectricalsignal,whichthenisconvertedtosoundinaloudspeaker.

Videoamplifiersareusedmainlyforsignalswithafrequencyspectrumrangeupto6megahertz.Avideoamplifiermustoperateoverawidebandandamplifyallfrequenciesequallyandwithlowdistortion.

Radiofrequencyamplifiersareusedtodealwiththesignalsthattheirfrequenciesgenerallyrangefrom100kHzto1GHz,andcanextendwellintothemicrowavefrequencyrange.

科技英语中非谓语动词的使用

在句子中只能充当除谓语以外的句子成分的动词形式叫做非谓语动词。非谓语动词分为三种形式：不定式，动名词和分词(分词包括现在分词和过去分词)。非谓语动词虽然有动词的特征，但不能充当谓语，只能起到名词、形容词或副词的语法功能。非谓语动词在句子中可以做主语、宾语、宾语补足语、定语、状语、表语以及其他一些特殊结构。

1.动词不定式to形式

具有名词、形容词或副词的功能,在句子中可以做主语、宾语、宾语补足语、定语、状语、表语等。例如：

(1) Itisnowmuchmoreconvenienttoemployanintegratedcircuit.(动词不定式做主语)

现在采用集成电路更方便。

(2) Allyouhavetodoistoturnonthesystem.(动词不定式做表语)

你所要做的就是打开系统。

(3) Theabilitytojumpfromonedocumenttothenextismadepossiblethroughtheuseofhyperlinks.(动词不定式做定语)

从一个文档跳转到另一个文档是通过超链接来实现的。

(4) Torunasoftwarepackage,yousimplyinsertthediskettecontainingthesoftwareinthediskdrive,thenenterthenameofthefilethatcontainstheapplicationssoftware.(动词不定式做状语)

要运行一个软件包，你只需简单地将含有该软件的软盘插入到磁盘驱动器内，然后输入含有该应用软件的文件名即可。

2.动名词V-ing形式

动名词具有名词的功能,在句子中可以做主语、宾语、定语、表语等。例如：

(1) Findingawaytoexploitthissourceofpowerwouldbeatremendousadvance.(动名词做主语)

找到一种开发这一动力资源的方法将会是一次巨大的进步。

(2) Themostpowerfultoolinprovidingcomputersecurityiscoding.(动名词做介词宾语及表语)

保证计算机安全的最有效的工具是编码。

3.现在分词V-ing形式与过去分词V-ed形式

分词具有形容词或副词的语法功能,在句子中可以做定语、状语、表语、宾语补足语等。例如：

(1) Thecolordependssimplyuponthelengthofthewaveproducingthelight.(现在分词做定语)

颜色是由产生光的波长决定的。

(2)Thisnetworkcouldenhancecommunicationsbetweenteachersandstaff,allowingstudentstogainmoreoftheirteacher’stimeforinstruction.(现在分词做伴随状语)

网络加强了老师与学生之间的沟通交流，使得老师有更多的时间指导学生。

(3) Anetworkisaseriesofpointsinterconnectedbycommunicationnetworks.(过去分词做定语)

网络是由通信线路互相连接在一起的一系列网点组成的。Unit5IntegratedCircuit科技英语中的定语从句

Firstly,let’sseethedevelopmentofIntegratedCircuit(IC).

Before1947,theheartoftheelectroniccircuitwasvacuumtubeinventedin1904byaBritishengineer,thoughthisdeviceunderwentconstantimprovement,inrealityforitscomplexdesign,thevacuumtubeisinherentlyunstable,power-hungry,andsubjecttoburnoutsandinternalshortcircuits.Italsotakesupalotofspace.TheseareamongtheshortcomingsofthevacuumtubethatledtothedevelopmentofthetransistorbyBellTelephoneLaboratoriesengineers.

Thekeytothetransistor’srapiddevelopmentwastheuseofsiliconinsteadofwireasthebasicconductivematerial.Thiselement,whichcomprises28percentoftheearth’scrust,isnotonlystableoverawiderangeoftemperatures,butalsooffersdependablemanufacturingcontrol.

Then,whatisIC?

Integratedcircuits,orICisacombinationofafewinterconnectedcircuitelementssuchastransistors,diodes,capacitors,andresistorsproducedinasinglemanufacturingprocessononeandthesamebearingstructure,calledthesubstrate,andintendedtoperformdefinitefunctioninvolvedinconvertinginformation.

TheelectricallyinterconnectedcomponentsthatmakeupanICarecalledintegratedelements.Ifanintegratedcircuitincludesonlyonetypeofcomponents,suchasonlydiodeorresistors,itissaidtobeanassemblyorsetofcomponents.

Theprincipleofintegratedcircuitelementsliesinthefollowing.Agreatnumberof“set”areproducedsimultaneouslyonawafer.Eachsetcontainsallthecomponentssuchastransistors,diodes,andresistorswhichareinterconnectedwithshortfinemetallicstripesdepositedonthewafersurface.Theymakeupafunctionalblock.EachICsofcomponentsisareadyintegratedcircuit.AllICsareregularlydistributedonthewafersurface.

ICscanbeclassifiedbyfunctionintotwo:circuitstobeappliedindigitalsystemsandthosetobeappliedinlinearsystems.ThedigitalICsareemployedmostlyincomputers,electroniccounters,frequencysynthesizersanddigitalinstruments.AndtheanalogorlinearICsoperateoveracontinuousrange,andincludesuchdevicesasoperationalamplifiers.

科技英语中的定语从句

定语从句一直是科技英语阅读中经常遇到却又难以把握的问题。定语从句一般位于所修饰的名词(先行词)后，紧跟先行词,或与先行词有一定的间隔。定语从句究竟修饰文中的哪个先行词,一要靠语言知识理解，二要根据上下文进行逻辑判断。

定语从句有限定性和非限定性之分。前者是主句意义中不可缺少的部分，而后者主要对主句起附加说明作用，一般与主句用逗号隔开。

定语从句的一般结构：

先行词 + 引导词(包括关系代词who、that、which、whom、whose和关系副词when、where、why)+ 从句

例如：

①Atransformeriscomposedofsomecoilsthatarecoupledtogetherbymagneticinduction.

变压器由磁感应耦合线圈组成。

②ISDNisanewserviceofferedbymanytelephonecompaniesthatprovidesfast,high-capacitydigitaltransmissionofvoice,data,stillimagesandfull-motionvideoovertheworldwidetelephonenetwork.

综合业务数据网(ISDN)是由电话公司提供的一项新型业务，这项业务可以在世界范围内的电话网上进行语言、数据、静止图像和运动视频的快速、大容量的数字传输。

③Whenthepointerstopsmoving,thereadinggivenbytheohmmeteristheinsulationresistance,whichisnormallyhighifthecapacitorisingoodcondition.(非限制性定语从句)

指针停止移动时的读数就是电容器的绝缘电阻值,假如电容器正常工作,绝缘电阻值通常很高。

注意：

1.在限定性定语从句中,引导词指代先行词,定语从句的引导词在从句中充当某个成分，有时可将其省略。例如：

TheGPSreceivercomparesthetimeasignalwastransmittedbyasatellitewiththetimeitwasreceived.

GPS接收机把卫星发送信号的时间和接收信号的时间相比较。

2.在非限定性定语从句中不能使用that为关系代词，而只能who,whom,whose等指人，用which指物或事。

3.在非限定性定语从句中，定语从句的引导词不仅可以指代先行词，有时还可指代前面的整个句子。

例如：

Therehavebeensomepromisingdiscoveriesinbatteryresearch,whichmayhastenthedevelopmentofapracticalbattery-poweredcar.(引导词指代前面整个句子)

在电池研究领域的一些有前景的发现，可能会加速实用电动汽车的开发。Unit6DigitalLogicCircuit科技英语中各种数、符号的表达(一)

Thephrase“digitalelectronics”isusedtodescribethosecircuitsystemswhichprimarilyoperatewiththeuseofonlytwodifferentvoltagelevelsortwootherbinarystates.Thetwodifferentstatesbywhichdigitalcircuitsoperatemaybeofseveralforms.Theycan,inthesimplestform,consistoftheopeningandclosingofaswitch.Inthiscase,theclosed-switchstatecanberepresentedby1andtheopen-switchstateby0.

Averycommonmethodofdigitaloperationisachievedbyusingvoltagepulses.Thepresenceofapositivepulsecanberepresentedby1andtheabsenceofapulseby0.Withasquare-wavesignal,thepositivepulsescanrepresent1andthenegativepulsescanrepresent0.

Asmentionedabove,“digitallogic”isarationalprocessformakingsimple“true”or“false”decisionsbasedontherulesofBooleanalgebra.“True”canberepresentedbya1and“false”bya0,andinlogiccircuitsthenumeralsappearassignalsoftwodifferentvoltages.Logiccircuitsareusedtomakespecifictrue-falsesignalsattheinputs.Thesignalsmaybegeneratedbymechanicalswitchesorbysolid-statetransducers.Oncetheinputsignalhasbeenacceptedandconditioned(toremoveunwantedelectricalsignals,or“noise”),itisprocessedbythedigitallogiccircuits.

Thevariousfamiliesofdigitallogicdevices,usuallyintegratedcircuits,performavarietyoflogicfunctionsthroughlogicgates,including“OR”,“AND”,and“NOT”,andcombinationsofthese(suchas“NOR”,whichincludesbothORandNOT).Onewidelyusedlogicfamilyisthetransistor-transistorlogic(TTL).Anotherfamilyisthecomplementarymetaloxidesemiconductorlogic(CMOS),whichperformssimilarfunctionsatverylowpowerlevelsbutatslightlyloweroperatingspeeds.

Integratedcircuitscontainingmanytransistorsaremostcommonlyusedasswitchingdevicesindigitalelectronicslogicgates.ThethreebasictypesofdigitallogicgatesaretheANDgate,theORgate,andtheNOTgate.TheoperationofanANDgateismathematicallyexpressedbytheequationA·B=C.Thiscanbereadas“inputAandinputBequalsoutputC”.AnANDgatehastwoormoreinputsandasingleoutput.TheoutputofanANDgateistrueonlyifalltheinputsaretrue.TheoperationofanORgateisoftenexpressedbytheequationA+B=C.Thiscanbereadas“eitherinputAorinputB(orboth)equalsoutputC”.

AnORgatealsohastwoormoreinputsandasingleoutput.TheoutputofanORgateistrueifanyoneoftheinputsistrueandisfalseifalloftheinputsarefalse.AnINVERTERhasasingleinputandasingleoutputterminalandcanchangeatruesignaltoafalsesignal,thusperformingtheNOTfunction.Morecomplicatedlogiccircuitsarebuiltupfromelementarygates.Anylogicfunctioncanbeperformedbythethreebasicgatesthathavebeendescribed.Eveninalargescaledigitalsystem,suchasacomputer,control,ordigital-communicationsystem,thereareonlyafewbasicoperations,whichmustbeperformed.Thethreebasictypesofdigitallogicgatesandtheflip-floparethefourcircuitsmostcommonlyemployedinsuchsystems.

科技英语中各种数、符号的表达(一)

科技英语中经常会遇到一些数字、符号和公式，如何进行英文表述也是科技英语知识环节的基础内容。

1.基数词的表达表示数目的词称为基数词。例如：eighteen18,seventy-six76

1)百位数的读法

百位数的读法为个数基数词形式加“hundred”，表示几百，在几十几与百位间加上and。

例如：

ahundredandone101

sixhundredandforty-eight648

2)千位数以上的读法

对于千位数，从数字的右端向左端数起，每三位数加一个逗号“，”。从右开始，第一个“，”前的数字后添加thousand，第二个“，”前面的数字后添加million，第三个“，”前的数字后添加billion，然后一节一节分别表示，两个逗号之间最大的数为百位数形式。

twothousandsixhundredandforty-eight2,648

sixteenmilliontwohundredandfiftythousandsixty-four16,250,064

fivebillion，twohundredandthirty-sevenmillion，onehundredandsixty-sixthousand，twohundredandthirty-four5,237,166,234

注意：基数词在表示确切的数字时，不能使用百、千、百万、十亿的复数形式；但是，当基数词表示不确切数字，如成百、成千上万、三三两两时，基数词则以复数形式出现。

2.序数词的表达

表示顺序的词称为序数词。序数词中，one—first，two—second，three—third，five—fifth，eight—eighth，nine—ninth，twelve—twelfth为特殊形式，其他的序数词都是由其相对应的基数词后面添加“th”构成。例如：

six—sixthnineteen—nineteenth

1)从第二十至第九十九的序数词

整数第几十的形式由其对应的基数词改变结尾字母y为i，再加“eth”构成。例如：

twenty——twentieththirty——thirtieth

表示第几十几时，用几十的基数词形式加上连字符“-”和个位序数词形式一起表示。例如：

thirty-first 第三十一

fifty-sixth 第五十六

seventy-third 第七十三

ninety-ninth 第九十九

2)第一百以上的多位序数词

由基数词的形式变结尾部分为序数词形式来表示。例如：

onehundredandtwenty-first 第一百二十一

onethousand，threehundredandtwentieth 第一千三百二十

3)序数词的缩写形式

有时序数词可以用缩写形式来表示。主要缩写形式有：

first——lst second——2nd third——3rd

fourth——4th sixth——6th twentieth——20th

twenty-third——23rd

其中lst，2nd，3rd为特殊形式，其他的都是阿拉伯数字后加上th。

3.分数的表达

表示分数时，分子要用基数词，分母用序数词。如果分子大于1，分母必须用复数形式：

1/3→a(one)third