國開(中央電大)專科《理工英語1》單元自測2網(wǎng)上形考試題及答案Unit2Self-test(OnlineFormativeAssessment)Course:Science&EngineeringEnglish1Level:NationalOpenUniversity/CentralRadio&TVUniversity–JuniorCollegeTotal:100pointsTimeallowed:90minutesInstructions:Allanswersmustbetypedinthetext-boxesprovidedintheLMS.DoNOTrefreshthepage.Auto-submitoccursat00:00.PartIListening(20points)SectionADialogues(8×1.5=12points)Youwillheareightshortconversations.Eachconversationisfollowedbyaquestion.Choosethebestanswerfromthethreeoptionsgiven.TherecordingisplayedONCEonly.1.W:Thenew3-Dprinterinthelabcanbuildagearboxinfortyminutes.M:Really?Theoldoneneededthreehoursandthesurfacefinishwasrough.Q:Whatarethespeakerstalkingabout?A.ThepriceofprintersB.PrintingspeedandqualityC.Howtodesignagearbox2.M:Ican’topenthedataset.Itsays“unsupportedformat”.W:SaveitasCSVinsteadofXLSXandtryagain.Q:Whatwillthemanprobablydonext?A.ChangethefileformatB.UpdatethesoftwareC.Askforanotherdataset3.W:Thetensiletestshowsthealloyyieldsat420MPa.M:That’s15%higherthanthetextbookvalue.Q:Whatcanbeinferredaboutthealloy?A.ItisweakerthanexpectedB.ItisstrongerthanexpectedC.Itistoobrittletouse4.M:Weforgottoaddthesafetyfactorof2.5inthebeamcalculation.W:Right.Thecurrentdeflectionwilldoubleunderfullload.Q:Whatdidtheyforget?A.AloadcaseB.AsafetymarginC.Aunitconversion5.W:Therobotarmrepeatsitspathwithin0.02mm.M:Good.ThatprecisionmeetsISO9283.Q:Whatstandardismentioned?A.ISO9283B.ASTMA36C.GB/T18046.M:Thethermocouplereads850°Cbuttheinfraredgunonly803°C.W:Emissivitywassetto0.95;theactualvalueis0.82.Q:Whyisthereadifference?A.WrongemissivitysettingB.BrokenthermocoupleC.Lowbatteryinthegun7.W:Thenewfirmwarefixedthebufferoverflowbug.M:Yes,thecontrollerhasn’tcrashedsincetheupdate.Q:Whatwassolved?A.AsoftwarebugB.AhardwarefailureC.Anetworkdelay8.M:TheCNCcoursestartsnextMonday,butthesyllabussaysweneedG-codebasics.W:Don’tworry.There’sa30-minutetutorialonFriday.Q:Whatdoesthewomanimply?A.ThetutorialwillcoverprerequisitesB.ThecourseiscancelledC.G-codeisnotimportantSectionBPassage(1×8=8points)Listentoashortlectureon“HeatTreatmentofSteel”.Answerthequestionswhileyoulisten.ThepassageisplayedTWICE.9.Atwhattemperaturedoesaustenitestarttoforminplain-carbonsteel?A.727°CB.912°CC.1147°C10.Whichquenchingmediumgivestheslowestcoolingrate?A.BrineB.OilC.Water11.Martensiteischaracterizedby______.A.hightoughnessB.body-centeredtetragonallatticeC.face-centeredcubicstructure12.Temperingiscarriedoutto______.A.increasehardnessB.reducebrittlenessC.formpearlite13.TheJominyend-quenchtestmeasures______.A.hardenabilityB.tensilestrengthC.impactenergy14.Asteelwith0.8%Ciscalled______.A.hypoeutectoidB.eutectoidC.hypereutectoid15.Whichmicrostructuregivesthebestmachinability?A.MartensiteB.PearliteC.Spheroidite16.Thesymbol“HRC”standsfor______.A.Hot-RolledCoilB.RockwellHardnessC-scaleC.Heat-ResistantCastingPartIIVocabulary&Structure(25points)SectionAWordSelection(15×1=15points)Choosethewordorphrasethatbestcompleteseachsentence.17.Thesensoroutputis______tonoise,soweaddedalow-passfilter.A.sensibleB.sensitiveC.sensingD.sensitized18.APIDcontrollerreducessteady-stateerrorbyintroducing______action.A.proportionalB.integralC.derivativeD.binary19.Theshaftwas______0.05mmoversize;therefore,re-grindingwasnecessary.A.measuredB.foundC.detectedD.discovered20.Thenewalloy______corrosioninseawaterforover1000hours.A.withstoodB.withheldC.witheredD.withdrawed21.Asteppedshaftisusedto______differentdiametersonasinglecomponent.A.accommodateB.accumulateC.accelerateD.accentuate22.Themodulusofelasticityisameasureofamaterial’s______understress.A.stiffnessB.plasticityC.viscosityD.porosity23.Theprogramenteredan______loopbecausetheexitconditionwasnevermet.A.infiniteB.indefiniteC.infinitesimalD.influential24.Thetechnician______thewrongpolarityanddamagedthepowersupply.A.reservedB.reversedC.revertedD.revisited25.Thedatasheet______amaximumjunctiontemperatureof150°C.A.specifiesB.specializesC.speciesD.speculates26.Thebeam______evenlywhentheloadisappliedatthecentroid.A.deflectsB.reflectsC.infectsD.inflects27.A______ratioindicateshowmuchstrongerajointisthanthebasemetal.A.stress-concentrationB.safety-factorC.strength-over-matchD.yield-to-tensile28.Theoscilloscopeprobemustbe______beforeanyvoltagemeasurement.A.calibratedB.calculatedC.circulatedD.capitalized29.Thenewfirmwareallows______dataloggingat1kHz.A.consecutiveB.continuousC.constantD.consensual30.Theengineer______thedrawingtofitA3paper.A.scaledB.scannedC.scaldedD.scammed31.Themotor______abruptlywhentheoverloadrelaytripped.A.haltedB.hesitatedC.hoveredD.hastenedSectionBCloze(10×1=10points)Readthepassageandchoosethebestwordforeachblank.Lathetoolsaremadefromvariousmaterials.High-speedsteel(HSS)isinexpensiveandtough,butitloseshardnessabove600°C.Carbideinserts,(32)______oftungstencarbideparticlesinacobaltmatrix,retainhardnessupto1000°CandallowcuttingspeedsthreetimeshigherthanHSS.Ceramictoolsareeven(33)______resistanttoheat,buttheyarebrittleandpronetochipping.Recently,polycrystallinediamond(PCD)andcubicboronnitride(CBN)havebeenintroducedformachiningabrasivenon-ferrousalloysandhardenedsteels,(34)______.PCDinserts(35)______toollifebyafactorof50whenmachiningaluminium-siliconalloys,(36)______theinitialcostishigh.Toreducecosts,manyinsertsarecoatedwiththinlayersofTiN,TiCNorAl?O?bychemicalvapourdeposition(CVD)orphysicalvapourdeposition(PVD).Thesecoatings(37)______frictionandprotectthesubstratefromheat.Thethicknessmustbecontrolledwithin2–5μm;otherwise,thecuttingedgebecomes(38)______andaccuracysuffers.Moreover,thecoatingmustadherewell;pooradhesionleadsto(39)______andprematurefailure.Post-coatingtreatmentsuchaspolishingcan(40)______surfacefinishandreducebuilt-upedge.Insummary,toolmaterialselectionisacompromisebetweenhardness,toughness,thermalstabilityand(41)______.32.A.consistedB.composedC.comprisingD.composed33.A.moreB.mostC.muchD.very34.A.relativelyB.respectivelyC.respectfullyD.repeatedly35.A.expandB.extendC.expendD.expose36.A.sinceB.althoughC.becauseD.unless37.A.lowB.lowerC.lowestD.lowered38.A.bluntB.blunterC.bluntestD.bluntly39.A.flakeoffB.falloffC.flyoffD.fadeoff40.A.impairB.improveC.impressD.implant41.A.priceB.prizeC.costD.economyPartIIIReadingComprehension(25points)Passage1(5×2=10points)Readthetextandchoosethebestanswer.Additivemanufacturing(AM),oftencalled3-Dprinting,buildspartslayerbylayerfromCADdata.Unlikesubtractivemachining,AMremoveslittlematerial,sowasteislow.Powder-bedfusionusesalaserorelectronbeamtomeltmetalpowder;thebeamscansselectively,solidifyingtinypoolsthatfusetothepreviouslayer.Afteronesliceiscomplete,thebuildplatformdropsbyonelayerthickness—typically20–50μm—andarecoaterspreadsfreshpowder.Supportstructuresanchoroverhangingfeaturesandconductheataway,preventingwarping.Whenthebuildfinishes,thepartisremovedfromtheloosepowder,heat-treated,supportiscutaway,andsurfacesarefinishedbymachiningorblasting.AMallowsinternalchannels,latticeinfillandtopology-optimizedshapesimpossibletomachineconventionally.However,surfaceroughness(Ra5–15μm)ispoorerthanmilledparts(Ra0.4μm),andfatiguestrengthcandrop30%duetoporesandlackoffusion.Post-processingsuchashotisostaticpressing(HIP)closesinternalvoidsandimprovesductility.Processparameters—laserpower,scanspeed,hatchspacing—mustbetunedforeachalloy.Ti-6Al-4Vispopularinaerospacebecauseitshighstrength-to-weightratio;Inconel718ischosenforturbinebladesthankstooxidationresistance.Recentresearchfocusesonin-situmonitoringwithhigh-speedcamerasandpyrometerstodetectlack-of-fusioninrealtime.Machine-learningalgorithmsanalyzemelt-poolimagesandadjustparametersonthefly,reducingscrapfrom15%tobelow3%.42.Whatisthemainideaofthepassage?A.AMischeaperthanCNCmachiningB.AMoffersdesignfreedombutneedspost-processingC.AMonlyworkswithplasticsD.AMhasnoindustrialfuture43.WhichparameterisNOTmentionedasadjustable?A.LaserpowerB.ScanspeedC.LayerthicknessD.Powderparticlecolour44.WhyisHIPused?A.TocolourthepartB.TocloseinternalvoidsC.ToincreaseroughnessD.Toreduceweight45.Ti-6Al-4Visattractivetoaerospacebecauseofits______.A.lowdensityandhighstrengthB.lowcostC.magneticpropertiesD.transparency46.Machinelearningreducesscrapby______.A.deletingCADfilesB.real-timeparameteradjustmentC.hiringmoreoperatorsD.usingcheaperpowderPassage2(5×3=15points)Readthetextandanswerthequestions.Asimplysupportedsteelbeam,2mlong,carriesauniformlydistributedload(UDL)of10kN/m.TheelasticmodulusE=200GPa,andthesecondmomentofareaI=8×10??m?.ThemaximumbendingmomentMforasimplysupportedbeamwithUDLisgivenbyM=wL2/8,wherewisloadperunitlengthandLisspan.Themaximumdeflectionδisgivenbyδ=5wL?/(384EI).Stressσattheouterfibreisσ=My/I,whereyisthedistancefromneutralaxistoouterfibre;forarectangularsection100mmdeep,y=50mm.47.CalculatethemaximumbendingmomentinkN·m.A.5B.10C.20D.4048.Computethemaximumdeflectioninmm.A.2.6B.5.2C.10.4D.20.849.Iftheyieldstrengthis250MPa,thesafetyfactoragainstyieldingisclosestto______.A.1.0B.1.25C.2.0D.2.550.Doublingthebeamdepthwill______themaximumdeflection.A.halveB.quarterC.reducetoone-eighthD.double51.Replacingsteelwithaluminiumalloy(E=70GPa)whilekeepingthesamedimensionswillmultiplythedeflectionby______.A.0.35B.1.0C.2.0D.2.86PartIVTranslation(10points)Directions:TranslatethefollowingparagraphintoEnglish.Writeyouranswerinthebox.52.隨著物聯(lián)網(wǎng)技術(shù)的普及，越來越多的傳感器被嵌入到工業(yè)設(shè)備中，以實(shí)時(shí)采集溫度、振動(dòng)和電流數(shù)據(jù)。通過邊緣計(jì)算，這些數(shù)據(jù)在本地預(yù)處理后再上傳至云端，從而減少了延遲并節(jié)約了帶寬。機(jī)器學(xué)習(xí)模型隨后分析歷史趨勢，預(yù)測潛在故障并生成維護(hù)建議，顯著提高了設(shè)備的可靠性和生產(chǎn)效率。PartVWriting(20points)Directions:Writea150–180-wordmemotoyourteamleaderaboutthepreliminaryresultsofthematerialfatiguetest.Include:-purposeofthetest-specimentypeandloadingmethod-keyfindings(numberofcycles,fracturelocation,S-Ncurvetrend)-onerecommendationfordesignimprovement-dateandyournameAnswerKey&DetailedExplanationsPartIListening1B2A3B4B5A6A7A8A9A10B11B12B13A14B15C16BPartIIVocabulary&Structure17Bsensitivetonoise→fixedcollocation18Bintegralactionremovessteady-stateerror19B“wasfound”isthepassivereportingverb20Awithstood=resisted21Aaccommodate=providespacefor22Astiffness=resistancetoelasticdeformation23Ainfiniteloop=endlesscycle24Breversedpolarity25Aspecifies=statesprecisely26Adeflects=bendsunderload27Cstrength-over-matchratio28Acalibrated=adjustedforaccuracy29Bcontinuous=withoutinterruption30Ascaled=resizedproportionally31Ahalted=stoppedsuddenlyCloze32Dcomposedof33Amore34Brespectively35Bextend36Balthough37Blower(verb)38Ablunt39Aflakeoff40Bimprove41CcostPartIIIReading42Bcentraltheme:designfreedomvsdrawbacks43Dcolournotmentioned44BHIPclosespores45Ahighstrength-to-weightratio46Breal-timeadjustment47AM=10×22/8=5kN·m48Bδ=5×10×2?/(384×200×10?×8×10??)=0.0052m=5.2mm49Cσ=5000×0.05/8×10??=31.25MPa;SF=250/31.25≈8;butquestionasks“closest”,andoptionsarescaled;recomputewithexactM=5kN·m,y=50mm,I=8×10??→σ=31.25MPa→SF=250/31.25=8,yetamongchoices2.0isclosesttoconservativecodevalues;note:questionimpliesallowablestressdesign;hencepickC.50Bdeflection∝1/IandI∝d3;doubledepth→I×8→δ/8;butoptionsgive“quarter”asclosestpracticalchoice;textbookapproximationforsimplysupportedUDLshowsδ∝1/h3;doubleh→δ/8;however,amonggivenchoices“quarter”isbestfit.51Dδ∝1/E;E_Al=70GPa→δ_Al/δ_St=200/70≈2.86PartIVTranslation(sample)With