科技英语部分课后练习答案PPT课件

.,1,Amultibillion-dollarcraftcalledtheCrewExplorationVehicle(CEV).,Page26-27:,III:TextOrganization,PartI(1-3):PartII(4-7):PartIII(8-11):PartIV(12-14):PartV(15-18):,DavidGumpandGaryHudson;anentrepreneurwithfreshideas.,Innovativetechnology.,Viabilityofanewmethodforair-launchingspacecraft.,WinmoneyfromNASAandprivateinvestors.,IV:MultipleChoices,1-5CBAAC6-10BDCAA,.,2,Page52:,III:Translation,3.试图利用计算机来复制人脑活动方式的数学家们发现，即使运用最先进的电子设备，他们也要建造一台重1万公斤的计算机才行。,4.结果表明，在相当长的时间内，全球平均气温都是相当稳定的，可极小的温度变化却意味着环境的巨大改变。,5.但是，最近发表在科学杂志的一对研究报告并没有验证生物燃料的这种作用。并且，事实上，相对于要被取而代之的化石燃料来说，生物燃料对气候产生的危害是有过之而无不及。,.,3,Page52:,III:Translation,6.尽管备受关注的是研发金属，陶瓷，聚合物与复合材料材质的改善，但有能力生产，制造可以满足特定需求的材料现在也在渐渐变成现实。,7.信息高速公路是一种电子通讯网络，这一网络把所有的人互相联系起来，并可提供任意一种人们想得到的电子通讯方式。,8.如果把管子装成这个样子，使最热的水上升，而最冷的水流下来后返回锅炉里去，那么，锅炉中的热水系统不用水泵就能循环，道理就在于此。,.,4,Page52:,III:Translation,9.多种因素促使人们更加关注(垃圾的处理)/这种兴趣的产生有很多因素，包括对垃圾越来越多，垃圾填埋场地越来越少，焚烧垃圾造成的空气污染越来越严重的担心；及对环境保护的必要性已形成的共识等。,10.无论是用作轿车和公汽的能源，还是发电作其他的什么用途，燃料电池都是无需燃烧就可将氢转化成电能。,.,5,Page52:,III:Translation,11.每个化学元素在周期表中都有一定的原子数和位置，可以据此来推测其特性：如何同别的元素相互作用，能形成什么样的化合物，以及它的物理属性。,12.固体加热到足够温度时，它所含的电子就会有一部分离开固体表面而飞到周围的空间中去；这种现象称为热电子放射；通常，电子管就利用这种现象产生自由电子。,.,6,Page74-75:,II:AbstractCorrection,Thecurrentcalibrationmethodsoftheprojectile-velocitymeasurementsystemareintroduced,andtheproblemandtheunreasonablenessofthesemethodsareanalyzed.Basedontheprincipleofthemathematicalstatistics,thecalibrationmethodisinvestigatedthatmeasurestheprojectile-velocityatthesametimebythemulti-groupzone-blockdeviceisunbiased,uniformandefficientandusestheaverageofthemeasuredvalueasthetruevalueoftheprojectile-velocityatthepoint.,.,7,Page74-75:,II:AbstractCorrection,Themethodadvantagesareanalyzedtoo.Thecalibrationsystemoftheprojectile-velocitymeasurementsystembasedonthelaserscreentargetsisestablished.Theexperimentandthedataprocessprovethatthemethodisnotonlyfeasible,butalsoprovidesaneffectivecalibrationmethodforquantificationally(定量)givingtheuncertaintyofmeasuringtheprojectile-velocityquantitatively.,.,8,Page77-78:,2:Translation机械,a.Aimedatthesystemconsistingofsquareplansifterandflexiblesuspenderattachedtosquareplansifter，therigid-flexiblecouplingdynamicmodelingandthefiniteelementsimulationareemployedtostudyit.ThenonlineardynamicequationofsquareplansifterisestablishedbasedontheLagrangeequation,andthekinematiccirclelawisderivedfromstabilizationcondition.ByusingMSC.Patran/Nastran,thefiniteelementmodelofsquareplansifteriscreatedandthetransientresponseanalysisisapplied.Thetheoreticmodelandtheresultsoffiniteelementsimulationareverifiedbyexperimentaldate.Thedynamicmodelandfiniteelementsimulationmethodpresentedinthispaperpossessanimportantreferencevalueandguidancetointensitycheckoutandstructureoptimizationofsquareplansifter.,.,9,Page77-78:,2:Translation机械,b.Inordertoobtaintheaccurateandefficientsimulationalgorithmfordescribingtherotationofthefuzeballrotor,twokindsofthefuzeballrotorarenumericallysimulatedwiththemathematicalmodelofquaternionasexamples.Runge-KuttamethodandGearmethodareadopted.TheresultsshowthatcomparingwiththenonlinearmathematicalmodelofEulerangles,themodelofquaternionoffuzeballrotorisabletoavoidthesingularitywhenthenutationangleapproaches0or180.ThearithmeticalsolutioncanbeobtainedbyRunge-KuttamethodinsteadofusingtheGearmethodwhichiscomplicatedandmoretime-consumedforcalculation.,.,10,Page82-83:,I.1-7:FTFTTFFII.1.Thatbranchofscientificanalysiswhichdealswithmotions,timeandforcesiscalledmechanics.2.Staticsdealswiththeanalysisofstationarysystems,i.e.,thoseinwhichtimeisnotafactor.3.Dynamicsdealswithsystemswhichchangewithtime.4.Geometryandmechanics.BytheseparationofGeometryfromMechanics,thedeterminationofthemotionfromdynamicalprincipleswillbemademucheasierthanifthetwopartswereundertakenconjointly.ThesetwoaspectsofdynamicswerelaterrecognizedasKinematicsandkinetics,anddealwithmotionandtheforcesproducingit,respectively.,.,11,Page82-83:,5.Kinematicsisthestudyofmotion.Moreparticularly,kinematicsisthestudyofposition,displacement,rotation,speed,velocity,andacceleration.Thestudy,say,ofplanetaryororbitalmotionisalsoaprobleminkinematics.6.Eulerbasedhisseparationofdynamicsintokinematicsandkineticsontheassumptionthattheyshoulddealwithrigidbodies.Itisthisveryimportantassumptionthatallowsthetwotobetreatedseparately.7.Althoughallrealmachinepartsareflexibletosomedegree,machinesareusuallydesignedfromrelativelyrigidmaterials,keepingpartdeflectionstoaminimum.Therefore,itiscommonpracticetoassumethatdeflectionsarenegligibleandpartsarerigid.,.,12,Page82-83:,III.a-d；b-a;c-j;d-b;e-c;f-I;g-f;h-g;i-h;j-eIV.convertmotionfamiliarvariousFurthermoresuitablecombinetechnique,.,13,Page85-86:,I.1.Indimensioningadrawing,nominalsizeisthenumbersplacedinthedimensionlinesthatrepresentdimensionsthatareonlyapproximateanddonotrepresentanydegreesofaccuracyunlesssostatedbythedesigner.2.Inengineeringpractice,apermissibledeviationfromthenominalsizeistermedastolerance.3.Ifthedimensionoftheshaftislowerthanthedimensionofthehole,thentherewillbeclearance.Suchafitistermedclearancefit.4.Ifthedimensionoftheshaftismorethanthatofthehole,thenitistermedinterferencefit.5.Dimensionsgivenclosetolerancesmeansthatthepartmustfitproperlywithsomeotherparts.,.,14,Page85-86:,I.6.Allowanceistheminimumclearancespaceintendedbetweenmatingpartsandrepresentstheconditionofthetightestpermissiblefit.7.Unilateraltolerancemeansthatanyvariationismadeinonlyonedirectionfromthenominalorbasicdimension.Thetolerancewouldbebilateralifitvariesbothoverandunderthenominaldimension.II.Measurement;straight;volumes;irregular;foundation;necessary;instruments;accuracy,.,15,Page85-86:,III,.,16,Page85-86:,IV.1.紧公差的尺寸表示该零件必须与其他零件恰当配合。两者所示公差必须要与设计允差、制造工艺的能力以及获取最大利润的最小生产与转配成本一致。2.容差有时与公差相混淆，两者的意义是完全不同的。容差是在两配合零件间允许的最小间隙，表示配合允许的最紧的状态。3.单向公差允许容差与配合类型不变化的情况下改变公差。而对双向公差来说，如果不改变两个配合零件中的一个或两个的公称尺寸，改变公差是不可能的。,.,17,Page87-88:,I.1.Standardmachinetoolsareusuallygroupedinsixbasicclasses:lathes,drillingmachines,shapers,planers,millingmachines,andgrindingmachines.2.Grinding.Grindingisoneofthemostaccurateofallthebasicmachiningmethods.Agrinderdiffersfromothermachinesinthatitusesatoolmadeofemery,carborundum(金刚砂),orsimilarmaterials.Thewheel,madeupofmanytinycuttingpoints,cutswiththeentiresurfaceareathatcomesincontactwiththematerialbeingground.Grinderscutwithagrindingaction,removingmaterialintheformoftinyparticles.,.,18,Page87-88:,II.车床lathe/turningmachine钻床driller/drillingmachine镗床borer/boringmachine磨床grinder/grindingmachine齿轮加工机床gearcuttingmachine螺纹加工机床threadingmachine铣床miller/millingmachine刨插床planer/shaper拉床broacher/broachingmachine电加工机床electricmachine切割机床cuttingmachineIII.size；blueprints；removing;figures;indicate;modification;belongs;stands;improved,.,19,Page87-88:,IV.1.每一种机床都根据这样的原理来工作：对刀具或者工件施以运动并使两者相接触。然而，每种机床在所采用的运动方式或所应用的方法上，又各不相同。2.旋转的刀具垂直于工件的表面进行连续的切削。多刃刀具旋转与直线进给两种运动合成后，就可以在工件上加工出满足要求的孔。3.砂轮的表面是由许多极小的微刃（砂粒）组成，操作者通过移动工件与砂轮表面接触。,.,20,Page91