研究生機(jī)械工程專業(yè)英語考試必背單詞

單詞Lesson1Gear齒輪,傳動(dòng)裝置Bearing軸承Cams凸輪Camsandfollowers凸輪和從動(dòng)件Couple力偶mechanics力學(xué)statics靜力學(xué)，靜止?fàn)顟B(tài)dynamics動(dòng)力學(xué)，原動(dòng)力，動(dòng)力特性constraintforces約束力appliedforces作用力Electric,magnetic,andgravitationalforces電,磁,重力matingsurface嚙合表面,配合表面,接觸面meshing嚙合，咬合，鉤住meshingteeth嚙合齒journalbearing滑動(dòng)軸承，向心滑動(dòng)軸承metal-to-metalcontact金屬-金屬接觸Overheating過熱failure失效flaking薄片，表面剝落，壓碎Spall削，割，剝落，脫皮noise噪音roughmotion運(yùn)動(dòng)不精確inertia慣性particle質(zhì)點(diǎn)rigidbody剛體deformable可變形的，應(yīng)變的deformableBody變形體Scalar數(shù)量的，標(biāo)量的Vectors矢量Density密度Mass質(zhì)量Displacement位移Velocity速度Acceleration加速度Moment力矩，彎矩Momentum動(dòng)量，沖量Lesson2Compressive壓縮的，有壓力的Turning車削Rectilinear直線的micrometer千分尺又稱螺旋測(cè)微器Powerhacksaws弓鋸床Shaper牛頭刨床Thread螺紋Work：功muscularaction肌肉動(dòng)作mechanicalmotion機(jī)械運(yùn)動(dòng)stretchanobject拉伸對(duì)象tensileforce：拉力intension：受拉compressiveforce：壓力torsionalforce：扭力torque：扭矩shearingforce：剪切力twistanobject扭曲對(duì)象Slide滑，脫落Slip滑動(dòng)，滑移incompression受壓turningofapart對(duì)一個(gè)零件進(jìn)行車削加工wedgingaction:楔入作用chip：切屑centersofthelathe車床的頂尖lathedog車床夾頭centrifugalforce：離心力grindingwheel：磨削砂輪bondingagent：粘合劑abrasiveparticle：磨料顆粒centrifuge-typemachines離心式機(jī)械Centrifuge離心機(jī)，離心作用Centrifugalforceprinciples離心力原理centripetalforce：向心力rotarymotion:回轉(zhuǎn)運(yùn)動(dòng)rectilinearmotion：直線運(yùn)動(dòng)handtool手工工具powertool動(dòng)力工具feed：進(jìn)給shaping：采用牛頭刨床（shaper)進(jìn)行刨削加工powersaw：弓鋸床，弓式鋸床thescrewofamicrometer意為“千分尺中的螺桿”harmonicandintermittentmotion：諧和運(yùn)動(dòng)和間歇運(yùn)動(dòng)simpleharmonicmotion：簡(jiǎn)諧運(yùn)動(dòng)returnstroke：快速回程shaperram：刨床滑枕Pulley滑輪Screw螺絲釘Belt帶Link鏈Lesson3Interactive互相作用的Iterative重復(fù)的,反復(fù)的,迭代的Pinpoint精確地定位或確認(rèn)Equilibrium平衡，均衡Tractable易于處理或操作的Orderofmagnitude數(shù)量級(jí)Ideally理想的情況下soasto為了withanyprecision很少精確idealize理想化idealization理想化strengthofmaterials材料力學(xué)Dynamics動(dòng)力學(xué)Approximations近似值beinherentin為、、、所固有，是、、、的固有性質(zhì)Render提出，給予，描繪degradingtheresult使結(jié)果降級(jí)pertinent有關(guān)prohibitive令人望而卻步Influx流入，注入，涌進(jìn)，匯集Lesson5Sprocket鏈輪snapring卡環(huán)Universaljoints萬向聯(lián)軸器Self-aligningbearing調(diào)心軸承，球面軸承,自位軸承Dryice干冰Shot-peening噴丸硬化處理Pin銷Key鍵Spline花鍵Couplings聯(lián)軸器nondrivingwheel非驅(qū)動(dòng)輪idlergear空轉(zhuǎn)齒輪，換向齒輪besubjectedto承受Fluctuate變動(dòng)，波動(dòng)，起伏alternatingbendingstress交變彎曲應(yīng)力deflections撓度lateralshaftdeflection橫向軸的撓度angulardeflection角偏轉(zhuǎn)non-self-aligningbearings非自調(diào)心軸承Torsionaldeflection扭轉(zhuǎn)變形criticalspeed臨界速度Attachmentofthehub轂的附件Keyway鍵槽Axial軸向Circumferential圓周方向Positioning定位Retaining固定retainingring定位環(huán)hub-to-shaftattachments輪轂與軸之間的連接interferencefit過盈配合hubbore轂孔bendingmoment彎矩cold-rolling冷軋relativeslope相對(duì)傾斜Journal軸頸plainbearing滑動(dòng)軸承Lesson6Clutch離合器Brake制動(dòng)器Friction摩擦Chain鏈，鏈條Timingbelt同步帶Beltdrive帶傳動(dòng)coefficientoffriction摩擦系數(shù)rayon人造纖維timingbelt同步帶V-beltdriveV帶傳動(dòng)Foregoing在前的，前述的fatiguelife疲勞壽命powertransmitted電力傳輸rotatableshaft可以轉(zhuǎn)動(dòng)的軸，從動(dòng)軸rotatingshaft轉(zhuǎn)動(dòng)軸，主動(dòng)軸inputshaft輸入軸outputshaft輸出軸unloadedstate空載狀態(tài)Rotor轉(zhuǎn)子rotationalinertia轉(zhuǎn)動(dòng)慣量torquecapacity扭矩容量kineticandpotentialenergy動(dòng)能和勢(shì)能provision規(guī)定thermalcapacity熱容量thermalstress熱應(yīng)力thermaldistortion熱變形rubbingvelocity摩擦速度Lining內(nèi)襯，襯套empiricalvalue經(jīng)驗(yàn)值Chaindrives鏈傳動(dòng)geardrives齒輪傳動(dòng)speedratio速比shaftseparationdistance軸間隔距離arbitrarycenterdistance任意的中心距Lure吸引，誘惑contractedout.承包出去，訂合同把工作包出去Lesson64Simulator模擬裝置,仿真裝置Terrain地區(qū),地帶Planar平面的marketable銷售closed-loopprocess閉環(huán)過程Factoryautomation工廠自動(dòng)化centraldatabase中央數(shù)據(jù)庫(kù)computer-aideddesigncomputer-aidedmanufacturingcomputer-aidedproductdesign計(jì)算機(jī)輔助產(chǎn)品設(shè)計(jì)computer-aidedanalysis計(jì)算機(jī)輔助分析computer-aideddrafting,計(jì)算機(jī)輔助繪圖designsensitivityanalysis設(shè)計(jì)敏感性分析Optimization最佳化，優(yōu)化modelsimulator模型模擬器substitute替代laboratoryorfieldtest實(shí)驗(yàn)室或現(xiàn)場(chǎng)測(cè)試manufacturability生產(chǎn)能力on-linecontrol在線控制simulate模擬Prototype原型repetitive重復(fù)electricalandelectroniccircuits電氣和電子電路algorithm算法finite-element有限元computationaltechnique計(jì)算技術(shù)multi-bodymechanicalsystem多體機(jī)械系統(tǒng)formulatingtheequation制定公式numericalmethod數(shù)值方法special-purposeprogram專用程序general-purposeprogram通用程序rigidlystructure剛性結(jié)構(gòu)flexibility靈活性planarmotion平面運(yùn)動(dòng)four-barlinkage四連桿機(jī)構(gòu)spatialmotion空間運(yùn)動(dòng)roughterrain崎嶇的地形Connectivity連通性，連接性forceelement力單元governingequation控制方程coordinate協(xié)調(diào)nonlinearity非線性Lesson71Industrialrobot工業(yè)機(jī)器人Printedcircuitboards印刷電路板Shutdown停工，關(guān)閉robotinstallation機(jī)器人安裝single-purposemachines單一用途的機(jī)器InternationalOrganizationforStandardization(ISO)國(guó)際標(biāo)準(zhǔn)化組織（ISO）reprogrammable可重復(fù)編程multipurposemanipulator多功能機(jī)械手RobotInstituteofAmerica(RIA)美國(guó)機(jī)器人協(xié)會(huì)（RIA）JapanIndustrialRobotAssociation(JIRA)日本工業(yè)機(jī)器人協(xié)會(huì)（JIRA）BritishRobotAssociation(BRA)英國(guó)機(jī)器人協(xié)會(huì)（BRA）reprogrammablemultifunctionalmanipulator可重新編程的多功能機(jī)械手multifunctional多功能multifunctional多功能end-effector末端執(zhí)行器articulatedarm關(guān)節(jié)臂articulated關(guān)節(jié)式的，鉸鏈的U.S.AtomicEnergyCommission美國(guó)原子能委員會(huì)Unsophisticated不復(fù)雜的materialshandlingmachine材料搬運(yùn)機(jī)GeneralMotorsCorporation通用汽車公司diecastingmachine壓鑄機(jī)diecasting壓力鑄造，壓鑄Gripper手爪degreesoffreedom(DOF)自由度（DOF）Unimation萬能自動(dòng)化公司jointed-sphericalrobot關(guān)節(jié)式球面機(jī)器人welding,painting焊裝，涂裝inspection檢查fullyautomatedproductionline全自動(dòng)生產(chǎn)線vehiclechassis汽車底盤conveyor輸送帶Assemble組裝asequenceof一序列的Mass-producedprintedcircuitboards(PCBs)大規(guī)模生產(chǎn)的印刷電路板（PCB）pick-and-placerobot拾取和放置機(jī)器人surpassing超越reliability可靠性inflationofwages通貨膨脹的工資imperative勢(shì)在必行，必要的Parting分離的，離別的robotcells機(jī)器人單元dangerzone危險(xiǎn)區(qū)markedoff關(guān)閉標(biāo)記precaution預(yù)防措施shutdownsystem停車系統(tǒng)Setting位置，安裝，環(huán)境翻譯Lesson2Considerableattentionisgiventotheactionofcentrifugalforceingrindingwheels.Thatis,thebondingagentthatholdstheabrasiveparticlesonthewheelmustbestrongerthantheforceswhichtendtomaketherevolvingwheelflyapartathighspeeds.Forthisreason,thespeedofagrindingwheelshouldnotexceedthesafesurfacespeedlimitspecifiedbythemanufacturer.Centrifugalforceincreaseswithspeed.對(duì)磨削用的砂輪來講離心力的影響要特別給以關(guān)注。即把磨料顆粒粘合在砂輪上的粘合劑它的粘合力必須大于使高速旋轉(zhuǎn)的砂輪分崩離析的離心力。因此，砂輪的轉(zhuǎn)速不能超過制造商給定的安全表面速度限制。離心力隨轉(zhuǎn)速的增加而增大。Theprinciplesofcentrifugalforceareusedinthedesignofcentrifuge-typemachines.Somecentrifugesareusedtoseparatechemicals;othersareusedtoremoveimpuritiesinmetalsbycentrifugalcastingprocesses.Centrifugalforceprinciplesarealsousedincommonappliancessuchasclothesdryersandindevicestocontrolmotorspeedsandacceleratemovingmachines.離心力的這種原理用在離心型機(jī)器的設(shè)計(jì)中。一些離心分離機(jī)用于分離化學(xué)制品；還有的通過離心鑄造工藝分離金屬中的雜質(zhì)。離心力作用也有普通的應(yīng)用如干衣機(jī)、控制發(fā)動(dòng)機(jī)轉(zhuǎn)速的裝置以及用于加速運(yùn)動(dòng)的機(jī)器。Centripetalforcecausesanobjecttotravelincircularpath.Thisactioniscausedbythecontinuousapplicationofforceswhichtendtopulltheobjecttothecenter.Inotherwords,theinwardforcewhichresiststhecentrifugalforceiscalledthecentripetalforce.Thecentripetalforceofobjectsspinningataconstantrateproducesanaccelerationtowardthecenterwhichisequalandoppositetothecentrifugalforce.向心力使物體沿著圓形軌道運(yùn)動(dòng)。這種現(xiàn)象的產(chǎn)生是由于將物體拉（軌道）中心的力的持續(xù)作用。換句話說，這種抵抗離心力的向內(nèi)的力就叫向心力。以固定速率作旋轉(zhuǎn)運(yùn)動(dòng)的物體的向心力產(chǎn)生一個(gè)向心的加速度，這個(gè)向心力與離心力大小相等，方向相反。Lesson3Primarily,wewillbediscussingthingswhicharein“equilibrium,”i.e.,notaccelerating.However,ifwelookcloselyenough,everythingisaccelerating.Wewillconsidermanystructuralmemberstobe“weightless”—buttheyneverare.Wewilldealwithforcesthatactata“point”butallforcesactoveranarea.Wewillconsidersomepartstobe“rigid”—butallbodieswilldeformunderload.首先，我們討論的是處于“平衡”狀態(tài)即沒有加速的物體。然而任何東西都在加速，如果我們觀察足夠仔細(xì)的話。我們認(rèn)為很多結(jié)構(gòu)件是“沒有重量”的——但它們從來不是這樣；我們認(rèn)為力的作用在一個(gè)“點(diǎn)”上，——但所有力都作用在一個(gè)區(qū)域上；我們認(rèn)為有些零件是“剛體的”——但所有物體在負(fù)載下都會(huì)變形。Wewillmakemanyassumptionsthatclearlyarefalse.Buttheseassumptionsshouldalwaysrendertheproblemeasier,moretractable.Youwilldiscoverthatthegoalistomakeasmanysimplifyingassumptionsaspossiblewithoutseriouslydegradingtheresult.我們都會(huì)作一些明顯是錯(cuò)誤的假設(shè)。但這些假設(shè)?？赡苁箚栴}簡(jiǎn)化，更容易駕馭。你會(huì)發(fā)現(xiàn)目標(biāo)是只要不使結(jié)果嚴(yán)重降級(jí)（歪曲），就盡可能多的做出簡(jiǎn)化的假設(shè)。Generallythereisnoclearmethodtodeterminehowcompletely,orhowprecisely,totreataproblem:Ifouranalysisistoosimple,wemaynotgetapertinentanswer;ifouranalysisistoodetailed,wemaynotbeabletoobtainanyanswer.Itisusuallypreferabletostartwitharelativelysimpleanalysisandthenaddmoredetailasrequiredtoobtainapracticalsolution.通常沒有明確的方法去確定怎么完整（全面）或精確的去處理問題：如果我們的分析太簡(jiǎn)單，（我們）可能不會(huì)得到一個(gè)中肯的答案；如果我們的分析太詳細(xì)，（我們）也許得不到任何答案。通常更好的是從相對(duì)簡(jiǎn)單的分析開始，添加一些需要的細(xì)節(jié)以獲得實(shí)用解。Duringthepasttwodecades,therehasbeenatremendousgrowthintheavailabilityofcomputerizedmethodsforsolvingproblemsthatpreviouslywerebeyondsolutionbecausethetimerequiredtosolvethemwouldhavebeenprohibitive.Atthesametimethecostofcomputercapabilityandusehasdecreasedbyordersofmagnitude.[5]Weareexperiencinganinfluxof"personalcomputers"oncampus,inthehome,andinbusiness.在過去20年間，用以解決問題的計(jì)算機(jī)方法可用性得到了巨大的提升，過去不能解決是因?yàn)榻鉀Q問題所需要的時(shí)間受到限制。同時(shí)計(jì)算機(jī)的性能成本和使用成本有成數(shù)量級(jí)的降低。我們?cè)谛@里、在家中，在商務(wù)場(chǎng)所都正在經(jīng)歷著一個(gè)“個(gè)人計(jì)算機(jī)”的浪潮。Lesson51.Keepshaftsasshortaspossible,withbearingsclosetotheappliedloads.Thisreducesdeflectionsandbendingmoments,andincreasecriticalspeeds.2.Placenecessarystressraisersawayfromhighlystressedshaftregionsifpossible.[9]Considerlocalsurfacestrengtheningprocesses(asshot-peeningorcold-rolling).[10]3.Useinexpensivesteelsfordeflection-criticalshafts,asallsteelshaveessentiallythesamemodulus.4.Whenweightiscritical,considerhollowshafts.1.保持軸盡可能短，與軸承接近施加的載荷。這減少了變形和彎曲力矩，并增大臨界速度。2.盡可能使必要的應(yīng)力集中源遠(yuǎn)離軸上承受較高應(yīng)力的區(qū)域?？紤]采用局部表面強(qiáng)化工藝（諸如噴丸強(qiáng)化和常溫滾壓）3.使用廉價(jià)的鋼材用于偏轉(zhuǎn)臨界軸，因?yàn)樗械匿摼哂谢鞠嗤膹椥阅Ａ俊?，當(dāng)重量是至關(guān)重要時(shí)，考慮空心軸。Lesson9Theimportanceofrequiringalubricatingfilmcannotbeoveremphasized,evenwhenusingceramicmaterials.[7]Unlubricatedsiliconnitrideorsiliconcarbidedonotinherentlyhavelowfriction,norgoodwearresistance.Thesepropertiescanbeobtainedwiththeaidofsolidlubricantswhicharecompatiblewiththematerials.Siliconnitride,lubricatedforexamplewithgraphitecontaininghightemperatureadditive,canformatribo-chemicalfilmwhichreducesthecoefficientoffrictionand,asaconsequence,minimizesheatgeneration.Thereductioninfrictiondependsontheeasiershearingofthefilmcomparedwiththebasematerial.Forbearingoperationatultra-hightemperatures—above550℃—solidlubricantswhicharemoreheatstablethangraphitearebeingconsidered.Itisimperativethatthedevelopmentofacomplextribologicalsystemsuchasahightemperaturesolidlubricated,ceramicbearingisconductedwithfullunderstandingoftheindividualtribologicalrelationshipofthevariouscomponents.潤(rùn)滑膜的重要性怎么強(qiáng)調(diào)都不過分，即使采用陶瓷材料時(shí)也是這樣。無潤(rùn)滑的氮化硅或碳化硅不固有低的摩擦，也沒有良好的耐磨性。這些性質(zhì)可在固體潤(rùn)滑劑的幫助獲得，這些性質(zhì)與材料相兼容。以氮化硅的潤(rùn)滑為例，用含有高溫添加劑的石墨，可形成摩擦化學(xué)膜從而降低摩擦系數(shù)，結(jié)果，減少熱量的產(chǎn)生。摩擦的減少取決于膜與基材相比誰更容易被切落。對(duì)于工作在超高溫（高于550℃）下的軸承來說比石墨有更好的熱穩(wěn)定性的固體潤(rùn)滑劑正在被考慮。一個(gè)復(fù)雜的摩擦系統(tǒng)的發(fā)展是很有必要的，如高溫固體潤(rùn)滑劑。陶瓷軸承被引入以充分理解各組成部件間的單獨(dú)摩擦關(guān)系。Lesson14Resistancetocorrosiondependsonthecompositionofthematerialandontheparticularenvironment.Corrosivemediamaybechemicals(acids,alkalis['?lk?lis],andsalts),theenvironment(oxygen,moisture,pollution,andacidrain),andwater(freshorsaltwater).[5]Nonferrousmetals,stainlesssteels,andnonmetallicmaterials,generallyhavehighcorrosionresistance.Steelsandcastironsusuallyhavepoorresistanceandmustbeprotectedbyvariouscoatingsandsurfacetreatments.抗腐蝕性取決于材料的成分和特定的環(huán)境。腐蝕媒介可以是化學(xué)品（酸、堿和鹽），環(huán)境（氧、潮濕、污染和酸雨）和水（清水或鹽水）。有色金屬、不銹鋼和非金屬材料通常有高抗腐蝕性。鋼和鑄鐵通常抗腐蝕性差，必須有各種涂層和表面處理保護(hù)。Theusefulnessofsomelevelofoxidation[?ksi'dei??n]isexhibitedinthecorrosionresistanceofaluminum,titanium,andstainlesssteel.Aluminumdevelopsathin(afewatomiclayers),strong,andadherenthard-oxidefilm(Al2O3)thatbetterprotectsthesurfacefromfurtherenvironmentalcorrosion.Titaniumdevelopsafilmoftitanium[tai'teinj?m]oxide(TiO2).Asimilarphenomenonoccursinstainlesssteels,which(becauseofthechromiumpresentinthealloy)developaprotectivefilmontheirsurfaces.Whentheprotectivefilmisscratchedandexposesthemetalunderneath,anewoxidefilmbeginstoform.某些等級(jí)的氧化物的有用性表現(xiàn)在鋁、鈦和不銹鋼的抗腐蝕性上。鋁產(chǎn)生一層薄的（一些原子層）、牢固的附著氧化膜（AL2O3）以保護(hù)表面不進(jìn)一步的腐蝕。鈦產(chǎn)生一層氧化鈦(TiO2）膜。不銹鋼也有相似的現(xiàn)象，（因?yàn)楹辖鹬杏欣樱┍砻娈a(chǎn)生一層保護(hù)膜，當(dāng)保護(hù)膜擦損并露出金屬里層時(shí)，一層新的氧化膜又開始形成了。Lesson28Roughness:thefinestoftheirregularitiesinthesurfacecausedbythemanufacturingprocessusedtosmooththesurface.Roughnessheightismeasuredinmicrometers(μm)ormicroinches(μin).Waviness:awidelyspacedvariationthatexceedstheroughnesswidthcutoffmeasuredininchesormillimeters;roughnessmayberegardedasasurfacevariationsuperimposedonawavysurface.Lay:thedirectionofthesurfacepatterncausedbytheproductionmethodused.Flaws:defectsoccurringinfrequentlyoratwidelyvaryingintervalsonasurface,includingcracks,blowholes,checks,scratches,andthelike;theeffectofflawsisusuallyomittedinroughnessheightmeasurements.粗糙度：由用來使工件表面光滑的加工工藝所造成的最細(xì)微的表面不平度。表面粗糙度的高度采用微米或微英寸作為測(cè)量的單位。波度：是超過粗糙度界限的大間隔偏差，采用英寸或毫米測(cè)量?？蓪⒋植诙瓤醋霪B加在波度表面上的表面不平度。加工紋理方向：由所采用的加工方法所產(chǎn)生的表面刀痕圖案的方向。缺陷：不經(jīng)常出現(xiàn)或者在很大區(qū)間內(nèi)才會(huì)出現(xiàn)的表面瑕疵，包括裂紋、氣孔、微細(xì)裂紋、劃痕等。缺陷的影響通常在粗糙度的高度測(cè)量中被忽略。Lesson62Peopleareenabledtodotheirjobsbetter.Byeliminatingtediouscalculationsandpaperwork-nottomentiontimewastedsearchingforinformation-thecomputernotonlyallowsworkerstobemoreproductivebutalsofreesthemtodowhatonlyhumanbeingscando:thinkcreatively.Computerintegrationmayalsolurenewpeopleintomanufacturing.Peopleareattractedbecausetheywanttoworkinamodern,technologicallysophisticatedenvironment.Inmanufacturingengineering,CAD/CAMdecreasestooldesign,NC-programming,andplanningtimeswhilespeedingtheresponserate,whichwilleventuallypermitin-housestafftoperformworkthatiscurrentlybeingcontractedout.可使人們更好地完成工作。通過避免冗長(zhǎng)的計(jì)算和書寫工作——這還不算查找資料所浪費(fèi)的時(shí)間——計(jì)算機(jī)不僅可以使人們更有效的工作，而且還能把他們解放出來去做只有人類才能做的工作：創(chuàng)造性的思考。計(jì)算機(jī)集成制造還會(huì)吸引新的人才進(jìn)入制造業(yè)。人才被吸引過來的原因是他們希望找到一個(gè)現(xiàn)代化的、技術(shù)先進(jìn)的環(huán)境中工作。在制造工程中，CAD/CAM減少了工藝裝備設(shè)計(jì)、數(shù)控編程和編制工藝規(guī)程所需要的時(shí)間。同時(shí)加快了響應(yīng)速度，這最終將會(huì)使目前外委加工的工作由公司內(nèi)部人員來完成。Lesson71Amajorreasonforthegrowthintheuseofindustrialrobotsistheirdecliningcost.Since1970s,therapidinflationofwageshastremendouslyincreasedthepersonnelcostsofmanufacturingfirms.Inordertosurvive,manufacturerswereforcedtoconsideranytechnologicaldevelopmentsthatcouldhelpimproveproductivity.Itbecameimperativetoproducebetterproductsatlowercostsinordertobecompetitiveintheglobalmarketeconomy.Otherfactorssuchastheneedtofindbetterwaysofperformingdangerousmanufacturingtaskscontributedtothedevelopmentofindustrialrobots.However,thefundamentalreasonhasalwaysbeen,andisstill,improvedproductivity.工業(yè)機(jī)器人成本的降低是促進(jìn)他們的使用量增長(zhǎng)的一個(gè)主要原因。從20世紀(jì)70年代開始，工資的快速增長(zhǎng)大