職稱英語(yǔ)考試真題閱讀判斷

經(jīng)典word整理文檔，僅參考，雙擊此處可刪除頁(yè)眉頁(yè)腳。本資料屬于網(wǎng)絡(luò)整理，如有侵權(quán)，請(qǐng)聯(lián)系刪除，謝謝！職稱英語(yǔ)考試真題閱讀判斷NewUnderstandingofNaturalSilk’sMysteriesNaturalsilk,asweallknow,hasastrengththatmanmadematerialshavelongstruggledtomatch.InadiscoverythatsoundsmorelikeanancientChineseproverbthanamaterialssciencebreakthrough,MITresearchershavediscoveredthatsilkgetsitsstrengthfromitsweakness.Or,morespecifically,itsmanyweaknesses.Silkgetsitsextraordinarydurabilityandductilityfromanunusualarrangementofhydrogenbondsthatareinherentlyveryweakbutthatworktogethertocreateastrong,flexiblestructure.Mostmaterials--especiallytheonesweengineerforstrength--gettheirtoughnessfrombrittleness.Assuch,naturalsilkslikethoseproducedbyspidershavelongfascinatedbothbiologistsandengineersbecauseoftheirlightweight,ductilityandhighstrength(poundforpound,silkisstrongerthansteelandfarlessbrittle).Butonitsface,itdoesn'tseemthatsilksshouldbeasstrongastheyare;molecularly,theyareheldtogetherbyhydrogenbonds,whicharefarweakerthanthecovalentbondsfoundinothermolecules.Togetabetterunderstandingofhowsilkmanagestoproducesuchstrengththroughsuchweakbonds,theMITteamcreatedasetofcomputermodelsthatallowedthemtoobservethewaysilkbehavesattheatomiclevel.Theyfoundthatthearrangementofthetinysilknanocrystalsissuchthatthehydrogenbondsareabletoworkcooperatively,reinforcingoneanotheragainstexternalforcesandfailingslowlywhentheydofail,soasnotsoallowasuddenfracturetospreadacrossasilkstructure.Theresultisnaturalsilksthatcanstretchandbendwhileretainingahighdegreeofstrength.Butwhilethat'sallwellandgoodforspiders,beesandthelike,thisunderstandingofsilkgeometrycouldleadtonewmaterialsthatarestrongerandmoreductilethanthosewecancurrentlymanufacture.Ourbestandstrongestmaterialsaregenerallyexpensiveanddifficulttoproduce(requiringhightemperaturetreatmentsorenergy-intensiveprocesses).Bylookingtosilkasamodel,researcherscouldpotentiallydevisenewmanufacturingmethodsthatrelyoninexpensivematerialsandweakbondstocreatelessrigid,moreforgivingmaterialsthatarenonethelessstrongerthananythingcurrentlyonoffer.Andifyouthoughtyouweregoingtogetoutofthismaterialssciencestorywithouthearingaboutcarbonnanotubes,thinkagain.TheMITteamisalreadyinthelablookingintowaysofsynthesizingsilk-likestructuresoutofmaterialsthatarestrongerthannaturalsilk--likecarbonnanotubes.Super-silksareonthehorizon.參考譯文：我們都知道，蠶絲具有的韌性是人造織物長(zhǎng)期奮力追求的目標(biāo)。在一項(xiàng)研究中(該項(xiàng)研究成果聽起來更像一則古代中國(guó)諺語(yǔ)，而不是材料科學(xué)的突破)，麻省理工學(xué)院的研究人員發(fā)現(xiàn)，蠶絲的力量源于其脆弱，或者，更具體地說，是它的多方面的脆弱。蠶絲的異常耐久性和延展性來自一種特別的氫鍵結(jié)構(gòu)，這些氫鍵本質(zhì)上非常脆弱，但它們共同創(chuàng)造了一種強(qiáng)壯而富有彈性的結(jié)構(gòu)。大多數(shù)材料(特別是那些要求硬度很高的材料)的韌性來自脆性。因此，和蜘蛛制造的蛛絲類似的蠶絲，因其重量輕，延展性強(qiáng)和韌性高，長(zhǎng)期以來引起了生物學(xué)家和工程師的興趣(同樣重量，蠶絲比鋼要壯，也不那么脆)。但表面上，蠶絲看起來卻不那么強(qiáng)壯;從分子結(jié)構(gòu)上看，它們是由氫鍵組成的，氫鍵比其他分子中發(fā)現(xiàn)的共價(jià)鍵要脆弱得多。為了更好地了解蠶絲如何以如此脆弱的化學(xué)鍵產(chǎn)生這么強(qiáng)壯的力，麻省理工學(xué)院的研究小組創(chuàng)造了一套計(jì)算機(jī)模型，這種模型能夠讓他們?cè)谠訉哟紊嫌^察蠶絲的'活動(dòng)方式。他們發(fā)現(xiàn)，微小蠶絲納米晶體的結(jié)構(gòu)使氫鍵能夠齊心協(xié)力地合作，相互增援，對(duì)抗外力，同時(shí)，當(dāng)外力減弱時(shí)也隨之慢慢減弱，這樣就不至于在蠶絲的整體結(jié)構(gòu)上出現(xiàn)突然的斷裂。這樣，天然絲能夠既伸縮和彎曲，又能夠保持極高的韌力。對(duì)于蜘蛛和蜜蜂之類的昆蟲來說這也沒什么，但對(duì)于蠶絲幾何形狀的這種了解，可能幫助人們制造出比我們面前能夠制造的材料更結(jié)實(shí)而又更柔軟的新材料。最好和最結(jié)實(shí)的材料通常是很昂貴而又難以制造的(需要高溫處理，或者高能耗處理)。通過研究蠶絲作為一個(gè)例子，研究人員有可能設(shè)計(jì)出制造材料的一種新方法，即用廉價(jià)材料和弱鍵，制造不那么堅(jiān)硬而又柔軟，但比目前所用的任何材料都結(jié)實(shí)的材料。如果你認(rèn)為不研究碳納米管的理論，就能從這一則材料學(xué)信息中獲取制造方法，那請(qǐng)三思。麻省理工學(xué)院研究小組已經(jīng)在實(shí)驗(yàn)室利用比蠶絲還結(jié)實(shí)的材料(比如碳納米管)研究合成類似蠶絲一樣的結(jié)構(gòu)。超級(jí)蠶絲即將出現(xiàn)。16.MITresearcherscarryoutthestudytoillustrateanancientChineseproverb.A.RightB.WrongC.Notmentioned17.Silk’sstrengthcomesfromitsweakhydrogenbondsworkingtogether.A.RightB.WrongC.Notmentioned18.Biologistandengineerareinterestedinunderstandingnaturalsilksbecausetheyareverylightandbrittle.A.RightB.WrongC.Notmentioned19.Ifthehydrogenbondsbreakduetoexternalforces,theybreakfast.A.RightB.WrongC.Notmentioned20.TheMITteamhadtrieddifferentmaterialsbeforetheystudiednaturalsilkintheirresearch.A.RightB.WrongC.Notmentioned21.Carbonnanotubesarecurrentl