英语六级考试备考晨读美文——Nitinol
<p> <span word="Nitinol">Nitinol</span> <span word="is">is</span> <span word="one">one</span> <span word="of">of</span> <span word="the">the</span> <span word="most">most</span> <span word="extraordinary">extraordinary</span> <span word="metals">metals</span> <span word="to">to</span> <span word="be">be</span> <span word="discovered">discovered</span> <span word="this">this</span> <span word="century">century</span>: <span word="A">A</span> <span word="simple">simple</span> <span word="alloy">alloy</span> <span word="of">of</span> <span word="nickel">nickel</span> <span word="and">and</span> <span word="titanium">titanium</span>, <span word="nitinol">nitinol</span> <span word="has">has</span> <span word="some">some</span> <span word="perplexing">perplexing</span> <span word="properties">properties</span>. <span word="A">A</span> <span word="metal">metal</span> <span word="with">with</span> <span word="a">a</span> <span word="memory">memory</span>, <span word="it">it</span> <span word="can">can</span> <span word="be">be</span> <span word="made">made</span> <span word="to">to</span> <span word="remember">remember</span> <span word="any">any</span> <span word="shape">shape</span> <span word="into">into</span> <span word="which">which</span> <span word="it">it</span> <span word="is">is</span> <span word="fashioned">fashioned</span>, <span word="returning">returning</span> <span word="to">to</span> <span word="that">that</span> <span word="shape">shape</span> <span word="whenever">whenever</span> <span word="it">it</span> <span word="is">is</span> <span word="heated">heated</span>. <span word="For">For</span> <span word="example">example</span>, <span word="a">a</span> <span word="piece">piece</span> <span word="of">of</span> <span word="nitinol">nitinol</span> <span word="wire">wire</span> <span word="bent">bent</span> <span word="to">to</span> <span word="form">form</span> <span word="a">a</span> <span word="circle">circle</span> <span word="that">that</span> <span word="is">is</span> <span word="then">then</span> <span word="heated">heated</span> <span word="and">and</span> <span word="quenched">quenched</span> <span word="will">will</span> <span word="remember">remember</span> <span word="this">this</span> <span word="shape">shape</span>. <span word="It">It</span> <span word="may">may</span> <span word="then">then</span> <span word="be">be</span> <span word="bent">bent</span> <span word="or">or</span> <span word="crumpled">crumpled</span>, <span word="but">but</span> <span word="on">on</span> <span word="reheating">reheating</span>, <span word="will">will</span> <span word="violently">violently</span> <span word="untwist">untwist</span>, <span word="reforming">reforming</span> <span word="its">its</span> <span word="original">original</span> <span word="shape">shape</span>. <span word="This">This</span> <span word="remarkable">remarkable</span> <span word="ability">ability</span> <span word="is">is</span> <span word="called">called</span> <span word="Shape">Shape</span> <span word="Memory">Memory</span> <span word="Effect">Effect</span> ; <span word="other">other</span> <span word="alloys">alloys</span>, <span word="such">such</span> <span word="as">as</span> <span word="brasses">brasses</span>, <span word="are">are</span> <span word="known">known</span> <span word="to">to</span> <span word="possess">possess</span> <span word="it">it</span> <span word="to">to</span> <span word="a">a</span> <span word="limited">limited</span> <span word="extent">extent</span>. <span word="No">No</span> <span word="one">one</span> <span word="fully">fully</span> <span word="understands">understands</span> <span word="SME">SME</span>, <span word="and">and</span> <span word="nitinol">nitinol</span> <span word="remains">remains</span> <span word="particularly">particularly</span> <span word="perplexing">perplexing</span>, <span word="for">for</span>, <span word="whenever">whenever</span> <span word="it">it</span> <span word="performs">performs</span> <span word="this">this</span> <span word="peculiar">peculiar</span> <span word="feat">feat</span>, <span word="it">it</span> <span word="appears">appears</span> <span word="to">to</span> <span word="be">be</span> <span word="breaking">breaking</span> <span word="the">the</span> <span word="laws">laws</span> <span word="of">of</span> <span word="thermodynamics">thermodynamics</span> <span word="by">by</span> <span word="springing">springing</span> <span word="back">back</span> <span word="into">into</span> <span word="shape">shape</span> <span word="with">with</span> <span word="greater">greater</span> <span word="force">force</span> <span word="than">than</span> <span word="was">was</span> <span word="used">used</span> <span word="to">to</span> <span word="deform">deform</span> <span word="it">it</span> <span word="in">in</span> <span word="the">the</span> <span word="first">first</span> <span word="place">place</span>. <span word="But">But</span> <span word="not">not</span> <span word="only">only</span> <span word="is">is</span> <span word="nitinol">nitinol</span> <span word="capable">capable</span> <span word="of">of</span> <span word="remembering">remembering</span>, <span word="it">it</span> <span word="also">also</span> <span word="has">has</span> <span word="the">the</span> <span word="ability">ability</span> <span word="to">to</span> <span word="learn">learn</span>. <span word="If">If</span> <span word="the">the</span> <span word="heating">heating</span>-<span word="cooling">cooling</span>-<span word="crumpling">crumpling</span>-<span word="reheating">reheating</span> <span word="process">process</span> <span word="is">is</span> <span word="carried">carried</span> <span word="out">out</span> <span word="sufficiently">sufficiently</span> <span word="often">often</span>, <span word="and">and</span> <span word="the">the</span> <span word="metal">metal</span> <span word="is">is</span> <span word="always">always</span> <span word="crumpled">crumpled</span> <span word="in">in</span> <span word="exactly">exactly</span> <span word="the">the</span> <span word="same">same</span> <span word="way">way</span>, <span word="the">the</span> <span word="nitinol">nitinol</span> <span word="will">will</span> <span word="not">not</span> <span word="only">only</span> <span word="remember">remember</span> <span word="its">its</span> <span word="original">original</span> <span word="shape">shape</span>, <span word="but">but</span> <span word="gradually">gradually</span> <span word="it">it</span> <span word="learns">learns</span> <span word="to">to</span> <span word="remember">remember</span> <span word="its">its</span> <span word="crumpled">crumpled</span> <span word="form">form</span> <span word="as">as</span> <span word="well">well</span>, <span word="and">and</span> <span word="will">will</span> <span word="begin">begin</span> <span word="to">to</span> <span word="return">return</span> <span word="to">to</span> <span word="the">the</span> <span word="same">same</span> <span word="crumpled">crumpled</span> <span word="shape">shape</span> <span word="every">every</span> <span word="time">time</span> <span word="it">it</span> <span word="is">is</span> <span word="cooled">cooled</span>. <span word="Eventually">Eventually</span>, <span word="the">the</span> <span word="metal">metal</span> <span word="will">will</span> <span word="crumple">crumple</span> <span word="and">and</span> <span word="uncrumple">uncrumple</span>, <span word="totally">totally</span> <span word="unaided">unaided</span>, <span word="in">in</span> <span word="response">response</span> <span word="to">to</span> <span word="changes">changes</span> <span word="in">in</span> <span word="temperature">temperature</span> <span word="and">and</span> <span word="without">without</span> <span word="any">any</span> <span word="sign">sign</span> <span word="of">of</span> <span word="metal">metal</span> <span word="fatigue">fatigue</span>. <span word="Engineers">Engineers</span> <span word="have">have</span> <span word="produced">produced</span> <span word="prototype">prototype</span> <span word="engines">engines</span> <span word="that">that</span> <span word="are">are</span> <span word="driven">driven</span> <span word="by">by</span> <span word="the">the</span> <span word="force">force</span> <span word="of">of</span> <span word="nitinol">nitinol</span> <span word="springing">springing</span> <span word="from">from</span> <span word="one">one</span> <span word="shape">shape</span> <span word="to">to</span> <span word="another">another</span> <span word="as">as</span> <span word="it">it</span> <span word="alternately">alternately</span> <span word="encounters">encounters</span> <span word="hot">hot</span> <span word="and">and</span> <span word="cold">cold</span> <span word="water">water</span>. <span word="The">The</span> <span word="energy">energy</span> <span word="from">from</span> <span word="these">these</span> <span word="remarkable">remarkable</span> <span word="engines">engines</span> <span word="is">is</span>, <span word="however">however</span>, <span word="not">not</span> <span word="entirely">entirely</span> <span word="free">free</span>: <span word="heat">heat</span> <span word="energy">energy</span> <span word="is">is</span> <span word="required">required</span> <span word="to">to</span> <span word="produce">produce</span> <span word="the">the</span> <span word="temperature">temperature</span> <span word="differences">differences</span> <span word="needed">needed</span> <span word="to">to</span> <span word="run">run</span> <span word="the">the</span> <span word="engine">engine</span>. <span word="But">But</span> <span word="the">the</span> <span word="optimum">optimum</span> <span word="temperatures">temperatures</span> <span word="at">at</span> <span word="which">which</span> <span word="the">the</span> <span word="metal">metal</span> <span word="reacts">reacts</span> <span word="can">can</span> <span word="be">be</span> <span word="controlled">controlled</span> <span word="by">by</span> <span word="altering">altering</span> <span word="the">the</span> <span word="proportions">proportions</span> <span word="of">of</span> <span word="nickel">nickel</span> <span word="to">to</span> <span word="titanium">titanium</span>; <span word="some">some</span> <span word="alloys">alloys</span> <span word="will">will</span> <span word="even">even</span> <span word="perform">perform</span> <span word="at">at</span> <span word="room">room</span> <span word="temperature">temperature</span>. <span word="The">The</span> <span word="necessary">necessary</span> <span word="temperature">temperature</span> <span word="range">range</span> <span word="between">between</span> <span word="the">the</span> <span word="warm">warm</span> <span word="and">and</span> <span word="the">the</span> <span word="cold">cold</span> <span word="can">can</span> <span word="be">be</span> <span word="as">as</span> <span word="little">little</span> <span word="as">as</span> <span word="twelve">twelve</span> <span word="degrees">degrees</span> <span word="centigrade">centigrade</span>.</p>
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