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February23,2013(HBUTGraduateEnglish)ESTReadingandTranslationPartone:StylisticFeaturesofEST(EnglishforScienceandTechnology)Readingpassageone:AerodynamicsinCarDesignAutomobiledesignersareworkingonwaystobuildautomobilesthatgetgoodgasmileage.Onewaytodothisistomakecarsmorestreamlinedbyreducingdragorwindresistance.Scientistsdefinedragasaforcethatretards,orslows,anobjectthatismovingthroughtheair.Allmovingobjectsaresubjecttodrag.Studiesestimatethatat88kilometersanhour,one-halfofthecar’sfuelandmorethan60percentofthecar’shorsepowerareusedtoovercomedrag.Soifcardesignerscanreducedragtheycanimproveonthecar’sgasmileage,orfuelefficiency.Tofindoutmoreaboutdrag,cardesignersuseengineerswhoarespecialistsinaerodynamics.Aerodynamicsisasciencethatinvolvesthestudyofmovingairandtheforcesthatactonobjectsmovingthroughtheair.Theaerodynamicsspecialistsmeasureairresistanceinunitsindicatingcoefficientofdrag,orCD.Thecoefficientofdragistheratiooftheamountofwindresistanceanobjectencounterstothatofaflatplateofthesameweightheldvertically.AsanexampleofCD,a1.2-by2.4-meterpieceofplywoodheldverticallywouldhaveaCDofabout1.1.OthershapeswouldhavealowerCD.AwatermelonofthesameweightastheplywoodwouldhavealowerCD.AfallingparachutewouldhaveaCDofabout1.3.Incomparison,thetypicalautomobilewouldhaveaCDofabout0.45.WindTunnels:TheBasicToolEngineersusewindtunnelstostudytheCDofautomobiles.Windtunnelsarethebasictoolofaerodynamicresearch.Theyareusedtotestdesignmodels,orsmallerrepresentations,ofbridges,buildings,spacecraft,andmostrecently,automobiles.Awindtunnelcanhaveawidthof12to24metersandbeaslongas275meters.Thetunnelhasaspecialsectionwhereatestmodelisplaced.Theobjecttestedcanbeafull-sizecaroraclaymodeloftherealthing.Ahugefanblowsairintothetestsectionatabout80kilometersanhour.Duringthistimetheaerodynamicspecialistcheckstheareasofthecarwheretheremaybeturbulence,orirregularairmovement.Somespecialistsusepowerfullightstocheckturbulence.Otherengineersusesmoke,smallpieceofpaper,orothervisiblesubstancesinthesameway.T
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