下载后可任意编辑新概念英语第四册原文及翻译Lesson7~9新概念英语第四册原文及翻译Lesson7Bats蝙蝠Inwhatwaydoesecho-locationinbatsplayanutilitarianrole?Notallsoundsmadebyanimalsserveaslanguage,andwehaveonlytoturntothatextraordinarydiscoveryofecho-locationinbatstoseeacaseinwhichthevoiceplaysastrictlyutilitarianrole.下载后可任意编辑Togetafullappreciationofwhatthismeanswemustturnfirsttosomerecenthumaninventions.Everyoneknowsthatifheshoutsinthevicinityofawalloramountainside,anechowillcomeback.Thefurtheroffthissolidobstruction,thelongertimewillelapseforthereturnoftheecho.Asoundmadebytappingonthehullofashipwillbereflectedfromtheseabottom,andbymeasuringthetimeintervalbetweenthetapsandthereceiptoftheechoes,thedepthoftheseaatthatpointcanbecalculated.Sowasborntheecho-soundingapparatus,nowingeneraluseinships.Everysolidobjectwillreflectasound,varyingaccordingtothesizeandnatureoftheobject.Ashoaloffishwilldothis.Soitisacomparativelysimplestepfromlocatingtheseabottomtolocatingashoaloffish.Withexperience,andwithimprovedapparatus,itisnowpossiblenotonlytolocateashoalbuttotellifitisherring,cod,orotherwell-knownfish,bythepatternofitsecho.Ithasbeenfoundthatcertainbatsemit下载后可任意编辑squeaksandbyreceivingtheechoes,theycanlocateandsteerclearofobstacles--orlocateflyinginsectsonwhichtheyfeed.Thisecho-locationinbatsisoftencomparedwithradar,theprincipleofwhichissimilar.MAURICEBURTONCuriositiesofanimallifeNewwordsandexpressions生词和短语batn.蝙蝠strictlyadv.明确地utilitarianadj.有用的下载后可任意编辑appreciationn.理解elapsev.障碍物hulln.消逝intervaln.船体receiptn.间隔apparatus下载后可任意编辑n.收到shoaln.仪器herringn.鱼群codn.鳕鱼squeakn.尖叫声参考译文动物发出的声音不都是用作语言交际。我们只要看一看蝙蝠回声定位这一极不寻常的发现，就可以探究一下声下载后可任意编辑音在什么情况下有绝对的有用价值。要透彻理解这句话的意义，我们应先回顾一下人类最近的几项发明。大家都知道，在墙壁或山腰附近发出的喊声，就会听到回声。固体障碍物越远。回声返回所用时间就越长。敲打船体所发了的声音会从海底传回来，测出回声间隔的时间，便可算出该处海洋的深度。这样就产生了目前各种船舶上普遍应用的回声探测仪。任何固体者反射声音，反射的声音因物体的大小和性质的不同而不同。鱼群也反射声音。从测定海深到测定鱼群，这一进展比较容易。根据经验和改进了的仪器，不仅能够确定鱼群的位置而且可以根据鱼群回声的特点分辨出是鲱鱼、鳕鱼，这是人们所熟悉的其他鱼。人们发现，某些蝙蝠能发出尖叫声，并能通过回声来确定并躲开障碍物，或找到它们赖以为生的昆虫。蝙蝠这种回声定位常常可与雷达相比较，其原理是相似的。下载后可任意编辑新概念英语第四册原文及翻译Lesson8Tradingstandards贸易标准Whatmakestradingbetweenrichcountriesdifficult?ChickensslaughteredintheUnitedStates,claimofficialsinBrussels,arenotfittograceEuropeantables.No,saytheAmerican:ourfowlarefine,wesimplycleantheminadifferentway.Thesedays,itisdifferencesinnationalregulations,farmorethantariffs,thatputsandinthewheelsoftradebetweenrichcountries.Itisnotjustfarmerswhoarecomplaining.AnelectricrazorthatmeetstheEuropeanUnion’ssafetystandardsmustbeapprovedbyAmericantestersbeforeitcanbesoldintheUnitedStates,andanAmerican-madedialysismachineneedstheEU’sokaybeforeishitsthemarketinEurope.下载后可任意编辑Asithappens,arazorthatissafeinEuropeisunlikelytoelectrocuteAmericans.So,askbusinessesonbothsidesoftheAtlantic,whyhavetwolotsoftestswhereonewoulddo?Politiciansagree,inprinciple,soAmericaandtheEUhavebeentryingtoreachadealwhichwoul...
