2022年信息科学与电子工程专业英语课后翻译答案

Unit1Exercises(1)TranslatethefollowingsentencesintoChinese.1.2.3.Aswithseriesresonance,thegreatertheresistanceinthecircuitthelowertheQand,accordingly,theflatterandbroadertheresonancecurveofeitherlinecurrentorcircuitimpedance.对于串联谐振,电路中电阻愈大Q值就愈低,相应地线路电流或电路阻抗谐振曲线也就愈平、愈宽。Awirecarryingacurrentlooksexactlythesameandweighsexactlythesameasitdoeswhenitisnotcarryingacurrent.一根带电导线其外表与重量都与不带电导线完全同样。Clickmouseonthewaveformanddragittochangethepulserepetitionrate,ordirectlyenteranewvalueoftheperiodintheprovideddialoguebox,whilekeepingthepulsewidthunchanged.在波形上点击鼠标并拖动来变化脉冲重复频率,或者在提供对话框中直接输入新周期值,而保持脉冲宽度不变。4.Electronicsisthescienceandthetechnologyofthepassageofchargedparticlesinagas,inavacuum,orinasemiconductor.Pleasenotethatparticlemotionconfinedwithinametalonlyisnotconsideredelectronics.电子学是一门关于带电粒子在气体、真空或半导体中运动科学技术。注意,在本书中粒子运动仅限于金属状况不属于电子学。5.6.Hardwaretechnologieshaveplayedvitalrolesinourabilitytouseelectronicpropertiestoprocessinformation,butsoftwareanddataprocessingaspectshavenotdevelopedatthesamespeed.硬件技术在我们使用电子特性来解决信息能力中始终起着重要作用,而软件及数字解决方面却没能与硬件同步发展。However,inaproperlydesignedDCamplifiertheeffectoftransistorparametervariation,otherthanIco,maybepracticallyeliminatediftheoperationpointofeachstageisadjustedsothatitremainsinthelinearoperationrangeofthetransistorastemperaturevaries.然而在设计得当直流放大器中,若调节每一级工作点使之在温度变化时保持在晶体管线性区,就能在事实上消除Ico以外晶体管参数变化所导致影响。Unit2Exercises(1)TranslatethefollowingsentencesintoChinese.1.2.3.Ifanalogsignalsaretobetransmitteddigitally,theyfirsthavetobesampledataspecifiedrateandfurtherconvertedtodiscreteamplitudesamplesbyquantization.如果要以方式传播模拟信号转换为离散幅度样本。,一方面必要以一定频率对信号进行采样,然后通过量化进一步将它们Linearfiltersamplifyorattenuateselectedspatialfrequencies,canachievesucheffectsassmoothingandsharpening,andusuallyformthebasisofre-samplingandboundarydetectionalgorithms.线性滤波器放大或衰减选取空间频率,可以实现像平滑和锐化这些效果,普通是重采样和边沿检测算法基本。Stabilityandrepeatabilityarefundamentalattributesofdigitalcircuits,however,andthenecessaryaccuracycanbeobtainedinadigitalversionofthemodulatorbyanappropriatechoiceofwordlengthtorepresentthesignals.但是稳定性和可重复性是数字电路字长而获得。Thefirstobservationismadeonthefundamentalrelationshipbetweenthenatureofsystem基本性质,在数字式调制器中必要精度可通过恰本地选取代表信号4.andtheperiodicityofitsfrequencyresponse:acontinuoussystemhasanaperiodicfrequencyresponse,

whileadiscretesystemhasaperiodicfrequencyresponse.从系统性质和它频率响应周期性之间基本关系中一方面可以看到:持续系统有非周期性频率响应,而离散系统有周期性频率响应。5.Themainfunctionofthereceiveristoextracttheinputmessagesignalfromthedegradedversionofthetransmittedsignalcomingfromthechannel.接受器重要功能是从由信道传播来退化了信号中提取出输入消息。Unit3Exercises(1)TranslatethefollowingsentencesintoChinese.1.2.Averycommonlyusedmethodofmicrowavemeasurementsisbasedonthestudyofastandingwavepatternformedalongthelinebecauseoftheinterferenceofincidentandreflectedwaves.一种很惯用微波测量办法是基于对驻波图型研究,这种驻波是由入射波和反射波之间干涉而沿着传播线形成。Computationsshowareductionof6dBintheEMfieldintensitywiththedistancedoubled,andanincreaseof3dBintheintensitywiththetransmittedpowerdoubled.Thisresultprovidesverificationtothealgorithmused.计算表白,当距离增大一倍时,电磁场强度减小6分贝;而发射功率增大一倍时,场强则增长3分贝。这一成果验证了所用算法对的性。3.Liketransferofheatbyconduction,convectionandradiation,microwaveheatingcanbeconsideredasanothermodeofheattransfer,inwhichheatisproduceddirectlyatthelocationofthedielectriclosses.就像通过传导、对流、辐射来传递热量同样,微波加热可以看作热传递另一种方式,即热量直接产生于发生介电损耗地方。4.5.Operationoftheradarisbasedonthemeasurementofthetimeittakesforapulsetransmittedfromanantennatogetreflectedbytheobjecttobedetectedandtoreturnattheantennaandthereceiver.雷达工作是基于对天线发出脉冲被所要探测目的反射,(然后)回到天线和接受机所需时间测量。OthermotivationsforusingCADincircuitdesignincludesthewishtoacquireconfidenceinadesignthatwasaccomplishedbyothermeans,and,notleastinimportance,asenseofcuriosityorperhapsadesiretodiscovertheunexpected.在电路设计中使用CAD其他动机涉及:想要验证用设计出来电路;满足好奇心或者也许是想发别办法现预想不到现象。后一种动机并非是最不重要。(获得信心,并非最不重要,意料之外事)6.7.Thespacingbetweentherepeatingamplifiersisafunctionofthecableattenuationandthesystembandwidthsothatthegainprovidedbytheseamplifierscompensatesforthelossintroducedbythecable.中继放大器之间间距是电缆衰减和系统带宽函数,以便这些放大器提供增益补偿电缆引起损耗。Whenthecut-offfrequencyisnolessthanthemaximalfrequencyoftheoriginalsignal,norisitgreaterthanthedifferencebetweenthesamplingfrequencyandthemaximalfrequency,theoriginalsignalmaybecompletelyrebuilt.当截止频率不不大于原始信号最高频率,也不不不大于采样频率和最高频率之差,原始信号可以完整地重建。8.WhilethepoliticsofthelastonehundredyearscenteredaroundIndustrialAgetechnology,thepoliticsofthefuturewillbebasedonInformationAgeconcernsorientedtowardsthestorage,protectionandexchangeofinformation.尽管近百年来政治活动是以工业时代技术为中心,将来政治活动将基于信息时代事物,面向信息存储、保护和互换。

Unit4Exercises(1)TranslatethefollowingpassagesintoChinese.1.Communicationmaybebroadlydefinedasthetransferofinformationfromonepointtoanother.Whentheinformationistobeconveyedoveranydistanceacommunicationsystemisusuallyrequired.Withinacommunicationsystemtheinformationtransferisfrequentlyachievedbysuperimposingormodulatingtheinformationontoanelectromagneticwavewhichactsasacarrierfortheinformationsignal.Thismodulatedcarrieristhentransmittedtotherequireddestinationwhereitisreceivedandtheoriginalinformationsignalisobtainedbydemodulation.Sophisticatedtechniqueshavebeendevelopedforthisprocessbyusingelectromagneticcarrierwavesoperatingatradiofrequenciesaswellasmicrowaveandmillimeterwavefrequencies.However,communicationmayalsobeachievedbyusinganelectromagneticcarrierthatisselectedfromtheopticalrangeoffrequencies.通信可以广义地定义为从一处到另一处信息传递。当要将信息传播到任何距离以外时就需要有一种通信系统。在通信系统内部,信息传播经常通过将信息叠加或调制到作为信号载体电磁波上来实现。经调制载波然后被传送到规定目地,在那里被接受,原始信号通过解调被恢复出来。为了实现这一过程,已经运用工作在射频、微波以及毫米波频率上电磁载波开发了复杂技术。但是通信也可以用光波频段上电磁载波来实现。2.Electroniccommunicationsisthetransferandmovementofdatabetweenlocationsthroughtheuseofcomputers.Anelectroniccommunicationsystemincludestheequipmentneededtosupportthemovementofinformation,thecommunicationlinesandmediatocarrytheinformation,thecomputersoftwareandprogramstocontroltheflowofinformation,thepersonneltoplan,implement,andoperatecommunications,andthemanagementofalltheseresources.Electroniccommunicationsestablisheslinksbetweenpeopleaswellascomputers.电子通信就要设备,承载信息通信对所有这些资源管理。电子通信建立起人和人、计算机和计算机之间联系。是通过使用计算机在不同地点之间传播数据。一种电子通信系统涉及:支持信息流动所需线路和媒介,控制信息流计算机软件和程序,筹、划实行、操作通信系统人员,以及3.Firstgenerationcommunicationssystemscanbecharacterizedbytheuseofanalogtransmissiontechniques,andtheuseofsimplemultiplexaccesstechniquessuchasfrequencydivisionmultipleaccess(FDMA).Theysufferedfromalowusercapacity,andsecurityproblemsduetothesimpleradiointerfaceused.Secondgenerationsystemswereintroducedintheearly1990’s,andallusedigitaltechnology.Thisprovidedanincreaseintheusercapacityofaroundthreetimes,achievedbycompressingthevoicewaveformsbeforetransmission.Thirdgenerationsystemsareanextensiononthecomplexityofsecond-generationsystemsandaretobeintroducedaftertheyear.Thesystemcapacitywillbeincreasedtoovertentimesoriginalfirstgenerationsystems,achievedbyusingcomplexmultiplexaccesstechniquessuchascodedivisionmultiplexaccess(CDMA),oranextensionofTDMA,andbyimprovingflexibilityofservicesavailable.第一代通信系统以模拟传播技术和简朴复用技术如频分复用为特性。这使用简朴无线电接口而存在安全问题。第二代通信系统于20世纪90年代初开始引入,所有前将话音波形压缩使得顾客容量提高了三倍。第三代通信系统是对第二代系统在复杂性方面扩展,预测于后来启用。通过杂复用技术如CDMA或TDMA扩展,并提高服务灵活性些系统顾客容量低,并且由于使用数字技术。通过在传播使用复使得系统容量比本来第一代系统提高10倍。4.Foreachcombinationofcommunication(modulation/detection)type,channelfadingmodel,anddiversitytype,theaveragebiterrorrate(BER)and/orsymbolerrorrate(SER)ofthesystemisobtainedandrepresentedbyanexpressioninaformthatcanreadilybeevaluated.Allcasesconsidered

correspondtorealpracticalchannels,andinmanyinstancestheBERandSERexpressionsobtainedcanbeevaluatednumericallyonahand-heldcalculator.对于通信(调制/检测)类型、信道衰落模型、分集类型每一种组合,得到系统平均误码率(BER)和符号错误率(SER),并以容易求值形式表达。所有考虑相应于实际信道状况,以及许多状况下得到BER和SER表达式均可用手持计算器来计算。5.Modulationisthesystematicvariationofsomeattributeofacarrierwaveformsuchastheamplitude,phase,orfrequencyinaccordancewithafunctionofthemessagesignal.Itisusedincommunicationsystemsformatchingsignalcharacteristicstochannelcharacteristics,forreducingnoiseandinterference,forsimultaneouslytransmittingseveralsignalsoverasinglechannel,andforovercomingsomeequipmentlimitations.Aconsiderableportionofthisbookisdevotedtothestudyofhowmodulationschemesaredeignedtoachievetheabovetasks.Thesuccessofacommunicationsystemdependstoalargeextentonthemodulation.调制是载波波形某些属性,例如幅度、相位和频率,依照消息信号函数有规则变化。它用于通信系统以道上同步传播各种信号,并克服某些设备限制。本使信号特性匹配信道特性,减少噪声和干扰,在单个信书相称大某些内容是研究如何设计调制方案以实现上述任务。一种通信系统成功很大限度上依赖于调制。Unit5Exercises(1)TranslatethefollowingpassageintoChinese.OFDMconsistsofalargenumberofsubcarriersequallyspacedinafrequencyband,eachmaybedigitallymodulatedbyasameschemesuchasPSK,QAM,etc.,orbydifferentschemes.Aseriallytransmittedsequenceisdividedintoanumberofsections,eachhavingNsymbols,andtheNsymbolsineachsectionareusedtomodulateNcarriersforsimultaneoustransmission.ThereforeOFDMisessentiallyaparallelmodulationsystem.Whenthenumberofsubcarriersissufficientlylarge,thesystemcanresistmultipathinterference.Thisisbecausethat,inthetimedomain,asymboldurationlongerthanthemultipathdelaycanbechosen,whileinthefrequencydomain,eachsymbolonlyoccupiesasmallportionofthechannel’sfrequencyband.Thus,theeffectofmultipathfadingspreadsovermanysymbols,resultinginslightdistortiontomanysymbolsratherthancompletedestroyofafewsymbols.Inthisway,correctdemodulationisnotaffectedsothatthesignalcanbeaccuratelyrecoveredatthereceiver.InanOFDMsystem,theprincipleofchoosingthesubcarrierintervalistomakethesubcarriersmutuallyorthogonalwithintheentiresymbolperiod.Thus,evenifspectraloverlapexistsbetweenthesubcarriers,thesymbolscanstillberecoveredwithoutloss.Inordertorealizemaximumspectralefficiency,theintervalbetweensubcarriersisusuallychosentoequalthereciprocalofthesymboldurationT.Thereforethesubcarrierfrequenciesinthebasebandarefn=n/T,(n=0,1,...,N1).Denotingthen-thmodulatingsymbolasX(n),theOFDMwaveformwithinasymboldurationcanbeexpressedas:nTN1x(t)X(n)exp2jt,0tT(1)(2)n0Samplingthiswaveformatt=T/NyieldsN1Xn()exp2kTjnk,k1,2,,N1NN1x(k)Xn()exp2jNn0n0Itisobservedfromtheaboveexpressionthatx(k)andX(n)formadiscreteFouriertransformpair,thereforethebasebandOFDMwaveformcanbegeneratedfromthediscreteFouriertransformofNmodulatingsymbols.WhenN=2mwheremisaninteger,thefastalgorithmofIDFTiseasytoimplement.OFDM由大量在频率上等间隔子载波构成。每个子载波可用同样方案,如PSK,QAM等,或者用不同方案数字调制。将串行传播符号序列提成许多段,每一段有N个符号,每段N个符号被用来分别调制N个载波同步发送。因而,OFDM本质上是一种并行调制系统,当载波数足够大时,这种系统具备抗多径干扰能力。这是由于在时域上符号周期能选获得比多径延迟时间长,而在频域上每个符号只占整个信道带宽一小某些,因而多径衰落影响被分散到许多符号上,其成果是许多符号都发生轻度畸变,而不是使某些符号被完全破坏。这样,不影响对的解调,信号能在接受器中精确地恢复。在OFDM系统中,选取子载波间隔原则,这样。虽然在子载波间存在频谱某些重叠,符号仍能无损失地恢复。为了实现最大频谱效符号周期倒数。因而基带子载波频率为fn=n/T,(n=0,1,...,N1),第n个调制符号记为周期内OFDM波形可表达是使子载波在整个符号周期内互相正交率,子载波之间间隔普通选用为X(n),在一种符号:nN1x(t)X(n)expj2t,0tT(1)Tn0在t=T/N时刻采样这个波形得到:N1kTnk,k1,2,,N1X(n)expj2NNN1x(k)X(n)expj2(2)n0n0从上面表达中可以看到,x(k)和X(n)构成了一对离散傅里叶变换,因而基带OFDM波形可依照N个调制符号离散傅里叶。变换来生成。当N=2m,其中m为整数,IDFT迅速算法很容易实现Unit6Exercises(1)TranslatethefollowingsentencesintoChinese.1.2.3.Communicationisthetransmissionofinformationfromonepointtoanother.Thistransmissionrequirestheabilitytovarysignalswithtimeinamannerwhichisunpredictabletothereceiver.通信就是信息从一点传送到另一点。这种传送规定信号随时间发生变化不能在接受端预测。Itistrueofanycommunicationsystemthattheshapeandamplitudeofthetransmittedsignalwillbecontinuouslydegradedbytheintroductionofnoise,andtheattenuationalongthetransmissionpath.传播信号会不断地被噪声引入和线路上衰减所损伤,对任何通信系统都是如此。Sincetheverybeginning,communicationssystemshaveconsistedofthreemajorparts,namely,theequipment,themedium,andtheprotocol.Itisstillthecasetoday.However,thecloselinkoftelecommunicationswiththecomputertechnologyhasbroughtabouttremendouschangesincommunications,fromtheconcepts,tothecontentsandthemethods.4.5.从一开始通信系统就由设备、媒介和合同三个要素构成。至今依然如此。然算机技术紧密联系使得通信从概念到内容和手段都发生了重大变化。Theavailabilityofsuchalargecollectionofsystemperformancecurvesinasinglecompilationallowstheresearcherorsystemdesignertoperformtrade-offstudiesamongthevariouscommunicationtype/fadingchannel/diversitycombinationssoastodeterminetheoptimumchoiceinthefaceofhisorheravailableconstraints.在一本书中提供如此大量系统性能曲线,使研究者或系统设计者能在各种通信类型、衰落信道、分集佳选。取组合之间进行比较研究,从而在她或她所面临限制之下做出最6.Thechannelprovidestheelectricalconnectionbetweentheinformationsourceandtheuser.Thechannelcanhavemanydifferentformssuchasamicrowaveradiolinkoverfreespace,apairofwires,oranopticalfiber.信道提供信息源和顾客之间电路联接。信道可以有许多不同形式,例如自由空间里微波联接,一对电线,或者一根光纤。7.Thedegradationofthetransmittedsignalisaresultofsignaldistortionduetoimperfectresponseofthechannelandduetoundesirableelectricalsignals(noise)andinterference.Noiseandsignaldistortionaretwobasicproblemsofelectricalcommunication.传播信号退化是信号失真成果,而这种失真又是由信道非抱负响应及不想要电信号(噪声)和干扰引起。噪声和信号畸变是电子通信两个基本问题。Unit8Exercises(1)TranslatethefollowingsentencesintoChinese.1.Earlyinthetwentiethcentury,itwasfoundthatlightcouldcauseatomstoemitelectronsandthat,whenlightreleasedanelectronfromanatom,theenergypossessedbytheelectronverygreatlyexceededthatwhichtheatomcould,accordingtotheelectromagneticwavetheory,havereceived.在二十世纪初期,人们发现光可以使原子放出电子,并且当光从原子中释放一种电子时,电子所包括能量大大超过由电磁波理论得到原子所接受能量。2.3.Pulsebroadeningdeterminestheminimumseparationbetweenadjacentpulses,whichinturndeterminesthemaximuminformation-carryingcapacityoftheopticalfiber.脉冲展宽决定了相邻脉冲之间最小间隔,这一间隔进而又决定了光纤最大信息量容。Ifoneweretotransmitsuchinformationwithoutimpressingitonanopticalcarrierbutinsteadonaradiofrequency(RF)carrierabithigherthanthemaximumrate,thetransmissionwavelengthoftheRFcarrierwouldbecentimetersorlarger.如果传播这样信息不是将它加载到光纤上,而是加载在略高于最大速率射频载波上,则此射频载波就会是厘米波或是波长更长某些波。4.5.6.Thesmallnessoftheopticalwavelength,therefore,allowsfortheminiaturizationoftransmitandreceivemodules,whichshouldallowconsiderablereductioninsize,weight,andcostofopticalcommunicationsystemswithrespecttomicrowave/radiowavecounterparts.光波波长之小使发射和接受模块得以小型化,这就使光通信系统尺寸、重量以至价格与相应微波、无线电波通信系统相比都大为减少。Althoughalltheadvantagesofcoherentopticalcommunicationsystemshaveyettobebroughttofruition,anotherpropertyofopticalradiationhasmadetoday’sopticalcommunicationsystemsnotdesirableforapplications.虽然相干光通信系统所有长处尚有待于贯彻在详细成果中,光辐射另一性质却使当前光通信系统不利于应用。Whencoupledwithlight’sshortwavelengthwhichallowsforminiaturesourcesanddetectorsandmicron-sizedwaveguides,directdetectionschemeshaveallowedforsmall,lightweight,highbandwidthsystemswhicharecompetitiveinmanyareas,mostnotablytothepresenttelecommunicationstransmission,althoughamyriadofotherapplicationsarecontinuallyopeningup.光波长很小,可以使用小型光源和检测器以及微米级波导,于是用直接检测方案可实当前许多领域具备竞争力小巧宽带系统,这些领域中特别引人注目是当前电信传播中应用,尽管无数其她应用也在不断涌现出来。7.Asmentionedpreviously,theseapplicationshavetendedtoopenupmoreslowlythanoriginallypredicted,ascostwasreallynotmuchofaconsiderationintelecommunications,whereequipmentcostsareswampedbyotherconsiderations.如前所述,(线路)成本并非电信系统中真正重要考虑因素,通信设备成本重要受到其她因素制约,因而这些应用比预料浮现得慢。

8.Aswavelengthsdecreasetoapproachthesizeofcircuitcomponents,circuitelementsarenolongerlumpedassuch,andleadscanactasreflectivecomponentsand/orantennasandlumpedelementsaselectromagneticresonators.随着波长减小到接近于电路元件尺寸,电路单元就不再是集总,导线可起到反射元件以及(或)天线作用,集总单元则成为电磁谐振器。Unit11Exercises1.Inatelevisionscanninggeneratorusingapairoffree-runningrelaxationoscillators,free-runningfrequenciesoftheoscillatorsaresetslightlybelowthehorizontalandverticalpulserates,andthestrippedpulsesareusedtotriggertheoscillatorsprematurelyandthustosynchronizethemtothelineandhalf-framerates.在采用一对自由张弛振荡器电视扫描发生器中,振荡器自由频率被设立得略低于水平和垂直(扫描)频率,分离出来脉冲被用来提前触发振荡器从而使它们与行频和半帧频(场频)同步。Unit12Exercises1.2.Referringtothefigure,weseethatsignalprocessingtechniquesareneededforpreprocessing,patternrecognitiontechniquesareneededforsegmentation,featureextraction,andclassification,andartificialintelligencetechniquesareneededforstructureanalysis,knowledge-acquisitionandrepresentation(worldmodel),andcontrolstructure(interactionamongtheblocks).参照图,我们看到信号解决技术是预解决所需要,模式辨认技术是分割、特性提取以及分类所需要,而人工智能技术则是构造分析、知识获取及表达(世界模型)以及控制构造(块间交互)所需要。Thepictureelementsacrossalineareconvertedtothevideosignalandlow-passfilteredwithanelectricalfilter.Thissmoothingremovesthediscretestructureinthehorizontaldimension.沿着一条直线图像像素被转换成视频信号,然后由一种电子滤波器进行低通滤波。这一平滑解决可消除水平方向离散构造。Unit13Exercises(1)TranslatethefollowingsentencesintoChinese.1.2.Theprecedingchaptershavedescribedhowtheautomaticcomputerperforms,buthavenotdescribedhowtheautomaticcomputercanbeputtousetododatahandlingworktoserveanorganization,norwhysuchworkisdoneinthewaythatitis.前面章节讲述了自动计算机是如何工作,但没有讲述自动计算机如何能用于数据解决工作以服务于一种机构,也没有讲述这种工作为什么用这种办法实现。Whilethesubjectofcodingoftencarrieswithitanairofsecrecy,amoreimportantmotiveinmanycodingsystemsistheimprovedefficiencyinconveyinginformation.如果说编码这一主题常带有一种秘密色彩,那么许多编码系统一种更重要目则是为了提高信息传递效率。Unit14Exercises(1)TranslatethefollowingsentencesintoChinese.1.Theimportanceofearlybraindevelopmentinsettingthefoundationsforlanguageisapparentinbabiesyoungerthan6months.大脑初期发展对于奠定语言基本重要性在半年如下婴儿中是显而易见。Unit15Exercises(1)TranslatethefollowingpassageintoChinese.Becausedigitalimageprocessingdoesencompasssuchawidevarietyoftechniquesandmathematicaltools,eachapplicationinvolvesasequenceofprocessingsteps.Thesestepsaremodulesthatcanbe

arrangedinanenormousnumberofdifferentsequences,andeachmodulegenerallyadmitsthespecificationofparametervaluesthatfurtherexpandtherangeofpossiblemanipulationschemestoachievethedesiredresults.Themajoradvantagesofdigitalimagesascomparedwithanalog(i.e.film)imagesarethequalityofthedataandtheaccessibilityofthatdatatocomputermanipulation.Thequalityadvantageisreallyanaggregateoftwoadvantages:Dynamicrange:upto128ormoregraylevelscanbepresentondigitalimageswhereasonly1530discernibleonfilmproducts.Reproducibility:acopyofacopyofacopyofadigitalimagecontainsexactlythesamedataastheoriginal,whereasaforth-generationphotographicproductissubstantiallydegradedincomparisonwiththeoriginal.Althoughtheseareadvantages,thecompellingadvantagefortheapplicationscommunityderivesfromtheaccessibilityofthedatatocomputermanipulation.Togenerateageneral-purposefilmproductisessentiallytochooseacompromiseamongcompetingrequirementsfromagronomists,hydrologists,foresters,geologists,urbanplanners,andotherusergroups;itisnotoptimizedforanyone.Digitalimageslendthemselvestocustomtailoringbytheuserforhisorherapplicationinawaythatfilmproductscannot.数字图像解决涉及了各种各样技术和数学工具,每一项应用都涉及到一系列解决环节。这些环节是以大量不同顺序排列各种模块,每一模块普通容许某些参数值技术指标,从而进一步扩大了为获得预期成果而也许采用解决方案选取范畴。与模拟图像(即胶片)相比,数字图像重要长处在于数据质量和数据可供计算机进行解决这两方面。质量方面优越性事实上是如下两种优越性综合:动态范畴:数字图像可体现128级或更多灰度,而胶片产品只能辨别15至30级;重现性:一幅数字图像多次复制后仍与原件包括完全相似信息,而一幅第四代照片与原件相比却大大地退化(损伤)了。Unit16Exercises(1)TranslatethefollowingsentencesintoChinese.1.2.Inrecentyears,therehasbeenatremendousincreaseintheuseofdigitalcomputersandspecial-purposedigitalcircuitryforperformingvariedsignalprocessingfunctionsthatwereoriginallyachievedwithanalogequipment.近年来为实现各种信号解决功能,数字计算机和专用数字电路使用有了巨大增长,这些解决功能原先都是用模拟设备实现。Inthebeginning,computerswereusedtoprocessonlynumericalinformation,butmajorityofourinformationisnon-numericalinnatureandverylittleisknownaboutitsdescriptionandprocessing.一开始计算机只是被用来解决数值信息,而我们大多数信息都是非数值性质,并且人们对这些信息描述和解决所知甚少。Unit17Exercises(1)TranslatethefollowingpassagesintoChinese.1.Forthefirsttimeeverthelandscapeischanging,ashighvolumepersonalcomputermultimediaapplicationsproliferate.Firstaffectedweremonitors,whichforsometimehaveofferedhigher-than-broadcastspeedandresolution.Onecanexpectcamerastofollow,withhigh-speed,high-resolutiondevicesdrivenbyconsumerdigitalstillcameratechnologyandlower-resolution,ultralowcostunitsdrivenbyentertainment,internetconferencing,andperceptualuserinterfaceapplications.随着大量个人计算机多媒体应用急剧增是显示屏,相称长时间以来它已经可以提供比广播级更高辨别率和速度。人们可期待照相机/摄像机也随之跟上,涉及由民数字照相机所推动高速度、高辨别率器件,娱乐业、互联网远程会议和顾客视觉界面应用所推动低辨别率和极低价格设备IfyoualreadyhavethefastestCPUinaparticularfamilyandstillwantmoreperformance,长,状况初次发生了变化。最早受到影响用。2.

thenitmaybemorecost-effectivetoaddsystemRAMorcacheRAMthantoputinaprocessorfromadifferentfamily.Addingsystemmemorycanbringsignificantperformanceincreasesatarelativelylowcost,assumingyouconfigurethememorycorrectly.InadditiontoaddedcacheandsystemRAM,afasterandlargerharddrivecansaveyoutimewhenrunningapplicationsdependentonheavydriveaccessanddatathroughput.Addingagraphicsacceleratorcardcanhelp,too,especiallyifyouarelookingforawaytostayawakewhileyoursystemredrawsimages.如果你已有了某一系列中最快CPU而还想要更多性能插入一枚另一系列解决器更合算。特别是如果你是一名Windows顾客系统内存可以较低代价带来可观性能提高。除了增长高速缓存或系统RAM,一种更快和更大硬盘可在,如果你使用Windows,并且发现你在寻找某种途径使你在系统重显图象时能保持“苏醒”,则特别是如,那么增长系统RAM或高速缓存RAM也许比,假设你对的地配备内存,则增长运营依赖于大量读写硬盘和有大量数据吞吐时节约你时间。增长一种图形加速器也是有益此。3.Inuniversityenvironments,MATLABhasbecomethestandardinstructionaltoolforintroductorycoursesinappliedlinearalgebra,aswellasadvancedcoursesinotherareas.Inindustrialsettings,MATLABisusedforresearchandtosolvepracticalengineeringandmathematicalproblems.Typicalusesincludegeneralpurposenumericalcomputation,algorithmprototyping,andspecialpurposeproblemsolvingwithmatrixformulationsthatariseindisciplinessuchasautomaticcontroltheory,statistics,anddigitalsignalprocessing(time-seriesanalysis).在大学环境里,它已界,MATLAB被用于研究和解决实际工程和数矩阵公式专门问题解决,这些问题是在自动控制理论、记录、数字信号解决科中提出来。成为应用线性代数导论以及其她领域中许多高档课程原则教学工具。在工业学问题。典型应用涉及通用数值计算、算法原型测试以(时间序列分析)等学及使用4.Multimediaisagenerictermfor“multimediacomputing”or“interactivemultimedia”.Thecomputerandsoftwareareusedtocontrolandnavigatethroughthecommunicationslinks,notonlyoneatthetime,butseveralsimultaneously.Computersystemshavebeenmostdevelopedinusingvisionandhearingtointerfacebetweenthedigitalandanalogueworlds,e.g.,stillandmovingimages,textandgraphicsusethevisualsenses,andaudiouseshearing.Multimediaisdefinedasvisual,audioandtextualinformationwhichcanbepresented,separatelyorsimultaneously,toconveyandpresentinformationinteractivelytousers.Itistechnicallyeasytodigitizetheanalogueformsofthesecommonmediaandhandledbycomputersnowwidelyavailableandinexpensivetobeaccessibletomostusers.多媒体是表达“多媒体计算”或条通信链接同步进行浏览。在运用视觉和听觉在数到极大发展,例如对静止和活动图像、文本和图形使用视觉,对音频使用听觉。多别或同步呈现视频、音频、文本信息,用以交互式地将信息传递和展示给顾客。普通媒体模拟形式用计算机实现数字化并加以解决,计算机当前已十分普遍,其价格便宜,大多数顾客都能使用。Theessentialcapabilityofanymultimediacomputersystemistheabilitytoconvertthe“交互式多媒体”普通术语。计算机和软件被用于控制并通过不止一字和模拟世界之间进行交互方面,计算机系统已媒体被定义为可以得分技术上很容易将这些5.analoguesignaltoadigitalformatandtocompressthisinformationusingstandardalgorithms.ThepoweroftheCPUwilldeterminewhetherthisprocesscanbecarriedoutinreal-timeorwhetherithastobedoneoff-line.OriginallythispoweronlyexistedinUNIXsystems,butmorerecentlyithasbecomeavailableinPCsandMacintosh.Thecompressionprocessisnecessaryotherwisethequantityofdatatobestoredandtransmittedwouldbeexcessive.MostPCshaveuntilrecentlydependeduponhardwareencoding/decodingsystems,butthespeedofcurrentprocessorsissuchthatsoftwarecompressionsystemshavebeendeveloped.Theadvantageofthesoftwaresystemsisthatthecompatibilityandinteroperabilityissuescanbehandledmoreeasily,andthecostoftheequipmentisnotraisedbytheneedtopurchaseexpensive

hardwaredevices.任何多媒体计算机基本功能是将模拟信号转换成数字格式,并用原则算法将此信息压缩能力。CPU解决能力将决定与否能实时完毕此过程还是必要离线执行。原先只有UNIX系统才有这种实时能力,但近年来PC和Macintosh也能胜任(有这种能力)了。压缩是必要,否则要存储和传送数据量太大。直到不久前大多数PC还依赖硬件编解码系统,而当前解决器速度已使软件编解码系统开发成为也许。软件系统长处在于可更以便地解决兼容性和协同工作问题,并且不会因购买昂贵硬件而提高设备成本。Unit19Exercises(1)Translatethefollowing