信息与通信工程专业英语02pa.ppt

第2篇课文 Part3InformationEngineering 信息工程 Unit11InformationSecurityUnit12ImageProcessingUnit13Multimedia Unit11InformationSecurity WhereDoSecurityThreatsComefrom Imagineyouworkforanorganization 1Youproducegoodsand orservices Theyhavevalueinthemarketplace oryouwouldnotbedoingit 2Yourorganizationtooktherisks didtheresearch andmadetheinvestments Youareentitledtothefruitsofyourlabor Unfortunately thereisalwaysahumanelementeagertotakeadvantageoftheworkdonebyyouandothers yetwithoutthecustomaryquidproquo paymentforservicesrenderedorforproductprovided 3 Directtheftofproductsorservicesisasimplemotivation Morecomplexisthetheftofinformationforavarietyofnefariouspurposes toimproveacompetitor sposition tofurtherapoliticalaim todenyyoutimelyaccesstocorrectinformationthatyouneedtosurvive togivetheperpetratoranegohigh Securityisentirelyapeopleissue Itispeoplewhocausesecurityproblems notmachinesorsystems Fortunately ourhigh technologytoolscanalsoservetothwartpeoplewhowoulddousharm justthewaywelockourdoorsagainstintruders Thatsecurityisapeopleproblemmustbeborneinmindasanunderlyingconstantthemeinanydiscussionofsecurity Evenwell intentionedpeopleareaweakpoint Well meaningpeoplewritedownpasswordsorletothersusetheirs Whilewetrytouse socialengineering internallytomodifybehaviorsothatpeoplewillkeepsecurityinmind outsiderstrytousethesameprincipleofsocialengineeringtotalkusersoutofpasswords Inasense theyaretakingadvantageofourincompleteorineffectivesocialengineering tryingtoreplaceitwiththeirown Nowwearementallypreparedtobegintothinklikeouradversaries Ifwecanputourselvesintheirplace thenwecandosomerole playingandbegintoviewoursecurityprecautionsnotjustfromtheinside butfromtheoutside Suchadualperspectiveisessentialtoeffectivesecuritymanagement WhatCanpeopleDotoOurInformation Theycandestroy InformationExecutableprogramsOperatingsystemsOthercomputingorsystemresourcesDestructionincludesbothlogicaldamage tothesysteminvolved and orphysicaldamagetotheequipmentitself Moresubtleandshortofdestruction tamperscanalteranyoftheabove presentingtheappearanceoflegitimacythoughtherealityisfalse 4 Theycansteal InformationServiceHardwareSoftwareTheftincludessimplytakinginformationnotbelongingtothem whetheractedonornot 5Itincludestheunauthorizeduseofsystemresourcesandisexemplifiedbythetheftoftelephoneservice 6Theftplainlyincludesremoval suchasdeletionofinformation aswellasphysicaltransportoffthepremises Theycandisclose InformationtowhichtheyhavenorightorneedInformationtounauthorizedpersonnelforothermotivationsHowtoletothersuseresourcesnotintendedforoutsideuseTheycancauseservicedisruptionsorinterruptions BycausingphysicalorlogicaldamagetothesystemByimproperlydenyingaccesstolegitimateusers Itisimportanttonotethatmotivationisnotalwaysrelevant 7Anyoftheabovelossescanbecausedaccidentally Furthermore theabovecanbecausedasofomission suchasfailingtodoabackup orcommission suchasdeliberatelycausingamalfunction ClassifyingThreatSourcesAthreatisfirstclassifiedasoriginatingfromoutsideorinsidetheorganization Fromthere weproceedtomorespecificsubcategories Externalthreatsinclude HackersCommercialespionageGovernment sanctionedespionageVendorsFormeremployeesInternalthreatsinclude DisgruntledemployeesUnintentionallossesorsecuritybreachesHackers Thebulkofthecaseevidenceshowsthatitistheinternalandnottheexternalthreatthatmustconcernusthemost KennethWeiss thefounderandchairmanofSecurityDynamics saysthat78percentofcomputerabuseoriginateswithacompany sownemployees Evenso instancesofexternalinterferencearegrowing Notes1 Imagineyouworkforanorganization 这是一个省略了主语的祈使句 youworkfor 是imagine的宾语 引导该从句的that也被省略掉了 2 Theyhavevalueinthemarketplace oryouwouldnotbedoingit 此句中的主语They指的是上一句的goodsand orservices 而it是指producegoodsand orservices这件事 3 Unfortunately thereisalwaysahumanelementeagertotakeadvantageoftheworkdonebyyouandothers yetwithoutthecustomaryquidproquo1 paymentforservicesrenderedorforproductprovided 本句中的totakeadvantageof是占便宜的意思 而quidproquo为拉丁字 意为补偿交换物 4 Moresubtleandshortofdestruction tamperscanalteranyoftheabove presentingtheappearanceoflegitimacythoughtherealityisfalse 本句中的shortof表示无足够的量 本句为带有现在分词短语及though引导的让步状语从句的主从复合句 5 Theftincludessimplytakinginformationnotbelongingtothem whetheractedonornot 此句中有两个现在分词短语 第一个是takinginformation 它是谓语动词includes的宾语 而第二个notbelongingto 是现在分词短语的否定形式 在句中充当定语 修饰先行词information 6 Itincludestheunauthorizeduseofsystemresourcesandisexemplifiedbythetheftoftelephoneservice 此句中的it指的是theft 7 Itisimportanttonotethatmotivationisnotalwaysrelevant 本句中 it是形式上的主语 真正的主语是that引导的一个主语从句 此处的motivation是指破坏 或作案 的动机 GrammarReview 一 定语从句1 Thatsecurityisapeopleproblem that mustbeborneinmindasanunderlyingconstantthemeinanydiscussionofsecurity 二 宾语从句1 KennethWeiss thefounderandchairmanofSecurityDynamics saysthat78percentofcomputerabuseoriginateswithacompany sownemployees 三 强调句型1 Itispeoplewhocausesecurityproblems notmachinesorsystems 四 短语1 Morecomplexisthetheftofinformationforavarietyofnefariouspurposes toimproveacompetitor sposition tofurtherapoliticalaim todenyyoutimelyaccesstocorrectinformationthatyouneedtosurvive togivetheperpetratoranegohigh 2 Inasense theyaretakingadvantageofourincompleteorineffectivesocialengineering tryingtoreplaceitwiththeirown 3 Nowwearementallypreparedtobegintothinklikeouradversaries 五 多重复合句1 Fortunately ourhigh technologytoolscanalsoservetothwartpeoplewhowoulddousharm justthewaywelockourdoorsagainstintruders 2 Whilewetrytouse socialengineering internallytomodifybehaviorsothatpeoplewillkeepsecurityinmind outsiderstrytousethesameprincipleofsocialengineeringtotalkusersoutofpasswords 3 Thebulkofthecaseevidenceshowsthatitistheinternalandnottheexternalthreatthatmustconcernusthemost 4 Ifwecanputourselvesintheirplace thenwecandosomerole playingandbegintoviewoursecurityprecautionsnotjustfromtheinside butfromtheoutside Unit12ImageProcessing 1 RepresentationofImagesImagescanhaveeitherdigitaloranalogrepresentation Inthedigitalrepresentationofgray levelimages theimageispresentedasatwodimensionalarrayofnumbers Eachnumberrepresentstheintensityorgrayleveloftheimageatthatrelativeposition Ifeachgraylevelisrepresentedas8bits 1byte thenthegraylevelsareallowed28or256possiblevalues Theselevelsareusuallyassignedintegervaluesrangingfrom0to255 with0representingthedarkestintensityleveland255thebrightestintensitylevel Eachelementinthematrixiscalledapictureelement whichisusuallyreferredtoasPELorpixel Inacolorimage therepresentationissimilar exceptateachlocationofthematrixthenumberrepresentsthreeprimarycolors red greenandblue Fora24 bitcolorrepresentationperpixel thenumberisdividedintothree8 bitsegments Eachsegmentrepresentstheintensityofoneofthecolorprimaries TounderstandhowadigitalimageisformedconsidertheillustrationshowninFig 12 1 1Inthisfigureanimaginarygridisplacedontheimage Thesizeoftheopeningsinthegriddeterminesthesizeofthepixel Thepixel sgraylevelisevaluatedbytheaveragelightintensityateachopeningofthegrid Thefinerthegridsize thehighertheresolution Inthenewfieldofadvancedtelevisiontechnologythepurposeistoprovidetheviewerwithdoubletheamountofresolutionofpresent daystandards thusprovidingahigher qualityimage Fig 12 1Representationofagray leveldigitalimage Intheanalogworld imagesareusuallypresentedashorizontalrasterlines Fig 12 2 Eachlineisbasicallyananalogsignalcarryingthecontinuousvariationsoflightintensitiesalongahorizontallineintheoriginalscene Imagesontelevisionsetsaredisplayedthroughrasterscanning Althoughtheterm analog isusedindescribingraster scannedimages theimageisanalogonlyalongthehorizontaldirection Itisdiscretealongtheverticaldirection andshouldbeconsideredasahybridsignal TelevisionsetsdesignedtoreceivesignalsencodedintheU S NTSC 2standarddisplayapproximately525lines Thefieldofadvancedtelevisiontechnologyendeavorstoprovideuswithdoubletheamountoflinesforabetterresolutioninlarge screentelevisionsets Asethavingascreengreaterthan28inchesisconsideredalarge screenset NotethataTVsetdisplaysthesamenumberoflineswhetheritisa5 inchsetor50 inchprojectiontelevisionset Forlargersetsthehumaneyeisabletodiscriminatetherasterlinesfromanormalviewingdistance whichisabout10feet Fig 12 2Representationofananalogimage 2 ImageDataCompressionImagecompressionistheart scienceofefficientlycodingdigitalimagestoreducethenumberofbitsrequiredinrepresentinganimage Thepurposeofdoingsoistoreducethestorageandtransmissioncostswhilemaintaininggoodquality 4Toappreciatetheneedforimagecompression weconsidertheamountofstoragerequiredandthetransmissiontimeusinga9600 baud bit s modemforthefollowingimages A512 512pixel 8 bit per pixel gray levelimagerequires2097 152bitsforstorageand3 64minutesfortransmission AnRGBcolorimageofthesameresolutionasthepreviouscasewouldrequire 6millionbitsofstorageand 11minutesoftransmissiontime A24 36mm 35mm negativephotographscannedat12 m whichamountsto3000 2000pixels assuming8bitsperpixel requires48millionbitsofstorageand 83minutesfortransmission 5Acolornegativewouldrequirethreetimesthatmuchinstorageandtransmission 6Obviously thestorageortransmissionofafewimageswouldposeaproblem Thereareplentyofotherexamplesthatwouldeasilyjustifyimagecompression andthereforegreatattentionhasbeendirectedtothistopic AnRGBcolorimageofthesameresolutionasthepreviouscasewouldrequire 6millionbitsofstorageand 11minutesoftransmissiontime A24 36mm 35mm negativephotographscannedat12 m whichamountsto3000 2000pixels assuming8bitsperpixel requires48millionbitsofstorageand 83minutesfortransmission 5Acolornegativewouldrequirethreetimesthatmuchinstorageandtransmission 6Obviously thestorageortransmissionofafewimageswouldposeaproblem Thereareplentyofotherexamplesthatwouldeasilyjustifyimagecompression andthereforegreatattentionhasbeendirectedtothistopic Facsimiletransmissionofgraphicdocumentsovertelephonelines archivalstorage medicalimagedatacompression andbroadcasttelevisionaresomeofthemanypotentialapplicationsforimagedatacompression Theadvancementinmicroelectronicsandtheevolutionofmanycommercialapplicationsledtothedevelopmentofstandardsandhardwareforreal timeimagecompression 7 Imagecompressionisachievedbyexploitingredundanciesintheimage Theseredundanciescouldbeeitherspatial spectral ortemporalredundancy Spectralredundancyisduetocorrelationbetweendifferentcolorplanes Temporalredundancyisduetothecorrelationofdifferentframesinasequenceofimagessuchasinvideoconferencingapplicationsorinbroadcastimages Notes1 Tounderstandhowadigitalimageisformed letus considertheillustratinshowninFig 12 1 本句主句为祈使句 即letus to consider 其中letus已被省略 在letus后面的不定式动词可以略去to 所以谓语动词consider直接用原形 Tounderstand 是不定式动词充当目的状语 其中how引导的从句是understand的宾语 全句应译为 为了理解图像是如何形成的 让我们来考虑图12 1所示的描述 2 NTSC是NationalTelevisionStandardCommittee的缩写 意为美国国家电视标准委员会 3 NotethataTVsetdisplaysthesamenumberoflineswhetheritisa5 inchsetor50 inchprojectiontelevisionset 本句为祈使句 谓语动词是note that引导的是它的宾语从句 连词whether引导的是一个条件状语从句 全句含义见参考译文 4 Thepurposeofdoingsoistoreducethestorageandtransmissioncostswhilemaintaininggoodquality 本句中ofdoingso是介词短语作定语 修饰purpose maintaininggoodquality是分词短语 在句中当状语 5 A24 36mm 35mm negativephotographscannedat12 m whichamountsto3 000 2 000pixels assuming8bitsperpixel requires48millionbitsofstorageand 83minutesfortransmission 本句中a24 36mm 35mm 是主句中的主语 scannedat12 m是过去分词短语作后置定语修饰photograph 而which引导的是一个非限定性定语从句 补充说明它前面的扫描效果 assuming8bits 是插入的现在分词短语作状语 说明amountsto3 000 2 000pixels的前提条件 requires才是主句的谓语动词 全句含义见参考译文 6 Acolornegativewouldrequirethreetimesthatmuchinstorageandtransmission 本句中的thatmuch指上一句的3000 2000pixels 7 Theadvancementinmicroelectronicsandtheevolutionofmanycommercialapplicationsledtothedevelopmentofstandardsandhardwareforreal timeimagecompression 本句是一个简单句 Theadvancement andtheevolution 是句中的并列主语 GrammarReview1 定语从句 1 Eachelementinthematrixiscalledapictureelement whichisusuallyreferredtoasPELorpixel 2 Forlargersetsthehumaneyeisabletodiscriminatetherasterlinesfromanormalviewingdistance whichisabout10feet 3 A24 36mm 35mm negativephotographscannedat12 m whichamountsto3 000 2 000pixels assuming8bitsperpixel requires48millionbitsofstorageand 83minutesfortransmission 2 状语从句 1 Althoughtheterm analog isusedindescribingraster scannedimages theimageisanalogonlyalongthehorizontaldirection 2 Ifeachgraylevelisrepresentedas8bits 1byte thenthegraylevelsareallowed28or256possiblevalues 3 介词短语 1 Theselevelsareusuallyassignedintegervaluesrangingfrom0to255 with0representingthedarkestintensityleveland255thebrightestintensitylevel 此句中的rangingfrom0to255是分词短语在句中作定语 修饰integervalues with0representing 是介词短语 在句中也作定语 修饰integervalues 2 Fora24 bitcolorrepresentationperpixel thenumberisdividedintothree8 bitsegments 句中的Fora24 bit 是介词短语作状语 说明主句谓语动词的执行条件 3 Thefieldofadvancedtelevisiontechnologyendeavorstoprovideuswithdoubletheamountoflinesforabetterresolutioninlarge screentelevisionsets 本句中的withdouble 是介词短语作状语 表示provideus的方式 4 Imagecompressionisachievedbyexploitingredundanciesintheimage 本句中的byexploiting 是介词短语作方式状语 5 Spectralredundancyisduetocorrelationbetweendifferentcolorplanes 本句中的dueto 是介词短语作表语 6 Temporalredundancyisduetothecorrelationofdifferentframesinasequenceofimagessuchasinvideoconferencingapplicationsorinbroadcastimages 本句中的dueto 也是介词短语作表语 4 不定式动词短语 1 Inthenewfieldofadvancedtelevisiontechnologythepurposeistoprovidetheviewerwithdoubletheamountofresolutionofpresent daystandards thusprovidingahigher qualityimage 2 Thepurposeofdoingsoistoreducethestorageandtransmissioncostswhilemaintaininggoodquality 3 Toappreciatetheneedforimagecompression weconsidertheamountofstoragerequiredandthetransmissiontimeusinga9 600 baud bit s modemforthefollowingimages 4 TounderstandhowadigitalimageisformedconsidertheillustrationshowninFig 12 1 5 分词短语 1 Eachlineisbasicallyananalogsignalcarryingthecontinuousvariationsoflightintensitiesalongahorizontallineintheoriginalscene 2 TelevisionsetsdesignedtoreceivesignalsencodedintheU S NTSC 2standarddisplayapproximately525lines Unit13Multimedia Contemporarymultimediaisdefinedasthedevelopment integration anddeliveryofanycombinationoftext graphics animation sound orvideothroughacomputer Thekeyterminthisdefinition theonethattransformstraditionandproduces newmedia is computer Thedigitalcomputerdisplacedtraditionaltechniquesforcreatingandeditingallformsofmedia Word processingdisplacedthetypewriter theCDtransformedsoundandmusicproduction anddigitalcamerasandeditingsoftwarearereplacingfilmandthedarkroom Thereasonforthistransformationissimple computerscannowcreatemediathatrivalthequalityoftraditionalproductsandtheycandosomoreefficientlyandmoreeconomically Analogmedia liketraditionalcraftsmanship willcontinuetoexist buttheirdominanceinthemarketplaceisatanend Mostmediaprofessionalsarebuildingtheircareerswithdigitaltechnology Themultimediarevolutionisnotjustaboutperformingtraditionaltasksinnewways Itisalsoaboutcreatingnewapproachestocommunication commerce education andentertainment Cellphonesbecometextmessengers cameras andvideodisplays 1 E commercegivesshoppersinstantaccesstocountlessproductsandservicescompletewithpictures demos reviews andpricecomparisons Classroomslosetheirwallsasdigitalmedia graphics animation sound andvideo streamthroughelectronicnetworks 2Newformsofentertainment suchaspodcasts videogames onlinepokertournaments andinteractivefilm havetransformedthatindustryaswell 3Inthesecases andinmanymore digitalmultimediaischangingtheworldbymakingitpossibleforuserstointeractwithinformationinnewways Themultimediarevolutionisnotjustaboutperformingtraditionaltasksinnewways Itisalsoaboutcreatingnewapproachestocommunication commerce education andentertainment Cellphonesbecometextmessengers cameras andvideodisplays 1E commercegivesshoppersinstantaccesstocountlessproductsandservicescompletewithpictures demos reviews andpricecomparisons Classroomslosetheirwallsasdigitalmedia graphics animation sound andvideo streamthroughelectronicnetworks 2 Newformsofentertainment suchaspodcasts videogames onlinepokertournaments andinteractivefilm havetransformedthatindustryaswell 3Inthesecases andinmanymore digitalmultimediaischangingtheworldbymakingitpossibleforuserstointeractwithinformationinnewways Soimportantarethesenewformsofinteractivitythatmultimediaapplicationsareoftendifferentiatedbasedonthedegreeandqualityofinteractiontheysupport 4Someapplicationsaredesignedtoallowlittleornointeractivity othersencourageasmuchinteractionaspossible Innon interactivemultimedia theuserhasnocontrolovertheflowofinformation Aninformationkioskatamuseummightregularlyrepeataseriesofslidesdescribingtheday sevents Suchapplicationsareoftenasimpleandeffectivewaytodrawattentiontoannouncements products orserviceswithoutrequiringanyactiononthepartontheviewer Ininteractivemultimedia usersareabletocontroltheflowofinformation Thereareseveraltypesofinteractivemultimedia Thefirstprovidesbasicinteractivity Basicinteractionsincludemenuselections buttonstoadvancescreens VCR likecontrols clickableobjects links andtextboxesforquestionsorresponses Hypermediaisamoreadvancedformofinteractivemediainwhichthedeveloperprovidesastructureofrelatedinformationandthemeansforausertoaccessthatinformation Anonlineanatomytutorial forexample organizesinformationbasedonphysiologicalrelationshipsandmayenhanceauser sunderstandingthroughhyperlinkstorelatedtext drawings animations orvideo Stillmoreadvancedformsofinteractivemultimediaadaptthepresentationofinformationtotheneedsortheinterestsofusers Theseapplicationsembodyaspectsofintelligenceanddecision makingandaredescribedasadaptivemultimediaorintellimedia 5Therangeoftheseformsofmultimediaislikelytoexpandsignificantlywithcontinueddevelopmentinanothermajorareaofcomputerresearch artificialintelligence 6Anotherpowerfulformofmultimediainteractivityisfoundinadvancedsimulationsandgamesthatcreatetheirownvirtualreality Virtualrealitiesarenotsimplyresponsivetousers theyareimmersive Animmersivemultimediaapplicationdrawsitsusersintoanalternateworld engagingthemintellectually emotionally andevenviscerally 7Advancedflightsimulatorssothoroughlyimmersepilotsinaworldofvirtualflightthattheyroutinelyserveassubstitutesfortraininginactualaircraft Videogamescandrawplayersintootherworldsforhoursorevendaysonend Multimediawillcontinuetoshapeourworld andeachofuscanbene