信息與通信工程專業(yè)英語02pa.ppt

第2篇課文 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 這是一個(gè)省略了主語的祈使句 youworkfor 是imagine的賓語 引導(dǎo)該從句的that也被省略掉了 2 Theyhavevalueinthemarketplace oryouwouldnotbedoingit 此句中的主語They指的是上一句的goodsand orservices 而it是指producegoodsand orservices這件事 3 Unfortunately thereisalwaysahumanelementeagertotakeadvantageoftheworkdonebyyouandothers yetwithoutthecustomaryquidproquo1 paymentforservicesrenderedorforproductprovided 本句中的totakeadvantageof是占便宜的意思 而quidproquo為拉丁字 意為補(bǔ)償交換物 4 Moresubtleandshortofdestruction tamperscanalteranyoftheabove presentingtheappearanceoflegitimacythoughtherealityisfalse 本句中的shortof表示無足夠的量 本句為帶有現(xiàn)在分詞短語及though引導(dǎo)的讓步狀語從句的主從復(fù)合句 5 Theftincludessimplytakinginformationnotbelongingtothem whetheractedonornot 此句中有兩個(gè)現(xiàn)在分詞短語 第一個(gè)是takinginformation 它是謂語動(dòng)詞includes的賓語 而第二個(gè)notbelongingto 是現(xiàn)在分詞短語的否定形式 在句中充當(dāng)定語 修飾先行詞information 6 Itincludestheunauthorizeduseofsystemresourcesandisexemplifiedbythetheftoftelephoneservice 此句中的it指的是theft 7 Itisimportanttonotethatmotivationisnotalwaysrelevant 本句中 it是形式上的主語 真正的主語是that引導(dǎo)的一個(gè)主語從句 此處的motivation是指破壞 或作案 的動(dòng)機(jī) GrammarReview 一 定語從句1 Thatsecurityisapeopleproblem that mustbeborneinmindasanunderlyingconstantthemeinanydiscussionofsecurity 二 賓語從句1 KennethWeiss thefounderandchairmanofSecurityDynamics saysthat78percentofcomputerabuseoriginateswithacompany sownemployees 三 強(qiáng)調(diào)句型1 Itispeoplewhocausesecurityproblems notmachinesorsystems 四 短語1 Morecomplexisthetheftofinformationforavarietyofnefariouspurposes toimproveacompetitor sposition tofurtherapoliticalaim todenyyoutimelyaccesstocorrectinformationthatyouneedtosurvive togivetheperpetratoranegohigh 2 Inasense theyaretakingadvantageofourincompleteorineffectivesocialengineering tryingtoreplaceitwiththeirown 3 Nowwearementallypreparedtobegintothinklikeouradversaries 五 多重復(fù)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 本句主句為祈使句 即letus to consider 其中l(wèi)etus已被省略 在letus后面的不定式動(dòng)詞可以略去to 所以謂語動(dòng)詞consider直接用原形 Tounderstand 是不定式動(dòng)詞充當(dāng)目的狀語 其中how引導(dǎo)的從句是understand的賓語 全句應(yīng)譯為 為了理解圖像是如何形成的 讓我們來考慮圖12 1所示的描述 2 NTSC是NationalTelevisionStandardCommittee的縮寫 意為美國國家電視標(biāo)準(zhǔn)委員會(huì) 3 NotethataTVsetdisplaysthesamenumberoflineswhetheritisa5 inchsetor50 inchprojectiontelevisionset 本句為祈使句 謂語動(dòng)詞是note that引導(dǎo)的是它的賓語從句 連詞whether引導(dǎo)的是一個(gè)條件狀語從句 全句含義見參考譯文 4 Thepurposeofdoingsoistoreducethestorageandtransmissioncostswhilemaintaininggoodquality 本句中ofdoingso是介詞短語作定語 修飾purpose maintaininggoodquality是分詞短語 在句中當(dāng)狀語 5 A24 36mm 35mm negativephotographscannedat12 m whichamountsto3 000 2 000pixels assuming8bitsperpixel requires48millionbitsofstorageand 83minutesfortransmission 本句中a24 36mm 35mm 是主句中的主語 scannedat12 m是過去分詞短語作后置定語修飾photograph 而which引導(dǎo)的是一個(gè)非限定性定語從句 補(bǔ)充說明它前面的掃描效果 assuming8bits 是插入的現(xiàn)在分詞短語作狀語 說明amountsto3 000 2 000pixels的前提條件 requires才是主句的謂語動(dòng)詞 全句含義見參考譯文 6 Acolornegativewouldrequirethreetimesthatmuchinstorageandtransmission 本句中的thatmuch指上一句的3000 2000pixels 7 Theadvancementinmicroelectronicsandtheevolutionofmanycommercialapplicationsledtothedevelopmentofstandardsandhardwareforreal timeimagecompression 本句是一個(gè)簡(jiǎn)單句 Theadvancement andtheevolution 是句中的并列主語 GrammarReview1 定語從句 1 Eachelementinthematrixiscalledapictureelement whichisusuallyreferredtoasPELorpixel 2 Forlargersetsthehumaneyeisabletodiscriminatetherasterlinesfromanormalviewingdistance whichisabout10feet 3 A24 36mm 35mm negativephotographscannedat12 m whichamountsto3 000 2 000pixels assuming8bitsperpixel requires48millionbitsofstorageand 83minutesfortransmission 2 狀語從句 1 Althoughtheterm analog isusedindescribingraster scannedimages theimageisanalogonlyalongthehorizontaldirection 2 Ifeachgraylevelisrepresentedas8bits 1byte thenthegraylevelsareallowed28or256possiblevalues 3 介詞短語 1 Theselevelsareusuallyassignedintegervaluesrangingfrom0to255 with0representingthedarkestintensityleveland255thebrightestintensitylevel 此句中的rangingfrom0to255是分詞短語在句中作定語 修飾integervalues with0representing 是介詞短語 在句中也作定語 修飾integervalues 2 Fora24 bitcolorrepresentationperpixel thenumberisdividedintothree8 bitsegments 句中的Fora24 bit 是介詞短語作狀語 說明主句謂語動(dòng)詞的執(zhí)行條件 3 Thefieldofadvancedtelevisiontechnologyendeavorstoprovideuswithdoubletheamountoflinesforabetterresolutioninlarge screentelevisionsets 本句中的withdouble 是介詞短語作狀語 表示provideus的方式 4 Imagecompressionisachievedbyexploitingredundanciesintheimage 本句中的byexploiting 是介詞短語作方式狀語 5 Spectralredundancyisduetocorrelationbetweendifferentcolorplanes 本句中的dueto 是介詞短語作表語 6 Temporalredundancyisduetothecorrelationofdifferentframesinasequenceofimagessuchasinvideoconferencingapplicationsorinbroadcastimages 本句中的dueto 也是介詞短語作表語 4 不定式動(dòng)詞短語 1 Inthenewfieldofadvancedtelevisiontechnologythepurposeistoprovidetheviewerwithdoubletheamountofresolutionofpresent daystandards thusprovidingahigher qualityimage 2 Thepurposeofdoingsoistoreducethestorageandtransmissioncostswhilemaintaininggoodquality 3 Toappreciatetheneedforimagecompression weconsidertheamountofstoragerequiredandthetransmissiontimeusinga9 600 baud bit s modemforthefollowingimages 4 TounderstandhowadigitalimageisformedconsidertheillustrationshowninFig 12 1 5 分詞短語 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