消防报警和安全检测 外文文献翻译Word下载.docx

消防报警和安全检测 外文文献翻译Word下载.docx

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消防报警和安全检测外文文献翻译@#@FireAlarmsandSecurityDetection@#@Afirealarmcircuit,asitsnameimplies,soundsanalarmintheeventofafire.Therecanbeoneorseveralalarmsthroughoutabuilding,andtherecanbeseveralalarmpoints,whichactivatethewarming.Thealarmpointscanbeoperatedmanuallyorautomatically;@#@inthelattercasetheymaybesensitivetoheat,smokeorionization.Thereareclearlymanycombinationspossible,andthischaptergivessomesystematicaccountofthewaytheyarebuiltup.@#@Severalalarmpointsareconnectedinparallel,andwheneveroneofthemisactuatedthecircuitiscompletedandthealarmsounds.Thisisdescribedasanopencircuit,anditwillbeseenthatitisnotfailsafe,becauseifthereisafailureofsupply,thefirealarmcannotwork.Anothercharacteristicofthiscircuitisthateveryalarmpointmustbecapableofcarryingthefullcurrenttakenbyallthebellsorhootersworkingtogether.@#@Thealarmpointsareconnectedinserieswitheachotherandwitharelaycoil.Therelayisnormallyclosedwhende-energized,andopenswhenthecoilisenergized.Thuswhenanalarmpointisactivatedtherelaycoilisde-energized,therelayclosesandthealarmsounds.Thissystemfailssafetotheextentthatifthecoilcircuitfailsthemaincircuitoperatesthealarm.Itisnotofcoursesafeagainsttotalfailureofthesupplybecauseinthateventthereisnosupplyavailabletoworkthebells.Thealarmpointsdonothavetocarrytheoperatingcurrentofthebellsorhooters.Thisarrangementiscalledaclosedcircuitincontrasttotheopencircuit.Wecannoticethatinanopencircuitthealarmpointsarewiredinparallelandarenormallyopen,whilstinaclosedcircuittheywiredinseriesandarenormallyclosed.@#@Atypicalmanuallyoperatedfirealarmpointiscontainedinarobustredplasticcasewithaglasscover.Thematerialischosenforitsfireresistingproperties.Thecasehasknockoutforconduitentriesattopandbottombutthematerialcanbesufficientlyeasilycutforthesiteelectriciantomakehimselfanentryinthebackifheneedsit.Alternativeterminalsareprovidedforcircuitsinwhichthecontactshavetoclosewhentheglassissmashedandforcircuitsinwhichthecontactshavetoopenwhentheglassissmashed.Intheformercase,thereisatestswitchwhichcanbereachedwhenthewholefrontisopenedwithanAllenKey.Inthelattercase,thetestpushisomittedbecausethecircuitisinanycaseofthefailsafetype.Thealarmpointillustratedissuitableforsurfacemounting.Similaronesareavailableforflushfixingandinweatherproofversions.Thecurrentcarryingcapacityofthecontactsshouldalwaysbecheckedwiththemaker'@#@scatalogue.@#@Athermallyoperatedalarmpointconsistsofabi-metalstripthatdeflectswhenthetemperaturerises,andtherebytiltsatubehalffullofmercury.Whenthetubetiltsthemercuryflowsintotheotherhalfofthetubewhereitcompletesthecircuitbetweentwocontactspreviouslyseparatedbyair.Alternatively,thearrangementwithinthetubecanbesuchthatthemercurybreaksthecircuitwhenthetubeistilted.Thecasingofthealarmisofstainlesssteel.Heatdetectorsofthistypeareusuallysettooperateat65℃.Theyarefrequentlyusedinboilerhouses.@#@Asmokeoperatedalarmpointwouldbeusedonlyinspecialcircumstanceswhichmakeitnecessarytodetectsmokeratherthanheat.Thistypecancausenuisanceoperationofthealarmbyreactingtosmallquantitiesofsmokewhichhavenotbeencausedbyafire;@#@theyhaveforexamplebeenknowntosoundthealarmasaresultofcigarettesmokeinanoffice.Modernoneshaveadjustablesensitivitysothattheycanbesettoavoidnuisanceoperation.@#@Anionizationdetectorcontainsachamberwhichhousessomelowstrengthradioactivematerialandapairofelectrodes.Theradioactivematerialmakestheairinthechamberconductivesothatasmallcurrentflowsbetweentheelectrodes.Thesizeofthecurrentvarieswiththenatureofthegasinthechamberandassoonasanycombustion.Productsareaddedtotheairthereisasuddenchangeinthecurrentflowing.Thedetectoralsohasasecondchamberwhichispermanentlysealedsothatthecurrentthroughitneverchanges.Aslongasthecurrentsthroughthetwochambersareequalthereisnooutput,assoonastheybecomeunbalancedthereisanetoutputwhichisusedtooperateatransistorswitchinthemaincircuitthroughthedetector.@#@Thehumanbeingisthemostefficientfiredetector,providedthatheisactuallythereatthetime.Thecombinationofhiseyes,earsandnoseallowshimtodifferentiatebetweenvariousphenomena.Hecansmellthedifferencebetweencigarettesmoke,burningtoastandsomethingmoresinistersuchasburningpaper.Hecanseesmokeandflamesandwilloftenhearafirebeforehehasnoticedeithertheflamesorthesmoke.Sometimes,thefirstthinghenoticesisheat,forexample,ahotpartitionwall.Itisthesephenomenathatfiredetectordesignersmeasuretodetecttheonsetoffire.Itistheonsetoffirethatiscrucial;@#@verysmallfirescanbeputoutquicklyandsafelywithportablefireextinguishers,orevenacupofcoffeeifdetectedsoonenough.Obviously,thesmallerthefire,thelessitmaybeobserved.Firedetectorsmust,therefore,bedesignedwithouttheriskoffalsealarms.Sowhattechnologyisusedtodaytodetectthesephenomena?

@#@@#@Twotechniquesareusedforthedetectionofsmoke:

@#@photoelectricsmokedetectorsandionizationsmokedetectors.Photoelectricdetectorsarearrangedsothat,althoughvisiblelightcannotenter,smokecanenterfreely.Thistypeofdetectorisbasedonamattblackchamberaboutthesizeofacoffeecup.Adividingwallisplacedinthemiddleofthechamberoneithersideofwhichislocatedalighttransmitterandalightreceiver.Undernormalcircumstances,lightfromthetransmitterisnotreceivedbythereceiver,asthechamberisnotreflective.Whensmokeparticlesenterthechamber,lightbouncesofftheseparticleswhichresultsinasignalbeingreceived.Asimilareffectcanbeobservedwhensunshineentersasmokyroom.Thesephoto-electricdetectorsarehighlysensitiveandreliable,solongasthesmokeparticlesarevisible.@#@Certainclassesoffire,however,emitinvisiblesmokeparticleslongbeforethefireisactuallyalightandinthesecasesanionizationsmokedetectormustbepresent.Althoughthedesignofthesedetectorsisslightlymorecomplicatedthaninthecaseofphoto-electricdetectors,thebasicprincipleisverysimple.Twometalplatesareseparatedbyseveralmillimetersandavoltageisappliedacrossthem.Sinceairdoesnotconductelectricity,nocurrentflows.Ifanionizingradioactivesourceisbroughtclosetotheplatesthentheairitselfisionized,thatis,electricallychargesparticlesarepresentbetweentheplatesandtheseallowatinycurrenttoflow.Anyparticlesenteringthechamber,eithervisibleorinvisible,tendtoneutralizetheions,thusdecreasingthecurrentflow.Itisthisreductionincurrentwhichismonitoredinmeasuringtheamountofsmokethatispresent.@#@Firedetectionanditscorrespondingsafetysystemsarecrucialpartsofanintelligentbuilding.Thispaperreviewsthecurrentstateofdevelopmentoffiredetectionandalarmsystemsintheintelligentbuilding.Newtechnologiesandconceptsdevelopedinintelligentbuildings,suchasadvancedmulti-functionsensors,computervisionsystemsandwirelesssensors,real-timecontrolviatheInternet,andintegratedbuildingservicesystems,havealsobeenreviewedanddiscussed.Thesenewtechnologiesandconceptswillimprovethecapabilityoffiredetectionsystemstodiscriminatebetweenfireandnon-firethreatsandwillincreasethetimeavailableforpropertyandlifeprotection.However,mucheffortisstillneededtoremovebarrierstothefurtherdevelopmentofthesenewtechnologies.@#@Newsensortechnologieswillbekeycomponentsinthenextgenerationofintelligentbuildings.Currentintelligentbuildingsoftenhaveembeddedprocessorsanddedicatedinformationnetworks.Thenewgenerationisexpectedtoaddthecapabilitytolearnaboutthebuildingscircumstancesanditsoccupantsneedsandchangethebehaviorofitscontrolsystemsaccordingly.Theemploymentofalargenumberofsensorswithinthebuildingwillallowittooperateinaresponsivemanner,ratherthanusingpre-programmedcontrolmodelsasareemployedinthefirsttwogenerationsofintelligentbuilding.Theinformationprovidedbysensorsincludeschangesinbothinternalandexternalenvironmentsofabuilding,suchassmoke,temperatureandhumidity,airquality,airmovement,andthenumberofbuildingoccupantsaswellasahostofotherproperties.Thesystemwillusesensorstoidentifyhowaparticularpersontendstoreacttoparticularcircumstancesandtolearndifferentbehaviorsfordifferentpeople.Thenumberofsensorsrequiredtoobtainthistypeoffunctionalityisquitehigh,especiallysinceoneofthemajorgoalsofintelligentbuildingsistoallowindividualizedcontrolofanenvironment.Thisneedwillincreasethecostofintelligentbuildingsandmakeitdifficulttomanagetheresultinglargeamountofdata.Developmentofcost-effectivesensorshasconsequentlybeenidentifiedasakeyneedforintelligentbuildings.Fortunately,manyofthepropertiesthatneedtobemonitoredcanbeusedformultiplepurposes.Securitysystemsthatcantracktheentryandexitofoccupantsfromanofficebuildingcanalsobeusedtoensurecompleteevacuationofabuildingduringafireoreven,inmoreadvancedforms,determinewhereoccupantsmaybetrappedandunabletoescape.Similarly,parameterssuchastemperat