毕业设计英文翻译.docx
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毕业设计英文翻译.docx
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毕业设计英文翻译
外文文献:
EstimatesoftheOperationalReliabilityofFireProtectionSystems
Forthepastthreeyears,theNationalInstituteofStandardsandTechnology(NIST)hasbeenworkingtodevelopanewencryptionstandardtokeepgovernmentinformationsecure.Theorganizationisinthefinalstagesofanopenprocessofselectingoneormorealgorithms,ordata-scramblingformulas,forthenewAdvancedEncryptionStandard(AES)andplanstomakeadecisionbylatesummerorearlyfall.Thestandardisslatedtogointoeffectnextyear.
INTRODUCTION
Background
Fireprotectionstrategiesaredesignedandinstalledtoperformspecificfunctions.Forexample,afiresprinklersystemisexpectedtocontrolorextinguishfires:
Toaccomplishthis,thesystem
sprinklersmustopen,andtherequiredamountofwatertoachievecontrolorextinguishmentmustbedeliveredtothefirelocation.Afiredetectionsystemisintendedtoprovidesufficient
earlywarningofafiretopermitoccupantnotificationandescape,andinsomecasesactivationofotherfireprotectionfeatures(e.g.,specialextinguishingsystems,smokemanagementsystems).Bothsystemactivation(detection)andnotification(alarm)mustoccurtoachieveearlywarning.Constructioncompartmentationisgenerallydesignedtolimittheextentoffirespreadaswellastomaintainthebuilding’sstructuralintegrityaswellastenabilityalongescaperoutesforsomespecifiedperiodoftime.Inordertoaccomplishthis,theconstructionfeaturesmustbefire“rated”(basedonstandardtests)andtheintegrityofthefeaturesmaintained.Thereliabilityofindividualfireprotectionstrategiessuchasdetection,automaticsuppression,andconstructioncompartmentationisimportantinputtodetailedengineeringanalysesassociatedwithperformancebaseddesign.
Inthecontextofsafetysystems,thereareseveralelementsofreliability,includingbothoperationalandperfornzancereliability.Operationalreliabilityprovidesameasureoftheprobabilitythatafireprotectionsystemwilloperateasintendedwhenneeded.Performancereliabilityisameasureoftheadequacyofthefeaturetosuccessfullyperformitsintendedhnctionunderspecificfireexposureconditions.Theformerisameasureofcomponentorsystemoperabilitywhilethelatterisameasureoftheadequacyofthesystemdesign.
Thescopeofthisstudywaslimitedtoevaluationofoperationalreliabilitydueprimarilytothe
formofthereporteddataintheliterature.Inadditiontothisdistinctionbetweenoperationaland
performancereliability,thescopefocusedonunconditionalestimatesofreliabilityandfailure
estimatesintermsoffail-dangerousoutcomes.Adiscussionofthesetermsisprovidedlaterinthepaper.
Scop
Thispaperprovidesareviewofreportedoperationalreliabilityandperformanceestimatesfor
(1)firedetection,
(2)automaticsuppression,andtoalimitedextent,(3)constructioncompartmentation.Ingeneral,thereportedestimatesforfiredetectionarelargelyforsmoke
detectiodfirealarmsystems;automaticsprinklerscomprisemostofthedataforautomaticsuppression,andcompartmentationincludescompartmentfireresistanceandenclosureintegrity.
Itshouldbenotedthatinsomecasestheliteraturedidnotdelineatebeyondthegeneral
categoriesof“firedetection”or“automaticsuppression,”requiringassumptionsregardingthe
specifictypeoffireprotectionsystem.
Severalstudiesreportedestimatesofreliabilityforbothfiredetectionandautomaticsprinkler
systemstrategies.However,verylittleinformationwasfounddetailingreliabilityestimatesfor
passivefireprotectionstrategiessuchascompartmentation.Alimitedstatisticalbasedanalysis
wasperformedtoprovidegeneralizedinformationontherangesofsuchestimatesandrelated
uncertainties.Thislattereffortwaslimitedtoevaluationofreporteddataondetectionand
suppression.Insufficientdatawereidentifiedoncompartmentationreliabilitytobeincluded.
Thispaperaddresseselementsofreliabilityastheyrelatetofiresafetysystems.Theliteraturesearchthatwasperformedforthisanalysisisreviewedandimportantfindingsanddatasummarized.Thedatafoundintheliteraturethatwereapplicabletosprinklerandsmokedetectionsystemsreliabilitywereanalyzed,withdescriptiveestimatesofthemeanvaluesand95
percentconfidenceintervalsfortheoperationalreliabilityoftheseinsitusystemsreported.
ELEMENTSOFRELIABILITYANALYSIS
ThereisconsiderabIevariationinreliabilitydataandassociatedanaIysesreportedintheliterature.Basically,reliabilityisanestimateoftheprobabilitythatasystemorcomponentwilloperateasdesignedoversometimeperiod.Duringtheusefulorexpectedlifeofacomponent,thistimeperiodis“reset”eachtimeacomponentistestedandfoundtobeinworkingorder.Therefore,themoreoftensystemsandcomponentsaretestedandmaintained,themorereliabletheyare.Thisformofreliabilityisreferredtoasunconditional.
Unconditionalreliabilityisanestimateoftheprobabilitythatasystemwilloperate“on
demand.”Aconditionalreliabilityisanestimatethattwoeventsofconcern,i.e.,afireand
successfuloperationofafiresafetysystemoccuratthesametime.Reliabilityestimatesthatdo
notconsiderafireeventprobabilityareunconditionalestimates.
Twootherimportantconceptsappliedtooperationalreliabilityarefuiled-safeandfailed-
dangerous.whenafiresafetysystemfailssafe,itoperateswhennofireeventhasoccurred.Acommonexampleisthefalsealarmingofasmokedetector.Afiresafetysystemfailsdangerouswhenitdoesnotfunctionduringafireevent.Inthisstudy,thefailed-dangerouseventdefinestheOperationalprobabilityoffailure(1-reliabilityestimate).Asprinklersystemnotoperatingduringafireeventoranoperatingsystemthatdoesnotcontrolorextinguishafireareexamplesofthistypeoffailure.
Theoverallreliabilityofasystemdependsonthereliabilityofindividualcomponentsandtheir
correspondingfailurerates,theinterdependenciesoftheindividualcomponentsthatcomposethe
system,andthemaintenanceandtestingofcomponentsandsystemsonceinstalledtoveri@
operability.Allofthesefactorsareofconcerninestimatingoperationazreliability.
Firesafetysystemperformanceisalsoofconcernwhendealingwiththeoverallconceptof
reliability.Systemperformanceisdefinedastheabilityofaparticularsystemtoaccomplishthe
taskforwhichitwasdesignedandinstalled.Forexample,theperformanceofafireratedseparationisbasedontheconstructioncomponent’sabilitytoremainintactandprovidefireseparationduringafire.Thedegreetowhichthesecomponentspreventfirespreadacrosstheir
intendedboundariesdefinessystemperformance.
Performancereliabilityestimatesrequiredataonhowwellsystemsaccomplishtheirdesigntaskunderactualfireeventsorfullscaletests.Informationonperformancereliabilitycouldnotbediscerneddirectlyfrommanyofthedatasourcesreviewedaspartofthiseffortduetotheform
ofthepresenteddata,andtherefore,itisnotaddressedasaseparateeffect.
Thecauseoffailureforanytypeofsystemistypicallyclassifiedintoseveralgeneralcategories:
installationerrors,designmistakes,manufacturing/equipmentdefects,lackofmaintenance,exceedingdesignlimits,andenvironmentalfactors.Thereareseveralapproachesthatcanbeutilizedtominimizetheprobabilityoffailure.Suchmethodsinclude
(1)designredundancy,
(2)activemonitoringforfaults,(3)providingthesimplestsystem(i.e.,theleastnumberofcomponents)toaddressthehazard,and(4)awelldesignedinspection,testing,andmaintenanceprogram.
Thesereliabilityengineeringconceptsareimportantwhenevaluatingreliabilityestimates
reportedintheliterature.Dependingonthedatausedinagivenanalysis,thereliabilityestimate
mayrelatetooneormoreoftheconceptspresentedabove.Theliteraturereviewconducted
underthescopeofthiseffortaddressestheseconceptswhereappropriate.MostoftheinformationthatwasobtainedfromtheliteratureinsupportofthispaperwerereportedintermsofunconditionaloperationaZreliability,i.e.,intermsoftheprobabilitythatafireprotectionstrategywillnotfaiZdangerous.
LITERATUREREVIEW
Aliteraturesearchwasconductedtogatherreliabilitydataofalltypesforfiresafetysystems
relevanttotheprotectionstrategiesconsidered:
automaticsuppression,automaticdetection,andcompartmentation.Theobjectiveoftheliteraturesearchwastoobtainsystem-specificreliabilityestimatesfortheperformanceofeachtypeoffiresafetysystemasafunctionofgeneric
occupancytype(e.g.,residential,commercial,andinstitutional).
Sourcesofinformationincludednationalfireincidentdatabasereports,USDepartmentofDefensesafetyrecords,industryandoccupancyspecificstudies,insuranceindustryhistoricalrecordsandinspectionreportsdocumentedintheopenliterature,andexperimentaldata.Reportsonexperimentalworkandfiretestingresultswereutilizedonlywhenfiredetection,automaticsuppression,orcompartmentationstrategieswereexplicitlyevaluated.Testsofsystemsusedforqualification,approval,orlistingwerealsoreviewedforinformationonfailuremodes.PublisheddatafromtheUnitedKingdom,Japan,Australia,andNewZealandwereincluded.
GeneralStudies
TheWarringtonFireResearchstudyaddressedthereliabilityoffiresafetysystemsandthe
interactionoftheircomponents.ADelphimethodologywasusedtodevelopdiscreteestimates
ofthereliabilityofdetectionandalarmsystems,fire
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