毕业设计英文翻译.docx

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