简介:Thestiffenedcylindricalshelliscommonlyusedforthepressurehullofsubmersiblesandthelegsofoffshoreplatforms.Therearevariousfailuremodesbecauseofuncertaintywiththestructuralsizeandmaterialproperties,uncertaintyofthecalculationmodelandmachiningerrors.Correlationsamongfailuremodesmustbeconsideredwiththestructuralreliabilityofstiffenedcylindricalshells.However,thetraditionalmethodcannotconsiderthecorrelationseffectively.Theaimofthisstudyistopresentamethodofreliabilityanalysisforstiffenedcylindricalshellswhichconsidersthecorrelationsamongfailuremodes.Firstly,thejointfailureprobabilitycalculationformulaoftworelatedfailuremodesisderivedthroughuseofthe2Djointprobabilitydensityfunction.Secondly,thefullprobabilityformulaofthetandemstructuralsystemisgivenwithconsiderationtothecorrelationsamongfailuremodes.Atlast,theaccuracyofthesystemreliabilitycalculationisverifiedthroughuseoftheMonteCarlosimulation.Resultoftheanalysisshowsthefailureprobabilityofstiffenedcylindricalshellscanbegainedthroughaddingthefailureprobabilityofeachmode.
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简介:Inordertoachievetheinformationfusioninthetimedomainbasedontheevidencetheory,anevidencecombinationmethodinthetimedomainbasedonreliabilityandimportanceisproposedaccordingtotheideaofevidencediscount.Firstly,thedistortionofthetime-domainevidenceisjudgedbasedonsingleexponentialsmoothing.Thereal-timereliabilityoftheevidenceattheadjacenttimeisobtainedbythereal-timereliabilityassessmentmethodoftheevidencebasedonthecredibilitydecaymodel.Then,therelativeimportanceoftheevidenceattheadjacenttimeisobtainedbycomprehensivelyconsideringimprovedconflictdegreeanduncertainty.Finally,basedonthecriterionofevidencediscountandtheDempster’sruleofcombination,theevidencecombinationiscarriedouttoachievethesequentialcombinationoftime-domainevidence.Thenumericalsimulationandanalysisshowthatthismethodhasfullyembodiedthedynamiccharacteristicsoftime-domainevidencecombination,andithasstrongprocessingabilityforconflictinformationandanti-disturbingability.Theproposedmethodhasgoodapplicabilitytoinformationfusioninthetimedomain.
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简介:Wediscussatransferlineconsistingofareliablemachine,anunreliablemachineandastoragebuffer.Thistransferlinecanbedescribedbyagroupofpartialdifferentialequationswithintegralboundaryconditions.FirstweshowthattheoperatorcorrespondingtotheseequationsgeneratesapositivecontractionC0-semigroupT(t),andprovethatT(t)isaquasi-compactoperator.Nextweverifythat0isaneigenvalueofthisoperatoranditsadjointoperatorwithgeometricmultiplicityone.Last,byusingtheaboveresultsweobtainthatthetime-dependentsolutionoftheseequationsconvergesstronglytotheirsteady-statesolution.
简介:Background:TheGlobalPhysicalActivityQuestionnaire(GPAQ)hasbeenusedtomeasurephysicalactivity(PA)andsedentarytimeinFrance,butnostudyhasassesseditspsychometricproperties.ThisstudyaimedtocomparethereliabilityaswellascriterionandconcurrentvalidityoftheFrenchversionoftheGPAQwiththeFrenchInternationalPhysicalActivityQuestionnairelongform(IPAQ-LF)anduseofanaccelerometerinageneraladultpopulation.Methods:Weincluded92participants(studentsorstaff)fromtheMedicineCampusattheUniversityofLorraine,Nancy(north-easternFrance).TheFrenchGPAQwascompletedtwice,7daysapart,tostudytest-retestreliability.TheIPAQ-LFwasusedtoassessconcurrentvalidityoftheGPAQ,andparticipantsworeanaccelerometer(ActiGraphGT3X+)for7daystostudycriterionvalidity.ReliabilityaswellasconcurrentandcriterionvalidityoftheGPAQweretestedbytheintraclasscorrelationcoefficient(ICC),Spearmancorrelationcoefficientforquantitativevariables,andKappaandPhicoefficientsforqualitativevariables.BothconcurrentandcriterionvalidityofGPAQwereassessedbyBland-Altmanplots.Results:TheGPAQshowedpoortogoodreliability(ICC=0.37-0.94;Kappa=0.50-0.62)andconcurrentvalidity(Spearmanr=0.41-0.86),butonlypoorcriterionvalidity(Spearmanr=-0.22-0.42).LimitsofagreementfortheGPAQandaccelerometerwerewide,withdifferencesbetween286.5min/weekand601.3min/week.Conclusion:TheFrenchversionoftheGPAQprovideslimitedbutacceptablereliabilityandvalidityforthemeasurementofPAandsedentarytime.ItmaybeusedforassessingPAandsedentarytimeinaFrenchadultpopulation.
简介:Uptonow,outlierdetectionandreliabilitytheoryaregenerallybasedontheregularGauss-Markovmodels,inwhichthecovariancematrixofob-servationsispositivelydefinite.Fortheadjustmentmodelswithsingularcovari-ancematrix,thestatisticsforoutlierdetectionarederivedbytheauthors.Thecorrespondingreliabilitytheoryisdeveloped.Andtheapplicationofthetheoryisdemonstratedwithapracticalexample.
简介:TheCET4writingtestiswidelyusedinChina,butwhetheritisamorereliableandvalidtestofwritingforCET4thanothermethodsofevaluationisstillnotclear.Thepurposeofthisstudywastoexaminethereliabilityandthevalidityofamodificationofthistest.Incarryingoutthestudy,atotalof60Band4studentsinZhejiangUniversitytookthemodifiedtest,aCET4testandaFirstCertificatePracticeTest.TheresultsofthisstudydemonstratethatthemodifiedversionisasignificantlymorereliableandvalidwritingtestthanthepresentCET4writingtest.TheseresultssuggestthattheCET4writingtestneedsmodification.