简介:BymeansofthefrozentimeapproachandtheKroneckerproduct,twocriteriaofasymptoticstabilityarederivedforthelinear,timevariantdynamicsystemswitheithershorttimedelaysorwithweakfeedbackinvolvingarbitrarytimedelays,respectively.Itisfoundthattheasymptoticstabilityoftheseretardeddy-nainicsystemsisgovernedbythemaximalandminimalsingularvaluesofthecoeffi-cientmatricesandtheirtimederivatives.
简介:Timereversalisappliedtotheunderwaterspreadingspectrumcodingcommunication.Onthebaseofanalyzingthefocusingcharacteristicsofthetimereversalinunderwaterwaveguide,thetimereversalisstudiedtoovercomethewavedistortionoftheencodedsignalcausedbythemulti-patheffect.TheexperimentresearchforunderwatercodingcommunicationiscarriedoutinalabwatertankandthecorrespondingtheoreticalanalysisisalsoconductedbyBinaryPhaseShiftKeying(BPSK)encodingandBarkercodewith7chipsforthespreadingspectrumsignal.Theresultsshowthatthetimereversalcanimprovethefocusinggainandincreasetheratiooftheprincipaltothesecondlobeofthecodingsignal,andcandecreasethebiterrorrateandincreasethecommunicationdistance.
简介:InthispaertheinequalityofLemma1of[1]isextended.BymeansofourinequalityandthemethodofLyapunovfunctionwestudythestabilityoftwokindsoflargeseatedifferentialsystemswithtimelagandthestabilityofahigher-orderdifferentialequationwithtimelag.Thesufficientconditionsforthestability(S.),theasymptoticstability(A.S.),theuniformlyasymptoticstability(U.A.S)andtheexponentialasymptoticstability(E.A.S.)ofthezerosolutionsofthesystermsareobtainedrespectively.
简介:Inthispaper,weproposeasusceptible-infected-susceptible(SIS)modeloncomplexnetworks,small-world(WS)networksandscale-free(SF)networks,tostudytheepidemicspreadingbehaviorwithtimedelaywhichisaddedintotheinfectedphase.Consideringtheuniformdelay,thebasicreproductionnumberR_0onWSnetworksandR_0onSFnetworksareobtainedrespectively.OnWSnetworks,ifR_0≤1,thereisadisease-freeequilibriumanditislocallyasymptoticallystable;ifR_0>1,thereisanepidemicequilibriumanditislocallyasymptoticallystable.OnSFnetworks,ifR_0≤1,thereisadisease-freeequilibrium;ifR_0>1,thereisanepidemicequilibrium.Finally,wecarryoutsimulationstoverifytheconclusionsandanalyzetheeffectofthetimedelayr,theeffectiverateλ,averageconnectivityandtheminimumconnectivitymontheepidemicspreading.
简介:Usingthetimereversal(TR)-reversetimemigration(RTM)mixedmethod,thenumericalanalysistowardstheacousticfieldfordetectionandlocationoftargetsinlayeredmediaisperformed.Firsttheapproachesandstepsofthenumericalanalysisandsimulationforacousticfieldareproposed,then,theacousticfielddistributionofsingletargetandmultipletargetsarefurthercomputedbyusingtheapproachesofsingleemission-multiplereceivingandmultipleemission-multiplereceiving.Thenumericalsimulationresultsindicatethattargetdetectionandlocationcanbewellrealized.Bycomparison,goodresultsareobtainedfromthebothtwoapproaches,butlargetime-consumingisobservedinwayofmultipleemission-multiplereceiving,andsowouldbeunacceptable.Additionally,theimprovedwayisalsoproposedformultipletargetdetection.
简介:Thispaperreviewssomeoftheprincipaluses,overalmostsevendecades,ofcorrelations,inbothEulerianandLagrangianframesofreference,ofpropertiesofturbulentflowsatvariablespatiallocationsandvariabletimeinstants.Commonlycalledspace–timecorrelations,theyhavebeenfundamentaltotheoriesandmodelsofturbulenceaswellasfortheanalysesofexperimentalanddirectnumericalsimulationturbulencedata.
简介:Fluvialprocessescomprisewaterflow,sedimenttransportandbedevolution,whichnormallyfeaturedistincttimescales.Thetimescalesofsedimenttransportandbeddeformationrelativetotheflowessentiallymeasurehowfastsedimenttransportadaptstocapacityregioninlinewithlocalflowscenarioandthebeddeformsincomparisonwiththeflow,whichliterallydictatesifacapacitybasedand/ordecoupledmodelisjustified.Thispapersynthesizestherecentlydevelopedmultiscaletheoryforsediment-l...
简介:Inthisnote,weobtainanasymptoticestimateforthetimederivativeoftheΦ-entropyintermsofthelowerboundoftheBakry–EmeryΓ2curvature.InthecasesofhyperbolicspaceandtheHeisenberggroup(moregenerally,thenilpotentLiegroupofranktwo),weshowthatthetimederivativeoftheΦ-entropyisnon-increasingandconcaveintimet,alsowegetasharpasymptoticboundforthetimederivativeoftheentropyinthesecases.
简介:Thesystemdynamicsofturningprocessescanbedescribedbyadelaydiferentialequation.Howtoimprovethestabilityandsuppressthevibrationofcuttingisofaninterestingtopic.Inthispaper,amultipletime-delaycontrollerisdevelopedbasedondiscreteoptimalcontrolmethodfortheturningvibrationscontrol.Numericalsimulationsarecarriedouttoverifytheefciencyofthecontroller.Resultsindicatethedesignedcontrollercansuppressthecuttingvibrationefcientlyandimprovethestabilityofthecuttingprocesses.Theinfluenceofdesignedtime-delayandsamplingtimeonthecontrolperformanceisalsodiscussed.