简介：

简介：自抗扰控制技术提出二十多年了，在国际国内有很多不同领域的工程应用，可是其理论基础却少有系统的研究。郭宝珠与赵志良的新书《ActiveDisturbanceRejectionControlforNonlinearSystems：AnIntroduction（非线性系统的自抗扰控制引论）》是作者们过去多年来关于非线性系统自抗扰控制理论基础的系统性总结，并配有大量的数值模拟。本书详细地引导读者领略自抗扰控制3个主要的部分：跟踪微分器、扩张状态观测器以及基于跟踪微分器和扩张状态观测器的反馈控制。

简介：Oxygen-containingdefectsareveryimportantforalteringthenonlinearoptical(NLO)propertiesofgraphene.Toinvestigatethecorrelationbetweenoxygen-containingdefectsandthesynergisticNLOresponseingraphenebasednanocomposites,weattachedCdSnanocrystalsonthesurfaceofgraphene(G)andpreparedG/CdSnanohybrids(NHs)consistingofvariousoxygen-containingfunctionalgroupsviaachemicalmethod.TheNLOabsorptionandrefractionofG/CdSNHsundersinglepulselaserirradiationareenhancedby10.8timeswiththeconcentrationdecreaseofsurfaceoxygen-containinggroups,whichmightbeattributedtothelocalfieldeffectsandsynergeticeffectsstemmingfromchargetransferbetweenthetwocomponents.However,theopticalnonlinearityisdecreasedwithfurtherconcentrationdecrease,whichmightarisefromsp~2fragmentinterconnectionandsurfacedefectsintheNHs.TheNLOabsorptiontransformationfromtwo-photonabsorptiontosaturableabsorptionwithoxygendecreaseisobserved,andintensity-relatedNLOabsorptionandrefractioninNHsarealsodiscussed.Meanwhile,theG/CdSNHsexhibitsuperiorNLOproperties,implyingpotentialapplicationsofNHmaterialinNLOdevices.

简介：Thispaperdealswiththemixedinitial-boundaryvalueproblemofDirichlettypeforthenonlinearelastodynamicsystemoutsideastar-shapeddomain.Thealmostglobalexistenceofsolutionwithsmallinitialdatatothisproblemisprovedandalowerboundforthelifespanofsolutionsisgiven.

简介：Weexperimentallydemonstrateforthefirsttime,tothebestofourknowledge,anall-fiberpassivelymode-lockedlaseroperationbasedonthenonlinearmultimodeinterferenceofstep-indexmultimodefiber.Suchastructurecouplesthelightinandoutofthemultimodefiberviasingle-modefibers,anditsphysicalmechanismsforsaturableabsorptionhavebeenanalyzedtheoreticallybasedonthethird-ordernonlinearKerreffectofmultimodefiber.Usingthenonlinearmultimodeinterferencestructurewith48.8mmlengthstep-indexmultimodefiber,themodulationdepthhasbeenmeasuredtobe~5%.Thepassivelymode-lockedlaseroutputpulseshaveacentralwavelengthof1596.66nm,bandwidthof2.18nm,pulsewidthof~625fs,andfundamentalrepetitionrateof8.726MHz.Furthermore,theinfluenceoftotalcavitydispersionontheopticalspectrum,pulsewidth,andoutputpowerisinvestigatedsystematicallybyaddingdifferentlengthsofsingle-modefiberanddispersioncompensationfiberinthelasercavity.

简介：Two-dimensional（2D）materialshaveemergedasattractivemediumsforfabricatingversatileoptoelectronicdevices.Recently,few-layermolybdenumdisulfide（MoS2）,asashining2Dmaterial,hasbeendiscoveredtopossessboththesaturableabsorptioneffectandlargenonlinearrefractiveindex.Herein,takingadvantageoftheuniquenonlinearopticalpropertiesofMoS2,wefabricatedahighlynonlinearsaturableabsorptionphotonicdevicebydepositingthefew-layerMoS2ontothemicrofiber.WiththeproposedMoS2photonicdevice,apartfromtheconventionalsolitonpatterns,themode-lockedpulsescouldbeshapedintosomenewsolitonpatterns,namely,multiplesolitonmolecules,localizedchaoticmultipulses,anddouble-scalesolitonclusters.Ourfindingsindicatethatthefew-layerMoS2-depositedmicrofibercouldoperateasapromisinghighlynonlinearphotonicdevicefortherelatednonlinearopticsapplications.

简介：Wedemonstrateapassivelymode-lockedall-fiberlaserincorporatingapieceofgraded-indexmultimodefiberasamode-lockingmodulatorbasedonanonlinearmultimodalinterferencetechnique,whichgeneratestwotypesofcoexistinghigh-energyultrashortpulses(i.e.,theconventionalsoliton(CS)andthestretchedpulse(SP))TheCSwithpulseenergyashighas0.38nJisobtainedatthepumplevelof130mW.Whenthepumpincreasesto175mW,thehigh-energySPoccursatasuitablenonlinearphasebiasanditspulseenergycanreach4nJata610mWpump.ThepulsedurationsofthegeneratedCSandSPare2.3psand387fs,respectively.Thetheoryofnonlinearfiberoptics,single-shotspectralmeasurementbythedispersiveFourier-transformtechnique,andsimulationmethodsbasedontheGinzburg–LandauequationareprovidedtocharacterizethelaserphysicsandrevealtheunderlyingprinciplesofthegeneratedCSandSP.Aroguewave,observedbetweentheCSandSPregions,mirrorsthelaserphysicsbehindthedynamicsofgeneratingahigh-energySPfromaCS.Theproposedall-fiberlaserisversatile,cost-effectiveandeasytointegrate,whichprovidesapromisingsolutionforhigh-energypulsegeneration.

简介：MakinguseoftheZ2×Z2symmetry,wecouldstudythestructurenearmultipleS-treakingturningpoints.Inparticular,weshowthatthereexisttwokindsofsingularpointpaththroughdoubleSbreakingturningpointsandtripleSbieakingturningpoints,onetsquadraticturningporntpathandoneisquadraticpitchforkbifurcationpointpath.SomesimpleregularextendedsystemstocornputedoubleandtripleS-breakingturningpointsareproposed.Numericalexamplesarealsogreen

简介：Fortwo-dimensionnonlinearconvectiondiffusionequation,atwo-gridmethodofcharacteristicsfinite-elementsolutionwasconstructed.Inthismethodthenonlineariterationsisonlytoexecuteonthecoarsegridandthefine-gridsolutioncanbeobtainedinasinglelinearstep.Forthenonlinearconvection-dominateddiffusionequation,thismethodcannotonlystabilizethenumericaloscillationbutalsoacceleratetheconvergenceandimprovethecomputationalefficiency.Theerroranalysisdemonstratesifthemeshsizesbetweencoarse-gridandfine-gridsatisfythecertainrelationship,thetwo-gridsolutionandthecharacteristicsfinite-elementsolutionhavethesameorderofaccuracy.Thenumericalexampleconfirmsthatthetwo-gridmethodismoreefficientthanthatofcharacteristicsfinite-elementmethod.

简介：Aself-adaptiveprecisealgorithminthetimedomainwasemployedtosolve2-Dnonlinearcoupledheatandmoisturetransferproblems.Byexpandingvariablesatadiscretizedtimeinterval,thevariationsofvariablescanbedescribedmoreprecisely,andanonlinearcoupledinitialandboundaryvalueproblemwasconvertedintoaseriesofrecurrentlinearboundaryvalueproblemswhicharesolvedbyFEtechnique.Inthecomputation,noadditionalassumptionandthenonlineariterationarerequired,andacriterionforself-adaptivecomputationisproposedtomaintainsufficientcomputingaccuracyforthechangesizesoftimesteps.Inthenumericalcomparison,thevariationsofmaterialpropertieswithtemperature,moisturecontent,andbothtemperatureandmoisturecontentaretakenintoaccount,respectively.Satisfactoryresultshavebeenobtained,indicatingthattheproposedapproachiscapableofdealingwithcomplexnonlinearproblems.

简介：Inthepaper,thenonlinearmagnetoelasticpropertiesofcompositionTb0.27Dy0.73Fe1.95<110>orientedpolycrystallinealloysareinvestigatedundercoupledloadsofhighmagneticfieldandcompressivestress.Themagnetizationandmagnetostrictionaremeasuredsimultaneouslyunderappliedmagneticfieldfrom800to800kA/mandcompressivestressfrom0to25MPaatroomtemperature.Thestraincoefcientandrelativepermeabilityareobtainedbydiferentialcalculationfromtheexperimentalcurves.Theresultsshowthatthevaluesofsaturationmagnetization(Ms)underdiferentcompressivestressesremaininvariablyconstantintheregionofthehighmagneticfield.Thesaturationmagnetostriction(λs)increaseswithincreasingcompressivestressandreaches1680×106under25MPa.Accordingtotheincreaseofthecompressivestress,thehystereticloopareaofmagnetizationandmagnetostrictionincreases,whilethemaximumrelativepermeabilityandstraincoefcientdecrease.Additionally,theinfluenceofthebiasmagneticfieldonthemechanicalpropertyistakenintoaccount.Thestress-strainrelationshipisnonlinearandsensitivetotheappliedexternalmagneticfieldsalongtheaxisofrod.Theresultsobtainedareausefulcomplementtotheexistingexperimentsfortheoreticalapproachesandengineeringapplications.

简介：

简介：Inthispaper,bothnonlinearsaturableabsorptionandtwo-photonabsorption（TPA）offew-layermolybdenumdiselenide（MoSe2）wereobservedat1.56μmwavelengthandfurtherappliedtomode-lockedultrafastfiberlaserforthefirsttimetoourknowledge.Few-layerMoSe2nanosheetswerepreparedbyliquid-phaseexfoliationmethodandcharacterizedbyxraydiffractometer,Ramanspectroscopy,andatomicforcemicroscopy.TheobtainedfewlayerMoSe2dispersionisfurthercompositedwithapolymermaterialforconvenientfabricationofMoSe2thinfilms.Then,weinvestigatedthenonlinearoptical（NLO）absorptionpropertyofthefew-layerMoSe2filmusingabalancedtwin-detectormeasurementtechnique.BoththesaturableabsorptionandTPAeffectsofthefew-layerMoSe2filmwerefoundbyincreasingtheinputopticalintensity.Thesaturableabsorptionshowsamodulationdepthof0.63%andalownonsaturablelossof3.5%,correspondingtotherelativemodulationdepthof18%.TheTPAeffectoccurredwhentheinputopticalintensityexceeds260MW∕cm2.Furthermore,weexperimentallyexploitthesaturableabsorptionoffew-layerMoSe2filmtomodelockanall-fibererbium-dopedfiberlaser.Stablesolitonmodelockingat1558nmcenterwavelengthisachievedwithpulsedurationof1.45ps.ItwasalsoobservedthattheTPAprocesssuppressesthemode-lockingoperationinthecaseofhigheropticalintensity.OurresultsindicatethatlayeredMoSe2,asanothertwo-dimensionalnanomaterial,canprovideexcellentNLOproperties（e.g.,saturableabsorptionandTPA）forpotentialapplicationsinultrashortpulsegenerationandopticallimiting.

简介：

简介：Amode-lockedthulium-dopedfiberlaser(TDFL)basedonnonlinearpolarizationrotation(NPR)withdifferentnetanomalousdispersionisdemonstrated.Whenthecavitydispersionis-1.425ps~2,thenoise-like(NL)pulsewithcoherencespikewidthof406fsandpulseenergyof12.342nJisgeneratedatacenterwavelengthof2003.2nmwith3dBspectralbandwidthof23.20nm.Intheexperimentalperiodof400min,the3dBspectralbandwidthvariation,theoutputpowerfluctuation,andthecentralwavelengthshiftarelessthan0.06nm,0.04dB,and0.4nm,respectively,indicatingthattheNPR-basedTDFLoperatingintheNLregimeholdsgoodlong-termstability.

简介：Liquid-phase-exfoliationtechnologywasutilizedtopreparelayeredMoS2,WS2,andMoSe2nanosheetsincyclohexylpyrrolidone.Thenonlinearopticalresponseofthesenanosheetsindispersionswasinvestigatedbyobservingspatialself-phasemodulation（SSPM）usinga488nmcontinuouswavelaserbeam.ThediffractionringpatternsofSSPMwerefoundtobedistortedalongtheverticaldirectionrightafterthelasertraversingthenanosheetdispersions.Thenonlinearrefractiveindexofthethreetransitionmetaldichalcogenidesdispersionsn2wasmeasuredtobe10-7cm2W-1,andthethird-ordernonlinearsusceptibilityχ（3）10-9esu.TherelativechangeofeffectivenonlinearrefractiveindexΔn2e∕n（2e）oftheMoS2,WS2,andMoSe2dispersionscanbemodulated0.012–0.240,0.029–0.154,and0.091–0.304,respectively,bychangingtheincidentintensities.Ourexperimentalresultsimplynovelpotentialapplicationoftwo-dimensionaltransitionmetaldichalcogenidesinnonlinearphasemodulationdevices.

简介：Bytheadditionalreactionofbinuclearcompounds(Me4N)2M2S4(TDT)2(M=Mo,W;H2TDT=H2CH3C6H3S2)withmononuclearcuprouscomplex,twonewM-Cu-SclustersMo2Cu2S4(TDT)2-(PPh3)2·CH3CH2OH(1)andW2Cu2S4(TDT)2(PPh3)2·0.5CH3CH2OH-0.5H2O(2)havebeenpreparedandcharacterizedbyIR,UV-Vis,31PNMRspectroscopy,cyclicvoltammetryandsinglecrystalX-raystructureanalysis.BothcompoundscrystallizeinspacegroupP21/nwithlatticeparametersa=1.0956(3),b=2.2072(3),c=2.4340(3)nm,β=100.36(2)°,V=5.790(3)nm3andZ=4for1anda=1.0965(9),b=2.2135(3),c=2.4317(4)nm,β=99.63(8)°,V=5.819(8)nm3andZ=4for2.Bothmolecularstructurescontainacubane-likeclustercore[M2Cu2S4](M=Mo,W)andtheirskeletonsarealmostthesameexceptforMatoms.Thesyntheses,structuresandspectrumcharacterizationsofthesetwoclustersarediscussed.Thethird-ordernonlinearoptical(NLO)propertyofthetwoclusterswasstudiedbythetechniqueofforwarddegeneratefour

简介：在现在的纸，我们声明有关为非卷绕旋转的一个类的pointwise集中和它的率的一些近似定理打形式的非线性的不可分的操作员：

简介：Inthispaper,weinvestigatethetravelingwavesolutionsforthenonlineardispersiveequation,Korteweg-deVriesZakharov–Kuznetsov(KdV-ZK)equationandcomplexcoupledKdVsystembyusingextendedsimplestequationmethod,andthenderivethehyperbolicfunctionsolutionsincludesolitonsolutions,trigonometricfunctionsolutionsincludeperiodicsolutionswithspecialvaluesfordoubleparametersandrationalsolutions.Thepropertiesofsuchsolutionsareshownbyfigures.Theresultsshowthatthismethodisaneffectiveandapowerfultoolforhandlingthesolutionsofnonlinearpartialdifferentialequations(NLEEs)inmathematicalphysics.

简介：在旅行波浪转变下面，一些非线性的部分微分方程例如Camassa河边肥沃的低地方程，高顺序的KdV方程，等等，被归结为u″表示的一首integrable颂诗+p(u)(u')2+q(u)=0答案能被给其将军。而且，为多项式联合完全的辨别系统，这些方程的所有单个旅行波浪答案的分类被获得。方程u″0包括的+p(u)(u')2+q(u)=是的方程(u')2=f(u)一种特殊情况，建议方法能也因此被用于很多非线性的方程。这些完全的结果不能被任何间接方法获得。