简介：Asimpleone-potnon-isocyanaterouteforsynthesizingthermoplasticpolyureasispresented.Insituurethanizationwasconductedfromthering-openingreactionofethylenecarbonatewithpoly(propyleneglycol)bis(2-aminopropylether)andhexanediamine,m-xylylenediamine,ordiethyleneglycolbis(3-aminopropyl)etherat100℃for6hundernormalpressure.Melttransurethanepolycondensationwassuccessivelyconductedat170℃underareducedpressureof399Pafordifferenttimeperiods.Aseriesofnonisocyanatethermoplasticpolyureas(NI-TPUreas)wereprepared.TheNI-TPUreaswerecharacterizedbygelpermeationchromatography,FTIR,1H-NMR,differentialscanningcalorimetry,thermogravimetricanalysis,wide-angleX-raydiffraction,atomicforcemicroscopy,andtensiletest.NI-TPUreasexhibitedMnofupto1.67×10^4g/mol,initialdecompositiontemperatureover290℃,andtensilestrengthofupto32MPa.SeveralcrystallizableNI-TPUreasexhibitedTmexceeding98℃.NI-TPUreaswithgoodthermalandmechanicalpropertieswerepreparedthroughagreenandsimpleone-potnon-isocyanateroute.

简介：Thispaperpresentsananalyticalsolutiontotheunsteadyflowofthesecond-ordernon-Newtonianfluidsbytheuseofintergraltransformationmethod.Basedonthenumericalresults,theeffectofnon-NewtoniancoefficientHcandotherparametersontheflowareanalysed.Itisshownthattheannularflowhasashortercharacteristictimethanthegeneralpipeflowwhilethecorrespondentvelocity,averagevelocityhavea(?)allervalueforagivenHc.Else,whenradiiratiokeepsunchanged,theshearstressofinnerwallofannularflowwillchangewiththeinnerradiuscomparedwiththegeneralpipeflowandisalwayssmallerthanthatoftheouterwall.

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简介：采用变物性格子Boltzmann通量求解器（VPLBFS)研究了Rayleigh-Benard热对流.以超临界流体为例，采用VPLBFS的简化形式和标准形式分别得到了通常关注的基于Boussinesq假设的常物性解，只考虑部分物性变化的基于partialBoussinesq假设的PBA解，以及考虑流体全部物性变化的变物性解，分析了non-Boussinesq效应对Rayleigh-B6nard热对流的影响，讨论了不同温差条件下的non-Boussinesq效应.研究结果表明：non-Boussinesq效应对超临界流体的Rayleigh-B6nard热对流有非常显著的抑制作用，论证了在研究热对流时考虑流体全部物性变化的必要性.

简介：Insituphotochromicprocessinthemonolayerofaphotochromicspiropyranderivativewithoutlongalkylchain,wasinvestigated.Thephotochromismattheair/waterinterfaceunderdiffernetsurfacepressureswasstudiedbysurfacepressure-areaisotherms,surfacepressure-timecurves,area-timecurvesandBrewsteranglemicroscopy.Bothformsofthecompoundwerefoundtoformmonolayersattheair/waterinterfacealthouhgitdoesnothavelongalkylchain.Alargeareaexpansioninthemonolayercorrespondingtoazreo^thorderreactionwasfoundattheinitialstageoftheUVlightirradiation.Aseriesofdynamicinvestigationsrevealedthatathighpressureafterphasetransitioninthemonolayer,thesurfacepressurechangesgreatlyumderalternativeirradiationofUVandvisiblelight.Anobviousmorphologicalchangeaccompanyingwiththephotochromismwasobservedinsitu.

简介：Inthispaper,anewdomaindecompositionmethodbasedonthenaturalboundaryreduction,whichsolveswaveproblemsoveranunboundeddomain,issuggestted.Ancircularartifcialboundaryisintroduced.Theoriginalunboundeddomainisdividedintotwosubdomains,aninternalboundedregionandexternalunboundedregionoutsidetheartificialboundary.ADirichlet-Neumann(D-N)alternatingiterationalgorithmisconstructed.WeprovethatthealgorithmisequavilenttopreconditionalRichardsoniterationmethod.Numericalstudiesareperformedbyfiniteelementmethod.ThenumericalresultsshowthattheconvergencerateofthediscreteD-Niterationisindependentofthefniteelementmeshsize.

简介：Basedontheporousmediatheoryandbytakingintoaccounttheeffectsoftheporefluidviscidity,energyexchangesduetotheadditionalthermalconductionandconvectionbetweensolidandfluidphases,amathematicalmodelforthedynamic-thermo-hydro-mechanicalcouplingofanon-localthermalequilibriumfluid-saturatedporousmedium,inwhichthetwoconstituentsareassumedtobeincompressibleandimmiscible,isestablishedundertheassumptionofsmalldeformationofthesolidphase,smallvelocityofthefluidphaseandsmalltemperaturechangesofthetwoconstituents.Themathematicalmodelofalocalthermalequilibriumfluid-saturatedporousmediumcanbeobtaineddirectlyfromtheaboveone.SeveralGurtin-typevariationalprinciples,especiallyHu-Washizutypevariationalprinciples,fortheinitialboundaryvalueproblemsofdynamicandquasi-staticresponsesarepresented.Itshouldbepointedoutthatthesevariationalprinciplescanbedegeneratedeasilyintothecaseofisothermalincompressiblefluid-saturatedelasticporousmedia,whichhavebeendiscussedpreviously.

简介：Anovelstructureisproposedfordoublingtheverticalbreakdownvoltageofsilicon-on-insulator(SOI)devices.Inthisnewstructure,theconventionalburiedoxide(BOX)inanSOIdeviceissplitintotwosections:thesource-sectionBOXandthedrain-sectionBOX.Ahighly-dopedSilayer,referredtoasanon-depletionpotential-clampedlayer(NPCL),ispositionedunderandclosetothetwoBOXsections.InthesplitBOXesandtheSiregionabovetheBOXes,theblockingvoltage(BV)isdividedintotwopartsbytheNPCL.ThevoltageintheNPCLisclampedtobenearlyhalfofthedrainvoltage.Whenthedrainvoltageapproachesabreakdownvalue,thevoltagesustainedbythesource-sectionBOXandtheSiregionunderthesourcearenearlythesameasthevoltagesustainedbythedrain-sectionBOXandtheSiregionunderthedrain.TheverticalBVisthereforealmostdoubled.TheeffectivenessofthisnewstructurewasverifiedforaP-channelSOIlateraldouble-diffusedmetal-oxidesemiconductor(LDMOS)andcanbeappliedtootherhigh-voltageSOIdevices.ThesimulationresultsshowthattheBVinanNPCLP-channelSOILDMOSisimprovedby55%andthespecificon-resistance(Ron,sp)isreducedby69%incomparisontotheconventionalstructure.

简介：Thepyrolyzedcarbonsupportedferrumpolypyrrole(Fe-N/C)catalystsaresynthesizedwithorwithoutselecteddopants,p-toluenesulfonicacid(TsOH),byafacilethermalannealingapproachatdesiredtemperatureforoptimizingtheiractivityfortheoxygenreductionreaction(ORR)inO2-saturated0.1mol/LKOHsolution.Theelectrochemicaltechniquessuchascyclicvoltammetry(CV)androtatingdiskelectrode(RDE)areemployedwiththeKoutecky-LevichtheorytoquantitativelyobtaintheORRkineticconstantsandthereactionmechanisms.ItisfoundthatcatalystsdopedwithTsOHshowsignificantlyimprovedORRactivityrelativetotheTsOH-freeone.TheaverageelectrontransfernumbersforthecatalyzedORRaredeterminedtobe3.899and3.098,respectively,forthecatalystswithandwithoutTsOH-doping.Theheat-treatmentisfoundtobeanecessarystepforcatalystactivityimprovement,andthecatalystpyrolyzedat600℃givesthebestORRactivity.Anonsetpotentialandthepotentialatthecurrentdensityof-1.5mA/cm2forTsOH-dopedcatalystafterpyrolysisare30mVand170mV,whicharemorepositivethanthosewithoutpyrolized.Furthermore,thecatalystdopedwithTsOHshowshighertolerancetomethanolcomparedwithcommercialPt/Ccatalystin0.1mol/LKOH.TounderstandthisTsOHdopingandpyrolyzedeffect,X-raydiffraction(XRD),scanningelectronmicroscope(SEM)andX-rayphotoelectronspectroscopy(XPS)areusedtocharacterizethesecatalystsintermsoftheirstructureandcomposition.XPSresultsindicatethatthepyrrolic-Ngroupsarethemostactivesites,afindingthatissupportedbythecorrespondencebetweenchangesinpyridinic-NcontentandORRactivitythatoccurwithchangingtemperature.SulfurspeciesarealsostructurallyboundtocarbonintheformsofC–Sn–C,anadditionalbeneficialfactorfortheORR.

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简介：Thispaperstudiesconformalinvarianceandconservedquantityofthird-orderLagrangeequationsfornonconservedmechanicalsystems.Third-orderLagrangeequations,thedefinitionandadeterminingequationofconformalinvarianceofthesystemarepresented.TheconformalfactorexpressionisdeducedfromconformalinvarianceandLiesymmetry.ThenecessaryandsufficientconditionthatconformalinvarianceofthesystemwouldhaveLiesymmetryundersingle-parameterinfinitesimaltransformationsisobtained.Thecorrespondingconservedquantityofconformalinvarianceisderivedwiththeaidofastructureequation.Lastly,anexampleisgiventoillustratetheapplicationoftheresults.

简介：在这篇论文，我们学习一般的伪的Cauchy问题的全球古典解决方案的asymptotic行为有多重的常数并且弱的线性夸张系统线性地堕落典型领域。基于周毅等证明的全球古典答案的存在，我们证明当t趋于到无穷时，答案接近C~1旅行波浪答案的联合，如果全部的变化和起始的数据的L~1标准是足够地小的。

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简介：基于无穷小并且一参数转变，三顺序的Lagrangian方程的谎言对称的问题被学习了。在谎言转变下面，使Lagrangian方程三顺序未改变的足够、必要的条件并且不变在这篇论文被获得。

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简介：Acompositebeamissymmetricifboththematerialpropertyandsupportaresymmetricwithrespecttothemiddlepoint.Inordertostudythefreevibrationperformanceofthesymmetriccompositebeamswithdifferentcomplexnonsmooth/discontinuousinterfaces,wedevelopanR(x)-orthonormaltheory,whereR(x)isanintegrableflexuralrigidityfunction.TheR(x)-orthonormalbasesinthelinearspaceofboundaryfunctionsareconstructed,ofwhichthesecond-orderderivativesoftheboundaryfunctionsareaskedtobeorthonormalwithrespecttotheweightfunctionR(x).WhenthevibrationmodesofthesymmetriccompositebeamareexpressedintermsoftheR(x)-orthonormalbaseswecanderiveaneigenvalueproblemendowedwithaspecialstructureofthecoefficientmatrixA:=[aij],aij=0ifi+jisodd.Basedonthespecialstructurewecanprovetwonewtheorems,whichindicatethatthecharacteristicequationofAcanbedecomposedintotheproductofthecharacteristicequationsoftwosub-matriceswithdimensionshalflower.Hence,wecansequentiallysolvethenaturalfrequenciesinclosed-formowingtothespecialtyofA.Weusethispowerfulnewtheorytoanalyzethefreevibrationperformanceandthevibrationmodesofsymmetriccompositebeamswiththreedifferentinterfaces.

简介：Anon-autonomouscompetingsystemisinvestigatedinthispaper,wherethespeciesxcandiffusebetweentwopatchesofaheterogeneousenvironmentwithbarriersbetweenpatches,butforspeciesy,thediffusiondoesnotinvolveabarrierbetweenpatches,furtheritisassumedthatalltheparametersaretimedependent.Itisshownthatthesystemcanbemadepersistentundersomeappropriateconditions.Moreover,sufficientconditionsthatguaranteetheexistenceofauniquepositiveperiodicorbitwhichisgloballyasymptoticstablearederived.

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