简介:BasedupontheHellinger-Reissner(H-R)mixedvariationalprincipleforthree-dimensionalelasticbodies,themodifiedH-Rmixedvariationaltheoremformagnetoelectroelasticbodieswasestablished.Thestate-vectorequationofmagnetoelectroelasticplateswasderivedfromtheproposedtheorembyperformingthevariationaloperations.Tolayatheoreticalbasisofthesemi-analyticalsolutionappliedwiththemagnetoelectroelasticplates,thestate-vectorequationforthediscreteelementinplanewasproposedthroughtheuseoftheproposedprinciple.Finally,itispointedoutthatthemodifiedH-Rmixedvariationalprincipleforpureelastic,singlepiezoelectricorsinglepiezomagneticbodiesarethespecialcasesofthepresentvariationaltheorem.
简介:Poly(azureblueⅡ)(PABⅡ)thinfilmmodifiedelectrodewassuccessfullyassembledonthesurfaceofaglassycarbonelec-tradebymeansofelectrochemicalpolymerization,whichwascarriedoutwithcyclicvoltammetricsweepinginthepotentialrangeof-0.6to+1.3V(vs.SCE)inBritton-Robinsonbuffersolution(pH=9.8)containing1.25x10^-4mol/LazureblueⅡ.TheeffectofpHonthepolymerizationprocessofazureblueⅡandthedeetrochemicalcharacteristicsofthepolymer-modifiedelectrodeswerestudiedindetail.Theexperimentalre-suitsindicatedthattheelectropolymerizatiouofazureblueⅡcouldtakeplaceinbasicorneutralmedia.Thecyclicvoltam-mogramsofpoly(azureblueⅡ)thinfilmmodifiedelectrodeshowedthepresenceoftwocouplesofredoxpeaks.Thefilmmodifiedelectrodeexhibitedpotentandpersistentelectrocataly-sisforoxidationofdihydronicotiamideadeninedinucleotide(NADH)inphosphatebuffermediawithadiminutionoftheoverpotentialofabout410mVandanincreaseinpeakcurrent.ThepresenceofsomedivalentcationsinanelectrolytecangreatlyenhancetheeleetrocotolyficcurrentforoxidationofNADH.TheeleetrocatalyticcurrentincreasedlinearlywithNADHconcentrationfrom1.0×10^-5to8.0×10^-3mol/Linthepresenceof4.0×10^-2mol/LMg^2+cation.Thedetectionlimit(3Sb1/S)WaS5.0×10^-6mol/L,andtherelativestandarddeviationofdeterminationresultswas4.2%forsixsuccessivedeterminationsof5.0×10^-4mol/LNADHinthepresenceofMg^2+cation.
简介:Twofamiliesofcatalysts,basedonPdnanoparticlessupportedonceramicasymmetrictubularaluminamembranes,arestudiesinthedirectsynthesisofH_2O_2.TheyarepreparedbydepositingPdintwoways:(i)reductionwithN_2H_4inanultrasonicbathand(ii)byimpregnation-deposition.Thefirstpreparationleadstolargerparticles,withaveragesizeofaround11nm,whilethesecondpreparationleadstosmallerparticles,withaveragesizearound4nm.Thecatalyticmembranesweretestedasprepared,afterthermaltreatmentinairandafterfurtherpre-reductionwithH_2inmild(100℃)conditions.SampleswerecharacterizedbyTEM,CO-chemisorptionmonitoredbyDRIFTSmethodandTPR,whilecatalytictestshavebeenperformedinasemi-batchrecirculationmembranereactor.Experimentalcatalyticresultswereanalysedusingtwokineticsmodelstoderivethereactionconstantsfortheparallelandconsecutivereactionsofthekineticnetwork.SmallerparticlesofPdshowlowerselectivityduetothehigherrateofparallelcombustion,evenifthebetterdispersionofPdandthushighermetalsurfaceareainthesampleleadtoaproductivityinH_2O_2similarorevenhigherthanthesamplewiththelargerPdparticles.IndependentlyonthepresenceofsmallerorlargerPdnanoparticles,anoxidationtreatmentleadstoasignificantenhancementintheproductivity,althoughthecatalystprogressivelyreducesduringthecatalyticprocess.Theinhibitionoftheparallelcombustionreaction(towater)inducedfromthecalcinationtreatmentremainsafterthein-situreductionoftheoxidizedPdspeciesformedduringthepre-treatment.Thisislikelyduetotheeliminationofdefectsiteswhichdissociativelyactivateoxygen,andtentativelyattributedtoPdsitesabletogivethree-andfour-foldcoordinationofCO.
简介:ThispaperinvestigatestherobuststochasticstabilityandH∞analysisforstochasticsystemswithtime-varyingdelayandMarkovianjump.Byusingthefreeweightingmatrixtechnique,i.e.,He’stechnique,andastochasticLyapunov-Krasovskiifunctional,newdelay-dependentcriteriaintermsoflinearmatrixinequalitiesarederivedforthetherobuststochasticstabilityandtheH∞disturbanceattenuation.Threenumericalexamplesaregiven.Theresultsshowthattheproposedmethodisefficientandmuchlessconservativethantheexistingresultsintheliterature.更多还原
简介:Ionothermalsynthesiswasusedtoprepareanovelaminoacidcontaininghybridzincophosphatemonomer,[Zn(HPO4)(H2PO4)][C6H10N3O2](denotedasZnPO-CJ58).Theinorganicframeworkof[Zn(HPO4)(H2PO4)]·[C6H10N3O2]consistsof4-memberedringsformedbyZnO3OHisandPO2(OH)2tetrahedra.TheHPO4andaminoacidmoietieshangontheZncenter.Suchaframeworkisstabilizedbyextensivemultipointhydrogenbondsinvolvingthephosphateunitsandhistidinemoleculestoformapseudo-3Dsupramolecularstructure.ItisnoteworthythatZnPO-CJ58isthefirstzincphosphateclusterwithaminoacidactingastheligand.Itexhibitsphotoluminescenceexcitedatawavelengthof220nm.Interestingly,ZnPO-CJ58cantransformintoalayeredstructure(C6H10N3O2)Zn2·(HPO4)(PO4)·H2O(ZnPO-CJ36)throughfurtherreactingwithwaterorzincacetatedihydrateinwaterat85℃for1h.Thisworkwillbehelpfulforthesynthesisofcrystallineinorganic-organichybridmaterialswithbiofunctionalmolecules.
简介:利用水热法首次合成了具有两种配位环境Cd原子的新型杂多蓝化合物[NH3(CH2)2NH3]5[Cd(H2O)][CdMo12^vO30(HPO4)6(H2PO4)2]·5H2O.通过元素分析、ICP、TG和X射线单晶衍射确定了其组成,使用IR和EPR进行了结构表征.通过N2吸附脱附测定了比表面积和孔径,为催化研究提供了基础数据.结果表明:该晶体为三斜晶系,P-1,空间群;晶胞参数a=1.2002(2)nm,b=1.4651(3)nm,c=2.1192(4)nm,V=3.5642(12)nm^3,p=83.01(3)°,Z=2,F(000)=2932,R1=0.0300,wR2=0.0716.
简介:The2-Dheteronuclearcoordinationpolymer{[Ag4Fe2(SCN)12(H2O)2][(inaH)2(H2O)2]}n(1)(inaHistheabbreviationofprotonatedisonicotinicacid)withchemicalformulaC24H20Ag4Fe2N14O8S12hasbeensynthesizedandcharacterizedbysinglecrystalX-raydiffraction,elementalanalysisandIRspectroscopy.TheAgES2ringsconnecttwokindsofoctahedralgeometriesofFe(Ⅲ)ions,[Fe(NCS)6]^3-and[Fe(H2O)E(NCS)4]^-unitswithbridgingthiocyanateionsleadingto2-D[Ag4Fe2(SCN)12(H2O)2]^2-anionframework.Fourkindsofringsincludingtheunprecedentedthirty-twomemberedAg4Fe4(SCN)8ringssharecomersoredgesinthe2-Danionlayerstructure.AllthiocyanatescoordinatetothemetalionsaccordingtotheHSABprinciplewithNatomsbindingtotheFe(Ⅲ)ionsandwithSatomsbindingtoAg(I)ions.Pronoatedinacationsstabilizethelayerstructureascounterionsandhydrogenbondswereformedwithinthepronoatedinacationsdimerandbetweenthedimersandthelatticewaters.Crystaldata:Mr=1560.44,triclinic,P-↑1,a=0.76082(1)nm,b=0.9234nm,c=1.85611(4)nm,α=103.0170(10)°,β=93.7780(10)°,γ=97.4080(10)°,V=1.25385(3)nm^3,Z=1,μ(MoKα)=2.650mm^-1,Dc=2.067g·cm^-3,F(000)=758,R1=0.0412,wR2=0.1003.
简介:ThispaperproposesanadaptivejointsourceandchannelcodingschemeforH.264videomulticastoverwirelessLANwhichtakesintoaccounttheusertopologychangesandvaryingchannelconditionsofmultipleusers,anddynamicallyallocatesavailablebandwidthbetweensourcecodingandchannelcoding,withthegoaltooptimizetheoverallsystemperformance.Inparticular,sourceresilienceanderrorcorrectionareconsideredjointlyintheschemetoachievetheoptimalperformance.Andachannelestimationalgorithmbasedontheaveragepacketlossrateandthevarianceofpacketlossrateisproposedalso.Twooverallperformancecriteriaforvideomulticastareinvestigatedandexperimentalresultsarepresentedtoshowtheimprovementobtainedbythescheme.
简介:Arylhalidesareakindofextremelyvaluablecompoundsusedintransition-metal-catalyzedcouplingreactions,aswellasimportantstructuremotifsinmanynaturalproductsandmanufactureddrugs[1,2].Theclassicalapproachforpreparationofhaloarenesiselectrophilicaromaticsubstitution(EAS)usingvarioushalogenatingreagentsoroxidativehalogenationswithhalogenatingreagentgeneratedinsitufromhalidesandoxidants,suchasperoxide,oxygenandmeta-cholorperoxybenzoicacid(mCPBA)[3,4].However,harshreactionconditionsarerequiredforhalogenationoflessactivearomatics.orthoMetalationfollowedbyhalogenquenchingisanotherapproachforhalogenationofaromatics[5].However,thereareobviousdrawbacksforthesemethods,suchaslowregioselectivity,harshconditionsandevendangerousprocedures.Therefore,thedevelopmentofanalternativeandpracticalwayremainschallengeinorganicsynthesis.
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