简介:Carbon-supportedPdnanoparticleswerepreparedbymicrowaveheating-glycolreductionmethod,andcharacterizedbyawidearrayofexperimentaltechniquesincludingX-raydiffractionspectroscopy(XRD)andtransmissionelectronmicroscopy(TEM).TheelectrooxidationbehaviorsofethanolonthePd/Celectrodeinalkalinemediawereinvestigatedusingcyclicvoltammetry(CV),chronoamperometry(CA),electrochemicalimpedancespectroscopy(EIS)andsinglecellperformancemethods.Pd/Celectrodeforethanoloxidationshowedhighelectro-catalyticactivityandlongtermstability.However,itisobservedthatthecurrentdensitydecreaseswiththeincreasingofthepotentialandnegativeimpedancepresentsinthepotentialfrom-0.1to0.1V.Thedecreasingcurrentdensityandthenegativeimpedancecouldbeduetotheadsorbedintermediatesspeciesthatinhibitedthefurtheroxidationofethanol.BasedonthechemicalreactionanalysisandEISspectra,equivalentcircuitsrelatingtovariouspotentialzoneshavebeenobtained.TheseresultsrevealthedynamicadsorptionofintermediatesspeciesonPdsurfaces.Significantly,itisclarifiedthattheadsorptionbehaviorbeginsfromthemaximumcatalysisofelectro-catalysisandendsintheformationofthepalladium(II)oxidelayerontheelectrodesurface.
简介:The12C+13Csystemhasbeenstudiedextensively,becauseofthesimilarityoftheentrancechanneltotheastrophysicallyimportant12C+12Creaction[1??3].Untilnow,threedifferentmethodshavebeenexploitedtoperformthefusioncrosssectionmeasurementsfor12C+13CundertheCoulombbarrier:(1)measuringtheyieldofcharacteristicrays,(2)thetotal-rayyieldsusingNaIsummingdetectorsand(3)theactivityofthereactionresidue24Na(T1=2=15.0h).Recently,thefusioncrosssectionof12C+13Chasbeenmeasureddownto0.9nbthroughtheactivitymeasurementbyourgroup[4].Althoughthestatisticalmodelcalculationsinallthesethreemethodshavebeenroutinelyusedtoconverttheobservedpartialcrosssectionsintothetotalfusioncrosssections[5],thesystematicuncertaintyinducedbythestatisticalcorrectionshasnotbeenstudiedverywell.
简介:以恒电位法在pH=9.0碱性水溶液中碳纤维簇电极上镀单层锌,在含有组氨酸和电解氧化锌镀层下原位合成了锌-组氨酸-羟基络合物修饰碳纤维电极,模拟了生物酶识别痕量的硫氢酸根离子,优化了电极制备的条件。建立了开路电位测定硫氢酸根离子的方法,在中性水溶液中,该电极以开路电位变化响应注入溶液中的硫离子浓度,并可用能斯特方程描述开路电位变化的规律。方法的最低检出限为1.0×10μmol/L,检测范围为1.0×10~1.0×10-18mol/L,相对标准偏差为3.5%。对实际样品中硫氢酸根离子检测结果为1.12×10-13mol/L,加标回收率为109.2%。研制的电化学传感器具有响应快速,灵敏度高,检出限低,检测范围宽,仪器简单方便等特点。
简介:雷纳兹应力(RS)上的积极偏爱的效果和它在边血浆的光线的狂暴的运输上的效果(r/a?=?0.9)并且在tokamak的血浆的擦去层(太阳)区域被调查。光线并且poloidal电场(Er,Ep)和离子浸透电流(我s)被多种用途的探查(MPP)测量。这根探针在IR-T1tokamak第一次被制作并且构造。这根探针的大多数优点是Er和Ep能在单个射击在不同半径被测量。因此不同半径的信息能与高精确相比。偏爱电压在V偏爱?=?200V和它与在r/a被修理的limiter偏爱被使用了?=?0.9。而且,之间的阶段差别光线并且MPP检测的RS光谱的poloidal电场,和时间的进化被计算。边上的RS大小(r/a?=?0.9)多于它在太阳的价值(r/a?=?1.02)。与应用偏爱200V,RS和Er和Ep被增加,当光线的狂暴的运输同时被减少时。因此,RS影响光线的骚乱,这能被结束。RS光谱的时间的进化证明RS的频率在r/a被增加并且到达它的最高的价值?=?0.9面对偏爱。
简介:本文得到了C*-代数值度量空间中的一些不动点定理,其结果改进并推广了马振华等人发表在2014年《不动点理论及其应用》一文中的工作.而且,运用所得到的结果,获得了一类常见积分方程解的存在性和唯一性定理.
简介:PtRu/SnO2/Ccatalystwaspreparedinapolyolprocess,followedbyreductiontreatmentandalkalineetching.X-raydiffraction,transmissionelectronmicroscopewithenergydispersivespectrometerandXrayphotoelectronspectroscopywereusedtocharacterizethemorphology,structureandcompositionofthecatalysts.COandmethanolelectro-oxidationactivitiesofthecatalystswereevaluatedbyCOstrippingvoltammetry,cyclicvoltammetryandchronoamperometrymeasurements.ReductiontreatmentofthepreparedPtRuSnO2/CcatalystinapolyolprocessinducedtheenrichmentofSnonthesurface,inhibitingmethanoldissolutionandCOadsorptiononPt.AlkalineetchingremovedSnorSnOxandthusexposedPtRuonthesurface,resultinginenhancedactivitiesforCOandmethanolelectro-oxidationduetothesynergyeffectsofPtRuonthesurfaceandSnspeciesbeneath.
简介:ThispaperconsidersthereliablecontroldesignforT-Sfuzzysystemswithprobabilisticactuatorsfaultsandrandomtime-varyingdelays.Thefaultsofeachactuatoroccursrandomlyanditsfailureratesaregovernedbyasetofunrelatedrandomvariablessatisfyingcertainprobabilisticdistribution.Intermsoftheprobabilisticfailuresofeachactuatorandtime-varyingrandomdelays,newfaultmodelisproposed.Basedonthenewfuzzymodel,reliablecontrollerisdesignedandsufficientconditionsfortheexponentiallymeansquarestability(EMSS)ofT-SfuzzysystemsarederivedbyusingLyapunovfunctionalmethodandlinearmatrixinequality(LMI)technique.Itshouldbenotedthattheobtainedcriteriadependonnotonlythesizeofthedelay,butalsotheprobabilitydistributionofit.Finally,anumericalexampleisgiventoshowtheeffectivenessoftheproposedmethod.
简介:ThisstudyshowsthepreparationofaTiO_2coatedPt/C(TiO_2/Pt/C)byatomiclayerdeposition(ALD),andtheexaminationofthepossibilityforTiO_2/Pt/Ctobeusedasadurablecathodecatalystinpolymerelectrolytefuelcells(PEFCs).CyclicvoltammetryresultsrevealedthatTiO_2/Pt/Ccatalystwhichhas2nmprotectivelayershowedsimilaractivityfortheoxygenreductionreactioncomparedtoPt/Ccatalystsandtheyalsohadgooddurability.TiO_2/Pt/Cpreparedby10ALDcyclesdegraded70%after2000Accelerateddegradationtest,whilePt/Ccorroded92%inthesameconditions.TiO_2ultrathinlayerbyALDisabletoachieveagoodbalancebetweenthedurabilityandactivity,leadingtoTiO_2/Pt/CasapromisingcathodecatalystforPEFCs.ThemechanismoftheTiO_2protectivelayerusedtopreventthedegradationofPt/Cisdiscussed.
简介:众多B2C网站已建立起会员等级制度,并据此向买家提供价格折扣。但会员等级制模型仅考虑买家交易金额,无法全面反映买家在线购买历史(onlinepurchasehistory),故不能准确提供差异化折扣。针对上述问题,提出了一种面向B2C电子商务的差异化折扣模型,该模型包含能体现买家在线购买历史的交易、退单、推荐购买、晒单等四个指标,将买家在线购买历史聚合为一个综合值,进而通过min-max标准化方法进行线性转换,将转换后的聚合值与会员等级基准折扣结合得到最终的差异化折扣,从而使得B2C网站可向同级别会员实施更精准的一对一营销和价格歧视策略。以京东商城为背景的仿真实验结果证明了本文新模型的有效性。
简介:传统的应用稳定性理论对横流不稳定性转捩现象的预测很难与现代CFD并行化计算结合,为了解决这个问题,文章基于SA-γ-—Re_(θt)转捩模型,使用不可压三维边界层相似性解实现横流位移损失厚度Reynolds数在流场中的当地化求解,结合亚音速试验数据-C1准则构建横流不稳定性转捩判据,从而实现了横流不稳定性转捩预测方法的当地化并行求解.首先采用SA-γ-—Re_(θt)转捩模型对NLF(1)-0416翼型进行了流向转捩预测,证实了该模型的正确性.然后应用所建立的横流转捩模型对45°前缘后掠角的NLF(2)-0415无限展长机翼和DLR-F5机翼,以及标准6∶1椭球标模进行了横流不稳定转捩数值模拟,计算结果显示转捩位置均与试验数据吻合较好,证明了文章所建立的方法在不可压边界层转捩预测具有较高的预测精度.
简介:近年来,以聚多巴胺球支撑的纳米复合材料越来越受到人们的关注。聚多巴胺球有表面功能化基团如-OH、-NH4等,决定了聚多巴胺球可以充当多种纳米复合材料的活性载体。利用聚多巴胺良好的还原性制备并负载银纳米粒子于聚多巴胺球表面,制备出的新型复合材料银纳米粒子一聚多巴胺球(以下简写为Ag@pdop)。Au修饰电极和银纳米粒子对过氧化氢的还原反应均具有很好的催化性能,利用两者特点将其复合制备修饰电极实现对H2O2的无酶传感,检测灵敏度达到了14.7μA/(mm01·L。),检出限可达11.8〉mol/L,线性范围0.2~6.0mmol/L,检测结果及抗干扰能力均令人满意。
简介:Toconsidertheanisotropicdamageinfatigue,animprovedboom-panelmodelispresentedtosimulatearepresentativevolumeelement(RVE)intheframeworkofcontinuumdamagemechanics.TheanisotropicdamagestateoftheRVEisdescribedbythecontinuityextentsofboomsandpanels,whosedamageevolutionsareassumedtobeisotropic.Thenumericalimplementationisproposedonthebasisofdamagemechanicsandthefiniteelementmethod.Finally,theapproachisappliedtothefatiguelifepredictionof2A12-T4aluminiumalloyspecimenundercyclicloadingoftension-torsion.Theresultsindicateagoodagreementwiththeexperimentaldata.