简介:Numericalestimatesforelectronsandmesonsparticle–antiparticlecreationfromvacuuminthepresenceofstrongelectromagneticfieldsarederived,usingthecompleteprobabilitydensityrelationofPopov’simaginarytimemethod(Popov,JETPLett.13,185(1971);Sov.Phys.JETP34,709(1972);Sov.Phys.JETP35,659(1972);PopovandMarinov,Sov.J.Nucl.Phys.16,449(1973);JETPLett.18,255(1974);Sov.J.Nucl.Phys.19,584(1974));(Popov,Phys.Let.A298,83(2002)),andwithintheframeworkofanexperimentalsetupliketheE144(Burkeetal.,Phys.Rev.Lett.79,1626(1997)).Theexistenceofcrossingpointamongpaircreationefficiencycurvesofdifferentphotonenergiesandtheroleofodd/evenmultiphotonordersintheproductionratesarediscussed.Finallyakindoftunabilityprocessbetweenthetwocreationprocessesisdiscussed.
简介:Anenvironmentallyfriendlyprecursor,adenosine,hasbeenusedasadualsourceofCandNtosynthesizenitrogen-dopedcarboncatalystwith/withoutFe.Ahydrothermalcarbonizationmethodhasbeenusedandwateristhecarbonizationmedia.Themorphologyofsampleswith/withoutFecomponenthasbeencomparedbyHRTEM,andtheresultshowsthatFecanpromotethegraphitizationofcarbon.Furtherelectro-chemicaltestshowsthattheoxygenreductionreaction(ORR)catalyticactivityofFe-containingsample(C–FeN)ismuchhigherthanthatoftheFe-freesample(C–N).Additionally,theintermediatesofC–FeNformedduringeachsyntheticprocedurehavebeenthoroughlycharacterizedbymultiplemethods,andthefunctionofeachprocedurehasbeendiscussed.TheC–FeNsampleexhibitshighelectro-catalyticstabilityandsuperiorelectro-catalyticactivitytowardORRinalkalinemedia,withitshalf-wavepotential20mVlowerthanthatofcommercialPt/C(40wt%).Itisfurtherincorporatedintoalkalinepolymerelectrolytefuelcell(APEFC)asthecathodematerialandledtoapowerdensityof100mW/cm~2.
简介:Itisidentifiedthatbarelypassingelectronsarethedriveofthee-Gshbones,ratherthanthebarelytrappedelectronsatlowfrequency.Thefrequencyjumpine-Bshboneexperimentsisreproducedandanalyzed.Itisfoundthatthee-Bshbonefrequencyincreaseswiththehotelectronenergy,whichisconsistentwiththeexperiments.Thegrowthrateofthemode(m=2,n=2)isgreaterthanthatofthemode(m=1,n=1).
简介:Afusionbreedermightbeanessentialintermediateapplicationoffusionenergyatearlierterm,sinceithasthepotentialtoprovideplentyofcommercialfissilefuel.Basedonfusionphysicsandtechnologiesavailableatpresentandinthenearfuture,therealisticfusionexperimentalbreeder,FEB-Ewasdesigned.
简介:Inthecontextofthetop-color-assistedtechnicolor(TC2)model,theflavor-changingneutral-current(FCNC)interactioninducedbythetop-higgs(h_t~0)arepredictedattreelevel.Westudytherelevantprocessesofe~+e~-(γγ)→th_t~0attheInternationalLinearCollider(ILC).ItisfoundthattheserareprocessesproductionratescanbeenhancedsignificantlyintheTC2model.Especiallyfortheprocessγγ→th_t~0,thetotalcrosssectionwillreachafewfbinthereasonableparameterspace.Wealsocalculatethedistributionsoftransversemomenta,pseudo-rapidandinvariantmassofthetop-higgs.Inviewofthemaindecaymodesoftop-higgsform_(h_t~0)<2m_t,weEndthattherewillbeseveralhundredsFCNCeventsproducedattheILCwithannuallyintegralluminosityof500fb~(-1).Duetothecleanbackground,suchFCNCsignalscanpossiblybedetectedattheILC.
简介:Variousagriculturalcropresiduesincludingcornstover,corncob,andsorghumstalkwithamoisturecontentof75wt%weresubjectedtoalongpretreatment(12-60h)withsupercriticalCO2(scCO2),atlowtemperature(50-80℃)andapressureof17.5-25.0Mpa.Thesugaryieldsfromtheenzymatichydrolysis(EH)ofthepretreatedsampleswereasmuchasthree-tofourfoldgreaterthanthoseaffordedbytherawmaterials.However,whenpretreatmentwasconductedwithinashorttime(e.g.0.5h),aspreviouslyreportedintheliterature,onlyaslightincreaseintheEHsugaryieldswasobserved.TheproposedscCO2pretreatmentmechanismdemonstratedtheroleofmoistureinthesystem.Wetting,softening,andswellingwereobservedtomainlyaffectthelignocellulosewhenasuitableamountofwaterwasadded.Finally,thesampleswereanalysedbyX-raydiffractionandscanningelectronmicroscopy,beforeandafterpretreatment,toinvestigatethechangesinthemicroscopicstructureofthebiomass.
简介:Anovelgas-phaseelectrocatalyticcellcontainingalow-temperatureprotonexchangemembrane(PEM)wasdevelopedtoelectrochemicallyconvertCO2intoorganiccompounds.TwodifferentCu-basedcathodecatalysts(CuandCu-C)werepreparedbyphysicalvapordepositionmethod(sputtering)andsubsequentlyemployedforthegas-phaseelectroreductionofCO2atdifferenttemperatures(70-90℃).ThepreparedelectrodesCuandCu-CwerecharacterizedbyX-raydiffraction(XRD),X-rayphotoemissionspectroscopy(XPS)andscanningelectronmicroscopy(SEM).Asrevealed,CuispartiallyoxidizedonthesurfaceofthesamplesandtheCuandCu-Ccathodiccatalystswerecomprisedofaporous,continuous,andhomogeneousfilmwithnanocrystallineCuwithagrainsizeof16and8nm,respectively.Theinfluenceoftheappliedcurrentandtemperatureontheelectro-catalyticactivityandselectivityofthesematerialswasinvestigated.Amongthetwoinvestigatedelectrodes,thepureCucatalystfilmshowedthehighestCO2specificelectrocatalyticreductionratesandhigherselectivitytomethanolformationcomparedtotheCu-Celectrode,whichwasattributedtothehigherparticlesizeoftheformerandlowerCuO/Curatio.Theobtainedresultsshowpotentialinterestforthepossibleuseofelectrical「enewableenergyforthetransformationofCO2intovaluableproductsusinglowmetalloadingCubasedelectrodes(0.5mgCucm2)preparedbysputtering.
简介:Inthepresentstudy,astatisticalinvestigationiscarriedouttoexplorewhetherthereisarelationshipbetweenthecriticalfrequency(foEs)ofthesporadic-ElayerthatisoccasionallyseenontheEregionoftheionosphereandthequasibiennialoscillation(QBO)thatflowsintheeast–westdirectionintheequatorialstratosphere.Multipleregressionmodelasastatisticaltoolwasusedtodeterminetherelationshipbetweenvariables.Inthismodel,thestationarityofthevariables(foEsandQBO)wasfirstlyanalyzedforeachstation(CocosIsland,Gibilmanna,NiueIsland,andTahiti).Then,acointegrationtestwasmadetodeterminetheexistenceofalong-termrelationshipbetweenQBOandfoEs.Afterverifyingthepresenceofalong-termrelationshipbetweenthevariables,themagnitudeoftherelationshipbetweenvariableswasfurtherdeterminedusingthemultipleregressionmodel.Asaresult,itisconcludedthatthevariationsinfoEswereexplainablewithQBOmeasuredat10hPaaltitudeattherateof69%,94%,79%,and58%forCocosIsland,Gibilmanna,NiueIsland,andTahitistations,respectively.ItisobservedthatthevariationsinfoEswereexplainablewithQBOmeasuredat70hPaaltitudeattherateof66%,69%,53%,and47%forCocosIsland,Gibilmanna,NiueIsland,andTahitistations,respectively.
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:TheCprogramminglanguageisexpressiveandflexible,butnotsafe;asitsexpressivepowerandflexibilityareobtainedthroughunsafelanguagefeatures,andimproperuseofthesefeaturescanleadtoprogrambugswhosecausesarehardtoidentify.SinceCiswidelyused,anditisimpracticaltorewriteallexistingCprogramsinsafelanguages,sowaysmustbefoundtomakeCprogramssafe.ThispaperdealswiththeunsafefeaturesofCandpresentsasurveyonexistingsolutionstomakeCprogramssafe.Wehavestudiedbinary-levelinstrumentationtools,sourcecheckers,source-levelinstrumentationtoolsandsafedialectsofC,andpresentacomparisonofdifferentsolutions,summarizedthestrengthsandweaknessesofdifferentclassesofsolutions,andshowmeasuresthatcouldpossiblyimprovetheaccuracyoralleviatetheoverheadofexistingsolutions.
简介:ThefirststarsintheearlyUniversewereformedabout400millionyearsafterthebigbang.VerificationoftheexistenceofthesestarsisimportantforourunderstandingoftheevolutionoftheUniverse[1].IthasbeenpredictedthatforPopulation-IIIstellarproductionyields,theabundancesofodd-Zelementsareremarkablydeficientcomparedtotheiradjacenteven-Zelements[2].Astronomersaresearchingforlong-lived,lowmassstarswiththeuniquenucleosyntheticpatternmatchingthepredictedyields[3].