简介:DNAcondensationisanimportantprocessinmanyfieldsincludinglifesciences,polymerphysics,andappliedtechnology.Inthenucleus,DNAiscondensedintochromosomes.Inpolymerphysics,DNAistreatedasasemi-flexiblemoleculeandapolyelectrolyte.Manyagents,includingmulti-valentcations,surfactants,andneutralpoorsolvents,cancauseDNAcondensation,alsoreferredtoascoil–globuletransition.Moreover,DNAcondensationhasbeenusedforextractionandgenedeliveryinappliedtechnology.ManyphysicaltheorieshavebeenpresentedtoelucidatethemechanismunderlyingDNAcondensation,includingthecounterioncorrelationtheory,theelectrostaticzippertheory,andthehydrationforcetheory.Recentlyseveralsingle-moleculestudieshavefocusedonDNAcondensation,sheddingnewlightonoldconcepts.Inthisdocument,themulti-fieldconceptsandtheoriesrelatedtoDNAcondensationareintroducedandclarifiedaswellastheadvancesandconsiderationsofsingle-moleculeDNAcondensationexperimentsareintroduced.
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简介:题目:一种多振子超声电机的设计目的:对超声电机而言,当多个压电振子并联时,由于以同一设计方案制作的电机振子往往具有不同的动态特性,因此会使得多振子电机的效率有所下降。即多振子电机工作的关键是如何使多个振子协同一致地驱动转子。为提高集成型多振子电机的效率和简化电机结构,提出一种构造贴片式多振子旋转超声电机的方法。创新点:1.提出圆周面内驱动的概念,发展已有的面内驱动概念(x-y面);2.提出一种模态转换方法,通过多个振子弯曲振动的叠加形成设计电机的扭转振动;3.电机工作时,不仅各个振子处于共振状态,而且连接而成的定子同样处于共振状态,有利于提高电机的效率;4.验证多振子同步驱动的机理。方法:1.振子采用贴片式结构,由极化方向沿厚度方向的压电陶瓷和金属基体粘结而成;与使用兰杰文振子相比,使用贴片式振子易于简化电机的结构。2.各个振子首尾相连形成电机的定子,既可用于构造直线电机,又可转换成旋转电机。3.通过有限元方法对不同振子数构成的电机定子进行性能比较,并且分析设计电机的驱动机理;此外,通过仿真分析确定电机的最优尺寸。4.根据设计结果,加工原理样机,并且对加工的样机进行实验研究,探讨设计方法的可行性。结论:1.根据仿真分析结果,最终加工的电机定子包含5个振子。2.定子中各个振子的振动特性完全相同,振子同步工作。3.样机定子的内径为28mm,外径为35mm,高为30min;测得定子的纵振和扭转频率分别为44.42kHz和43.83kHz;当激励电压的频率为43.9kHz、峰值为100V时,电机的空载转速为45r/min,堵转力矩为0.3N·m,最大效率约为30%。4.本文所设计的电机,是一种多振子并行驱动的整体式电机,具有结构紧凑和多�
简介:在这份报纸,我们在存在上解决一个问题结合线性多步方法(LMSM)的symplecticity,否定结果被获得。[从作者抽象]
简介:Bymeansoffirst-principlesdensityfunctionaltheory(DFT)calculationsandmoleculardynamics(MD)simulations,aseriesofcoronalmulti-walledsiliconnanotubes(MWSiNTs)withoutorwithhydrogenterminationsaresystematicallyidentified.Notably,coronalMWSiNTs,wheretheinteractionbetweenthewallsispreferablethroughcovalentbondsratherthanweakinteraction,showbetterstabilitythanCNT-likeSiNTs.Moreover,theyexhibitgoodelasticitywithsmallYoung’smodulus.Theinvestigationoftheelectronicstructuredemonstratesthattheypresentmetalliccharacteristics,whichisinstrikingcontrasttobulksilicon.Thus,theMWSiNTsmayfindimportantapplicationsinelectronicdevices.
简介:InthefieldofComptonscatterimaging,theproblemofhowtogetameaningfulimagefromlarge-scaleobjectisstillnotfullysttled.Thedifficultymainlyliesinthemethodofthecompensationoftheattenuation,Basedontheprincipleofsmall-angleforwardscattering,anewattenuationcorrectionmethodisdeducedinthispaper,wecandistinguishairfromothermaterialsevenitisdeepinsidealarge-scaleobject.Toverifyourmethod,wedesignamodelofaone-meter-longobjectandperformMonteCarlosimulationswithMCNPsoftware.
简介:GyroscopicdynamicsystemcanbeintroducedtoHamiltoniansystem.BasedonanadjointsymplecticsubspaceiterationmethodofHamiltoniangyroscopicsystem,anadjointsymplecticsubspaceiterationmethodofindefiniteHamiltonianfunctiongy-roscopicsystemwasproposedtosolvetheeigenvalueproblemofindefiniteHamiltonianfunctiongyroscopicsystem.ThecharacterthattheeigenvaluesofHamiltoniangyroscopicsystemareonlypureimaginaryorzerowasused.TheeigenvaluesthatHamiltonianfunctionisnegativecanbeseparatedsothattheeigenvalueproblemofpositivedefiniteHamiltonianfunctionsystemwaspresented,andanadjointsymplecticsubspaceiterationmethodofpositivedefiniteHamiltonianfunctionsystemwasusedtosolvetheseparatedeigenvalueproblem.Therefore,theeigenvalueproblemofindefiniteHamiltonianfunctiongyroscopicsystemwassolved,andtwonumericalexamplesweregiventodemonstratethattheeigensolutionsconvergeexactly.
简介:BasedonArnoldi’smethod,aversionofgeneralizedArnoldialgorithmhasbeendevel-opedforthereductionofgyroscopiceigenvalueproblems.Byutilizingtheskewsymmetryofsystemmatrix,averysimplerecurrencescheme,namedgyroscopicArnoldireductionalgorithmhasbeenob-tained,whichisevensimplerthantheLanczosalgorithmforsymmetriceigenvalueproblems.Thecomplexnumbercomputationiscompletelyavoided.Arestarttechniqueisusedtoenablethereductionalgorithmtohaveiterativecharacteristics.Ithasbeenfoundthattherestarttechniqueisnotonlyef-fectivefortheconvergenceofmultipleeigenvaluesbutitalsofurnishesthereductionalgorithmwithatechniquetocheckandcomputemissedeigenvalues.Bycombiningitwiththerestarttechnique,theal-gorithmismadepracticalforlarge-scalegyroscopiceigenvalueproblems.Numericalexamplesaregiv-entodemonstratetheeffectivenessofthemethodproposed.
简介:Amild,regioselective1,3-dipolarcycloadditionprotocolforthepreparationofphenylselenomethylisoxazolinesthroughsubstitutedallylphenylselenidesandnitrileoxideswasreported.
简介:Atheoreticalinvestigationiscarriedouttostudytheexistence,formationandbasicpropertiesofionacoustic(IA)doublelayers(DLs)inamagnetizedbi-ionplasmaconsistingofwarm/coldionsandBoltzmanndistributedelectrons.Basedonthereductiveperturbationtechnique,anextendedKortewegde-Vries(KdV)equationisderived.Thepropagationoftwopossiblemodes(fastandslow),andtheirevolutionareinvestigated.Theeffectsofobhqueness,magnitudeofthemagneticfield,ionconcentration,polarityofions,andiontemperatureontheIADLprofileareanalyzed,andthentherangesofparametersforwhichtheIADLsexistareinvestigatedindetails.
简介:Amulti-channelACpowerSupplycontrolerdevelopedrecentlybyuswasintrodueedbrieftyinthispaper.Thiscontrollerisacomputercontrolledmulti-electronic-switchdevice.Thecontrollercontains16independentchannelsinastandardbox(440W×405D×125Hmm).Thereisanelectronicswitchineachchannel,theratedloadpoweris≤1kW.Themainfunctionofthecontrolleristosetthestateofelectronicswitch(ON/OFF)
简介:TheneutronTimeOfFlight(nTOF)facilityatCERNisahighfluxspallationneutronsourcecommissionedinNov2000andAPr2001.ForthecommissioningphasesaninnovativemultipurposeDAQsystemwasdevelopedandused.Thissystemiscapableofhandlinghighdatarated(10Mb/s)withtheuseoftheNationalInstrumentsPCI-VXIinterfaceboardtocommunicatewiththeVMEcrates.ThegraphicaluserinterfaceisbasedonJava^TMandROOTallowingimmediatevisualizationofthedataandprovidingaflexiblewayofcreatingconfigurationsforvariousexperimentalsetups.
简介:Longwavesgeneratedbyamovingatmosphericpressuredistribution,associatedwithastorm,incoastalregionareinvestigatednumerically.Forsimplicitythemovingatmosphericpressureisassumedtobemovingonlyinthealongshoredirectionandthebeachslopeisassumedtobeaconstantintheon-offshoredirection.Bysolvingthelinearshallowwaterequationsweobtainnumericalsolutionsforawiderangeofphysicalparameters,includingstormsize(2a),stormspeed(U),andbeachslope(α).Basedonthenumericalresults,itisdeterminedthatedgewavepacketsaregeneratedifthestormspeedisequaltoorgreaterthanthecriticalvelocity,Ucr,whichisdefinedasthephasespeedofthefundamentaledgewavemodewhosewavelengthisscaledbythewidthofthestormsize.ThelengthandthelocationofthepositivelymovingedgewavepacketisroughlyUt/2≤y≤Ut,whereyisinthealongshoredirectionandtisthetime.Oncetheedgewavepacketisgenerated,thewavelengthisthesameasthatofthefundamentaledgewavemodecorrespondingtothestormspeedandisindependentofthestormsize,whichcan,however,affectthewaveamplitude.Whenthestormspeedislessthanthecriticalvelocity,theprimarysurfacesignatureisadepressiondirectlycorrelatedtotheatmosphericpressuredistribution.