学科分类
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42 个结果
  • 简介:Experimentshaveshownthattheionenergyobtainedbylaser–ionaccelerationcanbeoptimizedbychoosingeithertheappropriatepulsedurationortheappropriatetargetthickness.WedemonstratethatthisbehaviorcanbedescribedeitherbythetargetnormalsheathaccelerationmodelofSchreiberetal.orbytheradiationpressureaccelerationmodelofBulanovandcoworkers.Thestartingpointofourconsiderationsisthattheessentialpropertyofalasersystemforionaccelerationisitspulseenergyandnotitsintensity.Maybesurprisinglyweshowthathigherionenergiescanbereachedwithreducedintensities.

  • 标签: laser–ion ACCELERATION RELATIVISTIC LASER PLASMA INTERACTION
  • 简介:Anionbeamhastheuniquefeatureofbeingabletodeposititsmainenergyinsideahumanbodytokillcancercellsorinsidematerial.However,conventionalionacceleratorstendtobehugeinsizeandcost.Inthispaper,afutureintenselaserionacceleratorisdiscussedtomakethelaser-basedionacceleratorcompactandcontrollable.Theissuesinthelaserionacceleratorincludetheenergyefficiencyfromthelasertotheions,theionbeamcollimation,theionenergyspectrumcontrol,theionbeambunching,andtheionparticleenergycontrol.Inthestudy,eachcomponentisdesignedtocontroltheionbeamqualitybyparticlesimulations.Theenergyefficiencyfromthelasertoionsisimprovedbyusingasolidtargetwithafinesub-wavelengthstructureoranear-critical-densitygasplasma.Theionbeamcollimationisperformedbyholesbehindthesolidtargetoramulti-layeredsolidtarget.Thecontroloftheionenergyspectrumandtheionparticleenergy,andtheionbeambunchingaresuccessfullyrealizedbyamulti-stagelaser–targetinteraction.

  • 标签: INTENSE SHORT-PULSE LASER LASER ION ACCELERATION
  • 简介:MuonsproducedbytheBethe–HeitlerprocessfromlaserwakefieldacceleratedelectronsinteractingwithhighZmaterialshavevelocitiesclosetothelaserwakefield.Itispossibletoacceleratethosemuonswithlaserwakefielddirectly.Thereforeforthefirsttimeweproposeanall-optical‘GeneratorandBooster’schemetoacceleratetheproducedmuonsbyanotherlaserwakefieldtosupplyaprompt,compact,lowcostandcontrollablemuonsourceinlaserlaboratories.Thetrappingandaccelerationofmuonsareanalyzedbyone-dimensionalanalyticmodelandverifiedbytwo-dimensionalparticle-in-cell(PIC)simulation.Itisshownthatmuonscanbetrappedinabroadenergyrangeandacceleratedtohigherenergythanthatofelectronsforlongerdephasinglength.WefurtherextrapolatethedependenceofthemaximumaccelerationenergyofmuonswiththelaserwakefieldrelativisticfactorγandtherelevantinitialenergyE0.Itisshownthatamaximumenergyupto15.2GeVispromisingwithγ=46andE0=1.45GeVontheexistingshortpulselaserfacilities.

  • 标签: LASER WAKEFIELD ACCELERATION MUON SOURCE
  • 简介:Ashortoverviewofthetheoryofaccelerationofthinfoilsdrivenbytheradiationpressureofsuperintenselasersispresented.Asimplecriterionforradiationpressuredominanceatintensitiesaround5×1020Wcm-2isgiven,andthepossibilityforfastenergygainintherelativisticregimeisdiscussed.

  • 标签: LIGHT SAIL radiation pressure laser–plasma ACCELERATION
  • 简介:Duringourresearch,Ithasbeenfoundthatbodyaccelerationhasstrongrelationshipswiththehumanenergyexpenditure.Thispaperdiscussesthemethodstoassessphysicalactivityandconcludesthatforaccurateassessmentofphysicalactivityunderfreelivingconditionstherecentlyintroducedaccelerometerlooksmostpromising.Wedevelopedanewcomputerizedmachinetoassessthebodyactivityandenergyexpenditure.Testdatasofthetreadmillexperiment,respirationexperimentand5-kilometer-runningexperimenthavebeenarchieved,wefoundthatbodyaccerationintegralswithtimehaslinearrelationswithbodyenergyexpenture.

  • 标签: 身体素质 能量支出 运动医学 加速度
  • 简介:这篇论文讨论加速为解决非线性的抛物线的方程的含蓄的计划的反复的方法。二个新非线性的反复的方法由theimplicit明确的伪说出--牛顿(IEQN)方法和衍生物免费的含蓄明确的伪--牛顿(DFIEQN)方法被介绍,在哪个结果从linearization的线性方程能保存原来的部分微分方程的抛物线的特征。重复方法的反复的顺序能集成二次的联盟者到含蓄的计划的答案,这被证明。而且与Jacobian免费Newton-Krylov(JFNK)方法相比,theDFIEQN方法有一些优点,例如,它的实现是容易的,并且它与一个明确的系数矩阵给一个线性代数学的系统,以便线性(内部)重复没被限制为Krylov方法。由IEQN,DFIEQN,JFNK和Picard重复方法的计算结果在理论的证实和这些方法的表演的比较被介绍。

  • 标签: 非线性抛物线方程 误差图解 牛顿迭代法 计算数学
  • 简介:Sedimentationbasedprocessesarewidelyusedinindustrytoseparateparticlesfromaliquidphase.Sincetheadventofthe'Nanoworld'thedemandforeffectiveseparationtechnologieshasrapidlyrisen,callingforthedevelopmentofnewseparationconcepts,oneofwhichliesinhybridseparationusingthesuperpositionofamagneticfieldformagneticparticles.Possibleproductportfolioofsuchseparationconsistsofpigmentproduction,nanomagneticsproductionforelectronicsandbioseparation.Apromisingstepinthatdirectionismagneticfieldenhancedcakefiltration,whichhasbynowprogressedfrombatchtocontinuousoperation.Insedimentationprocessesinamassforcefieldthesettlingbehaviourofparticlesstronglydependsonphysico-chemicalproperties,concentrationandsizedistributionoftheparticles.ByadjustingthepH,theinterparticleforces,inparticulartheelectrostaticrepulsion,canbemanipulated.Forremanentmagneticparticlessuchasmagnetite,pre-treatmentinamagneticfieldcouldleadtoachangeofinterparticleinteractions.BymagnetizingtheparticlesapartfromvanderWaalsattractionandelectrostaticrepulsion,anadditionalpotentialisinduced,themagneticattraction,whichcouldeasilydominatetheotherpotentialsandresultinagglomerationintheprimaryminimum.Bysedimentationanalysis,awidespectrumofparameterslikepH,magneticfieldstrengthandconcentrationhavebeeninvestigated.Theresultsshowastrongincreaseofsedimentationvelocitybymagneticflocculationoftherawsuspension.Thisleadstoariseinthroughputduetotheaccelerationofsedimentationkineticsbyimpartinganon-chemicalinteractiontothephysico-chemicalpropertiesinthefeedstreamoftheseparationapparatus.

  • 标签: 磁絮凝法 磁性分离 残余氧化铁 加速沉淀
  • 简介:Wepresentamathematicalmethodforaccelerationworkspaceanalysisofcooperatingmulti-fingerrobotsystemsusingamodelofpoint-contactwithfriction.Anewunifiedformulationfromdynamicequationsofcooperatingmulti-fingerrobotsisderivedconsideringtheforceandaccelerationrelationshipsbetweenthefingersandtheobjecttobehandled.Fromthedynamicequation,maximumtranslationalandrotationalaccelerationboundsofanobjectarecalculatedundergivenconstraintsofcontactconditions,configurationsoffingers,andboundsonthetorquesofjointactuatorsforeachfinger.Here,therotationalaccelerationboundscanbeappliedasanimportantmanipulabilityindexwhenthemulti-fingerrobotgraspsanobject.Toverifytheproposedmethod,weusedasetofcasestudieswithasimplemulti-fingermechanismsystem.Theachievableaccelerationboundaryintaskspacecanbeobtainedsuccessfullywiththeproposedmethodandtheaccelerationboundarydependsontheconfigurationsoffingers.

  • 标签: 多指机器人 加速度工作空间 点接触摩擦模型 动力学方程
  • 简介:最近,放射压力加速(RPA)被建议了并且广泛地学习了,它证明那循环地极化了(CP)激光脉搏能在phase-stable-acceleration(PSA)加速单音精力充沛的离子捆从ultrathin陪衬的方法。自我组织的质子横梁能稳定地在10点在和一个平面目标的CP激光的相互作用被加速到GeV,这被发现<啜class=“a-plus-plus”>22W/cm<啜class=“a-plus-plus”>2。称为紧缩的激光血浆质子加速器(CLAPA)的一个工程最近被大多数在中国同意。激光的一个原型驾驶质子加速器(1~15MeV/1Hz)将基于PSA机制和血浆透镜在下一五年里在北京大学被造。它以后将为惯性的范围熔化为象癌症治疗,血浆成像和快点火那样的应用被升级到200兆电子伏。

  • 标签: 激光驱动 北京大学 粒子加速 质子加速器 激光等离子 惯性约束聚变
  • 简介:Thereal-timeidentificationofdynamicparametersisimportantforthecontrolsystemofspacecraft.Theeigensystemrealizationalgorithm(ERA)iscurrentlythetypicalmethodforsuchapplica-tion.Inordertoidentifythedynamicparameterofspacecraftrapidlyandaccurately,anacceleratedERAwithapartialsingularvaluesdecomposition(PSVD)algorithmispresented.InthePSVD,theHankelmatrixisreducedtodualdiagonalformfirst,andthentransformedintoatridiagonalmatrix.TheeigenvaluesarecomputedbythebisectionmethodintermsoftheSturmproperty,andthecorrespondingeigenvectorsareob-tainedbytheinverseiterationmethod.Finally,theeigenvaluesandtheeigenvectorsaretransformedintothesingularvaluesandthesingularvaluevectorsoftheoriginalmatrix.Anexampleforspacestationispresent-edtodemonstratetheefficacyandaccuracyoftheproposedalgorithm.

  • 标签: eigensystem REALIZATION algorithm PARTIAL SINGULAR value
  • 简介:Accelerationrecordandcharacteristicsofgroundmotionatanepicentraldistanceof200kmYu-HongTIAN(田玉红)andPei-DeWANG(王培德)(Instituteof...

  • 标签: RECORD and at DISTANCE epicentral GROUND
  • 简介:Thecompressedsensing(CS)ofaccelerationdatahasbeendrawingincreasingattentioningaittelemonitoringapplication.Insuchapplication,therestillexistsomechallengingissuesincludinghighenergyconsumptionofbody-worndeviceforaccelerationdataacquisitionandthepoorreconstructionperformanceduetononsparsityofaccelerationdata.Thus,thenovelschemeofcompressivesensingofaccelerationdataisneededurgentlyforsolutionsthatarefoundtotheseissues.

  • 标签:
  • 简介:Theconventionalpseudo-staticapproachoftenneglectstheeffectoftheverticalseismicaccelerationonthestabilityofaslope,butsomeanalysesunderplane-strain(2D)conditionsshowasignificanteffectontheslopestability.Thepurposeofthisstudyistoinvestigatetheeffectoftheverticalaccelerationonthesafetyofthree-dimensional(3D)slopes.Inthestrictframeworkoflimitanalysis,a3Dkinematicallyadmissiblerotationalfailuremechanismisadoptedherefor3Dhomogeneousslopesinfrictional/cohesivesoils.Asetofstabilitychartsispresentedinawiderangeofparametersfor3Dslopesundercombinedhorizontalandverticalseismicloadingconditions.Accountingfortheeffectsoftheverticalseismicacceleration,thedifferenceinsafetyfactorsfor3Dslopescanexceed10%,whichwillsignificantlyoverestimatethesafetyofthe3Dslopes.

  • 标签: 边坡稳定性 三维运动学 地震加速度 垂直加速度 拟静力法 平面应变
  • 简介:Onthebasisofasinusoidalmodelofthedisturbedhorizontalacceleration,thespectrumcharacteristicsofmisalignedangleandhorizontalaccelerationcorrectionareanalyzed.Inanairbornegravimetrytest,themisalignedangleofplatformandhorizontalaccelerationcorrectionarecalculated.Theyare5'and3mGal,respectively,whentheflightisstable.

  • 标签: HACC 水平加速度修正 空气传播 重力测量 计算 范围分析
  • 简介:Recentlytherehasbeengreatprogressinlaser-drivenplasma-basedacceleratorsbyexploitinghigh-powerlasers,whereelectronbeamscanbeacceleratedtomulti-GeVenergyinacentimeter-scaleplasmaduetothelaserwakefieldaccelerationmechanism.While,todate,worldwideresearchonlaserplasmaacceleratorshasbeenfocusedonthecreationofcompactparticleandradiationsourcesforbasicsciences,medicalandindustrialapplications,thereisgreatinterestinapplicationsforhigh-energyphysicsandastrophysics,exploringunprecedentedhigh-energyfrontierphenomena.Inthiscontext,wepresentanoverviewofexperimentalachievementsinlaserplasmaaccelerationfromtheperspectiveoftheproductionofGeV-levelelectronbeams,anddeducethescalingformulascapableofpredictingexperimentalresultsself-consistently,takingintoaccountthepropagationofarelativisticlaserpulsethroughplasmaandtheacceleratingfieldreductionduetobeamloading.Finally,wepresentdesignexamplesfor10-GeV-levellaserplasmaacceleration,whichisexpectedinnear-termexperimentsbymeansofpetawatt-classlasers.

  • 标签: ELECTRON BEAM loading GeV-level ELECTRON BEAM
  • 简介:Ultrashortlaserpulsesareusedtocreatesurfacestructuresonthin(25μm)silicon(Si)wafers.Scanningthewaferwithagalvanometricmirrorsystemcreateslargehomogeneouslystructuredareas.Thevarietyofstructureshapesthatcanbegeneratedwiththismethodisexemplifiedbytheanalysisofshape,heightanddistanceofstructurescreatedintheambientmediaairandisopropanol.Astudyofthecorrelationbetweenstructureheightandremainingwaferthicknessispresented.Thecomparativelyeasymanufacturingtechniqueandthestructurevarietythatallowsforcustom-tailoredtargetsshowgreatpotentialforhighrepetitionrateionaccelerationexperiments.

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