简介：

简介：

简介：

简介：Basedondynamicrupturesimulationsonaplanarfaultinahomogeneoushalf-space,weinvestigatedthenucleationprocessesusingthetime-weakeningfrictionlaw.Boththecharacteristictimeandtherupturespeedinthenucleationasperityplayanimportantroleindeterminingrupturebehaviorsonafaultplanefollowingthetime-weakeningfrictionlaw,withwhichrupturestartsfromasinglepointinthenucleationasperityandpropagatesatagivenspeedtowardtheboundaryofthenucleationarea.Rupturewithasmallcharacteristictimeoralargerupturespeedinthenucleationasperitypropagatesearlierfromthehypocenter.Rupturefollowingtheslipweakeningfrictionlawrequiresasmallerradiusofnucleationpatchtohavesimilarrupturefrontcontoursofthetime-weakeningfrictionlaw.Eveniftherupturevelocityinthenucleationpatchofthetime-weakeningfrictionlawincreasestoinfinity,thepeaksliprateinthenucleationasperityissmallerthanthatoftheslip-weakeninglaw.Thepeakgroundvelocitydistributionsofrupturesfollowingthetwofrictionlawsarealsocompared.

简介：

简介：Backconversionisanintrinsicphenomenoninnonlinearfrequencydown-conversionprocesses.However,thephysicalreasonforitsoccurrenceisnotwellunderstood.Here,wetheoreticallyrevealthatbackconversionistheresultofaπ-phasejumpassociatedwiththedepletionofoneinteractingwave.Bysuppressingtheidlerphasejumpthroughadeliberatecrystalabsorption,thebackconversioncanbeinhabited,thusenhancingtheconversionefficiencyfromthepumptothesignal.TheresultspresentedinthisLetterwillfurthertheunderstandingofnonlinearparametricprocessesandpavethewaytowardthedesignofhighlyefficientdown-conversionsystems.

简介：

简介：Asanimportantelementinsustainablebuildingdesign,thebuildingenvelopehasbeenwitnessingaconstantshiftinthedesignapproach.Integratingmulti-objectiveoptimization(MOO)intothebuildingenvelopedesignprocessisverypromising,butnoteasytorealizeinanactualprojectduetoseveralfactors,includingthecomplexityofoptimizationmodelconstruction,lackofadynamic-visualizationcapacityinthesimulationtoolsandconsiderationofhowtomatchtheoptimizationwiththeactualdesignprocess.Toovercomethesedifficulties,thisstudyconstructedanintegratedbuildingenvelopedesignprocess(IBEDP)basedonparametricmodelling,whichwasimplementedusingGrasshopperplatformandinterfacestocontrolthesimulationsoftwareandoptimizationalgorithm.ArailwaystationwasselectedasacasestudyforapplyingtheproposedIBEDP,whichalsoutilizedagrid-basedvariabledesignapproachtoachieveflexibleoptimumfenestrations.Tofacilitatethestepwisedesignprocess,anovelstrategywasproposedwithatwo-stepoptimization,whichoptimizedvariouscategoriesofvariablesseparately.Comparedwithaone-stepoptimization,thoughtheproposedstrategyperformedpoorlyinthediversityofsolutions,thequantitativeassessmentofthequalitiesofPareto-optimumsolutionsetsillustratesthatitissuperior.

简介：Tandemgasmetalarcwelding(T-GMAW)processshowsahighdepositionratethatuptothreetimesofthesingleelectrodeGMAW,sotheweldingspeedcouldbesignificantlyincreasedinthisprocess.However,themajorityofthisprocessapplicationsarebasedonthepre-programmedroboticwelding,whichdoesnotallowthemtotracktheseamreal-timeduringwelding.Rotatingarcsensor,sensingtheseampositionbydetectingthechangingofweldingcurrents,hasbeenwidelyadoptedintheautomaticrobotweldingprocess.Itisproposedinthispapertointegratetherotatingarcsensorwithatrailingtorchtodevelopanewapproachofrotatingarcleadtandemgasmetalarcwelding(RLT-GMAW)process.Thecharacteristicsoftheweldingcurrentsintheproposednewweldingprocesswerefirstlystudied,andthenaself-turningfuzzycontrolseamtrackingstrategywasdevelopedforthemobilerobotautomaticwelding.TheexperimentalresultsshowedthattheproposedRLT-GMAWprocesshadanexcellentseamtrackingperformanceandhighweldingdepositionrate.Evenifthereweresomeelectromagneticinteractionsbetweenthetwoarcs,thedeviationoftheweldingseamcouldalsobereflectedbythefluctuationoftheweldingcurrentsontheleadingarconcethecorrectweldingparameterswereselected.Basedonthedetecteddeviation,theweldingtrackingexperimentsshowedthattheproposedself-turningfuzzycontrollerhadagoodperformancefortheRLT-GMAWprocessseamtracking.

简介：

简介：Inthisstudy,atwo-stepheatingprocessisintroducedfortransientliquidphase(TLP)diffusionbondingforsoundjointswithT91heatresistantsteels.Atfirst,ashort-timehighertemperatureheatingstepisaddressedtomelttheinterlayer,followedbythesecondsteptocompleteisothermalsolidificationatalowtemperature.Themostcriticalfeatureofournewmethodisproducinganon-planarinterfaceattheT91heatresistantsteelsjoint.WeproposeatransitionalliquidphasebondingofT91heatresistantsteelsbythisapproach.Sincejointmicrostructureshavebeenstudied,wetestedthetensilestrengthtoassessjointmechanicalproperty.Theresultindicatesthatthesolidifiedbondmaycontainaprimarysolid-solution,similarcompositiontotheparentmetalandfreefromprecipitates.Jointtensilestrengthofthejointisnotlowerthanparentmaterials.Jointbend'sstrengthsareenhancedduetothehighermetal-to-metaljunctionproducinganon-planarbondlines.Nevertheless,thetraditionaltransientliquidphasediffusionbondingproducesplanarones.Bondingparametersofnewprocessare1260℃for0.5minand1230℃for4min.

简介：间歇生产过程具有弹性大、灵活等特点,其市场适应性较强。化工生产中间歇生产过程占相当比例,文章就间歇生产工艺的模拟与优化进行介绍,利用AspenBatchProcessDeveloper模拟间歇工艺过程,可以快速地得到工艺流程的物料衡算、热量衡算、操作时间、公用工程和成本估算等结果。同时,还可以对模拟结果进行分析,找出制约生产工艺的瓶颈,并对生产周期、生产规模、生产设备等进行优化,提高工艺设计效率,降低生产成本。

简介：

简介：Nb-Ti-Si-based合金粉末被元素的粒子的机械alloying(麻省)准备。形态学，尺寸，阶段成分，雏晶尺寸，格子紧张，作文和内部微观结构的进化，等等，合金，粉末被X光检查衍射(XRD)分析，扫描电子显微镜学(SEM)，精力散的光谱学(版本)，激光粒子尺寸分析器和传播电子显微镜(TEM)分析。合金粒子逐渐地被精制，他们的形状随milling时间的增加变得球状。Nb稳固的答案(Nbss)的衍射山峰分阶段执行移动向从2～5在球milling期间降低2个角度?h，并且在那Nbss衍射以后，山峰变向更高，有milling的增加的2个角度从5～70预定?h，它主要由于alloying元素原子的溶液被归因于Nbss粉末的格子参数的改变进Nb格子形成Nbss。在球milling过程期间，在雏晶尺寸的减少和粉末导致他们的衍射的连续拓宽的Nbss的格子紧张的增加达到顶点。典型薄片状的微观结构为5在球milling以后在粉末粒子内被形成?h并且变得更多随milling时间的增加精制了并且一致。在40-h-ballmilling以后，典型薄片状的微观结构消失并且很同类的微观结构相反被形成。这同类的微观结构被证明由仅仅使过饱和的Nbss阶段构成。

简介：

简介：Inordertotheoreticallystudythebucklepropagationofsubseapipelineswithslip-onbucklearrestors,atwo-dimensionalringmodelwassetuptorepresentthepipelineandanonlinearspringmodelwasadoptedtosimulatethecontactbetweenpipeline’sinnerwallsandbetweenpipeline’souterwallandslip-onbucklearrestor’sinnerwallduringbucklepropagation.Inaddition,somereversespringsareaddedtopreventthewallofleftandrightsidesseparatingfromtheinnerwallofslip-onbucklearrestors.Consideringlargedeformationkinematicsrelationsandtheelastic-plasticconstitutiverelationofmaterial,balanceequationswereestablishedwiththeprincipleofvirtualwork.Thevariationofexternalpressurewithrespecttothecross-sectionalareaofpipelineswasanalyzed,andthelowerboundofthecrossoverpressureofslip-onbucklearrestorswascalculatedbasedonMaxwell’senergybalancemethod.Bycomparingthetheoreticalresultswithexperimentandfiniteelementnumericalsimulation,thetheoreticalmethodisprovedtobecorrectandreliable.