简介：Theprocessesreportedforthepreparationoflanthanumhexaboride(LaB6)fromlanthanumoxideinvolvetheuseofcarboneitherelementalorintheformofboroncarbideorelementalboronitselfasreducingagents,fusedsaltsathightemperaturesorreactionswhichrequiretheproductboridetobeleachedout.Eachofthesetechniqueseitherincreasestheprocesscostsand/orincreaseschancesofcontaminationinfi-nalproduct.PureLaB6canbestbepreparedbyareactionwhichproducesagaseousbyprodu...

简介：Theinfraredcameraisusedtoinvestigatethetemperaturefieldofgasmetalarcwelding.Theresultsshowthatthetemperaturedistributionofweldpoolandadjacentareaappearsconeshape.AnewheatsourcemodelcombinedbyGaussiandistributionheatsourceofthearcandconicaldistributionheatsourceofthedropletissetupbasedontheexperimentalresults,andwiththecombinedboundaryconditions,thetemperaturefieldofgasmetalarcweldingissimulatedusingfiniteelementmethod.AccordingtothecomparisonbetweentheresultsofexperimentandsimulationintemperaturefieldshowsthatthenewcombinedheatsourcemodelismoreaccurateandeffectivethantheGaussheatsourcemodel.

简介：ThereareabundantnaturalgasresourcesinwesternChina,butmanyoilandgasfieldsarerichinchloridion,sulfuretedhydrogen,carbondioxideandothercorrosivemedium,whichhavestrongcorrosivitytopipeline.Onegasfieldpossessesabundantnaturalgaswithgreatpressure,andthechloridionconcentrationinthewaterseparatedfromgasisabout10%,sothemediumhasgreatcorrosivity.Inordertoensurethesafetyofthepipeline,about13kmlengthpipelineandtheinternalpipesofagastreatmentplantthatpurifiesgasabout12billioncubicmeterayeararemadeof2205duplexstainlesssteel(2205DSS).2205DSShasmanycharacteristicsinweldingwithcomplexweldingprocess;andbecauseofhighqualityrequirementsfortheconstructionofnaturalgaspipelineandrestrictionofon-siteconditions,thesiteweldingisverydifficult.Aroundtheengineeringapplication,alargenumberofexperimentalresearcheshavebeencarriedoutonthematerialmicrostructure,propertiesandweldability.Finallyweldedjointswhichconformtotherequirementsofstandardareobtained,contributingtothefirstlarge-scaleapplicationofthismaterialinthefieldofoilandgaspipelines.Consideringtheengineeringapplicationandthelatestresearchdevelopment,theweldingandkeyfactorsaffectingthejointpropertiesof2205DSSpipesaresummarizedandanalyzed.

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简介：SYSWELDwasusedtosimulatein-serviceweldingprocessofgaspipelineofX70pipelinesteel.Weldingthermalcycle,stressanddeformationofin-serviceweldedjointwerestudied.Theresultsshowthatpeaktemperatureofcoarsegrainheat-affectedzone(CGHAZ)ofin-serviceweldingontogaspipelineisthesamewithroutinewelding,butt_(8/5),t_(8/5)andt_(8/1)decreaseatcertaindegree.Forthezonenearweldedseam,axialstressandhoopstressintheinnerpipewallarecompressivestresswhenweldingsourcepassesthroughthecross-sectionthatisstudied,butresidualaxialstressandresidualhoopstressafterweldedarealltensilestress.Transientdeformationandresidualdeformationareallconvexdeformationcomparedwiththeoriginalpipediametersize.Deformationachievesmaximumwhenweldingthermalsourcepassesthroughthecross-sectionthatisstudiedandthendecreasesduringthecoolingprocessafterwelding.

简介：Theetchingeffectofammonia(NH3)onthegrowthofverticallyalignednanotubes/nanofibers(CNTs)wasinvestigatedbydirect-currentplasmaenhancedchemicalvapordeposition(DC-PECVD).NH3gasetchesNicatalystlayertoformnanoscaleislandswhileNH3plasmaetchesthedepositedamorphouscarbon.BasedontheetchingeffectofNH3gasonNicatalyst,thedifferencesofgrowingbundlesofCNTsandsinglestrandCNTswerediscussed;specifically,theamountofoptimalNH3gasetchingisdifferentbetweenbundlesofCNTsandsinglestrandCNTs.IncontrasttotheCNTcarpetgrowth,thesinglestrandCNTgrowthrequiresshorteretchingtime(5min)thanlargecatalyticpatterns(10min)sincenanodotsalreadyformcatalystislandsforCNTgrowth.Throughremovingtheplasmapretreatmentprocess,thedamagefrombeingexposedathightemperaturesubstrateoccurringduringtheplasmagenerationtimeisminimized.Highresolutiontransmissionelectronmicroscopy(HTEM)showsfishbonestructureofCNTsgrownbyPECVD.

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简介：OnthebasisOftheYoung-LaplaceEquationthatdescribesthepressuredifferencebetweeneachsideofacurvedliquidsurface,astaticequilibriummodelisestablishedtodescribethesurfaceshapeoftheweldbead.Thegeo-metricalmodelforthemoltenpoolisincluded,whichisessentialtoexplaintheundercutphenomenonduringhighspeedbead-on-platewelding.Theresultsgotfromaniterationalgorithmshowthatitistheforcebalanceontheliquidmixtureofthedepositedmetalandthedepositedmetalandthemoltenbasemetalandthemoltenbasemetalthatcausestheundercut.Somefactorsandtheireffectsarealsoana-lyzed.

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简介：Asensingsystemisdevelopedtomeasuretheweldpoolboundaryandpoolsurfacedeformationingastungstenarcwelding.LaserStrobetechniqueisusedtoeliminatethestrongarclightinterference,andspecularreflectionfromthepoolsurfaceissensedtodescribetherelationbetweenthedeformedstripesandpoolsurfacedepression.Clearimagesofboththepoolboundaryandthedeformedstripesedgesareobtainedduringgastungstenarcweldingprocess,whichlaysfoundationforreal-timemonitoringthepoolsurfacedepressionandweldpenetration.

简介：UsingXenonlamplightstoovercomethestronginterferencefromtheweldingarc,acomputer-basedsystemisdevelopedtosenseandvisualizethemetaltransferinGMAW.Thissystemcombinesthrough-the-arcsensingoftheweldingcurrentandarcvoltagewithhighspeedimagingofthemetaltransfer.Itcansimultaneouslydisplaythemetaltransferprocessesandwaveformsofelectricalweldingparametersinreal-timeThemetaltransfervideosandwaveformsofelectricalweldingparameterscanberecorded.Metaltransfersundervariousweldingconditionshavebeeninvestigatedwiththesystemdeveloped.

简介：ThesoftwareofSYSWELDwasusedtobuildmodelandsimulatethermalcycleofin-serviceweldingontoactivegaspipeline.Influenceofpipediameter,wallthicknessandheatinputonthermalcyclewasstudied.Theresultsshowthatt8/5,t8/3andpeaktemperatureofinnersurfacedecreasewhenwallthicknessincreasesfrom5mmto12mm.Butt8/1willincreaseswiththeincreaseofwallthicknessandwilldecreaseafterthewallthicknessislargerthan7mm.Pipediameterhaslittleinfluenceonthermalcycleandthatinfluencecanbeignoredwhenpipediameterisgreaterthan273mm.t8/5,t8/3,t8/1andpeaktemperatureofinnersurfacewillincreasewiththeincreaseofheatinput.

简介：Adigitalcontrolofpulsedgasmetalarcweldinginverterwasproposed.AcontrolsystemconsistingofanaloguepartswasreplacedwithanewdigitalcontrolimplementedinaTMS320LF2407ADSPchip.Thedesignandconstructionalfeaturesofthewholedigitalcontrolwerepresented.TheresourcesoftheDSPchipwereefficientlyutilizedandthecircuitsareveryconcise,whichcanenhancethestabilityandreliabilityofweldinginverter.Experimentalresultsdemonstratethatthedevelopeddigitalcontrolhastheabilitytoaccomplishtheexcellentpulsedgasmetalarcweldingprocessandthemeritsofthedevelopeddigitalcontrolarestableweldingprocess,littlespatterandperfectweldappearance.

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简介：Theexperimentaltimeseriesofweldingcurrentproducedbycarbondioxidegasmetalarcweldingwithshort-circuitingtransferwererecordedandsubsequentlyevaluated.Basedonphasespacereconstruction,thecorrelationdimensionsandKolmogoroventropiesofthecorrespondingsystemhavebeennumericallycalculatedusingtheGrassberger-Procacciaalgorithmatdifferenttimedelays.Itwasfoundoutthatthetimedelayhaslittleeffectontheestimationofcorrelationdimension;conversely,itplaysakeyroleinproducingpreciseresultsontheestimationofKolmogoroventropy.

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