简介:TheMOCVDgrowthofmodifiedAlAs/GaAsdoublebarrierresonanttunnelingdiodes(DBRTD)withanA1GaAschairwasreported.Theresonancestothefirstexcitedstateswereobtained.Thepeak-to-valleycur-rentratio(PVCR)is1.3at77K,roomtemperaturepeakcurrentdensityis8kA/cm~2.Theresonancevoltagesareinagreementwiththetheoreticalapproachbytransfer-matrixmethod.Influenceofinterruptedgrowthtimeatthehetero-interfaceandincorporationoftheAlGaAschairtothedeviceperformanceswerestudiedandthemechanismwasdiscussed.TheattempttoaddanAlGaAschairtotheDBRTDbyMOCVDresultedinimprovementinthePVCRandpeakcurrentdensity.
简介:Bead-on-plateCO2laserweldingof1000MPagradetransformationinducedplasticity(TRIP)steelwasconductedunderdifferentweldingpowers,weldingspeedsandshieldgases.Themacrostructuralandmicrostructuralfeaturesoftheweldedjointwereinvestigated.Theincreaseofweldingspeedreducedthewidthoftheweldbeadandtheporositiesintheweldbeadresultingfromthedifferentflowmodeofmeltedmetalinweldpool.ThedecreaseofweldingpoweroruseofshieldgasofheliumalsocontributedtothereductionofporosityinBead-on-plateCO2laserweldingof1000MPagradetransformationinducedplasticity(TRIP)steelwasconductedunderdifferentweldingpowers,weldingspeedsandshieldgases.Themacrostructuralandmicrostructuralfeaturesoftheweldedjointwereinvestigated.Theincreaseofweldingspeedreducedthewidthoftheweldbeadandtheporositiesintheweldbeadresultingfromthedifferentflowmodeofmeltedmetalinweldpool.Thedecreaseofweldingpoweroruseofshieldgasofheliumalsocontributedtothereductionofporosityintheweldbeadduetothealleviationofinducedplasmaformation,thusstabilizingthekeyhole.TheporosityformationintimatelycorrelatedwiththeevaporationofalloyelementMninthebasemetal.Thelaserweldedmetalhadsamemartensitemicrostructureasthatofwater-quenchedbasemetal.Theweldingparameterswhichincreasedcoolingrateallledtofinemicrostructuresoftheweldbead.
简介:基于SolidWorks软件平台开发了一套挤压模CAD系统,该系统将专家知识和设计经验存储于模具结构和零件模型中,通过选用不同模具组件的结构形状,达到了挤压模的优化设计。同时也保证了设计质量,加快了设计速度。