简介:WeldingresearchofA6N01S-T5aluminumalloyprofileforhigh-speedtrainwasdonebyusinglaser-MIGhybridweldingandMIGweldingindividually.Andtheweldappearance,weldingdistortion,mechanicalpropertiesofthejointsandmicrostructureswereanalyzed.Thetestresultsdemonstratedthathigh-efficientweldingfortheprofilecanbeachievedbyusinglaser-MIGhybridwelding,thespeedofwhichcanbeover3.0m/min.Theprocessinghadagoodgapbridgingability,evenifthegapofthebuttjointwasupto2.0mm,agoodweldappearancecanalsobegot.Whilethehybridweldingspeedwasgreaterthan2.5m/min,theweldingdistortionofthelaser-tandemMIGhybridjointswasjustabout33%ofthatoftheMIGjoints,buttheweldingefficiencywasover3timesofMIGwelding.Andtensilestrengthofthehybridjointswas85%ofthatofA6N01S-T5basemetal,9%higherthanthatoftheMIGjoints.Fatiguepropertieswastestedindividuallywithpulsedtensilefatiguemethodintheconditionof1×107lifetime.Thetestresultsdemonstratedthatthefatiguestrengthofthejointswasalittlelowerthanthatofbasematerial,whichcouldbeupto115MPa.Butthefatiguestrengthofhybridweldingjointswas107.5MPa,whichwas23%higherthan87MPaofMIGweldingjoints.
简介:FlameheatingcombinedwithwatercoolingwasusedtostraightenA6N01aluminumalloyweldedjointandeffectofflameheatingpassonitsmicrostructureandmechanicalpropertieswasstudied.ResultsshowedthattheflameinducedtheprecipitationandgrowthoftheMg2SiphaseontheAlsubstrateforthethermalagingA6N01aluminumalloyweldedjoints,thusitledthedecreaseofmicro-hardnessandtensilestrengthoftheA6N01aluminumalloyweldedjointwiththeincreaseoftheheatingpass.However,thefatiguepropertyoftheflameheatedjointwasimprovedbecausetheMg2Siprecipitationhinderedtheinitiationandpropagationofthefatiguecrack.
简介:BeijinghasbeenoneoftheepicentersattackedmostseverelybytheSARS-CoV(severeacuterespiratorysyndrome-associatedcoronavirus)sincethefirstpatientwasdiagnosedinoneofthecity'shospitals.WenowreportcompletegenomesequencesoftheBJGroup,includingfourisolates(IsolatesBJ01,BJ02,BJ03,andBJ04)oftheSARS-CoV.ItisremarkablethatallmembersoftheBJGroupshareacommonhaplotype,consistingofsevenlocithatdifferentiatethegroupfromotherisolatespublishedtodate.Among42substitutionsuniquelyidentifledfromtheBJgroup,32arenon-synonymouschangesattheaminoacidlevel.Rootedphylogenetictrees,proposedonthebasisofhaplotypesandothersequencevariationsofSARS-CoVisolatesfromCanada,USA,Singapore,andChina,gaverisetodifferentparadigmsbutpositionedtheBJGroup,togetherwiththenewlydiscoveredGD01(GD-Ins29)inthesameclade,followedbytheH-UGroup(fromHongKongtoUSA)andtheH-TGroup(fromHongKongtoToronto),leavingtheSPGroup(Singapore)moredistant.ThisresultappearstosuggestapossibletransmissionpathfromGuangdongtoBeijing/HongKong,thentoothercountriesandregions.
简介:《公路工程技术标准》(JTGB01-2014)(下称2014版标准)自2015年1月1日颁布实施,该版标准结合我国公路交通事业发展的现状和趋势,在强调交通安全、保护环境、节约资源的前提下,突出公路及其设施的功能在确定技术标准和指标中的主导作用;增加了公路改扩建、运行速度、非机动车和行人密集路段、安全性评价、救灾通道等方面的规定和要求;补充了干线公路交通工程、乡村公路交叉等方面的规定;调整了公路适应交通量、车辆折算系数、交通量预测年限、服务水平等级、路基横断面宽度、纵坡、桥梁减宽、隧道横断面及进出口线形、交通工程分类等方面的规定.