简介:AnewkindofsimpleandflexibleCO_2weldingsystemwasdevelopedtocarryoutwaveformcontrol.ThesystemconsistedofIGBTinverter,PWMcircuitandmicroprocessorunit(MPU),inwhichtheoutputcurrentofconstantcurrent(CC)powersupplycouldbechangedaccordingtotransientphysicalstate,andthevariabledownsloperatecontrolcouldbeusedtoensureastableweldingprocess.Theweldingexperimentresultsprovedtheeffectivenessofthiscontrolapproach.
简介:Accuratelymeasuringthedifferentialmolecularabsorptioncrosssectionisthekeytoobtainingahigh-precisionconcentrationofatmospherictracegasesinadifferentialabsorptionlidar(DIAL)system.However,theCO2absorptionlineismeticulousat1.6μm,easilytranslatingandbroadeningbecauseofthechangeoftemperatureandpressure.Hence,measuringtheverticalprofileofatmospherictemperatureandpressuretocalculatetheverticalprofileoftheCO2weightparameterisnecessary.Ingeneral,measuringatmospherictemperatureandpressurehasacertainamountofuncertainty.Therefore,thisstudyproposestheconceptofabalancedon-linewavelength,wherethedifferentialmolecularabsorptioncrosssectionislargerandtheCO2weightparameterisinsensitivetotheuncertaintyofatmospherictemperatureandpressure.Inthisstudy,weanalyzedtheinfluenceofuncertaintyontheCO2weightparameterateverypreselectedwavelength,aswellasdeterminedanappropriatewavelengthnearoneoftheabsorptionpeaks.Ourresultshowsthat1572.023nmshouldbeoneoftheappropriatebalancedonlinewavelengths.ThemeasurementerrorsofthemixingratioofCO2moleculeinthiswavelengthareonly0.23%and0.25%andarecausedby1Ktemperatureerrorand1hPapressureerror,respectively.Thisachievementofabalancedon-linewavelengthwillnotonlydepresstherequirementofthelaser’sfrequencystabilizationbutalsothedemandformeasurementprecisionoftheatmospherictemperatureandpressureprofile.Furthermore,thisstudycanachievetheexactmeasurementoftheverticalprofileofatmosphericCO2basedonanindependentdifferentialabsorptionlaser.
简介:摘要:本文简单地叙述了二氧化碳气体保护焊(以下简称CO2焊)时气孔产生的原因、防止措施和气孔的种类及气孔的危害,对上焊接加工实训课有着重要的指导作用,能有效提高实训课教学质量。
简介:摘要:制冷剂替代的一个研究方向是使用天然工质,而CO2是常用的天然工质之一。本文首先介绍制冷剂的相关物理性质和热力学性质特点,说明CO2作为制冷剂的优越性。然后结合CO2跨临界循环系统介绍结构元器件选型和特点,重点讲述系统非标结构件管路件的选用参考。最后,介绍CO2制冷系统发展过程中面临的挑战和今后发展趋势。
简介:依据红外分光计(InfraRedAtmosphericSounder,IRAS)光谱通道特征,发展了基于IRAS的大气辐射传输计算模式。以大气分子吸收光谱数据集(HighresolutionTRANsmission,HITRAN)2004为初始谱线输入资料,利用该模式模拟计算IRAS在CO2吸收带的10个通道辐射率测值对CO2浓度变化的响应,并对比了其与大气温度和水汽、O3等气体浓度误差对辐射率测值的影响,探讨了利用风云三号气象卫星探测大气CO2浓度的可行性。结果表明,IRAS的通道4最适于用来监测大气CO2浓度的变化,当CO2体积混合比浓度变化在10×10^-6时,对应的辐射率变化同仪器等效噪声辐射率相当,所以IRAS在理想状态下,最高可分辨的大气CO2浓度变化约为10×10^-6。