为了研究冷金属与脉冲复合焊(cold metal transfer and pulse,CMT+P)的焊接行为,使用PCI数据采集卡、高速相机、红外成像仪及声发射采集系统对焊接过程进行同步监测.发现脉冲射滴过渡发生前,焊机输出电流突增,同时焊丝尖端释放猛烈电弧...为了研究冷金属与脉冲复合焊(cold metal transfer and pulse,CMT+P)的焊接行为,使用PCI数据采集卡、高速相机、红外成像仪及声发射采集系统对焊接过程进行同步监测.发现脉冲射滴过渡发生前,焊机输出电流突增,同时焊丝尖端释放猛烈电弧光,随后熔滴滴入焊道,熔池温度增加,声发射(acoustic emission,AE)信号显示出1个波峰.发生CMT短路过渡时,焊机输出电流同时为焊丝熔化和焊丝伸出提供能量,待到焊丝尖端接触基板瞬间形成短路,熔池温度持续降低,AE信号微弱,伴随着熔滴因过热收缩而爆断,熔滴短路过渡完成.对AE信号进行离散傅里叶变换(discrete Fourier transform,DFT)后,可通过特征频率对CMT+P各个周期及阶段进行过程识别.结果表明,575 kHz和415 kHz可作为脉冲电弧周期和CMT短路周期的特征频率,推断180 kHz是脉冲电弧的特有频率,575 kHz的频率则是基础电弧提供,415 kHz处的频率则在CMT短路接触瞬间产生.展开更多
Background:Naturally-colored cotton has become increasingly popular because of their natural properties of coloration,UV protection,flame retardant,antibacterial activity and mildew resistance.But poor fiber quality a...Background:Naturally-colored cotton has become increasingly popular because of their natural properties of coloration,UV protection,flame retardant,antibacterial activity and mildew resistance.But poor fiber quality and limited color choices are two key issues that have restricted the cultivation of naturally-colored cotton.To identify the possible pathways participating in fiber pigmentation in naturally-colored cottons,five colored cotton accessions in three different color types(with green,brown and white fiber)were chosen for a comprehensive analysis of phenylpropanoid metabolism during fiber development.Results:The expression levels of flavonoid biosynthesis pathway genes in brown cotton fibers were significantly higher than those in white and green cotton fibers.Total flavonoids and proanthocyanidin were higher in brown cotton fibers relative to those in white and green cotton fibers,which suggested that the flavonoid biosynthesis pathway might not participate in the pigmentation of green cotton fibers.Further expression analysis indicated that the genes encoding enzymes for the synthesis of caffeic acid derivatives,lignin and lignan were activated in the developing fibers of the green cotton at 10 and 15 days post-anthesis.Conclusions:Our results strengthen the understanding of phenylpropanoid metabolism and pigmentation in green and brown cotton fibers,and may improve the breeding of naturally-colored cottons.展开更多
文摘为了研究冷金属与脉冲复合焊(cold metal transfer and pulse,CMT+P)的焊接行为,使用PCI数据采集卡、高速相机、红外成像仪及声发射采集系统对焊接过程进行同步监测.发现脉冲射滴过渡发生前,焊机输出电流突增,同时焊丝尖端释放猛烈电弧光,随后熔滴滴入焊道,熔池温度增加,声发射(acoustic emission,AE)信号显示出1个波峰.发生CMT短路过渡时,焊机输出电流同时为焊丝熔化和焊丝伸出提供能量,待到焊丝尖端接触基板瞬间形成短路,熔池温度持续降低,AE信号微弱,伴随着熔滴因过热收缩而爆断,熔滴短路过渡完成.对AE信号进行离散傅里叶变换(discrete Fourier transform,DFT)后,可通过特征频率对CMT+P各个周期及阶段进行过程识别.结果表明,575 kHz和415 kHz可作为脉冲电弧周期和CMT短路周期的特征频率,推断180 kHz是脉冲电弧的特有频率,575 kHz的频率则是基础电弧提供,415 kHz处的频率则在CMT短路接触瞬间产生.
基金This work was financially supported by the National Natural Science Foundation of China(31471540)National Transgenic Plant Research of China(2016ZX08005–001)to Zhang XL+3 种基金This project was also supported by the Fundamental Research Funds for the Central Universities(2662017JC030)Funding was also provided by Science and Technology Innovation Talent program(2020CB017)Scientific and Technological Breakthrough and Achievement Transformation Projects of Xinjiang Production and Construction Corps(2016 AC027)Scientific Research Project of Shihezi(2016HZ09)to You CY.
文摘Background:Naturally-colored cotton has become increasingly popular because of their natural properties of coloration,UV protection,flame retardant,antibacterial activity and mildew resistance.But poor fiber quality and limited color choices are two key issues that have restricted the cultivation of naturally-colored cotton.To identify the possible pathways participating in fiber pigmentation in naturally-colored cottons,five colored cotton accessions in three different color types(with green,brown and white fiber)were chosen for a comprehensive analysis of phenylpropanoid metabolism during fiber development.Results:The expression levels of flavonoid biosynthesis pathway genes in brown cotton fibers were significantly higher than those in white and green cotton fibers.Total flavonoids and proanthocyanidin were higher in brown cotton fibers relative to those in white and green cotton fibers,which suggested that the flavonoid biosynthesis pathway might not participate in the pigmentation of green cotton fibers.Further expression analysis indicated that the genes encoding enzymes for the synthesis of caffeic acid derivatives,lignin and lignan were activated in the developing fibers of the green cotton at 10 and 15 days post-anthesis.Conclusions:Our results strengthen the understanding of phenylpropanoid metabolism and pigmentation in green and brown cotton fibers,and may improve the breeding of naturally-colored cottons.
