A series of wear and flame resistant polyamide 6(PA6)composites were prepared using glass fiber(GF)and talc(T)as reinforcer,polytetrafluoroethylene(PTFE)and graphite(Gr)as solid lubricants,red phosphorus(RP)and zinc b...A series of wear and flame resistant polyamide 6(PA6)composites were prepared using glass fiber(GF)and talc(T)as reinforcer,polytetrafluoroethylene(PTFE)and graphite(Gr)as solid lubricants,red phosphorus(RP)and zinc borate(ZB)as flame retardant.The tribological property,mechanical property,flame retardant property and the flame retardant mechanism were investigated.The tests show that the formula of the wear resistant PA6 composite(WRPA 6)is PA6/GF/T/PTFE/Gr in the ratio of 100/15/5/10/5 by mass.Because this composite exhibits the lowest friction coefficient(0.1429)and no wear mass loss,the introduction of RP and ZB can increase the flame resistance of WRPA6,and the synergistic effect of RP and ZB is obtained.Detailedly,the composite with 4 parts of ZB and 12 parts of RP shows the best flame retardant property,achieving the highest limiting oxygen index(LOI)(30.2 vol%)and a UL94 V-0 rating,and the flame retardant mechanisms may be gas phase along with condense phase mechanism.展开更多
Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height(PBLH)over Guangzhou from September 2013 to November 2014 over Guangzhou.Impact of the boundary effect and the wavelet ...Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height(PBLH)over Guangzhou from September 2013 to November 2014 over Guangzhou.Impact of the boundary effect and the wavelet scale factor on the accuracy of the retrieved PBLH has been explored thoroughly.In addition,the PBLH diurnal variations and the relationship between PM_(2.5) concentration and PBLH during polluted and clean episodes were studied.Results indicate that the most steady retrieved PBLH can be obtained when scale factor is chosen between 300-390 m.The retrieved maximum and minimum PBLH in the annual mean diurnal cycle were~1100 m and~650 m,respectively.The PBLH was significantly lower in the dry season than in the wet season,with the average highest PBLH in the dry season and the wet season being~1050 m and~1200 m respectively.Compared to the wet season,the development of PBLH in the dry season was delayed by at least one hour due to the seasonal cycle of solar radiation.Episode analysis indicated that the PBLH was~50%higher during clean episodes than during haze episodes.The average highest PBLH in the haze episodes and clean episodes were~800 m and~1300 m,respectively.A significant negative correlation between PBLH and PM_(2.5) concentration(r=-0.55**)is discovered.According to China"Ambient Air Quality Standard",the PBLH values in good and slightly polluted conditions were 1/6-1/3 lower than that in excellent conditions,while the corresponding PM_(2.5) concentration were~2-2.5 times higher.展开更多
基金Project(149929)supported by the Postdoctoral Fund of Central South University,ChinaProject(16C0292)supported by the Hunan Education Department,ChinaProject(2016TP1022)supported by the Hunan Provincial Key Lab of Dark Tea and Jin-hua,China
文摘A series of wear and flame resistant polyamide 6(PA6)composites were prepared using glass fiber(GF)and talc(T)as reinforcer,polytetrafluoroethylene(PTFE)and graphite(Gr)as solid lubricants,red phosphorus(RP)and zinc borate(ZB)as flame retardant.The tribological property,mechanical property,flame retardant property and the flame retardant mechanism were investigated.The tests show that the formula of the wear resistant PA6 composite(WRPA 6)is PA6/GF/T/PTFE/Gr in the ratio of 100/15/5/10/5 by mass.Because this composite exhibits the lowest friction coefficient(0.1429)and no wear mass loss,the introduction of RP and ZB can increase the flame resistance of WRPA6,and the synergistic effect of RP and ZB is obtained.Detailedly,the composite with 4 parts of ZB and 12 parts of RP shows the best flame retardant property,achieving the highest limiting oxygen index(LOI)(30.2 vol%)and a UL94 V-0 rating,and the flame retardant mechanisms may be gas phase along with condense phase mechanism.
基金National Key R&D Program of China(2019YFC0214605,2018YFC0213901)National Natural Science Foundation of China(41775037)+1 种基金Guangdong Provincial Key R&D Program(2020B1111360003)Scientific and Technological Innovation Team Project of Guangdong Meteorological Service(GRMCTD202003)。
文摘Wavelet analysis was applied to lidar observations to retrieve the planetary boundary layer height(PBLH)over Guangzhou from September 2013 to November 2014 over Guangzhou.Impact of the boundary effect and the wavelet scale factor on the accuracy of the retrieved PBLH has been explored thoroughly.In addition,the PBLH diurnal variations and the relationship between PM_(2.5) concentration and PBLH during polluted and clean episodes were studied.Results indicate that the most steady retrieved PBLH can be obtained when scale factor is chosen between 300-390 m.The retrieved maximum and minimum PBLH in the annual mean diurnal cycle were~1100 m and~650 m,respectively.The PBLH was significantly lower in the dry season than in the wet season,with the average highest PBLH in the dry season and the wet season being~1050 m and~1200 m respectively.Compared to the wet season,the development of PBLH in the dry season was delayed by at least one hour due to the seasonal cycle of solar radiation.Episode analysis indicated that the PBLH was~50%higher during clean episodes than during haze episodes.The average highest PBLH in the haze episodes and clean episodes were~800 m and~1300 m,respectively.A significant negative correlation between PBLH and PM_(2.5) concentration(r=-0.55**)is discovered.According to China"Ambient Air Quality Standard",the PBLH values in good and slightly polluted conditions were 1/6-1/3 lower than that in excellent conditions,while the corresponding PM_(2.5) concentration were~2-2.5 times higher.
