During deep penetration laser welding,there exist plume（weak plasma） and spatters,which are the results of weld material ejection due to strong laser heating.The characteristics of plume and spatters are related to ...During deep penetration laser welding,there exist plume（weak plasma） and spatters,which are the results of weld material ejection due to strong laser heating.The characteristics of plume and spatters are related to welding stability and quality.Characteristics of metallic plume and spatters were investigated during high-power disk laser bead-on-plate welding of Type 304 austenitic stainless steel plates at a continuous wave laser power of 10 kW.An ultraviolet and visible sensitive high-speed camera was used to capture the metallic plume and spatter images.Plume area,laser beam path through the plume,swing angle,distance between laser beam focus and plume image centroid,abscissa of plume centroid and spatter numbers are defined as eigenvalues,and the weld bead width was used as a characteristic parameter that reflected welding stability.Welding status was distinguished by SVM（support vector machine） after data normalization and characteristic analysis.Also,PCA（principal components analysis） feature extraction was used to reduce the dimensions of feature space,and PSO（particle swarm optimization） was used to optimize the parameters of SVM.Finally a classification model based on SVM was established to estimate the weld bead width and welding stability.Experimental results show that the established algorithm based on SVM could effectively distinguish the variation of weld bead width,thus providing an experimental example of monitoring high-power disk laser welding quality.展开更多
A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels i...A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels in water. A 100 mL water sample was adjusted to pH 5.6 with nitric acid and a 1 mol?L–1 ammonium acetate solution, and then passed through an IED (diameter, 47 mm;effective filtering diameter, 35 mm) at a flow rate of 80 - 100 mL?min–1 to preconcentrate seven analytes. The IED was dried at 100?C for 20 min in an electric oven, and 110 - 145 small disks, each 2 mm in diameter, were punched out from the IED. A small disk was introduced into the graphite furnace and atomized according to a heating program. For Cd, Sn, Pb, and Bi measurements, Pd was used as a chemical modifier to enhance the absorbances. Calibration was performed using aqueous standard solutions. The detection limits, corresponding to three times the standard deviation (n = 5) of the blank values, were 0.092 μg·L–1 for Co, 0.12 μg·L–1 for Ni, 0.40 μg·L–1 for Cu, 0.077 μg·L–1 for Cd, 0.92 μg·L–1 for Sn, 0.61 μg·L–1 for Pb, and 0.80 μg·L–1 for Bi with an enrichment factor of 140 using a 100-mL water sample. A spike test for the seven analytes in tap water, rainwater, river water, and mineral drinking water showed quantitative recoveries (93% - 108%).展开更多
Metal derivative/graphitic carbon nitride(g-C_(3)N_(4))association is found promising in providing sustainable hydrogen production by photocatalytic water splitting process.Number of works reported on the synthesis an...Metal derivative/graphitic carbon nitride(g-C_(3)N_(4))association is found promising in providing sustainable hydrogen production by photocatalytic water splitting process.Number of works reported on the synthesis and application of various metal based g-C_(3)N_(4)composites are increasing day by day.Mechanism of charge separation varies according to the metal candidate that gets couple with g-C_(3)N_(4).The present article thus explores the interesting chemistry behind various metal based heterojunction and demonstrates the charge separation route.A thorough investigation has been done on the current research trend in the area.As many metal free g-C_(3)N_(4)composites are reported nowadays as an alternative to metal derivatives,here compares metallic and metal free derivatives of g-C_(3)N_(4)based on four critical requirements of an industrial catalyst,ie,activity,stability,cost and toxicity.Challenges and future direction in the area are also discussed with significance.The systematic discussion and schematic illustration of charge transfer process in different heterojunctions with reference to the reported systems,given in the article can definitely contribute to the design and development of more efficient g-C_(3)N_(4)based heterojunctions in future for hydrogen production application.展开更多
The complexes of biogenic metals (Zn2+,Cu2+,Co2+,Mn3+,Fe3+) based on meso-tetra(3,5-diisobor- nyl-4-hydroxyphenyl)porphyrin 1 were synthesized. The electrochemical behavior of these com-pounds was studied using cyclic...The complexes of biogenic metals (Zn2+,Cu2+,Co2+,Mn3+,Fe3+) based on meso-tetra(3,5-diisobor- nyl-4-hydroxyphenyl)porphyrin 1 were synthesized. The electrochemical behavior of these com-pounds was studied using cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. The antioxidant activity of complexes was estimated by means of the electrochemical assay based on the hydrogen atom transfer reaction to the stable radical 2,2’-diphenyl-1-picrylhydrazyl (DPPH). The RDE method was applied for this process monitoring. It was shown that the efficiency of the metal complexes (Cu2+,Co2+,Mn2+,Ni2+,Fe3+) is practically the same order as that of free base porphyrin 1. However the Zn2+ complex demonstrates significantly higher antioxidant activity, and the stoichiometry of the reaction was determined as σ = 4. The results demonstrate that porphyrin macrocycle can directly affect the antioxidant properties of 2,6-diisobornylphenol.展开更多
磁场是太阳物理的第1观测量,当前太阳磁场观测研究正迈向大视场、高时空分辨率、高偏振测量精度以及空间观测的时代.中国首颗太阳观测卫星-先进天基太阳天文台(ASO-S)也配置了具有高时空分辨率、高磁场灵敏度的全日面矢量磁像仪(FMG)载...磁场是太阳物理的第1观测量,当前太阳磁场观测研究正迈向大视场、高时空分辨率、高偏振测量精度以及空间观测的时代.中国首颗太阳观测卫星-先进天基太阳天文台(ASO-S)也配置了具有高时空分辨率、高磁场灵敏度的全日面矢量磁像仪(FMG)载荷,针对FMG载荷的需求,讨论了大面阵、高帧频互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)图像传感器应用于太阳磁场观测的可行性.首先,基于滤光器型太阳磁像仪观测的原理,比较分析了目前CMOS图像传感器(可用的或是可选的两种快门模式)的特点,指出全局快门类型更适合FMG;其次搭建了CMOS传感器实验室测试系统,测量了CMOS图像传感器的像素增益及其分布规律;最后在怀柔太阳观测基地的全日面太阳望远镜上开展了实测验证,获得预期成果.在这些研究基础上,形成了FMG载荷探测器选型方向.展开更多
基金partly supported by National Natural Science Foundation of China(No.51175095)Guangdong Provincial Natural Science Foundation of China(No.10251009001000001)the Guangdong Provincial Project of Science and Technology Innovation of Discipline Construction,China(No.2013KJCX0063)
文摘During deep penetration laser welding,there exist plume（weak plasma） and spatters,which are the results of weld material ejection due to strong laser heating.The characteristics of plume and spatters are related to welding stability and quality.Characteristics of metallic plume and spatters were investigated during high-power disk laser bead-on-plate welding of Type 304 austenitic stainless steel plates at a continuous wave laser power of 10 kW.An ultraviolet and visible sensitive high-speed camera was used to capture the metallic plume and spatter images.Plume area,laser beam path through the plume,swing angle,distance between laser beam focus and plume image centroid,abscissa of plume centroid and spatter numbers are defined as eigenvalues,and the weld bead width was used as a characteristic parameter that reflected welding stability.Welding status was distinguished by SVM（support vector machine） after data normalization and characteristic analysis.Also,PCA（principal components analysis） feature extraction was used to reduce the dimensions of feature space,and PSO（particle swarm optimization） was used to optimize the parameters of SVM.Finally a classification model based on SVM was established to estimate the weld bead width and welding stability.Experimental results show that the established algorithm based on SVM could effectively distinguish the variation of weld bead width,thus providing an experimental example of monitoring high-power disk laser welding quality.
文摘A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels in water. A 100 mL water sample was adjusted to pH 5.6 with nitric acid and a 1 mol?L–1 ammonium acetate solution, and then passed through an IED (diameter, 47 mm;effective filtering diameter, 35 mm) at a flow rate of 80 - 100 mL?min–1 to preconcentrate seven analytes. The IED was dried at 100?C for 20 min in an electric oven, and 110 - 145 small disks, each 2 mm in diameter, were punched out from the IED. A small disk was introduced into the graphite furnace and atomized according to a heating program. For Cd, Sn, Pb, and Bi measurements, Pd was used as a chemical modifier to enhance the absorbances. Calibration was performed using aqueous standard solutions. The detection limits, corresponding to three times the standard deviation (n = 5) of the blank values, were 0.092 μg·L–1 for Co, 0.12 μg·L–1 for Ni, 0.40 μg·L–1 for Cu, 0.077 μg·L–1 for Cd, 0.92 μg·L–1 for Sn, 0.61 μg·L–1 for Pb, and 0.80 μg·L–1 for Bi with an enrichment factor of 140 using a 100-mL water sample. A spike test for the seven analytes in tap water, rainwater, river water, and mineral drinking water showed quantitative recoveries (93% - 108%).
文摘Metal derivative/graphitic carbon nitride(g-C_(3)N_(4))association is found promising in providing sustainable hydrogen production by photocatalytic water splitting process.Number of works reported on the synthesis and application of various metal based g-C_(3)N_(4)composites are increasing day by day.Mechanism of charge separation varies according to the metal candidate that gets couple with g-C_(3)N_(4).The present article thus explores the interesting chemistry behind various metal based heterojunction and demonstrates the charge separation route.A thorough investigation has been done on the current research trend in the area.As many metal free g-C_(3)N_(4)composites are reported nowadays as an alternative to metal derivatives,here compares metallic and metal free derivatives of g-C_(3)N_(4)based on four critical requirements of an industrial catalyst,ie,activity,stability,cost and toxicity.Challenges and future direction in the area are also discussed with significance.The systematic discussion and schematic illustration of charge transfer process in different heterojunctions with reference to the reported systems,given in the article can definitely contribute to the design and development of more efficient g-C_(3)N_(4)based heterojunctions in future for hydrogen production application.
文摘The complexes of biogenic metals (Zn2+,Cu2+,Co2+,Mn3+,Fe3+) based on meso-tetra(3,5-diisobor- nyl-4-hydroxyphenyl)porphyrin 1 were synthesized. The electrochemical behavior of these com-pounds was studied using cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. The antioxidant activity of complexes was estimated by means of the electrochemical assay based on the hydrogen atom transfer reaction to the stable radical 2,2’-diphenyl-1-picrylhydrazyl (DPPH). The RDE method was applied for this process monitoring. It was shown that the efficiency of the metal complexes (Cu2+,Co2+,Mn2+,Ni2+,Fe3+) is practically the same order as that of free base porphyrin 1. However the Zn2+ complex demonstrates significantly higher antioxidant activity, and the stoichiometry of the reaction was determined as σ = 4. The results demonstrate that porphyrin macrocycle can directly affect the antioxidant properties of 2,6-diisobornylphenol.
文摘磁场是太阳物理的第1观测量,当前太阳磁场观测研究正迈向大视场、高时空分辨率、高偏振测量精度以及空间观测的时代.中国首颗太阳观测卫星-先进天基太阳天文台(ASO-S)也配置了具有高时空分辨率、高磁场灵敏度的全日面矢量磁像仪(FMG)载荷,针对FMG载荷的需求,讨论了大面阵、高帧频互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)图像传感器应用于太阳磁场观测的可行性.首先,基于滤光器型太阳磁像仪观测的原理,比较分析了目前CMOS图像传感器(可用的或是可选的两种快门模式)的特点,指出全局快门类型更适合FMG;其次搭建了CMOS传感器实验室测试系统,测量了CMOS图像传感器的像素增益及其分布规律;最后在怀柔太阳观测基地的全日面太阳望远镜上开展了实测验证,获得预期成果.在这些研究基础上,形成了FMG载荷探测器选型方向.
