In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass（PAM） reactor were carried out in the winter of 2014.The varia...In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass（PAM） reactor were carried out in the winter of 2014.The variations of secondary aerosol formation as a function of time,OH exposure,and the concentrations of gas phase pollutants and particles were reported in this study.Two periods with distinct secondary aerosol formation potentials,marked as Period Ⅰ and Period Ⅱ,were identified during the observation.In Period Ⅰ,the secondary aerosol formation potential was high,and correlated well to the air pollutants,i.e.,SO2,NO2,and CO.The maximal secondary aerosol formation was observed with an aging time equivalent to about 3 days of atmospheric oxidation.In period Ⅱ,the secondary aerosol formation potential was low,with no obvious correlation with the air pollutants.Meanwhile,the aerosol mass decreased,instead of showing a peak,with increasing aging time.Backward trajectory analysis during the two periods confirmed that the air mass in Period Ⅰwas mainly from local sources,while it was attributed mostly to long distance transport in Period Ⅱ.The air lost its reactivity during the long transport and the particles became highly aged,resulting in a low secondary aerosol formation potential.Our experimental results indicated that the in situ measurement of the secondary aerosol formation potential could provide important information for evaluating the contributions of local emission and long distance transport to the aerosol pollution.展开更多
Local ageing defects are the main causes of cross-linked polyethylene(XLPE)power cable faults.This research aims at assessing the severity level of typical cable local ageing defects based on the high-voltage frequenc...Local ageing defects are the main causes of cross-linked polyethylene(XLPE)power cable faults.This research aims at assessing the severity level of typical cable local ageing defects based on the high-voltage frequency domain spectroscopy(FDS)non-linearity.Experimentally,typical XLPE cables ageing defect conditions are simulated,with different ageing types,degrees,and local proportions.Then,the high-voltage FDS detection is conducted and the results have been analysed.It has been found that the high-voltage FDS non-linearity is only related to the detection voltage and ageing degree.Especially,it is more sensitive to changes in the ageing severity.Thus,the local ageing defect severity assessment method based on non-linearity has been established.Additionally,the sensitivity has been compared between two diagnostic evaluation methods:the high-voltage FDS and the widely used very-low frequency method(VLF,0.1 Hz).It can be concluded from the comparison result that the proposed assessment method has higher sensitivity than that of the traditional methods.Finally,the effectiveness of the proposed method for evaluating the on-site long cables has been validated.The result demonstrates that the proposed method can assess on-site long cables and has the potential to be formed as quantitative standards.展开更多
基金supported by the Key Research Program of Chinese Academy of Sciences (No. KJZD-EW-TZ-G06-01-15)the National Natural Science Foundation of China (No. 21407158)the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (No. XDB05010300)
文摘In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass（PAM） reactor were carried out in the winter of 2014.The variations of secondary aerosol formation as a function of time,OH exposure,and the concentrations of gas phase pollutants and particles were reported in this study.Two periods with distinct secondary aerosol formation potentials,marked as Period Ⅰ and Period Ⅱ,were identified during the observation.In Period Ⅰ,the secondary aerosol formation potential was high,and correlated well to the air pollutants,i.e.,SO2,NO2,and CO.The maximal secondary aerosol formation was observed with an aging time equivalent to about 3 days of atmospheric oxidation.In period Ⅱ,the secondary aerosol formation potential was low,with no obvious correlation with the air pollutants.Meanwhile,the aerosol mass decreased,instead of showing a peak,with increasing aging time.Backward trajectory analysis during the two periods confirmed that the air mass in Period Ⅰwas mainly from local sources,while it was attributed mostly to long distance transport in Period Ⅱ.The air lost its reactivity during the long transport and the particles became highly aged,resulting in a low secondary aerosol formation potential.Our experimental results indicated that the in situ measurement of the secondary aerosol formation potential could provide important information for evaluating the contributions of local emission and long distance transport to the aerosol pollution.
基金National Key Research and Development Program of China,Grant/Award Number:2023YFB2406900。
文摘Local ageing defects are the main causes of cross-linked polyethylene(XLPE)power cable faults.This research aims at assessing the severity level of typical cable local ageing defects based on the high-voltage frequency domain spectroscopy(FDS)non-linearity.Experimentally,typical XLPE cables ageing defect conditions are simulated,with different ageing types,degrees,and local proportions.Then,the high-voltage FDS detection is conducted and the results have been analysed.It has been found that the high-voltage FDS non-linearity is only related to the detection voltage and ageing degree.Especially,it is more sensitive to changes in the ageing severity.Thus,the local ageing defect severity assessment method based on non-linearity has been established.Additionally,the sensitivity has been compared between two diagnostic evaluation methods:the high-voltage FDS and the widely used very-low frequency method(VLF,0.1 Hz).It can be concluded from the comparison result that the proposed assessment method has higher sensitivity than that of the traditional methods.Finally,the effectiveness of the proposed method for evaluating the on-site long cables has been validated.The result demonstrates that the proposed method can assess on-site long cables and has the potential to be formed as quantitative standards.
