By means of a coaxial apparatus, microsecond charging have been carried out with ferent ethylene glycol concentrations of ethylene pressurized water breakdown experiments with different surface roughness of electrodes...By means of a coaxial apparatus, microsecond charging have been carried out with ferent ethylene glycol concentrations of ethylene pressurized water breakdown experiments with different surface roughness of electrodes and difglycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows： （1） the breakdown stress formula is modified to E = 0.561MA^-1/10teff^-1/^NP^1/8 ;（2） the coefficient M is significantly increased by surface polishing and ethylene glycol additive; （3） it is accumulative for the capacity of improving electrical breakdown strength for surface polishing, ethylene glycol additive, and pressurization, of which pressurization is the most effective method; （4） the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; （5） for pressurization and surface polishing, the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric.展开更多
The influence of the energy of femtosecond laser pulses on the intensity of Fe I （371.99 nm） emission line and the continuous spectrum of the plasma generated on the surface of Fe^3＋ water solution by a Ti： sapphi...The influence of the energy of femtosecond laser pulses on the intensity of Fe I （371.99 nm） emission line and the continuous spectrum of the plasma generated on the surface of Fe^3＋ water solution by a Ti： sapphire laser radiation with pulse duration 〈45 fs and energies up to 7 mJ is determined. A calibration curve was obtained for Fe3＋ concentration range from 0.5 g/L to the limit of detection in water solution, and its saturation was detected for concentrations above 0.25 g/L, which is ascribed to self-absorption. The 3σ- limit of detection obtained for Fe in water solution is 2.6 mg/L in the case of 7 mJ laser pulse energy. It is found that an increase of laser pulse energy insignificantly affects on LOD in the time-resolved LIBS and leads to a slight improvement of the limit of detection.展开更多
Water breakdown studies by Nd-YAG laser pulses of duration 100 fs, 30 ps and 6 ns at wavelength 1064 nm are pre- formed to investigate the physical mechanisms which couple the laser energy into the medium. Calculation...Water breakdown studies by Nd-YAG laser pulses of duration 100 fs, 30 ps and 6 ns at wavelength 1064 nm are pre- formed to investigate the physical mechanisms which couple the laser energy into the medium. Calculations are carried out applying a modified kinetic model of water breakdown previously developed by Kennedy (1995) to investigate the correlation between threshold intensity of breakdown and laser pulse length. The modifications considered the introduction of diffusion and recombination loss processes which might take place under the experimental conditions applied in these calculations. The validity of the model is tested by comparing the calculated threshold intensities and the experimentally measured ones where good agreement is shown. The study of the time evolution of the electron density clarifies the correlation between the pulse length and dominant ionization mechanism. The analysis of the spatial distribution of the electron density along the radial and axial distances of the focal spot showed that the size of the formed plasma increases with the increase of the pulse length. On the other hand, studies of self-focusing effect illustrated that under the investigated experimental conditions the effect of this process has an effective contribution only at laser pulses of the order of femtosecond scale when the laser beam is focused by a lens of a focal length ≥8.0 cm. This result in turns assures that using femtosecond pulses in ophthalmic microsurgery could be a safe tool from the retinal damage.展开更多
A highly-sensitive automatic transient laser-induced breakdown spectroscopy （LIBS） system is designed and integrated. It successfully avoids the delay time selecting problem in the conventional LIBS system, and real...A highly-sensitive automatic transient laser-induced breakdown spectroscopy （LIBS） system is designed and integrated. It successfully avoids the delay time selecting problem in the conventional LIBS system, and realizes the LIBS data acquisition with high spatiotemporal resolution automatically. Multiple transient spectra can be obtained in each measurement, which will provide more information for spectral research. The water-vapour and liquid-water Raman scattering spectra are captured by this system, and the comparison of experimental water-vapour Raman scattering spectrum with theoretical data verifies the reliability of the LIBS system. Based on this system, the air laser induced air breakdown spectra are captured and analysed. The system is also useful for the research on water-vapour Raman Lidar remote sensing.展开更多
光学电流互感器具有测量精度高、结构简单、安全性高等特点,其关键组件光纤复合绝缘子承担着通信和电气绝缘的双重作用。然而,现有不同光纤植入型式的光纤复合绝缘子芯体存在相应材料、结构或工艺等缺陷,光纤与绝缘材料之间易产生界面隐...光学电流互感器具有测量精度高、结构简单、安全性高等特点,其关键组件光纤复合绝缘子承担着通信和电气绝缘的双重作用。然而,现有不同光纤植入型式的光纤复合绝缘子芯体存在相应材料、结构或工艺等缺陷,光纤与绝缘材料之间易产生界面隐患,威胁电气设备安全运行。该文提出采用低密度环氧基复合泡沫作为光纤芯体基体,植入聚乙烯型低烟无卤(low smoke zero halogen polyethylene,LSZHPE)、聚乙烯-四氟乙烯(ethylene-tetrafluoroethylene copolymer,ETFE)及裸纤3种光纤,对比分析不同类型光纤芯体物理、界面、电气等关键性能。结果表明:LSZHPE光纤体系芯体具有较优的综合性能,150 h水扩散泄漏电流低于100μA,界面击穿强度达到13.34 k V/mm,同时光纤植入后光导通损耗满足实际应用要求;ETFE光纤及裸纤体系芯体电气性能良好,但受限于材料自身特性,界面剪切强度较低,界面可靠性相对较差。该研究为光纤复合绝缘子材料选型、界面评估及结构优化提供了新思路。展开更多
基金National 863 Project of China (No. 807-2020, 803-5051)
文摘By means of a coaxial apparatus, microsecond charging have been carried out with ferent ethylene glycol concentrations of ethylene pressurized water breakdown experiments with different surface roughness of electrodes and difglycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows： （1） the breakdown stress formula is modified to E = 0.561MA^-1/10teff^-1/^NP^1/8 ;（2） the coefficient M is significantly increased by surface polishing and ethylene glycol additive; （3） it is accumulative for the capacity of improving electrical breakdown strength for surface polishing, ethylene glycol additive, and pressurization, of which pressurization is the most effective method; （4） the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; （5） for pressurization and surface polishing, the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric.
基金supported by the Russian Science Foundation(agreement#14-50-00034)(measurements of limit of detection)Russian Foundation for Basic Research(NK 15-32-20878/15)obtained in the frame of "Organization of Scientific Research"in the Far Eastern Federal University supported by Ministry of Education and Science of Russian Federation
文摘The influence of the energy of femtosecond laser pulses on the intensity of Fe I （371.99 nm） emission line and the continuous spectrum of the plasma generated on the surface of Fe^3＋ water solution by a Ti： sapphire laser radiation with pulse duration 〈45 fs and energies up to 7 mJ is determined. A calibration curve was obtained for Fe3＋ concentration range from 0.5 g/L to the limit of detection in water solution, and its saturation was detected for concentrations above 0.25 g/L, which is ascribed to self-absorption. The 3σ- limit of detection obtained for Fe in water solution is 2.6 mg/L in the case of 7 mJ laser pulse energy. It is found that an increase of laser pulse energy insignificantly affects on LOD in the time-resolved LIBS and leads to a slight improvement of the limit of detection.
文摘Water breakdown studies by Nd-YAG laser pulses of duration 100 fs, 30 ps and 6 ns at wavelength 1064 nm are pre- formed to investigate the physical mechanisms which couple the laser energy into the medium. Calculations are carried out applying a modified kinetic model of water breakdown previously developed by Kennedy (1995) to investigate the correlation between threshold intensity of breakdown and laser pulse length. The modifications considered the introduction of diffusion and recombination loss processes which might take place under the experimental conditions applied in these calculations. The validity of the model is tested by comparing the calculated threshold intensities and the experimentally measured ones where good agreement is shown. The study of the time evolution of the electron density clarifies the correlation between the pulse length and dominant ionization mechanism. The analysis of the spatial distribution of the electron density along the radial and axial distances of the focal spot showed that the size of the formed plasma increases with the increase of the pulse length. On the other hand, studies of self-focusing effect illustrated that under the investigated experimental conditions the effect of this process has an effective contribution only at laser pulses of the order of femtosecond scale when the laser beam is focused by a lens of a focal length ≥8.0 cm. This result in turns assures that using femtosecond pulses in ophthalmic microsurgery could be a safe tool from the retinal damage.
基金Project supported by the Macao Science and Technology Development Fund,Macao Special Administrative Region (SAR),China(Grant No. 021/2007/A2)the National Natural Science Foundation of China (Grant No. 11176019)
文摘A highly-sensitive automatic transient laser-induced breakdown spectroscopy （LIBS） system is designed and integrated. It successfully avoids the delay time selecting problem in the conventional LIBS system, and realizes the LIBS data acquisition with high spatiotemporal resolution automatically. Multiple transient spectra can be obtained in each measurement, which will provide more information for spectral research. The water-vapour and liquid-water Raman scattering spectra are captured by this system, and the comparison of experimental water-vapour Raman scattering spectrum with theoretical data verifies the reliability of the LIBS system. Based on this system, the air laser induced air breakdown spectra are captured and analysed. The system is also useful for the research on water-vapour Raman Lidar remote sensing.
文摘光学电流互感器具有测量精度高、结构简单、安全性高等特点,其关键组件光纤复合绝缘子承担着通信和电气绝缘的双重作用。然而,现有不同光纤植入型式的光纤复合绝缘子芯体存在相应材料、结构或工艺等缺陷,光纤与绝缘材料之间易产生界面隐患,威胁电气设备安全运行。该文提出采用低密度环氧基复合泡沫作为光纤芯体基体,植入聚乙烯型低烟无卤(low smoke zero halogen polyethylene,LSZHPE)、聚乙烯-四氟乙烯(ethylene-tetrafluoroethylene copolymer,ETFE)及裸纤3种光纤,对比分析不同类型光纤芯体物理、界面、电气等关键性能。结果表明:LSZHPE光纤体系芯体具有较优的综合性能,150 h水扩散泄漏电流低于100μA,界面击穿强度达到13.34 k V/mm,同时光纤植入后光导通损耗满足实际应用要求;ETFE光纤及裸纤体系芯体电气性能良好,但受限于材料自身特性,界面剪切强度较低,界面可靠性相对较差。该研究为光纤复合绝缘子材料选型、界面评估及结构优化提供了新思路。
