Potential vorticity(PV)streamers are elongated filaments of high PV intrusions that generally exhibit three distinct shapes:ordinarily southwestward,hook,and treble-clef,each with significant influences on weather.The...Potential vorticity(PV)streamers are elongated filaments of high PV intrusions that generally exhibit three distinct shapes:ordinarily southwestward,hook,and treble-clef,each with significant influences on weather.These PV streamers are most frequent over arid and semi-arid Central Asia in the mid–high latitudes.This study applied the Mask Region-based Convolutional Neural Network algorithm(Mask R-CNN)to PV streamers on the dynamical tropopause during the warm season(May to September)over the years 2000–04 to train a weighted variational model capable of identifying these different shapes.The trained model demonstrated a strong ability to distinguish between the three shapes.A climatological analysis of PV streamers over Central Asia spanning 2000 to 2021 revealed an increasingly deep and pronounced reversal of circulation from ordinary to treble-clef shapes.The treble-clef shape featured a PV tower and distinct cut-off low in the troposphere,but the associated upward motions and precipitation were confined within approximately 1200 km to the east of the PV tower.Although the hook-shape PV streamers were linked to a weaker cut-off low,the extent of upward motion and precipitation was nearly double that of the treble-clef category.In contrast,the ordinary PV streamer was primarily associated with tropopause Rossby wave breaking and exhibited relatively shallow characteristics,which resulted in moderate upward motion and precipitation to 500 km to its east.展开更多
Data Streamer是微软开发的数据流采集插件,能够实时读取传感器采集的数据到Excel中进行分析。分别以“摩擦力实验数据可视化”“大气压强实验数据可视化”“固体融化时温度变化的规律实验数据可视化”为例,论述了如何在实验研究中结合...Data Streamer是微软开发的数据流采集插件,能够实时读取传感器采集的数据到Excel中进行分析。分别以“摩擦力实验数据可视化”“大气压强实验数据可视化”“固体融化时温度变化的规律实验数据可视化”为例,论述了如何在实验研究中结合传感技术,综合应用Data Streamer的数据采集技术和Excel的可视化分析技术,实时采集实验数据,并将其转换为实时变化的动态图象进行可视化展示和分析,为实验数据的可视化分析提供了新的思路和方法,可帮助研究者更准确地理解和掌握实验数据的变化规律。展开更多
Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude analysis.In this work,sphere-plane ...Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude analysis.In this work,sphere-plane gap discharge tests were carried out under the gap distance of 5 m at the Qinghai Ultra High Voltage(UHV)test base at an altitude of 2200 m.The experiments measured the physical parameters such as the discharge current,electric field intensity and instantaneous optical power.The duration of the dark period and the critical charge of streamer-toleader transition were obtained at high altitude.Based on radial thermal expansion of the streamer stem,we established a modified streamer-to-leader transition model of the sphere-plane gap discharge at high altitude,and calculated the stem temperature,stem radii and the duration of streamer-to-leader transition.Compared with the measured duration of sphere-plane electrode discharge at an altitude of 2200 m,the error rate of the modified model was 0.94%,while the classical model was 6.97%,demonstrating the effectiveness of the modified model.From the comparisons and analysis,several suggestions are proposed to improve the numerical model for further quantitative investigations of the leader inception.展开更多
Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning imp...Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline(stage 1), rapid velocity rise(stage 2)and slow velocity decline(stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.展开更多
In this study,based on two CMOS cameras,an orthogonal optical observation platform has been set up for positive streamer branches under 1 m rod-plate air gap.The Monopodia branch and the Dichotomous branch have been p...In this study,based on two CMOS cameras,an orthogonal optical observation platform has been set up for positive streamer branches under 1 m rod-plate air gap.The Monopodia branch and the Dichotomous branch have been proposed for steamer branch classification.The branch length,the branch angle and the optical diameter are statistical obtained and compared for the two branch types under different impulse voltages.The empirical function between the branch length Ls and the inception voltage Ui of the Monopodia branch has been obtained.The distributions of the branch angle and the axial angle of the two types have been given,and the mean optical diameters have been provided.Based on the comparisons,the formation mechanism of the two branch types has been proposed.This experimental result can provide the basic data to the numerical calculation of positive long air gap discharge.展开更多
This paper is aimed at the streamers in natural esters （vegetable oils） in point--plane electrode arrangement under lightning impulse voltage. The shape, stopping length, velocity and current of streamers are invest...This paper is aimed at the streamers in natural esters （vegetable oils） in point--plane electrode arrangement under lightning impulse voltage. The shape, stopping length, velocity and current of streamers are investigated. Six untreated commercial oils extracted from grape seeds, sunflower and rape seeds, corn, rice and sesame that could constitute potential liquids for high voltage applications are tested. A naphthenic mineral oil is also tested for comparison. It＇s shown that the streamers are filamentary for both polarities. For a given voltage, the stopping lengths （Lf） of streamers are longer when the point is positive than when it is negative; also, except mineral oil when the point is negative, the values of Lf-are very close in all tested oils. The streamers＇ velocities are in the same range for all vegetable oils and they vary between 0.4 km/s and 1.2 km/s for positive polarity and 0.2 km/s and 0.8 km/s for negative polarity.展开更多
Receiver ghost reflections adversely affect variable-depth streamer （VDS） data acquisition. In addition, the frequency notches caused by the interference between receiver ghosts and primary waves strongly affect sei...Receiver ghost reflections adversely affect variable-depth streamer （VDS） data acquisition. In addition, the frequency notches caused by the interference between receiver ghosts and primary waves strongly affect seismic data processing and imaging. We developed a high-resolution Radon transform algorithm and used it to predict receiver ghosts from VDS data. The receiver ghost reflections are subtracted and removed from the raw data. We propose a forward Radon transform operator of VDS data in the frequency domain and, based on the ray paths of the receiver ghosts, we propose an inverse Radon transform operator. We apply the proposed methodology to model and field data with good results. We use matching and subtracting modules of commercially available seismic data processing software to remove the receiver ghosts. The frequency notches are compensated and the effective frequency bandwidth of the seismic data broadens.展开更多
The paper presents research data on positive and negative coronas inatmospheric pressure air in a highly inhomogeneous electric field. Thedata show that irrespective of the polarity of pointed electrodes placed ina hi...The paper presents research data on positive and negative coronas inatmospheric pressure air in a highly inhomogeneous electric field. Thedata show that irrespective of the polarity of pointed electrodes placed ina high electric field (200 kV/cm), this type of discharge develops via ballstreamers even if the gap voltage rises slowly (0.2 kV/ms). The start voltageof first positive streamers, compared to negative ones, is higher andthe amplitude and the frequency of their current pulses are much lower:about two times and more than two orders of magnitude, respectively.The higher frequency of current pulses from negative streamers provideshigher average currents and larger luminous areas of negative coronascompared to positive ones. Positive and negative cylindrical streamersfrom a pointed to a plane electrode are detected and successive dischargetransitions at both polarities are identified.展开更多
The mechanisms of streamer generation and propagation in double-sided pulsed surface dielectric barrier discharge(SDBD)on both sides have been analyzed and investigated by experiment and numerical simulation.The fully...The mechanisms of streamer generation and propagation in double-sided pulsed surface dielectric barrier discharge(SDBD)on both sides have been analyzed and investigated by experiment and numerical simulation.The fully exposed asymmetric SDBD has two discharge processes located on the high voltage electrode(HVE)side and the ground electrode(GE)side.Discharge images of the HVE side and GE side are taken by a digital camera under continuous pulse and ICCD(Intensified Charge Coupled Device)is utilized to diagnose the generation and propagation of streamers in single pulse discharge.In order to understand the physical mechanisms of streamer evolution more deeply,we establish a 2D simulation model and analyze it from the aspects of electron density,ion density,reduced electric field and electron impact ionization source term.The results show that the primary and secondary discharges on the HVE side and the GE side of the double-sided SDBD are composed of positive streamer and negative streamer,respectively.On the HVE side,the accumulation of positive charges on the dielectric surface causes the direction of the electric field to reverse,which is the principal factor for the polarity reversal of the streamer.On the GE side,both the negative charges accumulated on the dielectric surface and the falling voltage are the key factors for the streamer polarity switch.展开更多
It is considered the mechanism of streamer discharge in the wide-gap semiconductors as a highly effective method of the laser excitation on the basis of representation about the phenomenon of light self-trapping of th...It is considered the mechanism of streamer discharge in the wide-gap semiconductors as a highly effective method of the laser excitation on the basis of representation about the phenomenon of light self-trapping of the discharge, providing their high propagation velocity down to v- 5 ×10^9 sm/s, the crystallographic orientation, filamentary character at thickness of the channel about 1 μm and absence of destructions of a crystal.展开更多
Variable-depth streamer seismic data are characterized by low and high frequencies and can be used to obtain high-quality and resolution images of complex subsurface structures. Taking advantage of the frequency range...Variable-depth streamer seismic data are characterized by low and high frequencies and can be used to obtain high-quality and resolution images of complex subsurface structures. Taking advantage of the frequency range in the variable-depth streamer data, we propose the simultaneous inversion of prestack data from variable-offset stack gathers to obtain the P-wave impedance, S-wave impedance, and density. Next, we validate the method by using model and actual variable-depth streamer data from the Huizhou block. The results suggest that the broadband data recorded by variable-depth streamers improve the signal-to-noise ratio and quality of the inversion results and outperform the constant-depth streamer data in delineating the underground stratigraphy.展开更多
Local electron mean energy （LEME） has a direct effect on the rates of collisional ionization of molecules and atoms by electrons. Electron-impact ionization plays an important role and is the main process for the pr...Local electron mean energy （LEME） has a direct effect on the rates of collisional ionization of molecules and atoms by electrons. Electron-impact ionization plays an important role and is the main process for the production of charged particles in a primary streamer discharge. Detailed research on the LEME profile in a primary streamer discharge is extremely important for a comprehensive understanding of the local physical mechanism of a streamer. In this study, the LEME profile of the primary streamer discharge in oxygen-nitrogen mixtures with a pin-plate gap of 0.5 cm under an impulse voltage is investigated using a fluid model. The fluid model includes the electron mean energy density equation, as well as continuity equations for electrons and ions and Poisson＇s electric field equation. The study finds that, except in the initial stage of the primary streamer, the LEME in the primary streamer tip tends to increase as the oxygen-nitrogen mole ratio increases and the pressure decreases. When the primary streamer bridges the gap, the LEME in the primary streamer channel is smaller than the first ionization energies of oxygen and nitrogen. The LEME in the primary streamer channel then decreases as the oxygen-nitrogen mole ratio increases and the pressure increases. The LEME in the primary streamer tip is primarily dependent on the reduced electric field with mole ratios of oxygen-nitrogen given in the oxygen-nitrogen mixtures.展开更多
Photocatalyst was prepared by immobilizing TiO2 on glass beads using the traditional sol-gel method. Ultraviolet light （UV） produced by pulsed streamer discharge was then used to induce photocatalytic activity of Ti...Photocatalyst was prepared by immobilizing TiO2 on glass beads using the traditional sol-gel method. Ultraviolet light （UV） produced by pulsed streamer discharge was then used to induce photocatalytic activity of TiO2 photocatalyst. Decolouration efficiency of the representative azo dye （acid orange 7, AOT） was investigated using the synergistic system of pulsed streamer discharge plasma and TiO2 photocatalysis. The obtained results showed that the decolouration rate of AO7 could be increased by 16.7% under the condition of adding supported TiO2 in the pulsed streamer discharge system, compared to that in the sole pulsed streamer discharge plasma system, due to the synergistic effect of pulsed streamer discharge and TiO2 photocatalysis induced by pulsed streamer discharge. The synergistic system of pulsed streamer discharge and TiO2 photocatalyst was found to have more reactive radicals for degradation of organic compounds in water.展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.42275063 and U20A2097)the Open Grants of the State Key Laboratory of Severe Weather(Grant No.2023LASW-B29)。
文摘Potential vorticity(PV)streamers are elongated filaments of high PV intrusions that generally exhibit three distinct shapes:ordinarily southwestward,hook,and treble-clef,each with significant influences on weather.These PV streamers are most frequent over arid and semi-arid Central Asia in the mid–high latitudes.This study applied the Mask Region-based Convolutional Neural Network algorithm(Mask R-CNN)to PV streamers on the dynamical tropopause during the warm season(May to September)over the years 2000–04 to train a weighted variational model capable of identifying these different shapes.The trained model demonstrated a strong ability to distinguish between the three shapes.A climatological analysis of PV streamers over Central Asia spanning 2000 to 2021 revealed an increasingly deep and pronounced reversal of circulation from ordinary to treble-clef shapes.The treble-clef shape featured a PV tower and distinct cut-off low in the troposphere,but the associated upward motions and precipitation were confined within approximately 1200 km to the east of the PV tower.Although the hook-shape PV streamers were linked to a weaker cut-off low,the extent of upward motion and precipitation was nearly double that of the treble-clef category.In contrast,the ordinary PV streamer was primarily associated with tropopause Rossby wave breaking and exhibited relatively shallow characteristics,which resulted in moderate upward motion and precipitation to 500 km to its east.
基金supported by National Natural Science Foundation of China(Scientific Funds for Young Scientists)(No.52007064)。
文摘Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude analysis.In this work,sphere-plane gap discharge tests were carried out under the gap distance of 5 m at the Qinghai Ultra High Voltage(UHV)test base at an altitude of 2200 m.The experiments measured the physical parameters such as the discharge current,electric field intensity and instantaneous optical power.The duration of the dark period and the critical charge of streamer-toleader transition were obtained at high altitude.Based on radial thermal expansion of the streamer stem,we established a modified streamer-to-leader transition model of the sphere-plane gap discharge at high altitude,and calculated the stem temperature,stem radii and the duration of streamer-to-leader transition.Compared with the measured duration of sphere-plane electrode discharge at an altitude of 2200 m,the error rate of the modified model was 0.94%,while the classical model was 6.97%,demonstrating the effectiveness of the modified model.From the comparisons and analysis,several suggestions are proposed to improve the numerical model for further quantitative investigations of the leader inception.
基金supported by the Beijing Science Fund for Distinguished Young Scholars(No.JQ22009)National Natural Science Foundation of China(No.51977198)。
文摘Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline(stage 1), rapid velocity rise(stage 2)and slow velocity decline(stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.
基金the National Basic Research Program of China(973 Program)(2011CB209403)。
文摘In this study,based on two CMOS cameras,an orthogonal optical observation platform has been set up for positive streamer branches under 1 m rod-plate air gap.The Monopodia branch and the Dichotomous branch have been proposed for steamer branch classification.The branch length,the branch angle and the optical diameter are statistical obtained and compared for the two branch types under different impulse voltages.The empirical function between the branch length Ls and the inception voltage Ui of the Monopodia branch has been obtained.The distributions of the branch angle and the axial angle of the two types have been given,and the mean optical diameters have been provided.Based on the comparisons,the formation mechanism of the two branch types has been proposed.This experimental result can provide the basic data to the numerical calculation of positive long air gap discharge.
文摘This paper is aimed at the streamers in natural esters （vegetable oils） in point--plane electrode arrangement under lightning impulse voltage. The shape, stopping length, velocity and current of streamers are investigated. Six untreated commercial oils extracted from grape seeds, sunflower and rape seeds, corn, rice and sesame that could constitute potential liquids for high voltage applications are tested. A naphthenic mineral oil is also tested for comparison. It＇s shown that the streamers are filamentary for both polarities. For a given voltage, the stopping lengths （Lf） of streamers are longer when the point is positive than when it is negative; also, except mineral oil when the point is negative, the values of Lf-are very close in all tested oils. The streamers＇ velocities are in the same range for all vegetable oils and they vary between 0.4 km/s and 1.2 km/s for positive polarity and 0.2 km/s and 0.8 km/s for negative polarity.
文摘Receiver ghost reflections adversely affect variable-depth streamer （VDS） data acquisition. In addition, the frequency notches caused by the interference between receiver ghosts and primary waves strongly affect seismic data processing and imaging. We developed a high-resolution Radon transform algorithm and used it to predict receiver ghosts from VDS data. The receiver ghost reflections are subtracted and removed from the raw data. We propose a forward Radon transform operator of VDS data in the frequency domain and, based on the ray paths of the receiver ghosts, we propose an inverse Radon transform operator. We apply the proposed methodology to model and field data with good results. We use matching and subtracting modules of commercially available seismic data processing software to remove the receiver ghosts. The frequency notches are compensated and the effective frequency bandwidth of the seismic data broadens.
文摘The paper presents research data on positive and negative coronas inatmospheric pressure air in a highly inhomogeneous electric field. Thedata show that irrespective of the polarity of pointed electrodes placed ina high electric field (200 kV/cm), this type of discharge develops via ballstreamers even if the gap voltage rises slowly (0.2 kV/ms). The start voltageof first positive streamers, compared to negative ones, is higher andthe amplitude and the frequency of their current pulses are much lower:about two times and more than two orders of magnitude, respectively.The higher frequency of current pulses from negative streamers provideshigher average currents and larger luminous areas of negative coronascompared to positive ones. Positive and negative cylindrical streamersfrom a pointed to a plane electrode are detected and successive dischargetransitions at both polarities are identified.
基金supported by National Natural Science Foundation of China(Nos.51877027 and 52107140)Project funded by China Postdoctoral Science Foundation(No.2021M700662)。
文摘The mechanisms of streamer generation and propagation in double-sided pulsed surface dielectric barrier discharge(SDBD)on both sides have been analyzed and investigated by experiment and numerical simulation.The fully exposed asymmetric SDBD has two discharge processes located on the high voltage electrode(HVE)side and the ground electrode(GE)side.Discharge images of the HVE side and GE side are taken by a digital camera under continuous pulse and ICCD(Intensified Charge Coupled Device)is utilized to diagnose the generation and propagation of streamers in single pulse discharge.In order to understand the physical mechanisms of streamer evolution more deeply,we establish a 2D simulation model and analyze it from the aspects of electron density,ion density,reduced electric field and electron impact ionization source term.The results show that the primary and secondary discharges on the HVE side and the GE side of the double-sided SDBD are composed of positive streamer and negative streamer,respectively.On the HVE side,the accumulation of positive charges on the dielectric surface causes the direction of the electric field to reverse,which is the principal factor for the polarity reversal of the streamer.On the GE side,both the negative charges accumulated on the dielectric surface and the falling voltage are the key factors for the streamer polarity switch.
文摘It is considered the mechanism of streamer discharge in the wide-gap semiconductors as a highly effective method of the laser excitation on the basis of representation about the phenomenon of light self-trapping of the discharge, providing their high propagation velocity down to v- 5 ×10^9 sm/s, the crystallographic orientation, filamentary character at thickness of the channel about 1 μm and absence of destructions of a crystal.
基金sponsored by Comprehensive Research of CNOOC(China) Limited(No.YXKY–2013–SZ–02)
文摘Variable-depth streamer seismic data are characterized by low and high frequencies and can be used to obtain high-quality and resolution images of complex subsurface structures. Taking advantage of the frequency range in the variable-depth streamer data, we propose the simultaneous inversion of prestack data from variable-offset stack gathers to obtain the P-wave impedance, S-wave impedance, and density. Next, we validate the method by using model and actual variable-depth streamer data from the Huizhou block. The results suggest that the broadband data recorded by variable-depth streamers improve the signal-to-noise ratio and quality of the inversion results and outperform the constant-depth streamer data in delineating the underground stratigraphy.
基金Project supported by the Funds for Innovative Research Groups of China (Grant No. 51021005)the National Basic Research Program of China (Grant No. 2009CB724504)the National Natural Science Foundation of China (Grant No. 50707036)
文摘Local electron mean energy （LEME） has a direct effect on the rates of collisional ionization of molecules and atoms by electrons. Electron-impact ionization plays an important role and is the main process for the production of charged particles in a primary streamer discharge. Detailed research on the LEME profile in a primary streamer discharge is extremely important for a comprehensive understanding of the local physical mechanism of a streamer. In this study, the LEME profile of the primary streamer discharge in oxygen-nitrogen mixtures with a pin-plate gap of 0.5 cm under an impulse voltage is investigated using a fluid model. The fluid model includes the electron mean energy density equation, as well as continuity equations for electrons and ions and Poisson＇s electric field equation. The study finds that, except in the initial stage of the primary streamer, the LEME in the primary streamer tip tends to increase as the oxygen-nitrogen mole ratio increases and the pressure decreases. When the primary streamer bridges the gap, the LEME in the primary streamer channel is smaller than the first ionization energies of oxygen and nitrogen. The LEME in the primary streamer channel then decreases as the oxygen-nitrogen mole ratio increases and the pressure increases. The LEME in the primary streamer tip is primarily dependent on the reduced electric field with mole ratios of oxygen-nitrogen given in the oxygen-nitrogen mixtures.
基金supported by the National Natural Science Foundation Committee of China(No.20377006)Foundation of Education Ministry of China(No.2005141002)
文摘Photocatalyst was prepared by immobilizing TiO2 on glass beads using the traditional sol-gel method. Ultraviolet light （UV） produced by pulsed streamer discharge was then used to induce photocatalytic activity of TiO2 photocatalyst. Decolouration efficiency of the representative azo dye （acid orange 7, AOT） was investigated using the synergistic system of pulsed streamer discharge plasma and TiO2 photocatalysis. The obtained results showed that the decolouration rate of AO7 could be increased by 16.7% under the condition of adding supported TiO2 in the pulsed streamer discharge system, compared to that in the sole pulsed streamer discharge plasma system, due to the synergistic effect of pulsed streamer discharge and TiO2 photocatalysis induced by pulsed streamer discharge. The synergistic system of pulsed streamer discharge and TiO2 photocatalyst was found to have more reactive radicals for degradation of organic compounds in water.
