The effects of feed gas flow rate and operating current on the electrical characteristics and dynamic behavior of a rotating gliding arc （RGA） plasma codriven by a magnetic field and tangential flow were investigate...The effects of feed gas flow rate and operating current on the electrical characteristics and dynamic behavior of a rotating gliding arc （RGA） plasma codriven by a magnetic field and tangential flow were investigated.The operating current has been shown to significantly affect the time-resolved voltage waveforms of the discharge,particularly at flow rate =21 min^-1.When the current was lower than 140 mA,sinusoidal waveforms with regular variation periods of 13.5-17.0 ms can be observed （flow rate =21 min^-1）.The restrike mode characterized by serial sudden drops of voltage appeared under all studied conditions.Increasing the flow rate from 8 to 121 min^-1 （at the same current） led to a shift of arc rotation mode which would then result in a significant drop of discharge voltage （around 120-200 V）.For a given flow rate,the reduction of current resulted in a nearly linear increase of voltage.展开更多
When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation betw...When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between the distribution of solute at solid-liquid interface and current density was established, and the effect of current on the distribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and the radius of curvature at the dendritic tip was discussed. The results show that as the current density increases, the distribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm 2, the latter varies significantly.展开更多
Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave -current coexistent field. Testing conditions include three i...Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave -current coexistent field. Testing conditions include three interaction angles 0', 45', 90' and two kinds of median sizes (0.38 and 1.10 mm). The results of transport rate show that the net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress of waves, mean shear stress of current and the grain size.展开更多
The effect of current density on the morphology of Zn electrodepositsprepared by a flow-channel cell was investigated by scanning electron microscopy (SEM). It was foundthat the morphology of Zn electrodeposits evolve...The effect of current density on the morphology of Zn electrodepositsprepared by a flow-channel cell was investigated by scanning electron microscopy (SEM). It was foundthat the morphology of Zn electrodeposits evolves from thin-layered hexagonal eta -phase crystalsto pyramidal eta -phase particles with increasing the current density. The morphological evolutionat various flow rates was also examined and the results show that the morphological evolution at alower flow rate is more remarkable than that at a higher flow rate with increasing the currentdensity. To reveal the mechanism of the morphological evolution in detail, the atomic configurationon both (0001)_eta and {1100 }_eta planes under different current densities was investigated, it wasnoted that a specify current density could provide a good condition for the layered epitaxialgrowth of hexagonal T)-phase.展开更多
In this paper, we present evolutions of the phase space density(PSD) spectra of ring current(RC) ions based on observations made by Van Allen Probe B during a geomagnetic storm on 23–24 August 2016. By analyzing PSD ...In this paper, we present evolutions of the phase space density(PSD) spectra of ring current(RC) ions based on observations made by Van Allen Probe B during a geomagnetic storm on 23–24 August 2016. By analyzing PSD spectra ratios from the initial phase to the main phase of the storm, we find that during the main phase, RC ions with low magnetic moment μ values can penetrate deeper into the magnetosphere than can those with high μ values, and that the μ range of PSD enhancement meets the relationship: S(O^+) >S(He^+)>S(H^+). Based on simultaneously observed ULF waves, theoretical calculation suggests that the radial transport of RC ions into the deep inner magnetosphere is caused by drift-bounce resonance interactions, and the efficiency of these resonance interactions satisfies the relationship: η(O^+) > η(He^+) > η(H^+), leading to the differences in μ range of PSD enhancement for different RC ions. In the recovery phase,the observed decay rates for different RC ions meet the relationship: R(O^+) > R(He^+) > R(H^+), in accordance with previous theoretical calculations, i.e., the charge exchange lifetime of O^+ is shorter than those of H^+ and He^+.展开更多
基于主动换相换流器(actively commutated converter,ACC)的高压直流输电(high voltage direct current,HVDC)技术具备构网运行能力且无换相失败风险,在大规模新能源外送领域具有良好的应用前景。调制策略是ACC换流站正常运行的前提,但...基于主动换相换流器(actively commutated converter,ACC)的高压直流输电(high voltage direct current,HVDC)技术具备构网运行能力且无换相失败风险,在大规模新能源外送领域具有良好的应用前景。调制策略是ACC换流站正常运行的前提,但现有高频、中频、基频3类调制方式在串联器件电压均衡、输出谐波特性、运行效率等方面各有优劣,不同场景及工况下的调制策略适配困难。针对上述问题,确立适应新能源送出的ACC-HVDC换流站调制策略性能指标;分别对5种典型调制策略的交流输出特性、直流电流利用率、运行损耗等指标进行量化对比,实现复杂场景多工况ACC调制策略的最优选择;最后,在MATLAB/Simulink中搭建ACC-HVDC电磁暂态仿真模型,对上述理论分析和算例进行验证。展开更多
基金supported by National Natural Science Foundation of China(51576174)
文摘The effects of feed gas flow rate and operating current on the electrical characteristics and dynamic behavior of a rotating gliding arc （RGA） plasma codriven by a magnetic field and tangential flow were investigated.The operating current has been shown to significantly affect the time-resolved voltage waveforms of the discharge,particularly at flow rate =21 min^-1.When the current was lower than 140 mA,sinusoidal waveforms with regular variation periods of 13.5-17.0 ms can be observed （flow rate =21 min^-1）.The restrike mode characterized by serial sudden drops of voltage appeared under all studied conditions.Increasing the flow rate from 8 to 121 min^-1 （at the same current） led to a shift of arc rotation mode which would then result in a significant drop of discharge voltage （around 120-200 V）.For a given flow rate,the reduction of current resulted in a nearly linear increase of voltage.
文摘When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between the distribution of solute at solid-liquid interface and current density was established, and the effect of current on the distribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and the radius of curvature at the dendritic tip was discussed. The results show that as the current density increases, the distribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm 2, the latter varies significantly.
基金the National Natural Science Foundation of China under contract No..59579014.
文摘Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave -current coexistent field. Testing conditions include three interaction angles 0', 45', 90' and two kinds of median sizes (0.38 and 1.10 mm). The results of transport rate show that the net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress of waves, mean shear stress of current and the grain size.
文摘The effect of current density on the morphology of Zn electrodepositsprepared by a flow-channel cell was investigated by scanning electron microscopy (SEM). It was foundthat the morphology of Zn electrodeposits evolves from thin-layered hexagonal eta -phase crystalsto pyramidal eta -phase particles with increasing the current density. The morphological evolutionat various flow rates was also examined and the results show that the morphological evolution at alower flow rate is more remarkable than that at a higher flow rate with increasing the currentdensity. To reveal the mechanism of the morphological evolution in detail, the atomic configurationon both (0001)_eta and {1100 }_eta planes under different current densities was investigated, it wasnoted that a specify current density could provide a good condition for the layered epitaxialgrowth of hexagonal T)-phase.
基金supported by the National Natural Science Foundation of China (41925018, 41874194)
文摘In this paper, we present evolutions of the phase space density(PSD) spectra of ring current(RC) ions based on observations made by Van Allen Probe B during a geomagnetic storm on 23–24 August 2016. By analyzing PSD spectra ratios from the initial phase to the main phase of the storm, we find that during the main phase, RC ions with low magnetic moment μ values can penetrate deeper into the magnetosphere than can those with high μ values, and that the μ range of PSD enhancement meets the relationship: S(O^+) >S(He^+)>S(H^+). Based on simultaneously observed ULF waves, theoretical calculation suggests that the radial transport of RC ions into the deep inner magnetosphere is caused by drift-bounce resonance interactions, and the efficiency of these resonance interactions satisfies the relationship: η(O^+) > η(He^+) > η(H^+), leading to the differences in μ range of PSD enhancement for different RC ions. In the recovery phase,the observed decay rates for different RC ions meet the relationship: R(O^+) > R(He^+) > R(H^+), in accordance with previous theoretical calculations, i.e., the charge exchange lifetime of O^+ is shorter than those of H^+ and He^+.
文摘基于主动换相换流器(actively commutated converter,ACC)的高压直流输电(high voltage direct current,HVDC)技术具备构网运行能力且无换相失败风险,在大规模新能源外送领域具有良好的应用前景。调制策略是ACC换流站正常运行的前提,但现有高频、中频、基频3类调制方式在串联器件电压均衡、输出谐波特性、运行效率等方面各有优劣,不同场景及工况下的调制策略适配困难。针对上述问题,确立适应新能源送出的ACC-HVDC换流站调制策略性能指标;分别对5种典型调制策略的交流输出特性、直流电流利用率、运行损耗等指标进行量化对比,实现复杂场景多工况ACC调制策略的最优选择;最后,在MATLAB/Simulink中搭建ACC-HVDC电磁暂态仿真模型,对上述理论分析和算例进行验证。
