Research of magnetic self-balance used in a repetitive high voltage rectangular waveform pulse adder

Compared with a sinusoidal operation, pulsed operation has more homogeneity and more efficiency in dielectric barrier discharge. In this paper, an improved pulse adder is designed and assembled to create repetitive high voltage rectangular pulses when resistive loads or capacitive loads exist. Beyond the normal pulse adder based on solid-state switches, additional metal- oxide-semiconductor field effect transistors are used in each stage for a faster falling edge. Further, the voltage difference between stages is eliminated by balancing windings. In this paper, we represent our theoretical derivation, software simulations and hardware experiments on magnetic self-balance. The experiments show that the voltage difference between stages is eliminated by balancing windings, which matches the result of simulations with almost identical circuits and parameters.

Contrasting Trend of Wintertime Wind Speed Between Near-surface and Upper Air in China During 1979-2021

The long-term height-resolved wind trend in China under global warming still needs to be discovered.To fill this gap,in this paper we examined the climatology and long-term(1979-2021)trends of the wintertime wind speed at the near-surface and upper atmosphere in China based on long-term radiosonde measurements.At 700,500,and 400 hPa,much higher wind speed was found over eastern China,compared with western China.At 300,200,and 100 hPa,maximum wind speed was observed in the latitude zone of around 25-35°N.Furthermore,westerly winds dominated most parts of China between 20°N and 50°N at altitudes from 700 hPa to 100 hPa.A stilling was revealed for the near-surface wind from 1979-2003.From 2004 onward,the near-surface wind speed reversed from decreasing to increasing.This could be largely due to the joint impact of reduced surface roughness length,aerosol optical depth(AOD),and increased sensible heat flux in the ground surface.The decrease of AOD tended to reduce aerosol radiative forcing,thereby destabilizing the planetary boundary layer(PBL).By comparison,the wintertime wind in the upper atmosphere exhibited a significant monotonic upward trend,albeit with varying magnitude for different altitudes.In the upper troposphere,the wintertime maximum wind was observed along a westerly jet stream,with a pronounced upward trend within the zone approximately bounded by latitudes of 25-50°N,particularly above 500 hPa.This accelerating wind observed in the upper troposphere and lower stratosphere could be closely associated with the large planetary-scale meridional temperature trend gradient.Besides,the direction for the wind at the near-surface and lower troposphere(925 and 850 hPa)exhibited a larger variance over the period 1979-2021,which could be associated with the strong turbulence of PBL caused by the heterogeneous land surface.For those pressure levels higher than 850 hPa,large wind directional variance was merely found to the south of 25°N.The findings from long-term radiosonde measurements in winter over China shed light on the changes in wind speed on the ground and upper atmosphere under global warming from an observational perspective.

平衡流形成的机制与锋生(英文)

The final balanced state of an initial unbalanced flow is discussed with the same method as Vallis (1992). For the two-dimensional, inviscid, rotating and nonlinear model, the final state of the flow depends on the initial conditions. If the initial potential vortcity of the flow is non-uniform, the final state is not necessarily geostrophic. However, for the zero and uniform potential vorticity flow, the final state will satisfy the thermal wind relation when the length scale of the initial disturbance is large enough. Otherwise, discontinuity will occur in the geostrophic solution. In this case, the final balanced state will not be geostrophic any longer and an extended momentum coordinate is introduced to overcome the mult-value problem. Key words Frontogenesis - Geostrophic adjustment - Thermal wind balance - Extended momentum coordinates The work was supported by the National Natural Science Foundation of China (Grant Nos. 49735180 and 40075011) and the State Key Basic Program: CHERES.

Anomalous changes of temperature and ozone QBOs in 2015−2017 from radiosonde observation and MERRA-2 reanalysis

Anomalous changes of zonal wind quasi-biennial oscillation(QBO)in winter 2015−2016 have received close attention.Combining radiosonde and satellite observations and reanalysis data,we investigate anomalous changes in temperature and ozone QBOs from the lower to middle stratosphere.As wind shear direction is reversed due to unexpected changes of zonal wind QBO at about 24−30 km,the shortest cold phase at 21−27 km appears in temperature QBO.This is different from the completely interrupted westward phase in zonal wind QBO,while the longest cold phase above almost 27 km lasts for 2−3 years from 2015 to 2017,owing to the absence of corresponding warm phase.Meridional scale reduction of temperature QBO causes a small temperature anomaly,thus the thermal wind relationship looks seemingly different from that in the other regular QBO cycles.QBO in the ozone mixing ratio anomaly shows a double-peak with inverse phase,and its phase below(above)30 km is in agreement with(opposite to)the phase of temperature QBO because of different control mechanisms of ozone.Following temperature QBO variation,QBO in the ozone mixing ratio anomaly exhibits a less positive phase at 20−30 km in 2016−2017,and a very long positive phase above 30 km from 2015 to 2017.QBO in total column ozone shows a small peak in winter 2016−2017 since ozone is mainly concentrated at 20 to 30 km.Anomalous changes of temperature and ozone QBOs due to unexpected QBO zonal wind variation can be well-explained according to thermal wind balance and thermodynamic balance.