Steering Multiple Reverse Current into Unidirectional Current in Deterministic Ratchets

Recent investigations have shown that with varying the amplitude of the external force, the deterministic ratchets exhibit multiple current reversals, which are undesirable in certain circumstances. To control the multiple reverse current to unidirectional current, an adaptive control law is presented inspired from the relation between multiple reversaJs current and the chaos-periodic/quasiperiodic transition of the transport velocity. The designed controller can stabilize the transport velocity of ratchets to steady state and suppress any chaos-periodic/quasiperiodic transition, namely, the stable transport in ratchets is achieved, which makes the current sign unchanged.

Pre-breakdown to stable phase and origin of multiple current pulses in argon dielectric barrier discharge

We report on the results of numerical models of the(i)initial growth and(ii)steady state phases of atmospheric-pressure homogeneous dielectric barrier discharge in argon.We employ our new inhouse code called Py DBD,which solves continuity equations for both particles and energy,shows exceptional stability,is accelerated by adaptive time stepping and is openly available to the scientific community.Modeling argon plasma is numerically challenging due to the lower speeds of more inertial ions compared to more commonly modeled neon and helium,but its common use for plasma jets in medicine makes its modeling compelling.Py DBD is here applied to modeling two setups:(i)the exponential growth from natural electron-ion seeds(onset phase)until saturation is reached and(ii)the multiple current pulses that naturally appear during the steady state phase.We find that the time required for the onset phase,when the plasma density grows from 10^(9)m^(-3)to 10^(17)m^(-3),varies from 80μs at 4.5 k V down to a fewμs above 6.5 k V,for voltage frequency f=80 k Hz and gap width d_(g)=0.9 mm.At the steady state,our model reproduces two previously observed features of the current in dielectric barrier discharge reactors:(1)an oscillatory behavior associated to the capacitative character of the circuit and(2)several(N_(p))current pulses occurring every half sinusoidal cycle.We show that the oscillations are present during the exponential growth,while current pulses appear approaching the steady state.After each micro-discharge,the gas voltage decreases abruptly and charged particles rapidly accumulate at the dielectric boundaries,causing avalanches of charged particles near the reactor boundaries.Finally,we run a parametric study finding that N_(p)increases linearly with voltage amplitude V_(amp),is inversely proportional to dielectric gap d_(g)and decreases when voltage frequency f increases.The code developed for this publication is freely available at the address https://github.com/gabersyd/PyDBD.

多次雷电冲击对氧化锌避雷器阀片性能的影响(英文)

A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester installed to the transformer,when a lightning strike happens,it may receive a very high lightning overvoltage,which is certainly resulted in the transformer damage at its insulation.Usually,a lightning arrester specification data attached to a lightning arrester contains the rating data of the lightning arrester current and voltage.In the use of lightning arrester,the possibility of receiving multiple lightning strikes is not taken into account sometimes.In fact,in some places,the number of multiple strikes in short duration is quiet high in number.This condition makes the lightning arrester being stroked by multiple lightning strikes.Therefore,it may change the lightning arrester's properties,and then the arrester may not be able to provide good electrical equipment protection against lightning strike anymore.This condition will result in great loss to electrical companies and electrical consumers.Therefore,this research studied the effect of applying multiple lightning strikes to ZnO lightning arrester block.Every time a group of lightning impulse current is applied to the ZnO lightning arrester block,it is followed by the measuring of its 50 Hz voltage and current characteristic. The changing in the ZnO lightning arrester block 50 Hz characteristic then can be analyzed.It was found that by applying more numbers of lightning strikes which made the arrester becoming worse,even though,actually,the lightning impulse peak current was still under the rating of the lightning arrester current.In this case for a 5 kA,24 kV lightning arrester,even though the lightning impulse peak current flowing through the ZnO lightning arrester block was still 2500 A,the lightning arrester ZnO block had already been damaged.Having been damaged,an alternating current flowing through the damaged ZnO block was about 10000 times as much current flowing to the good one.The maximum of impulse energy absorbed by a ZnO block recorded was 334.7 J/cm^3.The damaged ZnO block should be replaced by a good one.