Plasma jet devices that use a helium gas flow mixed with a small percentage of argon have been shown to operate with a larger discharge current and enhanced production of the Ar(1s5) metastable state, particularly in the discharge afterglow. In this experiment, time-resolved quantitative measurements of He(23S1) and Ar(1s5) metastable species were combined with current and spectrally resolved emission measurements to elucidate the role of Penning ionization in a helium plasma jet with a variable argon admixture. The plasma jet was enclosed in a glass chamber through which a flowing nitrogen background was maintained at 600 Torr. At 3%–5% Ar admixture, we observed a ∼50% increase in the peak circuit current and streamer velocity relative to a pure helium plasma jet for the same applied voltage. The streamer initiation delay also decreased by ∼20%. Penning ionization of ground-state argon was found to be the dominant quenching pathway for He(23S1) up to 2% Ar and was directly correlated with a sharp increase in both the circuit current and afterglow production of Ar(1s5) for Ar admixtures up to 1%, but not necessarily with the streamer velocity, which increased more gradually with Ar concentration. Ar(1s5) was produced in the afterglow through recombination of Ar+ and dissociative recombination of Ar2+ as the local mean electron energy decreased in the plasma channel behind the streamer head. The discharge current and argon metastable enhancement are contingent on the rapid production of He(23S1) near the streamer head, >5×1012 cm−3 in 30 ns under the conditions of this experiment.
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The aim of current research work on micro air vehicles is to realize their autonomous control, i.e. building a library for a lookup table that would apply to micro electronics. In doing so, comprehensive flight tests need to be carried out. In this study, a four-wing flapping MAV is built and a multi-discipline approach is used to design the MAV model. Precision manufacturing technology is introduced here. The finished micro air vehicle has a weight of 8 g and is tested for flight by remote control. The micro air vehicle can perform both hovering and forward flight with high maneuverability. Forward flight is investigated first in this paper. Particle image velocimetry system is employed to examine unsteady aerodynamic performance in selected flight conditions. The study reveals that the micro air vehicle model will provide enough lift at a 30 angle of attack and flapping frequency of 12 Hz, which is consistent with real-life forward flight observations.
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