## 2 Results
### Vortex Breakdown Control by the Plasma Swirl Injector  
[PERSON] et al. in [3] proposed and tested the concept of using the plasma swirler to control vortex breakdown. The presented plasma swirler with a helical shape was adopted to control the vortex breakdown. The plasma swirler with the electrode placed in the streamwise direction was designed by the authors. The plasma actuation, in affecting the onset and development of the vortex breakdown was captured and analyzed using particle image velocimetry (PIV) technique. The flow field measurement demonstrated that the plasma actuation was effective in controlling the development of vortex. The authors conclude that the method being proposed here may represent an attractive way of controlling vortex breakdown using a small amount of energy input without a moving or intrusive part, and the plasma actuation offers great flexibility in flow and combustion control.  
Influence of Ag Electrodes Asymmetry Arrangement on Their Erosion Wear and Nanoparticle Synthesis in Spark Discharge  
[PERSON] et al. in [4] investigated the effect of the asymmetry arrangement of Ag electrodes on them erosive wear and presented the synthesis of nanoparticles (NPs) during a spark discharge. The two types of discharge current pulses were studied: oscillation-damped, in which the electrodes changed their polarities during a single discharge, and unipolar, in which the electrodes had a given polarity during the discharge. The used electrodes in the form of rods, one of which had a gas supply hole, were installed coaxially. The authors demonstrated that it is possible to control the size and concentration of synthesized nanoparticles by changing the degree of the electrodes asymmetry by setting their end faces at a certain angle. With an increase in the degree of the electrodes asymmetry, larger nanoparticles (with sizes greater than 40 nm) appeared in the aerosol composition and their agglomeration increased. The results presented in this article can help spark discharge users to optimize the placement of discharge electrodes.  
Impact of the Samples Surface State on the Glow Discharge Stability in the Metals Treatment and Welding Processes  
[PERSON] et al. in [5] presented the results of a study of the effect of sample surface condition on the stability of glow discharge in metalworking and welding processes. The main objective of this study was to investigate the effect of cathode macro and micro relief on the existence of stable glow discharge in metalworking and diffusion welding processes. It was determined analytically and supported experimentally that the stability of the glow discharge is mainly affected by the generated sharp protrusions on the cathode surface due to the pretreatment of the samples by machining before welding. It was found that the increasing the cathode surface roughness from 10-15 \(\upmu\)m to 60-80 \(\upmu\)m led to the rapid decreasing the region of the limiting pressure of the stable glow discharge from 1.33-13.3 kPa to 1.33-5.3 kPa. The results presented in this article may be helpful for glow discharge researchers to optimize the working gas pressure and surface roughness of discharge electrodes.