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In this study, a modified phenomenological model has been proposed by merging the Suzen-Huang model and the Yoon-Han thrust model for two types of single plasma actuators and plasma synthetic jet actuators, in different geometries and different working and environmental conditions. The model introduced in the present work is based on the thrust induced by plasma. With this generalization and modification, this model overcomes the drawbacks of the standard Suzen-Huang model, i.e., lack of correct estimation of the nonlinear relationship between the applied voltage and the amount of thrust induced by the plasma and not considering the influence of parameters such as the thickness of dielectric and dielectric constant, the thickness of the exposed electrode, and the alternating current frequency). Applying this model on a single plasma actuator shows the accuracy and correctness of this model. Also, by generalizing the present model for the annular plasma synthetic jet actuators, the dependence of the maximum charge density and body force on the diameter of the actuator was included in the model. Validation of the present model for the annular plasma synthetic jet actuator shows that the model is able to adapt itself well to changing the diameter of the actuator, working conditions, geometry and materials of the actuator and make a good estimate of the results. [ABSTRACT FROM AUTHOR]

In this work, plasma has been used as a simple, very fast, low energy and efficient method for modification of the zinc oxide nanopowder to improve its photocatalytic activity. Zinc oxide is one of the effective photocatalysts in degradation of the organic contaminants, e.g. dyes. The purpose of the zinc oxide photocatalyst modification is to reduce the band gap and thus to increase its photocatalytic activity in the visible light range. To achieve nitrogen-doped zinc oxide nanoparticles (N-Doped ZnO), the zinc oxide nanopowder was suspended in melamine solution, as nitrogen precursor, and then treated with a non-thermal atmospheric pressure plasma. Different concentrations of melamine and different times of plasma exposure were considered for optimizing the nitrogen-doped zinc oxide structure. The photocatalyst properties of the pure zinc oxide and optimized nitrogen-doped zinc oxide samples were investigated by XRD, FESEM, EDX, BET, DRS and PL analyses. The photocatalytic activity of the pure zinc oxide nanopowder and plasma-treated samples were performed in the photocatalytic degradation of methylene blue dye contaminant. The degradation efficiency of methylene blue by the pure zinc oxide was 71.7%. By applying plasma to the zinc oxide nanopowder for 5 minutes with a concentration of 500 mg/L of melamine solution, the degradation efficiency was enhanced to 90%. According to the results, it can be seen that the plasma treatment has succeeded in the nitrogen doping process to the zinc oxide structure and improved its photocatalytic activity.

In this study, a cold atmospheric He plasma jet is investigated. The jet is of dielectric barrier discharge type, consisting of a dielectric tube with two metal ring electrodes. The continuity, momentum and energy conservation equations as well as the Poisson equation for obtaining the potential and the electric field, accompanied with the ideal gas laws, are used for the simulation. The results show that the electron and ion densities, potential and space charge field, internal energy, temperature and velocity of the electrons increase with time. Moreover, the increment of the plasma length and its forward propagation along the jet axis with time is also observed. Therefore, it is expected that the values of the mentioned quantities increase with time, which results in the increment of the plasma jet length.

Nowadays, cold atmospheric pressure plasmas are used as an efficient method in food industries. The advantage of plasma method compared to other method are high productivity, cost-effectiveness and reduction of harmful chemical pollutants. In this study, cold atmospheric pressure dielectric barrier discharge plasma in surface and volumetric treatment mode was produced, and its effect on the physical and chemical properties of saffron was investigated. For this purpose, after the production and characterization of plasma structures including electrode structure, electrical properties and optical emission spectroscopy, the influence of these structures on the physical and chemical properties of saffron was investigated. At first, the effect of surface and volumetric plasma treatment on degradation of Escherichia coli bacteria was investigated. The results showed that surface dielectric barrier discharge plasma treatment with high treatment time has a great effect on inactivation of Escherichia coli. Then, the effect of surface and volume treatments on the main properties of saffron including crocin, picrocrocin and safranal were investigated. The results showed that surface and volumetric plasma treatment increase the main properties of saffron,surprisingly. Finally, the effect of surface and volumetric plasma treatments on increasing harmful substance in saffron including nitrate and ammonium was investigated. The results showed that volumetric treatment of plasma due to direct processing increase the harmful substances in saffron, including nitrate and ammonium. According to the results of this research, it can be concluded that the dielectric barrier discharge in surface treatment mode has advantages against volumetric treatment. The latter suffers from harmful by-products. In this regard, the surface treatment of saffron is preferable to volumetric. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is one of the most important pathogenic bacteria in the dairy products industry that is capable of biofilm formation. Biofilm formation by these bacteria has been led to resistance to antimicrobial agents. Inactivation of microorganisms using cold atmospheric plasma is one of the new approaches in the food industry. In this study, to evaluate the antibacterial and anti-biofilm effect of cold atmospheric plasma, a dielectric barrier discharge system was used. Twenty isolates of S. aureus from clinical bovine mastitis milk were exposed to plasma from 5 to 20 Sec and their antibacterial activity was estimated by recording the growth zone of inhibition. Plasma treatment was performed punctually for 5 Sec to assess the possible effects of plasma treatment on bacterial biofilm-formation activity after 24 h. The results show that a remarkable reduction in the growth of bacteria by increasing the flow of plasma. Moreover, statistical analysis of the ELISA reader results showed that the exposure of the isolates to plasma, significantly (p < 0.05) reduced the biofilm formation. These results suggest that plasma can be a suitable alternative method for thermal sterilization techniques. However, its application requires further studies to determine the severity and duration of exposure of microorganisms to plasma.

In this work, we investigated generating argon cold plasma jet at atmospheric pressure based on dielectric barrier discharge configuration using three electrical power supplies of sinusoidal, pulsed and saw tooth high voltage shapes at 8 KHZ. At first; we describe the electronic circuit features for generating high voltage (HV) wave forms including saw tooth, sinusoidal and pulsed forms. Then, we consider the effect of voltage shape on the electrical breakdown. Relative concentrations of chemical reactive species such as Oxygen, atomic Nitrogen and OH were measured using optical emission spectroscopy. Using a simple numerical model, we showed a HV with less rise time increases electron density, therefore a cold plasma jet can be produced with a minimal consumption electrical power