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The structure of a muzzle brake has a significant effect on the overall technical performance of an automatic weapon. This paper presents a multi-objective optimization of a muzzle brake that enhances the overall performance, that is, it increases the muzzle brake efficiency and simultaneously decreases the noise emanating from the rifle upon discharge. A standard impact-reaction muzzle brake was selected as the research object. The optimal values of four structural parameters were established through multi-objective optimization. The process consists of design of experiments, coupled computational fluid dynamics and computational acoustics calculations, an approximation model, and a multi-objective genetic algorithm. Based on the results, the correlation and sensitivity between the structural parameters and the objectives were investigated. Moreover, the reaction force and noise directivity of the optimized muzzle brake were compared with those of the original design. The results show that the disk angle of the side holes was the most sensitive design variable for both efficiency and noise. The optimized muzzle brake had a remarkable improvement in brake efficiency accompanied by only a small increase in the sound pressure level, so it showed better overall performance. The optimization method proposed in this paper is practical and effective for engineering design. [ABSTRACT FROM AUTHOR]

Plasma-activated solution (PAS) has attracted wide attention in cancer treatment because it can treat deep tumors and offer storability. The changes in reactive species and physicochemical properties of PAS during storage can affect its anticancer effect. In this study, the plasma-activated medium (PAM) was prepared by treating RPMI 1640 medium with afterglow gas generated by a custom-built air surface dielectric barrier discharge device. PAM was stored at four common temperature conditions (25 °C, 4 °C, −20 °C, and −80 °C) for 1 day, 4 days, and 7 days, and then, the physicochemical properties, reactive oxygen and nitrogen species (RONS), and the anti-cancer effect on A549 cells under different storage conditions were compared. The results showed that PAM exhibited different anticancer effects at different storage temperatures over a 7 day storage period. The anticancer ability of PAM under 80 °C storage remained stable after 7 days of storage and decreased at all other temperatures. These results were also verified by apoptosis results, and the differences were mainly related to the concentration of H2O2 and NO2−, and oxido reduction potential. Our results provided a theoretical basis for the storage of PAM and its application in anticancer therapy. [ABSTRACT FROM AUTHOR]

The presence of bacteria and viruses in water has caused many large-scale water disease outbreaks. Cold atmospheric plasma has received much attention as an emerging non-thermal purification technology capable of eliminating micro-organisms, non-ferrous fuels, and heavy metals from water. In this study, a novel gas–liquid diaphragm discharge device that generates air plasma driven by a sinusoidal AC power supply was designed, and its sterilizing effect was investigated. First, the concentrations of reactive oxygen and nitrogen species in the diaphragm discharge were characterized, and the physicochemical properties of activated water were explored. Next, experiments on the inactivation of Pseudomonas aeruginosa were carried out using the device. Finally, pond sewage was treated with the device, and the diversity of micro-organisms in the water was analyzed using 16S rRNA assays to further investigate its applicability. The results showed that the species and quantities of micro-organisms in the water significantly reduced after discharge treatment, with the most significant changes occurring in the Bacillus and Firmicutes species. Thus, this study provides an alternative method for microbial inactivation in sewage treatment. [ABSTRACT FROM AUTHOR]

Atmospheric pressure cold plasmas are widely used in the biomedical field as evidenced by developments in recent years. In this study, a quartz tube-guided gas–liquid two-phase discharge has been configured with a hollow needle-water structure. The power source for the device was sinusoidal, and switching between a gas–liquid miscible discharge and a pure gaseous discharge was simple. It was discovered that the gas–liquid discharge was beneficial in terms of reactant species generation and reaction efficiency in terms of processing water. The types of particles, the physicochemical properties, and the concentrations of reactive oxygen and nitrogen species in the discharge were studied spectroscopically. The discharge was discovered to have high levels of H2O2 and NO2−, and the activated water was proven to be effective at sterilizing samples that were contaminated with micro-organisms. Key experimental parameters including the driving voltage and the air flow rate were optimized to achieve the best sterilization conditions. The membrane potential changes in the treated bacteria were also studied to explore the causes of bacterial inactivation. The results showed that the device exhibited a strong bactericidal effect for the gas–liquid mixed phase discharge operating at 17 kV for 5 min with a gas flow rate of 0.3 SLM. In addition, the present device offers enhanced sterilization efficiency relative to the efficiency of conventional plasma sterilization equipment and, therefore, has a wide range of applications. [ABSTRACT FROM AUTHOR]

In the field of plasma biomedicine, research on a plasma-activated medium (PAM) has attracted increasing attention in recent years because of its excellent characteristics. In this study, we used an atmospheric pressure air plasma jet to treat four different solutions: de-ionized water, RPMI 1640 medium, phosphate buffered saline (PBS), and saline. In order to investigate the property differences of different PAM, we mainly analyzed the physical and chemical properties and liquid-phase active species of different PAM and evaluated the inactivation of A549 lung cancer cells. The results show that the concentrations of long-lived reactive species (H2O2, NO2−, and NO3−) in different PAM increased with increasing treatment time. Biological experiments showed that the antitumor effects were in the order of PBS > saline > RPMI 1640 medium, and the best inactivation effect of plasma-activated PBS for 12 min was 89%. Meanwhile, plasma-activated PBS effectively promoted apoptosis in A549 cells, and the highest apoptosis rate was 91.3%. Therefore, this study demonstrates the medical application of different PAM in killing cancer cells and promotes the understanding of plasma–liquid interaction. [ABSTRACT FROM AUTHOR]