The microwave plasma torch (MPT) is an attractive plasma source in both industry and scientific research because of its advantages in electrodeless operation ability, high energy efficiency, and flexibility under different operational conditions. However, relatively few numerical studies have been carried out for the MPT fed by a rectangular waveguide in two or even three dimensions. Therefore, this paper presents a 2-D, axisymmetric, and stationary fluid models to characterize the MPT, with an emphasis on the mechanism of the surface wave formation and the sustentation of the plasma column. Nine partial differential equations are included in this research, coupling microwave radiation, heat transfer, plasma bulk flow, and transport of different species with each other. The obtained results reveal how the traveling surface wave occurs and elucidate the consequent influence of the surface wave formation. Furthermore, this paper demonstrates the extension of the plasma column length and the propagation of the surface wave with an increase in the total plasma-absorbed microwave power. The dependence of the plasma column length on the plasma-absorbed microwave power is found to be motivated by the surface wave propagation. The limitations of the model and the difficulties in its numerical implementation are also discussed in the paper.

A 2450-MHz microwave-induced room-temperature atmospheric-pressure plasma jet (RTAPPJ) based on a coaxial structure is proposed for applications of plasma biomedicine. This device is a simple structure with small size, low-power requirement and high controllability. It can induce an argon discharge at atmospheric pressure with as low as 15-W microwave power. The optical emission spectrum of the RTAPPJ shows various highly reactive radicals such as OH and O. The appropriate operation condition can reduce the temperature at the downstream of the flame to be around 30 °C. This portable device is designed to be suitable to manipulate different medical treatments.

For the discharges sustained by the travelling electromagnetic waves, the wave propagation characteristics are of great importance to discharge maintenance and stability. This study aims to investigate the propagating electromagnetic modes of the travelling wave in a cylindrical discharge tube bound by a metallic enclosure based on a microwave plasma torch. In certain particular circumstances, it is found that the cylindrical discharge tube with metallic enclosure is able to change from a one-conductor circular waveguide to a two-conductor-like coaxial waveguide. Such a change allows the travelling wave to propagate in the transverse electromagnetic mode, which has rarely been noticed before. Regarding this transition, a new criterion is proposed to determine the formation of the two-conductor-like waveguide structure. Existence conditions of different propagating modes of the travelling wave are further discussed with respect to different glass tube wall thicknesses and dielectric properties. The results indicate that it is possible to control the propagating modes of the travelling wave for different purposes by choosing a proper glass tube.

A 60-day feeding trial was conducted to investigate the effect of enzymatic hydrolysis chicken by-product (EHC) supplementation in high plant protein diets on growth performance, digestive capacity, antioxidant capacity and non-specific immunity of juvenile turbot (Scophthalmus maximus L.). The diet with 620 g/kg fish meal (FM) was used as the positive control group (FM group), while the diet with 372 g/kg FM and 256 g/kg degossypolled cottonseed protein were used as the negative control group (0 g/kg EHC group). Based on the negative control diet, grade levels of EHC (10, 20, 30 and 40 g/kg) were added, respectively. Results showed that fish fed with a high plant protein diet showed significantly lower growth performance, digestive capacity, antioxidant capacity and non-specific immunity than those of the positive control. The supplementation of 20 g/kg EHC significantly increased growth performance of fish as compared to the negative control. Furthermore, the digestive capacity of turbot fed the diet with 20 g/kg EHC was significantly improved by increasing activities of trypsin, pepsin and lipase and the expression of peptide transporter 1 (pept1). The antioxidant capacity and non-specific immunity of fish fed the diet with 20, 30 and 40 g/kg EHC were significantly improved by increasing activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (T-AOC), lysozyme (LZM) and acid phosphatase (ACP) in serum, decreasing the expression of interleukin-1β (il-1β) and tumour necrosis factor-α (tnf-α) and increasing the expression of transforming growth factor-β (tgf-β). In conclusion, the adverse effect of high plant protein diet on growth performance of turbot could be improved with the supplementation of 20 g/kg EHC, which could be due to the positive effect of EHC on digestive capacity, antioxidant capacity and non-specific immunity of juvenile turbot.