To simulate the transonic atomization jet process in Laval nozzles, to test the law of droplet atomization and distribution, to find a method of supersonic atomization for dust-removing nozzles, and to improve nozzle efficiency, the finite element method has been used in this study based on the COMSOL computational fluid dynamics module. The study results showed that the process cannot be realized alone under the two-dimensional axisymmetric, three-dimensional and three-dimensional symmetric models, but it can be calculated with the transformation dimension method, which uses the parameter equations generated from the two-dimensional axisymmetric flow field data of the three-dimensional model. The visualization of this complex process, which is difficult to measure and analyze experimentally, was realized in this study. The physical process, macro phenomena and particle distribution of supersonic atomization are analyzed in combination with this simulation. The rationality of the simulation was verified by experiments. A new method for the study of the atomization process and the exploration of its mechanism in a compressible transonic speed flow field based on the Laval nozzle has been provided, and a numerical platform for the study of supersonic atomization dust removal has been established.

To improve the trapping efficiency of respiratory dust by aerodynamic atomization, reduce the energy consumption and the requirements for the working conditions of nozzles and maintain the health and safety of workers, a comparative experiment evaluating aerodynamic atomization dust removal characteristics was conducted with a self-developed supersonic siphon atomization nozzle, which utilizes a Laval nozzle as the core, and an existing ultrasonic atomization nozzle. The experimental results showed that the new type of nozzle, from the perspectives of droplet speed, conservation of water and pressure, range, and attenuation view, completely surpasses the traditional pneumatic atomization nozzle. A supersonic antigravity siphon atomizer produces a cloud fog curtain composed of high-speed droplets and high-speed air. The particle size of the droplets is less than 10 µ. At the same flow rate of water, its dust removal rate is twice as high as that of ultrasonic nozzles. When the dust removal efficiency is the same, the water consumption of the supersonic siphon atomizer nozzle is 1/2, the air flow rate is 1/3, and the power consumption is 1/2 that of the ultrasonic atomizing nozzles. Siphon atomization can siphon at a total air pressure of 0.2 MPa, and the siphon pressure can reach 0.03 MPa at a total air pressure of 0.4 MPa, which increases with the increase in total inlet air pressure. For the first time, the process of siphoning and nozzle internal atomizing in the field of supersonic atomization dust removal is truly realized. The ultrafine sized droplets with high speeds produced by the new nozzle allow them to cover the limited working space in a shorter time, have a more effective trapping effect for a large number of fine dust particles, and quickly suppress the dust with greater kinetic energy. Therefore, the requirements for the working conditions are reduced, which will save more energy compared to the currently used nozzles available on the market.

Hermite–Gaussian beams, as a typical kind of higher-order mode laser beams, have attracted intensive attention because of their interesting properties and potential applications. In this paper, a full vector wave analysis of the higher-order Hermite–Gaussian beams upon reflection and refraction is reported. The explicit analytical expressions for the electric and magnetic field components of the reflected and refracted Hermite–Gaussian beams are derived with the aid of angular spectrum representation and vector potential in the Lorenz gauge. Based on the derived analytical expressions, local field distributions of higher-order Hermite–Gaussian beams reflection and refraction at a plane interface between air and BK7 glass are displayed and analyzed.

To effectively solve the problem of high dust concentration during coal cutting and frame shifting in fully mechanized mining faces, based on the theory of gas–solid two-phase flow, a geometric model of a fully mechanized mining face was established by using COMSOL numerical simulation software. Simulations were performed for the movement characteristics of wind flow and the law of dust diffusion. Results show that the air flow at the junction of the working face, the air inlet, the hydraulic support moving area, and the vicinity of the shearer has accelerated movement, and the maximum wind speed zone of about 3 m/s can be formed. Under the influence of wind flow, dust particles above 35 um settle faster, while dust particles below 35 um are very vulnerable to the influence of wind flow, and the settling speed is slower. Using a custom experimental platform, the atomization characteristics and wind resistance of a pressure fan nozzle, a supersonic nozzle, and an ultrasonic nozzle were tested, and the nozzle that was suitable for the scheme was selected and applied in the field. Comparing the dust concentration before and after the application of the dust removal scheme at the sampling point, results show that the dust removal efficiency of the proposed scheme exceeds 85%, and the treatment effect is good.

This paper discusses the observer-based H ∞ control problem for semi-Markov jump systems (S-MJSs) with generally uncertain transition rates (TRs) and input saturation, where the S-MJSs also consider H 2 -norm bounded disturbances and exosystem generated disturbances. First, the sufficient conditions for the local stochastic stability of the closed-loop system are given. Then, a full-order observer is designed to observe both the system state and external disturbance. Based on its estimated values, the composite controller is constructed to guarantee the system performance, and solvability conditions are proposed to ensure the closed-loop system to be the local stochastic stability with H ∞ performance level. Further, the maximum estimation of the attraction domain is given by an optimization problem. Finally, the effectiveness of the proposed method is verified by numerical example.