In this study, the magnetic properties, coercivity mechanism, and magnetization reversal process were investigated for Ce-(Y)-Pr-Fe-B films. After the addition of Y and subsequent heating treatment, the formations of REO (RE ≡ Ce and Pr) and REFe2 (RE ≡ rare earths) phases are inhibited, and the microstructure of Ce-Y-Pr-Fe-B film is optimized. Meanwhile, the coercivity and the squareness of the hysteresis loop are significantly improved. The coercivity mechanism of Ce-Y-Pr-Fe-B film is determined to be a mixture of nucleation and pinning mechanisms, but dominated by the nucleation mechanism. The demagnetization results show that the nucleation of reversal magnetic domains leads to irreversible reversal. Our results are helpful to understand the coercivity mechanism and magnetization reversal of permanent magnetic films with multi-main phases.
This paper aims to disclose the exact effects of various factors on the motion of ultrasonic cavitation bubble. For this purpose, this paper modifies the cavitation bubble dynamics model in light of liquid compressibility, liquid viscosity, water evaporation and vapor condensation. Based on the model, a dynamic equation was created for the bubble, and applied for Matlab simulation of bubble motion. The bubble motion was characterized by such parameters as radius, temperature, pressure, internal energy and the number of vapor molecules. The simulation attempts to reveal how the bubble motion is affected by the initial bubble radius, the ultrasonic frequency and the ultrasonic amplitude. Through the simulation, it is discovered that the change of the initial radius had a little impact on the bubble temperature and bubble pressure. However, the radius variation exerted an obvious influence on the other motion parameters. These parameters shared a similar change pattern. For ultrasonic frequency, the change in frequency had a limited effect on the bubble temperature and bubble pressure, but a significant impact on the other motion parameters. These parameters varied in different ranges. In addition, the ultrasonic amplitude had a rather prominent impact on all motion parameters of the cavitation bubble. The research findings provide important insight into the dynamic features of ultrasonic cavitation under ultrasonic waves.
As the fundamental research work of solid particle motion in the two-phase flow of solid-liquid or gas-liquid in the rotating state, based on the tapered drum rotating type separator and medium of water, the dynamic model of particle motion in the rotating flow filled was set up. Simultaneously, the visualization experiment of particle motion was carried out by the high speed camera and compared with the calculation results. In setting up of dynamic model, besides of forces of gravity, buoyancy, drag force and centrifugal force, the forces of imagination mass force, Basset force, Saffman lift force and pressure gradient force were considered. In the calculation, angle of taper, velocity of down flow and particle size were considered. It is found that the length of drum, angle of taper, down flow speed, rotating speed of drum and particle size had influence on the separating time and the length of particle movement traces. The results were proved by the visualization experiment, and further correctness of dynamic model was validated.
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