Search

This paper focuses on the 2D incompressible anisotropic magneto-micropolar fluid equations with vertical dissipation, horizontal magnetic diffusion, and horizontal vortex viscosity. The goal is to investigate the stability of perturbations near a background magnetic field in the 2D magneto-micropolar fluid equations. Two main results are obtained. The first result is based on the linear system. Global existence for any large initial data and asymptotic linear stability are established. The second result explores stability for the nonlinear system. It is proven that if the initial data are sufficiently small, then the solution for some perturbations near a background magnetic field remains small. Additionally, the long-time behaviour of the solution is presented. The most challenging terms in the proof are the linear terms in the velocity equation and the micro-rotation equation that will grow with respect to time t. We are able to find some background fields to control the growth of the linear terms. Our results reveal that some background fields can stabilise electrically conducting fluids. [ABSTRACT FROM AUTHOR]

Methane (CH4) gas sensors play an important role in industrial safety and detection of indoor gas quality. In general, metal oxide semiconductor sensing materials with nano-structure have high responses to the target gas. However, the sensor resistance is usually very high. Considering the practical application, it is vital to reduce base resistance and improve sensitivity for gas sensors. Herein, Pd-doped SnO2 nanoparticles were prepared as the basis material by a simple sol-gel method. In order to adjust the resistance, the pentavalent metal element (Sb) was introduced via a simple doping route. As CH4 sensing layers, the prepared SnO2-sensors doped with Pd and Sb exhibited the most obvious resistance reduction effect. Meantime, excellent sensing performances including high response, fast response/recovery time, excellent reproducibility and great stability were also obtained. In-depth research has shown that the ability to reduce resistance depends on the effective internal doping of cation with high valence. The enhanced sensing capability can be attributed to the 'synergistic effects' including catalytic effects of novel metals, increased oxygen vacancies and decreased band gap energy. This work can provide a new opportunity to design metal oxide sensing materials with low resistance and high sensitivity. [ABSTRACT FROM AUTHOR]

Currently, the self-shadowing effect of impinging particles is recognized as a vital factor to form columnar-like coating in the manufacture of thermal barrier coatings. Most of these quasi-columnar coatings are usually prepared under a very low-pressure condition. This paper investigates a novel quasi-columnar yttria stabilized zirconia (YSZ) coating using an atmospheric plasma spray-physical vapor deposition method. The microstructures of the coating present a quasi-columnar structure that is distributed along the cross-section of the coating within certain intervals with a large number of cluster-like structures on the top surface of the coating. A lower particle velocity that contributes to the generation of a mass of vapor YSZ materials is studied via experimental and numerical analyses and these results are compared with other current plasma spray methods. The mechanism of the self-shadowing effect from impinging particles that leads to the formation of a quasi-columnar feature at the boundary layer of the substrate is demonstrated by a three-dimensional numerical simulation and experimental observation. Furthermore, the hybrid growth model of the vapor and droplet co-deposited coating is clarified in this paper. [ABSTRACT FROM AUTHOR]

A microwave-assisted hydrothermal approach with a follow up thermal treatment was employed to prepare 1D porous CoO nanowires, which is constructed by numerous high crystallinity nanoparticles. A significant change in crystal structure of the precursor were observed, as position shift and absence of some diffraction peaks, which was induced by the microwave-assistance during hydrothermal process. Moreover, the precursor's purity was also effectively improved. As a result, the as-synthesized CoO annealed from the microwave-assisted precursor exhibited a morphology and phase structure significantly different from that of without microwave involvement. Benefiting from the 'microwave effect', the microwave-assisted as-fabricated porous CoO nanowires showed an enhanced specific capacitance (728.8 versus 503.7 Fg−1 at 1 A g−1), strengthened rate performance (70.0% versus 53.2% maintenance at 15 A g−1), reduced charge transfer resistance (1.06 Ω versus 2.39 Ω), enlarged window voltage (0.85 versus 0.7 V) and enhanced cycle performance (82.3% versus 76.5% retention after 5000 cycles at 15 A g−1), compared with that of sample without microwave assistance. In addition, the corresponding electrochemical properties are also higher than those reported CoO sample prepared by solvothermal method. In conclusion, this work provides a practical way for enhancing electrochemical properties of supercapacitor materials through adjusting the precursor by microwave assistance into hydrothermal process. [ABSTRACT FROM AUTHOR]

Unconventional superconductivity, in particular, in noncentrosymmetric systems, has been a long-sought topic in condensed matter physics. Recently, Re-based superconductors have attracted great attention owing to the potential time-reversal symmetry breaking in their superconducting states. We report the superconducting properties of noncentrosymmetric compounds TaxRe1 – x with 0.1 ≤ x ≤ 0.25, and find that the superconducting transition temperature reaches a maximum of ∼8 K at the optimal level x = 0.15. Nevertheless, muon-spin rotation and relaxation measurements reveal no time-reversal symmetry breaking existing in its superconducting state, which is in sharp contrast to both centrosymmetric Re metal and many other noncentrosymmetric Re-based superconductors. [ABSTRACT FROM AUTHOR]