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We are concerned with the uniform regularity estimates and vanishing viscosity limit of solution to two dimensional viscous compressible magnetohydrodynamics (MHD) equations with transverse background magnetic field. When the magnetic field is assumed to be transverse to the boundary and the tangential component of magnetic field satisfies zero Neumann boundary condition, even though the velocity is imposed the no-slip boundary condition, the uniform regularity estimates of solution and its derivatives still can be achieved in suitable conormal Sobolev spaces in the half plane $\mathbb{R}^2_+$, and then the vanishing viscosity limit is justified in $L^\infty$ sense based on these uniform regularity estimates and some compactness arguments. At the same time, together with \cite{CLX21}, our results show that the transverse background magnetic field can prevent the strong boundary layer from occurring for compressible magnetohydrodynamics whether there is magnetic diffusion or not., Comment: 33 pages. arXiv admin note: text overlap with arXiv:2108.12969

Vertical cambered V-type otter boards are widely used in large and medium-sized trawlers for their good stability and adaptability to various water layers. However, limited numerical studies on the hydrodynamic performance and structural strength of this type of otter board have been published. In this study, we established the three-dimensional numerical model of the double-slotted vertical cambered V-type otter board according to its special structure and stress feature. We compare the hydrodynamic performance results of our model with those of previous experiments. Using this model, we analyzed the influence of parameters such as attack angle, aspect ratio, dihedral, and deflector angles on its hydrodynamic performance. Moreover, the structural response characteristics of the otter board under typical working conditions were studied. We believe our results will provide theoretical reference for the structural design and optimization of the vertical cambered V-type otter board.

Additional file 1: Figure S1. Rarefaction analysis of sampling by observed bacterial.

In the conversion coatings, some uniformly distributed micro surface cracks always occur but the surface cracks behavior is rarely studied due to the frequent initiation in the real test conditions. In this work, computer simulation of micro surface cracks behavior and internal stresses generated in the anhydrous chemical conversion coating was carried out using the finite element method with the help of ABAQUS software. The Mises stress distribution, S11 stress variation, and the stress-time curves were obtained. The results show that the internal stresses generated in the conversion coating increase obviously with increasing time, and the stresses at the center and boundary of coating pieces are bigger than the ones in other areas while the S11 stresses around the center are bigger than the ones near the boundary. The cracks at the interface of coating pieces develop gradually and are as V-type cracks finally. The width of crack mouth opened is different since the contraction degree of each coating piece is different.

In this paper, we consider the nonlinear inhomogeneous compressible elastic waves in three spatial dimensions when the density is a small disturbance around a constant state. In homogeneous case, the almost global existence was established by Klainerman-Sideris [1996_CPAM], and global existence was built by Agemi [2000_Invent. Math.] and Sideris [1996_Invent. Math., 2000_Ann. Math.] independently. Here we establish the corresponding almost global and global existence theory in the inhomogeneous case.

This paper investigates the erosion performance of electro-thermal explosion directional spraying (EEDS) cermet WC/Co coatings using an air solid particle erosion rig. The influences of the different parameters such as impact angle, impingement velocity, environment temperature, particle diameter, on the erosion property of the coatings were studied. The eroded surfaces were examined by scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS) and the erosion mechanisms were discussed. The structure and bond characters of the coatings were also determined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and SEM. The results indicate that the EEDS WC/Co coatings are characterized by fine grain structure, good metallurgical bond and brittle erosion character. The erosion rates of the coatings decrease with temperature increasing and increase with impact angle and impingement velocity increasing. At elevated temperature, the oxidation happens on the coatings surface, which affects the erosion behavior.

Failure may occur catastrophically by fracture along grain boundaries when temper embrittlement induced by non-equilibrium, grain-boundary segregation (NGS) of phosphorus atoms. Temper embrittlement control technique based on the theory of NGS and deformation induced phase transformation in low-alloy steel, 12CrlMoV (which is used in steam pipeline of ships), was experimentally investigated. A single-pass hot rolling process by using a Gleeble-1500 system was performed, and the experimental results showed that the grain sizes were obviously affected by the deforming temperature, strains, strain rate and the quenching cooling rate. Temper embrittlement may be controlled and obviously improved by grain refinement.