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• Four cavities of different depths were evaluated to determine the cavity induced transition after the cavity. • The shallowest cavity is a "closed" cavity, inducing the widest transition, caused by the strong adverse pressure gradient and horseshoe vortex instability. • The other three deeper cavities are all "open" cavities. • Medium depth cavity did not induce transition. • The two deepest cavities induced a narrower transition, caused by shear layer instability. Cavity-induced transition (CIT) in a hypersonic boundary layer was simulated by employing direct numerical simulation (DNS). The upwind Roe scheme was discretized by high-order minimum dispersion and controllable dissipation (MDCD) reconstruction based on high-quality multi-block structured grids. The grid scale and time step are determined after evaluating the grid scale and nondimensional time step and comparing with the available measurements. Four depths, 1.0, 1.5, 2.0, and 2.5, multiplied by the baseline depth (D), are evaluated to determine their effects on the CIT on the wall after the cavity. The baseline is a typically "closed" cavity and the width of turbulent region at one cavity length downstream cavity (x = 2 L) is 67 mm, caused by the strong adverse pressure gradient and horseshoe vortex instability. Typically, the other three are "open" cavities with no transition for the 1.5 D cavity, a turbulent region width of 26 mm for the 2.0 D cavity, and 45 mm for the 2.5 D cavity at x = 2 L were obtained after the cavity. Moreover, the relationship between the flow structures and a typical high heat flux region is explored. Reattachment supplies heat to the wall, and separation removes heat from the wall. [ABSTRACT FROM AUTHOR]

• The diffuse scattering field is analyzed in detail in conventional X-ray transmission imaging systems. • A flexible algorithm is proposed for numerically reconstructing the scattering-disturbed X-ray photographs. • The numerically reconstructed X-ray photographs are demonstrated of high accordance with the experimentally ones. In high-energy X-ray radiography, the unpredictable photon scattering from the imaging system invariably disturbs imaging quality. Scattering-induced distortions in X-ray photographs need to be numerically compensated through image processing algorithms for accurate reconstruction. This paper proposes a numerical method for eliminating diffuse scattering, prevalent in common X-ray transmission imaging systems. Experiments are conducted to validate the effectiveness of the proposed image-processing algorithm. Results demonstrate that the numerically reconstructed X-ray photographs align well with the diffuse scattering-free ones, facilitating versatile applications of the algorithm in high-energy particle radiography. [ABSTRACT FROM AUTHOR]

• Pitting corrosion of SLM 316L SS in different aggressive solutions was studied. • A model was built to explain the pitting mechanism induced by gas-pore. • Metastable pitting at covered gas-pores is more likely to transition into stable. In this study, the pitting behaviors of wrought and SLM 316L SSs (stainless steels) are comparatively investigated under the conditions of different aggressiveness. The experimental results show that SLM 316L SS exhibits higher sensitivity to pitting corrosion in extremely aggressive solutions, while the wrought sample is more vulnerable to pitting in conditions with low aggressiveness. Gas pores are the pitting-sensitive sites in SLM 316L SS, and metastable pits initiated at covered gas pores are easier to evolve to stable growth compared to open pores due to the greater diffusion resistance. [ABSTRACT FROM AUTHOR]

Electrochemical hydrogen production from water splitting is one of the effective methods for hydrogen production that has recently attracted particular attention. One of the limitations of the electrochemical water splitting method is the slow oxygen evolution reaction (OER), which leads to an increase in overpotential and a decrease in hydrogen production efficiency. Here, Ni–Mo–S ultra-thin nanosheets were synthesized using the pulse reverse electrochemical deposition technique, and then this electrode was used as an electrode material for accelerating hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Remarkably, the optimized electrode needs only 74 mV to attain the 10 mA cm−2 current density in HER and require only 1.3 V vs RHE potential in the UOR process. Also, results showed that the replacement of the UOR with the OER process resulted in a significant improvement in the electrochemical production of hydrogen in which for delivering the current density of 10 mA cm−2 in overall urea electrolysis, only 1.384 V is needed. In addition, outstanding catalytic stability was obtained, after 50 h electrolysis, the voltage variation was negligible. Such outstanding catalytic activity and stability was due to 3-D ultrathin nanosheets, the synergistic effect between elements, and the superhydrophilic/superaerophobic nature of fabricated electrode. • Ni–Mo–S nanosheets was fabricated by pulse-revere electrodeposition. • Synthesized samples demonstrated outstanding electrocatalytic HER and UOR activity. • Synthesized electrodes demonstrated outstanding electrocatalytic durability. • The as fabricated surfaces showed superhydrophilic state. [ABSTRACT FROM AUTHOR]

Hypersonic flow transition from laminar to turbulent due to the surface irregularities, like local cavities, can greatly affect the surface heating and skin friction. In this work, the hypersonic flows over a three-dimensional rectangular cavity with length-to-width-to-depth ratio, L : W : D , of 19.9:3.57:1 at two angles of attack (AoA) were numerically studied with Improved-Delayed-Detached-Eddy Simulation (IDDES) method to highlight the mechanism of transition triggered by the cavity. The present approach was firstly applied to the transonic flow over M219 rectangular cavity. The results, including the fluctuating pressure and frequency, agreed with experiment well. In the hypersonic case at Mach number about 9.6 the cavity is seen as “open” at AoA of −10° but “closed” at AoA of −15° unconventional to the two-dimensional cavity case where the flow always exhibits closed cavity feature when the length-to-depth ratio L / D is larger than 14. For the open cavity flow, the shear layer is basically steady and the flow maintains laminar. For the closed cavity case, the external flow goes into the cavity and impinges on the bottom floor. High intensity streamwise vortices, impingement shock and exit shock are observed causing breakdown of these vortices triggering rapid flow transition. [ABSTRACT FROM AUTHOR]

Basalt fiber (BF) reinforced poly(lactic acid) (PLA) composites have promising applications in biomedical and automotive industries, but their mechanical performances are still largely restricted by poor interfacial properties between BFs and PLA. To this end, we develop a flexible/rigid hybrid nano-coating technology for fiber surface modification to improve the interfacial properties between BFs and PLA. An improved vacuum assisted prepreg process (VAPP) is proposed to prepare the high-performance modified BF/PLA composites. The SiO 2 nanoparticles and poly(ε-caprolactone) (PCL) polymer are designed as rigid and flexible phases, respectively, in hybrid nano-coating. The hybrid coating with a more rigid phase on the BFs can significantly enhance the mechanical properties of BF/PLA composites, especially their tensile strength and interlaminar fracture toughness. These values are approximately 29% and 110% higher, respectively, than those of unmodified BF/PLA composites. The increase in tensile strength results from a higher efficiency and continuous stress transfer derived from the flexible/rigid interfacial structure. An enhanced interlaminar fracture toughness is attributed to more dissipated energy due to the matrix yielding and crack deflecting at the interface induced by a large deformation of flexible PCL and crack pinning of SiO 2 nanoparticles, respectively. Furthermore, the modified BF/PLA composites with hybrid coatings of 1 wt% coating concentration exhibit optimal mechanical properties. This work provides a novel strategy for modifying the fiber-matrix interface to produce high-performance fiber-reinforced polymer composites. Image 1 [ABSTRACT FROM AUTHOR]