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The generation of secondary vortices from a wall-bounded vorticity sheet is a frequent occurrence in vortex ring–structure interactions. Such interactions arise in both engineering and biomedical applications, including tracheoesophageal speech. This study investigated the evolution of secondary vorticity following impact of an axisymmetric vortex ring on a concave hemicylindrical cavity. A primary vortex ring (PVR) with a formation number of F=2.00 and Reynolds number of ReΓ=1500 was generated within a water tank. Five different ratios of hemicylindrical cavity radius (Rcyl) to PVR radius (Rv) were examined; namely, γ=4,  3,  212,  2, and 112. Flow visualization and particle image velocimetry analysis of the scenarios revealed the asymmetric impact of the PVR on the cavity surface. This asymmetric impact leads to distinctive flow dynamics in the evolution of secondary vorticity across both the transverse and longitudinal planes. In the transverse plane, the PVR impact generated a secondary vortex ring (SVR) and a tertiary vortex ring (TVR). Following generation, the SVR and TVR rotated completely around the PVR. In the longitudinal plane, the SVR produced a horseshoe-like loop instead of rotating around the PVR completely. For γ=4,  3, and 212, the SVR loop moved upward due to self-induction. For γ=2 and  112, the legs of the SVR horseshoe-like loop experienced reconnection and produced two new vortex rings. The upward trajectory of the SVR horseshoe-like loop varied with γ, tending to move further from the primary ring's axis as γ decreased. 

Bonded magnetic composites combine the cost-effectiveness, low density, and manufacturing flexibility of conventional polymer binders with the unique magnetic characteristics of magnetic powders/fillers to form multifunctional magneto polymeric composites that offer superior properties to conventional sintered magnets. In this study, a co-rotating twin screw extruder was used to fabricate 20 and 40 wt.% strontium ferrite/polyamide 4.6 bonded magnetic composites viable for fused filament fabrication 3D printing. The characterization conducted on the bonded magnetic composites was scanning electron microscopy, simultaneous differential thermogravimetry, and vibrating sample magnetometry. The microstructure of the bonded composite exhibited a uniform platelet morphology of the strontium ferrite magnetic particles. There was no observable depreciation in the melting transitions, which suggests a thermally resistant magnetic composite. An appreciable increment in % crystallinity of 13 and 20% for 20wt. % and 40wt. % strontium ferrites bonded magnets were observed. This is attributable to the heterogeneous nucleation phenomenon, where the metal powders act as nucleation sites for increased crystalline domains. The bonded composite exhibited significant magnetic anisotropy, with the remanence (Mr), which is the most important property for magnetic application significantly increasing to 49.8% along the easy direction in comparison to the hard axis. This suggests the viability of the fabricated bonded composites in viable in producing anisotropic bonded magnetic devices, which are considered to exhibit stronger magnetic properties. 

Catalytic performance of Ni/zeolite, Ni-Fe/zeolite, and Ni-Fe-Mg/zeolite catalysts were investigated in steam reforming of toluene as a biomass tar model compound to explore promotional effect of MgO and Fe on Ni/ zeolite support. The Ni-Fe-Mg/zeolite catalysts with optimum metallic composition showed higher catalytic performance over corresponding monometallic Ni and Fe catalysts and Ni-Fe/zeolite (bimetallic) catalysts. Addition of Mg to Ni-Fe/zeolite catalyst enhanced the tar reforming reactions and increased the carbon de- position tolerance. The results suggest that Ni-Fe/zeolite and Ni-Fe-Mg/zeolite catalysts have great potential for application in the steam reforming of biomass tar.