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In this paper, we present a study of vibration characteristics of the double-beam structures combined with the concept of the acoustic black hole (ABH), which is an effective technique for vibration and noise control. In the proposed double-beam structure, the ABH beam as the vibration damper is attached to the primary uniform beam by a range of translational and rotational springs. We formulate the closed-form spectral element matrix of the double-beam structure and calculate the natural frequencies and mode shapes of the system. The results demonstrate the ABH effect of increasing the modal damping ratios. We also study the power flow and mechanical intensity of the system to offer physical insight into the vibration suppression mechanism of the ABH. A detailed parametric analysis of both translational and rotational springs is carried out. The investigation contributes to the exact dynamic modelling and analysis of the double-beam system containing ABH elements. Furthermore, the proposed ABH double-beam structure shows great potential for vibration control and energy harvesting. [ABSTRACT FROM AUTHOR]

CO2 oxidative dehydrogenation of propane (CO2-ODHP) is a strategy of "two birds with one stone" to synthesize propylene and utilize CO2. However, the reaction is always conducted at high temperatures (>550 °C). In the present work, we have for the first time conducted the reaction at 270 °C under photothermal conditions over several BiOX (X = Cl, Br, I) nanocatalysts. Among them, the BiOI nanosheet catalyst exhibited the highest C3H6 formation activity of 282.6 μmol gcat−1 h−1 with 89% selectivity. The lattice oxygen species on the catalyst could catalyze propane dehydrogenation to propylene, and simultaneously, oxygen vacancies were formed. The oxygen vacancies are responsible for CO2 reduction to CO. In addition, the catalyst is facet-dependent, and the (001) facets are more active than the (110) facets. The present work successfully verifies the feasibility of photothermal catalytic CO2-ODHP over BiOI nanosheets and also provides a new insight to construct other facet-dependent dual-functional redox catalysts. [ABSTRACT FROM AUTHOR]

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The acoustic black hole (ABH) structure has gradually become a research hotspot in recent years due to its ascendant capacity of vibration attenuation and energy accumulation. To further improve the performance of vibration and noise reduction, the ultra-low frequency broadband gap of a one-dimensional structure embedded ABHs with power-law material properties is investigated in this paper. Based on the Euler-Bernoulli theory, the Transfer Matrix Method (TMM) is used to establish the dynamic model of the dual power-law ABH (DP-ABH) beam. The band structure results obtained by TMM and the finite element method are compared with each other to verify the ultra-low broadband gap of the structure. Comparison with the traditional ABH show that the ultra-low frequency performance of the DP-ABH is due to the enhanced local resonator properties with reduction of dual power-law local stiffness. Parameter analysis served as a guide for optimization is carried out and a method of combining NSGA-II and TMM is applied to optimize the ABH section with full parameters, to consider a trade-off between lower bandgaps and higher stiffness. The investigation shows that the ultra-low broadband gaps of the periodic DP-ABHs structure, which meets adequate stiffness requirements, can be designed by optimized configuration. [ABSTRACT FROM AUTHOR]

This paper presents a study of dynamics analysis and optimization of a nonlinear cantilevered beam with the combination of the acoustic black hole (ABH) and the nonlinear energy sink (NES). We establish the nonlinear equations of a cantilevered beam with both the ABH and a NES. Then, we conduct sensitivity analysis of the parameters of the NES for a further understanding. To discover the potential of the NES efficiency, we define a multi-objective optimization problem and solve it by using cell mapping method. The numerical results show that the nonlinear ABH beam with the optimal NES can dissipate 97.7% of the input energy due to the energy concentration capability of the ABH and the irreversible energy transfer behavior of the NES. [ABSTRACT FROM AUTHOR]