Characteristics of Band Gap and Low-frequency Wave Propagation of Mechanically Tunable Phononic Crystals with Scatterers in Periodic Porous Elastomeric Matrices

The characteristics of passive responses and fixed band gaps of phononic crystals (PnCs) limit their possible applications. For overcoming this shortcoming, a class of tunable PnCs comprised of multiple scatterers and soft periodic porous elastomeric matrices are designed to manipulate the band structures and directionality of wave propagation through the applied deformation. During deformation, some tunable factors such as the coupling effect of scatterer and hole in the matrix, geometric and material nonlinearities, and the rearrangement of scatterer are activated by deformation to tune the dynamic responses of PnCs. The roles of these tunable factors in the manipulation of dynamic responses of PnCs are investigated in detail. The numerical results indicate that the tunability of the dynamic characteristic of PnCs is the result of the comprehensive function of these tunable factors mentioned above. The strong coupling effect between the hole in the matrix and the scatterer contributes to the formation of band gaps. The geometric nonlinearity of matrix and rearrangement of scatterer induced by deformation can simultaneously tune the band gaps and the directionality of wave propagation. However, the matrix's material nonlinearity only adjusts the band gaps of PnCs and does not affect the directionality of wave propagation in them. The research extends our understanding of the formation mechanism of band gaps of PnCs and provides an excellent opportunity for the design of the optimized tunable PnCs and acoustic metamaterials.

Surface plasmon coupling regulated CsPbBr3 perovskite lasers in a metal–insulator–semiconductor structure

A strong coupling effect often occurs between a metal and semiconductor, so micro/nano-lasers based on surface plasmons can break through the optical diffraction limit and realize unprecedented linear and nonlinear enhancement of optical processes.

Double-Hoist Dynamics and Oscillation Control of a Quadcopter Carrying a Swinging and Twisting Load

Quadcopters can serve as aerial cranes that are able to suspend large-size loads below the fuselage for material-handling services. Double-hoist mechanisms help quadcopter to transport bulky loads effectively. However, double-hoist mechanisms exhibit strong coupling effect among the quadcopter’s attitude, load swing, and load twisting. Different from the single-hoist mechanisms, no effects have been directed at quadcopter slung loads with double-hoist mechanisms. A novel nonlinear dynamics model of a quadcopter carrying a distributed-mass load by double-hoist mechanisms is given in this paper. This explicit model captures the coupling between the quadcopter and load motion. Then a novel control method is proposed to reduce the swing and twisting of the load simultaneously. The simulation results illustrate that the control method succeeds in limiting the unwanted oscillations of quadcopter attitudes, load swing and twisting.

Stabilizing sulfur vacancy defects by performing “click” chemistry of ultrafine palladium to trigger a high-efficiency hydrogen evolution of MoS2

A “click” chemistry strategy is used to construct an all-pH efficient hydrogen evolution reaction (HER) catalyst with engineered unsaturated sulfur edges via a strong coupling effect between ultrafine Pd ensembles and Co-MoS2 nanosheets.

Cavity Catalysis by Co-operative Vibrational Strong Coupling of Reactant and Solvent Molecules

<i>para</i>-nitrophenyl acetate hydrolysis is studied under vibrational strong coupling in a Fabry-Perot cavity. By tuning the cavity resonance to the C=O vibrational stretching mode of both the reactant and solvent molecules, it is found that the reaction is accelerated by an order of magnitude. It is shown that this cavity catalysis involves a co-operative strong coupling effect between the solvent and reactant molecules. The reaction rate follows an exponential relation with respect to the solvent coupling strength. The combination of co-operative effects and cavity catalysis confirms the potential of VSC as a new frontier in chemistry. <br>

Cavity Catalysis by Co-operative Vibrational Strong Coupling of Reactant and Solvent Molecules

<i>para</i>-nitrophenyl acetate hydrolysis is studied under vibrational strong coupling in a Fabry-Perot cavity. By tuning the cavity resonance to the C=O vibrational stretching mode of both the reactant and solvent molecules, it is found that the reaction is accelerated by an order of magnitude. It is shown that this cavity catalysis involves a co-operative strong coupling effect between the solvent and reactant molecules. The reaction rate follows an exponential relation with respect to the solvent coupling strength. The combination of co-operative effects and cavity catalysis confirms the potential of VSC as a new frontier in chemistry. <br>