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Spin-wave propagation in microfabricated 20 nm thick, 2.5 μm wide Yttrium Iron Garnet (YIG) waveguides is studied using propagating spin-wave spectroscopy (PSWS) and phase resolved micro-focused Brillouin Light Scattering (l-BLS) spectroscopy. We demonstrate that spin-wave propagation in 50 parallel waveguides is robust against microfabrication induced imperfections and extract spin-wave propagation parameters for the Damon-Eshbach configuration in a wide range of excitation frequencies. As expected from its low damping, YIG allows for the propagation of spin waves over long distances; the attenuation lengths is 25 μm at l0H45 mT. Moreover, direct mapping of spin waves by l-BLS allows us to reconstruct the spin-wave dispersion relation and to confirm the multi-mode propagation in the waveguides, glimpsed by propagating spin-wave spectroscopy. [ABSTRACT FROM AUTHOR]

The pressure-based, current-driven impedance control technique known as "Electroacoustic Absorption" has offered new horizons for room modal equalization at low frequencies, steerable anomalous reflection, acoustic transmission attenuation and non-reciprocal wave propagation. Nevertheless, its level of performance is strongly limited by stability constraints. A primary source of instability is the loss of acoustical passivity due to time delay in the digital implementation of the controller. In this paper, the effect of time delay on the Electroacoustic Absorber stability is verified by correlating, both numerically and experimentally, the loss of acoustical passivity at high frequencies to the upsurge of instability in a one-dimensional closed cavity. Then, we show the effect of placing a porous layer in front of the Electroacoustic Absorber, allowing to counteract for the loss of acoustical passivity and enlarge the passivity margin. Finally, we provide an integral constraint on the absorption spectrum valid for the pressure-based, current-driven architecture of the Electroacoustic Absorber. It generalizes the integral constraint for purely passive absorbers to electro-active impedance controlled loudspeakers, and demonstrates the close interdependence between absorption bandwidth, passivity, and electrical source supply by a straightforward analytical expression. • Effect of time-delay on acoustical passivity of impedance-control electroacoustic resonators. • Correlation between passivity loss and instability. • Generalization of integral constraint from purely passive to electro-active absorbers. • High-frequency passivation technique. [ABSTRACT FROM AUTHOR]

This study presents an experimental investigation of the application of a periodic array of shunted piezoelectric patches with negative capacitance for the broadband control of waves propagating on a flexible plate. A 15 × 5 array of piezoelectric patches is bonded onto the top surface of a freely supported rectangular plate. The patch array is intended to serve as an active interface between two regions of the plate, where one region has an input disturbance force and the other does not. Each patch is shunted through a single circuit, reproducing a resistance in series with a negative capacitance. The magnitude of the reactive part of the negative shunting impedance is tuned close to the intrinsic capacitance of the piezoelectric patch. The real part is adjusted for either light damping so as to induce a reactive (reflective) response, or with heavy damping to induce greater absorption. The experimental responses of the system equipped with this active interface display a strong attenuation or reflection of vibrations, depending on the shunt resistance, over a large frequency range, including the mid-frequency regime. In an effort to control vibroacoustic phenomena, this study represents the first attempt to implement an integrated smart metacomposite active interface on a plate structure. [ABSTRACT FROM PUBLISHER]

The propagation of wave modes in elastic structures with shunted piezoelectric patches is dealt with in this work. The wave finite element approach, which is based on the finite element method and periodical structure theory, is firstly developed as a prediction tool for wave propagation characteristics in beam like structures, and subsequently extended to consider shunted piezoelectric elements through the diffusion matrix model (DMM). With these numerical techniques, reflection and transmission coefficients of propagating waves in structures with shunted piezoelectric patches can be calculated. The performance of shunted piezoelectric patches on the control of wave propagation is investigated numerically with the DMM. Forced response of the smart structure can also be calculated, and based on which the time response of the structure can be obtained via an inverse discrete fourier transform approach. These general formulations can be applied to all types of slender structures. All these numerical tools can facilitate design modifications and systematic investigations of geometric and electric parameters of smart structures with shunted piezoelectric elements. [ABSTRACT FROM AUTHOR]

Abstract: The wave propagation problem in thin-walled elastic structures with shunted piezoelectric patches is investigated in this work. Based on the finite element (FE) method and periodical structure theory, the wave finite element (WFE) approach is firstly developed as a prediction tool for wave propagation characteristics in thin-walled beam structures, and subsequently extended to consider shunted piezoelectric elements through the diffusion matrix model (DMM). These numerical techniques enable the calculation of reflection and transmission coefficients of propagating waves in thin-walled structures with shunted piezoelectric patches. The performance of shunted piezoelectric patches on the control of wave propagation is analyzed numerically with the DMM. Forced response of thin-walled structures with shunted piezoelectric patches can also be obtained via the forced wave finite element (FWFE) formulation. With the frequency response issued from the FWFE calculation, the time response of these structures can be acquired via an inverse discrete Fourier transform (IDFT) approach. An extraction technique for reflection coefficient is proposed and can be applied in both numerical simulations and experiments. The formulations proposed in this work are general and can be applied to all types of slender structures. [Copyright &y& Elsevier]