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The design of phononic crystals and acoustic metamaterials with tunable and adaptive wave properties remains one of the outstanding challenges for the development of next generation acoustic devices. We report on the numerical and experimental demonstration of a locally resonant acoustic metamaterial with dispersion characteristics, which autonomously adapt in response to changes of an incident aerodynamic flow. The metamaterial consists of a slender beam featuring a periodic array or airfoil-shaped masses supported by a linear and torsional springs. The resonance characteristics of the airfoils lead to strong attenuation at frequencies defined by the properties of the airfoils and the speed on the incident fluid. The proposed concept expands the ability of existing acoustic bandgap materials to autonomously adapt their dispersion properties through fluid-structure interactions, and has the potential to dramatically impact a variety of applications, such as robotics, civil infrastructures, and defense systems. [ABSTRACT FROM AUTHOR]

One of the outstanding challenges in phononic crystals and acoustic metamaterials development is the ability to tune their performance without requiring structural modifications. We report on the experimental demonstration of a tunable acoustic waveguide implemented within a two-dimensional phononic plate. The waveguide is equipped with a periodic array of piezoelectric transducers which are shunted through passive inductive circuits. The resonance characteristics of the shunts lead to strong attenuation and to negative group velocities at frequencies defined by the circuits' inductance. The proposed waveguide illustrates the concept of a controllable acoustic logic port or of an acoustic metamaterial with tunable dispersion characteristics. [ABSTRACT FROM AUTHOR]

This paper explores the vibration damping properties of thermal barrier coatings (TBCs) containing thin plastically deformable metallic layers embedded in an elastic ceramic matrix. We develop an elastic-plastic dynamical model to study how work hardening, yield strain, and elastic modulus of the metal affect the macroscopic damping behavior of the coating. Finite element (FE) simulations validate the model and are used to estimate the damping capacity under axial and flexural vibration conditions. The model also provides an explanation for the widely observed nonlinear variation of the loss factor with strain in plasma-spayed TBCs. Furthermore, it facilitates the identification of multilayer configurations that maximize energy dissipation. [ABSTRACT FROM AUTHOR]

We report a new class of tunable and switchable acoustic metamaterials comprising resonating units dispersed into an elastic matrix. Each resonator consists of a metallic core connected to the elastomeric matrix through elastic beams, whose buckling is intentionally exploited as a novel and effective approach to control the propagation of elastic waves. We first use numerical analysis to show the evolution of the locally resonant band gap, fully accounting for the effect of nonlinear pre-deformation. Then, we experimentally measure the transmission of vibrations as a function of the applied loading in a finite-size sample and find excellent agreement with our numerical predictions. The proposed concept expands the ability of existing acoustic metamaterials by enabling tunability over a wide range of frequencies. Furthermore, we demonstrate that in our system the deformation can be exploited to turn on or off the band gap, opening avenues for the design of adaptive switches. [ABSTRACT FROM AUTHOR]

Periodic arrays of hybrid-shunted piezoelectric actuators are used to suppress vibrations of an aluminum plate over broad frequency bands. Commonly, piezoelectric-shunted networks are used for individual mode control, through tuned, resonant resistive/inductive circuits, and for broadband vibration attenuation, through negative impedance converters. Periodically placed resonant shunts allow for broadband reduction resulting from the attenuation of propagating waves in frequency bands which are defined by the spatial periodicity of the array and by the shunting parameters considered on the circuit. Such attenuation typically occurs at medium–high frequencies, while negative impedance converter networks are effective in reducing the vibration amplitudes of the lower modes of the structure. In this article, the combination of periodic resonant shunts and negative impedance converter networks on the same aluminum panel is studied to verify the possibility of combining the advantages of the two concepts. Both numerical and experimental investigations demonstrate that broadband attenuation is achieved in the mid–high frequency regimes due to the presence of resistive/inductive networks, while the combination with negative impedance converter circuits is responsible for amplitude reduction of the full frequency spectrum. Numerical simulations and frequency response measurements on a plate demonstrate that an attenuation region of about 1000 Hz is achieved with a maximum 8 dB vibration reduction. [ABSTRACT FROM AUTHOR]

Abstract: This work presents numerical and experimental investigations of the application of a periodic array of resistive–inductive (RL) shunted piezoelectric patches for the attenuation of broadband noise radiated by a flexible plate in an enclosed cavity. A 4×4 lay-out of piezoelectric patches is bonded to the surface of a rectangular plate fully clamped to the top face of a rectangular cavity. Each piezo-patch is shunted through a single RL circuit, and all shunting circuits are tuned at the same frequency. The response of the resulting periodic structure is characterized by frequency bandgaps where vibrations and associated noise are strongly attenuated. The location and extent of induced bandgaps are predicted by the application of Bloch theorem on a unit cell of the periodic assembly, and they are controlled by proper selection of the shunting circuit impedance. A coupled piezo-structural-acoustic finite element model is developed to evaluate the noise reduction performance. Strong attenuation of multiple panel-controlled modes is observed over broad frequency bands. The proposed concept is tested on an aluminum plate mounted in a wooden box and driven by a shaker. Experimental results are presented in terms of pressure responses recorded using a grid of microphones placed inside the acoustic box. [Copyright &y& Elsevier]

Mental health of immigrants is an important social and clinical issue. Immigrants may report higher rates of mental disorders and lower levels of use of mental health service with respect to natives. The aim of the present work is to review recent findings of the psychopathology of immigrants and analyze how to adapt the mental care settings through the use of mother tongues. We searched the literature to individuate and review the most recent scientific articles focused on the psychopathology of immigrants realized in Europe. Moreover, we summarized the guidelines about immigrants mental health care and we focused on the barriers caused by language. We individuated 15 papers reporting data about mental disorders among immigrants and the related risk and protective factors. The articles reported information about psychosis, depression, anxiety, post-traumatic stress disorder, somatization and suicide rates. Risk and protective factors are individuated mainly among social factors ( e.g. ethnic density effect, hosting countries' policies). Furthermore, immigrants encounter language barriers in the use of mental care services. The realization of cross-cultural training and the development of a working alliance between clinicians and interpreters resulted to be effective solutions even if these interventions are not frequently implemented. The extent of migratory flows and the related difficulties experienced by immigrants require attention and well-informed interventions. The high rates of incidence of mental disorder and the strict number of services who implement interventions taking into accounts fundamental aspect as language show that there is still a lot to do.

We report a new class of tunable and switchable acoustic metamaterials comprising resonating units dispersed into an elastic matrix. Each resonator consists of a metallic core connected to the elastomeric matrix through elastic beams, whose buckling is intentionally exploited as a novel and effective approach to control the propagation of elastic waves. We first use numerical analysis to show the evolution of the locally resonant band gap, fully accounting for the effect of nonlinear pre-deformation. Then, we experimentally measure the transmission of vibrations as a function of the applied loading in a finite-size sample and find excellent agreement with our numerical predictions. The proposed concept expands the ability of existing acoustic metamaterials by enabling tunability over a wide range of frequencies. Furthermore, we demonstrate that in our system the deformation can be exploited to turn on or off the band gap, opening avenues for the design of adaptive switches.