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International audience; Controlling low-frequency vibration of structures is still a challenge in modern industries. Metamaterials with local resonators present bandgaps at sub-wavelength frequencies. Propagative waves are not supported within the bandgaps. Therefore, metamaterials are widely proposed for vibration reduction or isolation at low frequencies. However, metamaterials with passive resonators suffer narrow effective frequency band and lack of adaptivity. In this talk, a new type of smart metamaterial with online controllable bandgaps is presented. The studied metamaterial is composed of piezoelectric actuators and digital synthetic impedance circuits (digital circuits). The digital circuit contains a micro-controller. By programming the micro-controller, the circuit can establish any desired impedance between the terminals of the connected piezoelectric patch, therefore to program the dynamical behaviours of the designed metamaterial. In this sense, a programmable metamaterial is studied. Experiments are performed to study its programmable dynamical behaviours, with a particular focus on isolation of vibration transmission. Results demonstrate that the proposed smart metamaterial can be flexibly programmed online to isolate vibration transmission in beam structures at desired frequencies or within a large frequency band. The proposed programmable metamaterial conception can be naturally extended to other kinds of structures like plates and shells, they are promising components in the future adaptive structures.

We characterize spin wave propagation and its modification by an electrical current in Permalloy(Py)/Pt bilayers with Py thickness between 4 and 20 nm. First, we analyze the frequency non-reciprocity of surface spin waves and extract from it the interfacial Dzyaloshinskii-Moriya interaction constant $D_s$ accounting for an additional contribution due to asymmetric surface anisotropies. Second, we measure the spin-wave relaxation rate and deduce from it the Py/Pt spin mixing conductance $g^{\uparrow\downarrow}_{eff}$. Last, applying a \textit{dc} electrical current, we extract the spin Hall conductivity $\sigma_{SH}$ from the change of spin wave relaxation rate due to the spin-Hall spin transfer torque. We obtain a consistent picture of the spin wave propagation data for different film thicknesses using a single set of parameters $D_s=0.25$ pJ/m, $g^{\uparrow\downarrow}_{eff} = 3.2\times 10^{19}$ m$^{-2}$ and $\sigma_{SH}=4\times10^{5}$ S/m.

The present paper aims to apply the concept of energy pumping for noise reduction at propagation and reception paths. This phenomenon consists in irreversible energy transfer from a linear primary system to a nonlinear energy sink, where the energy is finally dissipated. In this study, we turn a loudspeaker to an electroacoustic absorber by connecting at its transducers terminals a passive nonlinear shunt circuit playing the role of an absorber. The equivalent model consists of a linear structure describing the displacement of the loudspeaker, linearly coupled to a cubic nonlinear energy sink. For the case of 1:1 resonance, the Invariant manifold approach is applied for different time scales. It enables the detection of the slow invariant manifold and equilibrium and fold singularities at the fast and slow time scales respectively. This methodology provides a predictive tool allowing the design of the nonlinear energy sink for better control of the main system. The analytical and numerical results show that the nonlinear shunt circuit managed to expand the frequency band of the controlled system.

International audience; Aim - We explored the associations between childhood exposure to screens, including televisions, computers, game consoles, tablets and smartphones and primary language disorders. Methods - This multi-centre case-control study comprised 167 children aged 3.5-6.5 years, who were born in 2010-2012 and diagnosed with primary language disorders, and 109 matched controls without language disorders. Questionnaires were completed by their parents who were recruited by 16 family doctors and 27 speech and language therapists in the Ille-et-Vilaine region of France. The data were analysed using a multivariate logistic regression model and presented as adjusted odds ratios (aOR) and 95% confidence intervals (95% CI). Results - We found that cases (44.3%) and controls (22.0%) exposed to screens in the morning before nursery or primary school were three times more likely to develop primary language disorders (aOR 3.40, 95% CI 1.60-7.23). When this risk was combined with rarely or never discussing screen content with their parents (aOR 2.14, 95% CI 1.01-4.54) they were six times more likely to have language problems (aOR 5.86, 95% CI 1.44-23.95). Conclusion - Being exposed to screens in the morning before school, and rarely or never discussing screen content with parents, meant children were six times more likely to develop primary language disorders.

This data article presents the UK City LIFE1 data set for the city of Birmingham, UK. UK City LIFE1 is a new, comprehensive and holistic method for measuring the livable sustainability performance of UK cities. The Birmingham data set comprises 346 indicators structured simultaneously (1) within a four-tier, outcome-based framework in order to aid in their interpretation (e.g., promote healthy living and healthy long lives, minimize energy use, uncouple economic vitality from CO2 emissions) and (2) thematically in order to complement government and disciplinary siloes (e.g., health, energy, economy, climate change). Birmingham data for the indicators are presented within an Excel spreadsheet with their type, units, geographic area, year, source, link to secondary data files, data collection method, data availability and any relevant calculations and notes. This paper provides a detailed description of UK city LIFE1 in order to enable comparable data sets to be produced for other UK cities. The Birmingham data set is made publically available at http://epapers.bham.ac.uk/3040/ to facilitate this and to enable further analyses. The UK City LIFE1 Birmingham data set has been used to understand what is known and what is not known about the livable sustainability performance of the city and to inform how Birmingham City Council can take action now to improve its understanding and its performance into the future (see “Improving city-scale measures of livable sustainability: A study of urban measurement and assessment through application to the city of Birmingham, UK” Leach et al. [2]).

International audience; Smart metacomposites constitute a new concept of periodical structures including passive and semi-active devices which are optimized to provide new functionalities. Based on recent works on the application of Floquet-Bloch theorem to periodical mechanical systems including frequency-dependent parameters, we propose in this paper an extension to vibroacoustic behavior analysis of smart structures. The objective is to optimize electronic circuits used to shunt some piezoelectric patches distributed on the structure, in order to minimize the acoustic radiation of the structure. The proposed approach is based on the computation of the multi-modal wave dispersion curves into the whole first Brillouin zone of the structure, and associated propagation characteristics in the acoustic fluid. The impedance of the shunt circuit is then optimized in order to render the acoustic waves evanescent. The design is performed on the infinite periodic structure, and the smart metacomposite is finally integrated in a finite structure for validation purposes.

International audience; In the context of mid-frequency elastodynamical analysis of periodic structures, the Floquet-Bloch theorem has been recently applied. The latter allows the use of limited-size modeling of a representative cell to characterize waves dispersion properties of the assembled structure. The theorem provides a rigorous and well posed spectral problem representing waves dispersion in viscolelastic media. In particular, the wave-FEM (WFE) method and associated techniques are based on the Floquet-Bloch approach. Most of the current applications are limited either to undamped or to slightly damped systems. Through the mesh of the k-space (k being the wave number vector) inside or at the boundary of the first Brillouin zone is performed. For each wave headings a linear spectral problem is solved in order to obtain the corresponding eigenfrequency and the corresponding Floquet vector. Such process is more easily implemented for undamped structures but face some drawbacks when damping is considered. In this paper, the Floquet-Bloch theorem is used to set up an alternative technique in order to estimate the dispersion characteristics of a periodic structure. The approach is based on the same basic assumption, but the generalized eigenvalue problem which has to be solved differs from the one usually considered in WFE. Instead of discretising the k-space, the harmonic frequency and the wave heading are used to scan the k-space. Then the formulated eigenvalue problem is solved and the dispersion characteristics are obtained, including spatial attenuation terms. Some fundamentals properties of the eigensolutions are discussed, and the methodology is finally applied on a 2D waveguide application which can be found in the literature for an undamped case. The same example is considered with various damping levels, in order to illustrate the performances and specificities the efficiency of proposed approach. The proposed approach finds application in the analysis of wave propagation in the presence of damping materials or shunted piezoelectric patches, as well as in actively controlled systems, where equivalent damping terms are associated with the considered control scheme.