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Active structural acoustic radiation control of a piezolaminated arbitrary thick rectangular plate with a mixed-norm H_2/H_∞ robust controller is developed. The structure is made of a transversely isotropic host layer with a distributed piezoelectric sensor layer as well as a matched piezoelectric actuator layer, facing high frequency uncertainties and random external disturbances. The elasto-acoustic formulation, based on the exact linear 3D piezo-elasticity theory, is developed for problem of fully coupled structure and acoustic mediums. Identification of the fluid/structure interaction system with subspace algorithm is implemented on actuator/sensor data sets. A multi-objective controller with regional pole placement, formulated in LMI framework, is synthesized while unmodeled dynamics are treated as multiplicative uncertainties. Numerical simulations confirm effectiveness of the implemented multi-objective robust active control scheme for reduction of radiated acoustic power from a piezocomposite plate, without stimulating any instability. Also, better tracking performance and disturbance rejection of mixed-norm controller is observed in comparison to that of H_2 and H_∞ controllers. Finally, validity of the elasto-acoustic model is proved by results obtained from a finite element software, as well as with the data available in the literature.

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In this paper based on the Euler-Bernoulli beam model, the primary resonance a curved single carbon nanotube subjected to axial thermal force in the case of low temperature and high temperature and resting on a viscoelastic foundation is analytically investigated. The nonlinear partial differential governing equation is reduced to nonlinear ordinary differential governing equation by using of a single-mode Galerkin approximation along with the sinusoidal curvature for clamped-clamped single walled carbon nanotube under harmonic external force. The method of multiple scales is applied to determine the analytical primary resonance frequency response. Considering the curved geometry and the mid-plane stretching, a quadratic and cubic terms are presented in the governing equation. The effects of temperature change in high temperature and low temperature conditions, viscoelastic coefficients of medium, amplitude of sinusoidal curvature and excitation amplitude are investigated to study the property frequency response and development or elimination of forward and backward jumping phenomenon in primary resonance frequency response. The results show that these parameters have a significant effect on the frequency response of a curved single walled carbon nanaotubes under transvers harmonic force.

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