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Transformation acoustics opens a new avenue towards the architecture, modeling and simulation of a new class of sonic composites with scatterers made of various materials and having various shapes embedded in an epoxy matrix. The design of acoustic scatterers is based on the property of Helmholtz equations to be invariant under a coordinate transformation, i.e., a specific spatial compression is equivalent to a new material in a new space. In this paper, the noise suppression for a wide full band-gap of frequencies is discussed for spherical shell scatterers made of auxetic materials (materials with negative Poisson's ratio). The original domain consists of spheres made from conventional foams with positive Poisson's ratio. The spatial compression is controlled by the coordinate transformation, and leads to an equivalent domain filled with an auxetic material. The coordinate transformation is strongly supported by the manufacturing of auxetics which is based on the pore size reduction through radial compression molds. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the functionality of a compact robotic system with hybrid kinematic structure, consisting in two hexapods serially connected and controlled in such a way that they have identical configurations any time, in terms of accuracy and maneuverability. By the aid of a demonstration model it was intended to prove that the system substantially benefits of the precision and robustness of the parallel structures and simultaneously is capable to generate complex motions in a significant extended workspace compared with a single hexapod. The double hexapod system answers the actual need of accurate, complex and robust positioning systems used in new technologies and possibly in robotic surgery. [ABSTRACT FROM AUTHOR]

The present paper points out the scenario of the hyperchaotic attractor formation (an attractor with at least two positive Lyapunov exponents) in a class of models governed by the Sommerfeld effects. The Sommerfeld effect is the result of the conservation law of energy. When a dynamical system is coupled to a power source, it acts like a energy sink for which a part of the source energy is spend to deform the system rather than increasing the drive speed. The Sommerfeld effect involves riddling bifurcation which explains the creation of the hyperchaotic attractor. [ABSTRACT FROM AUTHOR]

A vibrating system is said ideal when its excitation is not influenced by the response of the system. When the excitation is influenced by the response of the system, the system is said non-ideal. A new degree of freedom is present in such systems, for which a new equation has to be added in order to describe how the energy source interacts with the vibrating system. The energy transfer is governed by the Sommerfeld effect which appears as a result of the law of energy conservation. In this paper, the response to vibrations of a class of non-ideal systems is analyzed. The coupling between the structure to a power source acts like a energy sink for which a part of the source energy is spend to deform the system rather than increasing the drive speed. The Sommerfeld effect involves on the one hand the vibration reduction and, on the other hand, a chaotic behavior with riddling bifurcation which explains the creation of the hyperchaotic attractors. [ABSTRACT FROM AUTHOR]

The sound attenuation in a sonic composite without/with point defects is studied using a new method that combines the features of the cnoidal method and the genetic algorithm. Acoustic scatterers are composed by piezoceramic hollow spheres of functionally graded materials-the Reddy and cosine graded hollow spheres. This method enables to obtain the dispersion relation for defect modes, and the prediction of the evanescent nature of the modes inside the band-gaps. [ABSTRACT FROM AUTHOR]

In this paper, the tangential and normal discontinuities at the interface between the scatterer and the matrix are independently modeled, and these relative displacements are directly proportional to the corresponding components of tractions at the interface. The generation of full band-gaps is investigated on the basis of the derived imperfect interface conditions for a sonic plate with an array of acoustic piezoceramic hollow spheres scatterers embedded in an epoxy matrix. The scatterers are made from functionally graded materials with radial polarization. Numerical evaluation has shown that imperfect interface may have a significant effect on the increasing of the length of the full band-gaps. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Transformation acoustics opens a new avenue towards the fabrication of a new class of sonic composites with scatterers made of auxetic materials embedded in the epoxy matrix. The design of the acoustic scatterers is based on the property of Helmoltz equations to be invariant under coordinate transformations, i.e. a specific spatial compression is equivalent to a variation of the material parameters in the original space. In this paper, the noise suppression for a wide full band-gap of frequencies is discussed for spherical shell scatterers made of auxetic materials. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]