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Burokur S.N.,CNRS Fundamental Electronics Institute | Burokur S.N.,CNRS Mechanical Energy and Electromagnetism Lab | Daniel J.-P.,Advanten | Ratajczak P.,Orange Group | De Lustrac A.,CNRS Fundamental Electronics Institute
Applied Physics Letters | Year: 2010

The directive emission from a bilayered metamaterial surface is numerically and experimentally reported. The LC-resonant metasurface is composed of both a capacitive and an inductive grid constituted by copper strips printed on both sides of a dielectric board. By the incorporation of varactor diodes in the capacitive grid, resonance frequency and phase characteristics of the metamaterial can be tuned. The tunable phase metasurface is used as a partially reflecting surface in a Fabry-Perot resonance cavity. Far field radiation patterns obtained by direct measurements show the reconfigurability of emission frequency while maintaining an enhanced directivity. © 2010 American Institute of Physics.


Dhouibi A.,CNRS Mechanical Energy and Electromagnetism Lab | Nawaz Burokur S.,University Paris - Sud | De Lustrac A.,University Paris - Sud | Priou A.,CNRS Mechanical Energy and Electromagnetism Lab
Applied Physics Letters | Year: 2013

The broadband directive emission from a metamaterial surface is numerically and experimentally reported. The metasurface, composed of non-resonant complementary closed ring structures, is designed to obey the refractive index of a half Maxwell fish-eye lens. A planar microstrip Vivaldi antenna is used as transverse magnetic polarized wave launcher for the lens. A prototype of the lens associated with its feed structure has been fabricated using standard lithography techniques. To experimentally demonstrate the broadband focusing properties and directive emissions, both the far-field radiation patterns and the near-field distributions have been measured. Measurements agree quantitatively and qualitatively with theoretical simulations. © 2013 American Institute of Physics.


Tichit P.-H.,University Paris - Sud | Burokur S.N.,CNRS Mechanical Energy and Electromagnetism Lab | De Lustrac A.,University Paris - Sud
Optics Express | Year: 2011

Using the idea of wave manipulation via transformation optics, we propose a way to create a quasi-perfect isotropic emission from a directional one. The manipulation is enabled by composite metamaterials that correspond to a space stretching around the source. It is shown that the directive radiation of a plane source larger than the operating wavelength can be transformed into an isotropic one by modifying the electromagnetic properties of the space around it. A set of parameters allowing practical realization of the proposed device is defined. Numerical simulations using Finite Element Method (FEM) are performed to illustrate the proposed coordinate transformation. This idea, which consists in strongly reducing the apparent size of a radiating source, can find various applications in novel antenna design techniques. © 2011 Optical Society of America.


Ghasemi A.,University Paris - Sud | Burokur S.N.,University Paris - Sud | Dhouibi A.,University Paris - Sud | De Lustrac A.,CNRS Mechanical Energy and Electromagnetism Lab
IEEE Antennas and Wireless Propagation Letters | Year: 2013

A high-gain low-profile Fabry-Pérot (FP) leaky-wave antenna (LWA) presenting one-dimensional high beam steering properties is proposed in this letter. The structure consists of a ground plane and a varying inductive partially reflective surface (PRS). A microstrip patch antenna is embedded into the cavity to act as the primary feed. As design examples, antennas are designed to operate at 9.5 GHz. Subwavelength FP cavities with fixed overall thickness of λ0/6 (where λ0 is the free-space operating wavelength) are fabricated and measured. The impact of varying the PRS inductance is analyzed. It is shown that a high beam steering angle from broadside toward endfire direction close to 60° can be obtained when judiciously designing the inductive grid of the PRS. © 2002-2011 IEEE.


Dhouibi A.,CNRS Mechanical Energy and Electromagnetism Lab | Burokur S.N.,University Paris - Sud | De Lustrac A.,University Paris - Sud | Priou A.,CNRS Mechanical Energy and Electromagnetism Lab
IEEE Antennas and Wireless Propagation Letters | Year: 2013

A low-profile substrate-integrated lens antenna is designed using planar metamaterials for a broadband operation. The lens antenna is based on embedding a Vivaldi antenna source inside a parallel-plate waveguide to illuminate a half Maxwell fish-eye (HMFE) lens operating in X-band. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary nonresonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher inserted into the parallel-plate waveguide. The electric field distribution inside the antenna system has also been explored numerically. Far-field radiation patterns have been measured on a fabricated prototype in an anechoic chamber. It has been shown from both near- and far-field plots that the proposed planar antenna presents good focusing properties. © 2013 IEEE.


Herve P.,CNRS Mechanical Energy and Electromagnetism Lab | Cedelle J.,CNRS Mechanical Energy and Electromagnetism Lab | Negreanu I.,Ecole Polytechnique - Palaiseau
Infrared Physics and Technology | Year: 2012

This paper presents, in the context of materials dynamic behaviour study, a method for simultaneous measurement of the temperature and emissivity of a solid's surface, by the use of infrared radiation. In contrast to existing methods, this method has no need for a pre-measurement of the surface emissivity. The emissivity and the temperature are measured simultaneously, by detecting the variations of emitted radiation and infrared radiation reflecting on the surface, at two different spectral zones. In this way, the accuracy of the measured temperature is greatly improved in cases were the surface optical properties vary during the measurement. Several experiments were carried out in order to complete the theoretical foundation of the method and to outline its accuracy and some of its limitations. There are various industrial applications of this method, for example the control of the temperature of the mechanical parts during work machining. One of them may be the measurement of the temperature of a sample during mechanical testing. An application of the method is proposed, that is easy to employ with non-sophisticated infrared and optical components. The results confirm the accuracy of the proposed method with an order of 3% of precision for temperature determination. © 2011 Elsevier B.V. All rights reserved.


Vidal P.,CNRS Mechanical Energy and Electromagnetism Lab | Polit O.,CNRS Mechanical Energy and Electromagnetism Lab
Computer Methods in Applied Mechanics and Engineering | Year: 2013

This paper presents a C1 6-node triangular finite element for multilayered composite plates submitted to mechanical and thermomechanical loads. It is based on the sinus model with layer refinement and includes the transverse normal effect. This kinematics allows to exactly ensure both (i) the continuity conditions for displacements and transverse shear stresses at the interfaces between layers of a laminated structure, and (ii) the boundary conditions at the upper and lower surfaces of the plates. It is important to notice that the number of unknowns is independent of the number of layers. This finite element is able to model both thin and very thick plates without any pathologies of the classic plate finite elements (shear locking, spurious modes, etc.). It is built on the Argyris interpolation for bending and the Ganev interpolation for membrane displacements and transverse shear rotations. The representation of the transverse shear strains by cosine functions allows avoiding shear correction factors. In addition, the transverse normal stress can be accurately recovered from equilibrium equations at the post-processing level, using the high degree of interpolation polynomia.Both mechanical and thermomechanical tests for thin and very thick plates are presented in order to evaluate the capability of this new finite element to give accurate results with respect to exact three-dimensional solutions. Both convergence velocity and accuracy are discussed and this new finite element yields very satisfactory results at a low computational cost. In particular, the transverse shear stresses computed from the constitutive relation are well estimated with regards to other equivalent single layer or even with respect to layerwise models. © 2012 Elsevier B.V.


Vidal P.,CNRS Mechanical Energy and Electromagnetism Lab | Polit O.,CNRS Mechanical Energy and Electromagnetism Lab
Composites Part B: Engineering | Year: 2011

This paper deals with the influence of the use of the Murakami's zig-zag function in the sine model for the analysis of laminated beams. The adding of this function introduces a discontinuity of the first derivative of the in-plane displacement with only one more unknown. The kinematics is based on a sine distribution and the transverse displacement remains constant through the thickness. The transverse shear strain is obtained using a cosine function avoiding the use of shear correction factors. A conforming FE approach is carried out using Lagrange and Hermite interpolations. It is important to notice that the number of unknowns is independent of the number of layers. The purpose is to develop a finite element approach with a low computational cost and without numerical pathology. This study aims at determining the influence of an additional zig-zag function in the Sine model for static and vibration analysis. In this way, mechanical tests for thin/thick laminated and sandwich beams are presented in order to evaluate the capability of this finite element. The results are compared with elasticity or finite element reference solutions in statics and vibration. Both convergence velocity and accuracy are discussed. This finite element yields satisfactory results at a low computational cost. © 2011 Elsevier Ltd. All rights reserved.


Bruant I.,CNRS Mechanical Energy and Electromagnetism Lab | Gallimard L.,CNRS Mechanical Energy and Electromagnetism Lab | Nikoukar S.,CNRS Mechanical Energy and Electromagnetism Lab
Journal of Sound and Vibration | Year: 2010

This paper deals with the optimization of piezoelectric actuators and sensors locations for active vibration control. Two modified optimization criteria are used, ensuring good observability or controllability of the structure, and considering residual modes to limit the spillover effect. Two optimization variables are considered for each piezoelectric device: the location of its center and its orientation. Genetic algorithms are used to find the optimal configurations. Several simulations are presented for a simply supported plate. © 2009 Elsevier Ltd. All rights reserved.


Lezgy-Nazargah M.,Hakim Sabzevari University | Vidal P.,CNRS Mechanical Energy and Electromagnetism Lab | Polit O.,CNRS Mechanical Energy and Electromagnetism Lab
Composite Structures | Year: 2013

This study deals with static, free vibration and dynamic response of functionally graded piezoelectric material (FGPM) beams using an efficient three-nodded beam element. This beam finite element is based on a refined sinus model. It does not require shear correction factor and ensures continuity conditions for displacements, transverse shear stresses as well as boundary conditions on the upper and lower surfaces of the FGPM beam. This conforming finite element does not suffer from shear locking. The number of the mechanical unknowns is independent of the number of layers. A high-order electrical potential field is considered through each graded piezoelectric layer. The proposed FE is validated through static, free vibration and dynamic tests for FGPM beams. For various electrical and mechanical boundary conditions, excellent agreement is found between the results obtained from the proposed formulation and reference results from open literature or 3D FEM. © 2013 Elsevier Ltd.

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