Versatile Analytical Approach for Assessing Harmonic Distortion in Current-Driven Electrodynamic Loudspeakers

International audienceCurrent-driven loudspeakers have been studied for a long time because they are in great demand by discriminating audiophiles. The latest market research provides clear motivation for producing adequate innovative designs and simple theoretical solutions to address the nonlinear properties of these loudspeakers. Thus, the aim of this paper is to present a compact analytical approach to assess the harmonic distortion that deteriorates the audio quality of electrodynamic loudspeakers, while separately considering the effect of varying the primary respective parameters. Taylor polynomials are conveniently used to derive simple expressions for the first five harmonic distortion lines of the entire spectrum: the significance of each parameter under consideration is rendered transparent using this methodology. This analytical approach is validated by performing a numerical analysis using Simulink software and can easily be implemented using a standard spreadsheet application. We also note that the acceleration of the diaphragm is referenced to the acceleration due to gravity in this study

Mesure de flux de chaleur dans un réfrigérateur thermoacoustique miniature.

Dans le cadre de la miniaturisation de systèmes thermoacoustiques réfrigérants, un démonstrateur de dimension réduite, muni d'un couple stack-échangeurs de chaleur, qui vise à refroidir un liquide jusqu'à son changement de phase, a été construit. L'évolution temporelle de la température et le flux de chaleur transverse sont mesurés à l'aide de microcapteurs spécifiquement développés. Les premiers résultats expérimentaux sont présentés

Application des methodes de la theorie du signal a la dissociation des energies en regime variable

SIGLECNRS T 57220 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Effective electro-optic constants of free-standing superlattices of any symmetry

International audienceA general framework describing the effective electro-optic constants of an idealized free-standing superlattice, composed of thin alternating layers is derived, as a function of the dielectric and electro-optic constants of each of the N constituents. The proposed model is valid only if the energy of light is small compared to the gap of each materials. The results are applied to superlattices with layers of all classes of all symmetries (triclinic, monoclinic, orthorhombic, hexagonal, tetragonal, and cubic)

Tensorial mathematic formulation for the generalization of effective dielectric concept in electromagnetism: superlattices of any symmetry with one and two directions of periodicity

International audienceI introduce a new theoretical formulation based on a composition method and a statistical discretization approach by matrical block so as to shape analytical expressions of effective dielectric tensors of superlattices (SLs) in electromagnetism by considering anisotropic properties and boundary conditions. Such a general framework describing the effective dielectric tensors of idealized free-standing SLs possessing respectively one and two directions of periodicity (1D-SLs and 2D-SLs), composed of thin alternating layers and bars of any symmetry is derived, as a function of the dielectric tensors of each of the N and (N £M) constituents. For the case of 1D-SLs of any symmetry, it is possible to unify and to infer from such global formulation the particular relationships on effective dielectric tensors known as the 'Vegard rules' in solid state physics. Moreover, it is worth noting that in the simpli¯ed case of a 2D-SL made of only two different isotropic materials showing of the same periodicity in both directions, our general matrix formulation, due to the alternative composition laws, leads to the well-established results called, respectively, 'Wiener's and Lichtenecker's bounds' regarding the dielectric constants. This new formalism refashions the concept of bounds of effective dielectric tensors and the notion of form birefringence applied to 1D- and 2D-SLs, with respectively relevant N multilayers and (N £ M) rectangular anisotropic columns for arbitrary symmetries. The results are applied to SLs with layers of all classes of all symmetries (triclinic, monoclinic, orthorhombic, hexagonal, tetragonal, and cubic)

Matrix formalism to enhance the concept of effective dielectric constant

International audienceBy using a matrix formalism, a general framework describing the effective permittivity constants of an idealized free-standing superlattice (SL), composed of thin alternating layers is derived, as a function of the dielectric tensor of each of the N constituents. The versatile results are applied to superlattices with layers of all classes of the whole set of symmetries (triclinic, monoclinic, orthorhombic, hexagonal, tetragonal and cubic). Such an approach leads to only three new general prevalent laws for working out the whole dielectric tensor of any superlattice featuring N constituents of any symmetry. Moreover it is of noteworthy interest that such laws can be formulated as one general relationship related to the ‘Vegard rules’ in solid state physics

Theoretical investigations on the effective electro-optic tensors of superlattices

International audienceIn a recent paper (Bêche and Gaviot 2002 Phys. Rev. B 65 033303), a matrix formalism designed to enhance the concept of effective electro-optic tensors in superlattices (SL) allowed us to derive a general matrix expression describing the electro-optic effect in an idealized free-standing SL. Starting from this matrix equation, we have now developed new general analytical expressions for each term of the effective electro-optic tensors of SL of any symmetry. It is relevant that we obtain only six analytical laws that just depend on the number of occurrences of the index '3', which corresponds to the direction perpendicular to the layers, respectively with both other indices that are in contraction or with the third index of the tensor

A new formulation to shape the concept of bounds in effective dielectric tensors for two directions periodicity

International audienceThis paper introduces a new theoretical formulation based on a composition method and a statistical discretization approach by matrical block. Anisotropic properties and boundary conditions are considered, introducing the analytical bounds expressions of the effective dielectric constants in the limit of the long-wavelength regime for an idealized superlattice (SL) possessing two directions of periodicity (2D-SL). Such a SL can be described as a multilayer array of alternating cells, (N × M) rectangular dielectric bars, allowing the structure to be shaped as a function of the dielectric constants of each of the anisotropic constituents. It is worth noting that in the simplified case of a 2D-SL made of only two different isotropic materials showing off the same periodicity in both directions, our general matrix formulation, due to the alternative composition laws, leads to the well-established results called, respectively, 'Wiener's and Lichtenecker's bounds' regarding the dielectric constant. This new formalism refashions the concept of bounds of effective dielectric tensors and the notion of form birefringence applied to 2D-SL, with relevant (N × M) rectangular anisotropic columns for arbitrary symmetries in the low-frequency model

Variational Method to Shape Analytical Expressions of Time Dependent Eigenvalue Equations: Slab Waveguides Families

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A general expression of the effective electro-optic constants of free standing superlattices

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