The Experts below are selected from a list of 5157 Experts worldwide ranked by ideXlab platform
J. H. Field - One of the best experts on this subject based on the ideXlab platform.
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Translational Invariance and the space-time Lorentz transformation with arbitrary spatial coordinates
arXiv: General Physics, 2007Co-Authors: J. H. FieldAbstract:Translational Invariance requires that physical predictions are independent of the choice of spatial coordinate system used. The time dilatation effect of special relativity is shown to manifestly respect this Invariance. Consideration of the space-time Lorentz transformation with arbitrary spatial coordinates shows that the spurious `length contraction' and `relativity of simultaneity' effects --the latter violating Translational Invariance-- result from the use of a different spatial coordinate system to describe each of two spatially separated clocks at rest in a common inertial frame
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The Local Space-Time Lorentz Transformation: a New Formulation of Special Relativity Compatible with Translational Invariance
arXiv: General Physics, 2005Co-Authors: J. H. FieldAbstract:The apparent times and positions of moving clocks as predicted by both `non-local' and `local' Lorentz Transformations are considered. Only local transformations respect Translational Invariance. Such transformations change temporal but not spatial intervals, so breaking space-time exchange symmetry and forbidding relativity of simultaneity and length contraction. Two satellite-borne experiments to test these predictions are proposed.
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The Space-Time Lorentz Transformation: Relativity of Simultaneity is Incompatible with Translational Invariance
arXiv: General Physics, 2004Co-Authors: J. H. FieldAbstract:Observations of the apparent times and positions of moving clocks as predicted by both `non-local' and `local' Lorentz Transformations are considered. Only local transformations respect Translational Invariance. Such transformations change temporal but not spatial intervals, so breaking space time exchange symmetry and forbidding relativity of simultaneity and length contraction. A satellite cesium clock experiment to test these predictions is proposed.
Fabien Treyssede - One of the best experts on this subject based on the ideXlab platform.
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Numerical modeling of waveguides accounting for Translational Invariance and rotational symmetry
2017Co-Authors: Fabien TreyssedeAbstract:The analysis of high-frequency wave propagation in arbitrarily shaped waveguides requires specific numerical methods. A widely spread technique is the so-called semi-analytical finite element (SAFE) formulation. This formulation enables to account for the Translational Invariance of waveguide problems and leads to a two-dimensional modal problem reduced on the cross-section. Despite this, solving the problem can still be computationally demanding. In order to further reduce the size of the modal problem, this paper presents a SAFE method for waveguides of rotationally symmetric cross-sections. Such structures are encountered in many applications. Typical examples are bars of circular cross-section, regular polygons, and multiwire cables. Numerical results show that the computational effort required for solving the SAFE modal problem is tremendously reduced by accounting for rotational symmetry.
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mechanical modeling of helical structures accounting for Translational Invariance part 2 guided wave propagation under axial loads
International Journal of Solids and Structures, 2013Co-Authors: Fabien Treyssede, Ahmed Frikha, Patrice CartraudAbstract:This paper corresponds to the second part of a study that aims at modeling helical structures accounting for Translational Invariance. In the Part 1 of this paper, the static behavior has been addressed using a helical homogenization approach which provides the stress state corresponding to axial loads. The latter is considered as a prestressed state, for elastic wave propagation analysis in helical waveguides, which is the subject of the Part 2 of this paper. Non destructive testing of springs and multi-wire strands is a potential application of the proposed model. Accounting for Translational Invariance, the elastodynamic equations of prestressed helical structures yield a 2D problem posed on the cross-section, corresponding to a so-called semi-analytical finite element (SAFE) formulation. For helical springs, the numerical model is validated with an analytical solution corresponding to a Timoshenko beam approximation. It is shown that the influence of the prestressed state is significant at low frequencies. Finally, a seven-wire strand subjected to axial loads is considered. The computed dispersion curves are compared to experimental data. Good agreement is obtained for the first compressional-like modes and their veering central frequency.
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Mechanical modeling of helical structures accounting for Translational Invariance. Part 1: Static behavior
International Journal of Solids and Structures, 2013Co-Authors: Ahmed Frikha, Patrice Cartraud, Fabien TreyssedeAbstract:The purpose of this paper is to investigate the static behavior of helical structures under axial loads. Taking into account their Translational Invariance, the homogenization theory is applied. This approach, based on asymptotic expansion, gives the first-order approximation of the 3D elasticity problem from the solution of a 2D microscopic problem posed on the cross-section and a 1D macroscopic problem, which turns out to be a Navier-Bernoulli-Saint-Venant beam problem. By contrast with earlier references in which a reduced 3D model was built on a slice of the helical structure, the contribution of this paper is to propose a 2D microscopic model. Homogenization is first applied to helical single wire structures, i.e. helical springs. Next, axial elastic properties of a seven-wire strand are computed. The approach is validated through comparison with reference results: analytical solution for helical single wire structures and 3D detailed finite element solution for seven-wire strands.
Patrice Cartraud - One of the best experts on this subject based on the ideXlab platform.
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mechanical modeling of helical structures accounting for Translational Invariance part 2 guided wave propagation under axial loads
International Journal of Solids and Structures, 2013Co-Authors: Fabien Treyssede, Ahmed Frikha, Patrice CartraudAbstract:This paper corresponds to the second part of a study that aims at modeling helical structures accounting for Translational Invariance. In the Part 1 of this paper, the static behavior has been addressed using a helical homogenization approach which provides the stress state corresponding to axial loads. The latter is considered as a prestressed state, for elastic wave propagation analysis in helical waveguides, which is the subject of the Part 2 of this paper. Non destructive testing of springs and multi-wire strands is a potential application of the proposed model. Accounting for Translational Invariance, the elastodynamic equations of prestressed helical structures yield a 2D problem posed on the cross-section, corresponding to a so-called semi-analytical finite element (SAFE) formulation. For helical springs, the numerical model is validated with an analytical solution corresponding to a Timoshenko beam approximation. It is shown that the influence of the prestressed state is significant at low frequencies. Finally, a seven-wire strand subjected to axial loads is considered. The computed dispersion curves are compared to experimental data. Good agreement is obtained for the first compressional-like modes and their veering central frequency.
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Mechanical modeling of helical structures accounting for Translational Invariance. Part 1: Static behavior
International Journal of Solids and Structures, 2013Co-Authors: Ahmed Frikha, Patrice Cartraud, Fabien TreyssedeAbstract:The purpose of this paper is to investigate the static behavior of helical structures under axial loads. Taking into account their Translational Invariance, the homogenization theory is applied. This approach, based on asymptotic expansion, gives the first-order approximation of the 3D elasticity problem from the solution of a 2D microscopic problem posed on the cross-section and a 1D macroscopic problem, which turns out to be a Navier-Bernoulli-Saint-Venant beam problem. By contrast with earlier references in which a reduced 3D model was built on a slice of the helical structure, the contribution of this paper is to propose a 2D microscopic model. Homogenization is first applied to helical single wire structures, i.e. helical springs. Next, axial elastic properties of a seven-wire strand are computed. The approach is validated through comparison with reference results: analytical solution for helical single wire structures and 3D detailed finite element solution for seven-wire strands.
Ahmed Frikha - One of the best experts on this subject based on the ideXlab platform.
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mechanical modeling of helical structures accounting for Translational Invariance part 2 guided wave propagation under axial loads
International Journal of Solids and Structures, 2013Co-Authors: Fabien Treyssede, Ahmed Frikha, Patrice CartraudAbstract:This paper corresponds to the second part of a study that aims at modeling helical structures accounting for Translational Invariance. In the Part 1 of this paper, the static behavior has been addressed using a helical homogenization approach which provides the stress state corresponding to axial loads. The latter is considered as a prestressed state, for elastic wave propagation analysis in helical waveguides, which is the subject of the Part 2 of this paper. Non destructive testing of springs and multi-wire strands is a potential application of the proposed model. Accounting for Translational Invariance, the elastodynamic equations of prestressed helical structures yield a 2D problem posed on the cross-section, corresponding to a so-called semi-analytical finite element (SAFE) formulation. For helical springs, the numerical model is validated with an analytical solution corresponding to a Timoshenko beam approximation. It is shown that the influence of the prestressed state is significant at low frequencies. Finally, a seven-wire strand subjected to axial loads is considered. The computed dispersion curves are compared to experimental data. Good agreement is obtained for the first compressional-like modes and their veering central frequency.
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Mechanical modeling of helical structures accounting for Translational Invariance. Part 1: Static behavior
International Journal of Solids and Structures, 2013Co-Authors: Ahmed Frikha, Patrice Cartraud, Fabien TreyssedeAbstract:The purpose of this paper is to investigate the static behavior of helical structures under axial loads. Taking into account their Translational Invariance, the homogenization theory is applied. This approach, based on asymptotic expansion, gives the first-order approximation of the 3D elasticity problem from the solution of a 2D microscopic problem posed on the cross-section and a 1D macroscopic problem, which turns out to be a Navier-Bernoulli-Saint-Venant beam problem. By contrast with earlier references in which a reduced 3D model was built on a slice of the helical structure, the contribution of this paper is to propose a 2D microscopic model. Homogenization is first applied to helical single wire structures, i.e. helical springs. Next, axial elastic properties of a seven-wire strand are computed. The approach is validated through comparison with reference results: analytical solution for helical single wire structures and 3D detailed finite element solution for seven-wire strands.
D. Zappalà - One of the best experts on this subject based on the ideXlab platform.
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Spontaneous breaking of Translational Invariance in noncommutative {lambda}{phi}{sup 4} theory in two dimensions
Physical Review D, 2008Co-Authors: P. Castorina, D. ZappalàAbstract:The spontaneous breaking of Translational Invariance in noncommutative self-interacting scalar field theory in two dimensions is investigated by effective action techniques. The analysis confirms the existence of the stripe phase, already observed in lattice simulations, due to the nonlocal nature of the noncommutative dynamics.
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spontaneous breaking of Translational Invariance in noncommutative lambda phi sup 4 theory in two dimensions
Physical Review D, 2008Co-Authors: P. Castorina, D. ZappalàAbstract:The spontaneous breaking of Translational Invariance in noncommutative self-interacting scalar field theory in two dimensions is investigated by effective action techniques. The analysis confirms the existence of the stripe phase, already observed in lattice simulations, due to the nonlocal nature of the noncommutative dynamics.
