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École des Ponts ParisTech is a university-level institution of higher education and research in the field of science, engineering and technology.Founded in 1747 as the world's first engineering school, it remains to this day one of the most prestigious and selective French Grandes Écoles. Its historical mission was primarily to train engineering officials and senior civil engineers. The school now offers a wide-ranging education in civil engineering, mechanics, computer science, applied mathematics, finance, economics, urban studies, environment and transport engineering.It is headquartered in Marne-la-Vallée and is a founding member of ParisTech and of the Paris School of Economics.The school is under the Ministry of Ecology, Sustainable Development and Energy. Wikipedia.

Peigney M.,ParisTech National School of Bridges and Roads
Journal of the Mechanics and Physics of Solids | Year: 2013

This paper addresses the theoretical prediction of the quasiconvex hull of energy-minimizing strains that can be realized by martensitic microstructures. Polyconvexification and related notions are used to derive some upper bounds (in the sense of inclusion) on the quasiconvex hull. Lower bounds are constructed by lamination techniques. The geometrically nonlinear theory (finite strains) is considered in the present Part 1. Analytical expressions are obtained for a three-well problem which encompasses the cubic to tetragonal transformation as a special case. Twelve-well problems related to cubic to monoclinic transformations are also studied. In that case, sufficient conditions are derived for the microstructure to be restricted to only two of the 12 wells. © 2013 Elsevier Ltd. Source

Peigney M.,ParisTech National School of Bridges and Roads
Journal of the Mechanics and Physics of Solids | Year: 2013

This paper addresses the theoretical prediction of the quasiconvex hull of energy-minimizing (or stress-free) strains that can be realized by martensitic microstructure. Polyconvexification and related notions are used to derive some upper bounds (in the sense of inclusion) on the quasiconvex hull. Lower bounds are obtained from lamination techniques. The geometrically linear setting (infinitesimal strains) is considered in the present Part 2. Three-, four-, and twelve-well problems are considered. In particular, the structure of the set of energy-minimizing strains in cubic to monoclinic transformations is investigated in detail. That investigation is notably supported by three-dimensional vizualisations obtained by considering four-well restrictions. © 2013 Elsevier Ltd. Source

Nedjar B.,ParisTech National School of Bridges and Roads
International Journal of Solids and Structures | Year: 2011

In this work, a fully three-dimensional constitutive model suitable for the macroscopic description of unidirectional fibre-reinforced composites where the matrix exhibits a time-dependent viscoelastic behavior is developed. Specifically, we consider a coordinate-free formulation where the stress and strain fields can be decomposed into fibre-directional and volumetric parts on the one hand, and into extra contributions on the other hand. This offers an ideal framework where one can separate the fibres' contribution, considered here as time-independent and linearly elastic, and the matrix contribution that experiences creep only in shear. Among the many possibilities, we choose in this work a generalized Kelvin-Voigt rheological model to formulate the viscoelastic behavior of the matrix. Long-term as well as short-term relaxation processes can be integrated in the model by means of as many as necessary viscoelastic processes. The numerical discretization is described for an easy integration within a finite element procedure. Finally, numerical examples illustrate the possibilities of the present model. © 2011 Elsevier Ltd. All rights reserved. Source

Gabillet P.,ParisTech National School of Bridges and Roads
Energy Policy | Year: 2015

Through the analysis of energy supply choices, this article explores the way in which energy priorities and their climate-related features are incorporated into urban public policy. These choices must take account of different factors, as is the case with district heating, which is justified as a vehicle of renewable energy while subject to pressure in eco-districts because its techno-economic balances are destabilised by falls in demand. Our study focuses particularly on the city of Metz (France), which has chosen district heating as the primary source for provision for the municipal area and for its first eco-district. We analyse the tensions within these choices, with particular attention to the way in which they are negotiated inside municipal departments and with the local energy operator. This enables us to explore the tensions in defining the scale that governs decisions and the linkages between energy-related and urban priorities. © 2014 Elsevier Ltd. Source

Bocquet M.,ParisTech National School of Bridges and Roads | Bocquet M.,French Institute for Research in Computer Science and Automation
Quarterly Journal of the Royal Meteorological Society | Year: 2012

Atmospheric chemistry and air-quality numerical models are driven by uncertain forcing fields: emissions, boundary conditions, wind fields, vertical turbulent diffusivity, kinetic chemical rates, etc. Data assimilation can help to assess these parameters or fields of parameters. Because such parameters are often much more uncertain than the fields diagnosed in meteorology and oceanography, data assimilation is much more of an inverse modelling challenge in this context. In this article these ideas are experimented with by revisiting the Chernobyl accident dispersion event over Europe. A fast four-dimensional variational scheme (4D-Var) is developed, which seems appropriate for the retrieval of large parameter fields from large observation sets and the retrieval of parameters that are nonlinearly related to concentrations. The 4D-Var, and especially an approximate adjoint of the transport model, is tested and validated using several advection schemes that are influential on the forward simulation as well as on the data-assimilation results. Firstly, the inverse modelling system is applied to the assessment of the dry and wet deposition parameters. It is then applied to the retrieval of the emission field alone, the joint optimization of removal-process parameters and source parameters and the optimization of larger parameter fields such as horizontal and vertical diffusivities or the dry-deposition velocity field. The physical parameters used so far in the literature for the Chernobyl dispersion simulation are partly supported by this study. The crucial question of deciding whether such an inversion is merely a tuning of parameters or a retrieval of physically meaningful quantities is discussed. Even though inversion of parameter fields may fail to determine physical values for the parameters, it achieves statistical adaptation that partially corrects for model errors and, using the inverted parameter fields, leads to considerable improvement in the simulation scores. © 2011 Royal Meteorological Society. Source

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