Dassault Aviation

About: Dassault Aviation is a company organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Aerodynamics. The organization has 564 authors who have published 645 publications receiving 11000 citations. The organization is also known as: Dassault.

Numerical simulation and optimal shape for viscous flow by a fictitious domain method

Abstract: In this article we discuss the fictitious domain solution of the Navier-Stokes equations modelling unsteady incompressible viscous flow. The method is based on a Lagrange multiplier treatment of the boundary conditions to be satisfied and is particularly well suited to the treatment of no-slip boundary conditions. This approach allows the use of structured meshes and fast specialized solvers for problems on complicated geometries. Another interesting feature of the fictitious domain approach is that it allows the solution of optimal shape problems without regriding. The resulting methodology is applied to the solution of flow problems including external incompressible viscous flow modelled by the Navier-Stokes equations and then to an optimal shape problem for Stokes and Navier-Stokes flow

Preparation, characterization and properties of sputtered electrochromic and thermochromic devices

Abstract: The interest in electrochromic materials has increased in the last few years because of their applications in a wide variety of optical modulation devices including smart windows for solar control in the architectural and automotive sectors and flat panel displays. Thermochromic coatings which reduce the transmission of solar energy as the temperature rises can prevent overheating and find application in the thermal control of buildings, satellites and spatial equipements. This article reports on the optical and structural properties of RF sputtered thin films of WO3 and VO2 for electrochromic and thermochromic devices.

Ferromagnetic resonance spectra in a weak stripe domain structure

Abstract: The ferromagnetic resonance (FMR) spectra in magnetic films with a nonuniform magnetization configuration are known to exhibit multiple absorption peaks. In this paper, the case of ferromagnetic films supporting a weak stripe domain structure is addressed. A two-dimensional dynamic micromagnetic model is used to investigate the high-frequency response of such a magnetic structure. In a first step, the zero-field susceptibility spectra are computed. The existence of numerous resonances resulting from the excitation of surface and volume modes is predicted. The main features of spectra (number of resonances, resonance frequencies, intensities, and linewidths) strongly depend on the equilibrium spin configuration and on the rf exciting field orientation. In a second step, the susceptibility spectra in the presence of an in-plane static magnetic field applied along the stripe direction are studied in detail. The dispersion relation, frequency versus in-plane magnetic field, is computed for each magnetic excitation. These dispersion curves reveal possible mode couplings and interchange of mode characters with increasing magnetic field. The theoretical in-plane FMR spectra are then deduced from the frequency and magnetic field dependence of the dynamic susceptibility. These theoretical results are discussed in light of available experimental FMR data obtained on thin ferromagnetic films with a moderate perpendicular anisotropy.

Pointwise control of the Burgers equation and related Nash equilibrium problems: computational approach

Abstract: This article is concerned with the numerical solution of multiobjective control problems associated with nonlinear partial differential equations and more precisely the Burgers equation. For this kind of problems, we look for the Nash equilibrium, which is the solution to a noncooperative game. To compute the solution of the problem, we use a combination of finite-difference methods for the time discretization, finite-element methods for the space discretization, and a quasi-Newton BFGS algorithm for the iterative solution of the discrete control problem. Finally, we apply the above methodology to the solution of several tests problems. To be able to compare our results with existing results in the literature, we discuss first a single-objective control problem, already investigated by other authors. Finally, we discuss the multiobjective case.

Mining the Content of Relational Databases to Learn Ontologies with Deeper Taxonomies

Abstract: Relational databases are valuable sources for ontology learning. Previous work showed how precise ontologies can be learned from such structured input. However, a major persisting limitation of the existing approaches is the derivation of ontologies with flat structure that simply mirror the schema of the source databases. In this paper, we present the RTAXON learning method that shows how the content of the databases can be exploited to identify categorization patterns from which class hierarchies can be generated. This fully formalized method combines a classical schema analysis with hierarchy mining in the data. RTAXON is one of the methods implemented in the RDBToOnto tool.