ParisTech

About: ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Residual stress. The organization has 1888 authors who have published 1965 publications receiving 55532 citations. The organization is also known as: Paris Institute of Technology & ParisTech Développement.

Success and failure of adaptation-diffusion algorithms for consensus in multi-agent networks

Abstract: This paper investigates the problem of distributed stochastic approximation in multi-agent systems. The algorithm under study consists of two steps: a local stochastic approximation step and a gossip step which drives the network to a consensus. The gossip step uses row-stochastic matrices to weight network exchanges. We first prove the convergence of a distributed optimization algorithm, when the function to optimize may not be convex and the communication protocol is independent of the observations. In that case, we prove that the average estimate converges to a consensus; we also show that the set of limit points is not necessarily the set of the critical points of the function to optimize and is affected by the Perron eigenvector of the mean-matrix describing the communication protocol. Discussion about the success or failure of convergence to the minimizers of the function to optimize is also addressed. In a second part of the paper, we extend the convergence results to the more general context of distributed stochastic approximation.

Reducing CPU Time for Radiative Exchange and Transient Heat Transfer Analysis Using Zone Method

Abstract: CPU time for radiative heat transfer analysis using the zone method is greatly reduced. Reduction in CPU time is attributed to the development of a simplified version of the plating algorithm for calculation of total exchange areas (TEAs) and of a model reduction algorithm for eliminating low-energy-level exchange areas from the matrix of radiative transfer. The accuracy and efficiency of the algorithms are examined for a windscreen bending furnace and a gas quenching chamber. Total CPU time is reduced by a factor of 17 for both applications.

Characterisation of R.F. magnetron sputtered Cr-N, Cr-Zr-N and Zr-N coatings

Abstract: Binary Cr-N, Zr-N and Cr-Zr-N films were synthesised using a R.F. reactive magnetron sputtering technique by co-sputtering Cr and Zr. The crystalline structure, morphology, mechanical and tribological properties of the films as a function of Zr content were characterised by X-ray diffraction, microanalysis X (WDS, EDS), X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, nanoindentation, scratch adhesion and pin-on-disc sliding wear tests. The residual stress was calculated with the Stoney formula. The Cr-Zr-N films exhibit a two-phase microstructure, containing a cubic (CrN, ZrN) with hexagonal (Cr2N, Zr2N) phases, as shown by X-ray diffraction. As the Zr content increased, a columnar and compact structure is developed with a low surface roughness. The results reveal that the mechanical and tribological properties of the films were found to depend on the Zr content and the hardness (maximum 26.3 GPa) is greatly improved in comparison with CrN and ZrN films, especially...