A comprehensive insight in the MOCVD of aluminum through interaction between reactive transport modeling and targeted growth experiments

Growth experiments and reactive transport modeling were combined to formulate a comprehensive predictive model for aluminum growth from dimethylethylamine alane. The growth-rate profile was experimentally investigated as a function of substrate temperature. The reactive transport model, built under the computational fluid dynamics software PHOENICS, was used to reproduce the experimental measurements and to contribute to the understanding of the aluminum growth process, under sub-atmospheric pressure conditions. The growth mechanism of aluminum films was based on well established in literature reaction order and activation energy of homogeneous and heterogeneous chemical reactions. The reactive transport model was used further to investigate the effect of some key operating parameters on the process output. Simulation results are suggestive of modifications in the operating parameters that could enhance the growth rate and the spatial uniformity of the film thickness

Shape optimization of a showerhead system for the control of growth uniformity in a MOCVD reactor using CFD-based evolutionary algorithms

A steady state, laminar flow coupled with heat transfer, gas-phase and surface chemistry, is numerically solved for the optimal design of a showerhead gas delivery system in an axis-symmetrical MOCVD reactor. The design method involves an evolutionary algorithm based on CFD simulations. A finite-volume CFD code for aluminum growth provides the numerical predictions of the growth rate and its spatial variation over the substrate. A multilevel evolutionary algorithm is used to continuously adjust the shape of the shower plate so as to minimize the spatial variation of the growth rate. A 5-variable parameterization of the shower plate is investigated and a near-optimal solution is proposed and compared to the original configuration of the shower plate

Virginia Satir : le risque d’être soi

L'auteure présente la pensée de Virginia Satir.The author presents Virginia Satir

Reaction and Transport Interplay in Al MOCVD Investigated Through Experiments and Computational Fluid Dynamic Analysis

An improved reactive transport model of a metallorganic chemical vapor deposition process for the growth of aluminum films from dimethylethylamine alane is developed. The computational fluid dynamics model is built under PHOENICS software for the simulation of the coupled fluid flow, heat transfer, and chemistry. The growth mechanism of aluminum films is based on wellestablished, in the literature, reaction order and activation energy of gas-phase and surface reactions. The improvement of the model against a simplified model is established. The interplay of reaction and transport is elucidated. In particular, the important effects of the gas-phase reaction and of the showerhead system are revealed; accounting for gas-phase along with surface reactions for the flow details in the showerhead and for the three-dimensional geometry induced by the distribution of the holes in the showerhead yields substantial enhancement of the predictive capability of the model. The satisfactory agreement between model predictions and growth-rate measurements allows one to understand and improve the process. The model is further used to investigate the effect of key operating parameters on the characteristics of the aluminum films. Simulation results are suggestive of modifications in the operating parameters that could enhance the growth rate and its spatial uniformity

A generalized empirical interpolation method : application of reduced basis techniques to data assimilation

In an effort to extend the classical lagrangian interpolation tools, new interpolating methods that use general interpolating functions are explored. The method analyzed in this paper, called Generalized Empirical Interpolation Method (GEIM), belongs to this class of new techniques. It generalizes the plain Empirical Interpolation Method by replacing the evaluation at interpolating points by application of a class of interpolating linear functions. The paper is divided into two parts: first, the most basic properties of GEIM (such as the well-posedness of the generalized interpolation problem that is derived) will be analyzed. On a second part, a numerical example will illustrate how GEIM, if considered from a reduced basis point of view, can be used for the real-time reconstruction of experiments by coupling data assimilation with numerical simulations in a domain decomposition framework

A weighted reduced basis method for parabolic PDEs with random data

This work considers a weighted POD-greedy method to estimate statistical outputs parabolic PDE problems with parametrized random data. The key idea of weighted reduced basis methods is to weight the parameter-dependent error estimate according to a probability measure in the set-up of the reduced space. The error of stochastic finite element solutions is usually measured in a root mean square sense regarding their dependence on the stochastic input parameters. An orthogonal projection of a snapshot set onto a corresponding POD basis defines an optimum reduced approximation in terms of a Monte Carlo discretization of the root mean square error. The errors of a weighted POD-greedy Galerkin solution are compared against an orthogonal projection of the underlying snapshots onto a POD basis for a numerical example involving thermal conduction. In particular, it is assessed whether a weighted POD-greedy solutions is able to come significantly closer to the optimum than a non-weighted equivalent. Additionally, the performance of a weighted POD-greedy Galerkin solution is considered with respect to the mean absolute error of an adjoint-corrected functional of the reduced solution.Comment: 15 pages, 4 figure

Les enjeux associés à l'appropriation de ressources numériques muséales par des enseignants du secondaire du Québec : proposition d'un cadre d'analyse

Depuis 2014, le Musée des beaux-arts de Montréal développe une plateforme nommée ÉducArt, qui suggère des activités éducatives réalisées à partir de sa collection encyclopédique pour soutenir les écoles secondaires québécoises dans leur mission culturelle. Comme l’élaboration de ressources destinées au milieu scolaire demande de tenir compte des besoins et des réalités de la classe (Van der Maren, 1996, 2003) et que le gouvernement du Québec entend poursuivre le financement de plateformes muséales (Rocheleau, 2016), il apparaît important d’étudier les enjeux associés à l’appropriation de ressources numériques muséales, telles que celles diffusées sur la plateforme ÉducArt, par des enseignants du secondaire du Québec. Dans cette perspective, un cadre d’analyse visant à mieux comprendre ces enjeux semble essentiel. Cet article se veut une contribution en ce sens, car à notre connaissance, aucun modèle théorique n’existe pour comprendre les enjeux particuliers que rencontrent des enseignants du secondaire lorsqu’ils tentent de s’approprier des ressources numériques muséales.Since 2014, the Montreal Museum of Fine Arts develops a platform called ÉducArt, which offers educational activities carried out from its encyclopaedic collection to support Quebec high schools in their cultural mission. As the development of such resources for schools requires consideration of the class needs and realities (Van der Maren, 1996; 2003) and Quebec’s government intends to continue financing museum platforms (Rocheleau, 2016), it appears important to study the issues associated with the appropriation of digital museum resources, such as those published on the ÉducArt platform, by high school teachers in Quebec. In this context, an analytical framework to better understand these issues seems essential. This article is intended to be a contribution in this direction because, to our knowledge, no theoretical model exists in order to specifically understand the issues encountered by high school teachers when trying to appropriate digital museum resources

Drosophila errantiviruses

Retroelements with long-terminal repeats (LTRs) inhabit nearly all eukaryotic genomes. During the time of their rich evolutionary history they have developed highly diverse forms, ranging from ordinary retrotransposons to complex pathogenic retroviruses such as HIV-I. Errantiviruses are a group of insect endogenous LTR elements that share structural and functional features with vertebrate endogenous retroviruses. The errantiviruses illustrate one of the evolutionary strategies of retrotransposons to become infective, which together with their similarities to vertebrate retroviruses make them an attractive object of research promising to shed more light on the evolution of retroviruses

Why do we need a theory and metrics of technology upgrading?

This paper discusses why we need theory and metrics of technology upgrading. It critically reviews the existing approaches to technology upgrading and motivates build-up of theoretically relevant but empirically grounded middle level conceptual and statistical framework which could illuminate a type of challenges relevant for economies at different income levels. It conceptualizes technology upgrading as three dimensional processes composed of intensity and different types of technology upgrading through various types of innovation and technology activities; broadening of technology upgrading through different forms of technology and knowledge diversification, and interaction with global economy through knowledge import, adoption and exchange. We consider this to be necessary first step towards theory and metrics of technology upgrading and generation of more relevant composite indicator of technology upgrading