349 research outputs found
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 dâĂȘtre 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
Vers une posture dâĂ©mancipation du chercheur-praticien quant au soutien Ă la mobilisation des savoirs en Ă©ducation inclusive = Hacia una postura de emancipaciĂłn del investigador con respecto al apoyo a la movilizaciĂłn del conocimiento en la educaciĂłn inclusiva
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 MusĂ©e des beaux-arts de MontrĂ©al dĂ©veloppe une plateforme nommĂ©e ĂducArt, qui suggĂšre des activitĂ©s Ă©ducatives rĂ©alisĂ©es Ă partir de sa collection encyclopĂ©dique pour soutenir les Ă©coles secondaires quĂ©bĂ©coises dans leur mission culturelle. Comme lâĂ©laboration de ressources destinĂ©es au milieu scolaire demande de tenir compte des besoins et des rĂ©alitĂ©s de la classe (Van der Maren, 1996, 2003) et que le gouvernement du QuĂ©bec entend poursuivre le financement de plateformes musĂ©ales (Rocheleau, 2016), il apparaĂźt important dâĂ©tudier les enjeux associĂ©s Ă lâappropriation de ressources numĂ©riques musĂ©ales, telles que celles diffusĂ©es sur la plateforme ĂducArt, par des enseignants du secondaire du QuĂ©bec. Dans cette perspective, un cadre dâanalyse visant Ă mieux comprendre ces enjeux semble essentiel. Cet article se veut une contribution en ce sens, car Ă notre connaissance, aucun modĂšle thĂ©orique nâexiste pour comprendre les enjeux particuliers que rencontrent des enseignants du secondaire lorsquâils tentent de sâapproprier des ressources numĂ©riques musĂ©ales.Since 2014, the Montreal Museum of Fine Arts develops a platform called ĂducArt, 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 Quebecâs 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 ĂducArt 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
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