EFFECTS STUDY OF SOLID PROTUBERANCES PROPERTIES ON THE TURBULENT NATURAL CONVECTION PERFORMANCE INSIDE A VERTICAL CHANNEL

Dans cette étude, nous présentons des prédictions numériques des effets des propriétés géométriques, physiques et thermiques des protubérances, telles que la conductivité thermique des protubérances solides, les rapports d’aspect et les intensités du flux de chaleur exercées sur les faces externes des protubérances, sur la convection naturelle turbulente dans un canal vertical. Les résultats de l’analyse du transfert de chaleur sont obtenus en solutionnant les équations de l’écoulement de chaleur et des fluides en utilisant le modèle de la turbulence. Le système étudié est bidimensionnel, turbulent et permanant. La procédure numérique étend sur un code numérique qui modélise l’écoulement de chaleur et des fluides. Les résultats sont données en termes des champs et des profils des propriétés locales telles que la température, la vitesse, le coefficient de transfert de chaleur et l’intensité de la turbulence pour différents valeurs du rapport d’aspect des protubérances, la conductivité thermique et le flux de chaleur exercé sur les faces externes des protubérances. Les champs des propriétés d’air physiques et thermiques montrent des comportements différents en fonction de la valeur du rapport d’aspect des protubérances. Un effet positif sur le rendement de la convection naturelle turbulente a été prédit, dans la plage de 0 à 6,5%, par rapport à un canal vertical sans protubérances '. La présence des protubérances c’est un facteur important dans l’amélioration du rendement de la convection naturelle turbulente dans un canal vertical

Existence of naked singularities in Brans-Dicke theory of gravitation. An analytical and numerical study

Within the framework of the scalar-tensor models of gravitation and by relying on analytical and numerical techniques, we establish the existence of a class of spherically symmetric spacetimes containing a naked singularity. Our result relies on and extends a work by Christodoulou on the existence of naked singularities for the Einstein-scalar field equations. We establish that a key parameter in Christodoulou's construction couples to the Brans-Dicke field and becomes a dynamical variable, which enlarges and modifies the phase space of solutions. We recover analytically many properties first identified by Christodoulou, in particular the loss of regularity (especially at the center), and then investigate numerically the properties of these spacetimes.Comment: 26 pages, PACS numbers: 04.20.Dw, 04.25.dc, 04.50.K

Equilibrium configurations from gravitational collapse

We develop here a new procedure within Einstein's theory of gravity to generate equilibrium configurations that result as the final state of gravitational collapse from regular initial conditions. As a simplification, we assume that the collapsing fluid is supported only by tangential pressure. We show that the equilibrium geometries generated by this method form a subset of static solutions to the Einstein equations, and that they can either be regular or develop a naked singularity at the center. When a singularity is present, there are key differences in the properties of stable circular orbits relative to those around a Schwarzschild black hole with the same mass. Therefore, if an accretion disk is present around such a naked singularity it could be observationally distinguished from a disk around a black hole.Comment: 13 pages, 3 figure. Replaced with published version, several changes made according to referee's advis

Between history and values: A study on the nature of interpretation in international law

My thesis discusses the place of evaluative judgements in the interpretation of general international law. It concentrates on two questions. First, whether it is possible to interpret international legal practices without making an evaluative judgement about the point or value that provides the best justification of these practices. Second, whether the use of evaluative judgements in international legal interpretation threatens to undermine the objectivity of international law, the neutrality of international lawyers or the consensual and voluntary basis of the international legal system. I answer both questions in the negative. As regards the first, I argue that international legal practice has an interpretive structure, which combines appeals to the history of international practice with appeals to the principles and values that these practices are best understood as promoting. This interpretive structure is apparent not only in the claims of international lawyers about particular rules of international law (here I use the rule of estoppel as an example) but also in the most basic intuitions of international theorists about the theory and sources of general international law. I then argue that some popular concerns to the effect that the exercise of evaluation in the interpretation of international law will undermine the coherence or the usefulness of the discipline are generally unwarranted. The fact that international legal practice has an interpretive structure does not entail that propositions of international law are only subjectively true, that the interpreter enjoys license to manipulate their meaning for self-serving purposes, or that international law will collapse under the weight of irresolvable disagreements, divisions and conflicts about its proper interpretation

Post-annealed silicon nanocrystal formation on substoichiometric SiO

In this work is presented a detailed physicochemical, structural and optical characterization of SiOxNy thin films. The films deposited using PECVD in SiH4-N2O-He discharges were thermally annealed at 1273 K for 1 hour in ambient nitrogen. The film stochiometry was measured by Rutherford Backscattering Spectroscopy. The chemical composition was dominated by silicon suboxide containing some Si-N and Si-H bonds. Raman scattering measurements suggest the formation of nanocrystallite silicon in the annealed films. The Raman observation is strongly supported by Transmission Electron Microscopy analysis which shows a high density of silicon nanocrystals, having a mean radius ranging between 3 and 6 nm. Using Spectroscopic Ellipsometry, we discussed the dielectric function evolution as a function of the deposition parameters

PECVD nanosilver embedded in organosilicon matrix for prevention of microbial adhesion

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