Numerical Study of Counterflow Diffusion Flame and Water Spray Interaction

This paper reports numerical investigation concerning the interaction of a laminar methane-air counterflow diffusion flame with monodisperse and polydisperse water spray. Commercial code ANSYS FLUENT with reduced chemistry has been used for investigation. Effects of strain rate, Sauter mean diameter (SMD), and droplet size distribution on the temperature along stagnation streamline have been studied. Flame extinction using polydisperse water spray has also been explored. Comparison of monodisperse and polydisperse droplet distribution on flame properties reveals suitability of polydisperse spray in flame temperature reduction beyond a particular SMD. This study also provides a numerical framework to study flame-spray interaction and extinction.

Graphene as a diffusion barrier for isomorphous systems: Cu-Ni system

Electrochemical exfoliation technique using the pyrophosphate anion derived from tetra sodium pyrophosphate was employed to produce graphene. As-synthesized graphene was then drop dried over a cold rolled Cu sheet. Ni coating was then electrodeposited over bare Cu and graphene-Cu substrates. Both substrates were then isothermally annealed at 800 degrees C for 3 h. WDS analysis showed substantial atomic diffusion in annealed Ni-Cu sample. Cu-graphene-Ni sample, on the other hand, showed negligible diffusion illustrating the diffusion barrier property of the graphene coating. (C) 2016 Elsevier B.V. All rights reserved.

Graphene as a diffusion barrier for isomorphous systems: Cu-Ni system

Electrochemical exfoliation technique using the pyrophosphate anion derived from tetra sodium pyrophosphate was employed to produce graphene. As-synthesized graphene was then drop dried over a cold rolled Cu sheet. Ni coating was then electrodeposited over bare Cu and graphene-Cu substrates. Both substrates were then isothermally annealed at 800 degrees C for 3 h. WDS analysis showed substantial atomic diffusion in annealed Ni-Cu sample. Cu-graphene-Ni sample, on the other hand, showed negligible diffusion illustrating the diffusion barrier property of the graphene coating. (C) 2016 Elsevier B.V. All rights reserved.

Boundary knot method for 2D and 3D Helmholtz and convection-diffusion problems under complicated geometry

The boundary knot method (BKM) of very recent origin is an inherently meshless, integration-free, boundary-type, radial basis function collocation technique for the numerical discretization of general partial differential equation systems. Unlike the method of fundamental solutions, the use of non-singular general solution in the BKM avoids the unnecessary requirement of constructing a controversial artificial boundary outside the physical domain. The purpose of this paper is to extend the BKM to solve 2D Helmholtz and convection-diffusion problems under rather complicated irregular geometry. The method is also first applied to 3D problems. Numerical experiments validate that the BKM can produce highly accurate solutions using a relatively small number of knots. For inhomogeneous cases, some inner knots are found necessary to guarantee accuracy and stability. The stability and convergence of the BKM are numerically illustrated and the completeness issue is also discussed.

Laboratory Study on Sediment Diffusion and Deposition into Blind Channels

Any waterway with one end closed and the other open is generally called a blind channel. The main flow tends to expand, separate, and cause circulation at the mouth of blind channels. The main flow continuously transfers momentum and sediment into the circulation region through the turbulent mixing region (TMR) between them, thus leading to a large amount of sediment deposition in the blind channels. This paper experimentally investigated the properties of the water flow and sediment diffusion in TMR, demonstrating that both water flow and sediment motion in TMR approximately coincide with a similar structure as in the free mixing layer induced by a jet. The similarity functions of flow velocity and sediment concentration are then assumed, based on observation, and the resulting calculation of these functions is substantially facilitated. For the kind of low velocity flow system of blind channels with a finite width, a simple formula for the sediment deposition rate in blind channels is established by analyzing the gradient of crosswise velocity and sediment concentration in TMR.

Diffusion mechanisms in the Fe3ASi

In this paper, the possible reasons for the high thermal vacancy concentration and the low migration barriers for the Fe atom diffusion in the DO3 structure Fe3Si have been discussed.

Molecular Dynamics Modeling of Diffusion Bonding

Molecular dynamics simulations on diffusion bonding of Cu-Ag showed that the thickness of the interfacial region depended on the stress. The interfacial region became amorphous during diffusion bonding, and it would normally transform from amorphous into crystalline structure when the structure was cooled to the room temperature.

Effect of diffusion on coating microstructure and oxidation resistance of aluminizing steel

The effect of diffuse treatment on coating microstructure and oxidation resistance at high-temperature of hot-dip aluminum were studied by means of TEM, SEM and XRD. The results show that, the diffusion temperature has significant effect on structure of coatings and its oxidation resistance. After diffusion at 750 degreesC, the coating consists of thick outer surface layer (Fe2Al5+ FeAl2), thin internal layer (FeAl + stripe FeAl2), and its oxidation resistance is poor. After diffusion at 950 degreesC, the outer surface layer is composed of single FeAl2 phase, the internal layer is composed of FeAl phase, and its oxidation resistance declines due to the occurrence of early stage internal oxidation cracks in the coating. After diffusion at 850 degreesC, the outer surface layer becomes thinner and consists of FeAl2 Fe2Al5(small amount), the internal layer becomes thicker and consists of FeAl+spherical FeAl2, and the spheroidized FeAl2 phase in the internal layer and its existing in FeAl phase steadily improve the oxidation resistance of the coating.

Forcing of self-excited round jet diffusion flames

In this experimental and numerical study, two types of round jet are examined under acoustic forcing. The first is a non-reacting low density jet (density ratio 0.14). The second is a buoyant jet diffusion flame at a Reynolds number of 1100 (density ratio of unburnt fluids 0.5). Both jets have regions of strong absolute instability at their base and this causes them to exhibit strong self-excited bulging oscillations at welldefined natural frequencies. This study particularly focuses on the heat release of the jet diffusion flame, which oscillates at the same natural frequency as the bulging mode, due to the absolutely unstable shear layer just outside the flame. The jets are forced at several amplitudes around their natural frequencies. In the non-reacting jet, the frequency of the bulging oscillation locks into the forcing frequency relatively easily. In the jet diffusion flame, however, very large forcing amplitudes are required to make the heat release lock into the forcing frequency. Even at these high forcing amplitudes, the natural mode takes over again from the forced mode in the downstream region of the flow, where the perturbation is beginning to saturate non-linearly and where the heat release is high. This raises the possibility that, in a flame with large regions of absolute instability, the strong natural mode could saturate before the forced mode, weakening the coupling between heat release and incident pressure perturbations, hence weakening the feedback loop that causes combustion instability. © 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Les attributs et contextes d'utilisation du travail collaboratif

Résumé: Le travail collaboratif s’invite à présent partout, et est identifié dans des domaines aussi multiples que variés. Dans le monde de l’entreprise, de la prise en charge médico-sociale, de l’éducation / formation, de la recherche, de l’économie, de la politique, de la gestion de carrière… etc. Ce travail vise dans un premier temps à décliner ce qu’est la collaboration, ses caractéristiques, ses contextes d’utilisation, et la façon dont elle se différencie des autres formes d’organisation (coopération et compétition notamment). Dans un deuxième temps, il réexamine la question de la nouveauté du travail collaboratif à la lumière des résultats obtenus. S’il est assez évident que les « ingrédients », les attributs du travail collaboratif ne sont pas nouveaux (le développement informatique mis à part), il semble en revanche que les combinaisons rencontrées et les domaines d’application génèrent de nouvelles questions. Pour finir, en s’inspirant des termes associés à collaboration, il considère quelques-uns des nouveaux enjeux dans la sphère professionnelle.

Entre Syrie et Mésopotamie : vases zoomorphes du Règne de Mittani

Abstract: The Mittanian zoomorphic vessels from Nuzi, Tell Brak, Tell al-Rimah and other sites allow the creation of a significant database for analysis based on typological criteria as well as spatial distribution. This class of materials is attested in several areas of the ancient Near East from the Late Calcholitic and still produced until the Mittanian age and thereafter. Most of the finds come from temples or domestic contexts and they can be now securely dated, while their spatial distribution can be properly investigated. Lion representations seem to predominate, but pigs and other animals appear as well. The exact function and meaning of these vessels are difficult to ascertain, nevertheless, in most cases, they are probably related to cultic practices performed throughout the Mittanian Empire.

La precarite de l’emploi et ses multiples impacts a la lumière du genre

Résumé: A l’heure où l’on évoque une “génération précaire” il est intéressant de s’interroger sur l’accroissement de la précarité de l’emploi en France et d’étudier ses éventuels effets sur les salariés. L’objectif de la présente recherche était d’observer les impacts causés par la précarité de l’emploi sur une population de référence et voir si ces effets différaient selon le sexe du salarié soumis à la précarité. Pour ce faire, nous avons soumis un questionnaire à deux groupes de travailleurs. Ce dernier portait sur la précarité de l’emploi et ses impacts en termes de stress, consommation de substances et impacts sur la sphère privée. Les résultats font apparaître des effets significatifs et des tendances qui existent sur certaines des dimensions interrogées (stress et consommation) entre le groupe de travailleurs précaires et non précaires. De plus, des effets entre hommes et femmes ont également été relevés. Par contre, nous n’avons pas d’effets observés sur la sphère privée de l’individu. Suite à l’absence d’effet constaté nous interrogeons la spécificité de la population. Aussi, nous envisageons de prolonger cette étude sur la recherche d’indicateurs concernant la précarité enseignante. Mots clés: précarité professionnelle, précarité du travail, précarité de l’emploi, travailleurs précaires, inégalités hommes femmes, stress, substances addictives, impact vie hors travail