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La microfluidique à goutte a connu un essor remarquable ces dix dernières années. Pourtant, la dynamique de ces objets reste largement inexplorée et incomprise. En effet, une question aussi fondamentale que de prédire la vitesse d'une goutte poussée par une phase porteuse à vitesse imposée, est restée jusqu’à ce jour, sans réponse. Comprendre la dynamique d'une goutte suppose de caractériser les dissipations visqueuses (friction) au sein de la goutte et dans le film de lubrification. Ces dissipations visqueuses sont étroitement liées à la forme et aux propriétés physico-chimiques de l'interface séparant l'intérieur de la goutte de la phase externe. Ce manuscrit présente une caractérisation de la dynamique d’une goutte 2D en cellule de Hele-Shaw en exploitant la double mesure du film de lubrification par microscopie interférentielle et de la vitesse de la goutte. Dans un premier temps, nous étudions expérimentalement la forme adoptée par l'interface en fonction de la viscosité de la goutte et de la concentration en tensioactifs. La comparaison des topographies expérimentales mesurées avec des modèles théoriques déjà existants et un nouveau développé dans ce manuscrit, révèle que l'utilisation d'une approche purement hydrodynamique (sans effet Marangoni) pour déterminer la topographie théorique n'est en mesure de reproduire la topographie expérimentale que lorsque le système ne présente pas de tensioactif ou bien lorsque la viscosité de la goutte est suffisamment importante pour prendre le pas sur d'éventuels effets Marangoni à l'interface. Dans les autres cas, la forment de l'interface évolue en fonction de la contrainte de Marangoni qui peut s'exercer localement ou globalement à l'interface. Dans un deuxième temps, l’établissement d’un modèle théorique pour la vitesse de la goutte, basé sur la modélisation des topographies de films expérimentales mesurées, permet de retrouver quantitativement, et sans paramètre d'ajustement, les vitesses de goutte mesurées expérimentalement. / Droplet microfluidics is a growing field of research. However, the dynamics of these objects remain misunderstood. Indeed, a question as fundamental as predicting the droplet velocity while pushed by an external fluid at a given velocity is still not answered. Understanding the dynamics of a droplet requires to characterize the viscous dissipation mechanisms (friction) within the droplet and in the lubrication film. This dissipation is related to the shape and to the physicochemical properties of the interface separating the inner phase of the droplet from the outer phase. This thesis presents a characterization of the dynamics of 2D droplets in a Hele-Shaw cell, by taking advantage of the double measurement of the lubrication film by interference microscopy and of the droplet velocity. Firstly, we study experimentally the influence of the droplet viscosity and surfactant concentration on the shape of the interface. The comparison between the topographies measured experimentally with the theoretical models already existing and the new one developed in this thesis, reveals that the use of a purely hydrodynamical approach in order to derive the theoretical topography only allows to recover the experimental topography if the system is surfactant free or if the droplet viscosity is high enough to overcome the Marangoni effect at the interface. In the other cases, the shape of the interface depends on the Marangoni stress exerted either locally or globally at the interface of the droplet. In a second part, the derivation of a theoretical model for the droplet velocity, based on the modeling of the lubrication film topographies measured experimentally, allows to recover quantitatively, and without any fitting parameter, the experimental data on droplet velocities.

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La digitation visqueuse est une instabilité hydrodynamique apparaissant lorsque, dans un milieu poreux, un fluide moins visqueux déplace un fluide plus visqueux. L’objectif de notre thèse est l’étude expérimentale des propriétés des motifs de digitation lorsque l'échantillon de fluide visqueux est de taille finie et lorsqu'une réaction chimique modifie la viscosité dans un milieu poreux modèle, en l’occurrence une cellule de Hele-Shaw. En particulier, notre étude a permis de quantifier la contribution de dispersion et de la digitation visqueuse à l’étalement dans l’espace d’échantillons de taille finie en fonction des paramètres expérimentaux (contraste de viscosité, vitesse de déplacement et taille de l’échantillon). Pour les fluides réactifs, nous analysons la digitation induite par une réaction A + B → C dont le produit C est plus visqueux que les réactifs A et B, ceux-ci ayant la même viscosité. Nous mettons en évidence l’effet des concentrations en réactifs, du choix du fluide vecteur et du débit d’injection sur le motif de digitation.

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Many critics examine Shaw's plays in terms of the subjects they deal with, but they often ignore what aspects of these subjects Shaw draws on or how he uses them. One subject that appears in many of his works is war. This thesis examines Shaw's treatment of war in Arms and the Man and Heartbreak House, and attempts to discover a common element between them that reveals something not only about the plays themselves, but also about Shaw's drama in general. The chapter on Arms and the Man notes how Shaw makes war a highly visible element of the play, but avoids dealing with issues directly related to war. Shaw does not draw on war itself, but on its image. The sources for Catherine's and Bluntschli's impressions of both war and Sergius—Lady Butler's paintings, the military melodrama and extravaganza, Tennyson's "Charge of the Light Brigade," and accounts of the Battle of Balaklava—indicate that the play's focus is not on war, but on how one perceives the world. This idea is further reinforced by Shaw's own views about idealism, romanticism, and realism. Unlike Arms and the Man, war is an integral part of Heartbreak House. Shaw uses elements from the British homefront during the First World War—the wasted lives of England's youth, the lies of the government and the press, and the potential for violence both on the front and at home during the conflict—to help create the play's deep sense of crisis and impending doom. But as with Arms and the Man, Heartbreak House is not a play about war. Whereas war is highly visible in the former, its presence is negligible in the latter: there are no military characters or any clear indication that a war is in progress until the end of the play. Moreover, Shaw does not draw on sources related only to the war. Thus while Heartbreak House was born largely out of the despair of the First World War, its themes go beyond that conflict to deal with questions about the individual, the family, and the fabric of society itself. This thesis concludes by briefly examining Saint Joan, and notes that it combines the two approaches to war found in Arms and the Man and Heartbreak House, but distances its intended audience—the English—by using a historical conflict where Englishmen are the enemy. In comparing the three plays' treatment of war, one can conclude that the common element in Shaw's treatment of war is his distancing of an audience from the subject itself. Moreover, one discovers that this distancing is related to the nature of the subjects that Shaw uses for his plays. Only subjects that he believed were complex were suitable for creating his dramatic works. Therefore, it is fruitless for critics to examine Shaw's plays for his opinions about a subject; they should concentrate on how Shaw uses these subjects in his plays instead. / Arts, Faculty of / English, Department of / Graduate

The aim of this diploma thesis is experimental verification of the influence of ceramics composition on the manipulation strength of the cores in the Shaw method. The work deals mainly with influence of the amount of acid in the composition of the binding fluid on the handling strength of the cores and the strength of the cores after annealing. The thesis further examines the possibility of increasing the handling strength of the cores by adding phosphoric acid to the binding fluid.

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