Cette thèse en mathématiques appliquées à la nanoélectronique aborde le problème de la simulation mathématique et numérique du transport de gaz d'électrons confinés dans certaines directions de l'espace. A l'échelle de la nanoélectronique, les phénomènes ondulatoires liés au transport des électrons ne peuvent plus être négligés et la description classique du transport électronique doit laisser place à une approche quantique. La modélisation de tels phénomènes nécessite la résolution de systèmes couplés de type Schrödinger-Poisson, coûteux numériquement. Cette thèse s'appuie donc sur le confinement fortement anisotrope des électrons dans de telles structures pour obtenir des modèles asymptotiques à dimensionnalité réduite, via une analyse asymptotique "fort confinement". La principale difficulté mathématique provient ici des oscillations rapides dues au confinement. Des méthodes telles que la moyennisation en temps long sont décrites pour y remédier. On s'intéresse dans cette approche à plusieurs situations de confinement différentes. Ainsi, on présente deux modèles asymptotiques pour la modélisation du transport d'électrons confinés sur un plan, ainsi qu'un modèle de confinement sur un plan d'un gaz d'électrons soumis à un champ magnétique fort uniforme. Enfin, on propose un modèle asymptotique mathématique ainsi que des simulations numériques dans le cas du transport d'électrons confinés dans un nanofil quantique. Celles-ci sont obtenues par des méthodes numériques basées sur l'idée de la réduction de dimensionnalité qui font appel notamment à une méthode de décomposition en sous-bandes.

<p>By the late nineteenth century childbirth was firmly established in the domestic sphere. However, in the early years of the twentieth century different forms of maternity clinics were established where normal, as well as complicated, deliveries could take place. The aim of this dissertation is to analyse the institutionalisation of maternity care in a local urban context, the role of women in confinement in this process, and its impact on infant mortality. The geographical setting of the thesis is Sundsvall, a town in northern Sweden. The study concentrates on the period spanning from 1900 to 1930, when local communities, rather than federal agencies, were charged with creating and implementing community standards for maternity care.</p><p>In order to lower the mortality rate of illegitimate infants, and to improve delivery conditions for unmarried women, a maternity home was opened in Sundsvall in 1913. Moreover, a maternity ward was established at the local hospital in 1920. In this study it is clear, that when institutional maternity care became available, the transition was rapid and unhesitating. When analysing the local practices it is possible to highlight the central role women played as part of this process. Initially indigent women and women bearing children out of wedlock accepted the institutional alternative, but shortly thereafter married women of means turned to the newly created wards. As a result of this early acceptance, these institutions were soon filled to capacity. </p><p>During the period in question a significant reduction in infant mortality rates can be noticed in the Swedish towns. A reasonable assumption is that the institutionalisation of maternity care improved infants chances of survival. In the study it is suggested that the institutionalised maternity care made an impact on neonatal mortality, as well as on post-neonatal mortality. The study shows that local practices of care played a key role in infant survival.</p><p>This dissertation reveals the value of examining local practices in order to understand the rapid changes of maternity care. Childbirth changed from being a private matter, taking place in one’s home, to be a public concern, taking place in the institutional setting. At the 1937 Parliament (Riksdag) the responsibility for institutionalised maternity care became a public and a State concern, and maternity care became a part of the Swedish welfare system.</p>

<p>Thermonuclear fusion is a promising energy source for the future. If an economically efficient thermonuclear reactor would be built it has to be a cheap, safe, and highly productive electric power plant, or, a heating plant.</p><p>The emphasis of this thesis is on the single cell mirror trap with a marginally stable minimum B vacuum magnetic field, the straight field line mirror field, which provides MHD stability of the system, absence of the radial drift even to the first order in plasma β , and a reduced magnetic flux tube ellipticity. Strong density depletion at the mirrors is proposed as a mean to build up a strong potential barrier for the electrons and thereby increase the electron temperature. Conditions to obtain an energy gain factor Q>10 are briefly analyzed. Current coils which could generate the derived magnetic field are proposed. A sloshing ion distribution function is constructed for the three dimensional ‘straight line mirror field’. The gyro centre Clebsch coordinates are found to be a new pair of motional invariants for this magnetic field. The gyro centre Clebsch coordinate invariants can be used to obtain complete solutions of the Vlasov equation, including the diamagnetic drift. These solutions show that the equilibria satisfy the locally omniginuity criterion to the first order in β .</p><p>Contributions of the plasma diamagnetism to the magnetic flux tube ellipticity are studied for the straight field line mirror vacuum magnetic field and a sloshing ion distribution. Computations employing ray tracing have shown that there is a modest increase in the ellipticity, but the effect is small if β <0.2 .</p><p>Adiabatic charged particle motion in general field geometry has been studied. A set of four independent stationary invariants, the energy, the magnetic moment, the radial drift invariant, and the bounce average parallel velocity is proposed to describe adiabatic equilibria. </p>

This thesis studies the behavior of the Eulerian scheme, with "Wave Confinement" (WC), when propagating periodic waves. WC is a recently developed method that was derived from the scheme "vorticity confinement" used in fluid mechanics, and it efficiently solves the linear wave equation. This new method is applicable for numerous simulations such as radio wave propagation, target detection, cell phone and satellite communications. The WC scheme adds a nonlinear term to the discrete wave equation that adds stability with negative and positive diffusion, conserves integral quantities such as total amplitude and wave speed, and it allows wave propagation over long distances with minimal numerical diffusion, which contrasts to other numerical methods where wave propagation is affected by numerical dissipation. Previous studies have shown that WC propagates short pulses/surfaces as thin nonlinear solitary waves. In this thesis, a one-dimensional (1D) periodic wave is propagated by WC using the advection and wave equations. For the advection equation, the parameters and the initial condition (IC) used in WC are analyzed to establish for which conditions the method can be implemented. When the IC is a positive periodic wave, the converged solution consists of a series of hyperbolic secants where the number of cycles of the IC represents the number of hyperbolic secants. Waves with varying signs are analyzed by changing the wave confinement term. For this case, the converged solution is a series of positive and negative hyperbolic secants where each hyperbolic secant is represented by half cycle of the IC. For the wave equation, parameters and different IC's are studied to determine when WC is feasible. For positive periodic waves, the converged solution retains its sinusoidal shape and does not converge to a series of hyperbolic secants. The waves with varying signs, however, converge to a series of hyperbolic secants as seen for the advection equation. WC is stable for various periodic waves for both advection and wave equations, which shows WC is useful for numerically propagating periodic waveforms. Convergence depends on the wave number of the IC and on the parameters (convection speed, positive diffusion, negative diffusion) used in WC.

Cette thèse développe une stratégie multi-échelle pour représenter le comportement mécanique des armatures et des câbles de précontrainte dans une structure en béton armé. Cette stratégie est déclinée en plusieurs étapes, permettant d'intégrer progressivement de nouveaux phénomènes physiques dans la modélisation. Le premier modèle asymptotique développé permet de représenter le comportement élastique effectif d'hétérogénéités périodiquement réparties sur une surface. Il combine un comportement d'interface élastique et un comportement de membrane. Un second modèle asymptotique s'intéresse ensuite au comportement de fibres rigides réparties sur une surface, et susceptibles de glisser par rapport au volume environnant. Ces modèles présentent l'avantage d'induire moins de concentrations de contraintes que les modèles de barres utilisés classiquement. Ils sont implantés dans le code éléments finis Code_Aster, et validés par rapport à des simulations tridimensionnelles de référence. Leur interaction avec une fissure présente dans le béton est étudiée. Enfin, cette stratégie permet de modéliser des essais expérimentaux réalisés sur une portion d'enceinte de confinement à l'échelle 1.

By the late nineteenth century childbirth was firmly established in the domestic sphere. However, in the early years of the twentieth century different forms of maternity clinics were established where normal, as well as complicated, deliveries could take place. The aim of this dissertation is to analyse the institutionalisation of maternity care in a local urban context, the role of women in confinement in this process, and its impact on infant mortality. The geographical setting of the thesis is Sundsvall, a town in northern Sweden. The study concentrates on the period spanning from 1900 to 1930, when local communities, rather than federal agencies, were charged with creating and implementing community standards for maternity care. In order to lower the mortality rate of illegitimate infants, and to improve delivery conditions for unmarried women, a maternity home was opened in Sundsvall in 1913. Moreover, a maternity ward was established at the local hospital in 1920. In this study it is clear, that when institutional maternity care became available, the transition was rapid and unhesitating. When analysing the local practices it is possible to highlight the central role women played as part of this process. Initially indigent women and women bearing children out of wedlock accepted the institutional alternative, but shortly thereafter married women of means turned to the newly created wards. As a result of this early acceptance, these institutions were soon filled to capacity. During the period in question a significant reduction in infant mortality rates can be noticed in the Swedish towns. A reasonable assumption is that the institutionalisation of maternity care improved infants chances of survival. In the study it is suggested that the institutionalised maternity care made an impact on neonatal mortality, as well as on post-neonatal mortality. The study shows that local practices of care played a key role in infant survival. This dissertation reveals the value of examining local practices in order to understand the rapid changes of maternity care. Childbirth changed from being a private matter, taking place in one’s home, to be a public concern, taking place in the institutional setting. At the 1937 Parliament (Riksdag) the responsibility for institutionalised maternity care became a public and a State concern, and maternity care became a part of the Swedish welfare system.

Le domaine des résonateurs MEMS (Micro-Electro-Mechanical Systems) est aujourd'hui le siège de diverses compétitions entre les producteurs afin d'améliorer les performances en terme de miniaturisation, intégrabilité, coûts de production etc. Ce travail de thèse s'inscrit dans un projet global de développement de résonateurs MEMS à ondes de volume compatibles avec la technologie des circuits intégrées. L'objectif est de valider le principe d'excitation des ondes acoustiques de volume en extension-compression par voie électrostatique dans des substrats monocristallins et aussi d'explorer les possibilités offertes par ces modes pour le confinement de l'énergie acoustique, technique plus largement exploitée dans le domaine des résonateurs à quartz que dans celui des MEMS. En ce sens, une nouvelle structure mono-port en silicium, fixée sur un support en verre, a été étudiée et modélisée analytiquement en vue de son implémentation dans une chaine de fabrication. Les modèles originaux développés dans ce cadre nous ont permis d'estimer les paramètres électriques du circuit équivalent, les déplacements mécaniques statique et dynamique propres au fonctionnement de la structure, autant en mode vibratoire d'extension-compression qu'en mode de flexion. Une étude théorique bidimensionnelle basée sur l'évaluation des courbes de dispersion d'une plaque en silicium a été menée afin d'évaluer les moyens de piégeage de l'énergie au centre de la structure fonctionnant en mode de volume. Tout en exploitant les microtechniques disponibles au sein de la Centrale MIMENTO de l'Institut FEMTO-ST, plusieurs séries de résonateurs ont été fabriquées sur substrat silicium pleine plaque. La fréquence fondamentale de vibration se situe aux alentours de 10 MHz pour le mode d'extension compression et de 70 kHz pour le mode de flexion. On détaille la caractérisation par voie mécanique et électrique. L'intégration des dispositifs fonctionnant en mode de flexion en boucle d'oscillation à l'aide d'un montage à base de point Wien est démontrée ainsi qu'une application de type capteur gravimétrique.

The profile of the poloidal velocity in the edge region of tokamak plasmas has been identified as playing a major role in the confinement of particles and energy. It has been suggested that a strongly sheared poloidal flow can reduce particle and energy losses by the stabilization of unstable modes and decorrelation of turbulence the edge region of the plasma. A Gundestrup probe, a Mach probe array, is used to measure both the parallel and perpendicular flow velocities in the Saskatchewan Torus-Modified (STOR-M) tokamak during several discharge conditions. It is observed that during Ohmic discharges there is no velocity shear and the direction of the parallel flow is independent of the direction of the toroidal magnetic field. During H-mode induced by a turbulent heating current pulse, a region of strong velocity shear develops in the plasma edge and an edge transport barrier develops. This results in a short period of improved particle and energy confinement with reduced fluctuation amplitudes. During electrode biasing experiments, a stainless steel biasing electrode is inserted into the plasma up to r = 82 mm and biased to +500 V relative to the vacuum chamber. It is observed that the particle confinement improves during the biasing phase while the energy confinement is degraded. A region of weak shear in the poloidal flow is observed in the plasma scrapeoff layer (SOL). The results from STOR-M are compared with results from data taken in the Czech Academy of Sciences Torus (CASTOR) tokamak during both Ohmic discharges and discharges with electrode biasing.

The profile of the poloidal velocity in the edge region of tokamak plasmas has been identified as playing a major role in the confinement of particles and energy. It has been suggested that a strongly sheared poloidal flow can reduce particle and energy losses by the stabilization of unstable modes and decorrelation of turbulence the edge region of the plasma. A Gundestrup probe, a Mach probe array, is used to measure both the parallel and perpendicular flow velocities in the Saskatchewan Torus-Modified (STOR-M) tokamak during several discharge conditions. It is observed that during Ohmic discharges there is no velocity shear and the direction of the parallel flow is independent of the direction of the toroidal magnetic field. During H-mode induced by a turbulent heating current pulse, a region of strong velocity shear develops in the plasma edge and an edge transport barrier develops. This results in a short period of improved particle and energy confinement with reduced fluctuation amplitudes. During electrode biasing experiments, a stainless steel biasing electrode is inserted into the plasma up to r = 82 mm and biased to +500 V relative to the vacuum chamber. It is observed that the particle confinement improves during the biasing phase while the energy confinement is degraded. A region of weak shear in the poloidal flow is observed in the plasma scrapeoff layer (SOL). The results from STOR-M are compared with results from data taken in the Czech Academy of Sciences Torus (CASTOR) tokamak during both Ohmic discharges and discharges with electrode biasing.

Z-Pinch IFE (Inertial Fusion Energy) reactor designs will likely utilize high yield targets (~ 3 GJ) at low repetition rates (~ 0.1 Hz). Appropriately arranged thick liquid jets can protect the cavity walls from the target x-rays, ions, and neutrons. However, the shock waves and mechanical loadings produced by rapid heating and evaporation of incompressible liquid jets may be challenging to accommodate within a small reactor cavity. This investigation examines the possibility of using two-phase compressible (liquid/gas) jets to protect the cavity walls in high yield IFE systems, thereby mitigating the mechanical consequences of rapid energy deposition within the jets. Two-phase, free, vertical jets with different cross sections (planar, circular, and annular) were examined over wide ranges of liquid velocities and void fractions. The void fraction and bubble size distributions within the jets were measured; correlations to predict variations of the slip ratio and the Sauter mean diameter were developed. An exploding wire system was used to generate a shock wave at the center of the annular jets. Attenuation of the shock by the surrounding single- or two-phase medium was measured. The results show that stable coherent jets can be established and steadily maintained over a wide range of inlet void fractions and liquid velocities, and that significant attenuation in shock strength can be attained with relatively modest void fractions (~ 1%); the compressible two-phase jets effectively convert and dissipate mechanical energy into thermal energy within the gas bubbles. The experimental characteristics of single- and two-phase jets were compared against predictions of a state-of-art CFD code (FLUENT®). The data obtained in this investigation will allow reactor system designers to predict the behavior of single- and two-phase jets and quantify their effectiveness in mitigating the consequences of shock waves on the cavity walls in high yield IFE systems.