The conventional methods for diagnosing pathological conditions of the tympanic membrane (TM) and other abnormalities require measuring its motion to an acoustic excitation for its use in a clinical environment. To obtain comprehensive quantitative diagnostic information from the motion of the entire surface of the TM, it is necessary to devise an integrated system capable of accurately recording the motion and induce an acoustic stimulus. To accomplish this goal, a sound presentation system (SPS) capable of impinging acoustic stimulus in the frequency range of 20Hz to 8 kHz at known amplitudes is synthesized in this thesis. This system is then integrated with optoelectronic digital holographic system (OEDHO) which utilizes laser interferometry to record and reconstruct phase shifted images with the help of a digital camera. The OEDHO is capable of accurately recording nanometer scale motion of the TM. The preliminary design of the SPS depends on the physical dimensions of the human ear, such as the diameter of the TM (6-9mm), depth of the ear canal (about 30mm), and also dimensions of the OEDHO system such as: diameter of tip of the otoscope head for optical access (8mm), and possible locations for integration with the OEDHO. The characteristics of the system are based on the intensity of the acoustic stimulus necessary to vibrate the TM (90-110dB SPL), and method of impinging the stimulus. To accomplish this goal, the nature of sound wave propagation through a circular pipe with known dimensions is analyzed analytically, experimentally, and by using finite element analysis (FEA). The pipe is further investigated for optimum parameters using FEA by introducing changes in the diameter (3.8mm, 6mm, 10mm), length of the pipe (30mm, 60mm, 90mm), radius of the curvature (50mm, 75mm, 100mm), and strength of the sound power source (0.2W, 0.4W, 0.6W). The comparative results provide guidelines for the design of the first version of the SPS (SPS_V1). The SPS_V1 consists of a symmetric design to impinge the acoustic stimulus towards the TM and a microphone to measure the sound pressure at the TM. The system is capable of housing a range of speakers from 2mm to 15mm in diameter. The SPS_V1 can directly interface with the standard medical speculums used for human ear testing. Also, the system is capable of interfacing with all available versions of the OEDHO. The SPS_V1 is currently being evaluated in a medical-research environment to address basic otological questions regarding TM function. The performance characterization of the system inside an artificial ear canal with two different speaker configurations is herein shown, and the potential improvements and utilization are discussed

L'électrolyse haute température de l'eau à l'aide de membranes en céramique conductrice de protons est un processus intéressant pour la production d'hydrogène. Ce processus, qui peut être effectué sans catalyseurs nobles, produit de l'hydrogène pur et nécessite moins d'électricité que l'électrolyse classique à basse température. Le développement futur de ces réacteurs à membrane nécessite des efforts accrus sur la simulation numérique afin d'optimiser la chaleur et les transferts de masse ainsi que la conception de cellules d'électrolyse. Ce travail présente un ensemble d'équations sélectionnées dans la littérature et des démonstrations mathématiques rigoureuses permettant la description des phénomènes de transport dans la cellule et en particulier dans les électrodes qui sont composées de cermets. A partir de ce modèle, une étude paramétrique est conduite de façon à caractériser l'influence des différents paramètres opératoires sur ces phénomènes. Les différentes observations de cette étude permettent de dresser un ensemble d'hypothèses pour le développement de méthodes destinées à la simplification du modèle et à la réduction du temps de résolution. Ces modèles simplifiés permettent la détermination analytique des grandeurs dans l'électrode et ont conduit à la construction de nombres adimensionnels et de longueur caractéristiques du dispositif. / High temperature electrolysis of water by using proton conducting ceramic membranes is an interesting process for producing hydrogen. This process can be carried out without noble catalysts and produces pure hydrogen and requires less electricity than classical low temperature electrolysis. The future development of such membrane reactors requires increasing efforts on numerical simulation in order to optimize the heat and mass transfers as well as the design of electrolysis cells. This work presents a set of equations selected from the literature and rigorously demonstrated for the description of transport phenomena in the cell and particularly in the electrodes which are made of cermets. From this model, a parametric study is conducted in order to characterize the influence of various operating parameters on these phenomena. The different findings of this study provide a set of assumptions for the development of methods for simplifying the model and reducing the time of resolution. These simplified models allow analytical determination of quantities in the electrode and leads to the establishment of dimensionless numbers and characteristics length of the device.

Ce travail présente le développement de spectromètres photoacoustiques pour la mesure de traces de gaz avec des résonateurs de Helmholtz différentiels.La cuve représente le coeur de l'instrument, le laser qui la traverse va créer une onde de pression stationnaire qui sera mesurée par des microphones. Le signal photoacoustique est fonction de la concentration du gaz et la manière dont il sera amplifié va dépendre en grande partie de la géométrie de la cuve. Une méthode aux éléments finis est utilisée pour exprimer cette caractéristique selon les modes et les fréquences propres calculées de la cuve. Les paramètres clés de la cuve sont ainsi calculés, comme la fréquence de résonance, le facteur de qualité et la constante de la cuve. Contrairement à d'autres méthodes de spectroscopie infrarouge, la sensibilité des spectromètres photoacoustiques augmente alors que la cuve se miniaturise. Cette particularité est vérifiée expérimentalement avec un bon accord avec la simulation. La modélisation prouve une nouvelle fois être suffisamment robuste pour être utilisée dans un processus d'ingénierie du spectromètre. Cet outil va en effet permettre d'optimiser les dimensions du résonateur selon les besoins de l'application, soit en privilégiant le maximum de signal, la plus haute fréquence de travail ou encore le plus faible encombrement. De nombreuses cuves ont été développés avec l'aide de la simulation, l'écart observé avec les paramètres expérimentaux est de l'ordre de 15 %. Enfin, les applications actuelles en mesure de traces de gaz demandent de mesurer la concentration d'au moins deux gaz, de façon simultanée, avec des niveaux de détection proche du ppb. Un mode de résonance de Helmholtz particulier est trouvé afin de proposer une mesure multi-gaz. Enfin, la sensibilité est augmentée grâce à un système multi-passages. / This work presents the conception of a photoacoustic spectrometer dedicated to trace gas measurements using a differential Helmholtz resonator. The main component of the instrument is the cell, where a standing wave is produced by a laser excitation and is measured with microphones. The photoacoustic signal is proportional to the gas concentration and the cell shape mainly affects its amplification. A finite element method is used to find this characteristic by calculating the cell eigenmodes and eigenfrequencies.Key parameters of the cell are then calculated, including cell frequency, quality factor and cell constant. Unlike other infrared spectroscopy methods, sensitivity of photoacoustic spectrometers increases by miniaturization process. This particular phenomenon is experimentally verified and is in good agreement with the simulation.Modelization proves again its robustness to be used on an engineering process of the spectrometer. This tool allows to optimize resonator dimensions according to the application, favouring maximum signal, higher working frequency or reduced size. Many cells designed with the help of the simulation are presented, where the observed error with experiments is of the order of 15 %. Finally, today's trace gas applications need the measurement of at least two concentrations, simultaneously with detection limits down to the ppb level. A novel Helmholtz resonance mode is then found to allow multi-gas sensing.Finally, sensitivity is increased by multi-pass systems.

The falling film flow of milk was studied both analytically and experimentally. Experiments were carried out for concentrations from 19.93% to 62.09% to obtain the rheological data of milk while analytical studies were done to derive the solutions of the problem. Studies which include calculations and simulations were carried out for a typical milk flow in a falling film evaporator. It was found that milk was non-Newtonian at high concentrations and Herschel-Bulkley model was able to model the milk flow. The typical falling film flow was able to be simulated as a two phase flow in COMSOL to gain a better understanding of the flow. It was found that there were counter-current flow between the film and air in the evaporator. A Matlab program was also used to study the analytical solutions of the film temperature change while it flows down the tube with results showing that heat transfer was not linear as would have believed. Results from several experiments also enabled the change of milk viscosity with time to be modeled. Milk viscosity increased steadily with time and higher at higher total solids from 35.47% to 49.25% for three hours. Calculations revealed that film thickness of milk was very thin, from 0.00116 m at the entrance of tube to 0.00146 m at the tube exit. From the use of models developed of the rheological parameters, results showed that these parameters have impacts on film flow except the yield stress. However, the viscosity and yield stress are factors that will limit the operating range available for falling film evaporator.

Optical trapping is an important tool for studying and manipulating nanoscale objects. Recent experiments have shown that subwavelength control of nanoparticles is possible by using patterned plasmonic nanostructures, rather than using a laser directly, to generate the electric fields necessary for particle trapping. In this thesis we present a theoretical model and experimental evidence for plasmonic optical trapping in nanoscale metal junctions. Further, we examine the use of the resultant devices as ultrasmall photodectors. Electromigrated nanojunctions, or “nanogaps”, have a well-established plasmon resonance in the near-IR, leading to electric field enhancements large enough for single-molecule sensitivity in Surface-Enhance Raman (SERS) measurements. While molecule-based devices have been carefully studied, optically and electrically probing individual quantum dots in nanoscale metal junctions remains relatively unexplored. Plasmon-based optical trapping of quantum dots into prefabricated structures could allow for inexpensive, scalable luminescent devices which are fully integrable into established silicon-based fabrication techniques. Additionally, these metal-nanocrystal-metal structures are ideal candidates to study optoelectronics in ultrasmall nanocrystals-based structures, as well as more exotic nanoscale phenomena such as blinking, plasmon-exciton interactions, and surface-enhanced fluorescence (SEF). We present experimental data supporting plasmon-based optical trapping in the nanogap geometry, and a corresponding numerical model of the electric field-generated forces in the nanogap geometry. Further, we give proof-of-concept measurements of photoconductance in the resultant quantum dot-based devices, as well as challenges and improvements moving forward.

Vågenergi är en nära helt oanvänd förnybar energiresurs med enorm potential och många fördelar jämfört med andra förnybara energikällor. Men havsmiljön är hård och krafterna kan bli mycket stora vilket ställer höga krav på vågkraftverkets konstruktion. Detta har förhindrat ett kommersiellt genombrott för vågkraften. Waves4Power har utvecklat ett vågkraftverk, WaveEL, som består av en flytboj och en vertikal cylinder med vattenkolv. Vattenpelaren i cylindern oscillerar i takt med vågorna och driver vattenkolven. Ett hydraulsystem bromsar vattenkolvens rörelser och utvinner energi ur vågorna. Mellanrummet mellan vattenkolv och cylindervägg kallas läckspalt och varierar i storlek över kolvens slaglängd. Hur kraftverkan på kolven ser ut vid olika flöden i cylinder och läckspalt är mindre känt. Om läckspalten är för stor förlorar kraftverket i effektivitet medan kraftverkan på kolven minskar. Är läckspalten istället för liten medför detta att geometrisk orundhet kan leda till skador. Det är också möjligt att kavitation uppstår runt kolven vilket innebär påfrestningar för konstruktionen. Simulering av kraftverkan genomfördes i COMSOL Multiphysics för att kartlägga kraftverkan och finna ett samband mellan kraftverkan på vattenkolven och andra variabler samt undersöka kavitationsrisken. Ett linjärt, dimensionslöst samband mellan kraftverkan på vattenkolven och en funktion beroende av flödeshastighet, kolvradie, periodtid och läckspaltens storlek togs fram. De områden som under vissa givna förutsättningar kan utsättas för kaviterande ångblåsor har sammanställts och resultatet visar hög risk för kavitation då kolven befinner sig i övre bypass-sektionen. / Wave energy is a nearly unused renewable energy resource with great potential and many advantages compared to other renewable energy sources. But the marine environment is harsh and the forces in the waves can be very large, which is very demanding to the wave energy converters construction. To this date, these factors has prevented a commercial breakthrough for wave power. Waves4Power has developed a wave energy converter, WaveEL, consisting of a buoy and a vertical cylinder with a water piston. The water column in the cylinder oscillates with the waves and drives the water piston. A hydraulic system brakes the water pistons movements and extract energy from the waves. The spacing between the water piston and cylinder wall is called leakage channel and varies in size over the piston stroke. How the forces on the water piston vary with the flow rate in the cylinder and the leakage gap is less known. If the leakage gap is too big the wave energy converter loses efficiency while the forces on the piston decreases. If the leakage gap is to small, this means that the lack of geometric roundness can lead to damage. It is also possible that cavitation occurs around the piston which could damage the construction. Simulation of the forces acting on the water piston was done in COMSOL Multiphysics. The objective was to map the forces acting on the water piston and ultimately to find a connection between the forces on the water piston and other variables. Lastly, the risk of cavitation was examined. A linear, dimensionless correlation between the forces on the water piston and a function dependent on flow rate, the piston radius, the wave period and the size of the leakage gap was developed. The areas that under certain given conditions can be exposed to cavitation have been compiled and the results show a high risk of cavitation when the piston is in the upper bypass section of the stroke.

Le travail réalisé au cours de cette thèse concerne le développement du système de bobines de l'expérience n2EDM à l'Institut Paul Sherrer (PSI). Le but de cette expérience est de mettre en évidence de nouvelles sources de violation CP à travers la mesure du moment dipolaire électrique du neutron. L'actuelle limite supérieure sur la mesure de nEDM, $2.9 \cross 10^{-26}$ e.cm (90\% C.L.) à été obtenue par la collaboration RAL-Sussex-ILL en 2006.L'expérience n2EDM vise à améliorer d'un ordre de grandeur la sensibilité statistique en gardant sous contrôle les effets systématiques. Cela requiert la production d'un champ magnétique très uniforme. Les non-uniformités de ce dernier sont en effet responsable de la dépolarisation des neutrons et impliqués dans plusieurs effets systématiques.Dans le premier chapitre, les motivations physiques sont discutées.Le second chapitre décrit le principe de mesure de l'expérience n2EDM, ainsi que l'importance de l'uniformité du champ magnétique. Le chapitre s'achève par une présentation globale du dispositif expérimental.Le troisième chapitre présente le logiciel COMSOL et discute du design et des performances de la bobine B$_{0}$, en charge de la production du champ magnétique principal.Dans le quatrième chapitre, le système de bobines correctrices chargées de corriger les non-uniformités du champ magnétique et celles devant produire des gradients spécifiques sont présentées.Finalement, le cinquième et dernier chapitre présente l'étude des dipôles magnétiques localisés et de leur influence sur l'expérience. / This work presents the design of the coils system developed for the n2EDM experiment at the Paul Sherrer Institute (PSI). The goal of this experiment is to reveal new sources of CP violation through the measurement of the neutron electric dipole moment. The current upper limit of the nEDM measurement, $2.9 \cross 10^{-26}$ e.cm (90\% C.L.) was achieved by the RAL-Sussex-ILL collaboration in 2006.The n2EDM experiment aims at improving by one order of magnitude the statistical sensitivity while keeping under control the systematics effects. It requires to produce a very uniform field, its non-uniformities being responsible of the neutron's depolarization and of severals systematic effects.In the first chapter, the theoretical motivation are discussed.The second chapter describes the measurement principle of the n2EDM experiment, as well as the importance of the magnetic field uniformity. This chapter ends by an overview of the apparatus.The third chapter introduces the COMSOL software and discuss the design and the performances of the B0 coil, in charge of the production of the main magnetic field.In the fourth chapter, the correcting coils used to suppress the non-uniformities of the magnetic field and the ones which produce specific gradients are presented.Finally, the fifth and last chapter talks about the study of localised magnetic dipoles and their influence on the experiment.

I detta arbete simulerades pressningsprocessen och värmeflödet hos en kabelsko genom att använda finite element analasis med hjälp av simuleringsprogrammet COMSOL Multiphysics. Syftet med värmeanalysen var för att undersöka om kabelskon får värmefläckar under drift som kan orsaka utmattning av metall. Först simulerades pressningsprocessen. Resultatet från pressnings-simuleringen användes sedan som underlag för att kunna genomföra värmeflödesanalysen av en pressad kabelsko i drift. Vid värmeanalysen hade kabeln en fast temperatur och kabelskons temperatur var beroende av tiden. Resultatet från simuleringen visade att det uppstår värmefläckar under drift men med väldigt låga temperaturskillnader. Däremot finns det osäkerheter i den valda metoden då många förenklingar gjordes i simuleringen. En simulering av värmeöverföring, där kabeln hade en fast temperatur, gjordes i ställetför att simulera en ström som går igenom kabeln och kabelskon. Val av detalj av meshen var enbart tillräckligt hög för att programmet skulle kunna genomföra beräkningen. En mer detaljerad mesh ger ett godare resultat. Modellen av kabelskon förenklades även till ett rör för att bespara beräkningstiden av programmet. För att möjligen öka noggrannheten på resultatet behövs en simulering med mer detaljerad mesh, med ström genom kabeln i stället för en fast temperatur och med en modell av den faktiska kabelskon i stället för en förenkling. En mer detaljerad mesh innebär mer detaljerad deformation i pressningsprocessen. Detta kan innebära fler och bättre kontaktytor mellan kabel och kabelsko och därmed en noggrannare resultat av värmeanalysen. Att simulera med ström och en icke-förenklad modell av en kabelsko i stället för fast temperatur och en förenklad modell innebär en mer verklighetsbaserad simulering där eventuella effekter av ojämn strömtäthet kan fångas. Vidare rekommenderas att en validering av simuleringen genomförs med hjälp av ett verklig test med exempelvis en värmekamera. / The crimping process and the heat flow on a cable lug were simulated in this project using finite element analysis and the simulation software COMSOL Multiphysics. The purpose of the heat analysis is to determine if there are any hot spots, that are prone to cause metal fatigue, on a cable lug while in use.Firstly, the crimping process were simulated. The result from the crimping process were then used to simulate the heat transfer while the cable lug is in use. The cable in the heat analysis had a fixed temperature and the temperature of the cable lug was time dependent. The simulation showed hot spots on the cable lug while in use although the temperature difference was modest. There were on the other hand uncertainties with the choice of method because simplifications were made in the simulation. A heat transfer where the cable hade a set value of temperature wassimulated instead of simulating a current that goes through the cable and the cable lug. The choice of mesh detail was just high enough for the software to be able to do calculations. A higher mesh quality would yield a better result. The geometry of the cable lug was simplified as a tube to save computation time. A new simulation with higher mesh quality, with current flowing through the cable and the cable lug instead of a set temperature and with the actual model of the cable lug is needed to get a more accurate result. A more detailed mesh means better approximations in crimping simulation which in turn gives better results in heat analysis due to better contact surface between the cable and the cable lug. Having current flow through the cable and the actual model of the cable lug instead of the simplifications that were made in the simulation is closer to reality and which can give a more accurate result. A validation of the simulation is recommended by using for example a thermal camera.

Corona discharge is one of the crucial problems related with high-voltage equipment. This paper focuses on the physical and numerical modelling of corona discharge in an Electrostatic precipitator (ESP). The model is based on Maxwells equations and the Finite element method (FEM) and is implemented with the COMSOL Multiphysics software.The simulation allows studying the electric charge distribution and the behaviour of the electric field inside the ESP. The work is focused primarily on time-dependent studies of the corona discharge.

Iliac artery aneurysms are considered rare and difficult to detect and treat. Prompt diagnosis and timely intervention are essential, because the incidence of rupture is as high as 50%. The reported mortality rate for patients who undergo surgery for ruptured iliac artery aneurysm ranges from 50% to 70%. This study developed an in-vitro mechanical model of an iliac artery aneurysm to verify the accuracy of computer simulation software. Both the in vitro model and the in silico model can be used for further research to develop better treatment technology. This study also looks at the different types of iliac artery aneurysms, risk factors that contribute to the development of an iliac artery aneurysms, and current treatment options.