Traction inverter, as a critical component in electrified transportation, has been the subject of many research studies in terms of topologies, modulation, and control schemes. Recently, some of the well-known electric vehicle manufacturers have utilized higher-voltage batteries to benefit from lower current, higher power density, and faster charging times. With the ongoing trend toward higher voltage DC-link in electric vehicles, some multilevel structures have been investigated as a feasible and efficient option for replacing the two-level inverters. Higher efficiency, higher power density, better waveform quality, and inherent fault-tolerance are the foremost advantages of multilevel inverters which make them an attractive solution for this application. The first contribution of this thesis is to investigate and present a comprehensive review of the multilevel structures in traction applications. Secondly, this thesis proposes an electro-thermal model based on foster equivalent thermal networks for a designed three-level active neutral point clamped (ANPC) inverter, as well as a modified sinusoidal pulse-width modulation (SPWM) -based technique. This electro-thermal model and the modulation technique enable temperature estimation in the inverter and minimization of the hotspot temperature and hence, increase the power density. Based on the experimental results derived from the implemented setup, a 12% increase in power density is achieved with the proposed technique. The other contribution is a reduced-complexity model-predictive controller (MPC) for the three-level ANPC inverter without weighting factors in which the number of calculations has dropped from 27 to 12 in each sampling period. The improvements to the structure and control system of the inverter are supported by theoretical analysis, simulation results, and experimental tests. A three-level inverter is implemented for 800 V, 70 kW operation and tested. 750 V Silicon Carbide (SiC) switches are utilized in the inverter structure. Finally, future trends and suggestions for the following studies are stated in this thesis. / Thesis / Doctor of Philosophy (PhD)

Interfacial mechanical properties of adhesive joints are very crucial in board applications, including composites, multilayer structures, and biomedical devices. Establishing traction-separation (T-S) relations for interfacial adhesion can evaluate mechanical and structural reliability, robustness, and failure criteria. Due to the short range of interfacial adhesion such as micro to nanoscale, accurate measurements of T-S relations remain challenging. The advent of machine learning (ML) became a promising tool to predict materials behaviors and establish data-driven mechanical models. In this study, we integrated a state-of-the-art ML method, finite element analysis (FEA), and standard experiments to develop data-driven models for characterizing the interfacial mechanical properties precisely. Macroscale force-displacement curves are derived from FEA with incorporation of double cantilever beam tests to generate the dataset for ML model. The eXtreme Gradient Boosting (XGBoost) multi-output regressions and classifier models are used to determine T-S relations with R2 score of 98.8% and locate imperfections at the interface with accuracy of around 80.8%. The outcome of the XGBoost models demonstrated accurate predictions and fast calculation speed, outperforming several other ML methods. Using 3D printed double cantilever beam specimens, the performance of the ML models is validated experimentally for different materials. Furthermore, a XGBoost model-based package is designed to obtain different adhesive materials T-S relations without creating a database or training a model.

No description available.

No description available.

No / The inner retinal complex is a well-defined layer in spectral-domain OCT scans of the retina. The central edge of this layer at the fovea provides anatomical landmarks that can be observed in serial OCT scans of developing full-thickness macular holes (FTMH). Measurement of the movement of these points may clarify the mechanism of FTMH formation. This is a retrospective study of primary FTMH that had a sequence of two OCT scans showing progression of the hole. Measurements were made of the dimensions of the hole, including measurements using the central edge of the inner retinal complex (CEIRC) as markers. The inner retinal separation (distance between the CEIRC across the centre of the fovea) and the Height-IRS (average height of CEIRC above the retinal pigment epithelium) were measured. Eighteen cases were identified in 17 patients. The average increase in the base diameter (368 microns) and the average increase in minimum linear dimension (187 microns) were much larger than the average increase in the inner retinal separation (73 microns). The average increase in Height-IRS was 103 microns. The tangential separation of the outer retina to produce the macular hole is much larger than the tangential separation of the inner retinal layers. A model based on the histology of the Muller cells at the fovea is proposed to explain the findings of this study.

Energy demands are steadily increasing as the world's population continues to grow. Automobiles are primary transportation means in a large portion of the world. The combination of fuel consumption by automobiles along with the shrinking fossil fuel reserves makes the development of new more energy efficient technologies crucial. Electric vehicle technologies have been studied and are still being studied today as a means of improving fuel efficiency. To that end, this work studies the effect of switching frequency on the efficiency of a hybrid electric vehicle traction drive, which contains both an internal combustion engine as well as electric motor. Therefore improving the efficiency of the electric motor and its drive will help improve the viability of alternative vehicle technologies. Automobiles spend the majority of their operational time in the lower speed, lower torque region. This work focuses on efficiency improvements in that region. To estimate the efficiency trend, the system is modeled and then tested both electrically and thermally. The efficiency is shown to increase at lower switching frequencies. The experimental results show that there are some exceptions, but the basic trend is the same. / Master of Science

This thesis presents the use of sliding mode control applied to a 1/10th scale robotic car to operate at a desired slip. Controlling the robot car at any desired slip has a direct relation to the amount of force that is applied to the driving wheels based on road surface conditions. For this model, the desired traction/slip is maintained for a specific surface which happens to be a Lego treadmill platform. How the platform evolved and the robot car was designed are also covered. To parameterize the system dynamics, simulated annealing is used to find the minimal error between mathematical simulations and physical test results. Also discussed is how the robot car and microprocessor can be modeled as a hybrid system. The results from testing the robot car at various desired percent slip show that it is possible to control the slip dynamics of a 1/10th scale automated robotic car and thus pave the way for further studies using scaled model cars to test an automated highway system. / Master of Science

No / BACKGROUND: A Full Thickness Macular Hole (FTMH) is often associated with vitreomacular traction, and this can be asymmetric with vitreomacular traction on one side of the hole but not the other. In cross-section, the elevated retinal rim around a developed FTMH is seen as a drawbridge elevation, and this drawbridge elevation may be used as a measure of morphological change. Examination of the drawbridge elevation of the retinal rim in FTMH with asymmetric vitreomacular traction may help to clarify the role of vitreomacular traction in the development of FTMH. METHOD: Cases of FTMH were identified with an initial OCT scan showing vitreomacular traction on one side of the hole only and that had a follow-up OCT scan showing progression of the hole. A tangent to the retinal surface at a distance of 700 microns from the axis of the hole was used as a marker of the drawbridge elevation of the retinal rim around the macular hole. Comparisons of the drawbridge elevation and change in drawbridge elevation between the sides with and without initial vitreomacular traction were made. RESULTS: There was no significant difference between the drawbridge elevation, or change in drawbridge elevation, on the side of the hole with initial vitreomacular traction compared to the side without initial traction. CONCLUSION: There is some intrinsic mechanism within the retina to link the morphological changes on the two sides of a FTMH. A bistable hypothesis of FTMH formation and closure is postulated to explain this linkage.

No / The ability of a cell to adhere and transmit traction forces to a surface reveals the cytoskeleton integrity of a cell. Shear sensitive liquid crystals were discovered with new function in sensing cell traction force recently. This liquid crystal has been previously shown to be non-toxic, linear viscoelastic and sensitive to localized exerted forces. This paper reports the possibility of extending the application of the proposed liquid crystal based cell force sensor in sensing traction forces of osteoblast-like (MG-63) and human keratinocyte (HaCaT) cell lines exerted to the liquid crystal sensor. Incorporated with cell force measurement software, force distributions of both cell types were represented in force maps. For these lowly contractile cells, chondrocytes expressed regular forces (10 – 90 nN, N = 200) around the circular cell body whereas HaCaT projected forces (0 – 200 nN, N = 200) around the perimeter of poly-hedral shaped body. These forces are associated with the organisation of the focal adhesion expressions and stiffness of the LC substrate. From the results, liquid crystal based cell force sensor system is shown to be feasible in detecting forces of both MG63 and HaCaT.

Ce manuscrit de thèse est composé de trois parties dédiées aux développements technologiques nécessaires à l'étude de la polarité et des contraintes mécaniques dans les cellules épithéliales. La première partie décrit les développements technologiques et méthodologiques qui ont été réalisés en micro-fabrication et traitement de surface, acquisition et analyse d'image, et mesure des forces de traction. La deuxième partie décrit l'étude de l'organisation spatiale du système d'adhérence des cellules épithéliales. De la régulation de leur polarité à celle de leur fonction, l'architecture des cellules épithéliales est profondément liée à leur système d'adhérence. Nous avons utilisé les micropatrons adhésifs pour contrôler la géométrie de la matrice extra-cellulaire pour examiner l'effet de l'adhérence des cellules avec la matrice sur la position des zones d'adhérence intercellulaire. Nos résultats montrent que l'organisation spatiale de l'adhérence cellule-matrice joue un rôle déterminant sur celle de l'adhérence intercellulaire. Ils montrent également que cette organisation dirige ensuite la position du centrosome et l'orientation de l'ensemble de la polarité interne. Lors d'une réorganisation spatiale de l'épithélium, comme c'est le cas au cours de la transition épithélium-mésenchyme, les systèmes d'adhérence et la polarité interne subissent tous les deux de profondes modifications. Néanmoins, les cellules semblent capables de les réguler de façon indépendante selon le type de stimulus qui induit la réorganisation. La dernière partie est une analyse des paramètres physiques impliqués dans l'architecture épithéliale. En parallèle des régulations biochimiques, les contraintes mécaniques jouent également un rôle fondamental dans la régulation des processus morphogenétiques. L'association de l'ensemble de nos développements technologiques (patterning de substrat déformable, logiciel de détection et de mesure de force, contrôle du positionnement des cellules) nous a permis d'analyser précisément les propriétés mécaniques des architectures multicellulaires. Nous avons découvert que l'organisation spatiale du système adhérence était un régulateur majeur de l'intensité et de la répartition des forces intra-cellulaires. Cette observation nous a permis de proposer une modification du modèle actuel de distribution des contraintes dans un épithélium qui prend en compte l'anisotropie des forces inter-cellulaires en réponse à l'hétérogénéité de la matrice extra-cellulaire. Ce nouveau modèle physique permet de rendre compte des positions adoptées par les cellules en réponse aux différentes géométries de la matrice extra-cellulaire. / This thesis dissertation is comprised of three major parts. The first part devotes to all the technological developments that have been realized in my thesis study. These developments in microfabrication, in image acquisition and analysis, and in the traction force analysis had solved various problems we have encountered during our study of epithelial architecture. The second part describes the study of the spatial organization of the adhesion systems in epithelia. From their polarity, their functioning, to their remodeling, the epithelial architecture is deeply linked with the adhesion systems. With the capability to well define the location of cell-matrix interaction, we examined how the intercellular adhesion was organized according to the cell-matrix adhesion. Our results highlighted the instructive role of cell-matrix adhesion in organizing the intercellular adhesion. This organization subsequently governed the internal polarity which was indicated by the centrosome positioning. During epithelial remodeling, both the adhesion system and internal polarity were subjected to modification. Nevertheless they could be regulated differently depending on the context of remodeling. The last part is focused on the physical aspect of the epithelial architecture. Apart from the biochemical signaling network, mechanical force is also a substantial ingredient in morphogenesis. Together with our techniques in micropatterning the soft gel, the development of software for traction force microscope, and our knowledge of cell-cell positioning, we were able to analyze precisely the mechanical property of the multicellular architecture. We found that the cellular contractility was modulated by the spatial organization of the adhesion system. It permitted us to complete the current physical model of epithelial geometry with an anisotropic term for contractility. This new physical model could effectively account for the cell positioning on various matrix geometries.