El objetivo principal de la presente tesis es presentar la teoría de las familias normales y mostrar su importancia en la teoría de grupos discontinuos y discretos. Primero haremos un estudio de las propiedades de las transformaciones de Moebius y luego su clasificación por conjugación. Para así introducirnos en la teoría de familias normales para funciones holomorfas y meromorfas. A partir de ello probaremos algunos resultados de normalidad para transformaciones de Moebius en especial el teorema fundamental de normalidad para transformaciones de Moebius. Finalmente veremos que un grupo Γ de transformaciones de Moebius es discontinuo en un punto α si y solo si Γ es discreto y forma una familia normal en α. / Tesis

This dissertation presents the kinematics study on two cases of parallel locomotion mechanisms. A parallel locomotion mechanism can be defined as "a mechanism with parallel configuration and discrete contact with respect to the ground which renders a platform the ability to move". The first case is a tripedal robot and the second case is an actuated spoke wheel robot. The kinematics study on these two mobile robots mainly includes mobility, inverse and forward kinematics, instantaneous kinematics, singularity and so on. The tripedal robot STriDER (Self-excited Tripedal Dynamic Experimental Robot) is expected to walk utilizing its built-in passive dynamics, but in its triple stance phase, the kinematic configuration of the robot behaves like an in-parallel manipulator. The locomotion of this novel walking robot and its unique tripedal gait are discussed, followed by the definitions of its coordinate frames. Geometric methods are adopted for the forward and inverse displacement analysis in its triple stance phase. Simulations are presented to validate both the inverse and the forward displacement solutions. The instantaneous kinematics and singularity analysis are developed respectively. Based on the screw theory, the Jacobian matrices are assembled. Using Grassmann Line Geometry, each row of the Jacobian matrices is interpreted as a line in 3D space and the analytical conditions of the linear dependency cases are identified, which corresponds to the forward singular configurations of the robot. The actuated spoke wheel robot IMPASS (Intelligent Mobility Platform with Active Spoke System) is investigated as the second case. It is revealed that this robot has multiple modes of locomotion on the ground and it is able to change its topology by changing the contact scheme of its spokes with the ground. This robot is treated as a mechanism with variable topologies and Modified Grübler-Kutzbach criterion and Grassmann Line Geometry are adopted to identify the degrees of freedom (DOF) for each case of its topological structures. The characteristic DOF are then verified through the testing on the robot prototype. The forward and inverse kinematics is investigated for two cases of its topologies. In order to improve the computation efficiency of the inverse kinematics formulation, virtual serial manipulator models are constructed. The effectiveness of the virtual serial manipulator models has been validated with numerical simulations. In conclusion, kinematics analyses have been successfully performed on the two parallel locomotion mechanisms. The results are utilized to control the robots' motions in specific configurations. The foundation has been laid for the future development of the robot prototypes and the future research on dynamics, control, intelligence and so on. / Ph. D.

This thesis focuses on the study, implementation and improvement of a digital Generator Control Unit (GCU) for a high-speed synchronous brushless generator. The control of variable frequency power system, a preferred candidate in More Electric Aircraft (MEA), becomes a big challenge. Compared with conventional analog GCU, digital GCU is a future trend due to the properties such as easy tuning, modification and no aging. Control approaches adopted in the new GCU design is introduced. It has multiloop structure and model-based characteristics. Sensorless rotor position detection was used to finish Park transformation. DSP+FPGA based controller hardware was developed in the lab. A set of hardware was designed to implement the control algorithms. VHDL-based software was developed for FPGA, which is working as a bridge between DSP and peripheral circuits. C-based software was designed to implement control algorithm inside DSP. A testbed system was developed according to the lab capacity of CPES. The complete load transit responses were tested according to the standard ISO1540 and EN8420. Good match between simulation and experiment has been reached. Compared with benchmark controller, great improvement in both steady state and dynamic performance is realized. A feasibility of using digital GCU in the next generation aircraft has been proved preliminarily. However, the challenge of reliability issues in digital system and software still needs further attention. / Master of Science

The object of this paper is to define the elementary transcendental functions of a complex variable by means of integrals, and to discuss their properties.

La transcriptómica estudia el nivel de expresión de los genes en distintas condiciones experimentales para tratar de identificar los genes asociados a un fenotipo dado así como las relaciones de regulación entre distintos genes. Los datos ómicos se caracterizan por contener información de miles de variables en una muestra con pocas observaciones. Las tecnologías de alto rendimiento más comunes para medir el nivel de expresión de miles de genes simultáneamente son los microarrays y, más recientemente, la secuenciación de RNA (RNA-seq). Este trabajo de tesis versará sobre la evaluación, adaptación y desarrollo de modelos estadísticos para el análisis de datos de expresión génica, tanto si ha sido estimada mediante microarrays o bien con RNA-seq. El estudio se abordará con herramientas univariantes y multivariantes, así como con métodos tanto univariantes como multivariantes. / Tarazona Campos, S. (2014). Statistical methods for transcriptomics: From microarrays to RNA-seq [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48485 / Premios Extraordinarios de tesis doctorales

Thesis advisor: Matthias von Davier / The transition of major international large-scale assessments (ILSAs) from paper- to computer-based assessments has made process data increasingly available. While process data is potentially valuable for analyzing students’ test-taking behaviors, it also raises ethical concerns and involves considerable costs. This prompts the question: “Does process data add value to the analysis of ILSA data?” In response, this dissertation explores the utility of process data through three studies. Study 1 proposes a multiple-group hierarchical speed-accuracy-revisits model to examine the gender differences in mathematics ability, response speed, revisit propensity, and the relationships among them. The model’s flexibility allows it to be applied in diverse contexts to investigate group differences in test-taking behaviors and achievement beyond gender. Study 2 addresses the overparameterization challenge in ILSA scaling by proposing a new approach: adding process variables to the usual contextual variables and replacing principal component analysis with variable selection for latent regression modeling. The findings show that process variables consistently improved measurement precision; using Lasso, random forests, and ultimately gradient boosting for variable selection achieved or surpassed the measurement precision of the conventional approach but with considerably fewer covariates. Integrating variable selection and process data yielded the highest measurement precision while achieving parsimony, demonstrating the effectiveness of the proposed method. Study 3 investigates students’ test-taking behaviors in the context of girls consistently outperforming boys on average across countries and assessments. Three types of test-taking behaviors were identified through latent class analysis: “Rapid”, “Challenged”, and “Engaged”. Using Bolck-Croon-Hagenaars and three-step methods reveals that girls in the “Rapid” class outperformed boys on average in all countries, while there were no significant gender differences in the “Engaged” class in three of the four countries. The gender gap in reading achievement may diminish to a mild to moderate extent if boys were to behave like girls, highlighting the importance of addressing disengagement issues in ILSAs. Collectively, these three papers advance the use of process data and demonstrate its value for analyzing and reporting results of ILSA data. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Lynch School of Education. / Discipline: Education.

No / This paper studies the selective maintenance problem for multi-state series systems working in variable loading conditions in the next mission. In the mission, a component's degradation depends on its current state and the load applied on it. A load-dependent degradation model is proposed for multi-state components operating in variable loading conditions. This model is inspired by the load-sharing model where many components share a common workload and the failure rate of a component depends on the state of other components. A Monte-Carlo simulation method is presented to simulate the multi-state component's degradation and to evaluate the system reliability. The final objective is to determine the best selective maintenance strategy to maximize the expected system reliability in the next mission within available resources. An illustrative example, reliability estimation results, and analysis of optimal selective maintenance scenarios for different levels of budget limitation are provided.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

<p dir="ltr">Additive manufacturing continues to show great promise for use in structural components due to the cost effectiveness and reduced complexity associated with optimized and targeted use of the method. However, before additive manufacturing can be widely accepted a more complete understanding of the material performance and microstructural features must be achieved. This thesis aims to further the understanding of cold dwell fatigue in additively manufactured Ti-6Al-4V and explore targeted microstructural control of additively manufactured Ti-6Al-4V through the use of printing parameter variations and hot isostatic pressing.</p><p dir="ltr">In the first portion of this thesis, experimental work was conducted to explore the effect of periodically applied load dwell and overloads on the stress-life relationship for additively manufactured Ti-6Al-4V. Samples printed using an optimized print parameter set, heat treated using hot isostatic pressing, machined, and longitudinally polished were tested across a variety of loading schemes including: constant amplitude, periodic dwell, periodic overload, and alternating periodic dwell and periodic overload. It was determined that, for the parameter set studied, periodic overload provided similar damage compared to constant amplitude cases, while periodic dwell provided greater damage compared to both constant amplitude and periodic overload cases. Additionally, a phenomenological failure prediction model for dwell, variable amplitude loading was created. The developed model combines the effects of plasticity and creep with an energy-based approach rooted in the fundamental behavior of the material.</p><p dir="ltr">In the second portion of this thesis a review of the literature is presented to explore the use of hot isostatic pressing in additively manufactured Ti-6Al-4V. The literature review holds the primary purpose of deepening the understanding of the relationships between hot isostatic pressing and microstructural control and how they are taken together to improve fatigue performance. The literature review explores many aspects of factors impacting fatigue life and how the additive manufacturing process impacts material microstructure. The final conclusion of the literature review is that 1 micrometer is the largest pore expected to achieve complete closure though hot isostatic pressing, that 40 micrometer is the critical pore size for fatigue failure, and the process for microstructural evolution during pore closure is dominated by creep and dynamic recrystallization. Using these facts targeted microstructural control can be explored to optimize fatigue performance through purposeful microstructural variations.</p>