Escuela de Ingeniería (TECNUN) - Tesis Doctorales y Tesinas - 2021-2025
Permanent URI for this collectionhttps://hdl.handle.net/10171/60382
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49 results
Results
- Tailored bam shaping techniques for enhanced ultrashort pulse laser processing.(2024) Fantova-Sarasa, J. (Jorge); Garcia-Mandayo, G. (Gemma); Rodríguez-González, A. (Ainara)Ultrashort pulse (USP) laser processing has set a new standard in the manufacturing industry due to its high precision and its capacity to engrave nearly all materials. This technology has been introduced in sectors such as automotive, aerospace and electronics for tasks such as micro-drilling or surface structuring. However, some challenges to the widespread use of USP laser processing include improving fabrication speed and exibility to meet industrial demands. Beam shaping techniques, which involves altering the amplitude, phase, or polarization of laser beams, have emerged as a convenient solution to address these issues, as they allow for more ecient, versatile, and high-resolution material processing. In this thesis, various beam shaping strategies are explored to boost the throughput and applicability of USP laser manufacturing processes. In particular, the experimental work is divided into three main parts, each focusing on a dierent type of beam shaping. The rst part investigates the optimization and application of Bessel beams for generating volume diraction gratings in dierent glasses. It includes the study of nonlinear laser-matter interactions during irradiation of each material and examines its eect on the morphological and optical properties of the resulting volume modications. By ne-tuning the laser writing parameters, ecient phase elements suitable for multiple applications are produced in all types of glass in a single laser pass. The second part examines the use of triangular beams to streamline asymmetrical surface machining. This novel manufacturing method was employed to engrave grooves with a wide range of geometries in a single step. Additionally, it enabled the straightforward fabrication of blazed gratings on stainless steel, with features similar to those manufactured using conventional methods. The third part focuses on the generation of multilevel at-top beams and its application in USP laser polishing. To optimize light structuring, several diractive optical elements (DOEs) were manufactured using a femtosecond (fs) laser-assisted lithographic process. The results of this line of work demonstrate the importance of the design and fabrication of the DOEs to ensure homogeneous beam shaping and uniform processing using an USP laser source. Overall, this thesis presents new strategies to enhance the precision and eciency of ultrashort pulse (USP) laser material processing. The ndings contribute to the broader eld of laser microfabrication and have clear implications in industrial applications.
- AIDIP methodology for integrating standardization into collaborative research projects – Focus on smart and resilient cities(Servicio de Publicaciones. Universidad de Navarra, 2024-07) Lindner, R. (Rene); Jaca-García, C. (Carmen); Hernantes-Apezetxea, J. (Josune)The European Commission fosters the integration of standardization in its Framework Programs since a decade to disseminate and exploit the project results, thus increasing the projects’ impacts to transfer research results into practice. Especially complex topics such as city resilience need urgently research results to face the increasing hazards they are facing. However, there is a lack of a common approach for integrating standardization in collaborative research projects. Furthermore, these projects have the difficulty to engage the relevant stakeholders properly and to foster the application of the resulting standards. This research addresses these issues by proposing the AIDIP methodology, which includes the Analysis of standardization landscape, the Identification of end-user needs and standardization potentials, the Definition of a standardization strategy, the Initiation of standardization activities, and the Promotion and exploitation of conducted standardization work. In addition, the research showed that standardization supports the engagement of project stakeholders and that gathered factors to support the application of standards at city level are appropriate.
- Design and assessment of a 2 MW High-temperature superconducting electric motor for regional aircraft propulsion.(Servicio de Publicaciones. Universidad de Navarra, 2024-07) Alvarez-Santos, P. (Pablo); Satrústegui-de-Legarra, M. (Marco); Martínez-Iturralde-Maiza, M. (Miguel)The objective of this Thesis is to investigate towards the increase of power density and reliability of electric motors for aeronautic electric propulsion. To achieve that, this work aims, firstly, to evaluate the current state of the art in aeronautical propulsion technology using electric machines. On this research, the emerging challenges concerning MW-class electric propulsion motors are discussed, identifying several technologies available to overcome those challenges. Moreover, some conclusions about the contribution of motor technology to the feasibility of short-term electrification of single aisle regional aircraft are pointed out. Finally, the proceedings relative to the modelling of the insulation of high voltage electric machines and the arcing effects that may occur on the system are presented. Insulation assessment of electrical machines for aircraft propulsion is evaluated and several tests are proposed. The tests to be performed can be separated into two completely different blocks: dielectric strength tests of different materials and partial discharge tests of the complete winding of an electrical machine. A self-developed partial discharge inception voltage prediction model is also presented and validated with the results obtained from the partial discharge tests. The analysis carried out on the state of the art will provide information on the design guidelines that have been taken in recent years, as well as the different projects and studies that are planned for the medium-term future. Thanks to this framework, geometric and performance requirements of the motor are defined together with the objectives to be met. To achieve this goal, the design of a 2 MW partially superconducting salient-pole electric motor for the electric propulsion of a regional single-aisle aircraft, as an alternative of conventional turbines is presented. An innovative design with a vacuum chamber comprising both the resistive stator and the superconducting rotor is exposed, along with the assessment of a skewed winding. In order to validate the technological achievements of the presented motor, a lab-scale validator is proposed in terms of electromagnetic and thermal calculations, explaining the construction of the validator components, considering, as well its assembly and test procedures. Moreover, the oil- flooded cooling system is presented and validated with a CFD Model. Finally, the conclusions drawn from the different chapters are summarised, which will serve as a guideline for the further steps of the Thesis.
- Decoding algorithms for quantum error correcting codes.(Servicio de Publicaciones. Universidad de Navarra., 2024-07) Marti i Olius, A. (Antonio) de; Etxezarreta-Martínez, J. (Josu); Crespo-Bofil, P. (Pedro)Quantum computers would prove a ground-breaking effect in several re- search fields to the advantage of our society due to their proved capacity for solving some problems deemed as too complex for classical comput- ers. Consequently, there is a generalized academic effort for constructing a quantum computer. Nonetheless, a real quantum computer does not suffice for implementing quantum algorithms reliably, it must be fault-tolerant. Quantum computers undergo noise due to a phenomenon generally named quantum decoherence, a fault-tolerant quantum computer has the capabil- ity to suppress the effects of decoherence to an extent. For that to happen, a quantum computer should consider quantum error correction, a process in which decoherence is studied and attempted to be corrected. Within the context of quantum error correction, the information from quantum proces- sors is to be stored in a larger, more redundant system named a quantum error correcting code. Afterwards, one can obtain a vector named syndrome which provides partial information on the effect decoherence has had on a code. The process of recovering the decoherence or error that the code has undergone is named decoding. This thesis studies decoders for quan- tum error correcting codes, their performance, complexity and adaption to different types of quantum decoherence.
- Roadmap for business sustainability through operational excellence in emerging countries.(Servicio de Publicaciones. Universidad de Navarra, 2024-07) Henríquez-Machado, R.J.(Rafael José); Muñoz-Villamizar, A. (Andres); Santos-García, J. (Javier)This research is dedicated to investigating in Operational Excellence (OE) within emerging countries, with a primary focus on understanding its current state, constructing a conceptual model, formulating a maturity model, and outlining a strategic roadmap for advancement. The study aims to address a significant research gap concerning OE in emerging markets compared to developed nations, offering strategic guidance for organizations in these regions to enhance their operational effectiveness and longevity. This thesis is structured to delve comprehensively into OE within emerging economies, develop pertinent models, validate outcomes, and propose a structured plan for implementation. The research methodology utilized in this study entails a thorough examination of OE practices in emerging countries through both qualitative and quantitative analyses. By employing in- depth interviews, surveys, and case studies, the study intends to gather invaluable insights into the current state of OE in these regions and identify critical factors influencing operational excellence. The conceptual model developed in this research integrates various dimensions of OE, including process efficiency, quality management, and continuous improvement, thus offering a holistic framework for organizations to bolster their operational performance. Additionally, the proposed maturity model provides a structured approach for organizations in emerging countries to assess their current level of operational excellence and pinpoint areas for enhancement. Through benchmarking against best practices and industry standards, companies can chart a course for improving their operational capabilities and achieving sustainable growth. The study underscores the significance of leadership commitment, employee engagement, and organizational culture in driving OE initiatives and fostering a culture of continuous improvement. This research contributes significantly to the body of knowledge on OE in emerging economies by offering a thorough analysis of the current state of operational excellence, developing practical models for organizations to boost their operational performance, and presenting a roadmap for implementation. By bridging the gap between research in emerging and developed markets, this study aims to empower organizations in emerging countries to fortify their operational capabilities, drive sustainable growth, and attain long-term success in an increasingly competitive global landscape.
- Enhancing the deployment of vehicle-to-infrastructure (V2I) communications throughcomprehensive temporal approach.(Servicio de Publicaciones. Universidad de Navarra, 2024-07) Iturbe-Olleta, N. (Nagore); Mendizabal-Samper, J. (Jaizki); Brazález-Guerra, A. (Alfonso)In the future, mobility will be connected, cooperative, and autonomous where self-driven vehicles will coexist together with human-driven ones, resulting in a safer and more efficient traffic flow leading to a reduction of CO2 emissions, life loss, and time spent on the road. That is why, in achieving the goal of having connected, cooperative, and autonomous mobility Vehicle-to-Everything (V2X) communications play a key role as they enable the communication between vehicles and between vehicles and the surrounding environment (infrastructure, pedestrians, etc.). Therefore, to lay the foundation for this future, there has been a great deal of progress in recent years to enable the exchange of information from the vehicles on the road to the infrastructure through Vehicle to Infrastructure (V2I) communications. For the envisioned future of connected, cooperative, and autonomous mobility to become a reality, V2I deployments are essential. They facilitate seamless mobility across highways and urban environments. However, the landscape of V2I communications is continuously evolving, with new features being introduced regularly. This dynamic nature necessitates ongoing updates and adaptations, precluding the possibility of a definitive, one-time deployment. Moreover, as V2I technology is still in the development phase, new deployments will be imperative to accommodate the advancements in this field. In this thesis, we show that the real deployment of V2I communications is improved when three stages of a V2I deployment (initial deployment, enhancement, and future perspectives) are considered. In the context of this research work the three stages are: • Initial deployment: The establishment of infrastructure is crucial for facilitating V2I communications. This foundational phase significantly enhances the initial deployment of V2I communications during the earliest field installations. Decisions made during this critical stage have a lasting impact on the entire lifespan of the deployment, setting the groundwork for future scalability and effectiveness. Given that the initial installation cost is substantial, relocating the components from their original deployment positions incurs significant expenses. Enhancement: Ongoing supervision of the installed facility is paramount for integrating new features effectively. It is highly advisable to rigorously test these features before their field implementation to ensure minimal errors. This proactive approach guarantees the reliability and efficiency of the system as it evolves. • Future perspectives: Finally, all the acquired knowledge and experience assist when engineering new V2I designs and features.
- Enhancing bone regeneration: A mechanobiology-centric approach to TPMS-based bone replacements.(Servicio de Publicaciones. Universidad de Navarra., 2024-06) Asbai-Ghoudan, R. (Reduan); Rodriguez-Florez, N. (Naiara); Ruiz-de-Galarreta-Moriones, S.(Sergio)Cellular porous structures are increasingly used for biomedical applications. Triply Periodic Minimal Surfaces (TPMS) are mathematically defined cellular structures whose geometry can be quickly adjusted to achieve the desired mechanical response (structural and fluid). This has made them desirable as bioinspired materials for bone replacement. Scaffolds for bone replacements should be designed to respond to the mechanical environment: they should provide enough structural support during bone regeneration, while also enabling nutrient diffusion through its pores to allow cell proliferation and differentiation. Mechanobiology plays an important role in bone regeneration and understanding the interaction between the scaffold's geometry, its material, and the mechanobiological environment is required to improve tissue regeneration. The main purpose of this dissertation is to improve the understanding of the mechanical behavior and mechanobiological properties of TPMS structures to design bone replacements that can accurately mimic bone properties. The design of TPMS scaffolds was parametrized and automated to target bone porosity and pore size while maintaining a good manufacturability. Then, the structural and fluid flow properties of the scaffolds were assessed using Finite Element (FE) and Computational Fluid Dynamics (CFD) models respectively. The results were introduced into an uncoupled tissue differentiation model to predict the TPMS architectures that could be most promising to induce bone differentiation. Finally, a previously validated mechanobiological computational model (FE) was enhanced to evaluate the bone regeneration potential of complex porous structures and integrate the influence of patient-specific properties and clinical strategies to maximize bone regeneration. The obtained results showed that the permeability of the studied TPMS architectures was affected by pore distribution and architecture. In addition, a novel analytical model that enables the prediction of the permeability values of TPMS structures based on geometrical parameters was developed. The results also indicated that the TPMS Gyroid architecture was the most suitable for promoting tissue differentiation when considering both the structural and fluid flow properties. Furthermore, the computational mechanobiological model successfully assessed the ability of various scaffolds to promote bone regeneration, emphasizing the importance of scaffold’s geometry and material. The bone ingrowth within the scaffold pores demonstrated that the scaffold's geometrical properties influence cellular diffusion and strain distribution, resulting in differences in regenerated bone volume and distribution. Furthermore, bone ingrowth was found to be material-dependent, implying that the material can be used to fine-tune strain distribution and improve bone growth. Similarly, the use of clinical strategies and consideration of the host's physiological characteristics resulted in variations in bone regeneration, emphasizing the importance of incorporating such parameters into the design process of bone substitutes. In conclusion, this dissertation provides a framework for designing optimal patient-specific strategies to promote bone regeneration, thereby improving the conceptualization and design of bone replacements.
- Femtosecond laser-enabled precison additive manufacturing: process parameter optimization and surface roughness reduction(Servicio de publicaciones. Universidad de Navarra, 2024-06-28) Ramón-Conde, I. (Iñigo); Rodríguez-González, A. (Ainara); Gómez-Aranzadi, M. (Mikel)AM is one of the most advanced technologies in recent years, transforming the paradigms of many industrial processes. Among the various techniques available, the use of lasers has stood out for its versatility and efficiency; however, there are still certain design limits in terms of the materials that can be used, as well as a constant need to improve the quality and precision of manufacturing methods. Femtosecond lasers, belonging to the family of USP lasers, have the ability to affect substrates of many kinds with the singularity of a very low or negligible thermal effect; this minimal effect, which can a priori be a disadvantage if a significant heat build-up is desired, has been exploited to perform additive manufacturing studies and achieve higher degrees of precision in the LPBF technique. The studies carried out in this thesis demonstrate that it is possible to fuse stainless steel powder of different sizes with an appropriate choice of processing parameters, using low values of pulse spacing and accumulating the pulses along the powder bed. Although it is necessary to use a small powder size, this thesis has succeeded in obtaining high surface quality cast stainless steel structures below 1 W laser power and with a pulse repetition of 500 kHz, the lowest ever achieved to date, and in a material never studied before. This thesis also analyses the ability of the optimised parameters to fabricate structures with reduced thickness profiles, matching the records of other similar techniques for structures with a thickness of less than 100 µm. Finally, the femtosecond laser has also been used, in burst mode, to reduce the surface roughness of different substrates with different morphologies. Using the maximum pulse repetition and the highest number of pulses per burst, these studies have succeeded in reducing the roughness of metallic substrates by more than 60 %, obtaining different degrees of final finish depending on the processing conditions. It has also been demonstrated that the polishing process does not affect the morphology of the processed profiles, reducing the surface roughness and improving the appearance, but without damaging or affecting the original design of the polished substrate. The results of this thesis demonstrate that the femtosecond laser is a very powerful tool for applications beyond surface ablation and/or texturing, achieving very promising results both in the field of additive manufacturing and in the reduction of surface roughness and improvement of the final finish of parts, also linked to and necessary in many additive manufacturing processes.
- Development of an upper limb tele-rehabilitation home robotic device for post-stroke patients.(Servicio de Publicaciones. Universidad de Navarra, 2020-12) Ugartemendia-Etxarri, A. (Axier); Díaz-Garmendia, I. (Iñaki); Gil-Nobajas, J.J. (Jorge Juan)Stroke is currently the second most frequent cause of death after coronary artery disease and its prevalence is increasing at an alarming rate. Hemiparesis is the most common outcome of stroke leading to movement deficiency. Fortunately, rehabilitation can help hemiparetic patients to learn new ways of using and moving their weak arms and legs. It is also possible with immediate therapy that people who suffer from hemiparesis may eventually regain movement. Although there are several approaches, extensive task-specific repetitive movement is one of the safest and most effective methods to regain lost mobility of the affected limbs. This therapy requires incessant medical care and intensive rehabilitation often requiring one-on-one manual interaction with the physical therapist. Robotic rehabilitation for post-stroke therapies is an emerging new domain of application for robotics with proven success stories and clinical studies. New robotic devices and software applications are hitting the market intending to assist specialists carrying out physical therapies and even allowing patients exercising at home. Rehabilitation robots are designed to assist patients performing repetitive movements for a long time irrespective of skills and fatigue compared to manual therapy. A successful robotic device for rehabilitation demands high workspace and force feedback capabilities similar to a human physiotherapist. Currently, there are several devices in the market that give a robotic solution to these repetitive movements, and have been installed in many hospitals around the world. However, features mentioned are usually achieved at the expense of other important requirements such as transparency and backdrivability, degrading the overall human-machine interaction experience. Mechanically, this implies developing robots with high workspace and force feedback features. Such systems have in turn the drawback of being bulky and heavy degrading final interaction experience with the patient. Due to these facts, a new home robotic tele-rehabilitation device is presented in this thesis. The proposed solution is a mechatronic device capable of rehabilitating patients at their homes while they interact with personal computer games connected to the robot. The proposed system also allows monitoring the user performance for optimal therapy design. The second part of this thesis proposes a novel active gravity compensation technique based on machine learning that can highly improve the performance of mechatronic systems used for rehabilitation and many other domains of robotic applications. Traditional algorithms to obtain active gravity compensation usually require the static equilibrium equations of the system. However, for complex mechatronic configurations, solving these equations is not straightforward. The use of machine learning methods can achieve gravity compensation without the need to solve the equilibrium equations. The proposed novel technique is validated in the developed tele-rehabilitation device. The third part of this thesis focuses on improving the safety of this type of haptic devices through further evaluating the stability of haptic rendering. The theoretical and experimental implications of rendering virtual stiffness, damping and inertia is thoroughly evaluated.
- Reconstruction and analysis of gut microbiota metabolic networks in the context of personalized nutrition.(Servicio de Publicaciones. Universidad de Navarra., 2024-05) Blasco-Aramburu, T. (Telmo); Planes-Pedreño, F.J. (Francisco Javier)The gut microbiota refers to the collection of microorganisms coexisting in the human gut. It is well-established that various species within our gut microbiota metabolize nutrients derived from the diet, transforming them into key compounds that regulate human health. In particular, the composition of the intestinal microbiota is directly linked to the development of relevant diseases. Understanding the relationship between microbiota, diet and human health constitutes a primary objective in biomedicine that can be investigated from different approaches. Genome-scale metabolic reconstructions, developed in the field of Systems Biology, have grown enormously in recent years and constitute a very promising tool to develop computational models of the gut microbiota. However, this methodology has not reached an adequate level of maturity, making it necessary to improve existing reconstructions and algorithms for different applications. The main objective of this doctoral thesis is to improve existing metabolic reconstructions of the human gut microbiota, specifically integrating degradation pathways of diet-derived compounds of great relevance for human health, as well as to develop new algorithms that allow predicting and analyzing metabolic alterations of the gut microbiota in different contexts. This work is primarily divided into two parts. The first part focuses on improving existing metabolic reconstructions of the human gut microbiota. In this section, we introduce AGREDA, a repository of microbial metabolic models that includes metabolic pathways for a wide range of dietary compounds not represented in previous reconstructions. Among the different families of metabolites, we have considerably improved the representation of phenolic compounds, highly relevant for nutrition and human health. In addition, by means of metabolomic studies, we were able to validate the capacity of AGREDA to predict compounds derived from bacterial metabolism in the gut microbiota. The second part of this doctoral thesis involves the development of computational methods able to explore the metabolism of the human gut microbiota. Firstly, we developed q2-metnet, a QIIME2 plugin that allows inferring functional metabolic features of a microbial community by integrating 16S gene sequencing data and metabolic reconstructions. We observed that the metabolic predictions of q2-metnet can effectively classify a cohort of patients with various clinical conditions in comparison with competing algorithms. Finally, we present the BN-BacArena algorithm, which enable the dynamic modeling of bacterial communities considering microbe-microbe and nutrient-microbe regulatory interactions, empirically extracted using Bayesian Networks. We demonstrate with experimental data that BN-BacArena improves the ability of other methods in the literature to predict relative abundance of species.