Author: LUMBRERAS CARRASCO, DAVID
Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
Programme: DOCTORAL DEGREE IN ELECTRONIC ENGINEERING
Department: Department of Electronic Engineering (EEL)
Mode: Normal
Deposit date: 27/05/2022
Reading date: pending
Reading time: pending
Reading place: pending
Thesis director: ZARAGOZA BERTOMEU, JORDI | MON GONZÁLEZ, JUAN
Committee:
     PRESIDENT: ROMERO CADAVAL, ENRIQUE
     SECRETARI: LAMICH AROCAS, MANUEL
     VOCAL: ESPINA MASRAMON, JORGE
Thesis abstract: Electrical and electronic equipment needs sinusoidal currents and voltages to function properly. Equipment such as computers, household appliances, electric vehicle chargers, and LED lights can distort the grid and worsen grid quality. Distorted electrical grids can cause malfunctions, reduce service life, and decrease the performance of connected equipment. Industry commonly solves these problems using active power filters, which can minimise the harmonics of the grid, eliminate undesirable reactive power, and restore balance to unbalanced power grids.This thesis deals with the design and implementation of an active power filter based on wide-bandgap semiconductors, which have properties that are superior to classical silicon devices. An active power filter¿s design must take advantage of these benefits to build converters that are smaller, more efficient, and consume fewer resources. However, wide-bandgap semiconductors also present design challenges. Because the most commonly used active power filters in the industry are based on two-level voltage source converters, the research for this doctoral thesis focuses on this converter topology. Moreover, its main objective is to contribute new modulation techniques that are specially designed to work with wide-bandgap semiconductors. The proposed modulations consider different aspects, such as the computational cost of the algorithms, converter losses, and the electromagnetic distortion generated.First, this thesis presents a hexagonal sigma-delta (H-S¿) modulation based on sigma-delta (S¿) modulation. The properties of this modulation are studied, and the technique is compared with other widely used modulations. The comparison considers efficiency, harmonic distortion, the electromagnetic compatibility of the converter, and the type of wideband semiconductor used. In addition, a fast algorithm is mathematically developed to simplify the presented modulation and reduce its computational cost.Secondly, this thesis presents a family of sigma-delta modulations specially designed to improve electromagnetic compatibility: the reduced common-mode voltage sigma-delta (RCMV-S¿) modulations. These modulations avoid using the vectors that generate the maximum common-mode voltage, which significantly reduces the generated electromagnetic distortion without affecting the performance of the converter and its harmonic distortion. Finally, the proposed modulations are applied in a wide-bandgap power converter working as an active filter. Thus, it is verified that the techniques presented in this thesis will obtain satisfactory results when implemented in commercial active power filters.

Author: CARDOSO DUARTE, AMANDA
Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
Department: Department of Signal Theory and Communications (TSC)
Mode: Normal
Deposit date: 24/05/2022
Reading date: 27/06/2022
Reading time: 16:00
Reading place: ETSETB- D5-010 link videoconferència: https://meet.google.com/acd-dukb-ywq
Thesis director: GIRÓ NIETO, XAVIER | TORRES VIÑALS, JORDI
Committee:
     PRESIDENT: SMEATON, ALAN
     SECRETARI: SAYROL CLOLS, ELISA
     VOCAL NO PRESENCIAL: ROGEZ, GRÉGORY
Thesis abstract: Signed languages are complete and natural languages used as the first or preferred mode of communication by millions of people worldwide. However, they, unfortunately, continue to be marginalized languages. Designing, building, and evaluating models that work on sign languages presents compelling research challenges and requires interdisciplinary and collaborative efforts. The recent advances in Machine Learning (ML) and Artificial Intelligence (AI) has the power to enable better accessibility to sign language users and narrow down the existing communication barrier between the Deaf community and non-sign language users. However, recent AI-powered technologies still do not account for sign language in their pipelines. This is mainly because sign languages are visual languages, that use manual and non-manual features to convey information, and do not have a standard written form. Thus, the goal of this thesis is to contribute to the development of new technologies that account for sign language by creating large-scale multimodal resources suitable for training modern data-hungry machine learning models and developing automatic systems that focus on computer vision tasks related to sign language that aims at learning better visual understanding of sign languages.Thus, in Part I, we introduce the How2Sign dataset, which is a large-scale collection of multimodal and multiview sign language videos in American Sign Language. In Part II, we contribute to the development of technologies that account for sign languages by presenting in Chapter 4 a framework called Spot-Align, based on sign spotting methods, to automatically annotate sign instances in continuous sign language. We further present the benefits of this framework and establish a baseline for the sign language recognition task on the How2Sign dataset. In addition to that, in Chapter 5 we benefit from the different annotations and modalities of the How2Sign to explore sign language video retrieval by learning cross-modal embeddings. Later in Chapter 6, we explore sign language video generation by applying Generative Adversarial Networks to the sign language domain and assess if and how well sign language users can understand automatically generated sign language videos by proposing an evaluation protocol based on How2Sign topics and English translation.

Author: CASTILLO ESCARIO, YOLANDA
Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
Programme: DOCTORAL DEGREE IN BIOMEDICAL ENGINEERING
Department: Department of Automatic Control (ESAII)
Mode: Article-based thesis
Deposit date: 30/05/2022
Reading date: 27/06/2022
Reading time: 10:00
Reading place: Sala Actes de l'Escola d'Enginyeria Barcelona Est (EEBE), Campus Diagonal Besòs, Av. d'Eduard Maristany, 16, 08019 Barcelona
Thesis director: JANE CAMPOS, RAIMON
Committee:
     PRESIDENT: REILLY, RICHARD
     SECRETARI: VALLVERDU FERRER, MARIA MONTSERRAT
     VOCAL: CARRAULT, GUY
Thesis abstract: Spinal cord injury (SCI) is one of the leading causes of disability worldwide. SCI causes motor and sensory impairment but is also associated with many other health problems. Two of these problems are trunk muscle impairment and sleep disorders. Impaired trunk function affects postural control and sitting balance, which are critical for activities of daily living. Disturbed sleep causes fatigue and sleepiness and can lead to serious comorbidities, impacting patient recovery and outcomes. However, due to the multiple health problems secondary to SCI and the limitations in current diagnostic tools, trunk function and sleep are rarely examined after SCI. The non-invasive acquisition and analysis of biomedical signals can help to overcome this issue, providing quantitative measures to assess patient condition. Smartphones can facilitate this task, thanks to their ubiquitous presence and powerful sensors.The aim of this PhD thesis is to propose new smartphone-based tools and biomedical signal analysis techniques for the quantitative assessment of trunk function and sleep-disordered breathing (SDB) in patients with SCI. This dissertation is divided into two parts, including four publications in high-impact journals. The first part addresses the characterization of trunk function in healthy subjects and patients with cervical (cSCI) and thoracic SCI (tSCI). The second part focuses on the development of a mobile health (mHealth) system based on smartphone audio signals for obstructive sleep apnea (OSA) diagnosis, and the detection and monitoring of SDB in SCI patients.The first part of the thesis introduces a novel methodology to quantitatively evaluate trunk function by combining electromyography (EMG) and smartphone accelerometry. In the first study, we characterized the muscle activity and movement patterns of trunk flexion during reaching in healthy humans and investigated if trunk stability was affected by a startling acoustic stimulus (SAS). We found that SAS markedly reduced the response time (RespT) and EMG onset latencies of all muscles (the so-called StartReact effect), either prime movers or stabilizers. In the second study, we evaluated trunk function and the effects of a SAS in patients with cSCI and tSCI. The results revealed deficits in postural control and compensatory strategies employed by SCI patients, such as delayed responses and high lateral deviations, with potential consequences for rehabilitation. This was the first study investigating the StartReact responses in trunk muscles in SCI. The SAS significantly shortened the RespT in tSCI, but not in cSCI, which suggests an increased cortical control in cSCI.In the second part of the thesis, we present mHealth tools for monitoring sleep disorders and investigate the sleep patterns of SCI patients. In the first article of this part, we designed a smartphone system and novel algorithms based on acoustic analysis for OSA screening. This approach demonstrated good agreement with a commercial system for home OSA diagnosis, correctly detecting and stratifying all the OSA patients. In the last article, sleep studies were performed in SCI patients using the smartphone, showing a very high prevalence of moderate-to-severe SDB in SCI patients. This study highlighted the problem of SDB in SCI and provided simple cost-effective tools to improve the detection and management of SDB in SCI patients.Overall, this thesis supports the use of smartphones and biomedical signal analysis for the assessment of trunk function and SDB in SCI patients. These novel approaches provide quantitative and objective measures for the evaluation and follow-up of patients in a simple and non-invasive way. We also give insights into the underlying mechanisms of postural control, respiratory function during sleep, and the changes occurring after SCI. Consequently, our results open the way for improving the management of health complications associated with SCI or other disabling conditions.

Author: QUIRÓS COLLAZOS, LUCÍA
Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
Programme: DOCTORAL DEGREE IN MARINE SCIENCES
Department: (DECA)
Mode: Normal
Deposit date: 22/04/2022
Reading date: 27/06/2022
Reading time: 10:00
Reading place: ETSECCPB - Saló d'Actes Ramon Margalef de l'Institut de Ciències del Mar del CSIC.
Thesis director: CALVO COSTA, EVA | PELEJERO I BOU, CARLES
Committee:
     PRESIDENT: FLORES VILLAREJO, JOSE-ABEL
     SECRETARI: CERMEÑO AÍNSA, PEDRO
     VOCAL: VILLANUEVA ALVAREZ, LAURA
Thesis abstract: The present PhD thesis is focused on the paleoclimatic reconstruction of the Pacific Ocean equatorial upwelling conditions, east of the Galapagos Islands, over the last 160.000 years. This region is of great interest to understand climate dynamics within the context of current global change, as it plays a key role in global biogeochemical cycles, especially the carbon cycle, being one of the areas with largest CO2 fluxes from the ocean to the atmosphere. In addition, studies covering the recent decades have shown that tropical regions play a key role in regulating global climate, since they control the transfer of thermal energy from low to high latitudes.This study is based on the analysis of molecular biomarkers in the marine sediment core ODP 1240, which was obtained during Leg 202 of the Ocean Drilling Program. The main analysed compounds were the long-chain ketones, known as C37 alkenones, the 24-methylcholesta-5,22-dien-3ß-ol, known as brassicasterol, long-chain n-alkanes, glycerol dialkyl glycerol tetraethers (GDGTs) and 1,14-alkyl diols.The UK'37 and TEXH86 indexes were obtained from the analyses of the mentioned biomarkers to assess their suitability as temperature proxies to reconstruct sea surface conditions at the eastern Pacific upwelling on a glacial-interglacial time scale. They reflect variations in the mean annual surface temperature at the study area and track the warming and cooling trends typical of glacial-interglacial variations, although with certain peculiarities associated with each proxy. The UK'37 derived record shows a special sensitivity to periods with La Niña-like seasonal conditions, when the upwelling was more intense and sea surface temperatures in this area were colder. On the other hand, the TEXH86 index shows a tendency to overestimate the cooling of surface waters during glacial periods, as it has been also observed in similar reconstructions in this and other tropical regions. This might be due to the combined influence of changes in surface temperature and in ammonium oxidation rates of the Thaumarchaeotas that synthesize GDGTs and proliferate in the upper water column.Paleoclimatic information provided by other records nearby indicate that changes in oceanic denitrification linked to the supply of oxygen through subsurface and intermediate waters could have a regulating effect on the availability of ammonium in surface water. This, in turn, would have led to changes in the relative abundance of the GDGTs synthesized by Thaumarchaeotas, causing a glacial cooling overestimation through the TEXH86 index.The high resolution that characterizes the ODP 1240 core has allowed gaining a more in-depth knowledge on the millennial-scale climatic variability of this region. In particular, the changes in primary production during the penultimate deglaciation have been studied. This deglaciation, known as Termination II, can be used as a laboratory to understand climate dynamics during periods of rapid global warming. The results show that phytoplankton production was enhanced by an increasing influence of nutrient-rich Southern Ocean-sourced waters and by enhanced atmospheric dust inputs, which would have served as an additional source of iron to the study region. These processes culminated during the development of the Heinrich Event 11 in the North Atlantic, at a time when the highest increase in primary productivity of Termination II was recorded in the eastern equatorial Pacific upwelling. The results of this thesis highlight the relationships between global dynamics of biogeochemical cycles and those of the eastern equatorial Pacific, as well as the role played by high to low latitude teleconnections.

Author: ALFARO ARAGÓN, CARLOS ARTURO
Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
Programme: DOCTORAL DEGREE IN ELECTRONIC ENGINEERING
Department: Department of Electronic Engineering (EEL)
Mode: Article-based thesis
Deposit date: 02/05/2022
Reading date: 28/06/2022
Reading time: 12:00
Reading place: EPSVG - Videoconferència https://meet.google.com/chf-vxcd-enn
Thesis director: GARCIA DE VICUÑA MUÑOZ DE LA NAVA, JOSE LUIS | GUZMAN SOLA, RAMON
Committee:
     PRESIDENT: FIGUERES AMORÓS, EMILIO
     SECRETARI: CASTILLA FERNANDEZ, MIGUEL
     VOCAL: GARCERÁ SANFELIU, GABRIEL
Thesis abstract: This doctoral thesis focuses on the modeling and control of electrical microgrids and triphasic converters. The starting points of this research work are based on previous work on modeling electrical microgrids working in isolated mode, and on the theoretical basis of control based on the slope method, widely studied in electrical microgrids. In addition, this work is basedon previous work on predictive control applied to three-phase converters, and on the theoretical bases of this type of control widely used in Power Electronics. The main contribution of this doctoral thesis is the deduction of a large-signal mathematicalmodel that describes the dynamics of the active and reactive powers that flow through converters connected in the microgrid.This proposal will make it possible to obtain new control techniques for three-phase converters connected in microgrids, suchas model-based predictive control, for example. It should be noted that the use of this model can be used as a tool to deducethe global stability of the microgrid. The systems treated in this thesis are a three-phase rectifier with a unity power factor anda three-phase microgrid composed of five three-phase inverters.