Public display of deposited theses

DOCTORAL DEGREE IN CHEMICAL PROCESS ENGINEERING

• AGUILAR MORENO, MIGUEL: Liquid-Liquid membrane contactors for sustainable ammonia recovery and valorization: experimental insights, novel approaches and applications
  
  Author: AGUILAR MORENO, MIGUEL
  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 CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 16/04/2024
  Deposit END date: 29/04/2024
  Thesis director: CORTINA PALLAS, JOSE LUIS | VALDERRAMA ANGEL, CESAR ALBERTO
  Committee:
       PRESIDENT: DOSTA PARRAS, JOAN
       SECRETARI: GIBERT AGULLO, ORIOL
       VOCAL: REZAKAZEMI, MASHALLAH
  Thesis abstract: This comprehensive research represents a significant stride in the exploration of innovative strategies aimed at enhancing ammonia recovery within diverse wastewater streams. The study is structured into distinct phases, each addressing crucial aspects of the ammonia recovery process. In the initial phase, the research focuses on augmenting membrane contactor performance, employing coagulation-flocculation (C/F) and aeration as preliminary treatments. The outcomes of this phase demonstrate substantial increases in both the mass transfer coefficient and overall efficiency ofammonia recovery, particularly notable when treating the real sidestream centrate. A pivotal finding underscores the efficacy of dosing aluminum sulphate (Al2(SO4)3) at 30 mg Al+/L in the C/F process, yielding remarkable efficiencies in the removal of chemical oxygen demand (COD), turbidity, and total suspended solids (TSS). Into the second phase, the study delves into the sustainable application of liquid-liquid membrane contactors (LLMC) for ammonia recovery. An array of experimental conditions is meticulously explored, with the results illuminating the considerable impact of replacing the acid washing liquid between steps on the overall performance of the LLMC. Additionally, the study highlights the nuanced relationship between the initial ammonia concentration and the subsequent recovery, providing valuable insights. This phase effectively showcases the potential versatility and efficiency of LLMCs in the valorization of ammonia within wastewater streams. The third and final phase introduces a novel asymmetric hollow fiber liquid-liquid membrane contactor (HF-LLMC) with distinctive selectivity for ammonia over water. The investigation entails a comprehensive examination of various operational parameters, including feed and acid flow rates, mass transfer coefficients, and acid consumption. Notably, the results affirm the high selectivity of the HF-LLMC for ammonia, coupled with minimal water transfer. This establishes the HF-LLMC as a promising technology for the recovery and concentration of ammonium in diluted urban and industrial streams. The amalgamation of these findings, approached with a global perspective, significantly contributes not only to the advancement of sustainable nutrient recovery technologies but also underscores their pragmatic feasibility for implementation within the frameworks of the circular economy and efficient resource management.
  

DOCTORAL DEGREE IN CIVIL ENGINEERING

• GÓMEZ DUEÑAS, SANTIAGO: Unraveling Hydrological Dynamics: Climate and Human Implications in the Magdalena River Streamflow and its Interaction with Ciénaga Grande de Santa Marta Wetland
  
  Author: GÓMEZ DUEÑAS, SANTIAGO
  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 CIVIL ENGINEERING
  Department: (DECA)
  Mode: Normal
  Deposit date: 16/04/2024
  Deposit END date: 29/04/2024
  Thesis director: BATEMAN PINZON, ALLEN
  Committee:
       PRESIDENT: SOLÉ, AURELIA
       SECRETARI: DE MEDINA IGLESIAS, VICENTE CÉSAR
       VOCAL: LA ROCCA, MICHELE
  Thesis abstract: This study offers a comprehensive understanding of the hydrological dynamics of the Magdalena River (MR) basin, located in Colombia. Multiple elements that affect streamflow were analyzed, such as climate-forcing drivers and human-induced ones, to understand the complex interactions that shape the region's hydrology.Firstly, the influence of many factors on the flow of water downstream of the Magdalena River was studied. The research identified El Niño southern oscillation (ENSO) episodes as crucial climate-forcing drivers and human-induced modifications such as reservoir evaporation. The complex nature of streamflow changes over time was highlighted by showing the variations in the average, volume, and maximum streamflow, as well as oscillations in evaporation and minimum streamflow, especially during positive ENSO episodes. These findings offer important insights into the changing hydrological regime of the MR basin, emphasizing the complex combination of elements that influence its flow patterns throughout time.Moreover, the study explored the hydrological connection between the MR and the Ciénaga Grande de Santa Marta (CGSM) wetland, revealing the interdependence of these two ecosystems. For this, the study explores the vulnerability of downstream habitats, especially wetlands, to changes in streamflow inputs by taking a broad approach that views the entire wetland as a unified unit. It identified crucial threshold ranges where the inflow from the Magdalena River to the CGSM becomes uncertain. This analysis highlights the urgent need to understand the interactions between water flow and wetland ecosystems and their significant impact. Furthermore, the present research utilizes Long Short-Term Memory (LSTM) neural network models to predict streamflow changes at the Calamar gauging station. The goal was to improve the precision of streamflow predictions by combining data from several gauging stations and reservoir evaporation records. Finally, this study can help enhance the comprehension of the intricate hydrological processes in the MR basin, revealing the interconnected effects of climate fluctuations, human actions, and ecosystem dynamics. In this context, this research sets the foundation for creating well-informed water resource management strategies in Colombia that protect wetland ecosystems' ecological health and adaptability in the face of ongoing environmental changes.
  

DOCTORAL DEGREE IN COMPUTER ARCHITECTURE

• GÓMEZ SÁNCHEZ, GONZALO: Exploring genomic datasets through machine learning methods leveraging high-performance computing
  
  Author: GÓMEZ SÁNCHEZ, GONZALO
  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 COMPUTER ARCHITECTURE
  Department: (DAC)
  Mode: Normal
  Deposit date: 16/04/2024
  Deposit END date: 29/04/2024
  Thesis director: BERRAL GARCÍA, JOSEP LLUÍS | CARRERA PÉREZ, DAVID
  Committee:
       PRESIDENT: GARCÍA LÓPEZ, PEDRO
       SECRETARI: RUIZ RAMÍREZ, MARC
       VOCAL: CIRILLO, DAVIDE
  Thesis abstract: In recent years, the exponential increase of generated data has raised the need for implementing new methodologies to process the huge datasets being created. High-Performance Computing (HPC) brings together a set of technologies mainly based on parallel computing that help reduce the time expended analyzing these datasets. A research field where these technologies are needed is Computational Genomics. Furthermore, the complexity of the genomic datasets limits the use of basic conventional methods for the discovery of complex significant relations, introducing the need for Machine learning (ML) algorithms and robust statistical methods to better classify these variants. In the first part of the thesis, we aim to identify complex patterns of somatic genomic rearrangements in cancer samples, which are triggered by internal cellular processes and environmental factors. The problem of classification becomes particularly challenging when considering thousands of rearrangements at a time, often composed of multiple DNA breaks, increasing the difficulty in classifying and interpreting them functionally. Here we present a new statistical approach to analyze structural variants (SVs) from 2,392 tumor samples from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium and identify significant recurrence. The proposed methodology is able not only to identify complex patterns of SVs across different cancer types but also to prove them as not random occurrences, identifying a new class of pattern composed of three SVs that was not previously described. In the second part of the thesis, we approach another challenge of human genetics, which is the study of the relation between single nucleotide variants (SNVs) and complex diseases, such as Type 2 Diabetes, Asthma, or Alzheimer's. The study of these disease-variant associations is usually performed in a single independent manner, disregarding the possible effect derived from the interaction between genomic variants. Here, we have created a containerized framework that uses Multifactor Dimensionality Reduction (MDR) to detect combinations of variants associated with Type 2 Diabetes (T2D), called Variant Interaction Analysis (VIA). This methodology has been tested in the Northwestern University NUgene project cohort using a subset of 1,883,192 variant pairs with some degree of association with T2D and identifying a subset of 104 significant pairs, two exhibiting a potential functional relationship with T2D. The developed algorithm has been released in an open-source repository, including the containerized HPC framework, which can be used to search for significant pairwise interactions in other datasets.In both frameworks developed within the thesis, the use of large-scale supercomputing architectures has been a hard requirement to find relevant clinical indicators. To ensure open and broad access to HPC technologies, governments, and academia are pushing toward the introduction of novel computing architectures in large-scale scientific environments. This is the case of RISC-V, an emerging open standard instruction-set architecture. To evaluate such technologies, in the last two parts of the thesis, we propose the use of our VIA use case as a benchmarking, providing the first genomic application for RISC-V. With this use case, we provide a representative case for heavy ETL (Extract, Transform, Load) data processing. We developed a version of the VIA workload for RISC-V and adapted our implementation in x86-based supercomputers (e.g. Marenostrum IV at the Barcelona Supercomputing Center (BSC)) to make a fair comparison with RISC-V, since some technologies are not available there. With this benchmark, we have been able to indicate the challenges and opportunities for the next RISC-V developments and designs to come, from a first comparison between x86 and RISC-V architectures on genomic workload executions over real hardware implementations.
  

DOCTORAL DEGREE IN ELECTRONIC ENGINEERING

• PUSAY VILLARROEL, BENJAMÍN ANDRÉS: Fabricación de células solares con absorbedores inorgánicos emergentes y contactos selectivos
  
  Author: PUSAY VILLARROEL, BENJAMÍN ANDRÉS
  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: 17/04/2024
  Deposit END date: 30/04/2024
  Thesis director: PUIGDOLLERS GONZALEZ, JOAQUIN | ORTEGA VILLASCLARAS, PABLO RAFAEL
  Committee:
       PRESIDENT: ASENSI LÓPEZ, JOSÉ MIGUEL
       SECRETARI: PLACIDI, MARCEL JOSE
       VOCAL: RIERA LORENTE, SERGI
  Thesis abstract: Silicon is abundant in nature and plays a predominant role in the photovoltaic industry for generating electrical energy. However, the current cost of this solar technology remains high, especially at a commercial level where efficiency reaches 22%. One strategy to reduce the cost of solar energy production involves enhancing the efficiency of solar modules. This can be achieved by integrating new techniques and technologies into the manufacturing processes of the industry, along with the use of abundant and low-toxic materials.Multi-junction solar cells (tandem) enable the integration of two different technologies to leverage their respective qualities as light absorbers, thereby enhancing their electrical performance. Additionally, these cells facilitate the simplification and adoption of new techniques during the manufacturing process. With its Band Gap of 1.1eV, silicon stands out as an excellent candidate for the bottom cell in multijunction or tandem solar cells.The objective of this thesis is to enhance the efficiency of silicon solar cells by utilizing them as multijunction bottom cells to create tandem solar cells. This will be achieved by incorporating a front solar cell based on emerging technologies.To achieve this objective, the introduction is developed, which includes a brief state-of-the-art overview of silicon-based solar cells, the development of tandem solar cells, and the most promising alternatives for emerging inorganic absorbers with adjustable Band Gap, such as kesterites or chalcopyrites (e.g., CuGaSe). The theoretical analysis enables the selection of technologies and processes developed in available laboratories.The application of robust methods for depositing selective contacts in silicon is under investigation. This process aims to prepare the silicon for the thermal and chemical processes involved in the growth of inorganic solar cells, such as kesterites or CGS. This approach enables the development of a robust, efficient, and long-term multijunction solar cell.In a second section, the study on semi-transparent selective contacts for solar cells with inorganic absorbers, such as kesterites or CGS, is presented. The goal is to obtain a compatible substrate for tandem solar cells. As an alternative to traditional CdS for the ETL, we propose the use of Al2O3/TiO2/Mg,i:ZnO layers. Additionally, the potential of enhancing its characteristics by adding polymers (PEI, Glycine) as dipoles is studied.Regarding the hole transport layer (HTL), a semi-transparent alternative to the opaque MoSe2 layers was developed using V2Ox.This layer functions as an interface between the absorber and the transparent electrode (TCO). The incorporation of this layer into kesterite solar cells yielded a semi-transparent device with promising haracteristics, and its application has a significant impact on the efficiency of solar cells.In the last section, a manufacturing process for tandem solar cells is proposed, utilizing Silicon technology as the bottom cell and emerging inorganic solar cells, such as kesterite and CGS, as the top solar cell. Strategies are studied to create a monolithic two-terminal (2T) device, with attention to preserving the physical and electrical characteristics of each device throughout the manufacturing process and during chemical and thermal exposures. Additionally, a study is presented on strategies for the formation of a monolithic device with three interdigitated back contact (IBC) type terminals, which is crucial for obtaining efficient and stable devices in the long term.Through the implementation of these techniques, we anticipate contributing to the research and development of tandem solar cells based on abundant and sustainable materials. This advancement could significantly accelerate the global adoption of solar energy as a clean and renewable source.
  

DOCTORAL DEGREE IN GEOTECHNICAL ENGINEERING

• BISCARO, CATERINA: 3D FEM meso-level analysis of sulphate attack in concrete: new results and developments using parallel HP computing
  
  Author: BISCARO, CATERINA
  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 GEOTECHNICAL ENGINEERING
  Department: (DECA)
  Mode: Change of supervisor
  Deposit date: 16/04/2024
  Deposit END date: 29/04/2024
  Thesis director: CAROL VILARASAU, IGNACIO | XOTTA, GIOVANNA
  Committee:
       PRESIDENT: SALOMONI, VALENTINA
       SECRETARI: PRAT CATALAN, PERE
       VOCAL: LIAUDAT, JOAQUÍN
       VOCAL: MAROTTI DE SCIARRA, FRANCESCO
       VOCAL: CIANCIO, DANIELA
  Thesis abstract: When concrete is subject to an environment characterised by a high humidity index and rich in sulphate ions, a concrete degradation process may be initiated due to External Sulphate Attack (ESA). The sulphate penetrating into the concrete activates a series of chemical reactions that lead to the formation of secondary ettringite, which may cause non-uniform volumetric expansions that may in turn generate cracking and ultimately culminate in the disintegration of the sample. Because the cracking may in turn facilitate sulphate penetration, ESA may be considered a coupled chemical-mechanical problem. In this study, the numerical analysis of ESA is conducted using the Finite Element Method by considering the specimen at the meso-level composed of larger aggregates embedded in a mortar matrix. Standard continuum finite elements are used to discretise the aggregates and the mortar. Zero-thickness interface elements are inserted along all the aggregate-mortar and selected mortar-mortar contacts to represent potential cracks. The diffusion-reaction of sulphate ions (chemical problem) is formulated following Tixier and Mobasher (2003) and Idiart et al. (2011b). Regarding the mechanical problem, the continuum elements are considered linear elastic, while the interface elements behave according to an elasto-plastic law incorporating concepts of fracture mechanics which was initially developed by Carol et al. (1997) and later extended for 3D analysis by Caballero et al. (2006).The first part of this thesis deals with the verification and use of DRAC5, a completely parallelised version of the in-house code developed within the materials mechanics group (MECMAT) of the Universitat Politècnica de Catalunya (UPC) which now incorporates MPI and PETSC libraries as well as HDF5 i/o files. This new version of the code, which is used to solve both the mechanical problem and the chemical problem through a staggered scheme, has allowed the analysis of new and more challenging 3D studies, producing realistic results that reflect the 'onion peeling' cracking pattern, similar to what has been observed in the laboratory and in previously studied 2D cases (Idiart, 2009). The second part of the thesis, deals with the development of new numerical solving techniques applicable to this type of mesh. In particular, a solution technique based on substructuring and the Schur complement is applied to the analysis of specimens comprising elements of the continuum exhibiting linear elastic behaviour and interface elements characterised by non-linear (elasto-plastic) behaviour. This new technique, which reduces substantially the number of degrees of freedom that need to be considered during the iterative process, has been preliminarily implemented in DRAC4, a simpler series version of the code, and is tested showing great advantages in terms of solution time for a range of 2D application examples. The development of a new formulation using rigid-plastic interfaces is also initiated. This formulation uses relative degrees of freedom at each pair of interface nodes, and leads to the resolution of a Linear Complementarity Problem. This development allows a further reduction in the degrees of freedom of the problem by only considering the nodes of the interface elements involved in the fracture process.
  

DOCTORAL DEGREE IN MARINE SCIENCES

• ASTUDILLO GUTIERREZ, CARLOS SALVADOR: Posidonia oceanica: A Perspective From Coastal Protection
  
  Author: ASTUDILLO GUTIERREZ, CARLOS SALVADOR
  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: Article-based thesis
  Deposit date: 23/04/2024
  Deposit END date: 07/05/2024
  Thesis director: GRACIA GARCIA, VICENTE | CACERES RABIONET, IVAN
  Committee:
       PRESIDENT: COLOMER FELIU, JORDI
       SECRETARI: GIRONELLA I COBOS, FRANCESC XAVIER
       VOCAL: FERNÁNDEZ MORA, MARIA DE LOS ANGELES
  Thesis abstract: Over the decades, the global coastlines have been a key indicator of the development of actual societies. However, the cost of this growth has resulted in the depredation of natural environments. The increased frequency of storms, rising temperatures or rising sea levels are clear symptoms that the environment is responding to the increased pressure that the coasts have been subjected to. In recent years, the degradation of coastal habitats has accelerated, indicating that traditional engineering solutions alone will not be able to solve the problem in the long term. IThis approach enables nature to be reintroduced as a potential element capable of confronting and counteracting the adverse changes that the coastal landscape is undergoing. In order to achieve this goal, it is essential to conduct a comprehensive analysis of the natural elements that comprise the coastline, with a particular focus on identifying strategies that enhance environmental stability. This study aims to gain a deeper understanding of the impact of Posidonia oceanica seagrass meadows on the coastline, both in their submerged and emerged states.A novel experiment was conducted in the experimental flume CIEM of the LIM/UPC Barcelona. The objective was to evaluate the protective effect of submerged meadows against irregular erosive waves on a sandy beach with a 1:15 slope. A real meadow model was used with plastic substitutes carefully selected to accurately reflect the dimensions, movements and habitats of a real Posidonia oceanica plant. The submergence ratio and density of the meadow were kept constant. The work has focused on measuring the attenuation of wave height, changes in velocity, involvement in sediment transport and shore erosion. The results showed a persistent decrease in wave height from the area behind the meadow to the breaker zone, which was directly correlated with meadow length and wave energy. Consequently, there was less shoreline erosion as a function of wave height attenuation in cases where meadow was present, and even less when the meadow was longer. Behind the longer meadow, there was a notable change in velocity, resulting in an imbalance of peak velocities. This included a decrease in negative peak velocities and an increase in positive peak velocities. This resulted in an increase in the skewness value of the velocity in this area. The orbital velocities exhibited a decrease only for the long meadow case, which contributed to a decrease in sediment transport volume and the formation of a breaker bar closer to the coast.The emerged part of the meadows was evaluated through field work, analysing the accumulations on the shoreline. Several routes were taken along the southern Catalan coast in order to identify the most frequent accumulation sectors associated with the position of the submerged meadow. Areas with seagrass meadows were identified at depths greater than 5 m, and it was found that these areas exhibited a low frequency of occurrence of banquette events. Information on the management of the accumulations was obtained through interviews with the relevant personnel in each coastal municipality. The aim was to ascertain the manner in which the banquette is dealt with during periods of high tourism demand. Furthermore, this work presents a characterisation of parameters such as penetration resistance and permeability of the accumulations. Additionally, a methodology based on thermal oxidation has been presented to accurately quantify the amount of sediment that can accumulate in the banquettes. The results indicate that the banquettes situated in close proximity to the shoreline accumulated less sediment than those positioned at a greater distance from the coast.
  
• MASDEU NAVARRO, MARTA: Distribution and cycling of volatile organic compounds in a tropical coral reef and the adjacent ocean.
  
  Author: MASDEU NAVARRO, MARTA
  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: Article-based thesis
  Deposit date: 24/04/2024
  Deposit END date: 08/05/2024
  Thesis director: SIMÓ MARTORELL, RAFAEL
  Committee:
       PRESIDENT: RIBES LLORDES, MARTA
       SECRETARI: LINARES PRAT, CRISTINA
  Thesis abstract: Volatile organic compounds (VOCs) participate in ecologycal interactions and climate. In recent years it has been shown that coral reefs are producers of VOCs, but the entire collection of volatiles and the formation processes of many of these compounds within the reef remain to be described, as well as whether these processes are essentially biological (pelagic and benthic) or abiotic (driven by solar radiation and water temperature). To this aim, in this thesis we have studied the VOCs in the internal and external waters of the Mo'orea coral reef, in French Polynesia. This is a well-preserved reef, which is characterized by a virtual unidirectional flow of water and with strong currents, so that it allows to study the connection between the incoming waters, from the open ocean, and the inland waters, influenced by the components and processes of the reef.We have described the spatial and temporal variability of a series of VOCs with climate interest (COS, CS2, isoprene, iodometans (CH3I and CH2ClI), bromometans (CHBr3 and CH2BR2) and DMS), and non-volatile related compounds, such as dimethillefoniopropidated (DMSP), acrylate and dimethylphoxide (DMSO), within lagoon waters and nearby ocean waters. We also made comparisons with concurrent measurements of sea surface temperature, solar radiation, biogeochemical variables (nutrients, organic matter) and the taxonomic abundances and affiliations of the microbial microbial plankton in order to explain the interconnections between DMSP-derived compounds(DMSPC), VOCs and their environment through day/night cycles.The concentration of all the studied VOCs increased when water crossed the reef crest, with the bromomethans being the compounds that showed a greater increase. Incubation experiments with inner-reef waters around midday indicated that (a) photochemical reactions were the main source of COS and the main sink of DMS;(b) microbial plankton was the main source of DMS, isoprene and CH3I, and a major sink of COS;(c) algae were the main source of the polyhalomethanes CH2ClI, CHBr3 and CH2Br2; (d) carbonate sediments were a major source of CS2 and CH2ClI, DMS and isoprene, and the main COS loss. The dominant coral holobiont (Pocillopora sp.) was a source of only DMS and COS. Another studied coral (Acropora pulchra) was an important source of DMSPC, whose concentration near the polyps was parallel to the intensity of sunlight, with large increases during the day and decreases at night. This variation was probably generated by (i) the role of DMSPC as antioxidants for endosymbiotic Symbiodinoceae and for the coral itself, and (ii) the expulsion of endosymbionts under very high solar radiation intensities, as suggested by the molecular description of the microbial community. The identification and quantification of functional genes by metagenomics indicated that the bacteria near the A. pulchra colony were well prepared for the use and transformation of the DMSPC released by coral holobiont. Furthermore, the detailed study of the short-distance gradients of VOCs concentrations between the branches of A. pulchra illustrated the hydrographic complexity that occurs within a branched coral colony.In the deep, transparent and oligotrophic waters os the adjacent open ocean, VOCs were basically originated in planktonic activity but mainly regulated by light, with great importance of photochemical reactions that produced some compounds and destroyed others.In general, for a month, the reef was a net producer and net emitter of VOCs, compared to the open ocean. Using the most enriched VOCs in the reef, as well as nitrate and terrigenous dissolved organic matter, as tracers of reef waters that leave through the outflow channel, we estimated that 35% of the water that enters the reef across the crest is recirculated water of the same reef. This thesis advances our understanding about the production and cycling of VOCs in a tropical coral reef and its relationship with solar radiation.
  

DOCTORAL DEGREE IN MATERIALS SCIENCE AND ENGINEERING

• MARTIN SAINT-LAURENCE, PABLO: Constitutive modeling of ultrafine-grained refractory high-entropy alloys obtained by powder metallurgy
  
  Author: MARTIN SAINT-LAURENCE, PABLO
  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 MATERIALS SCIENCE AND ENGINEERING
  Department: (CEM)
  Mode: Normal
  Deposit date: 17/04/2024
  Deposit END date: 30/04/2024
  Thesis director: CABRERA MARRERO, JOSE MARIA
  Committee:
       PRESIDENT: TORRALBA CASTELLÓ, JOSE MANUEL
       SECRETARI: LLORCA ISERN, NURIA
       VOCAL: CARREÑO GOROSTIAGA, FERNANDO
  Thesis abstract: Refractory high-entropy alloys (RHEAs) prepared by mechanical alloying followed by spark plasma sintering usually outweigh the high-temperature mechanical behavior of as-cast counterpart alloys. Despite that, few studies have been conducted in order to understand their deformation mechanisms associated with these alloys and their particular microstructures (ultrafine grain size and considerable presence of secondary phases). The present work reports the synthesis, the microstructural characterization, and the constitutive modeling the AlCrxFeMoNbTiV2 (x = 0.15, 0.4, 0.8) RHEAs prepared by powder metallurgy, aiming to contribute to the comprehension of the deformation mechanisms behind the high-temperature mechanical behavior of RHEAs obtained with this fabrication route, as well as of the composition-microstructure-properties of RHEAs.In order to do so, the study was divided into three parts. In the first one, the effect of composition and milling time over themicrostructural and particle evolution of the powder was investigated. In the second part, the effect of Cr content and of a heat treatment over phase formation, microstructure, and grain size was investigated. In the third part, the samples were subjected to compression testing between 950 °C and 1100 °C and between 0.0005 s-1 and 0.01 s-1 to obtain the constitutive equations of the peak stress. Additionally, the microstructure of some of the deformed samples was characterized to find microstructural hints associated with the different potential softening and deformation mechanisms. During the milling study, it was observed that most of the changes occurred during the firsts 50 h, resulting in an average particle size of 7 µm and a nanostructured bcc+hcp microstructure. Except for Mo, none of the constituent elements considerably affected the microstructure or the particle size of the milled powders. The as-sintered samples, fabricated using powder milled for 50 h, successfully presented an ultrafine-grained and multiphase microstructure, constituted by a V,Mo-rich bcc matrix, accompanied by Fe,Nb-rich Laves phases, Al2O3 particles, and Ti,Nb-rich carbides. For reference, a hardness of 1124 HV0.3 was obtained in the as-sintered samples. The average grain size of the matrix phase decreased from 0.40 µm to 0.21 µm with further Cr content; however, the high-temperature mechanical properties were not affected. On the other hand, after the heat treatment, the average grain size increased up to 1.5 µm without affecting the phase equilibrium though. In opposition to the Cr content, the heat treatment enhanced the yield strength in a considerable manner: a specific yield strength of 98 MPa·g-1·cm3 at 1000 °C was obtained in these samples, three times that of the as-sintered sample. Regarding the constitutive modeling, the power law excellently fitted the experimental data, resulting in an exponent of 2.45, indicating that grain boundary sliding governed the high-temperature deformation of the studied alloy, just as it does in ultrafine-grained size traditional alloys. Additionally, an elevated activation energy of 527 kJ·mol-1 was obtained, associated either with a high softening resistance as well as with the considerable presence of secondary phases. In the case of the heat-treated samples, dislocation climbing and glide seemed to govern the deformation (at least at 1000 °C), explaining the enhanced strength, attributed to the hindered grain boundary mobility due to the larger grain size.
  

DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING

• CHEN, JIAN: EFFECTS OF CAVITATION ON THE WAKE CHARACTERISTICS BEHIND BLUNT TRAILING EDGE HYDROFOILS
  
  Author: CHEN, JIAN
  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 MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING
  Department: Department of Fluid Mechanics (MF)
  Mode: Normal
  Deposit date: 22/04/2024
  Deposit END date: 06/05/2024
  Thesis director: ESCALER PUIGORIOL, FRANCESC XAVIER
  Committee:
       PRESIDENT: HIDALGO DÍAZ, VICTOR HUGO
       SECRETARI: CASTILLA LOPEZ, ROBERTO
       VOCAL: ZHANG, DESHENG
  Thesis abstract: The recent developments in hydraulic machinery will increase the possibility of damage resulting from cavitation and/or vortex-induced vibrations. Yet, many researchers have shed light on the vortex street flow and the associated vortex-induced vibration in cavitating-free regimes, but less attention has been paid to the presence of cavitation. In the present study, the effects of cavitation on the vortex street flow behind a blunt trailing edge hydrofoil and its interaction with the vortex-induced vibration have been investigated. This will help to understand the mechanisms involved and to predict the dynamic of vortex-induced vibration with the presence of cavitation, allowing further control of this complex phenomenon in hydraulic machinery and systems.Thus, numerical solvers have been developed that are capable of accounting for the cavitating vortex street flow behind bluff bodies which have been validated and verified using some benchmark cases. Then, the effects of the fluid compressibility in the vortex street flow behind the wedge have been determined. Moreover, a series of numerical studies on cavitating vortex street flow behind a blunt trailing edge hydrofoil NACA 0009 have been conducted by predicting the boundary layer transition. As a result, the effects of cavitation on flow dynamics and its interaction with vortex-induced vibration have been examined.The impacts of fluid compressibility on the dynamics of the cavitating wake flow have been found to depend on the frequency range. At low frequencies, the effects of fluid compressibility are minimal and can be disregarded. On the other hand, fluid compressibility has been observed to amplify spectral energy at high frequencies. Interestingly, it has been found that almost identical numerical results with and without fluid compressibility are obtained in terms of predicted mean pressure profiles, dominant vortex shedding frequencies, and instantaneous and mean void fraction fields, which suggests that the compressibility effects on cavitating vortex shedding can be neglected. For the cavitating vortex street flow behind a blunt trailing edge hydrofoil NACA 0009, high-fidelity numerical simulations have been established in the current thesis. Based on the results, it has been observed that cavitation has a significant impact on the wake flow dynamics, notably increasing the shedding frequency of the primary vortices. Additionally, cavitation growth leads to increased hydrodynamic loads on the hydrofoil surface. Furthermore, cavitation development enhances the advected velocity of the vortices while decreasing the streamwise inter-vortex spacing. Both factors are believed to contribute to the increase of the vortex shedding frequency while the reduction of streamwise inter-vortex spacing tends to dominate this increase.The numerical results related to cavitating vortex street flow behind a blunt trailing edge hydrofoil NACA 0009 subjected to forced oscillation have shown that the induced dynamic response due to the oscillation is influenced by the presence of cavitation. In the lock-in regime, cavitation appears to widen the upper bound of this regime and cause a decrease in the added moment of inertia and an increase in the added damping. Moreover, the timing of the vortex shedding changes with the presence of cavitation. On the other hand, the oscillation of the hydrofoil affects the dynamics of cavitation in terms of cavitation inception and cavity length. Generally, the cavitation inception number gradually increases with the forced oscillation frequency. Meanwhile, approaching the bounds of the lock-in regime will cause local decreases in cavitation inception numbers. Besides, the length of the cavitating wake is influenced by the variation of the oscillation frequency, and the maximum cavitating wake length occurs under stationary conditions.
  

DOCTORAL DEGREE IN NETWORK ENGINEERING

• CEPEDA PACHECO, JUAN CARLOS: Contribution to the enhancement of IoT-based application development and optimization of underwater communications, by artificial intelligence, edge computing, and 5G networks and beyond, in smart cities/seas
  
  Author: CEPEDA PACHECO, JUAN CARLOS
  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 NETWORK ENGINEERING
  Department: Department of Network Engineering (ENTEL)
  Mode: Normal
  Deposit date: 22/04/2024
  Deposit END date: 06/05/2024
  Thesis director: DOMINGO ALADREN, MARIA DEL CARMEN
  Committee:
       PRESIDENT: LLORET MAURI, JAIME
       SECRETARI: REMONDO BUENO, DAVID
       VOCAL: HUERTA, MÓNICA KAREL
  Thesis abstract: 6G networks have emerged as a revolutionary breakthrough, promising ultra-fast and reliable connectivity that redefines the way we interact with the digital world. This new generation of networks not only drives communication between devices but is also the backbone of the Internet of Things. In addition, the learning and adaptive capabilities of Artificial Intelligence systems are driving process automation and efficiency. Similarly, Edge Computing complements this landscape by decentralizing data processing, bringing computing capacity closer to the sources of information. This allows for reducing latency and improving efficiency byprocessing data in real-time, driving critical applications that require instantaneous responses.This thesis focuses on two important points: 1) Improving the efficiency of applications in smart cities, and 2) Enhancing the efficiency of underwater communications in smart coastal cities by applying artificial intelligence, edge computing, and 5G and beyond. To achieve these objectives, an exhaustive study of the existing literature on 5G and beyond networks, smart cities, and artificial intelligence has been carried out. In addition, technical documentation to obtain an updated view of the different technologies that enable the development of applications based on 5G and beyond has been analyzed. Aiming to generate newand innovative alternatives in the field of tourism, security, improved underwater communications, and marine discovery that drive promote development to meet the needs of citizens in smart cities and ocean/sea. As a result of this study, the first contribution has emerged. It involves the analysis, design, and implementation of a tourist attraction recommendation system employing a deep learning algorithm tailored for smart cities. The primary objective is to improve how tourist attraction recommendations are made so that they are tailored to the requirements of each visitor in a given city and thereby reduce the time it may take a visitor to search for possible places to visit.The second contribution arises in surveillance and security, which consists of a distraction detection system for the prevention of drowning in aquatic places, developed in a 5G and beyond network environment. For this goal, an approach of surveillance cameras capturing images of people in charge of minors in swimming pools or beaches was proposed; and employing an ML algorithm (convolutional neural networks) to classify the type of distraction that a person in charge of a minor may have.Finally, the third contribution is presented, called reinforcement learning and mobile edge computing for 6G-based underwater wireless networks. In this approach, a submerged edge mobile computing architecture is presented in which an AUV is used as a mobile platform (MEC), in addition, several local AUVs equipped with computational resources that collect tasks from sensor nodes and can make the decision to process them locally or partially or fully offload them to the mobile edge computing AUV device. To this end, an algorithm based on deep reinforcement learning (DDPG) is proposed for trajectory control, task offloadingstrategy, and computational resource allocation, combined with mobile edge computing and AUVs to improve underwater communication; aiming to minimize the sum of maximum processing delays and energy consumption during the whole process of executing a task.The contributions presented in this doctoral thesis are of singular importance, since to date they continue to be innovative. The contributions presented not only represent significant advances in their respective areas but also lay the groundwork for future research and developments in smart city construction and underwater communications optimization, thereby reinforcing the transformative potential of artificial intelligence, edge computing, and advanced wireless networks in these domains.
  
• HAASTRUP, ADEBANJO: Enhanced Dynamic Bandwidth Algorithms for Passive Optical Networks
  
  Author: HAASTRUP, ADEBANJO
  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 NETWORK ENGINEERING
  Department: Department of Network Engineering (ENTEL)
  Mode: Normal
  Deposit date: 22/04/2024
  Deposit END date: 06/05/2024
  Thesis director: RINCON RIVERA, DAVID | PINEY DA SILVA, JOSE RAMON
  Committee:
       PRESIDENT: KHALILI, HAMZEH
       SECRETARI: SPADARO, SALVATORE
       VOCAL: PAPAGIANNI, CHRYSA
  Thesis abstract: The telecommunications industry faces rapid changes due to the deployment of ultra-high speed access networks (5G and beyond, fiber-to-the-home), promising unparalleled experiences with high bandwidth and low latency. However, this transition brings challenges. With the surge in smart device numbers and bandwidth demand, optimizing network architecture, management, and resource usage is crucial for cost-efficiency. Passive Optical Networks (PONs) offer efficient broadband access for residential and commercial sectors, with advantages like energy efficiency and robust security and high performance. Leading organizations, such as IEEE and ITU-T, are actively developing standards to increase the capabilities of next-generation PONs. The goal is to meet the demands by implementing innovative mechanisms for efficient management, resource allocation, QoS, energy savings, and low latency.Next-generation PONs have introduced the use of multiple wavelengths based on TWDM techniques. However, managing multiple wavelengths presents challenges, as DBA algorithms need to consider both the time and wavelength dimensions of the network. This follows a Joint Time and Wavelength Scheduling (JTWS) scheme, which requires complex implementation. TWDM-PON also utilizes tunable transceivers in ONUs to switch between wavelengths, but this introduces a delay called Laser Tuning Time (LTT) which is often ignored, but it is an important consideration when designing our DBA algorithms. Additionally, there is a demand to integrate metro and access networks for streamlined telecom infrastructure. Long Reach PON (LRPON) offers a solution by expanding coverage from 20 km to 100 km, enabling high-speed, long-distance data transmission over optical fibers. This reduces the need for central offices, resulting in cost savings. However, the extended reach of LRPONs introduces new challenges, particularly in the area of DBA algorithms. Traditional DBA algorithms like IPACT may not be as efficient for LRPONs due to increased propagation delays and round-trip times (RTT) between the OLT and ONUs. To address these challenges, a novel DBA algorithm called the Distance Weighted DBA (DWDBA) algorithm is proposed.This thesis delves into the limitations of traditional DBA algorithms and proposes novel Enhanced DBA solutions for PONs. Leveraging techniques such as the Longest Processing Time (LPT) scheduling method to minimize queue delays, our DBAs also consider the concept of laser tuning time to bring a practical, real-world approach to our system. The main contributions of this thesis are: - Incorporating the often-overlooked laser tuning time (LTT) concept in our analysis of DBA for TWDM PONs, therefore obtaining more realistic results. - Introducing an innovative algorithm for PONs employing LPT to minimize queue delay and enhance throughput, resulting in a notable reduction (up to 73%) with respect to the queue delay when compared to IPACT. - Developing a Distance Weighted DBA (DWDBA), specifically tailored for LRPONs, aimed at preventing the penalization of ONUs located farther from the OLT. This results in improving up to 30% and 10% the queue delay and throughput, respectively, over IPACT.The effectiveness of these proposed algorithms is rigorously evaluated through comprehensive simulations, demonstrating their potential to meet the demands of future networks.
  

DOCTORAL DEGREE IN OPTICAL ENGINEERING

• BALLESTA GARCIA, MARIA: Propagation of polarized light through turbid media: Application of lidar technology in foggy environments
  
  Author: BALLESTA GARCIA, MARIA
  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 OPTICAL ENGINEERING
  Department: Department of Optics and Optometry (OO)
  Mode: Normal
  Deposit date: 22/04/2024
  Deposit END date: 06/05/2024
  Thesis director: ROYO ROYO, SANTIAGO
  Committee:
       PRESIDENT: ARTEAGA BARRIEL, ORIOL
       SECRETARI: VILASECA RICART, MERITXELL
       VOCAL: BIJELIC, MARIO
  Thesis abstract: In recent times, there has been a growing interest in LiDAR imaging systems for outdoor applications involving computer vision, such as automotive systems, surveillance, and robotics. LiDAR sensors have the ability to capture 3D data, that is, the geometry (volume, distances) of the scenes involved, complementing the 2D projections of scenes available in conventional cameras. However, their limited tolerance to adverse weather conditions, particularly fog, stays as one of the obstacles that hinders their complete settlement. This Thesis aims to evaluate the potential of utilizing the polarization properties of light and the digitization of the signal to improve the system¿s imaging capabilities in such challenging conditions. Additionally, our research offers valuable insights in the domain of imaging through fog. Understanding the interaction of polarized light with turbid media and recognizing the importance of the targets¿ polarimetric properties within the imaged scene is essential for optimizing the performance of polarimetric imaging systems.To achieve our goal, a preliminary investigation to examine the characteristics of polarimetric imaging through fog is undertaken. Our findings indicate that polarimetric imaging modes provide higher contrast compared to intensity-based imaging modes, facilitating the identification and segmentation of different targets. Additionally, experimental characterization of the depolarizing behavior of light through fog is conducted for both reflection and transmission imaging modes. The results suggest that, in this scenario, light behavior falls within the scattering regime of the polarization memory effect, with a significantly reduced depolarization in circularly polarized beams when compared to linearly polarized ones. To the best of our knowledge, this Thesis quantifies for the first time the differences between the performance of both polarization modes in fog conditions. Next, a Monte Carlo-based model is developed to meet the requirements of our LiDAR prototype. Considering the resource-intensive nature of experiments conducted in fog conditions and the dynamic nature of fog, the model¿s ability to accurately simulate the physics of the problem, including a realistic fog environment, helps to guide the definition of the future experimental actions. Subsequently, the model is utilized to simulate and analyze various aspects relevant to the design of the system, including polarization configurations, interactions with targets, and irregularities in the media (in practice, generalizing the scattering media beyond fog to e.g. sand or smog), together with the characteristics of the acquired signal. Finally, this Thesis presents a novel polarized LiDAR imager prototype and evaluates its performance in fog conditions. It conclusively shows that using circularly polarized light and a cross-configuration detection setup significantly improves system performance in such scenarios. This system effectively tackles challenges induced by scattered light, reducing saturation effects from backscattering, mitigating scattering noise in point clouds, and enhancing target detection, especially for highly reflective surfaces like metallic targets. This approach offers an innovative, straightforward, and efficient method for signal stabilization and enhancement of the point cloud quality by relying on the inherent physics of the problem.
  

DOCTORAL DEGREE IN STRUCTURAL ANALYSIS

• AGUIRRE RUZ, ALEJANDRO: Numerical approximation of thin structures using stabilized mixed formulations for Infinitesimal and Finite Strain theories, including Fluid-Structure Interaction problem applications.
  
  Author: AGUIRRE RUZ, ALEJANDRO
  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 STRUCTURAL ANALYSIS
  Department: (DECA)
  Mode: Normal
  Deposit date: 22/04/2024
  Deposit END date: 06/05/2024
  Thesis director: CODINA ROVIRA, RAMON | BAIGES AZNAR, JOAN
  Committee:
       PRESIDENT: ROMERO OLLEROS, IGNACIO
       SECRETARI: ROSSI BERNECOLI, RICCARDO
       VOCAL NO PRESENCIAL: COLOMÉS GENÉ, JOSEP ORIOL
  Thesis abstract: The theories of thin structures can be classified into two main branches depending upon whether shear deformation in the transverse direction is taken into consideration or not. In this context, theories accounting for shear deformations prove suitable for modeling structures with both thin and thick profiles. In the Finite Element context, they are referred to as C0 theories due to the minimum continuity order of shape functions required to pose a discretized approximation. However, there are space incompatibilities in the standard discrete approximation that exhibits spurious solutions, particularly evident in thin structures. These instabilities, known as numerical locking, result in an artificial stiffening of the structure, whose effect becomes more pronounced for thinner structures. Various forms of numerical locking can be triggered, influenced not only by the slenderness of the structure but also by its shape and the nature of the applied loads. In this context, flat structures are prone to shear locking when exposed to transverse loads. Conversely, curved structures may confront different mechanisms leading to various forms of numerical locking, namely membrane, thickness, and trapezoidal locking. The initial part of the study aims to develop a specialized framework to address instabilities in the context of flat structures in the context of Reissner-Mindlin theory. Subsequently, the second part of the study aims to expand the framework to effectively address instabilities arising in of curved structures in the context of Solid-Shell elements. The locking problem is approached by means of a mixed formulation that considers displacements and stress as unknowns in a curvilinear coordinate framework. This approach allows to isolate the components of the stress tensor in order to study the mechanisms in which every type of numerical locking are triggered. The third part of the thesis is dedicated to integrating the previous advancements into Finite Strain analysis by the inclusion of standard hyperelastic constitutive behavior. With this approach, the problem becomes even more difficult to solve because of the non-linearity and the large deformations the shell is subject to. Lastly, the fourth and final part is dedicated to addressing the Fluid-Structure Interaction problem using an embedded mesh approach, which has consistently been a topic of great research interest in the literature, because of its complexity and wide variety of applications. This problem introduces a variety of challenges that have to be properly addressed: the discontinuous pressure field arising for the structure separating the fluid domain, the computation and imposition of transmission conditions between domains, the coupling strategy, and the algorithmic work needed to join all of these ingredients together. This thesis mainly focuses on overcoming challenges associated with thin structures when employing the conventional Galerkin Finite Element approach. It seeks solutions through stabilized methods, specifically within the Variational Multiscale framework. As result, the formulations developed through the investigations have proven to be robust, allowing to model locking-free thin structures efficiently, and to accurately describe the physics of thin shells immersed in fluid flows and being subject to large deformations.
  

DOCTORAL DEGREE IN SUSTAINABILITY

• ORNELAS HERRERA, SELENE IVETTE: PREFERENCIAS DE LOS CONSUMIDORES Y AGRICULTORES HACIA UN SISTEMA AGROALIMENTARIO MÁS SOSTENIBLE
  
  Author: ORNELAS HERRERA, SELENE IVETTE
  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 SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Normal
  Deposit date: 17/04/2024
  Deposit END date: 30/04/2024
  Thesis director: KALLAS CALOT, ZEIN
  Committee:
       PRESIDENT: SÁNCHEZ GARCÍA, M. MERCEDES
       SECRETARI: RAHMANI MEDDOUR, DJAMEL
       VOCAL: IGLESIAS MARTÍNEZ, EVA
  Thesis abstract: The adaptation of the agri-food system towards more sustainable models is a pressing need to guarantee food security for current and future generations, in the face of population growth, scarce natural resources and climate change. To meet the challenges of producing more sustainably, new food production systems have been developed, they incorporate the principles of circular economy. Circular production systems reduce the consumption of new external inputs and the generation of waste, reducing adverse environmental effects and allowing the recovery of nutrients. This thesis addresses two of the main links in the shortest value chain of the agri-food system, "the producer and the consumer", and their response towards the incorporation of sustainability approaches, such as circularity. The objective is to analyze whether the circular agriculture practices identified as more sustainable are accepted by agricultural producers and the factors that influence their adoption, as well as the preference of consumers and their willingness to pay for these circular production innovations, in order to try to convert the results obtained into evidence that can serve as a basis for generating adequate and coherent public policies, to support and facilitate the adoption of circular innovations. . In relation to the above, in the first instance a semi-structured questionnaire was applied to agricultural producers from: Spain, Austria, Czech Republic and Italy, in which the hierarchical analysis method (AHP) to measure preferences and the scale of the New Ecological Paradigm NEP were included to measure environmental attitudes. Results showed an adoption readiness of 48.24% and that the acceptance of the proposed circular innovations is closely related to the environmental objectives, level of education, previous adoption experience and environmental attitudes of farmers. We also found that institutional support plays an important role in adoption decisions. With regard to consumers, in a first approach, through a survey of 5,246 consumers in Germany, the Netherlands, Italy, the Czech Republic and Spain, their willingness to pay for beef fillet produced in a circular livestock system was analyzed, using the Discrete Choice Experiments (DCE) method. This study included the analysis of the behaviors that influence their preferences, based on the Theory of Planned Behavior (TPB). The results allowed us to observe that there is a potential market for circular beef fillet. Although preferences are heterogeneous, consumers are generally willing to pay a higher premium for circular beef steak than conventional steak and lower than for organic beef. Of the components of planned behavior theory, social norms and behavioral control perception increased preferences for circular production beef steak, while environmental attitudes increased preferences for organic beef steak, and reduced preference for conventional beef steak. Subsequently, the preferences of 5,591 consumers in Spain, Poland, Italy, Hungary, Croatia and Belgium were analyzed, as well as their willingness to pay for pork, milk and bread labelled as circular and presented as more sustainable, in terms of reducing greenhouse gas emissions and optimizing nutrients. This analysis included sustainable consumption behavior, focused on purchasing, use, and recycling habits. The results showed that about 27% of participating consumers preferred foods from circular systems. As in the previous study, the results highlighted the importance of consumers' environmental attitudes in determining their preferences for environmentally sustainable products. All of the above results on consumers allow us to suggest to governments, policy makers and other sectors involved in sustainable food production, the standardization of food labels obtained through circular agriculture systems and the design of educational programs to increase knowledge about the problems generated by unsustainable consumption habits.
  
• PAZMIÑO FLORES, YADIRA CARMEN: Evaluación de los usos de suelo y valor ecosistémico del páramo de la Subcuenca Chambo (Ecuador)
  
  Author: PAZMIÑO FLORES, YADIRA CARMEN
  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 SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Article-based thesis
  Deposit date: 17/04/2024
  Deposit END date: 30/04/2024
  Thesis director: FELIPE BLANCH, JOSE JUAN DE | VALLBE MUMBRU, MARC
  Committee:
       PRESIDENT: AGUILERA BENAVENTE, FRANCISCO
       SECRETARI: ALCARAZ SENDRA, OLGA
       VOCAL: GUAITA PRADAS, INMACULADA
       VOCAL NO PRESENCIAL: HERNÁNDEZ CLEMENTE, ROCÍO
       VOCAL NO PRESENCIAL: GILABERT NAVARRO, M. DESAMPARADOS
  Thesis abstract: The scarcity of information that allows understanding the importance of natural resources from an economic approach is a limitation to establish parameters related to environmental investment in conservation plans. This research proposes a methodology that allows modeling the variability of páramo land uses and the Ecosystem Valuation (EV) of the Chambo-Ecuador sub-basin from a bioeconomic monitoring that links the economic rent of páramo land uses with remote sensing tools and geographic information systems. The main results of the methodology determined that temporal monitoring of land covers is essential to identify areas of greatest vulnerability to EV degradation. The thresholds, functions and interrelationships determined in the Cart Decision Tree (CDT), Multilayer Perception (MLP), Multivariate Adaptive Regression Splines (MARS) and Support Vector Machines (SVM) models for land cover recognition were efficient; the models performed 88%, 85%, 83% and 81% respectively. The hybridization of the models, Markov chains and cellular automata was appropriate for predicting future land cover changes in Andean areas in relation to their VE, the methods achieved acceptable accuracy for recognizing páramo land uses. The variables chosen for land cover classification were adequate to identify land cover particularities.The opportunity cost and benefit transfer methods proposed obtained a good performance in the evaluation of food production trajectories linked to environmental services (ES) of carbon supply and concentration associated with indirect and support ES, so it was determined that the information from the dynamics of environmental services is an important indicator to understand the real state of the resource and consequently allows understanding the necessary strategies to undertake sustainable actions for ecological management.The mapping generated allowed us to determine that the páramo decreased by 13% between 2000-2010 and 19% between 2010-2020. It was estimated that the loss of the ecosystem between 2000 and 2030 will increase to 28%. From the first year of the study to the last year considered in the work, the páramo will go from occupying 92% to 64% of the area studied. The changes in the EV reveal that the categories with anthropogenic activity analyzed maintain a constant growth that has a direct impact on the EV of the páramo. The most affected areas are those up to 3500 meters above sea level. The EV of the Chambo sub-basin from 2000 to 2020 will increase from 2.86×108 USD to 2.59×108 USD and it is estimated that by 2030 the EV will decrease to 2.48×108 USD, which leads us to recognize that, although the loss of the EV of the natural resource is not critical, its degradation is increasing.Through this methodology it will be possible to obtain, in a practical way, data on the conservation status of the resource over time, allowing to solve problems related to the scarcity of data and leading to the understanding of changes in the area from a socioecological approach, i.e., covering the environmental impacts of human activities on natural systems. The basis of the developed method allows replication of the methodology.The information generated by this study will be of vital importance to understand the causes of the changes in the Andean systems in monetary and environmental terms, which will allow the development of management plans and conservation policies aimed at protection and sustainable management from an economic approach.
  
• RAMIREZ GARRIDO, ROSEMBER: Evaluación del Riesgo Ambiental de las Nanopartículas de Plata (AgNPs) en Ecosistemas Acuáticos
  
  Author: RAMIREZ GARRIDO, ROSEMBER
  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 SUSTAINABILITY
  Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
  Mode: Normal
  Deposit date: 18/04/2024
  Deposit END date: 02/05/2024
  Thesis director: DARBRA ROMAN, ROSA MARIA | MARTI GREGORIO, VICENÇ
  Committee:
       PRESIDENT: DE PABLO RIBAS, JOAN
       VOCAL: DÍAZ CRUZ, SILVIA
  Thesis abstract: The widespread and increasing use of silver nanoparticles (AgNPs) in various products is leading to their release into different environmental compartments, especially into aquatic environments. These particles can enter these environments through various pathways, for example, gradually via effluents from wastewater treatment plants (WWTPs) or accidentally through spills onto soil or into rivers. This thesis presents a detailed analysis of the transport (advection-dispersion) and dispersion of silver nanoparticles (AgNPs) in both surface and groundwater, considering mass balances, various mathematical models, and factors influencing their mobility and retardation. For surface waters, continuous and point discharges are considered, and an analytical model is used to represent the behavior of AgNPs in the river. For groundwater, point discharges are considered. The interaction of AgNPs with porous media in groundwater (retardation process) is also taken into account, which allows for the calculation of the maximum concentration of AgNPs in groundwater. Initially, a Fuzzy Logic model is developed to assess the environmental risk in aquatic ecosystems based on the concentration and toxicity of AgNPs. The toxicity is determined with great adaptability by including variables such as shape, size, and coating of the nanoparticles, allowing a more accurate risk assessment. This model is applied to a discharge of AgNPs into the river from WWTP effluents or an accident. The results show that in all cases, the risk of AgNPs due to direct accidental discharge into the river poses a higher risk than that from WWTPs. Subsequently, a hybrid model is developed that integrates Monte Carlo simulation (for concentration calculation) with the developed Fuzzy Logic model. This integration provides a tool for assessing the environmental risk of AgNPs due to a spill onto the soil. Two scenarios are proposed after the spill: discharge of AgNP-contaminated aquifer water into the river and use of this aquifer water for wetland recharge. The concentration distribution of AgNPs by river discharge is below the proposed legal limit, while in the wetland use scenario, legal limits are not met in any case, indicating a higher risk associated with this latter use. After conducting a sensitivity analysis, it has been proved that the developed Hybrid model, which combines Fuzzy Logic and Monte Carlo techniques, is a useful and versatile tool for managing uncertainty in risk assessment.
  

DOCTORAL DEGREE IN URBANISM

• KARAMANEA, PANAGIOTA: Diachronic terrains: Three landscape narrations on the west Attic coast
  
  Author: KARAMANEA, PANAGIOTA
  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 URBANISM
  Department: (DUTP)
  Mode: Normal
  Deposit date: 23/04/2024
  Deposit END date: 07/05/2024
  Thesis director: SABATE BEL, JOAQUIN | GOULA, MARIA
  Committee:
       PRESIDENT: SARDÀ FERRAN, JORDI
       SECRETARI: SPANOU, IOANNA
       VOCAL: MORAITIS, KONSSTANTINOS
  Thesis abstract: The thesis researched for a hybrid interdisciplinary system of tools that could help decode coastal landscapes. The west Attic shoreline, a space of contrasts and surprises, stands as a forgotten landscape awaiting rediscovery. Amidst the interplay of urbanity and landscape Attica, unfolds dynamic perspectives as a cultural ecotone. Until now, a comprehensive cartographic study of the western Attic coast, has been absent. The research delves into the cultural formation of perspectives on the coast, examining how both foreign and local intellectuals have shaped these views over time. It investigates the Grand Tour and its contemporary interpretations, the 1930¿s, seeking to understand their influence on the collective imagination regarding Attica. It provides a synthesized overview of the historical aspect, spanning from antiquity to the touristic evolution of today. The research navigated through toponymy and landscape, historical archives and old maps focusing especially on the west Attic coastal terrain. The research also endeavors to adopt the lens of the seventh art, cinema. The research explores the sensorial gaze Attica and the local cinema 1950¿s selection of coastal shots. From a cultural and sensory standpoint, cinema offers a unique lens through which the coast is perceived. It allows to explore the emotional and experiential aspects of coastal life, capturing the essence of the seaside environment. Cinema, with its storytelling capabilities can help us connect with the coast on a personal and emotional level. By dissecting films where the landscape takes on a protagonist role, the research shifts its focus to cinema as a tool for articulating the intricacies of the coastal environment ¿ a novel and imaginative approach to apprehending its essence. In this context, cinema is not merely regarded as a narrative artistic form; rather, it emerges as a potent medium for both representation and comprehension. Finally, the thesis delves into an exploration of the landscape through original mapping and cartography, aiming to uncover dynamics and qualitative attributes. The overarching goal is to dissect the coastal expanse, unravelling its configuration, fundamental traits, and prominent landscape elements. Through cartography, an effort is made to discern the intricate relationships between various entities, navigating scales and offering an interpretive lens grounded in landscape perspective. On the other hand, the morphological and cartographical approach involves an examination of the physical characteristics and spatial layout of the coast. This includes the topography, land use patterns, and geographical features that shape the coastal region. By delving into these aspects, a deeper understanding of how the coast functions is gained and how it can be harnessed for various purposes, from urban landscape planning to environmental conservation. The spatial configuration of the ground, the surface as infrastructure in the sense of landscape armature and ecological aspects seen as a systemic network, could help integrate the natural landscape in the discussion of rejuvenating the city in a resilient way. Landscape architecture as an interface between city and nature is proposing interdisciplinary processes to apply.