Doctoral School

Reading date: 08/07/2025

• GONZALEZ SUBIABRE, REINALDO GUIDO MOISES: Impact of Mixing-Driven Precipitation and Sharp Soil Interfaces on Solute Transport: From laboratory visualization to numerical modeling
  
  Author: GONZALEZ SUBIABRE, REINALDO GUIDO MOISES
  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: Barcelona School of Civil Engineering (ETSECCPB)
  Mode: Normal
  Deposit date: 10/06/2025
  Reading date: 08/07/2025
  Reading time: 11:00
  Reading place: UPC Campus NordETSECCPBC/ Jordi Girona 1-3Edificio C1, Sala 002Barcelona
  Thesis director: FERNANDEZ GARCIA, DANIEL
  Thesis abstract: Understanding the dynamics of solute transport in highly heterogeneous porous systems represents an inherent challenge for assessing various subsurface activities, such as carbon sequestration and groundwater remediation. This difficulty arises from the inability to directly observe the processes occurring in the subsurface. To improve the understanding of the impact of heterogeneity on solute transport, it is crucial to visualize and evaluate these processes in well-controlled experimental settings. The objective of this thesis is to enhance the current understanding of the impact of heterogeneity on solute transport dynamics through laboratory experiments and numerical modeling. The work offers new experimental insights into solute transport, mixing, and chemical reactions in highly heterogeneous porous media, with a particular focus on the role of mineral precipitation and sharp soil interfaces in transport dynamics, aiming to enhance the conceptual and numerical understanding of these complex processes. The first part of the thesis investigates the impact of Mixing-Driven Calcite Precipitation (MDP) on solute transport. Laboratory experiments were conducted in an intermediate-scale Hele-Shaw cell, simulating a coarse-sand porous medium to observe the spatiotemporal evolution of calcite precipitation under mixing conditions. Self-organized heterogeneities in the precipitate structure were observed, with calcite layers forming symmetric patterns aligned with the main flow, contrasting with the asymmetry predicted by a semi-analytical model under idealized conditions. Tracer tests conducted before and after precipitation demonstrated significant impacts on solute transport, including the emergence of strong anomalous transport features, such as earlier solute arrival, a distinct double peak, and pronounced tailing. The thesis continues with a chapter that evaluates how self-organized heterogeneous porous media, induced by mineral precipitation, should be characterized in a solute transport model to effectively reproduce the resulting non-Fickian transport behavior. To achieve this, we analyze the spatial variability of hydraulic conductivity by implementing different permeability scenarios in a random walk particle tracking model. Our results highlight the importance of capturing two key features to effectively describe solute transport. First, delineating the total precipitated area is crucial for accurately representing flow diversion caused by permeability reduction, which explains the emergence of the double peak in solute concentrations. However, fully capturing both the double peak transition and tailing requires representing the internal structure of the high-precipitation zones within the precipitated area, as these characterize internal preferential flow channels. The thesis concludes with an experimental work that investigates the impact of sharp interfaces in reactive and conservative solute transport. Experiments were conducted in an intermediate-scale horizontal tank to visualize and evaluate the spatiotemporal evolution of solutes plumes. The results show that the reaction product encounters anomalous resistance when crossing the interface between coarse and fine materials. This effect is less pronounced during the fine-to-coarse (FC) transition. An unexpected enhancement of the transverse spread of the reaction product is observed in the coarse-to-fine (CF) transition, accompanied by a slower release within the fine material. A sudden decrease in the longitudinal resident concentration is detected across the heterogeneity interface. Mixing metrics reveal that, as the apparent transverse dispersivity increases near the interface during the CF transition, both the scalar dissipation rate and the total mass reacted also rise, indicating greater solute reactivity compared to the FC configuration.
  

• MARTÍNEZ MOLINA, IGNACIO: Los edificios residenciales urbanos de José Antonio Coderch, 1964-1969. Las plantas bajas como construcción de espacio público.
  
  Author: MARTÍNEZ MOLINA, IGNACIO
  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 ARCHITECTURAL DESIGN
  Department: Department of Architectural Design (PA)
  Mode: Normal
  Deposit date: 03/06/2025
  Reading date: 08/07/2025
  Reading time: 11:30
  Reading place: ETSAB (Escuela Técnica Superior de Arquitectura de Barcelona) - Planta Baja - Sala de Grados - Av. Diagonal, 649-651 - 08028 - Barcelona
  Thesis director: GARCIA ESCUDERO, DANIEL | BARDÍ MILÀ, BERTA
  Thesis abstract: This research analyzes urban residential buildings designed by J.A. Coderch between 1964 and 1969, specifically exploring his relationship with the city. The study uses ground floors as an analytical tool, understood as the ground plane - a crucial intersection point between building and urban environment.Coderch's professional career spanned approximately from 1940 until his death in 1984. During this time, he constructed 12 urban buildings, mostly in Barcelona, plus other unrealized projects.The study period begins in 1964 with the commission for the Girasol building. In the following three years, he developed almost simultaneously three emblematic works: the Girasol building (1964-1967), the Trade Towers (1965-1969), and the Banco Urquijo housing complex (1967-1971), which won the FAD Prize in 1972. These projects enabled him to access the commission for the Sarriá Garages housing complex (1968-1975). During this period, he also completed other relevant projects such as the competition for Banco Sabadell, the Roviralta Foundation building, and the Monitor building.In just five years, a significant evolution is observed in the scale and complexity of his urban projects, advancing from small semi-public interventions to large projects incorporating extensive pedestrian public areas. This progression allowed him to develop both typological and urban research and evolution.Although the characteristic fragmentation of volumes and facades in his work can sometimes complicate understanding his urban proposal, an analysis free from formal judgments reveals that his projects, far from isolating themselves from the city, express a clear intention of urban integration and continuity, enriching the environments where they are inserted.This intention materializes through four conceptual strategies present in all his projects:1. Permeability: His designs favor access and interaction with the surroundings through eliminating enclosures, creating covered porches and passages, and incorporating permeable base levels.2. Parcel cession as public space: By setting back buildings from plot boundaries, the generated free spaces are conceived as extensions of public space.3. Creation of public gardens and green areas: A key element adopting three main forms: public gardens integrated into private projects, garden streets, and garden levels.4. Vertical articulation of the ground floor: The ground plane acquires a dynamic and complex configuration in its section.Although Coderch has often been considered an anti-urban architect, supposedly disinterested in the city, this study demonstrates the contrary. His rejection was not directed at the city itself, but at the dichotomy imposed by two predominant 20th-century urban models: the traditional model (street alignment, closed blocks, ventilation courtyards) and modern urbanism (functionality, isolated high-rise buildings, urban discontinuity). Faced with these limitations, Coderch developed hybrid alternatives transcending this classification.This work maintains that his proposals retain their validity in contemporary debates on architecture and city. Following Professor Manuel de Solà-Morales, who affirmed that building a city involves generating civic, collective, and common spaces through architectural design, we can consider J.A. Coderch a profoundly urban architect, committed to an architecture that dialogues with the city and enhances public space quality.
  

Reading date: 09/07/2025

• KHARE, PRASUNIKA: Simulation and Modeling of C+L+S Multiband Optical Transmission for the OCATA Time Domain Digital Twin
  
  Author: KHARE, PRASUNIKA
  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: Department of Computer Architecture (DAC)
  Mode: Normal
  Deposit date: 19/05/2025
  Reading date: 09/07/2025
  Reading time: 10:00
  Reading place: Sala C6-220
  Thesis director: VELASCO ESTEBAN, LUIS DOMINGO | SIMOES DA COSTA, NELSON MANUEL
  Thesis abstract: This thesis focuses on implementing more robust control and management strategies such as those based on machine learning to enhance intelligence and drive towards autonomous operation is crucial for the future of optical communications. In this regard, this thesis aims at three specific objectives: The first objective is to develop a multiband optical transmission simulator. It can be challenging to conduct simulations on a fully loaded MB system with hundreds of channels. In addition, in MB optical transmission, the Inter-channel Stimulated Raman Scattering (ISRS) becomes a major effect, which adds more complexity. In view of that, the Fourth Order Runge-Kutta in Interaction Picture (RK4IP) method is evaluated as an alternative to reduce time complexity, which is complemented with an adaptive step size algorithm to further reduce the computation time. We show that RK4IP provides an accuracy comparable to that of SSFM with reduced computation time, which enables its application for MB optical transmission simulation. The second objective focuses on developing models for C+L+S Multiband Optical Transmission System In this objective of this thesis, we focus on modelling MB optical transmission to provided fast and accurate QoT estimation and propose Machine Learning (ML) approaches based on neural networks, which can be easily integrated into an Optical Layer Digital Twin (DT) solution. We start by considering approaches that can be used for accurate signal propagation modelling. Even though solutions like the Splitstep Fourier method (SSFM) for solving the non-linear Schrödinger equation (NLSE) cannot be used for QoT estimation due to their very high time complexity. Therefore, ML modelling approaches are considered to be integrated in the OCATA DT, where models predict optical signal propagation in the time domain. Being able to predict the optical signal in the time domain, as it will be received after propagation, opens opportunities for automating network operation, including connection provisioning and failure management. The third objective of this thesis is to develop a semi-analytical model for measuring the gain profile of amplifiers in both fully loaded and partially loaded conditions of the metro- access network. The power imbalance is one of the issues associated with transitioning to a metro-access merged network. Additionally, maintaining these two separate networks (metro and access) is both complicated and costly. The node that interconnects the two networks must perform O-E-O conversions on the data traversing between them. The current network system uses ROADM in nodes, which is all optical and requires no O-E-O conversion. Therefore, this goal primarily focuses on characterizing the parameters of EDFA present in reconfigurable optical add-drop multiplexers (ROADMs) with the aim of achieving a balance between flexibility, complexity, and cost. These nodes must be thoroughly characterized regarding optical losses, power consumption, and other metrics. Once evaluated, the performance of these nodes can be modelled to enable the SDN controller to incorporate them into the network.
  

• RIDOLFO, SHARON: Ultrafine particles characterization from different transport sources
  
  Author: RIDOLFO, SHARON
  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 NATURAL RESOURCES AND THE ENVIRONMENT
  Department: Department of Mining, Industrial and ICT Engineering (EMIT)
  Mode: Article-based thesis
  Deposit date: 29/05/2025
  Reading date: 09/07/2025
  Reading time: 11:00
  Reading place: Sala B3 MultimèdiaEscola Tècnica Superior d'Enginyeria de Telecomunicació de Barcelona
  Thesis director: AMATO, FULVIO | QUEROL CARCELLER, XAVIER
  Thesis abstract: Ultrafine particles (UFP), defined as airborne particulates with an aerodynamic diameter smaller than 100 nm, are of particular concern due to their ability to penetrate deep into the respiratory system and even reach the brain directly via the olfactory bulb, with potential to cause a wide range of adverse health effects. In response to the growing evidence of health risks associated with UFP, the World Health Organization (WHO) has recently issued ‘Good practice statements’ emphasizing the need of integrating UFP in terms of particle number concentration (PNC) into existing air quality monitoring systems (WHO, 2021). In line with these recommendations, the new European Air Quality Directive (AQD, 2024/2881/EC) requires the monitoring of PNC and particle number size distribution (PNSD) in urban, and of PNC in rural supersites and pollution hotspots, including traffic, harbors, airports, and industry, among others (EU, 2024). In this context, the present PhD thesis investigates the concentrations, size (and some chemicals) patterns and source contributions of UFP in transport environments, including a review of existing literature on PNC-PNSD, as well as experimental studies conducted at an airport, harbor, road traffic and urban background (UB) in Barcelona (NE Spain) and a subway in Valencia (E Spain). The review aimed to assess the instruments used, analyze results, and identify knowledge gaps in PNC-PNSD across transport environments. It highlighted under-studied areas needing further investigation and provided key insights for the field campaigns. The findings identified road traffic as the main contributor to PNC in urban areas, with commuting modes influenced by proximity to traffic and meteorological conditions. It also emphasized the need for harmonizing measurement protocols due to significant variations in methods, particularly in lower (finer) particle size detection limits.The experimental studies revealed substantial variability in PNC and PNSD, driven by differences in emission sources and site-specific conditions. The airport recorded the highest PNC, dominated by aircraft activity, particularly taxiing and takeoff, while the subway exhibited the lowest. Nucleation mode particles (<25 nm) were especially elevated at the airport and road traffic site, indicating the influence of fresh emissions and secondary formation from gaseous precursors. In contrast, the harbor showed a dominant Aitken mode (25-100 nm) linked to ship emissions. Diurnal trends further reflected localized source activity, with distinct peaks observed in line with transport operations, except in the subway, where PNC remained relatively stable. PNSD was unimodal below 20 nm at the airport and traffic sites, unimodal around 20-30 nm at the harbor, and flatter at the subway, suggesting a lack of significant local sources of UFP. Notably, no second mode (40-90 nm), commonly associated to diesel emissions, was observed at the road traffic site, indicating a possible decline in larger diesel-related particles due to the implementation of EURO 5 and 6/V and VI standards and the Barcelona Low Emission Zone (LEZ). Source apportionment analyses confirmed aviation and shipping as dominant contributors to UFP at the airport and harbor, respectively, while chemical characterization revealed specific tracers such as aluminum (airport), chromium and barium (traffic), vanadium and nickel (harbor), and copper (subway), among others.
  

Reading date: 11/07/2025

• CALVO IBAÑEZ, ALBERT: User-Oriented Explainable AI (XAI) for Decision-Making in Critical Sectors
  
  Author: CALVO IBAÑEZ, ALBERT
  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 COMPUTING
  Department: Department of Computer Science (CS)
  Mode: Normal
  Deposit date: 04/04/2025
  Reading date: 11/07/2025
  Reading time: 11:00
  Reading place: FIB, Sala d'actes Manuel Martí Recober B6-planta 0
  Thesis director: ESCRIG ESCRIG, JOSEP
  Thesis abstract: The increasing integration of Artificial Intelligence (AI) into critical sectors demands a comprehensive understanding of decision-making processes to ensure trust and accountability. To address these challenges, Explainable Artificial Intelligence (XAI) has emerged as a research area aimed at enhancing the transparency of AI workflows. In detail, XAI seeks to provide insights into AI decision-making processes, thus improving trust and accountability. This dissertation explores the role of XAI in ensuring informed decision-making in critical sectors, focusing on the development and evaluation of explainability techniques tailored to real-world industrial scenarios that demand accurate XAI interfaces to ensure the usability in big data scenarios requiring time constrained explainability assesments. In detail, the dissertation contributes to the field by proposing novel interfaces and frameworks for XAI, designed to operate efficiently in big data environments. These contributions are validated through published works in reputable conferences and journals, demonstrating the practical utility and impact of the proposed methods. Ultimately, this research advances the understanding of XAI’s role in enhancing the transparency and accountability of AI systems, ensuring their safe and effective deployment in critical sectors.