Doctoral School

Reading date: 27/05/2026

• RUIZ CARREGAL, GERARD: High-Resolution Drone-Based Repeat-pass SAR Interferometry for 3D displacement estimation
  
  Author: RUIZ CARREGAL, GERARD
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Article-based thesis
  Deposit date: 15/04/2026
  Reading date: 27/05/2026
  Reading time: 11:00
  Reading place: Sala D4 012, UPC Campus Nord.
  Thesis director: LOPEZ MARTINEZ, CARLOS | IGLESIAS GONZÁLEZ, RUBÉN | LORT CUENCA, MARC
  Thesis abstract: The precise characterization of ground deformation processes is essential for risk assessment and early-warning applications, since displacement is often a precursor to catastrophic failures. Over the past two decades, Synthetic Aperture Radar (SAR) and Multi-Temporal Differential SAR Interferometry (MT-DInSAR) have enabled millimetric displacement estimation over wide areas with dense spatial sampling. Within this context, satellite-based SAR offers regular, long-term global coverage, while Ground-Based SAR (GBSAR) provides near real-time monitoring, enabling the observation of localized rapid deformation processes. Despite these strengths, both systems present inherent limitations. Satellite SAR cannot capture rapid displacements due to multi-day revisit intervals and provides no sensitivity to displacement along the North-South (NS) direction due to its near-polar orbits. GBSAR provides excellent temporal resolution, but its deployment is limited in inaccessible areas, and its fixed geometry often leads to displacement underestimation.Airborne SAR systems mitigate several of these limitations by offering controlled revisit times and multi-view imaging, allowing the retrieval of the three-dimensional (3D) displacement vector. In this context, multirotor drones have emerged as a cost-effective and adaptable platform for airborne SAR. Drone-borne SAR inherits airborne challenges related to platform motion and navigation uncertainties, together with additional constraints such as payload limitations, and requires the adaptation of MT-DInSAR algorithms to low-altitude platforms and non-regular revisit times.The objective of this dissertation is to demonstrate the capability of drone-based SAR systems to estimate ground displacement time-series using multi-temporal interferometric stacks in real operational scenarios. To this end, the thesis develops an end-to-end framework encompassing sensor development, interferometric processing, and MT-DInSAR methodologies. A Ku-band dual-channel Frequency-Modulated Continuous-Wave (FMCW) radar is developed and integrated into a multirotor platform. An interferometric processing chain is further proposed to generate phase-calibrated repeat-pass interferograms, combining Digital Elevation Model (DEM) refinement from single-pass interferometry with a dedicated coregistration strategy, where the MTCD-MSQ algorithm is introduced as a new coregistration approach designed for high-frequency airborne acquisitions. Furthermore, two complementary MT-DInSAR workflows are proposed to address distinct deformation regimes. SD-MT-DInSAR retrieves cumulative displacement time-series when interferometric coherence is preserved between consecutive acquisitions, while SDVEL-MT-DInSAR exploits the flexibility of drones to perform repeated intra-day flights to estimate displacement velocity time-series in rapidly deforming areas, where decorrelation occurs in a few hours. Finally, the thesis employs multi-geometry acquisitions to retrieve the full 3D displacement vector.The framework is validated in controlled experiments with Corner Reflectors (CR) and in real operational conditions over an active open-pit mine, demonstrating submillimetric sensitivity, meter-scale displacement monitoring over several days, and 3D displacement retrieval in complex scenarios.The dissertation confirms that drone-based SAR is a reliable deformation monitoring tool that complements satellite and GBSAR systems, opening new opportunities in geotechnics, mining, and natural hazard assessment.
  

Reading date: 28/05/2026

• GAMARRA GAMARRA, MARÍA DEL PILAR: Comportamiento Ético: Identidad Moral, Atención Moral y su papel en la Construcción del Liderazgo Ético
  
  Author: GAMARRA GAMARRA, MARÍA DEL PILAR
  Programme: DOCTORAL DEGREE IN BUSINESS ADMINISTRATION AND MANAGEMENT
  Department: Department of Management (OE)
  Mode: Normal
  Deposit date: 30/04/2026
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: OLIVELLA NADAL, JORGE | GIROTTO, MICHELE
  Thesis abstract: When a leader acts without ethics, the entire organization is shaken; when leadership is exercised with integrity, it inspires sustainable cultures and strengthens social trust. This doctoral thesis addresses the challenge of understanding how leaders perceive and enact their own ethical behavior, focusing on two fundamental internal drivers: moral identity and moral attentiveness. These factors, often invisible in everyday organizational discourse, distinguish formal leadership from authentic leadership capable of generating legitimacy, resilience, and commitment in complex contexts.The research is grounded in a clear diagnosis: financial scandals, corporate misconduct, and growing social demands for transparency have placed ethics at the center of the business agenda. However, most previous studies have examined ethical leadership from the perspective of subordinates or within Anglo-Saxon contexts, leaving aside the leader’s own viewpoint and the analysis of specific cultural realities such as the Spanish context. This is the gap that the thesis seeks to address.The study is developed in two phases. The first presents a bibliometric analysis and a systematic review of more than thirty years of scientific literature, identifying three theoretical pillars of ethical leadership: values-based theories, cognitive moral development theory, and social learning theory. This review highlights the fragmentation of existing approaches and the scarcity of empirical studies focused on leaders’ self-perceptions, as well as the need to incorporate variables such as gender, age, and hierarchical level.The second phase builds an empirical model applied to the Spanish context. To this end, the classic ethical leadership scale is psychometrically validated and adapted to leaders’ self-perceptions through exploratory and confirmatory factor analyses, reliability tests, and structural equation modeling. The process includes expert review, pilot testing, and the administration of questionnaires to a sample of managers from different sectors. The result is a robust, context-adapted scale that identifies three dimensions of self-perceived ethical leadership: integrative decision-making, the reinforcement of ethical behaviors, and the leader’s personal example as a role model.The findings show that moral identity and moral attentiveness significantly influence these dimensions, albeit in different ways. The internalization of moral identity predicts the integration of ethical principles into decision-making, while the symbolization of moral identity and reflective moral attentiveness explain the tendency to reinforce ethical behaviors. In addition, variables such as gender, age, managerial experience, and hierarchical position act as moderators, indicating that ethical leadership emerges through the interaction of personal and professional characteristics.Overall, this thesis demonstrates that ethical leadership is not an abstract code or a superficial discourse, but a practice rooted in the leader’s internal coherence, reflected in decision-making, and projected onto organizational culture, contributing to the development of more just and sustainable organizations.
  

• JURADO ROMERO, ARNAU: Self-Propulsion of Molecular Swimmers
  
  Author: JURADO ROMERO, ARNAU
  Programme: DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS
  Department: Department of Physics (FIS)
  Mode: Normal
  Deposit date: 28/04/2026
  Reading date: 28/05/2026
  Reading time: 11:00
  Reading place: Sala de Juntes de la FIB
  Thesis director: REY ORIOL, ROSENDO | CALERO BORRALLO, CARLOS
  Thesis abstract: Active matter systems have the ability to exhibit self-propulsion by consuming energy to produce mechanical work, staying out of equilibrium. They occur on a vast range of scales, from herding mammals and flocking birds down to bacteria. Understanding these systems requires the study of the mechanisms that drive the system out of equilibrium and the emergent collective phenomena that result from activity. Both these questions require a multidisciplinary approach, the innovative application of classical non-equilibrium physics, as well as the development of new theoretical frameworks.A major goal in the field is the development of artificial micro- and nano-scale particles capable of self-propulsion, so-called swimmers. These swimmers hold the potential for groundbreaking applications, such as targeted drug delivery, non-invasive microsurgery, and water purification.This overarching technological goal is met with a number of theoretical and practical challenges, of which the search for viable propulsion mechanisms at the nano-scale is only one of them. However, achieving propulsion at such small scales is limited by the hydrodynamic regime characteristic of these scales, in which reciprocal deformations cannot produce net propulsion. In addition, rotational diffusion, which severely hinders the self-propelling capabilities of a swimmer, increases rapidly with diminishing size.This thesis demonstrates a propulsion mechanism for a small molecule, nitromethane, via all-atom molecular dynamics simulations. The molecule is subject to a high energy vibrational excitation which is then released anisotropically onto the surrounding water solvent. This results in propulsion velocity bursts that are able to enhance the translational diffusion of the molecule. Making use of the all-atom nature of the simulations, the propulsion is explained mechanistically and in terms of self-thermophoresis, an ubiquitous mechanism in micro-metric self-propelling colloids. The nitromethane model thus constitutes the smallest example of a self-propelling particle.Motivated by these findings, the dynamics of self-propelled particles under periodic time dependent propulsion velocities are investigated. By extending the popular Active Brownian Particle (ABP) model, we obtain the translational diffusion enhancement of exponentially decaying propulsion, similar to the one exhibited by nitromethane. The results show that narrow, intense, peaks of activity, sufficiently spaced in time, are able to greatly enhance the diffusion of the swimmer. This strategy provides new avenues for mitigating the negative effect of rotational diffusion as swimmers are downsized.The collective dynamics of a many-body system of self-propelled particles under exponentially decaying periodic activity are also investigated. A well-known collective phenomenon in active matter is the emergence of Motility Induced Phase Separation (MIPS), consisting in the activity-driven phase separation into dense and dilute phases. The inclusion of time modulation in the system results in a significant alteration of the MIPS phase diagram, which has been thoroughly characterized. In some cases, phase separation is severely suppressed, allowing the system to remain as a single homogeneous phase while maintaining high mobility particles.Finally, a class of state-of-the-art machine learning interatomic potentials, based on neural networks, is presented and utilized for the study of thermophoresis, a phenomenon closely related to the propulsion mechanism of nitromethane and with a marked sensitivity to solute-solvent interactions. Neural network potentials allow the exploration of large scale systems with precision rivaling first-principles quantum calculations. These new algorithms are being developed at a fast pace and allow for the accurate characterization of condensed matter systems, a critical ingredient in the development of functionalized self-propelling particles.
  

Reading date: 29/05/2026

• MALLA, ADITYA JAGADEESH: COLLOIDAL QUANTUM DOT EMITTERS IN THE SHORTWAVE INFRARED REGION
  
  Author: MALLA, ADITYA JAGADEESH
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 16/04/2026
  Reading date: 29/05/2026
  Reading time: 10:00
  Reading place: ICFO Auditorium
  Thesis director: KONSTANTATOS, GERASIMOS
  Thesis abstract: Shortwave infrared (SWIR) light sources are indispensable for applications including advanced imaging, spectroscopy, and sensing; however, their widespread adoption is hindered by the high cost and limited scalability of epitaxial semiconductor technologies such as InGaAs. Colloidal quantum dots (QDs) offer an attractive alternative owing to their high photoluminescence quantum yield, size-tunable emission, large-area processability, and compatibility with low-cost solution-based fabrication. Among various QD-based emitters employing lead sulphide (PbS), this thesis focuses on two complementary technologies: electrically driven quantum-dot light-emitting diodes (QLEDs) and optically pumped downconverters (DCs).The first part of this thesis addresses performance enhancement in QLEDs (emitting at 1380 nm) through systematic device engineering. Charge imbalance is identified as a key factor limiting QLED efficiency and radiance. By optimising the ZnO electron transport layer via controlled annealing-temperature tuning, electron injection was modulated, leading to a maximum external quantum efficiency (EQE) of 20%. Furthermore, the charge balance within the emissive layer was optimised by controlling its thickness, resulting in an increase in maximum radiance from 5 W.sr-1.m-2 to 17.5 W.sr-1.m-2. Building upon this, a dual electron transport layer architecture was implemented to decouple interfacial quality from bulk electron transport, enabling a further enhancement in maximum radiance to 30 W.sr-1.m-2 while maintaining comparable EQE.Light extraction and Joule heating constitute an additional bottleneck in achieving high-performance QLEDs. To overcome substantial optical losses into substrate modes inherent in conventional bottom-emission devices, top-emission QLED (TQLED) architectures were investigated. These offer improved light extraction and allow for the use of opaque, high-thermal-conductivity silicon substrates to manage Joule heating. A high-performance sputtered indium tin oxide (ITO) electrode was developed, exhibiting optical transmission exceeding 85% at 1400 nm and a low sheet resistance of 33 Ω/□. By utilising optimised architecture with integrated ITO optical spacers and a dielectric/metal/dielectric top electrode, a low-Q microcavity was established. This modified the far-field radiation pattern to a forward-directed profile and narrowed the emission linewidth. The synergy between this resonant optical design and superior thermal dissipation enabled a record radiance exceeding 100 W.sr-1.m-2, and allowed for the first demonstration of active see-through SWIR imaging illuminated solely by QLEDs.The second part of the thesis is focused on lead sulphide QD-based DCs. The QD-DCs suffer from performance degradation under high excitation power densities due to the significant heat generation in the process of light absorption. We have developed high-power, stable, and spectrally tunable narrowband and broadband SWIR DCs (1000 nm - 1600 nm). By mixing two different-sized QDs, we exploit Förster resonance energy transfer and photon reabsorption to realise a binary system with a high photoluminescence quantum yield of 35 %. Embedding the QDs in a poly(methyl methacrylate) host mitigates local thermal stress on the QDs, enabling standalone DCs with a high emission power density (EmPD) of 110 mW.cm-2 at 1380 nm. Further optimisation with a spectrally selective distributed Bragg reflector for enhanced light extraction and a sapphire substrate for efficient heat dissipation, we achieved a record EmPD of 385 mW.cm-2 at 1380 nm with optical power conversion efficiency of 10% and operational stability above 230 hours at an EmPD of 190 mW.cm-2. This demonstrates a scalable route to low-cost SWIR light sources, narrowing the performance gap between solution-processed DCs and conventional epitaxial semiconductors.
  

• MOSAHEBFARD, MOHAMMADREZA: Resource Management in Sliced Converged Optical-Wireless 6G Networks: From Strategic Dimensioning to Dynamic Service Provisioning
  
  Author: MOSAHEBFARD, MOHAMMADREZA
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 10/04/2026
  Reading date: 29/05/2026
  Reading time: 11:00
  Reading place: Room C4-021B at the Castelldefels Campus
  Thesis director: VERIKOUKIS, CHRISTOS | VARDAKAS, JOHN
  Thesis abstract: The evolution toward the 6th Generation (6G) networks relies on converged optical-wireless infrastructures and virtualization technologies like Network Functions Virtualization (NFV) to support diverse services through Network Slicing. While enabling flexibility, these paradigms introduce profound complexity in managing shared computational and com-municational resources. This thesis addresses this challenge by identifying a fundamental temporal duality in resource management, spanning the strategic need for agile capacity planning to the operational necessity of real-time service provisioning. This complexity is further aggravated by the presence of various network slices, each with distinct Quality of Service (QoS) requirements. To resolve this dichotomy, distinct methodologies are developed within this PhD thesis.To address the strategic domain, where Mobile Virtual Network Operators (MVNOs) require rapid dimensioning tools for flexible resource leasing, this PhD thesis develops a computationally efficient analytical framework based on one-dimensional Markov chains. Uniquely, this model captures resource occupancy at two levels: physical resources governing Service Function Chain (SFC) instantiation, and virtual resources governing user admission. This stratified modeling avoids state-space explosion while accurately calculating admission ratios, achieving relative errors typically below 2% compared to simulations. The framework is applied to determine the minimum resources required to achieve target admission ratios under varying arrival rates, as well as to identify the necessary capacity to meet different target admission rates under constant traffic loads. This capability enables rapid offline dimensioning to guarantee Quality of Service (QoS) thresholds, offering a scalable alternative to time-consuming simulations and resource-exhaustive optimization approaches.Complementing this, the operational challenge of online SFC Embedding (SFCE) is addressed. Recognizing the NP-hardness of the embedding problem with the objective of jointly minimizing holistic power consumption and blocking probability, HORIZON, a novel holistic heuristic designed to optimize Mobile Virtual Network Operator (MVNO) operational efficiency, is developed. It employs a proactive backward placement strategy coupled with power and latency-aware segmental routing, and integrates comprehensive power models for both servers and Reconfigurable Optical Add-Drop Multiplexers (ROADMs). By enforcing strict inter-slice isolation while maximizing intra-slice efficiency, HORIZON achieves power efficiency within 15% of optimal Integer Linear Programming (ILP) bounds under resource-constrained scenarios. Evaluations across four realistic network topologies demonstrate execution times of 10–18 ms per service request (38–67 times faster than optimal solvers), power savings up to 23.6% compared to state-of-the-art heuristics, and negligible blocking rates, enabling MVNOs to minimize OPerational EXpenditure (OPEX) while strictly adhering to Service Level Agreements (SLAs).