Doctoral School

Reading date: 28/11/2025

• AL AWAD, ABDULRAHMAN: Multiscale Multiphysics Investigation of Helium Bubble Formation and Dynamics in Liquid Lead-Lithium Eutectic
  
  Author: AL AWAD, ABDULRAHMAN
  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 NUCLEAR AND IONISING RADIATION ENGINEERING
  Department: Department of Physics (FIS)
  Mode: Normal
  Deposit date: 03/11/2025
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: BATET MIRACLE, LLUIS | SEDANO MIGUEL, LUIS ANGEL
  Thesis abstract: Liquid metals (LMs) and their alloys are characterized with excellent thermophysical and dynamic properties for heat transport purposes, thus rendering them as promising candidates in advanced energy-production technologies such as the nuclear fusion energy. Liquid lead-lithium eutectic (LLE) alloy remains a key medium of the various breeding blanket (BB) concepts of the EU DEMO design. In LLE-BBs, helium (He) is produced in a mole-to-mole ratio with tritium by nuclear reactions, and technical concerns regarding the state of He in liquid LLE alloy have been raised since the 1990s. Gas-bubble nucleation in weak liquid–gas solutions has been a challenging topic in theory, experimentation, and computer simulations, especially given the expected very low solubility of He in LMs and the scarcity of experimental data. Despite the continuous efforts, the He nucleation issue still lacks conclusive findings and robust estimations of relevant parameters, and the main objective of this thesis is to exploit ab initio (AIMD) and classical molecular dynamics (CMD) simulations in order to shed light on the underlying physics and theory, and to estimate the thermodynamic and kinetic conditions required for He bubbles to nucleate and grow in a manner that facilitates the integration of results and findings into macroscopic models, e.g., CFD models, for engineering design and nuclear safety purposes. Additionally, it aims to pave the way and generally contextualize the use of atomistic simulations in the field. In the first part of this thesis, the invaluable AIMD methods using SIESTA code are utilized to support and justify the selection and construction of classical interatomic potentials, where liquid Li, Pb and LLE alloy are systematically investigated. In the second part, a classical potential of the embedded-atom-method class is parametrized for liquid Li using mechanical and non-mechanical properties. A mixing scheme is introduced to reproduce properties of liquid LLE alloy. To minimize the arbitrariness of functional forms, the parametrization schemes address the uniqueness problem. CMD simulations with LAMMPS code are performed to extensively investigate and estimate static and dynamic properties of pure LM and He/LM systems, both bulk and interfacial properties. In the third part, in analogy with recent advances in crystallization and droplet formation studies, the diffusive-shielding stabilization, the thermodynamic irreversibility of bulk nanobubbles (bNBs) mechanisms and the mean-first passage times theory are revisited and deployed to characterize the stability of He-bNBs in liquid LLE alloy, as inspired from bubble stability theories and experiments in closed and finite-volume systems. Namely, an analytical perturbation approach with an appropriate equation-of-state of He-bNBs and a stochastic and kinetic approach via forward CMD simulations are established, and the consistency and equivalency of both is demonstrated and thoroughly discussed. Most importantly, the underlying theoretical bases, assumptions, limitations and their computational counterparts are extensively described and illustrated. The overall proposed framework resolves ambiguities about the influence of the simulation domain and time on the observed bNBs in CMD simulations. Essentially, it provides a novel and plausible explanation for helium-bNBs existence and persistence by carefully assessing and estimating the thermodynamic equilibrium conditions; hence, their stability and longevity are shown not to be in violation of the fundamental laws of solubility and diffusivity, at least in CMD simulations and given the relatively high supersaturation levels. Lastly, thermodynamic and kinetic conditions required for the helium nucleation phenomena to take place at LLE-BBs operating conditions are inferred, based on the various investigated theories and performed computations, and coherently, macroscopic modelling suggestions and recommendations are provided.
  

• GONZÁLEZ ESPINOSA, VANESSA: Diseño de materiales cementícios reforzados con fibras vegetales impregnadas con materiales de cambio de fase para mejorar el comportamiento térmico de las cubiertas de los edificios.
  
  Author: GONZÁLEZ ESPINOSA, VANESSA
  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, BUILDING CONSTRUCTION AND URBANISM TECHNOLOGY
  Department: Department of Architectural Technology (TA)
  Mode: Normal
  Deposit date: 31/07/2025
  Reading date: 28/11/2025
  Reading time: 11:00
  Reading place: EPSEB (Escuela Politécnica Superior de Edificación de Bcn) - Sala de Actos Campus Diagonal Sur, Edificio P. - Av. Doctor Marañón, 44-50 - 08028 BCN
  Thesis director: CLARAMUNT BLANES, JOSE | LACASTA PALACIO, ANA MARIA
  Thesis abstract: In the current context, sustainable construction prioritises innovative materials that combine energy efficiency, mechanical strength and safety against extreme conditions, such as fire, in order to address the challenges of climate change and human needs. Fibre-reinforced cementitious composites and phase change materials (PCM) are emerging as a promising solution, particularly in raised roof pavements, where thermal regulation is essential. The main objective of this thesis is to develop a cement board reinforced with non-woven vegetable fibres and PCM for raised roof pavements, determining the optimal dosage of cement, fibres and PCM that maximises mechanical resistance and thermal regulation capacity, as well as analysing its response to fire. The research seeks to advance the integration of PCM and plant fibres into cementitious matrices, proposing improvements for their practical application in construction with an environmental focus.The methodology, which is highly experimental in nature, was structured in several stages. First, the state of the art on cementitious composites and PCM was reviewed, identifying trends and challenges. Subsequently, an experimental campaign was designed that included: selection of materials (commercial cements, non-woven fibres and pure and microencapsulated PCMs), formulation of mixtures with different proportions of fibres and PCMs compared to a control without PCMs, evaluation of mechanical properties (flexural strength), thermal properties (conductivity, thermal storage and retardation) and fire behaviour through standardised tests, and statistical analysis to determine the impact of each component.The results show that the incorporation of PCM RT28 through direct impregnation into non-woven fibres in cementitious composites improves thermal properties, achieving a delay in temperature changes comparable to that of microencapsulated PCM mixed into the cementitious matrix. However, the composite made with PCM RT28 has superior mechanical strength, with a modulus of rupture (MOR) approximately three times greater than that of the microencapsulated composite, although both show a decrease in strength compared to samples without PCM. The non-woven fibres, by effectively impregnating the PCM, reinforce the cohesion of the composite and preserve hardening by deformation, partially mitigating the loss of mechanical strength.Although both the vegetal fibres and the PCM used are organic in nature and therefore combustible, the cementitious composites exhibited good fire performance, with low-intensity flames and a high self-extinguishing capacity once the heat source was removed. Overall, the samples with PCM incorporated through fibre impregnation showed better fire behaviour than those formulated with microencapsulated PCM: although ignition occurred slightly earlier, the total heat released (THR), as measured in the cone calorimeter tests, was substantially lower.This combination, which has been little explored, balances thermal efficiency and structural functionality, with direct applications in sustainable buildings. The research provides a detailed analysis of the interaction between plant fibres, PCM and the cement matrix, proposing optimal dosages and strategies to mitigate fire-related risks. The results lay the foundations for future research and practical applications, promoting the development of more efficient and sustainable building materials.
  

• MAKHARADZE, DAVIT: Design and Application of PEGylated Pseudo-Protein Nanoparticles in Drug Delivery
  
  Author: MAKHARADZE, DAVIT
  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 POLYMERS AND BIOPOLYMERS
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 15/10/2025
  Reading date: 28/11/2025
  Reading time: 15:00
  Reading place: Sala Polivalent A0.3 Ed. A - EEBE Campus Diagonal Besòs. https://eebe.upc.edu/ca/lescola
  Thesis director: DEL VALLE MENDOZA, LUIS JAVIER
  Thesis abstract: In recent years, there has been growing interest in biodegradable and biocompatible polymeric nanoparticles (NPs) because of their versatile uses in drug delivery systems (DDSs). To improve the biological performance of these systems, PEGylation– the covalent attachment of polyethylene glycol (PEG) to the NP surface has been proposed, which improves NP stability, reduces protein adsorption, and extends circulation time.This thesis represents the synthesis, characterization, and biomedical applications of PEGylated NPs of poly(ester amide) (PEA) class. As part of the experimental work, four different types of polymer are presented in this thesis, labelled as follows: 8L6, unsaturated copolymers (precursors for PEG attachment)– [8L6]0.5-[tES-L6]0.5, (FuL6)0.5-(8L6)0.5 and their PEG conjugated adduct–PEG-PEA. Core-shell NPs are synthesized based on polymer 8L6 as a core and PEG-PEA as a shell. These biodegradable polymers (BPs) consist of the amino acid L-leucine, naturally occurring dicarboxylic acid, and diol units. The main advantages of these polymers consist of low to zero immunogenicity, high compatibility, and, at the same time, they release nutritive amino acids upon biodegradation. The polymers are designed in that way to have a non-proteinaceous molecular architecture, which is highly important to minimize immune recognition and rejection of the biomaterial.Chapter 3 describes the synthesis of polymer 8L6 and the initial design of precursor polymer [8L6]0.5-[tES-L6]0.5 for PEG attachment; the resulting PEG-PEA forms micelles similar to traditional surfactants. Additionally, stable core-shell 8L6 NPs with a size range of 100 to 200 nm were successfully prepared using the novel biodegradable surfactant PEG-PEA.Chapter 4 represents the synthesis of the new precursor (FuL6)0.5-(8L6)0.5, developed in response to the complexity and multi-step nature of the previous precursor’s synthesis. This copolymer contains equal mole percentages of unsaturated (FuL6) and saturated (8L6) repeating units designed for the special reason: the unsaturated fragments (FuL6) work for covalent attachment of PEG-derivatives and the saturated (anchoring) fragments (8L6) for immobilizing the PEGylating surfactant (PEG-PEA) to the surface of the drug-loaded NPs. Additionally, this chapter investigates the effect of various amine catalysts on the Michael addition reaction between (FuL6)0.5-(8L6)0.5 and thiol and amine-functionalized PEGs to optimize the reaction conditions.In chapter 5, the surface modification of 8L6 polymeric particles with PEG-PEA is studied by transmission electron microscopy (TEM) and synchrotron radiation-based FTIR (SR-FTIR) microspectroscopy. The formation of the core-shell structure is confirmed by both techniques.Finally, chapter 6 demonstrates the application of PEGylated 8L6 polymeric core-shell NPs. The anti-cancer potential of the phenolic compound resveratrol (RES) is evaluated using biodegradable vehicles. Those NPs are functionalized with the blood-plasma glycoprotein transferrin, which can bind to its receptor (transferrin receptor 1) highly expressed in tumour cells. The antiproliferative effects of RES-loaded NPs are studied in HeLa and U-87 cancer cell lines.Considering that synthesized NPs are biodegradable, biocompatible, and have high drug-loading capacity, this approach provides high efficiency for cancer therapy.
  

• MASSAROTTI, GIORGIO PAOLO: New Dual Steering System in a Compact Tractor
  
  Author: MASSAROTTI, GIORGIO PAOLO
  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 Mechanical Engineering (EM)
  Mode: Normal
  Deposit date: 01/10/2025
  Reading date: 28/11/2025
  Reading time: 10:00
  Reading place: Sala de Juntes, Ed. TR5, ESEIAAT
  Thesis director: GAMEZ MONTERO, PEDRO JAVIER | CODINA MACIA, ESTEBAN
  Thesis abstract: In order to achieve optimal controllability in a dual-steering tractor (a four-wheel, iso-diametric tractor equipped with a dual-hydraulic steering system), this thesis proposes a coordinated approach that combines experimental testing (using a special agricultural tractor) with numerical analysis of the entire vehicle, developed in Bond Graph-3D. After an exhaustive review of the scientific literature, it is observed that the compact tractor with dual steering, has not yet been thoroughly analysed. In this thesis, in chapter 1 it is possible to identify the reasons that led to the realization of this long work and the objectives that were set at the beginning. These objectives were born from the understanding of the state of the art relating to double steering in the off-road sector, focusing particularly on the case of a vineyard tractor. All starting from the basics, from the steering which occurs smoothly and through the variants that can be found on the market today. In light of the machine construction information, the model of the studied tractor was introduced, searching the literature for the methods and models that could describe its dynamic behavior. In order to detail the description, the hydraulic circuit chosen based on the requirements listed in chapter 4 was introduced and an analysis to its modeling combined with the dynamic model of the tractor using Bond-Graph was provided. At the same time, experimental tests were carried out with a prototype tractor which incorporated the hydraulic circuitpreviously described, together with the dynamic model of the tractor, also obtained through modeling from the physical machine. The numerical analysis provided results that match very well with the experimental data, providing the key to the "salient" factors that characterize the tractor's steering capacity. A threshold can be set, relative to the vehicle speed, to disable dual-steer mode when a certain speed is exceeded. Based on experimental data, this threshold is set around 8.5 km/h. In conclusion, there are possibilities for future development that would lead the system described to a new circuit capable of appreciating not only the factors that determine the drivability of the tractor, but also of managing possible dangerous conditions for the user.
  

• OLIVER SEGURA, JOSÉ: Accelerating SpMV on HBM-equipped FPGAs: Hardware-Software Co-design and Collaboration
  
  Author: OLIVER SEGURA, JOSÉ
  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: 27/10/2025
  Reading date: 28/11/2025
  Reading time: 12:30
  Reading place: Sala C6-E101
  Thesis director: AYGUADÉ PARRA, EDUARD | MARTORELL BOFILL, XAVIER
  Thesis abstract: SpMV is a key linear algebra kernel at the core of many algorithms across multiple knowledge domains. Its memory-bound nature and its low arithmetic intensity make its efficient implementation a challenging problem. Usual mechanisms present in general-purpose microprocessors, such as cache memories, become useless without further data transformation as the size of the problem grows beyond the capacity of the cache. The capability of FPGAs to generate application-specific logic and memory hierarchies results in performant and energy-efficient designs. This has made them an interesting alternative when trying to efficiently implement SpMV. The push by vendors to position them as HPC accelerators and the inclusion of HBM in the last generations of boards have increased this trend. Most SpMV implementations for FPGAs allow to work exclusively using single-precision floating-point arithmetic, while in the context of HPC applications, double-precision floating-point arithmetic is usually required. CSR or slightly modified versions of it are usually used as the basis for these implementations. This limits inter and intra-row parallelism due to conflicts in memory accesses, requiring the implementation to include complex logic such as arbitration or stall/retry mechanisms or to use replicated memories, increasing resource usage and limiting the scalability of the designs. This thesis presents two proposals to leverage the features offered by FPGAs, especially HBM and customizable memory hierarchies, to further improve the achieved performance and, in the case of the second proposal, allowing for a precision-agnostic design that can be synthesized to work with different arithmetic types as required.The first proposal consists of a double-precision FPGA co-designed SpMV accelerator and matrix representation. Instead of using CSR as the basis, the representation and the accelerator are defined considering all the advanced features that FPGAs offer, in a co-design approach. This approach allows maximization of inter-row and intra-row parallelism by allowing simultaneous processing of several matrix values per cycle in a fully pipelined fashion without requiring complex logic or memory replication. The proposed matrix representation allows the easy partitioning of work among different accelerators and the efficient use of HBM bandwidth. The evaluation shows that the proposed implementation outperforms state-of-the-art implementations in terms of absolute, bandwidth-relative, and energy-relative performance.The second proposal builds on the first one, increasing its arithmetic efficiency. It does so in different ways. In the first place, it improves the efficiency of the proposed encoding by reducing the amount of metadata required to process the matrix. In the second place, it increases the useful data ratio of the transformed representation by considering new hierarchical abstractions within the matrix. In the third place, it repurposes zero-padding, when present, to act as a carrier of useful data. This proposal is highly parametrizable, including the possibility of using it to generate designs working with different data types without requiring more changes than setting the desired data type at compile time. The evaluation shows that this proposal significantly improves over the first one in double-precision arithmetic. Single-precision results demonstrate its capability to improve the performance offered by state-of-the-art designs that use much higher bandwidth.