Doctoral School

Reading date: 01/10/2026

• VILELLA I CROSAS, TÀNIA: Biocompatible superelastic TiNb-based alloys produced by additive manufacturing
  
  Author: VILELLA I CROSAS, TÀNIA
  Programme: DOCTORAL DEGREE IN MATERIALS SCIENCE AND ENGINEERING
  Department: Department of Materials Science and Engineering (CEM)
  Mode: Normal
  Deposit date: 02/09/2026
  Reading date: 01/10/2026
  Reading time: 12:00
  Reading place: ESCOLA D'ENGINYERIA BARCELONA ESTC/Eduard Maristany, 16 (08019 Barcelona)EDIFICI A planta 0, SALA D'ACTEShttps://meet.google.com/hzr-ymub-uum
  Thesis director: FARGAS RIBAS, GEMMA | RODRÍGUEZ RIUS, DANIEL
  Thesis abstract: The clinical success of load-bearing orthopaedic implants is fundamentally constrained by two major mechanical and biological limitations: the stress-shielding phenomenon induced by the high elastic modulus mismatch between standard titanium alloys (e.g Ti-6Al-4V) and human cortical bone, and the long-term risk of systemic toxicity or hypersensitivity associated with superelastic shape memory alloys like NiTi. Ni-free, β-type TiNb systems offer an ideal biocompatible alternative due to their inherently low stiffness and capacity for superelastic behaviour. However, conventional processing methods (casting and forging) lead to severe phase segregation, while conventional additive manufacturing (AM) routes remain restricted by the high cost and processing rigidity of pre-alloyed spherical feedstocks. To address this gap, this Thesis establishes novel, cost-effective AM pathways to fabricate complex, bone-mimetic architectures directly from irregular elemental powder blends using two distinct approaches: Direct Ink Writing (DIW) combined with vacuum sintering, and high-energy Electron Beam Powder Bed Fusion (PBF-EB).The first part of this work optimizes the extrusion-based DIW route for binary TiNb configurations. Rheological screening identified an optimal solid powder loading of 75 wt.%. This concentration maximizes green metallic density. It also maintains the shear-thinning behaviour and yield stress needed for shape retention post-printing. Pushing the loading to 80 wt.% triggers a micro-rheological jamming transition. This jamming is driven by internal friction between the irregular elemental particles. Vacuum sintering cycles were mapped to control the evolution of densification and porosity. Open, tubular pore networks successfully consolidated into isolated internal porosity. The macro-porous architecture was preserved. Nb acts as a β-stabilizer and suppresses α-phase formation. This results in a compliant body-centered cubic (bcc) β-matrix. Instrumented micro- and nanoindentation profiling evaluated the local mechanics. The macro-apparent stiffness of the porous scaffolds successfully matched human cortical boneIn the second part of this Thesis, ink formulation was expanded to ternary (TiNbZr, TiNbTa) and and quaternary (TiNbTaZr) systems. This approach achieved successful in-situ alloying. The third part of the thesis investigates single-step liquid-state consolidation via high-energy PBF-EB. A narrow process window was developed. The intense hydrodynamic mixing overcomes the large melting temperature gap between Ti and refractory Nb. The high vacuum and in-situ thermal annealing eliminate macro-segregation. This process results in homogeneous, single β-phase or metastable α’’-phases.The compliant β-phase was integrated with advanced Triply Periodic Minimal Surface (TPMS gyroid) designs to mitigate stress-shielding. Finally, in vitro biological validation using SaOs-2 osteoblast-like cells was performed across the three parts of this Thesis, demonstrating outstanding cytocompatibility in all cases.Conclusively, this Thesis demonstrates flexible, cost-effective, and versatile manufacturing strategies that bridge the gap between low-cost elemental feedstocks and high-performance functional materials. By integrating architectural complexity with precise microstructural control, this work establishes a robust pathway for the development of the next generation of bone-mimetic, superelastic implants, ultimately enhancing patient safety and long-term clinical reliability.
  

Reading date: 02/10/2026

• GARCÍA CARRASCO, VÍCTOR: El nexe aigua-energia de Catalunya davant la transició energètica: simulació horària, dessalinització oportunista i optimització multi-objectiu
  
  Author: GARCÍA CARRASCO, VÍCTOR
  Programme: DOCTORAL DEGREE IN STATISTICS AND OPERATIONS RESEARCH
  Department: Department of Statistics and Operations Research (EIO)
  Mode: Normal
  Deposit date: 02/09/2026
  Reading date: 02/10/2026
  Reading time: 11:00
  Reading place: FIB Sala d'actes Manuel Martí Recober B6-planta 0
  Thesis director: FONSECA CASAS, PAU
  Thesis abstract: Catalonia simultaneously faces two structural crises: the transition towards a decarbonised electricity system and the worsening of water stress under climate change. The 2021-2024 drought, which brought Ter-Llobregat system reservoirs to emergency levels, and the accelerated renewable deployment envisaged by the PROENCAT plan highlight the need for planning tools that integrate both subsystems. This thesis provides the tools to develop the first digital twin of Catalonia's coupled water-energy system at hourly resolution, formally specified using the SDL (Specification and Description Language) framework following the DT = DM + DS paradigm.The model integrates electricity generation (nuclear, wind, solar PV, hydropower, storage and combined cycles), water management (reservoirs, desalination, reclaimed water) and drought policies (progressive restriction phases) within a single simulation framework. It has been validated retrospectively against the 2024 electricity mix (errors < 2%), prospectively against PROENCAT projections for the 2030 and 2040 horizons, and under stress through 5 hydrological perturbation scenarios. The solution space, with until 14 decision variables, has been explored using Random Grid Search and NSGA-II, enabling a methodological comparison of both multi-objective optimisation approaches.Results demonstrate that the planned desalination capacity of 160 hm³/year is necessary but insufficient under severe climate change scenarios, and that 240 hm³/year effectively provides a robust safety margin. An opportunistic desalination strategy is proposed and evaluated, linking plant operation to renewable surplus availability and achieving 49-75% of water production during surplus hours, with a 20-34% reduction in gas consumption. The model confirms the viability of PROENCAT targets for 2040 and identifies 14.8 TWh of renewable surpluses as a fundamental synergy between the energy transition and water security.This thesis contributes in three areas: the formal integration of the water-energy nexus at regional basin scale, the formulation of an opportunistic desalination strategy without precedent in the literature, and a comparative multi-objective optimisation methodology transferable to other Mediterranean basins.
  

• HURTÁN DÍAZ, ENRIQUE: Experimental Characterization of Microconfined High-Pressure Transcritical Fluid Turbulence
  
  Author: HURTÁN DÍAZ, ENRIQUE
  Programme: DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING
  Department: Department of Mechanical Engineering (EM)
  Mode: Normal
  Deposit date: 04/09/2026
  Reading date: 02/10/2026
  Reading time: 09:00
  Reading place: Sala de conferències/polivalent de l'edifici I del Campus Diagonal-Besòs, EEBE.
  Thesis director: JOFRE CRUANYES, LLUÍS | CASALS TERRE, JASMINA
  Thesis abstract: Microfluidic systems have emerged as a key enabling technology for compact and highly integrated devices across biomedical and chemical applications. However, their performance remains fundamentally constrained in energy-related applications due to the predominance of laminar flow regimes at small scales, where transport processes are governed primarily by molecular diffusion. This thesis investigates the emergence of turbulent-like flow regimes in microconfined high-pressure transcritical fluids as a novel pathway to overcome these limitations. In particular, the work focuses on the role of strong thermophysical property gradients generated near the critical point and while crossing the pseudo-boiling line in destabilizing microscale flows, enhancing mass and heat transport.The research begins by establishing the experimental and methodological framework required to investigate transcritical microflows under extreme thermodynamic conditions. A dedicated high-pressure microfluidic facility is developed, integrating advanced thermal control and high-speed optical diagnostics based on two-dimensional time-resolved micro-particle image velocimetry (2D TR-μPIV). Particular attention is devoted to identifying the characteristic spatio-temporal scales governing these flows and to assessing the limitations of conventional techniques in resolving the smallest turbulent scales. The analysis reveals that thermophysical scales associated with density gradients become comparable to the smallest hydrodynamic scales of the flow, leading to strong thermodynamic–hydrodynamic coupling and fundamentally altering the interpretation of microscale transport.Building upon this framework, the thesis experimentally demonstrates the existence of instability-driven turbulent-like regimes in microchannels operating under transcritical conditions. The results show that sharp density gradients generate baroclinic torque and variable-density effects that help to trigger and amplify flow perturbations, developing highly unsteady multiscale flow structures even at Reynolds numbers significantly below the transition thresholds of classical incompressible flows. Flow visualizations reveal the presence of fluctuations represented by optical distortions and turbophoretic particle migration, providing direct experimental evidence of turbulent-like dynamics previously predicted by direct numerical simulations.The impact of these regimes on transport processes is subsequently investigated through the development of a microchannel heat exchanger platform. To support these experiments, a novel hybrid custom-fabricated platform based on Ostemer–copper bonding is developed, enabling high-pressure operation while preserving optical accessibility and thermal control. Heat transfer measurements demonstrate substantial enhancement of convective transport under transcritical conditions, directly linked to the emergence of multiscale flow structures and instability-driven mixing. These results establish a direct connection between the underlying flow physics and the observed macroscopic thermofluid performance.Taken together, the findings in this thesis demonstrate that turbulent-like transport in microfluidic systems can be achieved not by increasing inertial forces, but by exploiting the thermodynamic behavior of fluids near the critical point. This work establishes a new paradigm for microscale transport enhancement based on thermodynamic–hydrodynamic coupling, and opens new opportunities for the development of high-performance microfluidic technologies for thermal management, energy conversion, and process intensification applications.
  

• KALLINGER, MAGNUS DANIEL: Layout Optimization in Floating Offshore Wind with Focus on Subsea Components
  
  Author: KALLINGER, MAGNUS DANIEL
  Programme: DOCTORAL DEGREE IN CIVIL ENGINEERING
  Department: Barcelona School of Civil Engineering (ETSECCPB)
  Mode: Normal
  Deposit date: 06/07/2026
  Reading date: 02/10/2026
  Reading time: 12:00
  Reading place: UPC Campus Nord, ETSECCPB, C/ Jordi Girona 1-3, edificio C1, Sala 002, Barcelona
  Thesis director: DOMÍNGUEZ GARCÍA, JOSÉ LUIS | TRUBAT CASAL, PAU
  Thesis abstract: Floating offshore wind is regarded as a key technology for exploiting deep-water wind resources where bottom-fixed foundations become economically uncompetitive. Yet, large-scale floating wind deployments remain constrained by high cost, limited maturity, and strong multidisciplinary coupling among subsystems that jointly determine farm feasibility and performance. Subsea components are central to this coupling: station-keeping systems and dynamic/static power cables govern not only structural response and electrical performance, but also impose first-order constraints on wind-farm design (turbine placement, anchoring footprints, cable topology and routing corridors). In addition, the limited practicality of subsea instrumentation motivates monitoring strategies that can reduce O&M burden and support condition-based operation. In this context, this thesis addresses layout optimisation for floating wind with a focus on subsea components. The thesis is organised around three research lines, aligned with the subsequent contribution chapters. First, it develops an early-stage optimisation framework for station-keeping design that combines computationally efficient frequency-domain simulations with customised particle swarm optimisation to screen large design spaces (layouts, materials, and ancillary components). The framework is applied both to conventional floating wind platforms and to a single-point moored weathervaning concept. Second, it investigates virtual sensing for floating wind turbines to estimate critical mooring and structural loads from accessible measurements, motivated by the high installation and maintenance effort of subsea sensors and by the need for scalable monitoring. Third, it advances floating wind inter-array design through (i) farm-level topology optimisation that incorporates floating-specific cable length effects and techno-economic performance, and (ii) physically informed routing that explicitly accounts for floater offsets, mooring-cable interaction constraints, touchdown feasibility, and three-dimensional bathymetry. The results show, first, that early-stage station-keeping optimisation can be carried out efficiently while producing technically meaningful and cost-effective designs, and it highlights the importance of line-specific functionality, substructure type, and site-dependent choices. Second, the virtual sensing studies demonstrate that critical loads can be estimated with useful accuracy and improved robustness when physical structure is embedded into the learning process, enabling reduced reliance on subsea instrumentation. Third, in the electrical domain, the proposed topology and routing methods improve the physical consistency and feasibility of floating wind cable layouts and yield measurable reductions in cable length and investment cost, which propagate to lower levelized cost of energy. Relative improvements are modest, but the absolute savings become significant at farm scale.
  

• RIVERA TORRES, PEDRO JUAN: Complex Engineering Systems: Expanding the Bioengineering Toolset with Biomimetic and Complexity Science-Based Solutions to Engineering Problems.
  
  Author: RIVERA TORRES, PEDRO JUAN
  Programme: DOCTORAL DEGREE IN BIOMEDICAL ENGINEERING
  Department: Department of Automatic Control (ESAII)
  Mode: Article-based thesis
  Deposit date: 13/07/2026
  Reading date: 02/10/2026
  Reading time: 11:00
  Reading place: Sala Polivalent, Edifici A, Av. d'Eduard Maristany, 16, 08019 Barcelona, Escola d'Enginyeria de Barcelona Est (EEBE)
  Thesis director: KANAAN IZQUIERDO, SAMIR
  Thesis abstract: This dissertation will seek to expand the toolset available for the solution of problems in engineering using probabilistic Boolean networks (PBN), a modeling methodology used mainly for analyzing Gene Regulatory Networks (GRN). Its purpose is validating their benefits as mechanisms of problem solving in engineering; general machine learning, reinforcement learning and fault detection and isolation in generation and transmission/distribution of electrical power and in manufacturing systems. The use of PBNs has been validated before as a mechanism of modeling of manufacturing processes and smart power. Modeling of systems using PBNs allows to construct models of multiple systems, know their respective failure modes, and incrementing their robustness using reinforcement learning to predictively react to faults and failures. We present the use of PBNs as a model constructing mechanism to determine the reliability of engineered systems and processes, and control of their evolution using machine learning. These models will enable us to study the mechanics of failure in engineered systems, making them more robust. We also present a Learning Probabilistic Boolean Network model of a manufacturing system and a Smart-grid system that can learn to preserve a healthy system state, in a way inspired by Artificial Neural Networks, but without the training that these systems require, and allowing the system to avoid faults and failures.