Doctoral School

Reading date: 23/04/2024

• ALBUQUERQUE PORTELLA, FELIPE: A paradigm shift of HPC for geosciences: a novel HPC service model for geosciences applications
  
  Author: ALBUQUERQUE PORTELLA, FELIPE
  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: 25/03/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: BERRAL GARCÍA, JOSEP LLUÍS | CARRERA PÉREZ, DAVID
  Committee:
       PRESIDENT: FONTOURA DE GUSMAO CERQUEIRA, RENATO
       SECRETARI: TOUS LIESA, RUBÉN
       VOCAL: DE MORAES, RAFAEL JESUS
  Thesis abstract: The Oil and Gas (O&G) industry ranks prominently among the leading commercial users of powerful supercomputers worldwide, as indicated by global High-Performance Computing (HPC) ranking lists, such as TOP500 and Green500. Geoscience applications, particularly flow and geomechanical simulators, pose demanding workloads for HPC in adressing complex engineering challenges in the O&G industry, together with seismic processing. The rise of hybrid on-demand and cloud HPC environments presents new challenges to end users. Beyond expertise in their fields, users must navigate the intricacies of computer architecture to select the optimal hardware and parallelization option. They also need to consider the business model decisions of the cloud providers, such as managing spot instances, selecting different cloud regions, or even different cloud providers.Furthermore, users struggle with the complexities of configuring their own geoscience software due to the multitude of tunable numerical parameters. Default values may not be optimal for specific reservoir models, requiring geoscientists¿ expertise in both the physics and mathematics behind the simulators and in computer science. A deep understanding of application performance is challenging, as it can vary based on input parameters. Many users end up relying on default configurations or decisions by system administrators for geoscience software, missing opportunities to optimize speed and cost-effectiveness.This thesis aims to shift the paradigm in utilizing HPC for geoscience by entrusting computer architecture decisions to domain-aware optimization algorithms. Such an approach not only enhances usability for the end user, but can also translate into substantial reductions in both time and cost. These algorithms could lead to better utilization of on-premises supercomputers and cost optimization of cloud resources. We evaluate the feasibility of this approach through the contributions of three algorithms. The first algorithm of this work was named TunaOil, which is a novel methodology that uses previous reservoir simulation executions to train an oracle that proposes near-optimal numerical parameters for subsequent simulations within a History Matching (HM) workflow. This allows the simulation parameters to be adjusted without additional executions, saving valuable time. Experiments show that the contribution of this algorithm is an improvement of up to 31% in the overall runtime of the HM workflow.The second algorithm, named MScheduler, is a metascheduler framework designed for reservoir simulations in the cloud. It effi-ciently executes SLURM jobs by utilizing spot Virtual Machines (VMs) to minimize costs and ensure job completion even in the event of VM termination. Key contributions include a novel methodology for reservoir simulation checkpointing, a cost-based scheduler, and an analysis of the strategy using real production jobs. MScheduler significantly reduces financial costs with a slight increase in makespan. On average, it reduces monetary costs by up to 32%, with only an 8% increase in the makespan compared on-demand executions. In the best case, the monetary savings reach 66%, with a 19% increase in makespan.The third algorithm utilizes Machine Learning (ML) algorithms in job schedulers to predict execution times of reservoir job, improving cluster resource efficiency. The developed model classifies the duration time interval of SLURM reservoir simulation jobs with an accuracy of more than 70%, exceeding the standard performance described in the job scheduling literature, thus contributing to improved scheduling decisions.Together, these algorithms mark a paradigm shift in HPC utilization for geoscience applications. They liberate end users from complex computer architecture choices, contributing to improved decision-making and significant time and cost benefits.
  

• HÖSCHELE, JONATAN: A strontium quantum-gas microscope
  
  Author: HÖSCHELE, JONATAN
  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 PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 25/03/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: TARRUELL PELLEGRIN, LETICIA
  Committee:
       PRESIDENT: SCHRECK, FLORIAN EBERHARD
       SECRETARI: DE RIEDMATTEN, HUGUES
       VOCAL: WEITENBERG, CHRISTOF
  Thesis abstract: The development of quantum-gas microscopes has revolutionized the field of quantum simulation with ultracold atoms. More specifically, their ability of direct observation and manipulation of degenerate quantum gases in optical lattices on a single particle level has brought novel ways of probing and engineering quantum degenerate many-body systems. So far, most of these setups have focused on alkali atoms. Combining quantum-gas microscopy with the properties of alkaline-earth atoms such as strontium gives rise to exciting research directions. In this thesis, we report on the design and construction of a strontium quantum-gas microscope. The findings in this thesis can be divided into three parts.In the first part, we focus on the accumulation of atoms in the science cell and develop a scheme to enhance the atom number in magneto-optical traps of strontium atoms operating on the 461-nm transition. This scheme resonantly populates a short-lived reservoir state, partially shielding the atomic cloud from losses in the cooling cycle. We demonstrate a factor of 2 enhancement in the atom number for the bosonic isotopes Sr-88 and Sr-84, and the fermionic isotope Sr-87, showing the efficient capture of these isotopes in our experiment. Our scheme can be readily implemented in the majority of strontium experiments, given that the shielding transition at 689 nm is commonly used for further cooling. In our case, the shielding scheme facilitates the generation of Bose-Einstein condensates.The second part of the thesis reports on the generation of degenerate quantum gases of Sr-84 with up to 200000 atoms. After summarizing the required cooling steps, we study the formation of Bose-Einstein condensates during evaporative cooling in our experiment. Analyzing the evolution of the horizontal and vertical size of our quantum-degenerate clouds in free fall leads to the characteristic asymmetric expansion, which we compare to theory for our experimental parameters. We also show the generation of smaller Bose-Einstein condensates of less than 20000 atoms with the help of a light-sheet potential. With this highly-anisotropic confinement we can consider our Bose-Einstein condensates two-dimensional for atom numbers of the order of 1000.In the third part we demonstrate site-resolved imaging of a Sr-84 bosonic quantum gas in a Hubbard-regime optical lattice potential. We confine the quantum gas by a two-dimensional optical lattice and the aforementioned light-sheet potential, both operating at strontium's clock-magic wavelength. A high-NA imaging objective enables single-atom and single-site resolved fluorescence imaging by scattering photons on strontium's broad 461-nm transition, while performing efficient attractive Sisyphus cooling of the atoms on a narrower transition at 689 nm. We reconstruct the atomic occupation of the lattice sites from the fluorescence images, obtaining imaging fidelities above 94%. Finally, we realize a Sr-84 superfluid in the Bose-Hubbard regime and observe its characteristic interference pattern after free expansion in the light sheet with single-atom resolution. Our strontium quantum-gas microscope provides a new platform to study dissipative Hubbard models and cooperative effects in atom-light interaction at the microscopic level. Moreover, the ability to capture also the fermionic isotope Sr-87 paves the way to generate degenerate Fermi gases with SU(N) symmetry and study SU(N) quantum magnetism.
  

• NARVÁEZ MONTOYA, JOFFRE SANTIAGO: Desarrollo de técnicas acústicas como ensayo no destructivo para evaluar la adherencia de distintos revestimientos arquitectónicos alicatados a su soporte: casos de aplicación.
  
  Author: NARVÁEZ MONTOYA, JOFFRE 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 ARCHITECTURAL, BUILDING CONSTRUCTION AND URBANISM TECHNOLOGY
  Department: Department of Architectural Technology (TA)
  Mode: Normal
  Deposit date: 25/03/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: ZAMORA MESTRE, JOAN LLUIS
  Committee:
       PRESIDENT NO PRESENCIAL: DELGADO MENDEZ, LUIS
       SECRETARI: DIAZ GOMEZ, CESAR
       VOCAL NO PRESENCIAL: CARDENAS HARO, XAVIER RICARDO
  Thesis abstract: The present research is aimed at deepening the evaluation of adhesion in architectural tile coverings in the building sector; despite the improvement of new cementitious adhesives and new ceramic tiles, detachment failures still occur in tile coverings, which can be due to external forces (shocks, earthquakes, vibrations, etc.), inadequate prescription of the cementitious adhesive, incorrect installation, or lack of preparation of the substrate. How to recognize in an inspection the defective state of adhesion of a tiling of this type, in order to prevent detachment?At present, this adhesion is usually evaluated in the laboratory by means of destructive horizontal surface tensile testing systems described in the current regulations on cementitious adhesives. No non-destructive systems have been described for use on site in any layout. The objective of this research is to develop a non-destructive procedure for the evaluation of the state of adhesion of an architectural tiling that is of practical use at the construction site. Several existing alternative techniques, such as thermography or ultrasound, have been considered in the research, but finally it has been decided to focus on the analysis of the acoustic signal obtained by standardized percussion of a tiled tiling on site. This percussion technique has its antecedents in the traditional practice of the experienced architect who manually percussed the tiling with the knuckles of his hand and who, based on his experience, established the lack of adhesion as a defect associated with a "hollow and more vibrant" sound, compared to that of well-bonded tiles. Digital percussion recording analysis is a technique that is already being developed in the field of mechanics to assess the condition of fasteners.The methodology developed in this research is based on successive experimental campaigns in which the PhD student architect has been able to participate, evolving from the understanding of the different vibration phenomena of a free-standing tile depending on the support bonds, through the evaluation of the main vibration frequency of a percussive tiling to the analysis of the correlation between various proposed parameters related to energy, time and their frequency with respect to the values reached in standardized pull-off tests, before and after accelerated aging processes.It is concluded that the results achieved are very promising, although further work is needed to focus on how the acoustic signal emitted by the percussion is modified when it passes through not only the tile and the cementitious adhesive that binds it to the substrate, but especially when it passes through the contact interface between the two.
  

• RIVERA DEÁN, JAVIER: Non-classical states of light: generation via strong-field processes and applications in quantum key distribution
  
  Author: RIVERA DEÁN, JAVIER
  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 PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 25/03/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: ACÍN DAL MASCHIO, ANTONIO | CIAPPINA, MARCELO
  Committee:
       PRESIDENT: KAMINER, IDO
       SECRETARI: DE RIEDMATTEN, HUGUES
       VOCAL: AHUFINGER BRETO, VERÓNICA
  Thesis abstract: The dawn of the last century marked the onset of the first quantum revolution, a period characterized by groundbreaking discoveries culminating in the establishment of quantum mechanics. Over time, the abstract concepts introduced by this new branch of Physics, evolved into indispensable practical devices shaping our daily lives. This technological evolution spurred our actual era, centered around information exchange and acquisition, laying the foundation for what is now termed the second quantum revolution. This phase aims to leverage quantum information science, which harnesses quantum mechanics' properties to propel advancements in information processing, communication, and computation, leading to revolutionary quantum technologies.At the heart of advancing quantum technologies lies the exploration of what are known as non-classical states --physical manifestations exhibiting behaviors diverging from classical physics, necessitating the framework of quantum mechanics for explanation. Manipulating and generating these states delineates the frontier of progress in quantum technology. Therefore, it is crucial to devise methodologies for generating and controlling non-classical states. Photonics emerges as a promising platform within this context due to its robustness and exceptional manageability of this kind of states.For the above reasons, this Thesis adopts a dual focus. Firstly, we delve into the generation of non-classical states of light through strong-field processes. These processes entail interactions between light and matter, where light intensities contend with the binding forces that keep electrons bound to their respective nuclei. Our exploration demonstrates the utility of strong-field phenomena in generating non-classical states of light, exhibiting intriguing features dependent on specific process dynamics and the materials involved in excitation. Secondly, we investigate the constraints and prerequisites of non-classical states of light sources --beyond those derived from the aforementioned strong-field processes-- for the advancement of quantum communication. In particular, we analyze quantum key distribution, aiming to create a secret key exclusively known by the communicating parties for encrypting and decrypting messages.Therefore, this Thesis can be understood as a zeroth step towards leveraging strong-field physics as a prospective tool for quantum information science applications, as well as an exploration about the advances and limitations of photonic-based setups for quantum key distribution.
  

Reading date: 24/04/2024

• FERNÁNDEZ BOSMAN, DAVID: PyMCGPU-IR: a new tool for patient dose monitoring in interventional radiology procedures
  
  Author: FERNÁNDEZ BOSMAN, DAVID
  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 BIOMEDICAL ENGINEERING
  Department: Institute of Energy Technologies (INTE)
  Mode: Normal
  Deposit date: 27/02/2024
  Reading date: 24/04/2024
  Reading time: 11:30
  Reading place: Aula Capella, Escola Tècnica Superior d'Enginyeria Industrial de Barcelona (ETSEIB), Av. Diagonal, 647. 08028 Barcelona
  Thesis director: GINJAUME EGIDO, MERCE | DUCH GUILLEN, MARIA AMOR
  Committee:
       PRESIDENT: SANS MERCE, MARTA
       SECRETARI: SEMPAU ROMA, JOSEP
       VOCAL: SÁNCHEZ CASANUEVA, ROBERTO MARIANO
  Thesis abstract: Interventional radiology procedures are associated with potentially high radiation doses to the skin. The 2013/59/EURATOM Directive establishes that the equipment used for interventional radiology must have a device or a feature informing the practitioner of relevant parameters for assessing patient dose at the end of the procedure. Monte Carlo codes of radiation transport are considered to be one of the most reliable tools available to assess doses. However, they are usually too time consuming for use in clinical practice. This thesis has been developed at the Institute of Energy Technologies of the Universitat Politècnica de Catalunya within the framework of the European project "Implications of Medical Low Dose Radiation Exposure" (MEDIRAD). The main objective of this work is to develop a software tool based on the Monte Carlo program MC-GPU for assessing the skin dose in patients undergoing interventional radiology (IR) procedures. The achievement of this objective can be divided into two main blocks: the validation of MC-GPU and the development and validation of PyMCGPUIR, a skin dose calculation tool for IR procedures based on MC-GPU. For the validation of MC-GPU, simulations were conducted and compared with the well-validated code PENELOPE/penEasy and then compared against thermoluminescent measurements performed on slab phantoms, both in a calibration laboratory and at a hospital. MC-GPU demonstrated excellent agreement in organ dose distribution, with differences below 1%, despite reducing the calculation time by a factor of 2500. Comparisons with thermoluminescent measurements indicated agreements within 10%, validating MC-GPU¿s ability to provide accurate dose estimates in real clinical setups in very short times. In this work we have also developed PyMCGPU-IR, a new software tool based on the Monte Carlo program MC-GPU for assessing skin dose and organ doses in patients undergoing an interventional radiology (IR) procedure. PyMCGPU-IR has been validated through skin and organ dose measurements in an anthropomorphicphantom and showed differences below 6% in skin dose measurements and mostly below 20% in organ doses in clinical procedures. PyMCGPU-IR offers both, high performance and accuracy for dose assessment when compared with skin and organ dose measurements. It also allows the calculation of dose values at specific positions and organs, the dose distribution and the location of the maximum dose per organ. In addition, PyMCGPU-IR overcomes the time limitations of CPU-based MC codes.In this thesis we have shown that PyMCGPU-IR is an innovative Skin Dose Calculation (SDC) tool that offers higher performance and accuracy for skin dose calculations compared to most available SDCs. Currently, PyMCGPU-IR provides dose values only after the procedure has finished. In the future, PyMCGPU-IR could be adapted to provide real-time dose calculation if real-time radiation source information is available.