Public display of deposited theses
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DOCTORAL DEGREE IN ARTIFICIAL INTELLIGENCE
- MONTES GOMEZ, MARIA DE LAS NIEVES: Value Engineering for Autonomous AgentsAuthor: MONTES GOMEZ, MARIA DE LAS NIEVES
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 ARTIFICIAL INTELLIGENCE
Department: Department of Computer Science (CS)
Mode: Article-based thesis
Deposit date: 30/11/2023
Deposit END date: 15/12/2023
Thesis director: SIERRA GARCIA, CARLOS | OSMAN, NARDINE
Committee:
PRESIDENT: CORTÉS GARCÍA, CLAUDIO ULISES
SECRETARI: JONKER, CATHOLIJNTJE MARIA
VOCAL: SEVERINO DE ALMEIDA E PAIVA, ANA MARIA
Thesis abstract: The topic of this thesis is the engineering of values for autonomous agents. This is realised through the formulation, design and implementation of new functionalities for autonomous agents that enable reasoning in terms of values. In particular, we argue for the role of prescriptive norms as value-promoting mechanisms. Hence, value-driven agents should be able to autonomously determine which regulations (such as obligations, permissions or prohibitions) make the Multiagent System they inhabit better promote some values of interest. We lay the foundations of our work on Schwartz¿s Theory of Basic Human Values to establish a consequential connection between values and norms, considering that norms are aligned with respect to values if the outcomes they incentivise satisfy the goals that capture the meaning of values in a particular context. Another feature of Schwartz¿s theory that has been previously overlooked in the literature is the strong social dimension of values. That is, agents should be able to reason not just in terms of their own, but also of the values of others in their community. This points to Theory of Mind (i.e. the cognitive ability to perceive, interpret and reason about others in terms of their mental states) as an outstanding component of value-based reasoning.This thesis is structured around three main contributions (published in journal papers) plus their integration. The first contribution establishes the normvalue relationship as a consequential one in nature, and proposes a methodology for the automated synthesis and analysis of optimally value-aligned normative systems. The second contribution tackles the limitations of the first, and defines the Action Situation Language to systematically express a wide range of rules that may be implemented in a Multiagent System. This language is complemented by a game engine that automatically interprets interaction descriptions and builds their semantics as Extensive Form Games, which are later analysed with standard game-theoretical tools. This leads to a distribution over game outcomes, which are evaluated in terms of their desirability with respect to values. The third contribution introduces Theory of Mind-related functionalities into an existing Belief-Desire-Intention agent architecture, and combines them with abductive reasoning capabilities.The three contributions are integrated in a novel functionality that enables agents to reason about prescriptive norms in terms of dynamic values. This means that an autonomous agent can, at runtime, switch its value perspective to the one it estimates that another agent has. Such perspective-dependent value-based normative reasoning functionality, with its inherent social orientation, constitutes a novel contribution to the community of values for autonomous agents and paves the way for possible applications such as value-based negotiation over normative systems. In summary, value engineering is a principled and systematic approach to computational ethics, which provides an innovative tool set for integrating ethical values into the design of autonomous agents.
DOCTORAL DEGREE IN CIVIL ENGINEERING
- BOTEY BASSOLS, JOAN: Exploring the potential of satellite InSAR in Geological Engineering: new opportunities in land monitoring and hydrogeological characterisation.Author: BOTEY BASSOLS, JOAN
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: (DECA)
Mode: Change of supervisor + Article-based thesis
Deposit date: 17/11/2023
Deposit END date: 30/11/2023
Thesis director: VÁZQUEZ SUÑÉ, ENRIC | CROSETTO, MICHELE | GERARD, PIERRE
Committee:
PRESIDENT: GIARDINA, GIORGIA
SECRETARI: HURLIMANN ZIEGLER, MARCEL
VOCAL: ROSSETTO, RUDY
Thesis abstract: Interferometry with Synthetic Aperture Radar (InSAR) is a remote sensing technique to measure displacements of the observed surface, either the ground or any structure on it. Although the systematic acquisition of SAR data from satellites started in the 1990s, InSAR is a technique still in development. The continuous improvement of the successive SAR satellite constellations in terms of reliability, revisit time, spatial resolution and data accessibility, and the processing techniques of SAR data in the estimation of surface displacements is improving the performance of InSAR. Thus, this doctoral thesis aims to explore the new opportunities that InSAR offers today. In particular, the objectives are, first, to explore novel contributions of InSAR in geological engineering, more specifically, in land monitoring and the hydrogeological characterisation of the ground; and, second, to do so while covering both qualitative and quantitative applications at both regional and local scales. These goals are addressed through four questions. The first question aims to investigate whether InSAR¿s spatial resolution and precision are high enough today to monitor ground deformation at such a local scale and in such a changing environment as a construction site. Applied to the ground deformation induced by the dewatering of civil engineering works, InSAR provides a much more complete view and understanding of the observed phenomena than more common alternative techniques such as levelling. However, levelling usually provides more precise measurements. Thus, a combination of both techniques will improve and make the monitoring of civil engineering works more reliable. The second question is whether, because of its spatial data density and its precision, InSAR is suitable for the numerical modelling of extensive ground deformation phenomena. The results achieved thanks to InSAR data in the hydromechanical numerical modelling of regional and long-term ground subsidence related to the overexploitation of confined aquifers prove to be significantly better than the results obtained with other data sources. InSAR data can, first, cover the whole extent of the aquifer system and identify several different deformation phenomena and, second, improve the design of the numerical models and the calibration of the ground parameters, thus achieving a significantly better reproduction and understanding of the observed ground subsidence that enable the design of more adequate and effective policies for land planning and the management of (ground)water resources. The third question turns to a novel InSAR technique: coherence change detection (CCD), a method to detect and map, under certain conditions, changes in the observed surface. In particular, the question is whether InSAR coherence can indeed remotely detect torrential sediment transport events in arid environments. The conclusion is that InSAR coherence is not only able to detect the occurrence of such events but shows a greater detection capacity than the meteorological data, being much more operative and economical than field campaigns. Finally, the fourth question is whether InSAR coherence can remotely map these events, aiming to evaluate the uncertainty that other factors that may also affect InSAR coherence introduce in the CCD maps. The comparison of several mapping methods with different sensitivity to each component of the coherence changes show that CCD methods are able to locate the areas affected by such events, although rugged areas require a thorough analysis and the precise delimitation of the affected areas still presents some uncertainty. All in all, despite the weaknesses that are still to be resolved, InSAR already offers valuable contributions to geological engineering.
- HUANG, DONG: Multi-port container traffic analysis using Data Science tools: an application to Yangtze River Delta (China)Author: HUANG, DONG
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: (DECA)
Mode: Normal
Deposit date: 17/11/2023
Deposit END date: 30/11/2023
Thesis director: GRIFOLL COLLS, MANUEL | ZHENG, PENGJUN
Committee:
PRESIDENT: DUCRUET, CESAR
SECRETARI: ESTRADA ROMEU, MIGUEL ANGEL
VOCAL: MARTÍNEZ MARÍN, JESÚS EZEQUIEL
Thesis abstract: As a crucial node of maritime transportation, seaports carry more than 90% of global trade. Considering the complexity of a port system, even slight improvement at strategical and operational decision levels will lead to a considerable efficiency enhancement. In recent years, the rapid rise of Data Science has sparked a new revolution in the scientific research paradigm, namely data-driven research, which has had a particularly significant impact on the field of complex system research. Therefore, to make more reliable decisions, attention to the Data Science tools used to port traffic has increased noticeably. As one of the most developed regions in China, the Yangtze River Delta multi-port system (YRDP) has caught more and more attention in recent years due to its relevance and the specific economic weight in world trade. Therefore, to insight into the development pattern of YRDP, this thesis first combined the Hierarchical Clustering method with Compositional Data techniques to explore the temporal and spatial evolution of YRDP from 1992 to 2019. A clear port-city dynamic coupling relationship can be an essential asset for port authorities and stakeholders. To explore the dynamic coupling relationship and the inter-lagging effect in a port system, the second part of the thesis proposed a complete framework based on the Auto-Regression Distribute Lag model (ARDL) and ARDL-Error Correction Model (ARDL-ECM), and then the framework is applied in YRDP. The findings indicated that this framework is useful to explore the dynamic coupling relationship and the inter-lagging effects between the port and port city and different ports have different port-city relationships and different inter-lagging effects. Accurate forecasting of container traffic is critical for policymakers and port authorities, especially in the context of anomalous events. (e.g. the COVID-19 pandemic and the 2008 financial crisis). So, the third part of this thesis proposed a hybrid forecasting model based on statistical models and Machine Learning models for container traffic forecasting to enhance prediction accuracy while eliminating the nonlinearity and multivariate limitations. Error metrics analysis suggests that the hybrid models we proposed have better performance compared to other benchmark models. At the same time, this hybrid model can also better predict container traffic in the context of anomalous events. Finally, the results also reveal that, with an increase in the training dataset extensions, the accuracy of the models is improved, particularly in comparison with standard statistical models (i.e. SARIMA model). To resist the challenge of anomalous, the last part of this thesis proposed a method based on the Pearson Correlation Coefficient and Complex Network to explore the co-opetition changes and connectivity and accessibility changes in port systems under the influence of anomalous events. An empirical analysis of the Chinese port system was performed for illustration and verification purposes. The results indicate that: 1) the cooperation between large-scale ports is more intense than that of small-scale ports after the COVID-19 pandemic and lower-intensity competition mainly occurs in the pre-COVID-19 period and high-intensity competition mainly took place in the post-COVID-19 period. 2) the COVID-19 pandemic weakened the connectivity and accessibility of the port. 3) from the perspective of the Chinese port systems, the Pearl River Delta multi-port system (PRDP) has the greatest internal cooperation, YRDP is second to PRDP, and the Bohai Rim port system (BRP) is the last one for both periods. In terms of connectivity and accessibility, the ranking of the Chinese port system is as follows: YRDP, PRDP and BRP. 4) in terms of methodology, we provide a new perspective to explore the co-opetition pattern changes in a port system.
- VAEZI ANZEHA, IMAN: NoProcess understanding of induced seismicity during stimulation of enhanced geothermal systemsAuthor: VAEZI ANZEHA, IMAN
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: (DECA)
Mode: Normal
Deposit date: 22/11/2023
Deposit END date: 05/12/2023
Thesis director: VILARRASA RIAÑO, VÍCTOR
Committee:
PRESIDENT: PEREIRA, JEAN-MICHEL
SECRETARI: VAUNAT, JEAN
VOCAL: CUETO-FELGUEROSO LANDEIRA, LUIS
Thesis abstract: This doctoral thesis investigates the causes that induce (micro)seismicity as a result of hydraulic stimulation in fractured low-permeability rock. Understanding such phenomenon is of paramount importance to eventually forecast induced seismicity in geo-energy applications, like Enhanced Geothermal Systems (EGS). The research is driven by both scholarly and engineering considerations, addressing the intricate coupled hydro-mechanical (HM) processes that are at play and aiming to advance in the understanding of the mechanisms underlying co-seismicity during the hydraulic stimulation phase of EGS. The thesis begins with a comprehensive review of existing modeling methodologies of coupled processes in fractured rock. This exploration highlights the significant advancements these methodologies have brought to the foundational understanding of fractures, ultimately improving predictive capabilities related to coupled processes within fractured systems. The subsequent focus of the research involves an investigation into the flow regimes induced by constant flow rate water injection into a fracture surrounded by a low-permeability matrix. The study sheds light on the implications for hydraulic test interpretation and numerical simulations. The findings reveal that even in very low-permeability confining rock matrix, leakage is non-negligible due to the small fracture aperture, which maximizes pressure gradients across the fracture-matrix interface. The transition between flow regimes, often overlooked in field tests, has important implications for accurately estimating fracture transmissivity in injection tests in fractured media and modeling approaches. The thesis then proposes an innovative approach for the implicit representation of fractures surrounded by low-permeability rock matrix. This approach assimilates fractures as equivalent continua, demonstrating that a relatively thick equivalent continuum layer can accurately represent a fracture and reproduce HM behavior. The proposed method is validated through the modeling of a hydraulic stimulation carried out at the Bedretto Underground Laboratory, showcasing its ability to improve the simplicity and efficacy of continuum methods in representing fractures in fractured media. Finally, the research delves into the modeling of a highly-monitored test at the Bedretto Underground Laboratory to investigate the impact of fluid injection on permeability enhancement and induced microseismicity. Three models are examined, with the viscoplastic fracture with dilatancy and strain-weakening approach emerging as the most comprehensive in capturing the spatio-temporal coupled response of fractured rock to hydraulic stimulation. This model proves effective in estimating the extent of the stimulated fracture, permeability enhancement, and its impact on the local state of stress and pore pressure at surrounding fractures, presenting a valuable tool for the design of effective hydraulic stimulation. In summary, this doctoral thesis contributes to the understanding of micro-seismicity induced by EGS operations, offering insights into coupled processes, flow regimes, and innovative modeling approaches, ultimately advancing the field of geothermal energy research and hydraulic stimulation design.
DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS
- MIR GARCIA, PAU: Singularities and symmetries on the crossroads of geometry and physicsAuthor: MIR GARCIA, PAU
Thesis link: https://atenea-phd.upc.edu/mod/finalthesis/download.php?hash=598504eabf81e20f3fdafed1f196d38442255589
Programme: DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS
Department: Department of Applied Physics (FA)
Mode: Normal
Deposit date: 20/11/2023
Deposit END date: 01/12/2023
Thesis director: MIRANDA GALCERÁN, EVA
Committee:
PRESIDENT: IBORT LATRE, LUIS ALBERTO
SECRETARI: ROMAN ROY, NARCISO
VOCAL: OMS, CEDRIC
Thesis abstract: In this thesis we study several mathematical objects that are essential to formulate and model physical systems. Applying the tools provided by differential geometry, we develop and analyze different mathematical structures that are used in three physical contexts: dissipative dynamics, integrable systems and geometric quantization. To do it, we mainly employ the setting of b-symplectic geometry, a natural extension of symplectic geometry which is specifically designed to address manifolds with boundary. It is based on the concept of b-forms introduced by Melrose and was initiated by Guillemin, Miranda and Pires.Firstly, in the context of dissipative dynamics, we introduce and discuss a variety of twisted b-cotangent models. In these models, defined on the cotangent bundle of a smooth manifold, the fundamental structure is a b-symplectic form that is singular within the fibers of the bundle. Our models give rise to dynamical systems governed by the standard Hamiltonian of a free particle, accompanied by a positiondependent potential. After examining different types of potentials and finding that all of them induce dissipation of energy in the system, we prove that these twisted bcotangent models offer a suitable Hamiltonian formulation for dissipative systems. Consequently, they expand the scope of Hamiltonian dynamics and bring a new approach to the study of non-conservative systems.Secondly, in the context of integrable systems, we introduce and investigate bsemitoric systems, a family of systems that generalizes simultaneously semitoric systems and b-toric systems, and which is tailored for b-symplectic manifolds. We provide a comprehensive definition of b-semitoric systems, that adapts the characteristics of semitoric systems to the framework of b-symplectic manifolds, and we construct three examples of this type of system. The three examples are based on modifications of the coupled angular momenta system, a classical semitoric system that represents the coupling of two rigid rotors. Our examination of the examples, which includes the classification of the singular points and the study of the global dynamics, allows us to highlight the unique characteristics of b-semitoric systems.Thirdly, in the context of geometric quantization, we introduce a Bohr-Sommerfeld quantization method for b-symplectic toric manifolds. We establish that the dimension of this quantization method depends on a signed count of the integer points in the image of the moment map of the toric action. Additionally, we demonstrate its equivalence with the formal geometric quantization of such manifolds. Furthermore, we present a geometric quantization model based on sheaf cohomology, suitable for integrable systems with non-degenerate singularities, that also relies on the count of the integer points in the image of the moment map.
DOCTORAL DEGREE IN MARINE SCIENCES
- FERNÁNDEZ TEJEDOR, MARGARITA: Challenges for shellfish aquaculture in Mediterranean coastal areas.Author: FERNÁNDEZ TEJEDOR, MARGARITA
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 MARINE SCIENCES
Department: (DECA)
Mode: Article-based thesis
Deposit date: 17/11/2023
Deposit END date: 30/11/2023
Thesis director: ESPINO INFANTES, MANUEL | DIOGENE FADINI, JORGE
Committee:
PRESIDENT: CHIRIVELLA MARTORELL, JERONIMO
SECRETARI: GRIFOLL COLLS, MANUEL
VOCAL NO PRESENCIAL: SEBASTIA FRASQUET, MARIA TERESA
Thesis abstract: The increase in the production of marine bivalves targets the sustainable development of aquaculture to improve global food and nutrition security. Bivalve aquaculture is currently facing challenges and threats that are limiting its growth and even its maintenance. Summer marine heat waves produce important mortalities endangering the harvest of the year and the seed of the following harvest. There is a need for expansion to deeper areas less affected by these events. We have developed a methodology to select these areas based on a combination of in situ and remote sensing data to build carrying capacity model for a coastal area in the Western Mediterranean. Harmful algal blooms (HABs) have an impact on bivalve aquaculture through the production of toxins that can accumulate in the bivalves affecting human health, to avoid that, shellfish closures are enforced in areas where toxins are detected over regulatory levels. Direct effects of HABs also threaten bivalve aquaculture producing mortality of farmed bivalves. We have evaluated the risk and trends of HABs in the Mediterranean Sea using bibliographic references and records of HABs events. The results show a low risk of toxic blooms but a higher risk of high biomass blooms without clear trends. Unexplained mortalities of farmed bivalves occur in the Mediterranean Sea, the presence of pathogens alone does not always explain these events. We have detected the presence of Perkinsus olseni for the first time in Mytilus galloprovincialis from the Mediterranean Sea. Warming may stimulate its proliferation, but we cannot conclude that its presence alone was the trigger of the mortality event observed. Translocation of bivalves from other geographical areas may be a risk for the introduction of pathogens and invasive species. In addition, the production of local seed may have other benefits due to bivalve adaptation to local environmental conditions. The replacement of live microalgae diets with artificial diets to simplify hatchery-nursery procedures has been attempted by different teams during the last decades. Artificial diets have been successful for fish and crustaceans but not yet for bivalves. We have tested the efficacy of an artificial diet to feed larvae of Ostrea stentina. Our results show significant differences in the growth and survival of the same larvae feed with live microalgae pointing out that it is not adequate for the hatchery and nursery production of Ostrea stentina larvae. We have addressed various challenges of the bivalve aquaculture in the Mediterranean Sea and have provided tools and evaluations to overcome the limitations and facilitate its development.
DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING
- BABICI, LAURA MARIANA: Fractal Approach to Wheel-Rail Roughness Contact TheoryAuthor: BABICI, LAURA MARIANA
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: Change of supervisor
Deposit date: 22/11/2023
Deposit END date: 05/12/2023
Thesis director: ROMEU GARBI, JORDI | TUDOR, ANDREI
Committee:
PRESIDENT: CHIRIAC, RADU
SECRETARI: PALEU, VIOREL
VOCAL: OLARU, DUMITRU
Thesis abstract: In this study, the Weierstrass fractal function was used to model the surface roughness of railway tracks and, subsequently, the static coefficient of friction (COF) for Hertzian rail-wheel contact and cylinder-plane interactions. This methodology is based on the assumption that the fractal nature of surface roughness can be effectively captured using fractal parameters, which significantly influence the contact mechanics and frictional behaviour observed in railway systems.Initially, the study focused on a detailed modelling of the railway track surface roughness. To validate the efficacy of this model, a rigorous and meticulous comparison between the theoretical results obtained and the experimental data was conducted. These data were collected through extensive roughness measurements carried out at the Faurei Railway Testing Centre in Romania. For robust validation, 41 roughness parameters derived from the fractal model were compared with those measured experimentally. This comprehensive approach allowed not only for the validation of the fractal model but also for its refinement by identifying which parameters are most critical in representing the real roughness of the tracks, as well as the minimum measuring length for determining acoustic roughness.The experimental determination of the static COF was conducted through laboratory tests involving two cylinder-plane specimens, made from the same material as the railway wheel and track. This configuration was chosen to closely replicate the contact conditions found in actual wheel-rail interactions, thus ensuring that the experimental data collected were representative and reliable.To precisely determine the static COF, the stick-slip (SS) process was meticulously characterized by monitoring acoustic emissions (AE), allowing for convenient identification of each phase. The acoustic emissions provided a non-invasive means not only to detect transitions between stick and slip phases but also to understand the underlying mechanisms driving these transitions.This dual approach of theoretical modelling and experimental validation forms the core of this methodology and offers a comprehensive understanding of the frictional phenomena occurring within railway systems, which essential for designing and maintaining safer and more efficient railway operations. The insights gained from this study are expected to significantly contribute to the development of new standards and practices in railway engineering, particularly in areas of wear reduction, noise control, and overall system reliability.The results of this research pave the way for a more nuanced understanding of the fractal nature of contact surfaces and their implications on tribological performance.
DOCTORAL DEGREE IN PHOTONICS
- ALDAMA GUARDIA, JENNIFER DIANA: Toward integrating continuous-variable quantum key distribution technologyAuthor: ALDAMA GUARDIA, JENNIFER DIANA
Thesis link: https://atenea-phd.upc.edu/mod/finalthesis/download.php?hash=b353c7dd471185b13fd16a33cf9c8ccb95c0dd1d
Programme: DOCTORAL DEGREE IN PHOTONICS
Department: Institute of Photonic Sciences (ICFO)
Mode: Normal
Deposit date: 17/11/2023
Deposit END date: 30/11/2023
Thesis director: PRUNERI, VALERIO | ETCHEVERRY CABRERA, SEBASTIAN FELIPE
Committee:
PRESIDENT: SANTOS BLANCO, MARÍA CONCEPCIÓN
SECRETARI: SCHIAVON, MATTEO
VOCAL: ORTIZ MARTIN, LAURA
Thesis abstract: Being able to secure confidential information is imperative in today¿s society, but advancements in quantum technologies pose a potential threat. In response, researchers are developing technologies based on quantum mechanics, such as quantum key distribution (QKD), in particular continuous-variable QKD (CV-QKD), which is emerging as a promising solution due to its compatibility with classical network infrastructures. However, current systems remain bulky and costly, limiting their widespread adoption. To address this challenge, the miniaturization and integration of QKD systems into monolithic photonic integrated circuits (PICs) have the potential to accelerate adoption across a broader market. This is due to the anticipated reductions in size, power consumption, production costs and overall system complexity.This work presents four pulsed Gaussian-modulated coherent state (GMCS) CV-QKD systems based on discrete components and, in the last case, a PIC. The thesis begins with a modular system utilizing discrete components, such as phase and amplitude modulators. Notably, this prototype eliminates the need for phase locking, as the same laser serves as both a local oscillator and the source for generating quantum signals. The system mitigates Rayleigh backscattering by employing two channels, one for transmitting light and the other for transmitting coherent states. Demonstrations indicate its operability over metropolitan distances. In the second approach, the system showcases the parallelization of CV-QKD signals and the coexistence of multiple quantum signals with a classical signal, spatially multiplexed through a multicore fiber (MCF). In this scenario, two lasers are employed, with one emitting the frequency locking signal propagating along one of the MCF¿s core.The third proposal introduces a simplified CV-QKD transmitter (TX) that eliminates the need for a phase modulator in the GMCS generation. This system leverages the random properties of a distributed feedback (DFB) laser operating in the gain-switching (GS) mode. The study demonstrates the applicability of our proposed compact TX for GMCS generation in CV-QKD and its feasibility for integration into a metropolitan network.Finally, we describe and characterize an InP-based PIC TX tailored for CV-QKD applications. System-level proof-of-principle experiments are conducted using a shared laser approach with a pulsed GMCS CV-QKD protocol over an 11 km optical fiber channel. The results indicate potential secret key rates of 52 kbps in the asymptotic regime and 27 kbps in the finite size regime, highlighting the capabilities of the proposed PIC design and, more broadly, the properties of InP technologies for monolithic integration of CV-QKD systems. All the proof-of-principle experiments outlined in this dissertation contribute significantly to the field of miniaturizing CV-QKD systems.
- LOWINSKI, JAN WOJCIECH: Nonlinear optics with a Rydberg ensemble for quantum information processing purposesAuthor: LOWINSKI, JAN WOJCIECH
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: 22/11/2023
Deposit END date: 05/12/2023
Thesis director: DE RIEDMATTEN, HUGUES
Committee:
PRESIDENT: CHANG, DARRICK
SECRETARI: DÜRR, STEPHAN CLAUS
VOCAL: ADAMS, CHARLES STUART
Thesis abstract: Photons have emerged as the main candidates for carrying quantum information due to their weak interaction with the environment. Unfortunately, their limited interaction with one another poses challenges for photonic quantum information processing. One of the possible solutions lies in the unique behavior of interacting Rydberg excitations in cold atomic ensembles, where strong nonlinearities enable engineering interactions among individual photons. This phenomenon makes Rydberg ensembles a promising platform for quantum information applications, notably in long-distance quantum communication. This thesis presents a series of experiments that explore and exploit Rydberg-mediated interactions, all with the long-term objective of building an efficient quantum repeater. The thesis begins with a concise theory overview of Rydberg and ensemble physics. This is followed by an explanation of the experimental setup. I discuss how, building upon a previously existing setup, we improved the stability and spectral properties of our laser system, along with enhancing the quality of the atomic ensemble. The introductory section of the thesis concludes with a description of two different single-photon generation methods and an in-depth review of various decoherence mechanisms impacting Rydberg ensemble excitations. The single-photon generation performance has been improved by the modifications implemented in the setup, resulting in higher generation rates and better single-photon purity. Supported by experimental data and a careful analysis of experimental parameters, we identify the most probable sources of significant decoherence and suggest potential strategies for mitigation. In our initial experiment, we achieve the storage and subsequent retrieval of an on-demand single photon. This photon is generated through the collective excitation of Rydberg states in one cold atomic ensemble, and it is stored in a low-noise Raman quantum memory situated in another cold atomic ensemble. Our results show the capability to store and retrieve these single photons while maintaining a high signal-to-noise ratio of up to 26 and preserving strong antibunching characteristics. We also explore the built-in temporal beam splitting capabilities of the Raman memory and successfully use the memory to control the single photon waveshape. In the second experiment, we demonstrate for the first time an interaction and storage of single photons in a highly non-linear medium based on cold Rydberg atoms. We employ the DLCZ protocol in a cold atomic ensemble to create single photons, guiding them to another ensemble for storage in a highly excited Rydberg state under conditions of electromagnetically induced transparency. By studying the statistics of the light retrieved from the Rydberg atoms, we show for the first time single-photon filtering with non-classical input light. Moreover, through Monte Carlo simulation, we get an intuitive understanding of the effect of the (partial) Rydberg blockade upon the Fock state distribution of arbitrary input light pulses. This allows us to conclude that the response of the medium is determined by the input Fock state distribution, what confirms the established understanding of Rydberg ensemble nonlinearity. This demonstration can be seen as a step towards realization of deterministic photon-photon gates based on Rydberg ensembles with single photon inputs. The results presented in this thesis affirm the potential of Rydberg ensembles to become central elements of future quantum networks, both as single photon sources and processing nodes. Furthermore, auxiliary outcomes provide an additional understanding of the Rydberg ensemble physics and offer insight into limitations that we need to overcome to improve further our setup.
- SALAMON, TYMOTEUSZ PIOTR: Theoretical models for quantum simulators of novel materials and devicesAuthor: SALAMON, TYMOTEUSZ PIOTR
Thesis link: https://atenea-phd.upc.edu/mod/finalthesis/download.php?hash=e140b88eff7a56c20419d653590fc9203e86b4dc
Programme: DOCTORAL DEGREE IN PHOTONICS
Department: Institute of Photonic Sciences (ICFO)
Mode: Normal
Deposit date: 20/11/2023
Deposit END date: 01/12/2023
Thesis director: LEWENSTEIN, MACIEJ | RAKSHIT, DEBRAJ
Committee:
PRESIDENT: RUBIO VERDÚ, CARMEN
SECRETARI: GONZALEZ TUDELA, ALEJANDRO
VOCAL: WEITENBERG, CHRISTOF
Thesis abstract: Over the past three decades, optically trapped ultra-cold atoms have served as a versatile platform for controlled exploration of numerous condensed matter phenomena. The successful fabrication of magic angle twisted bi-layer graphene (MATBG) has introduced a for condensed matter physicists, while concurrently posing a novel challenge for the quantum simulation community. This thesis is devoted to addressing this problem, focusing mainly on the simulation of MATBG structures using ultra-cold atoms within its initial three chapters.To overcome the issue of unit cell expansion resulting from rotation misalignment, in the first chapter we propose the concept of "twist-less twistronics¿ (twistronics, a term coined from twist and electronics). This innovative notion involves replacing the physical rotation of one layer with a light-modulated hopping amplitude between the layers. Enabled by the architecture of ultra-cold atoms, this approach yields quasi-flat bands, a pivotal ingredient for collective phenomena observed in Magic-Angle Twisted Bilayer Graphene (MATBG), achieved at significantly reduced unit cell sizes.The opening chapter also presents a suitable experimental set-up. Moreover, it provides a comprehensive theoretical framework, including tight-binding calculations and effective models derived from perturbative analysis. The second chapter delves into the topological properties of an analogous system, emphasizing the energy separation between the quasi-flat bands and the resulting spectrum. We demonstrate Quantum Anomalous Hall Effect across diverse parameter regimes, accompanied by an exhaustive phase diagram with respect to tunable parameters.In the third chapter, we extend our investigation to encompass onsite, density-density attractive interactions between lattice atoms. Employing the Hartree-Fock-Bogoliubov mean-field approximation, we consider all feasible interaction channels within/between layers and spins. This chapter aims to elucidate the relationship between band flattening, a fully controlled parameter in our system, and the emergence/size of a superconductive gap. Notably, we uncover a substantial enhancement in the critical (Kosterlitz-Thouless) temperature within the quasi-flat band regime at quarter filling, along with a comprehensive diagram illustrating superconducting order parameters corresponding to each interaction channel.The fourth chapter marks a departure from condensed matter simulations, delving into "special purpose quantum computing" within the context of quantum batteries. These devices, analogous to their classical counterparts, store and release energy on demand, a process inherently governed by the battery Hamiltonian. Our work establishes a novel framework for assessing quantum battery performance and setting fundamental bounds on two key attributes: power and capacity. We investigate the essential Hamiltonian terms of a for achieving quantum speed-up in battery charging.The last, fifth chapter describes the theoretical tools, that have been used to support the first experimental realisation of the Extended Bose Hubbard model with dipolar excitons. We discuss the parameters of interests and important observables, such as a structure factor and discuss both the exact diagonalization and mean-field methods, which were necessary to verify the observation of strongly correlated phases at half and unit filling.
DOCTORAL DEGREE IN STATISTICS AND OPERATIONS RESEARCH
- RAMÓN LUMBIERRES, DANIEL JACOBO: Speculation ¿ Postponement strategies in supply chain network design problemsAuthor: RAMÓN LUMBIERRES, DANIEL JACOBO
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 STATISTICS AND OPERATIONS RESEARCH
Department: Department of Statistics and Operations Research (EIO)
Mode: Normal
Deposit date: 22/11/2023
Deposit END date: 05/12/2023
Thesis director: HEREDIA CERVERA, FRANCISCO JAVIER
Committee:
PRESIDENT: ALONSO AYUSO, ANTONIO
SECRETARI: RODRÍGUEZ PEREIRA, JESSICA
VOCAL: PAGÈS BERNAUS, ADELA
Thesis abstract: Speculation and Postponement are opposite supply chain strategies intended to either advance or postpone the necessaryproduction processes to transform raw materials into finished goods. A Customer Order Decoupling Point, or CODP, is alogistic point of the chain where the speculative production is stored until the placement of demand orders, so the CODPpositioning characterizes the associated strategy of the supply chain. Two optimization models are presented to decide theoptimal Supply Chain Network Design and its Speculation ¿ Postponement strategy through a two-stage stochasticoptimization approach: a first one called (OSCS) that assigns strategic and speculation decisions to first-stage variables, andpostponement and recourse values to second-stage variables; and a second one called (OSCST) with the same strategicdecisions as (OSCS) where speculation and postponement concepts are explicitly excluded of the modelling, so allproduction flow decisions are left to second-stage variables. The analysis of a study case of (OSCS) shows clear combinedSpeculation ¿ Postponement strategies for different products joint along with tactical criterions to fulfill demand orders indecreasing order of inventory production added value, as well as significant strategic differences between the originalproblem and its deterministic equivalent. The solutions of the study cases of (OSCST) keep the observed tactical criterionsand show Speculation ¿ Postponement strategies that lay outside of the classical scope. Finally, an extension of theSpeculation ¿ Postponement strategy framework is proposed joint along with two measures, the Absolute and RelativeDegree of Speculation, to quantify the Speculation ¿ Postponement strategy of any supply chain problem with inventory levels.This PhD thesis is the result of a collaboration between GNOM-UPC, Accenture Technology Labs, Accenture AnalyticsInnovation Center and CIM-UPC.
- SALGADO ROJAS, JOSE: MIPing complex multi-action management planning: models, algorithms, and variantsAuthor: SALGADO ROJAS, JOSE
Thesis link: https://atenea-phd.upc.edu/mod/finalthesis/download.php?hash=591a7be8da44831e52d1ea3011d1f42cc340f20d
Programme: DOCTORAL DEGREE IN STATISTICS AND OPERATIONS RESEARCH
Department: Department of Statistics and Operations Research (EIO)
Mode: Normal
Deposit date: 17/11/2023
Deposit END date: 30/11/2023
Thesis director: HERMOSO LOPEZ, VIRGILIO | ÁLVAREZ MIRANDA, EDUARDO
Committee:
PRESIDENT: BLANCO IZQUIERDO, VÍCTOR
SECRETARI: PEREIRA GUDE, JORGE
VOCAL: AQUILUE JUNYENT, NURIA
Thesis abstract: We are living in an era where the complexity of environmental challenges is unprecedented. Biodiversity loss, habitat degradation, and climate change are interconnected issues requiring a comprehensive and multifaceted approach. Conservation planning, a critical component in addressing these challenges, has evolved into a complex task. It requires the consideration of multiple actions, criteria, and spatial dependencies. The urgency of the environmental crisis necessitates effective tools for conservation planning capable of handling this complexity and delivering optimal solutions. This thesis tackles the complexity of spatial conservation planning by developing advanced decision-making tools and addressing computational challenges. It introduces novel contributions through the integration of Mixed Integer Programming (MIP) models, tailored to the Multi-Action Management Planning (MAMP) problem. These models incorporate temporal sequencing (DMAMP), threat spread simulations, and benefit diffusion (Db-MAMP), allowing for realistic and comprehensive conservation planning. Furthermore, the thesis presents the prioriactions package, a user-friendly tool developed using the R programming language. The integration of this package adds a valuable practical component to the thesis, offering users an effective and efficient solution for spatial conservation planning. Overall, this thesis provides valuable insights, novel methodologies, practical tools, and computational advancements that enhance decision-making in complex conservation planning scenarios. The thesis acknowledges the proposed model's limitations and suggests future research directions, ensuring these tools' continued evolution and improvement. It represents a significant stride towards developing more complex decision-making tools in conservation planning. The exploration and application of MIP demonstrate the potential of mathematical modelling in aiding complex decision-making processes. This work contributes to the field of conservation planning by providing a robust and efficient tool for decision-making, paving the way for future research in this area.
DOCTORAL DEGREE IN SUSTAINABILITY
- MOLINS DURAN, GEMMA: Impacte ambiental de la valorització d¿un residu industrial aviari per a l¿obtenció de materials compòsitsAuthor: MOLINS DURAN, GEMMA
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 SUSTAINABILITY
Department: University Research Institute for Sustainability Science and Technology (IS.UPC)
Mode: Normal
Deposit date: 17/11/2023
Deposit END date: 30/11/2023
Thesis director: CARRILLO NAVARRETE, FERNANDO | ÁLVAREZ DEL CASTILLO, MARÍA DOLORES
Committee:
PRESIDENT: SUÑOL MARTÍNEZ, JUAN JOSÉ
SECRETARI: BUSCIO OLIVERA, VALENTINA
VOCAL: PALET BALLÚS, CRISTINA
Thesis abstract: Chicken meat production has increased in recent years and is expected to continue growing, which also increases the generation of waste from the poultry industry. Chicken feathers (PlP) are one of these wastes and solutions are being sought to valorise them. One option is its use in composite materials made with polylactic acid (PLA) with the aim of obtaining a biodegradable plastic material with a low environmental impact. In this thesis, a study of the properties and environmental impacts of this composite material has been performed. For the manufacture of this material, first of all, it is necessary to stabilize the PlPs that leave the slaughterhouse, then they are crushed and finally mixed with the melted PLA to form plates of composite material. In relation to the properties, the tensile mechanical properties, the dimensional stability in water absorption, the density and the compatibility between fiber and matrix have been analysed using FTIR and SEM spectroscopy. The results indicate that the addition of PlP to PLA has little effect on the Young's modulus despite reducing the tensile strength and elongation at break.Spectroscopic analysis shows a weak interaction between fiber and matrix, suggesting that PlPs are a good filler material, but they cannot be considered as a reinforcing material. As for the environmental impacts, they have been studied using the life cycle analysis (LCA) methodology. Firstly, two different processes of stabilization of PlP have been compared, one treatment with steam and another with cationic surfactant. The results allow us to see that stabilization with steam has a smaller impact on the categories studied. Feathers stabilized are crushed and melted together with PLA to form a sheet of material. The results show that the use of PlP in composite materials with PLA can reduce the impact of the material, with the production of PLA contributing the most to the impact, and that the input to the system with the most impacts is the consumption of electricity Although the thesis studies the impact of the material without taking into account the process of raising the chicken, its influence on the impact of the material has been studied, reaching the conclusion that it is not significant.
DOCTORAL DEGREE IN THERMAL ENGINEERING
- ALSALTI BALDELLOU, ÀDEL: Development of linear solvers for large-scale CFD simlations on hybrid supercomputersAuthor: ALSALTI BALDELLOU, ÀDEL
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 THERMAL ENGINEERING
Department: Department of Heat Engines (MMT)
Mode: Normal
Deposit date: 20/11/2023
Deposit END date: 01/12/2023
Thesis director: TRIAS MIQUEL, FRANCESC XAVIER | OLIVA LLENA, ASENSIO
Committee:
PRESIDENT: VERSTAPPEN, ROELAND
SECRETARI: OLIET CASASAYAS, CARLES
VOCAL: VARBANESCU, ANA LUCIA
Thesis abstract: Divergence constraints are present in the governing equations of many physical phenomena, and they usually lead to a Poisson equation whose solution is one of the most challenging parts of scientific simulation codes. Indeed, it is the main bottleneck of incompressible computational fluid dynamics (CFD) simulations, and developing effective Poisson solvers is a critical task.On the other hand, the fact that hardware's memory bandwidth tends to grow much slower than its peak performance has led to strongly memory-bound codes. Additionally, extreme-scale problems have comparable memory requirements, which can become problematic given the faster but smaller memory generally available in massively parallel accelerators. Using more computing resources is a natural way to avoid such limitations and tackle larger problems. However, this generally comes at the price of losing parallel efficiency and is exacerbated by the widening gap between memory and network bandwidths in fat nodes.In this context, this thesis presents a strategy to mitigate several of the challenges above. It consists of exploiting s spatial symmetries to increase the arithmetic intensity of the simulations and reduce their memory requirements. Remarkably enough the proposed strategy is identical regardless of the mesh connectivity (structured or unstructured) and the geometric complexity of the problem, therefore applying to a wide range of academic and industrial configurations.First of all, by proving the existence of an inexpensive block diagonalisation that transforms the original Poisson equation into a set of 2¿^s fully decoupled subsystems, we can accelerate significantly the iterative solvers' convergence. Additionally, imposing an adequate grid points' ordering allows reducing the operators' footprint and replacing the standard sparse matrix-vector product (SpMV) with the more compute-intensive sparse matrix-matrix product (SpMM). Numerical experiments making Algebraic Multigrid (AMG) and preconditioned Krylov subspace methods exploit a varying number of symmetries showed reductions of up to 23% and 72% in the iterations' count, resulting in up to 1.7x and 5.6x overall speedups, respectively.This approach is successfully extended to the preconditioning stage, giving rise to LRCFSAI(k), an enhanced variant of the Factored Sparse Approximate Inverse (FSAI) preconditioner. LRCFSAI(k) arises from introducing another level of approximation by taking advantage of the decoupled subsystems' close similarity to apply the same FSAI to all of them, therefore replacing SpMV with SpMM and leading to notable memory savings and increases in the arithmetic intensity. Of course, recycling the same preconditioner on all the subsystems worsens its convergence. Although being this effect much smaller than expected, it motivated the introduction of relatively cheap but very effective low-rank corrections. A key feature of these corrections is that thanks to being applied to each subsystem independently, the more symmetries being exploited, the more effective they become, leading to up to 5.7x faster convergences than the standard FSAI. Numerical experiments on up to 1.07 billion grids confirm the quality of LRCFSAI(k), which, despite being 2.6x lighter, outperforms the standard FSAI by a factor of up to 4.4x.Finally, the advantages of exploiting symmetries and replacing SpMV with SpMM are extended throughout the simulations. As a result, matrix multiplications are accelerated, whereas their memory footprint is reduced, making massive simulations more affordable. As an example of practical application, we consider the numerical simulation of turbulent incompressible flows using a low-dissipation discretisation of unstructured collocated grids on both CPU and GPU. All the required matrices are classified into three sparsity patterns, showing up to 5.0x speed-ups and 8.0x memory savings.
Last update: 30/11/2023 05:30:26.