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Public display of deposited theses

Presentació d'al·legacions a una tesi doctoral en el termini d'exposició pública

In accordance with the Academic Regulations for Doctoral Studies, doctors may request access to a doctoral thesis in deposit for consultation and, if there are, to send to the Permanent Commission of the Doctoral School the observations and allegations that they consider opportune on the content.

 

DOCTORAL DEGREE IN BIOMEDICAL ENGINEERING

  • 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
    Deposit END date: 11/03/2024
    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.

DOCTORAL DEGREE IN BUSINESS ADMINISTRATION AND MANAGEMENT

  • HINOJOSA I RECASENS, JOSEP DOMINGO: Investigación sobre la persistencia, el cambio y la materialidad de la identidad organizacional: entrevistas a expertos y el caso de una empresa centenaria
    Author: HINOJOSA I RECASENS, JOSEP DOMINGO
    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 BUSINESS ADMINISTRATION AND MANAGEMENT
    Department: Department of Management (OE)
    Mode: Normal
    Deposit date: 05/03/2024
    Deposit END date: 18/03/2024
    Thesis director: SUNYER TORRENTS, ALBERT
    Committee:
         PRESIDENT: GARCÍA ÁLVAREZ, MARIA ERCILIA
         SECRETARI: PONS PEREGORT, OLGA
         VOCAL: SELVA OLID, CLARA
    Thesis abstract: ContextThis thesis investigates organizational identity, its persistence and change, and the relationship between identity and material objects. Organizational identity is what the members of an organization answer when they ask themselves: Who are we? and what do we do as an organization?. As a field of research, organizational identity has been gaining relevance in recent decades, especially since the authors Albert and Whetten (1985) established the academic foundations to characterize this concept through the attributes that identity must have: centrality, endurance and differentiation. This characterization was generally accepted by the scientific community and was not questioned for years; it is still considered relevant today. Organizational identity is a broad and complex topic that has been explored by various researchers using qualitative methods. Identity can evolve as organizational practices and narratives are reinterpreted. Some authors consider that identity is dynamic and that it can change as the organization evolves. In this thesis we develop an exploratory research on organizational identity, paying special attention to how identity can adapt, change and be instantiated by material objects. Specifically, this thesis has been structured based on two lines of research: The first line of research studies the persistence of organizational identity and its changes over time, the second line explores the possible relationships between the organizational identity and material artifacts.JustificationThere remains an interesting path to follow in research on organizational identity. Currently, organizational identity is part of the strategic debates and communication plans of many organizations, highlighting the relevance of this concept that can be considered the DNA of an organization. The purpose of this research is to deepen the understanding of organizational identity by exploring how it evolves when the environment changes, when new strategies or different events occur in which identity may face internal or external tensions. Finally, a single in-depth case study is developed exploring the relationships between the identity of an organization and some of its material artifacts.ContributionsThis study has shown that physical objects are part of an identity system that, including other intangible elements, such as verbal communication and narratives, support, instantiate and communicate organizational identity over time. This research results extend the literature on identity, and on the influence and use of material identity objects. The in-depth case study has shown that physical objects has been used to support, instantiate and communicate organizational identity. The data induction process has characterized three different categories of physical objects that provide identity meanings: primal artifacts, identity markers and artifacts created ad hoc.LimitationsThis work provides an exciting opportunity for future research to extend these findings by examining the persistence, change, and materiality of identity in other organizational contexts and industries.

DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS

  • DUAN, YAJUAN: Viscoelastic behavior of high-entropy metallic glasses
    Author: DUAN, YAJUAN
    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 COMPUTATIONAL AND APPLIED PHYSICS
    Department: Department of Physics (FIS)
    Mode: Change of supervisor + Article-based thesis
    Deposit date: 21/02/2024
    Deposit END date: 05/03/2024
    Thesis director: PINEDA SOLER, ELOY | QIAO, JICHAO
    Committee:
         PRESIDENT: CHAZEAU, LAURENT
         SECRETARI: LI, CHUN
         VOCAL: BRUNA ESCUER, PERE
    Thesis abstract: Metallic glasses, especially high-entropy metallic glasses, characterized by their unique microstructure and mechanical properties, provide an effective way for investigating relaxation dynamics and related aspects in the field of glass science. This doctoral thesis focuses on the dynamic and structural heterogeneity of metallic glasses, with an emphasis on high-entropy metallic glasses, unraveling the complex correlation between their microstructural characteristics, thermal behavior, and mechanical properties. The research aims not only to enhance the theoretical understanding of these materials but also to explore novel methods for their modulation and optimization. Firstly, an extensive characterization of dynamic and structural heterogeneity in metallic glasses is studied, with a focused analysis on the connection between ß relaxation and liquid-like zones. This is achieved through a methodical application of stress relaxation and recovery processes, supported by mechanical spectroscopy. This approach reveals a critical temperature-dependent decrease in dynamic heterogeneity and elucidates the complex interplay between ß relaxation, stress relaxation behavior, and the microstructural evolution of liquid-like zones. Through the application of the Kohlrausch-Williams-Watts equation and various other analytical techniques, the study enhances our comprehension of the fundamental properties of metallic glasses, especially in relation to their mechanical response.Furthermore, the modulation of dynamic heterogeneity in metallic glasses is unveiled. This exploration involves a variety of mechanical measurement techniques, each providing unique insights into the physical and mechanical behavior of metallic glasses, especially for high-entropy metallic glasses. Investigations of the internal friction behavior shed light on the influence of microstructural alterations, especially those induced by varying aging temperatures, on energy dissipation mechanisms in metallic glasses. Additionally, the studies through dynamic cyclic loading, creep testing, and stress relaxation measurements provide a more profound understanding of mechanical hysteresis loops and the mechanisms of inelastic deformation. These insights not only broaden the scope of our comprehension of the mechanical behaviors exhibited by metallic glasses but also demonstrate the potential of various mechanical interventions in tailoring their dynamic properties, thereby enhancing their functional efficacy and structural integrity. Finally, the intrinsic correlation between dynamics and thermodynamics in high-entropy metallic glasses is investigated across both super-high and extremely low frequency domains. High-frequency behavior is explored via electromagnetic acoustic transformation (EMAT), elucidating temperature-dependent mechanical responses and atomic-scale structural stability. In contrast, differential scanning calorimetry (DSC) facilitates the analysis of thermal properties at extremely low frequencies, uncovering gradual structural transformations and long-term material stability. This bifurcated frequency approach yields a holistic understanding of the mechanical and thermal dynamics of high-entropy metallic glasses, emphasizing the significance of the probed frequency window in determining their macroscopic properties.Overall, this dissertation contributes substantially to the domain of non-equilibrium physics in glassy materials. The comprehensive analysis and findings of this research provide novel insights into the aging and relaxation dynamics of metallic glasses, enhancing our understanding of these complex materials. The comprehensive analysis and novel findings presented herein have far-reaching implications for the development, optimization, and application of metallic glasses, paving the way for future advancements in their application and functionality

DOCTORAL DEGREE IN MATERIALS SCIENCE AND ENGINEERING

  • ELIZALDE HUITRÓN, SERGIO ALBERTO: Study on the forming limit on shear spinning process
    Author: ELIZALDE HUITRÓN, SERGIO ALBERTO
    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 MATERIALS SCIENCE AND ENGINEERING
    Department: (CEM)
    Mode: Normal
    Deposit date: 27/02/2024
    Deposit END date: 11/03/2024
    Thesis director: CABRERA MARRERO, JOSE MARIA
    Committee:
         PRESIDENT: GARCÍA CANO, IRENE
         SECRETARI: CALVO MUÑOZ, JESICA
         VOCAL: SORGENTE, DONATO
    Thesis abstract: Shear spinning is an incremental sheet metal forming process where a flat metal blank or pre-form is usually converted into an axisymmetric hollow part. Several ductile metals and alloys can be shear formed either at cold and hot conditions, and the most common include steel, aluminum, copper, and nickel alloys. The shape of the shear-formed parts may be conical, concave, convex, or a combination, with wide-ranging applications across industries like aerospace, automotive, and more.The main focus of this research was the study of the forming limit at room temperature in the shear spinning process through experimental trials and finite element simulations. Traditionally, a successful part produced by shear forming is highly dependent on the operator's experience, and usually, the right conditions are found after several trials.The forming limit of any metal forming process is essential data that helps to predict defects appearance in advance, guaranteeing product quality. Accordingly, processing maps to failure were derived for a mild steel DC04, stainless steel AISI 420, precipitation hardening aluminum alloys AA2024 and AA7075, in which the failure limits were found as a function of the thickness reduction, roller attack angle, spindle speed, and feed rate. The experimental findings revealed a convincing relationship between the maximum allowable thickness reduction and the feed rate ratio with the roller nose radius. As the feed rate increased, the maximum allowable thickness reduction exhibited an exponential decrease, described by a parametric equation. Also, it was found that the maximum allowable thickness reduction was 84% for the DC04 and 80% for the rest of the materials.Furthermore, numerical simulations based on the finite element method have been demonstrated as an efficient tool to accurately predict the mechanical response and appearance of defects in metal forming operations. The prediction capabilities of the numerical simulation are based on the evolution of field variables through the operation, i.e., displacements, strain, strain rate, stresses, and ductile damage. Different models of shear spinning were built with the ABAQUS commercial software. First, the efficiency of the different kinematic strategies and solving methods used to model the shear spinning were compared. An efficient segment model was proposed that reduces the computing time up to 300 times compared to conventional models.Further, different uncoupled ductile damage models were implemented via the user materials subroutine (VUMAT). It was found that the ductile damage models can accurately predict failure conditions using a non-linear damage evolution formulation.This research enhances the understanding of material deformation in the shear spinning process and provides a framework for improving operational efficiency in incremental forming processes.

DOCTORAL DEGREE IN STRUCTURAL ANALYSIS

  • JIMÉNEZ REYES, SERGIO: Development of a unified fatigue constitutive model: from high to low cycle regime.
    Author: JIMÉNEZ REYES, SERGIO
    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 STRUCTURAL ANALYSIS
    Department: (DECA)
    Mode: Normal
    Deposit date: 01/03/2024
    Deposit END date: 14/03/2024
    Thesis director: OÑATE IBAÑEZ DE NAVARRA, EUGENIO | BARBU, LUCIA GRATIELA
    Committee:
         PRESIDENT: MARTINEZ GARCIA, JAVIER
         SECRETARI: PEREZ MARTINEZ, MARCO ANTONIO
         VOCAL NO PRESENCIAL: LUCCIONI, BIBIANA MARIA
    Thesis abstract: n a context in which research lines such as optimised design, smart design, use of new materials, weight reduction, etc. are becoming more and more common in the engineering field, techniques that allow for an accurate analysis of the real behaviour of materials, parts and structures are becoming essential. This involves understanding the actual overall response exhibited by a material subjected to a heterogeneous set of external forces, which is only possible by abandoning the reductionist view typically adopted in the design phases in which external forces are amplified, resistance properties are diminished and deterioration phenomena are studied one by one. A clear example of this is the treatment given to the study of fatigue phenomenon, which, in general, is limited to an extrapolation of results obtained in a controlled laboratory environment in order to predict failure, disregarding the process and focusing only on the consequences, thus preventing an integrated study of fatigue with any other inelastic process.Unlike conventional approaches based on simplified analytical calculations or specific numerical models for certain regimes, a unified treatment of fatigue is proposed in this thesis based on plastic-damage constitutive laws. Using the Finite Element method, a framework is built to capture the response of a material exposed to quasi-static loading states in both monotonic and fatigue regimes, resulting in the accumulation of plastic strains and/or stiffness degradation.To reach this point, a study of the individual mechanisms of deterioration encompassed within the unified approach proposed in the thesis is carried out. On the one hand, the characterisation of the constitutive response associated with plastic-damage processes is undertaken. This analysis is carried out by adopting three approaches that involve different levels of coupling in the description of damage and plasticity, resulting in three laws that are further exploited for their potential to be adapted for the study of fatigue processes, yielding to fluctuating plastic-damage models. On the other hand, the characterisation of the behaviour under fatigue loading conditions is addressed by studying the effects that cyclic loads inducing dominant tensile stresses have in a material, including scenarios where the stress level may exceed the yield limit. Having identified the inelastic processes associated with fatigue, the objective methodology is then constructed to coherently study and quantify the successive deterioration mechanisms to which a material may be subjected.This sets the guidelines for further work in the simulation of complex processes involving multiple mechanical deterioration phenomena. Thus, this thesis serves as the first step aimed at: defining the foundations, outlining the applications and initiating the exploration of the potential of the proposed approach.

DOCTORAL DEGREE IN SUSTAINABILITY

  • LI, SHANSHAN: Consumers¿ preferences and willingness to pay towards sustainable food products: Current situation and future perspective in EU and China
    Author: LI, SHANSHAN
    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: Article-based thesis
    Deposit date: 27/02/2024
    Deposit END date: 11/03/2024
    Thesis director: KALLAS CALOT, ZEIN
    Committee:
         PRESIDENT: GIL ROIG, JOSE MARIA
         SECRETARI: BRUGAROLAS MOLLA-BAUZA, MARGARITA MARÍA
         VOCAL: DE MAGISTRIS, TIZIANA
    Thesis abstract: Currently, most of the world¿s agriculture is still based on conventional farming due to its high-yield characteristics, providing food for a growing global consumer population. However, this agricultural system is simultaneously contributing to biodiversity loss and climate change, making it unsustainable for the planet. As consumers are increasingly concerned about the potential environmental and health impacts of food, sustainable agricultural practices are beginning to be explored and developed. Both the European Union (EU) and China are making efforts in this regard. In this context, the overall objective of this dissertation is to explore, from a consumer perspective, the preferences, willingness to pay (WTP), factors affecting WTP for sustainable food products, and sustainable food-related behavior in two distinct regions: the EU and China.Firstly, a meta-analysis of 80 global studies covering a wide range of sustainable attributes was conducted. Subgroup analysis and meta-regression results showed that globally, consumers¿ average WTP premium for sustainable food products in percentage terms was 29.5%. It was worth noting that WTP estimates that were measured by hypothetical methods were typically higher than those by non-hypothetical approaches due to hypothetical bias. In addition, the organic attribute had significantly higher WTP values than other sustainable attributes. The fruit & vegetable category exhibited the highest WTP value, while the seafood category displayed the lowest one. Interestingly, the percentage of WTP for Asia exceeded that of North America and was similar to that of Europe.Secondly, consumers¿ food purchasing and consumption patterns have been reshaped by the global public health crisis (the COVID-19 pandemic). Therefore, the changes of consumers¿ food purchasing and consumption behavior in Spain and China during the COVID-19 lockdown, especially sustainable behavior, were explored. The study conducted in Spain analyzed three main dependent variables: total food consumption, expenditure, and sustainable food purchases. Data were collected from 1,203 respondents through an online semi-structured survey. To examine Chinese consumers¿ sustainable buying and consumption behavior, a semi-structured questionnaire was designed, and data were collected from 1,006 participants. Three dependent variables were measured, i.e., food purchasing behavior on sustainable attributes, sustainable and healthy diets, and food waste. In these two studies, some interesting results were found. Consumers¿ socio-demographic characteristics, emotions, trust in information sources, knowledge of COVID-19, risk attitudes, and risk perceptions played key roles in consumers¿ sustainable food-related behavior during the lockdown.Thirdly, circular farming was studied here as a sustainable agricultural system. Using the Open-Ended Choice Experiment (OECE) methodology, we conducted a questionnaire survey with 5,591 consumers from six EU countries, aiming to explore their WTP and demand for food products produced by circular farming. Three products were focused on: pork, milk, and bread. The study found that there was a demand for food produced by circular agriculture on the European market and that consumers were willing to pay higher prices than for conventional products. Among these six countries, consumers in Spain were willing to pay the highest premium (>26%), while consumers in Hungary exhibited a relatively low WTP for these products. Consumers¿ socio-demographic characteristics, environmental attitudes, and price influenced their purchases of circular food products.This dissertation provides insights for stakeholders. In addition, future research could explore consumers¿ food-related behavior in the current environment and investigate the market potential of the circular food products in China.

Last update: 05/03/2024 05:30:31.