Doctoral School

Reading date: 14/05/2024

• AGUILAR MORENO, MIGUEL: Liquid-Liquid membrane contactors for sustainable ammonia recovery and valorization: experimental insights, novel approaches and applications
  
  Author: AGUILAR MORENO, MIGUEL
  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 CHEMICAL PROCESS ENGINEERING
  Department: Department of Chemical Engineering (EQ)
  Mode: Normal
  Deposit date: 16/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CORTINA PALLAS, JOSE LUIS | VALDERRAMA ANGEL, CESAR ALBERTO
  Committee:
       PRESIDENT: DOSTA PARRAS, JOAN
       SECRETARI: GIBERT AGULLO, ORIOL
       VOCAL: REZAKAZEMI, MASHALLAH
  Thesis abstract: This comprehensive research represents a significant stride in the exploration of innovative strategies aimed at enhancing ammonia recovery within diverse wastewater streams. The study is structured into distinct phases, each addressing crucial aspects of the ammonia recovery process. In the initial phase, the research focuses on augmenting membrane contactor performance, employing coagulation-flocculation (C/F) and aeration as preliminary treatments. The outcomes of this phase demonstrate substantial increases in both the mass transfer coefficient and overall efficiency ofammonia recovery, particularly notable when treating the real sidestream centrate. A pivotal finding underscores the efficacy of dosing aluminum sulphate (Al2(SO4)3) at 30 mg Al+/L in the C/F process, yielding remarkable efficiencies in the removal of chemical oxygen demand (COD), turbidity, and total suspended solids (TSS). Into the second phase, the study delves into the sustainable application of liquid-liquid membrane contactors (LLMC) for ammonia recovery. An array of experimental conditions is meticulously explored, with the results illuminating the considerable impact of replacing the acid washing liquid between steps on the overall performance of the LLMC. Additionally, the study highlights the nuanced relationship between the initial ammonia concentration and the subsequent recovery, providing valuable insights. This phase effectively showcases the potential versatility and efficiency of LLMCs in the valorization of ammonia within wastewater streams. The third and final phase introduces a novel asymmetric hollow fiber liquid-liquid membrane contactor (HF-LLMC) with distinctive selectivity for ammonia over water. The investigation entails a comprehensive examination of various operational parameters, including feed and acid flow rates, mass transfer coefficients, and acid consumption. Notably, the results affirm the high selectivity of the HF-LLMC for ammonia, coupled with minimal water transfer. This establishes the HF-LLMC as a promising technology for the recovery and concentration of ammonium in diluted urban and industrial streams. The amalgamation of these findings, approached with a global perspective, significantly contributes not only to the advancement of sustainable nutrient recovery technologies but also underscores their pragmatic feasibility for implementation within the frameworks of the circular economy and efficient resource management.
  

• BISCARO, CATERINA: 3D FEM meso-level analysis of sulphate attack in concrete: new results and developments using parallel HP computing
  
  Author: BISCARO, CATERINA
  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 GEOTECHNICAL ENGINEERING
  Department: (DECA)
  Mode: Change of supervisor
  Deposit date: 16/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: CAROL VILARASAU, IGNACIO | XOTTA, GIOVANNA
  Committee:
       PRESIDENT: SALOMONI, VALENTINA
       SECRETARI: PRAT CATALAN, PERE
       VOCAL: LIAUDAT, JOAQUÍN
       VOCAL: CIANCIO, DANIELA
       VOCAL: MAROTTI DE SCIARRA, FRANCESCO
  Thesis abstract: When concrete is subject to an environment characterised by a high humidity index and rich in sulphate ions, a concrete degradation process may be initiated due to External Sulphate Attack (ESA). The sulphate penetrating into the concrete activates a series of chemical reactions that lead to the formation of secondary ettringite, which may cause non-uniform volumetric expansions that may in turn generate cracking and ultimately culminate in the disintegration of the sample. Because the cracking may in turn facilitate sulphate penetration, ESA may be considered a coupled chemical-mechanical problem. In this study, the numerical analysis of ESA is conducted using the Finite Element Method by considering the specimen at the meso-level composed of larger aggregates embedded in a mortar matrix. Standard continuum finite elements are used to discretise the aggregates and the mortar. Zero-thickness interface elements are inserted along all the aggregate-mortar and selected mortar-mortar contacts to represent potential cracks. The diffusion-reaction of sulphate ions (chemical problem) is formulated following Tixier and Mobasher (2003) and Idiart et al. (2011b). Regarding the mechanical problem, the continuum elements are considered linear elastic, while the interface elements behave according to an elasto-plastic law incorporating concepts of fracture mechanics which was initially developed by Carol et al. (1997) and later extended for 3D analysis by Caballero et al. (2006).The first part of this thesis deals with the verification and use of DRAC5, a completely parallelised version of the in-house code developed within the materials mechanics group (MECMAT) of the Universitat Politècnica de Catalunya (UPC) which now incorporates MPI and PETSC libraries as well as HDF5 i/o files. This new version of the code, which is used to solve both the mechanical problem and the chemical problem through a staggered scheme, has allowed the analysis of new and more challenging 3D studies, producing realistic results that reflect the 'onion peeling' cracking pattern, similar to what has been observed in the laboratory and in previously studied 2D cases (Idiart, 2009). The second part of the thesis, deals with the development of new numerical solving techniques applicable to this type of mesh. In particular, a solution technique based on substructuring and the Schur complement is applied to the analysis of specimens comprising elements of the continuum exhibiting linear elastic behaviour and interface elements characterised by non-linear (elasto-plastic) behaviour. This new technique, which reduces substantially the number of degrees of freedom that need to be considered during the iterative process, has been preliminarily implemented in DRAC4, a simpler series version of the code, and is tested showing great advantages in terms of solution time for a range of 2D application examples. The development of a new formulation using rigid-plastic interfaces is also initiated. This formulation uses relative degrees of freedom at each pair of interface nodes, and leads to the resolution of a Linear Complementarity Problem. This development allows a further reduction in the degrees of freedom of the problem by only considering the nodes of the interface elements involved in the fracture process.
  

• GÓMEZ SÁNCHEZ, GONZALO: Exploring genomic datasets through machine learning methods leveraging high-performance computing
  
  Author: GÓMEZ SÁNCHEZ, GONZALO
  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: 16/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: BERRAL GARCÍA, JOSEP LLUÍS | CARRERA PÉREZ, DAVID
  Committee:
       PRESIDENT: GARCÍA LÓPEZ, PEDRO
       SECRETARI: RUIZ RAMÍREZ, MARC
       VOCAL: CIRILLO, DAVIDE
  Thesis abstract: In recent years, the exponential increase of generated data has raised the need for implementing new methodologies to process the huge datasets being created. High-Performance Computing (HPC) brings together a set of technologies mainly based on parallel computing that help reduce the time expended analyzing these datasets. A research field where these technologies are needed is Computational Genomics. Furthermore, the complexity of the genomic datasets limits the use of basic conventional methods for the discovery of complex significant relations, introducing the need for Machine learning (ML) algorithms and robust statistical methods to better classify these variants. In the first part of the thesis, we aim to identify complex patterns of somatic genomic rearrangements in cancer samples, which are triggered by internal cellular processes and environmental factors. The problem of classification becomes particularly challenging when considering thousands of rearrangements at a time, often composed of multiple DNA breaks, increasing the difficulty in classifying and interpreting them functionally. Here we present a new statistical approach to analyze structural variants (SVs) from 2,392 tumor samples from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium and identify significant recurrence. The proposed methodology is able not only to identify complex patterns of SVs across different cancer types but also to prove them as not random occurrences, identifying a new class of pattern composed of three SVs that was not previously described. In the second part of the thesis, we approach another challenge of human genetics, which is the study of the relation between single nucleotide variants (SNVs) and complex diseases, such as Type 2 Diabetes, Asthma, or Alzheimer's. The study of these disease-variant associations is usually performed in a single independent manner, disregarding the possible effect derived from the interaction between genomic variants. Here, we have created a containerized framework that uses Multifactor Dimensionality Reduction (MDR) to detect combinations of variants associated with Type 2 Diabetes (T2D), called Variant Interaction Analysis (VIA). This methodology has been tested in the Northwestern University NUgene project cohort using a subset of 1,883,192 variant pairs with some degree of association with T2D and identifying a subset of 104 significant pairs, two exhibiting a potential functional relationship with T2D. The developed algorithm has been released in an open-source repository, including the containerized HPC framework, which can be used to search for significant pairwise interactions in other datasets.In both frameworks developed within the thesis, the use of large-scale supercomputing architectures has been a hard requirement to find relevant clinical indicators. To ensure open and broad access to HPC technologies, governments, and academia are pushing toward the introduction of novel computing architectures in large-scale scientific environments. This is the case of RISC-V, an emerging open standard instruction-set architecture. To evaluate such technologies, in the last two parts of the thesis, we propose the use of our VIA use case as a benchmarking, providing the first genomic application for RISC-V. With this use case, we provide a representative case for heavy ETL (Extract, Transform, Load) data processing. We developed a version of the VIA workload for RISC-V and adapted our implementation in x86-based supercomputers (e.g. Marenostrum IV at the Barcelona Supercomputing Center (BSC)) to make a fair comparison with RISC-V, since some technologies are not available there. With this benchmark, we have been able to indicate the challenges and opportunities for the next RISC-V developments and designs to come, from a first comparison between x86 and RISC-V architectures on genomic workload executions over real hardware implementations.
  

Reading date: 15/05/2024

• PAZMIÑO FLORES, YADIRA CARMEN: Evaluación de los usos de suelo y valor ecosistémico del páramo de la Subcuenca Chambo (Ecuador)
  
  Author: PAZMIÑO FLORES, YADIRA CARMEN
  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: 17/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: FELIPE BLANCH, JOSE JUAN DE | VALLBE MUMBRU, MARC
  Committee:
       PRESIDENT: AGUILERA BENAVENTE, FRANCISCO
       SECRETARI: ALCARAZ SENDRA, OLGA
       VOCAL: GUAITA PRADAS, INMACULADA
       VOCAL NO PRESENCIAL: HERNÁNDEZ CLEMENTE, ROCÍO
       VOCAL NO PRESENCIAL: GILABERT NAVARRO, M. DESAMPARADOS
  Thesis abstract: The scarcity of information that allows understanding the importance of natural resources from an economic approach is a limitation to establish parameters related to environmental investment in conservation plans. This research proposes a methodology that allows modeling the variability of páramo land uses and the Ecosystem Valuation (EV) of the Chambo-Ecuador sub-basin from a bioeconomic monitoring that links the economic rent of páramo land uses with remote sensing tools and geographic information systems. The main results of the methodology determined that temporal monitoring of land covers is essential to identify areas of greatest vulnerability to EV degradation. The thresholds, functions and interrelationships determined in the Cart Decision Tree (CDT), Multilayer Perception (MLP), Multivariate Adaptive Regression Splines (MARS) and Support Vector Machines (SVM) models for land cover recognition were efficient; the models performed 88%, 85%, 83% and 81% respectively. The hybridization of the models, Markov chains and cellular automata was appropriate for predicting future land cover changes in Andean areas in relation to their VE, the methods achieved acceptable accuracy for recognizing páramo land uses. The variables chosen for land cover classification were adequate to identify land cover particularities.The opportunity cost and benefit transfer methods proposed obtained a good performance in the evaluation of food production trajectories linked to environmental services (ES) of carbon supply and concentration associated with indirect and support ES, so it was determined that the information from the dynamics of environmental services is an important indicator to understand the real state of the resource and consequently allows understanding the necessary strategies to undertake sustainable actions for ecological management.The mapping generated allowed us to determine that the páramo decreased by 13% between 2000-2010 and 19% between 2010-2020. It was estimated that the loss of the ecosystem between 2000 and 2030 will increase to 28%. From the first year of the study to the last year considered in the work, the páramo will go from occupying 92% to 64% of the area studied. The changes in the EV reveal that the categories with anthropogenic activity analyzed maintain a constant growth that has a direct impact on the EV of the páramo. The most affected areas are those up to 3500 meters above sea level. The EV of the Chambo sub-basin from 2000 to 2020 will increase from 2.86×108 USD to 2.59×108 USD and it is estimated that by 2030 the EV will decrease to 2.48×108 USD, which leads us to recognize that, although the loss of the EV of the natural resource is not critical, its degradation is increasing.Through this methodology it will be possible to obtain, in a practical way, data on the conservation status of the resource over time, allowing to solve problems related to the scarcity of data and leading to the understanding of changes in the area from a socioecological approach, i.e., covering the environmental impacts of human activities on natural systems. The basis of the developed method allows replication of the methodology.The information generated by this study will be of vital importance to understand the causes of the changes in the Andean systems in monetary and environmental terms, which will allow the development of management plans and conservation policies aimed at protection and sustainable management from an economic approach.
  

• PUSAY VILLARROEL, BENJAMÍN ANDRÉS: Fabricación de células solares con absorbedores inorgánicos emergentes y contactos selectivos
  
  Author: PUSAY VILLARROEL, BENJAMÍN ANDRÉS
  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 ELECTRONIC ENGINEERING
  Department: Department of Electronic Engineering (EEL)
  Mode: Normal
  Deposit date: 17/04/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: PUIGDOLLERS GONZALEZ, JOAQUIN | ORTEGA VILLASCLARAS, PABLO RAFAEL
  Committee:
       PRESIDENT: ASENSI LÓPEZ, JOSÉ MIGUEL
       SECRETARI: PLACIDI, MARCEL JOSE
       VOCAL: RIERA LORENTE, SERGI
  Thesis abstract: Silicon is abundant in nature and plays a predominant role in the photovoltaic industry for generating electrical energy. However, the current cost of this solar technology remains high, especially at a commercial level where efficiency reaches 22%. One strategy to reduce the cost of solar energy production involves enhancing the efficiency of solar modules. This can be achieved by integrating new techniques and technologies into the manufacturing processes of the industry, along with the use of abundant and low-toxic materials.Multi-junction solar cells (tandem) enable the integration of two different technologies to leverage their respective qualities as light absorbers, thereby enhancing their electrical performance. Additionally, these cells facilitate the simplification and adoption of new techniques during the manufacturing process. With its Band Gap of 1.1eV, silicon stands out as an excellent candidate for the bottom cell in multijunction or tandem solar cells.The objective of this thesis is to enhance the efficiency of silicon solar cells by utilizing them as multijunction bottom cells to create tandem solar cells. This will be achieved by incorporating a front solar cell based on emerging technologies.To achieve this objective, the introduction is developed, which includes a brief state-of-the-art overview of silicon-based solar cells, the development of tandem solar cells, and the most promising alternatives for emerging inorganic absorbers with adjustable Band Gap, such as kesterites or chalcopyrites (e.g., CuGaSe). The theoretical analysis enables the selection of technologies and processes developed in available laboratories.The application of robust methods for depositing selective contacts in silicon is under investigation. This process aims to prepare the silicon for the thermal and chemical processes involved in the growth of inorganic solar cells, such as kesterites or CGS. This approach enables the development of a robust, efficient, and long-term multijunction solar cell.In a second section, the study on semi-transparent selective contacts for solar cells with inorganic absorbers, such as kesterites or CGS, is presented. The goal is to obtain a compatible substrate for tandem solar cells. As an alternative to traditional CdS for the ETL, we propose the use of Al2O3/TiO2/Mg,i:ZnO layers. Additionally, the potential of enhancing its characteristics by adding polymers (PEI, Glycine) as dipoles is studied.Regarding the hole transport layer (HTL), a semi-transparent alternative to the opaque MoSe2 layers was developed using V2Ox.This layer functions as an interface between the absorber and the transparent electrode (TCO). The incorporation of this layer into kesterite solar cells yielded a semi-transparent device with promising haracteristics, and its application has a significant impact on the efficiency of solar cells.In the last section, a manufacturing process for tandem solar cells is proposed, utilizing Silicon technology as the bottom cell and emerging inorganic solar cells, such as kesterite and CGS, as the top solar cell. Strategies are studied to create a monolithic two-terminal (2T) device, with attention to preserving the physical and electrical characteristics of each device throughout the manufacturing process and during chemical and thermal exposures. Additionally, a study is presented on strategies for the formation of a monolithic device with three interdigitated back contact (IBC) type terminals, which is crucial for obtaining efficient and stable devices in the long term.Through the implementation of these techniques, we anticipate contributing to the research and development of tandem solar cells based on abundant and sustainable materials. This advancement could significantly accelerate the global adoption of solar energy as a clean and renewable source.