Author: MACÍAS GARCÍA, ANA ISABEL
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: Confidentiality
Deposit date: 07/09/2022
Reading date: pending
Reading time: pending
Reading place: pending
Thesis director: CABRERA MARRERO, JOSE MARIA | CALVO MUÑOZ, JESSICA
Committee:
     PRESIDENT: GONZÁLEZ REYES, JOSÉ GONZALO
     SECRETARI: MUÑOZ BOLAÑOS, JAIRO ALBERTO
     VOCAL: MERCADO SOLÍS, RAFAEL DAVID
Thesis abstract: In this thesis, the ability to refine the grain size of a low carbon steel (deep drawing quality, DDQ) was studied by means of two different techniques of Severe Plastic Deformation (SPD). Firstly, the Repetitive Corrugated and Straightening (RCS) technique using a die designed for this project. Likewise, a Finite Element Analysis (FEA) was carried out to establish processing routes that would guarantee an optimal distribution of the deformation throughout the entire sheet. The second technique chosen was Calibrated Groove Pressing (CGP), for which a classic die design, with walls to restrict motion in both directions, was chosen. Both processes were carried out at room temperature and with lubricant throughout the process. Two processing routes were established for each of the techniques, reaching different levels of deformation in each of them. To know the mechanical response of the material after being processed, Vickers hardness and tensile tests were carried out. In addition, drawing tests were carried out to know the resulting ability of the material to be shaped. The microstructural characterization was carried out by means of the Electron Backscattered Diffraction (EBSD) technique, to determine the ability to obtain ultrafine grain size, and the strain distribution and texture evolution. The study of mechanical properties revealed the increase in mechanical strength of the material by increasing the deformation, for both techniques. However, the elongation capacity of the material was severely reduced, causing a great loss of drawability in the final material. According to the microstructural results, the evolution of the grain size refinement was observed for each of the different routes and techniques. The grain size reduction depends directly on the increment of the fraction of low and high angle grain boundaries, which varied as the deformation progressed. The morphology, distribution, and grain size, as well as the stored deformation, modified the texture of the material, obtaining intense textures with distributions along the fibers with a shear and lamination texture orientation.

Author: MOHAMMADZADEH, NASIBEH
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 NETWORK ENGINEERING
Department: Department of Network Engineering (ENTEL)
Mode: Normal
Deposit date: 14/09/2022
Reading date: 06/10/2022
Reading time: 10:00
Reading place: ETSETB Aula Màster del C3-005
Thesis director: MUÑOZ TAPIA, JOSE LUIS | NOGOORANI, SADEGH DORRI
Committee:
     PRESIDENT: HERNÁNDEZ GAÑÁN, CARLOS
     SECRETARI: ESPARZA MARTIN, OSCAR
     VOCAL: SILVA CÁRDENAS, CARLOS BERNARDINO
Thesis abstract: Invoice factoring has been a popular way to provide cash flow for businesses. The primary function of a factoring system is to prevent an invoice from being factored twice. In order to prevent double factoring, many factoring ecosystems use one or several centralized entities to register factoring agreements. However, this puts a lot of power in the hands of these centralized entities and makes it difficult for users to dispute situations in which factoring data is unavailable, wrongly recorded or manipulated by negligence or on purpose.This thesis presents our research around the current problems of invoice factoring and our new solutions to solve this process using the blockchain technology. A public blockchain can keep a permanent, secure, ordered and transparent record of transactions which are then available for everyone at any time to view and verify.In this thesis, we start proposing a base solution, and we gradually enhance it. In the base protocol, we propose an architecture for invoicing registration based on a general blockchain. The blockchain platform builds trust between the parties by executing transactions correctly. We employed a smart contract to complete the registration process, and prevent double factoring. The smart contract provides for auditing and dispute resolution in such a way that privacy is protected and relevant information is alwaysavailable.In the second protocol, we add a relayer to our architecture for easier on-boarding. Only the relayer is required to submit blockchaintransactions, and pay the corresponding fees. Other participants can proxy their transactions through the relayer, and pay the relayer in fiat money. We also enhance our identity management and authentication using the concept of verifiable credentials (VC) in order to better comply with the Know-Your-Customer (KYC) regulation. In fact, in this architecture, participants use their decentralized identifiers (DIDs) and the DIDComm protocol for asynchronous and secure off-chain interactions.In the final protocol, we greatly enhance our smart contract with respect to the conditions it checks before registering an invoice factoring. We integrate non-interactive zero-knowledge proofs and cryptographic commitments into our solution. With these cryptographic tools in place, we can prevent a special type of denial of service (DoS) attack and better verify invoice details withoutcompromising privacy. Our protocols are very efficient in terms of blockchain costs. In particular, we only need one transaction to register an invoice factoring, and most of the details are recorded in low-cost blockchain storage. Our evaluations and comparison with the literature reveals that our protocols are superior to the related works with respect to efficiency, security, privacy, and ease ofuse.

Author: CASAMOR VIDAL, MAX
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 NUCLEAR AND IONISING RADIATION ENGINEERING
Department: Department of Physics (FIS)
Mode: Normal
Deposit date: 08/09/2022
Reading date: pending
Reading time: pending
Reading place: pending
Thesis director: FREIXA TERRADAS, JORDI | REVENTOS PUIGJANER, FRANCESC-JOSEP
Committee:
     PRESIDENT: SANCHEZ ESPINOZA, VICTOR HUGO
     SECRETARI: BATET MIRACLE, LLUIS
     VOCAL: AVRAMOVA, MARIA
Thesis abstract: The combined use of thermal-hydraulics system with sub-channel codes (TH-TH coupling) in transient analysis provides an integrated tool with the capability of modelling in detail both the core thermal-hydraulic conditions and the system behaviour. Different code coupling methods are often used in the nuclear industry to provide accuracy to the calculations while maintaining a sufficient degree of usage. In some cases, and for specific scenarios, the coupling method can be simplified to the off-line transfer of the the boundary conditions from plant models run by system codes to sub-channel codes (off-line coupling). The off-line coupling approach has been considered valid to evaluate the safety margins for limiting parameters such as the minimum departure from nucleate boiling ratio, which relates the local power with the critical heat flux. The off-line coupling is fast and sufficiently accurate in most situations, however, boundary conditions at the inlet and at the outlet of both solutions will present miss-matchings. In order to overcome the inconsistencies between system and sub-channel codes, advanced on-line coupling methods may be applied (e. g. semi-implicit coupling). These are methods that imply coherent boundary conditions between codes in all domain and are significantly more complex in mathematical terms. The selection of an appropriate coupling method between system and sub-channel codes is crucial. Recent sensitivity studies performed in sub-channel codes have shown a strong influence of the boundary condition's uncertainty to the major figure of merit. The present study aims to evaluate the implications of the coupling methods in safety analysis evaluations in two transients with strong system effects. For this purpose, CTF (a sub-channel code) and RELAP5 (system code) are coupled using two coupling techniques: the off-line coupling, where the boundary conditions are obtained from the RELAP5 model and imposed by table to CTF, and the semi-implicit coupling method, which has been applied to couple CTF and RELAP5, implementing the semi-implicit coupling methodology developed by Weaver in 2002.The selected cases for the study are a complete loss of forced flow and a pressurizer relief valve opening. The models used are, on one hand, a RELAP5 plant model that consists of a full plant model of a generic Westinghouse 3-loop nuclear power plant. On the other hand, a hybrid assembly sub-channel CTF core model has been developed using the same reference data as the RELAP5 model. In recent years, the application of Best Estimate Plus Uncertainty (BEPU) calculations, has gained importance in the scientific community. This method, far from adding conservatism by forcing non-physical conditions to the calculations, tries to take the uncertainties of the calculations into the process. The BEPU method used in the present study is the GRS BEPU method, which implements Wilks' method using order statistics. BEPU analysis can be considered an additional tool for coupling methods comparisons. Results show that base cases and sensitivity analysis present good agreement between the coupling methods with some minor discrepancies. For the first case, the Spearman's rank correlation coefficients and distributions of the BEPU analysis present similar results for the two approaches. On the contrary, the second case shows differences in the evaluation of the figures of merit, which can be explained and correlated to the boundary conditions deviations between codes. This suggests that non-imposed boundary condition values for the off-line coupling method is an important issue to take into account when applying this type of method for system-dependent transients that are extended in time.

Author: DALLA PORTA DORNELLES, LEONARDO
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: Normal
Deposit date: 26/07/2022
Reading date: 07/10/2022
Reading time: 11:00
Reading place: FIB- Enllaç de la sala de defensa publica en zoom: https://us02web.zoom.us/j/86597459567
Thesis director: SÁNCHEZ VIVES, MARIA VICTORIA | DESTEXHE, ALAIN
Committee:
     PRESIDENT: MATTIA, MAURIZIO
     SECRETARI: MASOLLER, CRISTINA
     VOCAL: MASSIMINI, MARCELLO
Thesis abstract: The brain, a natural adaptive system, can generate a rich dynamic repertoire of spontaneous activity even in the absence of stimulation. The spatiotemporal pattern of this spontaneous activity is determined by the brain state, which can range from highly synchronized to desynchronized states. During slow wave sleep, for example, the cortex operates in synchrony, defined by low-frequency fluctuations, known as slow oscillations (<1Hz). Conversely, during wakefulness, the cortex is characterized mainly by desynchronized activity, where low-frequency fluctuations are suppressed. Thus, an inherent property of the cerebral cortex is to transit between different states characterized by distinct spatiotemporal complexity patterns, varying in a large spectrum between synchronized and desynchronized activity. All these complex emergent patterns are the product of the interaction between tens of billions of neurons endowed with diverse ionic channels with complex biophysical properties. Nevertheless, what are the mechanisms behind these transitions? In this thesis, we sought to understand the mechanisms and properties behind slow oscillations, their modulation and their transitions towards wakefulness by employing experimental data analysis and computational models. We reveal the relevance of specific ionic channels and synaptic properties to maintaining the cortical state and also get out of it, and its spatiotemporal dynamics. Using a mean-field model, we also propose bridging neuronal spiking dynamics to a population description.

Author: OSMAN, MOHAMMED OSMAN
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 NETWORK ENGINEERING
Department: Department of Network Engineering (ENTEL)
Mode: Normal
Deposit date: 18/05/2022
Reading date: 07/10/2022
Reading time: 10:00
Reading place: ETSETB, videoconferència https://meet.google.com/iyk-zmpg-cqh
Thesis director: MANGUES BAFALLUY, JOSEP
Committee:
     PRESIDENT: AGÜERO CALVO, RAMÓN
     SECRETARI: ZOLA, ENRICA VALERIA
     VOCAL: BARANDA HORTIGÜELA, JORGE
Thesis abstract: The SDN (Software-Defined Networks) architecture separates the data and the control planes of the networks. It logically centralizes the control of a network in a central point that is an SDN controller, which acts as a brain of the network and is in charge of telling each network node how to forward incoming packets by installing the appropriate forwarding rules. One of the main advantages it brings is programmability through this single entity (the logical controller) with which network management applications must interact to apply their policies. Through agreed-upon APIs, the network managers can exploit the full potential of SDN.SDN generally assumes ideal control channels between the SDN controller and the network nodes, which may not be the case in challenging environments that are becoming more common due to dense deployment of small cells (SCs) with reduced coverage in 5G and beyond 5G deployments. In 5G and beyond 5G use cases, cost-effective wireless transport networks are required to connect the SCs. In this context, mmWave technology is a good player to connect the SCs as mmWave provides larger radio spectrum chunks that in turn provide larger bandwidth and higher data rate.To manage the dense deployment of SCs in the mobile networks, on the network management/control front, network programmability and virtualization are also an integral part of 5G and beyond 5G networks. In this regard, to provide end-to-end connectivity, management and orchestration of all the segments of the networks ranging from RAN (Radio Access Network), transport network to the core is vital. On the transport networks side (the main focus of the dissertation), SDN plays an important role as SDN enables programmability and virtualization in the network.Though SDN Provides huge flexibility in network management by splitting the control plane from the data plane, it has some limitations in wireless networks context as separation of the control plane from the data plane introduce the extra points of failure in the SDN paradigm (e.g., control communication channel failure, SDN controller failure). In the wide-area networks (WAN) scenarios where in-band channels (e.g., microwave or mmWave links) are responsible to carry control traffic between the forwarding nodes and the SDN controller, the assumption of the availability of a reliable network may not be possible as the performance of the wireless link changes with the environmental conditions, which leads to a high risk of experiencing channel impairments, which might cause centralized SDN operation failure by affecting communication between the transport component of SCs and the SDN controller.To overcome SDN from failure, the dissertation presents a hybrid SDN scheme that explores the benefits of centralized and distributed operations depending on control communication channel conditions. Our hybrid SDN approach combines both centralized and distributed modes in the same node to form a hybrid control plane architecture. We introduce a local agent in the node that is composed of a monitoring framework to detect reliability of the control communication channel and a decision module that conceive a novel control logic switching algorithm to make a decision whether to operate in a centralized or distributed mode. We evaluate the proposed solution under a variety of unreliable network conditions (e.g., link impairments, control packet loss) to investigate the operational performance of the hybrid SDN during high loss conditions. The experimental results show that the proposed hybrid SDN solution substantially improves the aggregated throughput, particularly when control channel packet loss ratios increase, which in turn keeps the network operational in hard conditions where the centralized SDN would result in a non-operational network.