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.

Author: MIJAS VÉLEZ, GABRIELA DAYANA
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 TEXTILE AND PAPER ENGINEERING
Department: Department of Textile and Paper Engineering (ETP)
Mode: Temporary seizure
Deposit date: 12/09/2022
Reading date: 10/10/2022
Reading time: 12:00
Reading place: ETSEIAT_ Sala d'actes de l'INTEXTER (Carrer Colom 15, 08222 Terrassa)
Thesis director: RIBA MOLINER, MARTA
Committee:
     PRESIDENT: BONET ARACIL, MARÍA ÁNGELES
     SECRETARI: ARDANUY RASO, MONICA
     VOCAL: MAESTÁ BEZERRA, FABRICIO
Thesis abstract: The main objective of this work has been to obtain fibres and subsequently yarns and fabrics that are suitable for textile applications, through the cottonisation of an agricultural by-product of hemp (Cannabis Sativa L.). The raw material used has come from a non-textile industrial hemp which, so far, is used in the production of oils and sedes and its by-product is also used in the paper industry and in the production of composite materials, but not materials with textile properties. The main problem with hemp, as well as other similar bast fibres, is the high lignin content, which makes it difficult to dry spin using conventional cotton and short fibre spinning techniques. By means of the cottonisation process developed in this study, which has consisted of the application of mechanical, alkaline and oxidising or enzymatic processes, a reduction in the content of non-cellulosic materials has been achieved, including lignin, which has been reduced by 79%. The substrate obtained after the aforementioned processes was blended with cotton in different proportions. Finally, yarns with a count of 40 tex have been obtained through Open-End rotor spinning and then, they were used to produce knitted fabrics. In addition, the substrates resulting have been dyed with natural and sulphurous dyes from natural raw materials to evaluate their behaviour by testing their fastness to different agents. On the other hand, the delignified fibres have been physically and chemically characterised to determine the influence of the alkaline treatment on their final properties. The delignification kinetics of the hemp fibres have also been studied to optimise the process and carry out an industrial scale-up of the process. The results showed that forced convection should be promoted by moving the chemical bath or the material to be treated and that there were no significant differences in the lignin content of the samples treated with NaOH = 0.5M. In this way, it was possible to reduce the amount of alkali initially used by 75%. Based on the results of the kinetics, the alkaline process has been scaled up and for this purpose, a reactor with bath recirculation has been designed and manufactured. This design has allowed the processing of up to 5 kg of hemp, at 80 °C, a temperature lightly lower than those at which these alkaline treatments are usually carried out. The hemp fibres were then treated in two different ways: with an oxidising treatment or with an enzymatic treatment. On the one hand, the fibres that have been treated with an oxidising process have been blended at a 25/75 hemp/cotton ratio to obtain drafter slivers. On the other hand, fibres that have been treated with enzymes have been subsequently blended at a 50/50 hemp/cotton ratio to obtain slivers at laboratory scale. In both cases, it has been possible to spin yarns through Open-End rotor spinning with a 40-tex count and with adequate strength to make knitted fabrics. Finally, the softness of the 50/50 and 25/75 hemp/cotton fabrics has been evaluated, considering a 100% cotton fabric of similar characteristics as a reference. With this, it has been possible to conclude that, in the case of the fabrics with a greater quantity of hemp, an acceptable softness has been obtained despite the high hemp content, and in the second case, the softness has been very similar to that of 100% cotton. This study has determined that, by means of the developed cottonisation process, an agricultural hemp by-product with no initial textile use is susceptible to being spun and knitted, enabling substrates with properties similar to those of cotton to be obtained.

Author: ALAVI, SEYED HAMIDREZA
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 CONSTRUCTION ENGINEERING
Department: (DECA)
Mode: Normal
Deposit date: 14/09/2022
Reading date: 11/10/2022
Reading time: 11:00
Reading place: ETSEIAAT_ Sala de conferències, Edifici TR5, ESEIAAT
Thesis director: FORCADA MATHEU, NURIA
Committee:
     PRESIDENT: POUR RAHIMIAN, FARZAD
     SECRETARI: CASALS CASANOVA, MIQUEL
     VOCAL NO PRESENCIAL: FUERTES CASALS, ALBA
Thesis abstract: A Decision Support System (DSS) can help facility managers to improve building performance, occupants¿ comfort, and energyefficiency during the Operation and Maintenance (O&M) phase. These DSSs are normally data-intensive and have specific datarequirements. Building Information Modeling (BIM) has the potential to advance and transform facilities O&M by providing facilitymanagers with a digitalized virtual environment that allows them to retrieve, analyze, and process such data. However, theimplementation of BIM in O&M phases is still limited. The majority of issues in the BIM-O&M context lie in the interoperability betweendifferent software that requires different data structures and formats. In a BIM environment, there are issues associated withextracting, storing, managing, integrating, and disseminating data so that interoperability is assured.Considering the aforementioned aspects, the aim of this thesis is to enable interoperability between BIM models and the DSSs forbuilding performance aspects such as building condition, maintenance, and occupants¿ comfort. This integration automatizes thedata transfer process which can assist Facility Management (FM) team in properly establishing the necessary measurements tomoderate the negative consequences on buildings and thereby improve their performance and occupants¿ comfort. The approachcan also provide FM teams with an effective platform for data visualization in a user-friendly manner that can assist in integratingdigital insights into FM decision-making processes and converting them into positive strategic actions. The proposed approach isvalidated in existing software as a case study. It is possible to demonstrate the applicability of this approach by ensuring that itsinteractions and outcomes are feasible using case studies. Case studies also identify how much the task efficiencies are incomparison with the manual method, helping facility managers to optimize operation strategies of buildings in order to enhance theirperformance. Verification tests are also performed on the information exported from a software program.The results demonstrate an efficiency increase in high-quality FM data collection for different kinds of DSS, reducing the time andeffort that the FM team spends on searching for information and entering data. A Dynamo script is designed to allow administratorsto include as much information as they wish in BIM models. Moreover, a novel approach is proposed to create a new category in BIMto assist public and business administrations with managing assets efficiently. In addition, building performance aspects can also beanalyzed using the proposed method of integrating occupants' feedback into BIM models. By implementing the proposed approach,FM teams are able to correctly establish measurements which can be applied to mitigate the negative effects on buildings, thusimproving their performance and enhancing their occupants¿ comfort. Besides, the proposed approach enables BIM to be a moreuseful tool for visualization by using the most appropriate charts and formatting.