Author: BELOHLAV, VOJTECH
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 ENVIRONMENTAL ENGINEERING
Department: (DECA)
Mode: Change of supervisor
Deposit date: 07/09/2021
Reading date: 20/10/2021
Reading time: 10:00
Reading place: ETSECCPB-https://meet.google.com/txv-wrnu-kch
Thesis director: UGGETTI, ENRICA | JIROUT, TOMAS | KRATKY, LUKAS
Committee:
     PRESIDENT: SKOCILAS, JAN
     SECRETARI: BLANCO AGUILERA, RICARDO
     VOCAL: FEKETE, ROMAN
     VOCAL: ¿ULC, RADEK
     VOCAL: PETERA, KAREL
Thesis abstract: Due to the large volume of the processed medium in pilot or industrial cultivation systems, it is difficult to illuminate the entire layer of the culture medium, which results in the formation of dark zones. Due to insufficient mixing, also an unbalanced utilization of nutrients contained in the culture medium or formation of temperature gradients can occur. Microalgal biofilm formation attached to the transparent walls of closed photobioreactors (PBRs) is also a significan! limitation associated with scaling-up, since it can significantly reduce the intensity of incident light. According to those factors, the hydrodynamic conditions of the culture medium are an importan! parameter in the scaling-up of cultivation systems, since it affects the mixing and the homogeneity of the culture medium. Efficient mixing can: 1) allow all microalgal cells to reach the irradiated area (light zone) of the culture medium; 2) prevent the formation of temperature gradients or sedimentation of microalgal cells; 3) intensify mass transfer resulting in more efficient utilization of nutrients. Moreover, the intensification of flow in the a rea clase to the transparent walls of the cultivation system can also result in an in crease of wall shear stress and a reduction of biofilm formation. The aim of this thesis was to study the influence of hydrodynamic conditions on parameters affecting the production of microalgae in two cultivation systems: a hybrid horizontal tubular photobioreactor (HHT PBR) and a closed flat panel photobioreactor (FP PBR). To this end, a multi-physical model was created to study the effect of hydrodynamic conditions on microalgae cultivation. Based on the experimental measurements, a numerical model simulating the hydrodynamic conditions in transparent HHT PBR tubes was validated. Through the model, the influence of different operating conditions on the mixing of the culture medium were investigated. The developed multi-physical model allowed to investigate the influence of operating conditions on the distribution of light in the culture medium and the production of microalgae, The model showed that, in systems working with a large !ayer of culture medium or a high concentration of microalgae, the intensification of mixing increases the production of microalgae. To do this, the hydrodynamic conditions in the cultivation system should be brought as clase as possible to the state where the entire volume of the culture medium is ideally mixed. This state can be achieved by increasing the flow rate in the tubes or by using static mixers installed in the tubes of the PBR. Hydrodynamics in FP PBR were more complex than in HHT PBR. By comparing the created ydrodynamic model with experimental measurements, the influence of hydrodynamics on the prevention of biofilm formation was specified as well. The created hydrodynamic model allowed to optimize the operating and design parameters of the FP PBR. In arder to intensify the mixing and homogenize the flow of the culture medium in the FP PBR, a static mixer was designed. Compared to the empty FP PBR chamber, the homogenization time was reduced and the homogenous flow in the chamber was ensured by the installed static mixer The multi-physical model developed in this thesis has preved to be an efficient tool to understand the influence of hydrodynamic conditions on microalgae production. Based on experimental measurements and numerical models, the operating conditions of HHT PBR and FP PBR were optimized. To further intensify the mixing and homogenize the flow of the culture medium, a static mixer was designed, which demonstrated a positive effect on the hydrodynamic conditions of the culture system. Overall, the created numerical model is a useful tool to improve existing cultivation systems, to acquire knowledge during the scale-up of cultivation systems or for designing novel PBRs.

Author: DIEZ BLANCO, MARIA TERESA
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 ARCHITECTURAL, CIVIL AND URBAN HERITAGE AND REFURBISHMENT OF EXISTING BUILDINGS
Department: (RA)
Mode: Normal
Deposit date: 21/09/2021
Reading date: pending
Reading time: pending
Reading place: pending
Thesis director: MILLAN GOMEZ, ANTONIO
Committee:
     PRESIDENT: MENDOZA RAMIREZ, HECTOR
     SECRETARI: RINCÓN BORREGO, IVÁN ISRAEL
     VOCAL NO PRESENCIAL: CARRASCO HORTAL, JOSE
Thesis abstract: The Dutch De Stijl group was born at a time of common interest among avant-garde artists and architects of the first half of the 20th century in the purification of the means of expression, based until then on a tradition of imitation: of natural forms in art and ancient styles in architecture. The Neo-Plasticists, however, went beyond a simple formal renovation to generate a new spatial concept, thanks to the influence exerted by the painter Piet Mondrian on the other members of the group. Mondrian conceived painting based on asymmetrical combinations of mutually neutralising planes, something he extended to his idea of architecture. Another significant influence on this paradigm shift was the work of the American architect Frank Lloyd Wright, also based on breaking down the massive, unitary envelope of the traditional dwelling. In this way, the plane was established as the minimum architecture unit, thus achieving continuity and fluidity between spaces, both interior and exterior. This concept, already present in traditional Japanese architecture, continued beyond the Neoplastic movement, leaving a considerable mark on great masters such as Le Corbusier and Mies van der Rohe.Similarly, in the early 1930s, what had been for centuries the traditional solidity and compactness of architecture gave way to a radical change through a 'dematerialised' conception of it. Volume was defined by the sum of independent planes, transparencies, and open corners. Thus, the formal vocabulary of De Stijl became integrated into the International Style, closing that way the circle in its desire to be a universal style. The main objective of this doctoral thesis is, therefore, to analyse the influence of the De Stijl group in architecture, from today's point of view, based on three key concepts for the Dutch movement: colour (i.e. the application and meaning of colour in neoplastic architecture), space (in terms of the generation of a new spatial conception) and style, which gave the group its name (De Stijl means "The Style" in Dutch), intending to assess the survival of some neoplastic trait or vestige in contemporary architecture. Thus, we find the work of the Finnish architect Juha Leiviskä, generated from compositions of orthogonal planes that delimit areas and which in turn are blurred through the use of natural light, as well as several designs by the architect Steven Holl, also based on a reading of space starting from planes and the application of colour as an architectural resource. All this makes it possible to establish analogies with Neoplasticism, thus reflecting a symbiosis of ideas, of which Rafael Moneo's Museum of Roman Art in Mérida is also an example. Therefore, the main conclusion to be drawn is that De Stijl's architectural proposals are still valid today, albeit as formal references, as they are applied outside the meaning and theoretical content they had for this avant-garde movement. To this end, a comparative case study has been carried out, based on the analysis of the architectures ¿starting from shared spatial concepts- and complemented with the writings and statements of their main actors.

Author: HESP, NIELS CASPAR HERMAN
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: 16/09/2021
Reading date: 20/10/2021
Reading time: 15:30
Reading place: ICFO ¿ The Institute of Photonic Sciences - Campus Baix Llobregat - Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona) - SPAIN
Thesis director: KOPPENS, FRANK
Committee:
     PRESIDENT: POLINI, MARCO
     SECRETARI: PAPADAKI, GEORGIA
     VOCAL: BASOV, DMITRI
Thesis abstract: Nano-optics studies the behaviour of light on the nanoscale. In particular, it probes the interaction of light with objects, often of nanometre-size, and reveals fine details of the material's optical properties. Optoelectronics is an integral part of optics and describes the interaction between light and electronics, such as the detection of light and subsequent conversion to an electrical signal. Understanding such mechanisms at the nanoscale is of importance for improving imaging and light-harvesting applications. In this Thesis, we apply near-field microscopy to study optics on the nanoscale. It probes optical properties using light interacting with the near-field electromagnetic field near the material's surface.Twisted bilayer graphene (TBG) is formed by stacking two layers of graphene - a one-atom-thick sheet of carbon atoms - with a small twist angle. This causes an interference pattern in the atomic lattice called a moiré pattern, which affects the electronic properties dramatically.The discovery of unconventional superconductivity in TBG in 2018 made it a thriving field of research. Adding to this, TBG revealed strongly correlating states and topological features, making it a host of tunable exotic phases that may shed light on the origins of unconventional superconductivity. These phenomena motivate us to study the optical properties of TBG on a nanoscale, which have received little attention thus far.In the first part of this Thesis, I describe spatially oscillating patterns within selected regions of TBG that we detected using near-field microscopy. We interpret them as a manifestation of plasmons --- electrons moving collectively in a wave-like pattern --- driven by interband transitions. We model these areas with a reduced interlayer coupling, which enhances the strength of interband transitions and explains the observed plasmon dispersion. After this, I discuss large-scale periodic features observed in minimally twisted bilayer graphene (¿ < 0.1 deg) by photocurent nanoscopy. For these small twist angles, the atoms rearrange in triangular domains separated by a network of domain walls. We find that the domain walls convert heat injected in the domains into a measurable current via the photothermoelectric effect. Our results uncover the sharp changes in electronic properties at the domain walls, which govern the optoelectronic response.I focus in the second part of the Thesis on the development of new experimental techniques, which enable nano-optical studies on exotic states of TBG and its relatives. I show that the semiconducting material WSe2 can be used as an ambipolar transparent top gate for infrared near-field experiments. This enables full control of the carrier density and transverse displacement field without blocking near-field access.Hereafter, I describe a commercial cryogenic near-field microscope with a base temperature of 10 K, which required modifications for reliable operation. I present an active damping system to oppose the vibrations in the system and enhance the mechanical stability. We further improve the AFM stability by changing the AFM excitation position.In the final two Chapters I examine the photoresponse of TBG at low temperature. We observe semi-periodic modulations across our sample, which we believe manifests a second-order superlattice arising from TBG aligned to the hBN substrate in combination with strain. In a different sample, we reveal a spatially inhomogeneous response from which we deduce a map of the local twist angle.

Author: BARANDA HORTIGÜELA, JORGE
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: 22/09/2021
Reading date: pending
Reading time: pending
Reading place: pending
Thesis director: MANGUES BAFALLUY, JOSEP
Committee:
     PRESIDENT: MASIP BRUIN, JAVIER
     SECRETARI: SERRANO YÁNEZ-MINGOT, PABLO
     VOCAL NO PRESENCIAL: YOUSAF, FAQIR ZARRAR
Thesis abstract: 5G marks the beginning of a deep revolution in the mobile network ecosystem, transitioning to a network of services to satisfy the demands of new players, the vertical industries. This revolution implies a redesign of the overall mobile network architecture where complexity, heterogeneity, dynamicity, and flexibility will be the rule. Under such context, automation and programmability are essential to support this vision and overcome current rigid network operation processes. Software Defined Networking (SDN), Network Function Virtualization (NFV) and Network slicing are key enabling techniques to provide such capabilities. They are complementary, but they are still in its infancy and the synergies between them must be exploited to realise the mentioned vision. The aim of this thesis is to further contribute to its development and integration in next generation mobile networks by designing an end-to-end (E2E) network service orchestration (NSO) architecture, which aligned with some guidelines and specifications provided by main standardization bodies, goes beyond current management and orchestration (MANO) platforms to fulfil network service lifetime requirements in heterogeneous multi-technology/administrative network infrastructures shared by concurrent instances of diverse network services.Following a bottom-up approach, we start studying some SDN aspects related to the management of wireless network elements and its integration into hierarchical control architectures orchestrating networking resources in a multi-technology (wireless, optical, packet) infrastructure. Then, this work is integrated in an infrastructure manager module executing the joint resource abstraction and allocation of network and compute resources in distributed points of presence (PoPs) connected by a transport network, aspect which is not (or lightly) handled by current MANO platforms. This is the module where the integration between NFV and SDN techniques is executed. This integration is commanded by a Service Orchestrator module, in charge of automating the E2E lifecycle management of network services implementing network slices (NS) based on the vertical requirements, the available infrastructure resources, and, while fulfilling service level agreement (SLA) also during run-time operation. This architecture, focused on single administrative domain (AD) scenarios, constitutes the first group of contributions of this thesis.The second group of contributions evolves this initial architecture to deal with the orchestration and sharing of NS and its network slice subnet instances (NSSIs) involving multiple ADs. The main differential aspect with current state-of-the-art solutions is the consideration of resource orchestration aspects during the whole orchestration process. This is fundamental to achieve the interconnection of NSSIs, hence making the E2E multi-domain orchestration and network slicing a reality in practice. Additionally, this work also considers SLA management aspects by means of scaling actions during run-time operation in such complex scenarios. The third group of contributions demonstrate the validity and applicability of the resulting architectures, workflows, and interfaces by implementing and evaluating them in real experimental infrastructures featuring multiple ADs and transport technologies interconnecting distributed computing PoPs. The performed experimentation considers network service definitions close to real vertical use cases, namely automotive and eHealth, which help bridging the gap between network providers and vertical industries stakeholders. Experimental results show that network service creation and scaling times in the order of minutes can be achieved for single and multi-AD scenarios, in line with 5G network targets. Moreover, these measurements serve as a reference for benchmarking the different operations involved during the network service deployment. Such analysis are limited in current literature.

Author: LÓPEZ RUIZ, LUIS 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 ENVIRONMENTAL ENGINEERING
Department: (DECA)
Mode: Normal
Deposit date: 22/09/2021
Reading date: pending
Reading time: pending
Reading place: pending
Thesis director: ROCA RAMON, XAVIER | GASSO DOMINGO, SANTIAGO
Committee:
     PRESIDENT: BOVEA EDO, MARÍA DOLORES
     SECRETARI: ÁLVAREZ DEL CASTILLO, MARÍA DOLORES
     VOCAL: PUIG VIDAL, RITA
Thesis abstract: Construction and demolition waste (CDW) is a major environmental concern that requires immediate attention. The large volumes of CDW produced and its associated environmental effects have led to explore new alternatives addressing this problem in more sustainable ways. In this context, the Circular Economy (CE) paradigm emerged as an innovative solution for creating more sustainable production and consumption patterns, fostering economic growth, and providing environmental protection and social welfare. At the global level, the concept of CE has gained increasing interest from government bodies, business organizations and academics. This has resulted in multiple political agendas including CE as a core driver, as well as an emerging trend of research exploring its concept and applications. However, because of the novelty and dynamism of the concept, research developments on practical applications and quantitative assessments are at an early stage. The main aim of this study was to propose an approach to integrate the CE concept in the construction and demolition sector, as well as providing the basis for evaluating the environmental and economic effects of circularity strategies and to monitor their implementation. For this purpose, an integrative framework of strategies for CE adoption in the CDW sector is proposed. This together with a methodological proposal to evaluate and compare the environmental and economic performance of different circularity alternatives incorporating multi-criteria decision analysis. In addition, this work proposes a system of indicators for measuring CE features for CDW products. The proposed framework identifies 14 influential strategies for the circularity of the CDW sector and describes their interaction throughout its lifecycle stages. The methodological proposal incorporates the Life Cycle Analysis (LCA) methodology to assess the environmental dimension., while the economic criteria adopt a complex cost method. The multicriteria VIKOR method was used to perform the multi-criteria analysis. The methodology is applied to evaluate the use of concrete waste in high-grade applications, specifically the production of structural and non-structural concrete mixes in the region of Catalonia, Spain. The indicators framework incorporates a systematic approach considering the most relevant factors and parameters for successful measurement of CE interventions. It consists of 22 measures within the three dimensions of environment, economic and innovation/materials. Preconstruction strategies are highlighted as the most influential in the circularity of the sector. CE strategies presented better environmental and economic performance; however, results are conditioned by the particular context of the study. Transportation and landfilling are identified as the most conditioning parameters affecting both environmental and economic performance.