Yes / This article presents a unique technique to enhance isolation between transmit/receive radiating elements in densely packed array antenna by embedding a metamaterial (MTM) electromagnetic bandgap (EMBG) structure in the space between the radiating elements to suppress surface currents that would otherwise contribute towards mutual coupling between the array elements. The proposed MTM-EMBG structure is a cross-shaped microstrip transmission line on which are imprinted two outward facing E-shaped slits. Unlike other MTM structures there is no short-circuit grounding using via-holes. With this approach, the maximum measured mutual coupling achieved is -60 dB @ 9.18 GHz between the transmit patches (#1 & #2) and receive patches (#3 & #4) in a four-element array antenna. Across the antenna’s measured operating frequency range of 9.12 to 9.96 GHz, the minimum measured isolation between each element of the array is 34.2 dB @ 9.48 GHz, and there is no degradation in radiation patterns. The average measured isolation over this frequency range is 47 dB. The results presented confirm the proposed technique is suitable in applications such as synthetic aperture radar (SAR) and multiple-input multiple-output (MIMO) systems. / H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E0/22936/1

Subduction is a dynamic and time-dependent process which requires time-dependent models for its study. In addition, due to the very high pressures within the Earth's interior, an evaluation of the role of compressibility in subduction studies should be undertaken. However, most subduction studies have been conducted by using kinematic, steady-state, and/or incompressible mantle convection models; these simplifications may miss important elements of the subduction process. In this dissertation, I evaluate the effects of time-dependence and compressibility on the evolution of subduction by using 2-D Cartesian numerical models. The effect of compressibility on the thermal and flow structures of subduction zones is evaluated by using kinematically prescribed slab and steady-state models. The effect of compressibility is primarily expressed as an additional heat source created by viscous dissipation. The heat results in thinner thermal boundary layer on the subducting slab and increases slab temperatures. With that exception, the effect of compressibility is relatively small compared with, for example, the effect of the mantle rheology on the thermal and flow structures of the mantle wedge. Plate reconstruction models show that the convergence rate and age of the incoming plate to trench vary with time, which poses a problem for steady-state subduction models. Thus, I consider the time-dependent convergence rate and age of the incoming plate in the kinematic-dynamic subduction models in order to understand the localization of high-Mg# andesites in the western Aleutians. The results show that the localization of high-Mg# andesites is a consequence of the time-dependent convergence rate and slab age along the Aleutian arc. The influence of mantle and slab parameters as well as compressibility on the slab dynamics is evaluated by using 2-D dynamic subduction models. The results demonstrate that periodic slab buckling in the mantle results in periodic convergence rate and dip of the subducting slab; time-dependence is a natural expression of subduction. The effect of compressibility on the slab dynamics is not significant. The periodic convergence rate and dip of the subducting slab explain time-dependent seafloor spreading at the mid-ocean ridge, convergence rate of the oceanic plate at trench and arc-normal migration of arc volcanoes. / Ph. D.

Within the EU's railway research program IN2TRACK3, a product known as the 3MB track system (Moulded Multi Modular Block slab track system) has been developed. The new innovative track system can be explained as a hybrid solution between traditional ballast tracks and slab track systems. The project has a primary objective for the 3MB system to reduce life cycle costs, improve reliability and punctuality, and increase capacity. The modular construction system allows for easier maintenance of railway tracks, as damaged parts can be replaced more quickly. In September 2022, a full-scale test was initiated on a 50-meter stretch in Gransjö, north of Boden, situated along the Iron Ore Line (Malmbana). Initially planned for a 2-year testing period, but the track system was dismantled and removed after approximately one year due to the emergence of a recurring severe crack pattern within the blocks. This degree project aims to conduct a thorough damage investigation, focusing on investigation the reasons behind the repeated crack patterns observed in the 3MB system. The analysis will particularly emphasise the design of the reinforcement and assesses whether the chosen concrete type is suitable for the specific conditions of the construction. Various laboratory tests, including compressive strength, tensile strength, and thin section analysis, are employed in this investigation. Additionally, a comprehensive literature study is conducted to ensure its credibility and quality. The results reveal that the aggregate in the sample is porous. This porosity increases the risk of frost damage and cracking in the concrete. The air content was measured at 7.1%, which is somewhat high, together with a high w/c equivalent between 0.50 and 0.55, which has a potentially negative impact on the strength. The study's in-depth analysis of the 3MB system blocks revealed two main problems: the choice of porous limestone as aggregate and insufficient coverage of the reinforcing steel. The porous nature of limestone led to water absorption and frost susceptibility, while inadequate coverage resulted in corrosion and frost cracking. Laboratory experiments also showed low tensile strength and uneven concrete quality. Calculations indicated the need for spalling reinforcement. Workmanship errors, including haphazard concrete pouring and suboptimal rail fastening solutions, exacerbated the situation. The study highlights the need for improvements in the concrete's waterproofing and fatigue strength to meet the system's requirements and avoid similar problems in the future. Despite the challenges, the project presents potential for success with the right adjustments and lessons learned from the initial testing phase. Despite challenges and identified obstacles in the project, the 3MB system can succeed. By fine-tuning the concrete recipe, and optimizing reinforcement and aggregate quality, the problems can be avoided. It is crucial to look beyond these obstacles and stick to the overall goal of the project: to establish the sustainable and efficient railways of the future. These challenges can be overcome through careful measures and ensure the project's positive contribution to the transport sector. / Inom EU:s järnvägsforskningsprogram IN2TRACK3 har en produkt känt som 3MB spårsystem (Moulded Multi Modular Block slab track system) utvecklats. Det nya innovativa spårsystemet kan förklaras som en hybridlösning mellan traditionella ballastbanor och ballastfria banor. Projektet har som primärt mål för 3MB-systemet att minska livscykelkostnaderna, förbättra tillförlitlighet och punktlighet, och öka kapaciteten. Det modulära byggsystemet möjliggör enklare underhåll av järnvägasspår, eftersom skadade delar kan bytas ut på ett snabbare sätt. I september 2022 inleddes ett fullskaleprov på en 50 meter lång sträcka i Gransjö, norr om Boden, belägen längs Malmbanan. Ursprungligen planerad för en 2-årig testperiod, men spårsystemet demonterades och togs bort efter cirka 1 år på grund av uppkomsten av ett återkommande allvarligt sprickmönster inom blocken. Målet med detta examensarbete är att genomföra en grundlig skadeutredning, med fokus på att undersöka orsakerna bakom de upprepade sprickmönster som observerats i 3MB-systemet. Analysen betonar särskilt dimensioneringen av armeringen och bedömning om den valda betongtypen är lämplig för konstruktionens specifika förutsättningar. Olika laboratorietester, inklusive tryckhållfasthet, draghållfasthet och tunnslipsanalys, används i undersökningen. Dessutom genomförs en omfattande litteraturstudie för att säkerställa studiens trovärdighet och kvalitet. Resultaten avslöjar att ballasten i provet är porös. Denna porositet ökar risken för frostskador och sprickbildning i betongen. Lufthalten uppmättes till 7,1%, Vilket är något högt, och tillsammans med ett högt vatten-cement-tal mellan 0,50 och 0,55, ger de en potentiellt negativ påverkan på hållfastheten. Studiens djupgående analys av 3MB-systemet block avslöjade två huvudproblem: valet av porös kalksten som aggregat och otillräcklig täckning av armeringsstålet. Kalkstenens porösa natur ledde till vattenabsorption och frostkänslighet, medan otillräcklig täckning resulterade i korrosion och frostsprickor. Laboratorieexperiment visade också på låg draghållfasthet och ojämn betongkvalitet. Beräkningar indikerade behovet av spjälkningsarmering. Utförandefel, inklusive ej fullgod betonggjutning och suboptimala rälbefästnings-lösningar, förvärrade situationen. Studien framhåller behovet av förbättringar i betongens vattentäthet och utmattninghållfasthet för att möta systemets krav och undvika liknande problem i framtiden. Trots dessa utmaningar har projektet en potential att bli framgångsrikt med rätt justeringar och lärdomar från den initiala testfasen. Trots utmaningar och identifierade hinder i projektet kan 3MB-systemet lyckas. Genom att finjustera betongreceptet, optimera armeringen och ballastkvaliteten bör uppkomna problemen undvikas. Det är avgörande att se bortom dessa hinder och hålla fast vid projektets övergripande mål: att etablera framtidens hållbara och effektiva järnvägar. Genom noggranna åtgärder kan dessa utmaningar övervinnas och säkerställa projektets positiva bidrag till transportsektorn.

Cuenca Asensio, E. (2012). ON SHEAR BEHAVIOR OF STRUCTURAL ELEMENTS MADE OF STEEL FIBER REINFORCED CONCRETE [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18326

No / Gas chromatography–mass spectrometry (GC–MS) and bulk carbon isotope determinations have been performed on samples (‘cemented organic residues’, charcoal, sediment and fire-cracked rock) excavated from 12 slab-lined pits from various locations in Arctic Norway to test the premise that these archaeological features were used for the extraction of oil from the blubber of marine mammals, such as seal, whale and walrus. A wide range of lipid compound classes were detected especially in the cemented organic residues and in the charcoal samples. The presence of long-chain unsaturated and isoprenoid fatty acids together with oxidation and thermal alteration products of unsaturated acids such as dicarboxylic acids, dihydroxyfatty acids and ω-(o-alkylphenyl)alkanoic acids suggests that these features were used for marine oil extraction at elevated temperatures. Notably the location of the hydroxyl groups in the dihydroxyfatty acids provides a record of the positional isomer of the precursor fatty acid and allows confirmation that 11-docosenoic (cetoleic) acid, the most abundant C22:1 isomer in marine oil, was a major component of the original lipid. Further information was provided by the presence of long-chain fatty acyl moieties in surviving triacylglycerols and the presence of cholesterol. A fungal metabolite, mycose (trehalose), was found in all samples apart from a fire-cracked rock and points to microbiological activity in the pits. Bulk isotope analysis conducted on the ‘cemented organic residues’ is consistent with modern reference samples of blubber and oil from seal and whale. These data provide clear analytical evidence of the function of slab-lined pits in the archaeological record and suggest widespread exploitation of marine mammals for producing oil for heating, lighting and myriad other uses in the past.

Neste trabalho estudam-se alguns novos métodos de seleção de variáveis no contexto da regressão linear que surgiram nos últimos 15 anos, especificamente o LARS - Least Angle Regression, o NAMS - Noise Addition Model Selection, a Razão de Falsa Seleção - RFS (FSR em inglês), o LASSO Bayesiano e o Spike-and-Slab LASSO. A metodologia foi a análise e comparação dos métodos estudados e aplicações. Após esse estudo, realizam-se aplicações em bases de dados reais e um estudo de simulação, em que todos os métodos se mostraram promissores, com os métodos Bayesianos apresentando os melhores resultados. / In this work, some new variable selection methods that have appeared in the last 15 years in the context of linear regression are studied, specifically the LARS - Least Angle Regression, the NAMS - Noise Addition Model Selection, the False Selection Rate - FSR, the Bayesian LASSO and the Spike-and-Slab LASSO. The methodology was the analysis and comparison of the studied methods. After this study, applications to real data bases are made, as well as a simulation study, in which all methods are shown to be promising, with the Bayesian methods showing the best results.

Neste trabalho estudam-se alguns novos métodos de seleção de variáveis no contexto da regressão linear que surgiram nos últimos 15 anos, especificamente o LARS - Least Angle Regression, o NAMS - Noise Addition Model Selection, a Razão de Falsa Seleção - RFS (FSR em inglês), o LASSO Bayesiano e o Spike-and-Slab LASSO. A metodologia foi a análise e comparação dos métodos estudados e aplicações. Após esse estudo, realizam-se aplicações em bases de dados reais e um estudo de simulação, em que todos os métodos se mostraram promissores, com os métodos Bayesianos apresentando os melhores resultados. / In this work, some new variable selection methods that have appeared in the last 15 years in the context of linear regression are studied, specifically the LARS - Least Angle Regression, the NAMS - Noise Addition Model Selection, the False Selection Rate - FSR, the Bayesian LASSO and the Spike-and-Slab LASSO. The methodology was the analysis and comparison of the studied methods. After this study, applications to real data bases are made, as well as a simulation study, in which all methods are shown to be promising, with the Bayesian methods showing the best results.

Le magmatisme Néogène italien est caractérisé par une grande variété pétrologique et géochimique, couvrant presque entièrement le spectre des roches magmatiques connues dans le monde entier. Le volcanisme récent, Quaternaire, comprenant des laves de composition<br />basiques et intermédiaires, est à la base de la majorité des modèles géodynamiques. Comparativement, le magmatisme acide, correspondant aux premières manifestations sur la marge Tyrrhénienne est beaucoup pour les édifices de la Province Toscane (San Vincenzo, Roccastrada et Amiata). Pour le volcan de Monte Amiata, de nouvelles données isotopiques Sr-Nd et Pb confirment qu'il est en terme de sources un hybride entre les Province Toscane et Romaine. Nous proposons grâce aux âges obtenus un nouveau scénario pour sa mise en place. L'analyse en composantes principales (ACP) des données isotopiques du Pb de toutes les manifestations acides étudiées dans cette thèse a permis d'identifier les deux composants source à l'origine de ces roches. Le composant le plus important est un pôle mantellique<br />correspondant à un mélange entre DM et HIMU, tandis que le second, dont le rôle est mineur comparé au premier, est un pôle enrichi de type crustal. Les roches acides les plus au Sud (Pontines) montrent une influence plus forte du composant DM+HIMU. Ainsi, même sur des<br />roches aussi différenciées et à plus petite échelle (l'Italie centrale), on retrouve la tendance générale propre à l'ensemble de la péninsule Italienne et de la Sicile, dérivée de l'étude isotopique des roches basiques, qui montre un mélange général entre DM et HIMU auquel s'ajoute un composant dérivé de la croûte. L'influence du pôle DM-HIMU est croissante du<br />Nord au Sud de l'Italie. Etendue à l'échelle de la marge Tyrrhénienne italienne, l'ACP permet d'identifier deux<br />domaines sources, délimités par une discontinuité lithosphérique majeure de l'Italie centrale, le 41ème Parallèle, dans lesquels les composants évoluent différemment. Les caractéristiques du domaine Nord pourraient être contrôlées par un processus de délamination de la lithosphère inférieure, celles du domaine Sud par un retrait rapide du slab, les deux<br />phénomènes provoquant une remontée asthénosphérique.

Les serpentinites sont les roches produites par l’hydratation de la péridotite au niveau du plancher océanique. L’antigorite est la phase de haute température et haute pression appartenant au groupe minéral des serpentines, pouvant contenir dans sa structure jusqu’à 13 wt% H2O, et permet ainsi le transfert de quantités considérables d’eau dans le manteau, à travers les processus de subduction. Sa déstabilisation est fonction du chemin thermique emprunté par la plaque plongeante. Durant cette thèse nous avons étudié deux cas de figure pour la déshydratation de l’antigorite menant soit à la libération des fluides dans le coin mantellique et à la production des magmas d’arc, soit au transfert de l’eau à plus grandes profondeurs).Dans un premier temps, des expériences de déshydratation d’antigorite naturelle ont été conduites sur la presse multi-enclumes à 3 GPa et entre 600 et 900°C. Les conditions oxydantes ou bien réductrices ont été contrôlées par le dispositif expérimental (four en graphite ou en chromite de lanthane). Cette étude a permis de caractériser les produits de déshydratation de l’antigorite dans un système chimique représentatif des systèmes naturels ainsi que de contraindre l’état redox des réactions associées. En effet, les résultats mis en avant par cette étude montrent une fO2 équivalente au tampon Quartz-Magnétite-Fayalite (QFM) +5. Un tel potentiel oxydant des fluides issus de la déshydratation de l’antigorite soutient l’hypothèse de l’oxydation de la source mantellique des magmas d’arcs, présentant des rapports Fe3+/Fetotal plus élevés que les basaltes de ride médio-océanique par exemple.Dans un second temps, nous nous sommes intéressés aux modalités de transfert de l’eau dans le manteau profond. L’antigorite naturelle a cette fois été déstabilisée à de plus fortes pressions allant de 6.5 à 10 GPa pour des températures comprises entre 500 et 850°C. Ces résultats expérimentaux, ainsi qu’une analyse géométrique des relations de phases dans le system FMASH selon la méthode de Shreinemaker, ont mis en avant des modifications dans le diagramme de phase pour un système ultramafique hydraté en comparaison des études précédentes. En effet, la phase A est communément décrite comme le produit de déstabilisation de l’antigorite à haute pression, tandis que la phase E n’apparait qu’à des profondeurs plus importantes. Nos résultats suggèrent, dans le système naturel enrichi en aluminium et en fer, une stabilité continue des phases hydratées, suivant la transition antigorite > phase E > phase A pour des températures inférieures à 750°C. Cette étude a également permis d’affiner les estimations des quantités d’eau pouvant être stockées dans les assemblages de minéraux hydratés stables dans la lithosphère plongeante (slab). Dans le cas des plaques plongeantes relativement froides (<750°C à 8-10 GPa) le transport de l’eau par le biais des « Dense Hydrous Magnesium Silicates » (DHMS) phase A et phase E soutient l’hypothèse de l’hydratation de la zone de transition dans le manteau. / From the Mid-Oceanic-Ridge to the subduction trench, hydration of peridotite minerals in the upper part of the oceanic lithosphere produces hydrous phases such as serpentine. Because of its high-water content (13 wt% H2O) this mineral family is of particular interest for water fluxes. Depending on the thermal path followed by the lithosphere while sinking into the mantle, antigorite destabilization can either lead to fluid release in the mantle wedge or water transfer to deeper levels. During this thesis we conducted experimental investigations of antigorite dehydration in the framework of these two scenarios.First, we investigated antigorite dehydration under conditions relevant to slab water release, known to trigger partial melting and to generate arc magmatism. Multi-anvil experiments were conducted on a natural serpentinite sample, at 3 GPa and between 600 and 900°C under different redox conditions. We were able to constrain phase assemblages produced by antigorite dehydration as well as the fO2 of such reactions to 5 units above the FMQ (Fayalite-Magnetite-Quartz buffer). These results support the oxidizing character of slab released fluids, that could explain the oxidized character of arc magmas compared to Mid-Oceanic-Ridge basalts or Oceanic-Island basalts.The second experimental work conducted during this thesis allowed to refine phase equilibria involving antigorite and the Dense Hydrous Magnesium Silicates (DHMS) phase A and phase E, in a realistic chemical composition for hydrated ultramafic system. Antigorite destabilization was performed between 6.5 and 10 GPa, for temperatures in the range <500-850°C. Our experimental results, together with a Shreinemaker’s analysis in the FMASH system led to establish a modified phase diagram compared to those presented in previous studies. While phase A has been described as the high-pressure product of antigorite breakdown in the literature, followed by phase E stability at higher pressure, we propose the transitionantigorite>phase E>phase A for the aluminous and iron-rich hydrated peridotite system. This study allowed the refinement of water budgets that can be stored in relatively cold slabs (<750°C at 8-10 GPa), supporting the hypothesis of water survival down to the transition zone.

A l'échelle de plusieurs dizaines de millions d'années, un système de subduction implique de grandes déformations de la plaque plongeante assimilée un solide viscoélastique, et du manteau supérieur assimilé à un fluide newtonien. L'objectif de ce travail est de développer une stratégie de couplage solide-fluide appliquée à l'étude de l'interaction lithosphère-asthénosphère. Cette stratégie est basée sur l'utilisation de maillages non-conformes aux interfaces et d'une méthode de domaines fictifs (MDF) pour la résolution du problème fluide. Pour l'efficience des modèles 3D, nous employons une formulation simplifiée de la méthode de domaines fictifs par multiplicateurs de Lagrange. La MDF développée est validée par des comparaisons avec des solutions analytiques qui montrent que la méthode est d'ordre 1. La stratégie de couplage est également validée par la comparaison avec d'autres méthodes de couplage solide-fluide. Une première étude est ensuite menée pour analyser l'influence de certains paramètres rhéologiques et cinématiques sur la dynamique d'une subduction contrôlée par les vitesses des plaques. Cette étude, en 2D, concerne plus spécifiquement le mécanisme de plissement périodique du slab lorsque celui-ci est ancré à 660 km de profondeur. Ce mécanisme induit des variations de pendage du slab générant des variations de l'état de contrainte de la plaque chevauchante. Un intérêt particulier est porté sur l'influence de la viscosité du manteau sur les plissements. Dans ce cadre, nous réalisons une application à la subduction andine. / Over the time scale of tens of millions of years, a subduction system involves large deformations of tectonics plates, as one plate sinks into the Earth's mantle. The aim of this work was to develop a soli-fluid coupling method applied to the lithosphere-asthenosphere interaction in the context of subduction zones. Plates were assumed to behave as viscoelastic bodies, while the upper mantle was assimilated to a newtonian fluid. The method developped here is based on the use of non-matching interface meshes and a fictitious domain method (FDM) for the fluid problem. To optimize the computational efficiency of 3D model, we used a simplified version of the Lagrange multipliers fictitious domain method. The developped FDM has been benchmarked with analytical solutions and we showed that this FDM is a first-order method. The coupling method has also been compared to other fluid-solid coupling methods using matching interfaces meshes. A first two-dimensional study was performed in order to evaluate the influence of some rheological and kinematic parameters on the dynamics of a subduction controlled by the velocity of the plates. This study aimed at investigating cyclic slab folding over a rigid 660 km depth transition zone. This folding mechanism induces variations in slab dip that generate variations in the stress state of the overriding plate. We focussed on the influence of the upper mantle viscosity on slab folding. We also applied this model to the Andean subduction zone. Several studies have determined a cyclic variation of the South-American tectonic regime (period of 30-40~Myrs) which may have been related to the slab dip evolution.