Disseny de materials compostos ceràmics mitjançant impressió 3D

La zircònia és un material que es troba en alça en diversos sectors industrials degut a les interessants propietats mecàniques així com la seva estabilitat química i biocompatibilitat. La dificultat a l’hora de fabricar peces de geometria complexa però, ha estat limitant la seva utilització i expansió. En les darreres dècades i degut al avenços tecnològics que incorpora la tecnologia d’impressió 3D s’obre un ampli camp d’estudi. Aquesta podria permetre l’obtenció d’aquests dissenys avançats a preus realment competitius respecte a tècniques convencionals. En el següent projecte de final de grau es duu a terme un exhaustiu procés de caracterització microestructural i mecànica d’aquest material com a base d’un producte capaç de ser utilitzat per a la tecnologia d’impressió 3D. Pel que fa al estudi microestructural de les mostres es realitzen diversos processos per a conèixer rugositat, densitat, porositat i mida de gra. D’altra banda, per dur a terme la caracterització mecànica s’estudia la duresa a diferents escales, tenacitat, resposta a assaigs de ratllada i fatiga

Estimación de resultados deportivos mediante modelos lineales generalizados

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2023, Director: Josep Fortiana Gregori[es] En este trabajo se explica el contexto histórico sobre diversos estudios que se han hecho tratando de encontrar una forma óptima para predecir el resultado de un partido de futbol. Explicaremos, definiremos y detallaremos también como calcular los modelos lineales generalizados. Finalmente trataremos de aplicar lo aprendido de cara a definir un modelo de regresión lineal de Poisson para predecir los resultados de una temporada de fútbol entera

UO2 surface oxidation by mixtures of water vapor and hydrogen as a function of temperature

In the present work, X-Ray Photoelectron Spectroscopy (XPS) was used to study the effect of water vapor on the UO2 surface as a function of temperature. The experiments were performed in situ inside a high pressure chamber attached to the XPS instrument. UO2 samples were put in contact with either hydrogen or argon streams, saturated with water at room temperature, and the sample surface evolution was analyzed by XPS. In the case of the water vapor/argon experiments, one experiment at 350°C was performed and, in the case of the water vapor/hydrogen experiments, the temperatures used inside the reactor were 60, 120, 200 and 350°C. On one hand, in presence of argon, the results obtained showed that the water vapor in the argon stream oxidized 93% of the U(IV) in the sample surface. On the other hand, the degree of UO2 surface oxidation showed a different dependence on the temperature in the experiments performed in the presence of hydrogen: the maximum surface oxidation occurred at 120°C, where 65.4% of U(IV) in the sample surface was oxidized, while at higher temperatures, the surface oxidation decreased. This observation is attributed to the increase of hydrogen reducing effect when temperature increases which prevents part of the oxidation of the UO2 surface by the water vapor.Peer ReviewedPostprint (author's final draft

Transoesophageal detection of heart graft rejection by electrical impedance: using Finite Element Method simulations

Previous studies have shown that it is possible to evaluate heart graft rejection level using a bioimpedance technique by means of an intracavitary catheter. However, this technique does not present relevant advantages compared to the gold standard for the detection of a heart rejection, which is the biopsy of the endomyocardial tissue. We propose to use a less invasive technique that consists in the use of a transoesophageal catheter and two standard ECG electrodes on the thorax. The aim of this work is to evaluate different parameters affecting the impedance measurement, including: sensitivity to electrical conductivity and permittivity of different organs in the thorax, lung edema and pleural water. From these results, we deduce the best estimator for cardiac rejection detection, and we obtain the tools to identify possible cases of false positive of heart rejection due to other factors. To achieve these objectives we have created a thoracic model and we have simulated, with a FEM program, different situations at the frequencies of 13, 30, 100, 300 and 1000 kHz. Our simulation demonstrates that the phase, at 100 and 300 kHz, has the higher sensitivity to changes in the electrical parameters of the heart muscle.Peer ReviewedPostprint (author’s final draft

Online action recognition

Recognition in planning seeks to find agent intentions, goals or activities given a set of observations and a knowledge library (e.g. goal states, plans or domain theories). In this work we introduce the problem of Online Action Recognition. It consists in recognizing, in an open world, the planning action that best explains a partially observable state transition from a knowledge library of first-order STRIPS actions, which is initially empty. We frame this as an optimization problem, and propose two algorithms to address it: Action Unification (AU) and Online Action Recognition through Unification (OARU). The former builds on logic unification and generalizes two input actions using weighted partial MaxSAT. The latter looks for an action within the library that explains an observed transition. If there is such action, it generalizes it making use of AU, building in this way an AU hierarchy. Otherwise, OARU inserts a Trivial Grounded Action (TGA) in the library that explains just that transition. We report results on benchmarks from the International Planning Competition and PDDLGym, where OARU recognizes actions accurately with respect to expert knowledge, and shows real-time performance.Peer ReviewedPostprint (author's final draft

Disseny mecànic d’una ortesi activa per a lesionats medul·lars a partir de l’anàlisi dinàmica de la marxa humana

Premi al millor Projecte de Fi de Carrera presentat durant l'any 2013 en l'àmbit de Mecànica que atorga la CÀTEDRA ALSTOMEn aquest projecte es presenta el disseny mecànic d’una ortesi activa tipus SCKAFO (Stance Control Knee Ankle Foot Orthosis) pensada per assistir la marxa de lesionats medul·lars incomplets, amb una classificació C o D segons ASIA (American Spinal Injunry Associaton). Per comprendre el mecanisme seguit per les persones al caminar, s’inclou una breu explicació sobre la biomecànica de la marxa humana. També es descriuen quines són les mancances dels lesionats medul·lars que es poden beneficiar de la tecnologia dissenyada. A més, es realitza una recerca bibliogràfica sobre l’estat de l’art de les ortesis i de l’anàlisi de la marxa, aspecte fonamental per al disseny de dispositius exosquelètics. Per a la realització del disseny cal conèixer les especificacions mecàniques, que són els esforços articulars que realitza una persona sana quan camina. Per a tal fi, es fa una anàlisi dinàmica de la marxa humana. Coneixent la cinemàtica i les forces de contacte amb el terra d’un subjecte sa caminant, es resol un problema de dinàmica inversa. S’utilitzen les equacions de Lagrange amb multiplicadors per trobar els esforços desitjats. Les dades de moviment i de força necessàries per a l’anàlisi s’obtenen a partir d’una captura realitzada al laboratori de biomecànica de l’ETSEIB. Al llarg del projecte es fa una explicació de la metodologia seguida per fer la captura i es presenten i discuteixen els resultats obtinguts, tant a nivell cinemàtic com a nivell dinàmic. Un cop es coneixen les especificacions, es realitza el disseny mecànic del dispositiu sota la hipòtesi que els esforços necessaris per a la marxa assistida d’un lesionat són aproximadament els mateixos que els necessaris per a la marxa d’un subjecte sa (Kao et al., 2010). L’ortesi es dissenya seguint les recomanacions d’un metge i un tècnic ortopeda. El resultat és una ortesi que actua de forma passiva, amb una molla, sobre el turmell i de forma activa sobre el genoll. L’actuació sobre el genoll es realitza amb un motor elèctric i un reductor -col·locats en paral·lel a la cuixa per tal d’estalviar espai- durant la fase de balanceig i amb un sistema de bloqueig comercial durant la fase de recolzament. El funcionament es troba automatitzat gràcies a un sistema de control. Finalment, es fa una anàlisi de viabilitat del projecte per al cas que es vengués l’ortesi durant 7 anys a l’estat espanyol i que la seva producció fos seriada. Aquesta anàlisi dóna per suposada la viabilitat tècnica de la solució per la que s’ha optat i estudia la viabilitat a nivell social, econòmic i ambiental. A nivell social, es fa una hipòtesi dels clients que es tindran a partir de dades estadístiques de lesionats medul·lars. A nivell ambiental, es justifica un ús racional dels recursos i s’explica breument quin seria el procés a seguir per tractar els residus. A nivell econòmic, es realitza un estudi de la viabilitat de comercialització del producte i es dóna una estimació del preu de vendaAward-winnin

New Bactericide Orthodonthic Archwire: NiTi with Silver Nanoparticles

A potential new bactericide treatment for NiTi orthodontic archwires based in the electrodeposition of silver nanoparticles on the surface was studied. Twenty-five archwires were treated by electrodeposition, obtaining nanoparticles of silver embedded on the archwire surface. These were evaluated in order to investigate the possible changes on the superelastic characteristics (critical temperatures and stresses), the nickel ion release, and the bacteria culture behavior. The chemical composition was analyzed by Energy Dispersive X-Ray Spectroscopy-microanalysis; the singular temperatures of the martensitic transformation were obtained by a flow calorimeter. Induced martensitic transformation stresses were obtained by mechanical testing apparatus. Nickel ion release was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) equipment using artificial saliva solution at 37 °C. Bacterial tests were studied with the most used oral bacterial strains: Streptococcus sanguinis and Lactobacillus salivarius. NiTi samples were immersed in bacterial suspensions for 2 h at 37 °C. Adhered bacteria were separated and seeded on agar plates: Tood-Hewitt (TH) and Man-Rogosa-Sharpe (MRS) for S. sanguinis and for L.salivarius, respectively. These were then incubated at 37 °C for 1 day and the colonies were analyzed. The results showed that the transformation temperatures and the critical stresses have not statistically significant differences. Likewise, nickel ion release at different immersion times in saliva at 37 °C does not present changes between the original and treated with silver nanoparticles archwires. Bacteria culture results showed that the reduction of the bacteria due to the presence to the nanoparticles of silver is higher than 90%. Consequently, the new treatment with nanoparticles of silver could be a good candidate as bactericidic orthodontic archwire.Gobierno de España y la Unión Europea RTI2018-098075-B-C22Generalitat de Catalunya 2017SGR70

A Distributed Control Strategy for Islanded Single-Phase Microgrids with Hybrid Energy Storage Systems Based on Power Line Signaling

Energy management control is essential to microgrids (MGs), especially to single-phase ones. To handle the variety of distributed generators (DGs) that can be found in a MG, e.g., renewable energy sources (RESs) and energy storage systems (ESSs), a coordinated power regulation is required. The latter are generally battery-based systems whose lifetime is directly related to charge/discharge processes, whereas the most common RESs in a MG are photovoltaic (PV) units. Hybrid energy storage systems (HESS) extend batteries life expectancy, thanks to the effect of supercapacitors, but they also require more complex control strategies. Conventional droop methodologies are usually applied to provide autonomous and coordinated power control. This paper proposes a method for coordination of a single-phase MG composed by a number of sources (HESS, RES, etc.) using power line signaling (PLS). In this distributed control strategy, a signal whose frequency is higher than the grid is broadcasted to communicate with all DGs when the state of charge (SoC) of the batteries reaches a maximum value. This technique prevents batteries from overcharging and maximizes the power contribution of the RESs to the MG. Moreover, different commands apart from the SoC can be broadcasted, just by changing to other frequency bands. The HESS master unit operates as a grid-forming unit, whereas RESs act as grid followers. Supercapacitors in the HESS compensate for energy peaks, while batteries respond smoothly to changes in the load, also expanding its lifetime due to less aggressive power references. In this paper, a control structure that allows the implementation of this strategy in single-phase MGs is presented, with the analysis of the optimal range of PLS frequencies and the required self-adaptive proportional-resonant controllers

Immobilization of selenite onto natural siderite (FeCO3)

The sorption processes of metals and semimetals on siderite are being studied because of the potential adequacy of the mineral for removing contaminants from natural waters and because of its formation during the reduction of iron(III) (hydr)oxides under anaerobic conditions in the presence of organic matter or bacteria. This transformation could involve the release of contaminants previously sorbed on the iron(III) (hydr)oxides. In this work, the sorption of selenite on natural siderite (Bordes de Conflent, Lleida, Spain) is experimentally studied and the results obtained are compared to the previous results on selenite sorption on magnetite, hematite and goethite.Results indicate that the process of sorption was very fast; the equilibrium was reached in less than 1 hour, which indicates that sorption will not be kinetically controlled. The experimental data were fitted with a non-competitive Langmuir isotherm, which would indicate that the main process for the decrease of selenite in solution would be its sorption on siderite via monolayer coverage of the solid surface. The values of maximum sorption capacity of siderite obtained at pH 7,1 and 8,0 were 6,9 10-7 and 6,4 10-7 mol g-1, respectively and the same value of Langmuir constant was obtained for both pH values, 4,7 104 L mol-1.Postprint (published version