Anàlisi del comportament d’una unió cargolada entre dues peces plàstiques reforçades amb fibra de vidre

En aquest projecte de final de grau es té com a objectiu principal analitzar el comportament a tallant que presenta una unió cargolada entre dues peces de plàstic formades per una matriu de resina de polièster i un reforç de fibra de vidre, és a dir, entre dues peces d’un material compost. Com a context, s’ha considerat el tipus d’unió que es podria trobar en la carcassa d’una aerogenerador eòlic. En primer lloc, es volien dur a terme uns assajos experimentals, els quals no s’han pogut acabar realitzant degut a l’emergència sanitària global declarada a causa del Covid19. S’han documentat exhaustivament com si s’haguessin fet però sense obtenir resultats, ja que és un material útil per entendre la resta del projecte. En segon lloc, s’ha estudiat aquesta unió de dues peces de material compost des d’un punt de vista teòric. Amb aquests càlculs realitzats, s’ha acabat determinant de quina manera fallarà el conjunt. En tercer lloc, s’ha estudiat també aquesta unió des del punt de vista d’una simulació per ordinador fent servir el conegut mètode dels elements finits. S’ha desenvolupat de forma exhaustiva i també s’ha pogut acabar determinant, amb els resultats obtinguts, de quina manera entrarà en fallada el conjunt. Ja per acabar, s’ha desenvolupat un petit punt de correlació de resultats per extreure determinades conclusions de l’estudi d’aquest sistema d’una unió cargolada de dues peces de material compost des dels dos punts de vista treballats: el teòric i la simulació

Bimetallic Ru–Pd supported on CeO2 for the catalytic partial oxidation of methane into syngas

A series of monometallic Ru, Pd, and bimetallic Ru–Pd catalysts loaded on CeO2 support have been prepared via mechanochemical and conventional incipient wetness impregnation methods and used in the partial oxidation of methane (POM) to obtain synthesis gas (H2 and CO). The influence of the preparation method, the order of addition of the metals, the Ru:Pd metal ratio, and the milling energy and time for samples prepared by the mechanochemical method, have been evaluated between 300 and 600 °C. The results revealed that bimetallic Ru–Pd/CeO2 catalysts outperform monometallic Ru–CeO2 and Pd–CeO2 for POM, both in terms of catalytic activity and stability. Additionally, the bimetallic Ru–Pd/CeO2 catalysts prepared by ball milling produced syngas at a much lower temperature compared to the conventional catalysts prepared by incipient wetness impregnation. Raman spectroscopy, temperature programmed reduction (H2–TPR), X–ray photoelectron spectroscopy (XPS) and high–resolution transmission electron microscopy (HRTEM) have been used to characterize the catalysts before and after reaction.Peer ReviewedPostprint (published version

Low-temperature partial oxidation of methane over Pd–Ni bimetallic catalysts supported on CeO2

Monometallic Pd and Ni and bimetallic Pd–Ni catalysts supported on CeO2 are prepared via mechanochemical and conventional incipient wetness impregnation methods and tested for the production of syngas by the partial oxidation of methane. Compared with monometallic Ni/CeO2 and Pd/CeO2, bimetallic Pd–Ni/CeO2 catalysts show considerable higher methane conversion and syngas yield. Additionally, the bimetallic catalysts prepared by ball milling produce syngas at lower temperature. Different preparation parameters, such as metal loading, Pd/Ni ratio, milling energy, milling time and order of incorporation of the metals are examined. The best performance is obtained with a bimetallic catalyst prepared at 50 Hz for 20 min with only 0.12 wt% Pd and 1.38 wt% Ni. Stability tests demonstrate superior stability for bimetallic Pd–Ni/CeO2 catalysts prepared by a mechanochemical approach. From the characterization results, this is explained in terms of an impressive dispersion of metal species with a strong interaction with the surface of CeO2.Peer ReviewedPostprint (published version

Les biblioteques públiques a Dinamarca: punt i a part

Visió general del sistema bibliotecari danès, centrada en la biblioteca pública: legislació, informatització, serveis centrals, estructura i serveis de la biblioteca

Review of the Decomposition of Ammonia to Generate Hydrogen

Because of the problems associated with the generation and storage of hydrogen in portable applications, the use of ammonia has been proposed for on-site production of hydrogen through ammonia decomposition. First, an analysis of the existing systems for ammonia decomposition and the challenges for this technology are presented. Then, the state of the art of the catalysts used to date for ammonia decomposition is described considering the catalysts composed of noble and non-noble metals and their combinations, as well as novel materials such as alkali metal amides and imides. The effect of the supports and promoters used is analyzed in detail, and the catalytic activity obtained is compared. An analysis of the kinetics of the reaction obtained with different catalysts is also presented and discussed, including the reaction mechanism, the determining step of the reaction, and the apparent activation energy. Finally, the structured reactors used to date for the decomposition reaction of ammonia are explored, as well as the possibilities offered by catalytic membrane reactors, which allow the on-site simultaneous production and separation of hydrogen.Peer ReviewedPostprint (author's final draft

How to speak the same language: key ideas from the forum on Catalan wildfire research

Postprint (published version

The catalytic activity of the Pr2Zr2-xFexO7±d system for the CO oxidation reaction

One of the alternatives to decrease the concentration of CO is its oxidation reaction to CO2, which can be made more efficient using catalysts. In this work, it is shown that pyrochlore structures are a promising candidate to act as heterogeneous catalysts due to their chemical and physical properties. For use as a catalyst in this reaction, the Pr2Zr2-xFexO7±d (x = 0, 0.05, 0.10, and 0.15) system was synthesized by the solvothermal method, firing the powder obtained at temperatures of 1200 and 1400°C. The diffraction patterns confirmed the pyrochlore structure as the single phase in all the nominal compositions. The Brunauer–Emmett–Teller method and dynamic light-scattering analysis showed an increase in the particle size and a decrease in the specific surface area when increasing the iron concentration and increasing the calcination temperature. The compositions that presented the best catalytic activity were the samples with the highest iron concentration. Moreover, these samples were able to convert all the CO oxidation reactions in a narrower temperature range than a conventional CeO2 sample. The presence of vacancies and the redox behavior of the elements present are the key factors for the catalysis of this system in the CO oxidation reaction.Postprint (published version

Seroepidemiologia de l’hepatitis C a Catalunya l’any 2002

Seroepidemiologia; Hepatitis C; Factors de risc; PrevencióSeroepidemiología; Hepatits C; Factores de riesgo; PrevenciónSeroepidemiology; Hepatitis C; Risk factors; PreventionIntroducció. L’hepatitis C és una malaltia vírica crònica que disposa d’un tractament farmacològic molt efectiu. L’objectiu del treball que es presenta va ser estudiar la seroprevalença de l’hepatitis C en població de ≥5 anys de Catalunya l’any 2002 i comparar la prevalença trobada l’any 2002 amb la prevalença trobada en un estudi realitzat l’any 1996. Mètodes i resultats. Es va obtenir una mostra representativa (n=2620) de la població de ≥5 anys de Catalunya. Es van obtenir mostres de sèrum i es van utilitzar les proves d’ELISA i immunoassaig recombinant (RIBA) (Ortho Diagnostics) per determinar la seroprevalença de persones amb infecció pel virus de l’hepatitis C (VHC). La prevalença d’infecció pel VHC l’any 2002 era de l’1,3% (l’1% en els homes i l’1,5% en les dones). La prevalença d’infecció pel VHC s’associava amb drogoaddicció parenteral (ORaj=36,5, p <0,01), tatuatges (ORaj=26,1, p <0,001) i transfusions de sang (ORaj=6,8, p <0,005). La prevalença d’infecció pel VHC s’havia reduït un 48% entre el 1996 i el 2002 (un 2,5% el 1996 i un 1,3% el 2002). Conclusions. La prevalença d’infecció pel VHC era de l’1,3% el 2002. La prevalença d’infecció pel VHC s’havia reduït entre el 1996 i el 2002, possiblement per les activitats preventives desenvolupades a Catalunya.Introducción. La hepatitis C es una enfermedad vírica crónica para la que se dispone de un tratamiento farmacológico muy efectivo. El objetivo del trabajo que se presenta fue estudiar la seroprevalencia de la hepatitis C en población de ≥5 años de Cataluña en el 2002 y comparar la prevalencia obtenida en el año 2002 con la prevalencia obtenida en un estudio realizado el año 1996. Métodos y resultados. Se obtuvo una muestra representativa (n=2620) de la población de ≥5 años. Se obtuvieron muestras de suero y se utilizaron pruebas de ELISA e inmunoensayo recombinante (RIBA) (Ortho Diagnostics) para determinar la seroprevalencia de personas con infección por el virus de la hepatitis C (VHC). La prevalencia de infección por el VHC en el 2002 fue del 1,3% (el 1% en los hombres y el 1,5% en las mujeres). La prevalencia de infección por el VHC se asociaba con drogadicción parenteral (ORaj=36,5, p <0,01), tatuajes (ORaj=26,1, p <0,001) y transfusiones de sangre (ORaj=6, 8, p <0,005). La prevalencia de infección por el VHC se había reducido un 48% entre el 1996 y el 2002 (un 2,5% el 1996 y un 1,3% el 2002). Conclusiones. La prevalencia de infección por el VHC era del 1,3% en el 2002. La prevalencia de infección por el VHC se había reducido entre 1996 y 2002, posiblemente por las actividades preventivas desarrolladas en Cataluña.Background. THepatitis C is a chronic viral disease for which a very effective pharmacological treatment is available. The aim of the present study was to analyse hepatitis C virus (HCV) seroprevalence in population aged ≥5 years in Catalonia in 2002, and to compare the seroprevalence found in 2002 with the prevalence found in a study carried out in 1996. Methods and Results. A representative sample (N=2620) of the population aged ≥5 years in Catalonia was obtained. Serum samples were obtained, and ELISA and RIBA assays (Ortho Diagnostics) were used to determine the seroprevalence of HCVinfected people. The prevalence of HCV infection in 2002 was 1.3%, 1% in men, and 1.5% in women. The prevalence of HCV infection was associated with parenteral drug abuse (ORadj=36.5, p<0.01), tattoos (ORadj=26.1, p<0.001), and blood transfusions (ORadj=6, 8, p<0.005). Prevalence of HCV infection had been reduced by 48% between 1996 and 2002 (2.5% vs. 1.3%). Conclusions. Prevalence of HCV infection was estimated to be 1.3% in 2002. A decrease in HCV prevalence occurred between 1996 and 2002, possibly due to preventive activities developed in Catalonia

Operando NAP-XPS studies of a ceria-supported Pd catalyst for CO oxidation

Supported Pd/CeO2 catalytic systems have been widely investigated in the low-temperature oxidation of CO (LTO CO) due to the unique oxygen storage capacity and redox properties of the ceria support, which highly influence the structural, chemical and electronic state of Pd species. Herein, operando near-ambient pressure XPS (NAP-XPS) technique has allowed the study of a conventional Pd/CeO2 catalyst surface during the CO oxidation reaction under experimental conditions closer to the actual catalytic reaction, unfeasible with other surface science techniques that demand UHV conditions. SEM, HRTEM and XRD analyses of the powder catalyst, prepared by conventional incipient wetness impregnation, reveal uniformly CeO2-loaded Pd NPs of less than 2 nm size, which generated an increase in oxygen vacancies with concomitant ceria reduction, as indicated by H2-TPR and Raman measurements. Adsorbed peroxide (O22-) species on the catalyst surface could also be detected by Raman spectra. Operando NAP-XPS results obtained at the ALBA Synchrotron Light Source revealed two kinds of Pd species under reaction conditions, namely PdOx and PdII ions in a PdxCe1-xO2-d solution, the latter one appearing to be crucial for the CO oxidation. By means of a non-destructive depth profile analysis using variable synchrotron excitation energies, the location and the role of these palladium species in the CO oxidation reaction could be clarified: PdOx was found to prevail on the upper surface layers of the metallic Pd supported NPs under CO, while under reaction mixture it was rapidly depleted from the surface, leaving a greater amount in the subsurface layers (7% vs. 12%, respectively). On the contrary, the PdxCe1-xO2-d phase, which was created at the Pd–CeO2 interface in contact with the gas environment, appeared to be predominant on the surface of the catalyst. Its presence was crucial for CO oxidation evolution, acting as a route through which active oxygen species could be transferred from ceria to Pd species for CO oxidation.Peer ReviewedPostprint (published version