Deposici��n de carbono en las superficies de pel��culas delgadas de Fe sumergidas en tolueno en condiciones ambientales

Las nanoestructuras han sido muy estudiadas debido a su importancia en aplicaciones tecnol��gicas y biom��dicas, como por ejemplo el recubrimiento de los sensores y biosensores. Estas necesitan ser recubiertas para su protecci��n y/o funcionalizaci��n. Un estudio sobre las superficies de nanopart��culas magn��ticas y esf��ricas (MNPs) de Fe y Ni revel�� que el tolueno act��a como catalizador de reacciones de condensaci��n de los componentes arom��ticos formando estructuras gigantes, polic��clicas e irregulares, creando as�� una especie de recubrimiento de carbono. Tambi��n se ha estudiado la posibilidad de formar recubrimientos con carbono en pel��culas de hierro y permalloy (FeNi) en tiempos largos de tratamiento de 1 a��o. En el presente trabajo, debido a los resultados anteriores para las pel��culas delgadas de hierro, se ha estudiado el desarrollo del proceso de deposici��n del grafeno defectuoso a temperatura ambiente, sobre las superficies de las pel��culas delgadas de hierro en periodos de entre unos d��as hasta medio a��o aproximadamente. Se ha hecho un estudio en funci��n del tiempo de inmersi��n en tolueno de las propiedades estructurales y magn��ticas de las pel��culas de hierro depositadas sobre vidrio. Las pel��culas de hierro han sido preparadas por el m��todo de pulverizaci��n cat��dica y despu��s sumergidas en tolueno. Las t��cnicas utilizadas para la caracterizaci��n estructural han sido, la difracci��n de Rayos-X, los estudios de microscopia electr��nica de barrido (SEM) y la perfil��metr��a. La caracterizaci��n magn��tica se ha hecho con un magnet��metro de Kerr (MOKE) y un magnet��metro vibrante (VSM). Las muestras cristalizaban en el sistema c��bico FCC del grupo espacial Fm-3m, con par��metro de celda de 3.5922��. El tama��o de dominio coherente para los ��ndices de Miller (110) ha ido aumentando a lo largo del tratamiento. Para el ��ndice de Miller (211) el tama��o de dominio coherente ha disminuido. Este comportamiento se explica tendiendo en cuenta el modelo propuesto en la literatura cient��fica del proceso de formaci��n de las estructuras de grafeno defectuoso. El an��lisis de las im��genes de SEM y los correspondientes datos de la emisi��n de Rayos-X han confirmado la presencia del carbono en la superficie. La cantidad del carbono en la superficie de las pel��culas de hierro aumenta con el incremento del tiempo de inmersi��n en tolueno. Ha sido posible detectar la presencia del carbono en la superficie despu��s de 9 d��as de inmersi��n (por lo tanto, el proceso de las estructuras polic��clicas e irregulares es relativamente r��pido). La deposici��n del carbono no resulta en una formaci��n de estructura uniforme, as�� que cuanto m��s largo es el tratamiento, m��s complicadas son las estructuras. Como resultado del tratamiento superficial durante aproximadamente medio a��o, se observa un aumento de rugosidad de un micr��metro aproximadamente. La diferencia entre las medidas de MOKE y VSM para el campo coercitivo y la remanencia, se explica teniendo en cuenta el proceso de oxidaci��n de la superficie y la interacci��n de algunas partes de la pel��cula de hierro con el tolueno, que pueden causar la relajaci��n de las tensiones. La imanaci��n de saturaci��n obtenida para las pel��culas despu��s del tiempo de tratamiento de 135 d��as es de 192 emu por gramo. La disminuci��n de la imanaci��n de saturaci��n es debida a la oxidaci��n de las pel��culas por el contacto con la atm��sfera y el tolueno. En un c��lculo aproximado se ha llegado a la conclusi��n que dicha capa tiene un espesor de 50 nm, repartida en dos capas de 25 nm. De todo lo anterior y de la base de an��lisis de las propiedades estructurales y magn��ticas de las pel��culas delgadas de hierro sumergidas en tolueno para hacer el tratamiento superficial a temperatura ambiente, se concluye, que las estructuras polic��clicas e irregulares de grafeno defectuoso se forman relativamente r��pido. El tratamiento con el tolueno no causa muchos cambios en la estructura y en las propiedades magn��ticas, se trata de procesos superficiales. La modificaci��n in situ de pel��culas de hierro en tolueno, puede ser candidato a m��todo de protecci��n y funcionalizaci��n de los sensores magn��ticos.

On the optimal usage of labelled examples in semi-supervised multi-class classification problems

In recent years, the performance of semi-supervised learning has been theoretically investigated. However, most of this theoretical development has focussed on binary classification problems. In this paper, we take it a step further by extending the work of Castelli and Cover [1] [2] to the multi-class paradigm. Particularly, we consider the key problem in semi-supervised learning of classifying an unseen instance x into one of K different classes, using a training dataset sampled from a mixture density distribution and composed of l labelled records and u unlabelled examples. Even under the assumption of identifiability of the mixture and having infinite unlabelled examples, labelled records are needed to determine the K decision regions. Therefore, in this paper, we first investigate the minimum number of labelled examples needed to accomplish that task. Then, we propose an optimal multi-class learning algorithm which is a generalisation of the optimal procedure proposed in the literature for binary problems. Finally, we make use of this generalisation to study the probability of error when the binary class constraint is relaxed.

Bertso transformation with pattern-based sampling

This paper presents a method to generate new melodies, based on conserving the semiotic structure of a template piece. A pattern discovery algorithm is applied to a template piece to extract significant segments: those that are repeated and those that are transposed in the piece. Two strategies are combined to describe the semiotic coherence structure of the template piece: inter-segment coherence and intra-segment coherence. Once the structure is described it is used as a template for new musical content that is generated using a statistical model created from a corpus of bertso melodies and iteratively improved using a stochastic optimization method. Results show that the method presented here effectively describes a coherence structure of a piece by discovering repetition and transposition relations between segments, and also by representing the relations among notes within the segments. For bertso generation the method correctly conserves all intra and inter-segment coherence of the template, and the optimization method produces coherent generated melodies.

Advanced Reaction Systems for Hydrogen Production

[EN] This PhD work started in March 2010 with the support of the University of the Basque Country (UPV/EHU) under the program named ���Formaci��n de Personal Investigador��� at the Chemical and Environmental Engineering Department in the Faculty of Engineering of Bilbao. The major part of the Thesis work was carried out in the mentioned department, as a member of the Sustainable Process Engineering (SuPrEn) research group. In addition, this PhD Thesis includes the research work developed during a period of 6 months at the Institut f��r Mikrotechnik Mainz GmbH, IMM, in Germany. During the four years of the Thesis, conventional and microreactor systems were tested for several feedstocks ���renewable and non-renewable, gases and liquids��� through several reforming processes in order to produce hydrogen. For this purpose, new catalytic formulations which showed high activity, selectivity and stability were design. As a consequence, the PhD work performed allowed the publication of seven scientific articles in peer-reviewed journals. This PhD Thesis is divided into the following six chapters described below. The opportunity of this work is established on the basis of the transition period needed for moving from a petroleum based energy system to a renewable based new one. Consequently, the present global energy scenario was detailed in Chapter 1, and the role of hydrogen as a real alternative in the future energy system was justified based on several outlooks. Therefore, renewable and non-renewable hydrogen production routes were presented, explaining the corresponding benefits and drawbacks. Then, the raw materials used in this Thesis work were described and the most important issues regarding the processes and the characteristics of the catalytic formulations were explained. The introduction chapter finishes by introducing the concepts of decentralized production and process intensification with the use of microreactors. In addition, a small description of these innovative reaction systems and the benefits that entailed their use were also mentioned. In Chapter 2 the main objectives of this Thesis work are summarized. The development of advanced reaction systems for hydrogen rich mixtures production is the main objective. In addition, the use and comparison between two different reaction systems, (fixed bed reactor (FBR) and microreactor), the processing of renewable raw materials, the development of new, active, selective and stable catalytic formulations, and the optimization of the operating conditions were also established as additional partial objectives. Methane and natural gas (NG) steam reforming experimental results obtained when operated with microreactor and FBR systems are presented in Chapter 3. For these experiments nickel-based (Ni/Al2O3 and Ni/MgO) and noble metal-based (Pd/Al2O3 and Pt/Al2O3) catalysts were prepared by wet impregnation and their catalytic activity was measured at several temperatures, from 973 to 1073 K, different S/C ratios, from 1.0 to 2.0, and atmospheric pressure. The Weight Hourly Space Velocity (WHSV) was maintained constant in order to compare the catalytic activity in both reaction systems. The results obtained showed a better performance of the catalysts operating in microreactors. The Ni/MgO catalyst reached the highest hydrogen production yield at 1073 K and steam-to-carbon ratio (S/C) of 1.5 under Steam methane Reforming (SMR) conditions. In addition, this catalyst also showed good activity and stability under NG reforming at S/C=1.0 and 2.0. The Ni/Al2O3 catalyst also showed high activity and good stability and it was the catalyst reaching the highest methane conversion (72.9 %) and H2out/CH4in ratio (2.4) under SMR conditions at 1073 K and S/C=1.0. However, this catalyst suffered from deactivation when it was tested under NG reforming conditions. Regarding the activity measurements carried out with the noble metal-based catalysts in the microreactor systems, they suffered a very quick deactivation, probably because of the effects attributed to carbon deposition, which was detected by Scanning Electron Microscope (SEM). When the FBR was used no catalytic activity was measured with the catalysts under investigation, probably because they were operated at the same WHSV than the microreactors and these WHSVs were too high for FBR system. In Chapter 4 biogas reforming processes were studied. This chapter starts with an introduction explaining the properties of the biogas and the main production routes. Then, the experimental procedure carried out is detailed giving concrete information about the experimental set-up, defining the parameters measured, specifying the characteristics of the reactors used and describing the characterization techniques utilized. Each following section describes the results obtained from activity testing with the different catalysts prepared, which is subsequently summarized: Section 4.3: Biogas reforming processes using ��-Al2O3 based catalysts The activity results obtained by several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 are presented in this section. In addition, an alumina-based commercial catalyst was tested in order to compare the activity results measured. Four different biogas reforming processes were studied using a FBR: dry reforming (DR), biogas steam reforming (BSR), biogas oxidative reforming (BOR) and tri-reforming (TR). For the BSR process different steam to carbon ratios (S/C) from 1.0 to 3.0, were tested. In the case of BOR process the oxygen-to-methane (O2/CH4) ratio was varied from 0.125 to 0.50. Finally, for TR processes different S/C ratios from 1.0 to 3.0, and O2/CH4 ratios of 0.25 and 0.50 were studied. Then, the catalysts which achieved high activity and stability were impregnated in a microreactor to explore the viability of process intensification. The operation with microreactors was carried out under the best experimental conditions measured in the FBR. In addition, the physicochemical characterization of the fresh and spent catalysts was carried out by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), N2 physisorption, H2 chemisorption, Temperature Programmed Reduction (TPR), SEM, X-ray Photoelectron Spectroscopy (XPS) and X-ray powder Diffraction (XRD). Operating with the FBR, conversions close to the ones predicted by thermodynamic calculations were obtained by most of the catalysts tested. The Rh-Ni/Ce-Al2O3 catalyst obtained the highest hydrogen production yield in DR. In BSR process, the Ni/Ce-Al2O3 catalyst achieved the best activity results operating at S/C=1.0. In the case of BOR process, the Ni/Ce-Zr-Al2O3 catalyst showed the highest reactants conversion values operating at O2/CH4=0.25. Finally, in the TR process the Rh-Ni/Ce-Al2O3 catalyst obtained the best results operating at S/C=1.0 and O2/CH4=0.25. Therefore, these three catalysts were selected to be coated onto microchannels in order to test its performance under BOR and TR processes conditions. Although the operation using microreactors was carried out under considerably higher WHSV, similar conversions and yields as the ones measured in FBR were measured. Furthermore, attending to other measurements like Turnover Frequency (TOF) and Hydrogen Productivity (PROD), the values calculated for the catalysts tested in microreactors were one order of magnitude higher. Thus, due to the low dispersion degree measured by H2-chemisorption, the Ni/Ce-Al2O3 catalyst reached the highest TOF and PROD values. Section 4.4: Biogas reforming processes using Zeolites L based catalysts In this section three type of L zeolites, with different morphology and size, were synthesized and used as catalyst support. Then, for each type of L zeolite three nickel monometallic and their homologous Rh-Ni bimetallic catalysts were prepared by the wetness impregnation method. These catalysts were tested using the FBR under DR process and different conditions of BSR (S/C ratio of 1.0 and 2.0), BOR (O2/CH4 ratio of 0.25 and 0.50) and TR processes (at S/C=1.0 and O2/CH4=0.25). The characterization of these catalysts was also carried out by using the same techniques mentioned in the previous section. Very high methane and carbon dioxide conversion values were measured for almost all the catalysts under investigation. The experimental results evidenced the better catalytic behavior of the bimetallic catalysts as compared to the monometallic ones. Comparing the catalysts behavior with regards to their morphology, for the BSR process the Disc catalysts were the most active ones at the lowest S/C ratio tested. On the contrary, the Cylindrical (30���60 nm) catalysts were more active under BOR conditions at O2/CH4=0.25 and TR processes. By the contrary, the Cylindrical (1���3 ��m) catalysts showed the worst activity results for both processes. Section 4.5: Biogas reforming processes using Na+ and Cs+ doped Zeolites LTL based catalysts A method for the synthesis of Linde Type L (LTL) zeolite under microwave-assisted hydrothermal conditions and its behavior as a support for heterogeneously catalyzed hydrogen production is described in this section. Then, rhodium and nickel-based bimetallic catalysts were prepared in order to be tested by DR process and BOR process at O2/CH4=0.25. Moreover, the characterization of the catalysts under investigation was also carried out. Higher activities were achieved by the catalysts prepared from the non-doped zeolites, Rh-Ni/D and Rh-Ni/N, as compared to the ones supported on Na+ and Cs+ exchanged supports. However, the differences between them were not very significant. In addition, the Na+ and Cs+ incorporation affected mainly to the Disc catalysts. Comparing the results obtained by these catalysts with the ones studied in the section 4.4, in general worst results were achieved under DR conditions and almost the same results when operated under BOR conditions. In Chapter 5 the ethylene glycol (EG) as feed for syngas production by steam reforming (SR) and oxidative steam reforming (OSR) was studied by using microchannel reactors. The product composition was determined at a S/C of 4.0, reaction temperatures between 625��C and 725��C, atmospheric pressure and Volume Hourly Space Velocities (VHSV) between 100 and 300 NL/(gcath). This work was divided in two sections. The first one corresponds to the introduction of the main and most promising EG production routes. Then, the new experimental procedure is detailed and the information about the experimental set-up and the measured parameters is described. The characterization was carried out using the same techniques as for the previous chapter. Then, the next sections correspond to the catalytic activity and catalysts characterization results. Section 5.3: xRh-cm and xRh-np catalysts for ethylene glycol reforming Initially, catalysts with different rhodium loading, from 1.0 to 5.0 wt. %, and supported on ��-Al2O3 were prepared by two different preparation methods (conventional impregnation and separate nanoparticle synthesis). Then, the catalysts were compared regarding their measured activity and selectivity, as well as the characterization results obtained before and after the activity tests carried out. The samples prepared by a conventional impregnation method showed generally higher activity compared to catalysts prepared from Rh nanoparticles. By-product formation of species such as acetaldehyde, ethane and ethylene was detected, regardless if oxygen was added to the feed or not. Among the catalysts tested, the 2.5Rh-cm catalyst was considered the best one. Section 5.4: 2.5Rh-cm catalyst support modification with CeO2 and La2O3 In this part of the Chapter 5, the catalyst showing the best performance in the previous section, the 2.5Rh-Al2O3 catalyst, was selected in order to be improved. Therefore, new Rh based catalysts were designed using ��-Al2O3 and being modified this support with different contents of CeO2 or La2O3 oxides. All the catalysts containing additives showed complete conversion and selectivities close to the equilibrium in both SR and OSR processes. In addition, for these catalysts the concentrations measured for the C2H4, CH4, CH3CHO and C2H6 by-products were very low. Finally, the 2.5Rh-20Ce catalyst was selected according to its catalytic activity and characterization results in order to run a stability test, which lasted more than 115 hours under stable operation. The last chapter, Chapter 6, summarizes the main conclusions achieved throughout this Thesis work. Although very high reactant conversions and rich hydrogen mixtures were obtained using a fixed bed reaction system, the use of microreactors improves the key issues, heat and mass transfer limitations, through which the reforming reactions are intensified. Therefore, they seem to be a very interesting and promising alternative for process intensification and decentralized production for remote application.

Higher order vortex gyrotropic modes in circular ferromagnetic nanodots

Magnetic vortex that consists of an in-plane curling magnetization configuration and a needle-like core region with out-of-plane magnetization is known to be the ground state of geometrically confined submicron soft magnetic elements. Here magnetodynamics of relatively thick (50-100 nm) circular Ni80Fe20 dots were probed by broadband ferromagnetic resonance in the absence of external magnetic field. Spin excitation modes related to the thickness dependent vortex core gyrotropic dynamics were detected experimentally in the gigahertz frequency range. Both analytical theory and micromagnetic simulations revealed that these exchange dominated modes are flexure oscillations of the vortex core string with n = 0,1,2 nodes along the dot thickness. The intensity of the mode with n = 1 depends significantly on both dot thickness and diameter and in some cases is higher than the one of the uniform mode with n = 0. This opens promising perspectives in the area of spin transfer torque oscillators.

Euskarazko denbora-egiturak etiketatzeko gidalerroak v2.0

[EN]To interpret the temporal information on texts, a mark-up language that will code that information is needed, in order to make that information automatically reachable. The most used mark-up language is TimeML (Pustejovsky et al., 2003), which has also been choosen for Basque. In this guidelines we present the Basque version of ISO-TimeML (ISO-TimeML working group, 2008). After having analysed the tags, attributes and values created for English, we describe the most appropriate ones to represent Basque time structures��� information.

Desarrollo de recubrimientos inteligentes de base de metales de transici��n

Este trabajo tiene como objetivo estudiar las propiedades estructurales y magn��ticas de diferentes pel��culas delgadas anis��tropas de permalloy. Algunas de las muestras a estudiar han sido depositadas con diferentes velocidades de deposici��n, y otras de ellas se han depositado sobre diferentes capas de base sobre el sustrato. Todas ellas han sido producidas mediante pulverizaci��n cat��dica.

Magnetoimpedancia en sistemas homog��neos y heterog��neos

La magnetoimpedancia (MI) se define como el gran cambio en la impedancia el��ctrica que sufren los materiales ferromagn��ticos cuando son expuestos a un campo magn��tico externo. Este fen��meno es causado por la dependencia de la permeabilidad del material con el campo magn��tico, la cual causa variaciones en la profundidad de penetraci��n (��) de las corrientes que fluyen por la muestra. Esto se conoce como efecto pelicular o skin effect. Los materiales ferromagn��ticos blandos tienen alta permeabilidad y baja coercitividad, y por tanto estrechos ciclos de hist��resis. Entre ellos se encuentra el permalloy (Py), una aleaci��n de hierro y n��quel (Fe_20 Ni_80). Siendo este el principal material de investigaci��n del presente trabajo, se tratar�� de dar primero un estudio anal��tico del fen��meno de la MI para muestras en forma de hilo, as�� como pel��culas delgadas (monocapas y tricapas). Las herramientas utilizadas de c��mputo son MATLAB y FEMM para el apartado que a simulaciones se refiere. El trabajo incluye una segunda parte experimental. Mediante LabVIEW, con los instrumentos y t��cnicas adecuadas, el efecto de la MI puede ser debidamente cuantificado, y es precisamente el objetivo final de este an��lisis la comparaci��n de los resultados experimentales con las simulaciones.

Aplicaci��n de nuevas tecnolog��as a la ense��anza

La aplicaci��n de las nuevas tecnolog��as de la informaci��n y las comunicaciones (NTIC) en la ense��anza se presenta, a menudo,como una innovaci��n metodol��gica. Sin embargo, nuestra participaci��n en algunas experiencias como tutores y estudiantes nos lleva a afirmar que no existe una metodolog��a de ense��anza espec��fica para este entorno. En este art��culo se hace una revisi��n cr��tica de potencialidades y limitaciones de las NTIC en la ense��anza, y se defiende incorporar las NTIC como complemento a la actividad docente universitaria cl��sica. En ese contexto, se argumentar�� que la incorporaci��n de herramientas multimedia y de comunicaci��n ha de basarse en un an��lisis exhaustivo de todos los elementos que constituyen la formaci��n, proponi��ndose finalmente una metodolog��a para el desarrollo de complementos formativos.

Hacia la adaptaci��n al cr��dito europeo en aut��matas y lenguajes formales

Durante el curso 2006-2007 la asignatura Aut��matas y Lenguajes Formales se ha incorporado al proyecto SICRE (Seguimiento para la Introducci��n de los CR��ditos Europeos). El presente documento recoge cu��l ha sido la orientaci��n de la asignatura, principalmente en cuanto a actividades realizadas y resultados de las mismas.

Complemento pr��ctico en la ense��anza de lenguajes formales usando las expresiones regulares en el contexto de aplicaciones web

Tradicionalmente la ense��anza de los aut��matas y lenguajes formales basa su principal aplicaci��n pr��ctica en la construcci��n de compiladores. Sin embargo, las tareas de dise��o y programaci��n necesarias son excesivamente complejas como para que los estudiantes, que est��n cursando el tercer cuatrimestre de la Ingenier��a, puedan abordarlas con el rigor necesario. Es posible incorporar otro enfoque pr��ctico, real y m��s actual de las expresiones regulares en estas asignaturas, aprovechando su frecuente uso como herramienta de especificaci��n de patrones a la hora de dise��ar formularios de entrada de datos en diferentes contextos y, particularmente, en aplicaciones web de tres capas. El hecho de trabajar esta competencia junto con el desarrollo te��rico de las expresiones regulares permite a los estudiantes ser conscientes de la importante utilidad pr��ctica de este concepto, sin restringirlo a otros usos m��s cl��sicos relacionados con el dise��o de procesadores de textos o analizadores l��xicos. Durante el curso 2006-07 se ha propuesto a los estudiantes de Ingenier��a T��cnica en Inform��tica de Sistemas de la Universidad del Pa��s Vasco desarrollar fragmentos de c��digo basados en una notaci��n formal para resolver problemas de reconocimiento de patrones. La experiencia se ha llevado a cabo utilizando concretamente la notaci��n, inspirada en las expresiones regulares, de JavaScript, resultando viable, efectiva y bien valorada por parte de los estudiantes.

Documentos de soporte para una pr��ctica interuniversitaria de bases de datos

Este informe recoge la documentaci��n generada para llevar a cabo una pr��ctica interuniversitaria en el ��rea de base de datos durante los cursos 09/10 y 10/11. Se ha desarrollado una experiencia entre la UPV/EHU y la Universidad de la Rioja incorporando de forma sistem��tica la telecolaboraci��n, formando equipos de trabajo con estudiantes de las dos universidades que no se conocen entre s�� y han trabajado a distancia. El proyecto se ha realizado en el ��mbito de dos asignaturas de bases de datos concretas, una de cada universidad, donde las similitudes y diferencias entre ambas producen equipos heterog��neos. Los alumnos han colaborado en las diferentes fases de la creaci��n de una base de datos, desde la invenci��n de unos requisitos hasta la realizaci��n de consultas. Para el desarrollo de esta pr��ctica se han elaborado enunciados detallados para cada fase con ejemplos del trabajo a realizar. Adem��s se ha acordado una r��brica de evaluaci��n y una encuesta para valorar la experiencia. En el presente documento se recopila dicho material de soporte.