Dissertations / Theses on the topic 'Glass(y)'

A simple and accurate multisheet Brewster angle measurement technique has been developed to measure substrate indices. Both K$ sp+$ and Ag$ sp+$ ion-exchanged optical waveguides in glass substrates were characterized for infrared wavelengths $ lambda=1.152$ and 1.523$ mu m.$ For the characterization of Ag$ sp+$ ion-exchange waveguide, the WKB method has been modified to handle the index truncation point at the waveguide boundary inside the substrate accurately. An explicit and stable finite-difference vector beam propagation method has also been developed for efficient numerical simulations of the guided-wave optical devices.<br>A modified Y-branch wavelength multi/demultiplexer (abbreviated as WDM) for $ lambda=1.31$ and 1.55 $ mu m$ was designed and optimized by the beam propagation method (abbreviated as BPM). The device, made by K$ sp+$ ion-exchange in glass with a sputtered Al$ rm sb2O sb3$ strip on one branch, can provide high extinction ratios and wide bandwidth. It was successfully fabricated. The measured results of over 20db extinction ratio agree well with the BPM design simulations. A new Y-branch WDM made by K$ sp+$ and Ag$ sp+$ ion-exchanges was proposed and fabricated. It eliminates a difficult fabrication process, involving an Al$ rm sb2O sb3$ strip waveguide, and still provides the other merits of the first device. Its feasibility has been experimentally established. To simplify the fabrication process further, an asymmetric Mach-Zehnder WDM by one step ion-exchange for both two-wavelength and three-wavelength ($ lambda=0.98 mu$m being the third wavelength) was proposed. The BPM simulations show some improvements in several aspects over other types of demultiplexers.

A repetitive low-pressure die casting technique has been developed for casting high quality Mg6SCU2SY10 bulk metallic glass (BMG) samples. Using these as-cast samples, the thermal and mechanical behaviour of the BMG in the supercooled liquid (SCL) region was investigated principally by uniaxial tensile testing, differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Using the die casting facility, charge temperature, injection pressure and injection velocity were found to be important parameters for controlling the length, porosity and degree of crystallinity in the as-cast samples. A processing map was generated which showed that a melt temperature and casting pressure in the range 560-580°C and 0.4-0.5 bar, respectively, generated the highest quality samples. The static crystallization behaviour of the as-cast BMG was investigated in detail. It was found that the kinetics of both anisothermal and isothermal crystallization were adequately represented by a number of transformation models. Using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) relation in conjunction with isothermal DSC, the Avrami exponent was found to vary from 2.2 to 2.5 with increasing annealing temperature which implies that, at high annealing temperatures, nucleation occurs at a constant rate accompanied by diffusion-controlled growth of spherical grains. A comparable Avrami exponent of 2.34 was also calculated by anisothermal DSC using the Ozawa method. The tensile flow behaviour of the BMG was investigated over a range of strain rates (10.3to 10.1S•1) and deformation temperatures (150 to 170 QC) in the SCL region using standardized tensile test samples. It was found that, the flow stress increased rapidly to a maximum value followed by a decrease to a very low steady-state value. In the SCL region, the relationship between peak flow stress, strain rate and absolute deformation temperature was described adequately by the classic Sellars-Tegart constitutive relationship. There was also a good correlation between the Zener-Hollomon parameter, Z, and the flow characteristics of the BMG such as the transition from Newtonian to non-Newtonian flow at Z>1 031 S•1 and optimum superplasticity for Z-values in the range 5 x 1030 to 5 x 1031 S•1 where tensile elongations in excess of 1400% were achieved.

This doctoral thesis has been carried out at the company VAC-TRON S.A., together with the Department of Materials Science and Engineering of Universitat Politècnica de Catalunya, in the Besós (EEBE) and Vilanova i la Geltrú (EPSEVG) campus, with the support of the Industrial Doctorate Plan of the Secretariat for Universities and Research of the Department of Business and Knowledge of the Generalitat de Catalunya. The scientific and technological interest that justifies this research line answers the concern to know, characterize and improve the products manufactured by glass to metal seal, achieving a knowledge scientifically based that allows optimizing the current way of working in the company. The technology of glass-metal sealing consists of the manufacture of hermetic components, composed of a metal base, a glass preform and metal pins, which are joined by heating the glass to practically a melting state, allowing it to join to metal parts. The bond generated must be hermetic and must guarantee the electrical resistivity of the glass. Glass is the most important part of the three latter components, being responsible to generate a hermetic seal. Its main properties have been analyzed, such as: characteristic temperatures, chemical composition, particle size and microstructure. The results obtained allowed to differentiate the two most commonly used glasses, borosilicate and sodalime, relating the difference in compositions with the sealing temperature of each glass, as well as the increase in this temperature as the heating rate increases. Once the properties of the analyzed glasses are known, the glass-metal seal has been studied according to the design of the piece and the materials used. Then the hermeticity and electrical resistance of the samples were verified and their behavior as a function of temperature and external mechanical stress were studied. The temperature cycles showed that there is no significant change in the properties of sodalime glasses, while in borosilicate glasses decreased their hermeticity after temperature cycle, when the metal body had lower thickness. On the other hand, pressure tests have shown that the height of the glass was important, breaking at the bending limit of the glass. In addition, it has been found that the critical seal is the one formed with the base. As well, thesmaller the glass diameter, the more pressure the piece resists. These results were used to perform a series of numerical simulations to obtain the rupture pressures. Some results were coincident with the simulation but others no. Once the factors that influence the piece performance were known, new metallic materials for the bases have been studied, such as aluminum or titanium, which allow the company to enter new markets. With these new materials, it was necessary to determine the sealing curve and find the right glass to achieve the required tightness and electrical resistance. Solutions were found for both metals, although with certain limitations. In the case of titanium, the required electrical resistance was not attained by the glass, while in the aluminum case, the temperature cycles requirements were not achieved Finally, the evaluation of other alternative manufacturing methods for the metal bases was carried out. Metallic samples obtained by powder metallurgy and through the MIM and MEAM processes were studied. Because the samples manufactured by powder metallurgy and MIM were commercial ones, in which it was not possible to modify their manufacturing conditions, the results have been unfavorable, while with the samples manufactured by additive metal extrusion (MEAM), a proper seal was achieved.<br>Esta tesis doctoral se ha llevado a cabo en la empresa VAC-TRON S.A. juntamente con el departamento de Ciencia e Ingeniería de Materiales de la Universitat Politècnica de Catalunya en su sede del campus del Besós (EEBE) y Vilanova i la Geltrú (EPSEVG), con el soporte del Plan de Doctorados Industriales de la Secretaría de Universidades e Investigación del Departamento de Empresa y del Conocimiento de la Generalitat de Catalunya. La tecnología del sellado vidrio-metal consiste en la fabricación de componentes herméticos, compuestos por una base metálica, una preforma de vidrio y unos pasadores metálicos, que se unen mediante el calentamiento del vidrio hasta prácticamente un estado de fusión, permitiendo que éste se una al metal. La unión generada debe ser hermética y debe garantizar la resistividad eléctrica del vidrio. El interés científico y tecnológico que justifica esta línea de investigación responde a la inquietud de conocer, caracterizar y mejorar los productos obtenidos mediante el sellado vidrio-metal, obteniendo una base de conocimientos científicos que permita optimizar la manera actual de trabajar en la empresa. De los tres componentes, el vidrio es el más importante, siendo el responsable de generar la unión hermética. Se han analizado propiedades como: temperaturas características, composición química, tamaño de partícula y microestructura. Los resultados obtenidos han permitido diferenciar los dos vidrios más utilizados, borosilicato y sodalime, relacionando la composición con la temperatura de sellado de cada vidrio, así como el aumento de esta temperatura al aumentar la velocidad de calentamiento. Conocidas las propiedades de los vidrios analizados, se ha estudiado la unión vidrio-metal según el diseño de la pieza y de los materiales utilizados. Comprobadas la hermeticidad y resistencia eléctrica de las muestras, se ha estudiado su comportamiento a cambios de temperatura y esfuerzos mecánicos. Los ciclos de temperatura determinaron que en los vidrios sodalime no se produce un cambio significativo de sus propiedades, mientras que los vidrios de borosilicato presentan una disminución de la hermeticidad después del ciclo de temperatura cuando la base metálica presenta un menor espesor. Por otro lado, los ensayos de presión han mostrado que la altura de vidrio es importante. Además, se ha comprobado que la unión crítica es la formada con la base, y qué cuanto menor sea el diámetro de vidrio, mayor presión resiste. Estos resultados se utilizaron para realizar una serie de simulaciones y obtener las presiones de rotura, aunque con ciertas diferencias con los resultados experimentales. Conocidos los factores que influyen en la pieza final, se han estudiado nuevos materiales metálicos para las bases, como el aluminio o el titanio, que permita a la empresa introducirse en nuevos mercados. Con estos nuevos materiales, ha sido necesario determinar la curva de sellado y encontrar el vidrio adecuado para conseguir la hermeticidad y la resistencia eléctrica requeridas. Se han encontrado soluciones para ambos metales, aunque con ciertas limitaciones. En el caso del titanio, el vidrio no presenta la resistencia eléctrica requerida, mientras que el vidrio sellado con aluminio no resiste los ciclos de temperatura requeridos por la normativa. Por último, se ha llevado a cabo la evaluación de otros métodos para la fabricación de las bases metálicas que puedan ser alternativos al mecanizado convencional, sobre todo para series pequeñas, disminuyendo el coste y tiempo de fabricación. Se han estudiado muestras metálicas obtenidas por pulvimetalurgia y mediante los procesos MIM y MEAM. Debido a que las muestras obtenidas por pulvimetalurgia y MIM eran muestras comerciales, en las que no era posible modificar sus condiciones de fabricación, los resultados han sido desfavorables, mientras que con las muestras obtenidas mediante fabricación aditiva por extrusión de metal<br>Ciències i enginyeria de materials

Informe de Seminario para optar al grado de Licenciada en Lengua y Literatura Inglesa<br>The urban subject has been a matter of frequent discussion among writers from different ages and origins. In the present, we cannot conceive an exploration of human subjectivity without taking into account the urban experience. The contemporary self is, in fact, an urban self. Under that vein, "the city and the urban subject" is the main object of study of the seminar that frames this thesis. The work that has been chosen for the exploration of the urban experience is Paul Auster´s novel, City of Glass written in 1985, and part of The New York Trilogy. The reason behind this choice is that the novel posits a search for identity in an urban context, specifically in New York City. This well known metropolis can be said to be an icon of the American tradition, it has inscribed their history in it, and it is, at the same time, a tissue of experiences and perceptions that continually interweave through time. Naturally, as time goes on, people change, perceptions change, and the urban environment also changes. But in spite of this obvious transformation that affects almost everything, New York included, some people prefer consistency, regularity and uniformity, like the main character of City of Glass.

L'objectif principal de ce travail est de développer une nouvelle vitrocéramique structurée par NASICON avec une conductivité Li-ion élevée. Par conséquent, ce travail présente une nouvelle série de compositions de type NASICON sur la base du système Li1+xCrx(GeyTi1-y)2-x(PO4)3. Dans un premier temps, une composition spécifique de ce système a été synthétisée par la méthode de fusion et refroidissement rapide, suivie d'une cristallisation. Le comportement de cristallisation du verre précurseur a été examiné par calorimétrie différentielle à balayage et spectroscopie infrarouge. Les principaux résultats indiquent que le verre précurseur présente une nucléation homogène, a une stabilité de verre considérable et cristallise une phase de type NASICON, qui permet d'obtenir des électrolytes solides par voie vitrocéramique. Dans une deuxième étape, on examine l'effet de la substitution de Ti par Cr et Ge sur la stabilité de verre du verre précurseur, sur les paramètres structuraux de la phase cristalline NASICON et sur les propriétés électriques des vitrocéramiques. Par conséquent, un ensemble de seize compositions de ce système est synthétisé. Les principaux résultats indiquent que la stabilité de verre augmente lorsque Ti est remplacé par Ge et Cr. Après cristallisation, toutes les vitrocéramiques présentent une phase de type NASICON, et leurs paramètres de maille décroissent avec Ge et augmentent avec la teneur en Cr, ce qui permet de régler le volume de la cellule unitaire de la structure de type NASICON. De plus, la conductivité ionique et l'énergie d'activation pour la conduction du lithium dans les vitrocéramiques dépendent notamment du volume de la cellule unitaire de la structure de type NASICON. Enfin, la fenêtre de stabilité électrochimique de la vitrocéramique à structure NASICON de conductivité ionique la plus élevée est étudiée. Les mesures de voltampérométrie cyclique sont suivies par spectroscopie d'impédance électrochimique in situ, permettant de déterminer l'effet des réactions d'oxydation et de réduction sur les propriétés électriques des vitrocéramiques en question. La spectroscopie photoélectronique par rayons X, à son tour, est appliquée pour déterminer quelles espèces chimiques subissent une réduction/oxydation. Nos résultats révèlent que la stabilité électrochimique de ce matériau est limitée par la réduction des cations Ti+4 dans les faibles potentiels et par l'oxydation des anions O-2 dans les hauts potentiels. Aux hauts potentiels, un comportement similaire a également été rencontré pour d'autres conduites Li-ion de type NASICON bien connues, suggérant que le comportement électrochimique dans les potentiels oxydatifs pourrait être généralisé pour les phosphates à structure NASICON<br>The primary goal of this work is to develop a new NASICON-structured glass-ceramic with high Li-ion conductivity. Therefore, this work introduces a new series of NASICON-type compositions based on the Li1+xCrx(GeyTi1-y)2-x(PO4)3 system. At first, a specific composition of this system is synthesized by the melt-quenching method, followed by crystallization. The crystallization behavior of the precursor glass is examined by differential scanning calorimetry and infrared spectroscopy. The main results indicate that the precursor glass presents homogeneous nucleation, has considerable glass stability and crystallizes a NASICON-like phase, which allows solid electrolytes to be obtained by the glass-ceramic route. As a second step, we examine the effect of substituting Ti by Cr and Ge on the glass stability of the precursor glass, on the structural parameters of NASICON-like phase and the electrical properties of the glass-ceramics. Hence, a set of sixteen compositions of this system is synthesized. The main results indicate that the glass stability increases when Ti is replaced by Ge and Cr. After crystallization, all the glass-ceramics present NASICON-like phase, and their lattice parameters decrease with Ge and increase with Cr content, making it possible to adjust the unit cell volume of the NASICON-type structure. Furthermore, the ionic conductivity and activation energy for lithium conduction in the glass-ceramics are notably dependent on the unit cell volume of the NASICON-type structure. Finally, the electrochemical stability window of the NASICON-structured glass-ceramics of highest ionic conductivity is investigated. Cyclic voltammetry measurements are followed by in situ electrochemical impedance spectroscopy, enabling the effect of oxidation and reduction reactions on the electrical properties of the glass-ceramics in question to be determined. X-ray photoelectron spectroscopy, in turn, is applied to determine which chemical species undergo reduction/oxidation. Our findings reveal that the electrochemical stability of this material is limited by the reduction of Ti+4 cations in low potentials and by the oxidation of O-2 anions in high potentials. At high potentials, similar behavior is also encountered for other well-known NASICON-like Li-ion conducting suggesting that the electrochemical behavior in oxidative potentials could be generalized for NASICON-structured phosphates

Las marcas viales constituyen la única guía óptica que en muchas ocasiones tienen los usuarios de la vía, su correcta aplicación y conservación nos puede llegar a determinar la gravedad de un accidente hasta el punto de poder llegar a evitarlo. Por tanto, el correcto mantenimiento y repintado de la señalización vial horizontal en las carreteras convencionales a nivel mundial y de la red viaria española en particular, la investigación en nuevas combinaciones de materiales y el estudio de su durabilidad dependiendo del posicionamiento que ocupa la marca vial en carretera, nos aportan, sin duda, un apoyo útil para progresar en la lucha contra la accidentalidad vial. Por ese motivo, se ha investigado, no sólo la evolución temporal de las características fundamentales de la señalización vial horizontal como son: la visibilidad diurna, la visibilidad nocturna y la resistencia al deslizamiento de nuevas combinaciones de materiales de post-mezclado y materiales base, como es la pintura fosforescente; sino que, al mismo tiempo, se ha elaborado una relación y un estudio de la vida útil de la marca vial atendiendo a sus características fundamentales según la zona de la calzada que ocupa esa marca vial, estableciendo las pautas de comportamiento de las mismas y cuándo reemplazarlas por no cumplir con los criterios mínimos de aceptación, relacionando la sección de desgaste a cada una de las marcas viales que podemos encontrar en las carreteras convencionales de la red viaria española. Para ello, hemos elaborado un testing ground (TG1), en la carretera CV-904, con un total de 36 samples, teniendo para cada sentido de circulación 18 combinaciones de materiales atendiendo a material base y material de post-mezclado (microesferas de vidrio, cargas antideslizantes no transparentes y grano de vidrio transparente), y a su sistema de aplicación (monolayer o bilayer). Además, hemos ejecutado un segundo testing ground (TG2), en la ronda interna de la propia Universidad de Alicante, donde, partiendo de los conocimientos obtenidos en el primer estudio, se han fabricado nuevas combinaciones de materiales incluyendo el material base, diferentes tipos de microesferas de vidrio y cargas antideslizantes como parte del material de post-mezclado, se ha añadido pintura con pigmentos fosforescentes para mejorar la visibilidad nocturna y barniz de recubrimiento premezclado con agregados antideslizantes para prolongar la vida útil de la marca vial, fabricando un total de 40 samples analizadas en laboratorio. No sólo se han estudiado los resultados de los parámetros fundamentales de cada sample, sino que nos hemos apoyado en la toma de fotografías in situ analizándolas cualitativamente, lo que nos ha ayudado a comprender su evolución y los resultados. Al mismo tiempo hemos tomado muestras de todas ellas para su observación en laboratorio. Tras la comparativa entre la evolución de cada característica principal de las probetas y su análisis, hemos establecido los períodos de la vida útil de cada una de ellas según la zona de afección en la que están ubicadas atendiendo a la Norma 8.2-IC. Cabe destacar que se ha dejado la línea de investigación relacionada con la interconexión entre el vehículo autónomo, la infraestructura viaria y la señalización vial horizontal abierta como principal futura línea de investigación.

[ES] En el ámbito de los materiales compuestos o composites para la construcción, el cemento reforzado con fibras de vidrio (GRC, del inglés glass fiber reinforced cement) es el más extensamente utilizado, por sus excelentes propiedades mecánicas (resistencia a flexión y tenacidad). Sin embargo, la durabilidad de estos composites se ha demostrado crítica, y es necesario proponer alternativas. Las fibras usadas, de carácter álcali-resistente (fibras AR, formadas por agrupación de filamentos), son atacadas por el medio agresivo que impone el cemento hidratado. Una alternativa interesante, desde el punto de vista tecnológico, es la incorporación de materiales cementantes suplementarios de carácter puzolánico. El objetivo del presente trabajo es estudiar la influencia de las diferentes adiciones activas en morteros de GRC, observando el comportamiento de los elementos constitutivos del material en condiciones normales de curado, y también al ser sometidos a procesos de envejecimiento controlado. Asimismo, se analiza el comportamiento de los nuevos composites sometidos a diferentes medios agresivos, evaluando la durabilidad y la mejora de los compuestos por medio de la determinación de sus propiedades mecánicas, químicas y físicas. Se han elaborado probetas de GRC a través del procedimiento de premezcla (premix) y se han determinado sus propiedades mecánicas (resistencia a flexión, tenacidad y módulo de elasticidad). Adicionalmente, se han cuantificado las ganancias de resistencia al comparar composites GRC basados en cemento Portland (especímenes control) con otros en los que se ha sustituido hasta el 60% de dicho cemento por adiciones puzolánicas. Al objeto de mejorar la reactividad de las puzolanas, en algunos casos se ha implementado un aumento de su finura a través de la molienda (cenizas volantes molidas, CVm) o de procesos de sonicación (humo de sílice sonicado, HSS). Los especímenes de GRC han sido sometidos a un proceso de envejecimiento (tratamiento en agua a 55ºC durante un período prolongado) y se ha observado un empeoramiento muy importante de la resistencia a flexión y la tenacidad de aquellos que poseen solamente cemento Pórtland como componente cementante. Los composites GRC que contienen cantidades elevadas de puzolana (60% de CVm) o mezclas de puzolanas (50%CVm / 10%HSS, 50%CVm / 10%FCC) presentan una mejora sustancial de las propiedades mecánicas con respecto a los GRC control. La mejora de estos sistemas GRC con elevados porcentajes de puzolanas reactivas se han confirmado a través de estudios físicos y físico - químicos: evaluación de densidad, absorción, estudios microscópicos (lupa y microscopía electrónica de barrido) y análisis termogravimétrico. En cuanto a la respuesta de los composites GRC frente a diferentes disoluciones agresivas, se ha demostrado el efecto beneficioso de la presencia de puzolanas. Después de la exposición de los morteros de GRC a una disolución de NH4Cl, el comportamiento mecánico de los morteros puzolánicos se mantiene por encima del mortero GRC control: esto se debe a la relación directa existente con el incremento de la densidad y la disminución de grado de absorción del composite con la sustitución puzolánica. Al evaluar las propiedades de los morteros de GRC después de su exposición a una disolución de H2SO4, se observan diferencias muy importantes en la evolución de la masa, resistencia a flexión y tenacidad: los composites control son más afectados por la acidez del medio, de modo que la pérdida de masa es muy significativa si se compara con los GRC que presentan puzolanas. La estancia en la empresa Saint Gobain Vetrotex, ha permitido confirmar una gran similitud en los resultados obtenidos mediante los procedimientos seguidos en el laboratorio de la UPV (compuestos de GRC premezclado) comparados con las prácticas desarrolladas por el laboratorio de materiales de la empresa (composites de GRC proyectado). Se han evaluado<br>[CAT] En l'àmbit dels materials compostos o compòsits per a la construcció, el ciment reforçat amb fibres de vidre (GRC, de l'anglès glass fiber reinforced cement) és el més extensament utilitzat, per les seves excel·lents propietats mecàniques (resistència a flexió i tenacitat). No obstant això, la durabilitat d'aquests compòsits s'ha demostrat crítica, i cal proposar alternatives. Les fibres usades, de caràcter àlcali-resistent (fibres AR, formades per agrupació de filaments), són atacades pel medi agressiu que imposa el ciment hidratat. Una alternativa interessant des del punt de vista tecnològic és la incorporació de materials cimentants suplementaris de caràcter putzolànic. L'objectiu d'aquest treball és estudiar la influència de les diferents addicions actives en morters de GRC, observant el comportament dels elements constitutius del material en condicions normals de curat, i també quan son sotmesos a processos d'envelliment controlat. Així mateix, s'analitza el comportament dels nous compòsits sotmesos a diferents mitjans agressius, avaluant la durabilitat i la millora dels compostos mitjançant la determinació de les seves propietats mecàniques, químiques i físiques. S'han elaborat provetes de GRC a través del procediment de mescla prèvia (premix) i s'ha determinat les seves propietats mecàniques (resistència a flexió, tenacitat, mòdul d'elasticitat). Addicionalment s'han quantificat els guanys de resistència al comparar compòsits GRC basats en ciment Portland (espècimens control) amb altres en què s'ha substituït fins al 60% d'aquest ciment per materials putzolànics. A l'objecte de millorar la reactivitat de les putzolanes, en alguns casos s'ha implementat un augment de la seva finor a través de la mòlta (cendres volants mòltes, CVm) o de processos de sonicació (fum de sílice sonicat, HSS). Els espècimens de GRC han estat sotmesos a un procés d'envelliment (tractament en aigua a 55ºC durant un període prolongat) i s'ha observat l'empitjorament molt significatiu de la resistència a flexió i la tenacitat d'aquells que posseeixen solament ciment Pòrtland com a component cimentant. Els compòsits GRC que contenen quantitats elevades de putzolana (60% de CVm) o mescles de putzolanes (50% CVm / 10% HSS, 50% CVm / 10% FCC) presenten una millora substancial de les propietats mecàniques respecte als GRC control. La millora d'aquests sistemes GRC amb elevats percentatges de putzolanes reactives s'han confirmat a través d'estudis físics i fisicoquímics: avaluació de densitat, absorció, estudis microscòpics (lupa i microscòpia electrònica de rastreig) i anàlisi termogravimètric. Pel que fa a la resposta dels compòsits GRC enfront de diferents dissolucions agressives, s'ha demostrat l'efecte beneficiós de la presència de putzolanes. Després de l'exposició dels morters de GRC a una dissolució de NH4Cl, el comportament mecànic dels morters putzolànics es millor que el morter GRC control: això es deu a la relació directa existent amb l'increment de la densitat i la disminució del grau d'absorció del compòsit amb la putzolana. Quan s¿ha avaluat les propietats dels morters de GRC després de la seva exposició a una dissolució H2SO4, s'observen diferències molt importants en l'evolució de la massa, resistència a flexió i tenacitat: els compòsits control són més afectats per l'acidesa del medi, de manera que la pèrdua de massa és molt significativa si es compara amb els GRC que presenten putzolanes. L'estada a l'empresa Saint Gobain Vetrotex, ha permès confirmar una gran similitud en els resultats obtinguts mitjançant els procediments seguits en el laboratori de la UPV (compostos de GRC amb premescla) comparats amb les pràctiques desenvolupades pel laboratori de materials de l'empresa (compostos de GRC projectat). S'han avaluat prototips per a la indústria de l'GRC projectat.<br>[EN] In the field of composite materials for construction, glass fiber reinforced cement (GRC) is the most widely used, due to its excellent mechanical properties (resistance to bending and toughness). However, the durability of these composites has been demonstrated to be critical and alternatives need to be proposed. The used fibers, alkali-resistant (AR fibers, formed by grouping of filaments), are attacked by the aggressive medium imposed by the hydrated cement. An interesting alternative, from a technological point of view, is the incorporation of supplementary cementitious materials of pozzolanic behaviour. The purpose of this research is to study the influence of the different mineral additions in GRC mortars, observing the behaviour of the constituent elements of the material under normal curing conditions and controlled aging processes. Likewise, the behaviour of new composites subjected to different aggressive environments is analyzed, evaluating the durability and improvement of the compounds by determining their mechanical, chemical and physical properties. GRC specimens have been produced through the premix procedure and their mechanical properties (flexural strength, toughness, and modulus of elasticity) have been determined. Additionally, resistance gains have been quantified when comparing GRC composites based on Portland cement (control specimens) with others in which up to 60% of that cement has been replaced by pozzolanic additions. In order to improve the reactivity of pozzolans, in some cases an increase in its fineness has been implemented through grinding (ground fly ash, CVm) or sonication processes (sonicated silica fume, HSS). The GRC specimens have been subjected to an aging process (treatment in water at 55ºC for an extended period) and worsening of the flexural strength and toughness of those who only have Portland cement as cementitious component has been observed. GRC composites containing high amounts of pozzolan (60% CVm) or mixtures of pozzolans (50% CVm / 10% HSS, 50% CVm / 10% FCC) show a substantial improvement in mechanical properties compared to the control GRC. The improvement of these GRC systems with high percentages of reactive pozzolans have been confirmed through physical and physical-chemical studies: evaluation of density, absorption, microscopic studies (magnifying glass and scanning electron microscopy), and thermogravimetric analysis. Regarding the response of GRC composites against different aggressive solutions, the beneficial effect of the presence of pozzolans has been demonstrated. After the exposure of the GRC mortars to a NH4Cl solution, the mechanical behavior of pozzolanic mortars remains above that of the control GRC mortar: this is due to the direct relationship existing with the increase in density and the decrease in the absorption of the composite with the pozzolanic replacement. When evaluating the properties of GRC mortars after exposure to an H2SO4 solution, very important differences are observed in the evolution of the mass, flexural strength and toughness: the control composites are more affected by the acidity of the medium, so that the loss of mass is very significant when compared to the GRCs that present pozzolans. The stay at the Saint Gobain Vetrotex company has confirmed a great similarity to the results obtained by the procedures followed at the UPV laboratory (premixed GRC compounds) compared to the practices developed by the company's materials laboratory (composites of projected GRC). Scalable prototypes have been assessed for the projected GRC industry.<br>Lalinde Castrillón, LF. (2020). Estudio de compuestos de GRC y adiciones activas: Propiedades mecánicas, envejecimiento acelerado y durabilidad [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/157637<br>TESIS

Informe de Seminario para optar al grado de Licenciada en Lengua y Literatura Inglesa<br>Our objective is to visualize how Beckett show us the ideas explained before in “Murphy” and how he configured them and gave them form through the story and the characters. In order to do so, we will support our analysis with the concepts presented by the theory of chaos and the ideas developed by Jacques Derrida in his theory of Deconstruction. All this in order to understand the phenomena of contradiction presented as the central element in the novel. We also will see how the symbolism present in the novel is used as a way to reinforce and clarify this phenomenon and finally we will be able to see how we can identify our human condition through this novel.

Informe de Seminario para optar al grado de Licenciada en Lengua y Literatura Inglesa<br>Our seminar, ‘The city and the urban subject in British and American Literature’, revolved around the problem of cities and urban subjects, considering the relations they have with the metropolis and the way in which the constant flux of cities affects them. The consolidation of the cities created a space for new subjects, and new genres. But there is one element of these cities that caught my attention, and this is a shared element with the countryside, and a reminiscent idea of the early human communities. This is the house.

La presente tesis con título “Estudio de las diferencias entre hombres y mujeres en los estilos de liderazgo y su efecto en el acceso a puestos de dirección en la empresa Nexsys del Perú S.A.C”, identifica en qué tipo de liderazgo se encuentran las personas que ocupan cargos directivos según la Teoría de la Malla Gerencial del Enfoque de Rejillas. El estudio correspondió a un enfoque cuantitativo, en un nivel observacional descriptivo, prospectivo y transversal. Los métodos empleados fueron la encuesta según Blake & Mouton, y un cuestionario propio adaptado, que nos permitieron tener un enfoque respecto a las diferencias de género en los estilos de liderazgo y averiguar el motivo fundamental al acceso a cargos directivos en la organización. Las herramientas aplicadas se llevaron a cabo utilizando una población de dieciocho personas en puestos directivos entre veinticuatro a sesenta años de edad, laborando; y teniendo como cargo directivo, entre un mes a ocho años. La particularidad de la investigación radica en que es una empresa donde el 61.11% son mujeres y el 38.89% son hombres, siendo más de la mitad mujeres, incluyendo la Gerente General. Teniendo en cuenta los últimos informes de la Instituto Nacional de Estadística e Informática, la coyuntura social o variables sociales, influyen para que la mujer no se desempeñe laboralmente en la directiva de una organización, en el caso de Nexsys del Perú S.A.C, no aplica ya que hay más mujeres que hombres en los puestos directivos, descartando aquella costumbre que sólo los hombres lideren en las organizaciones.<br>The present thesis entitled "The study of the differences between men and women in leadership styles and their effect on access to management positions in Nexsys del Perú SAC", identifies in which type of leadership are people who hold management positions according to the Managerial Grid Model. The study corresponded to a quantitative approach, at a descriptive, prospective and transversal observational level. The methods used were the Blake & Mouton survey, and a self-adapted questionnaire, which allowed us to have a focus on gender differences in leadership styles and to find out the fundamental reason for access to management positions in the organization. The applied tools were carried out using a population of eighteen people in managerial positions between twenty-four to sixty years of age, working; and having as manager, from one month to eight years. The particularity of the investigation is that it is a company where 61.11% are women and 38.89% are men, with more than half women, including the General Manager. Taking into account the latest reports from the National Institute of Statistics and Informatics, the social situation or social variables, so that women do not work in the management of an organization, in the case of Nexsys del Perú SAC, does not apply because there are more women than men in management positions, discarding that custom that only men lead in organizations.

[EN] The present work examines the influence of the chemical structure of polymers on thermal, mechanical and dielectric behavior. The experimental techniques used for the purpose are differential scanning calorimetry, dynamo-mechanical analysis and dielectric spectroscopy. Additionally, in order to confirm the results obtained using the above methods, other techniques such as ray diffraction have also been employed. Chapters 1 and 2 contain the introduction and the objectives, respectively. Chapter 3 briefly describes the experimental techniques used. Chapter 4 contains the findings of the comparative analysis of the response to electrical noise fields for three poly(benzyl methacrylates) with different structures. The analysis was carried out under a wide range of frequencies and temperatures on three poly(benzyl methacrylates) containing two dimethoxy groups in positions 2,5-, 2,3- and 3,4-. The results show that the position of the dimethoxy groups on the aromatic ring has a significant effect on the molecular dynamics of poly(benzyl methacrylate). The spectra obtained were of high complexity and therefore, in order to perform a better analysis, numerical methods for time-frequency transformation including the use of parametric regularization techniques were used. We studied the effect of this structural change on the secondary relaxation processes and relaxation process &#61537;, relating to the glass transition. We also analyzed the effect of the dimethoxy group position on the formation of nanodomains, in which the side chains are predominant, and on the conduction processes of the materials tested. In Chapter 5, the conductivity of rubbery liquids was studied by analyzing poly(2,3-dimethoxybenzyl methacrylate), which exhibits its own particular behavior. The chapter analyzes the principle of time-temperature superposition, employing different interrelated variables. Chapter 6 focuses on how the presence of crosslinking affects the molecular mobility of polymethacrylates containing aliphatic alcohol ether residues. In this case, the effect of crosslinking on the secondary and primary relaxation processes was analyzed. The creation of nanodomains in the side chains as a result of the presence of crosslinking was also studied.<br>[ES] En este trabajo se presenta un estudio de la influencia de la estructura química de los polímeros en su comportamiento térmico, mecánico y dieléctrico. Las técnicas experimentales empleadas para ello han sido la calorimetría diferencial de barrido, el análisis dinamo-mecánico y la espectroscopia dieléctrica. Adicionalmente, se han empleado otras técnicas como la difracción de rayos, con objeto de corroborar los resultados obtenidos por las primeras. En los Capítulos 1 y 2 se recoge la introducción y los objetivos, respectivamente. El Capítulo 3 presenta una breve descripción de las técnicas experimentales empleadas. En el Capítulo 4 se recogen los resultados obtenidos en el análisis comparativo de la respuesta a campos de perturbación eléctrica en un amplio rango de frecuencias y temperaturas para tres polimetacrilatos de bencilo con dos grupos dimetoxi en posiciones 2,5-, 2,3- y 3,4-. Los resultados obtenidos señalan el importante efecto de la posición de los grupos dimetoxi en el anillo aromático, sobre la dinámica molecular del polimetacrilato de bencilo. Los espectros obtenidos fueron muy complejos, por ello en orden a llevar a cabo un mejor análisis se emplearon métodos numéricos para la transformación tiempo-frecuencia que incluyeron el uso de técnicas de regularización paramétrica. Se ha estudiado el efecto que dicho cambio estructural ejerce tanto sobre los procesos de relajación secundaria como sobre el proceso de relajación &#945;, relacionado con la transición vítrea. Así mismo, se ha analizado el efecto de la posición de los grupos dimetoxi en la formación de iii nanodominios en los que predominan las cadenas laterales, y su efecto en los procesos de conducción de los materiales analizados. En el Capítulo 5 se recoge el estudio de la conductividad de líquidos gomosos tomando como modelo el poli (metacrilato de 2,3-dimetoxibencilo), por su peculiar comportamiento. En este capítulo se ha realizado un análisis del principio de superposición tiempo-temperatura, empleando para ello diferentes variables relacionadas entre sí. En el Capítulo 6 se recoge el efecto de la presencia de entrecruzante en la movilidad molecular de polimetacrilatos que contienen residuos de éteres de alcoholes alifáticos. En este caso, se ha analizado el efecto de la presencia de entrecruzante tanto en los procesos de relajación secundarios, como en el proceso de relajación principal. También se llevó a cabo un análisis del efecto que la presencia de entrecruzante tiene sobre la creación de nanodominios gobernados por las cadenas laterales.<br>[CAT] En aquest treball es presenta un estudi de la influència de l'estructura química dels polímers en el seu comportament tèrmic, mecànic i dielèctric. Les tècniques experimentals utilitzades han sigut la calorimetria diferencial de rastreig, l'anàlisi dinamo-mecànic i l'espectroscòpia dielèctrica. Addicionalment, s'han empleat altres tècniques com la difracció de rajos X a fi de corroborar els resultats obtinguts per les primeres. En els Capítols 1 i 2 s'arreplega la introducció i els objectius, respectivament. Al Capítol 3 es presenta una breu descripció de les tècniques experimentals emprades. En el Capítol 4 es recull els resultats obtinguts en l'anàlisi comparativa de la resposta a camps de pertorbació elèctrica en un ampli rang de freqüències i temperatures de tres polimetacrilats de benzil amb dos grups metoxi en posicions 2,5-, 2,3- i 3,4-. Els resultats obtinguts assenyalen l'important efecte de la posició dels grups metoxi en l'anell aromàtic, sobre la dinàmica molecular del polimetacrilat de benzil. Els espectres obtinguts van ser molt complexos, per aquesta raó per a dur a terme un millor anàlisi es van emprar mètodes numèrics per a la transformació temps-freqüència que van incloure l'ús de tècniques de regularització paramètrica. S'ha estudiat l'efecte que el dit canvi estructural exerceix tant sobre els processos de relaxació secundària com sobre el procés de relaxació &#61537;, relacionat amb la transició vítria. Així mateix, s'ha analitzat l'efecte de la posició dels grups metoxi en la formació de nanodominis en els que predominen les cadenes laterals, i el seu efecte en els processos de conducció dels materials analitzats. En el Capítol 5 s'arreplega l'estudi de la conductivitat de líquids gomosos prenent com a model el poli-(metacrilat de 2,3-dimetoxibencilo), pel seu peculiar comportament. En aquest capítol s'ha realitzat un anàlisi del principi de superposició temps-temperatura, emprant per a això diferents variables relacionades entre sí. En el Capítol 6 s'arreplega l'efecte de la presència d'entrecreuat en la mobilitat molecular de polimetacrilats que contenen residus d'èters d'alcohols alifàtics. En aquest cas, s'ha analitzat l'efecte de la presència d'entrecreuat tant en els processos de relaxació secundaris, com en el procés de relaxació principal. També es va dur a terme un anàlisi de l'efecte que la presència d'entrecreuat químic té sobre la creació de nanodominis governats per les cadenes laterals.<br>Carsí Rosique, M. (2015). Molecular mobility. Structure-property relationship of polymeric materials [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59460<br>TESIS<br>Premiado

A zircônia estabilizada por ítria (Y-TZP) apresenta excelentes propriedades mecânicas; entretanto, sua microestrutura cristalina inerte faz com que tratamentos aplicados em porcelanas e vitrocerâmicas, como condicionamento com ácido fluorídrico e aplicação de compostos silânicos, sejam ineficazes para obter união aos cimentos resinosos. Neste trabalho, propõe-se uma alternativa para aumentar a reatividade da Y-TZP a cimentos resinosos por meio de um processo de modificação da superfície através da deposição de um filme vítreo. O objetivo deste estudo é, portanto, caracterizar um filme vítreo, sinterizado com diferentes ciclos térmicos, após deposição sobre Y-TZP (YZ 20/19, VITA Blocks Zahnfabrik, Bad Saackingen, Germany) e avaliar a resistência de união imediata e após ciclagem térmica (10.000 ciclos 5 e 55°C) a dois cimentos resinosos (Relyx Arc, 3M/ESPE, St. Paul, MN, USA e Rely-X U200 3M/ESPE, Neuss, Germany). A caracterização do filme foi efetuada por meio de microscopia eletrônica de varredura, para avaliar a morfologia; EDS (Espectroscopia por dispersão de energia), para estabelecer uma análise qualitativa e semi-quantitativa dos elementos químicos presentes e mensuração do ângulo de contato. Foram propostas as seguintes condições experimentais na superfície da YTZP: deposição dos filmes sinterizados à 700°C, 900°C ou ciclo de sinterização para o auto glaze; aplicação do primer contendo MDP (Alloy Primer, Kuraray Medical Inc, Kurashiki, Okayama, Japan); e silicatização da superfície (sistema Rocatec Soft, 3M/ESPE, St. Paul, MN, USA). Após o ensaio mecânico, o padrão de fratura foi avaliado por meio de microscopia óptica. Para os dados obtidos, o traço de Pillai (p = 0,00) mostrou que o tipo de tratamento empregado tem um efeito significativo sobre a resistência de união. Para determinar a diferença entre os grupos estudados foi aplicado um teste de comparações múltiplas (Tukey). O filme 900 apresentou maior resistência de união imediata (42,2 MPa), sendo este valor estatisticamente superior a silicatização (35,5 MPa) e MDP (28,0 MPa). Os resultados obtidos após termociclagem, mostram que o filme 900 novamente apresentou maior resistência de união (36,8 MPa) e também foi estatisticamente superior ao MDP (16,1 MPa) e silicatização (27,3MPa). A análise em microscópio estereoscópico demonstrou um padrão de fratura predominantemente coesiva na resina para microtração imediata para os grupos com deposição do filme vítreo e silicatizados. Para o MDP, o padrão de fratura foi, na sua maioria, do tipo mista. O ângulo de contato medido imediatamente após os tratamentos de superfície apresentou-se menor para os grupos com filme e silicatização e manteve-se com baixos valores somente para os grupos com filme após limpeza com álcool absoluto. A análise por EDS das superfícies dos filmes indicou a presença de silício nos diversos pontos analisados. Concluiu-se, deste modo, que a deposição do filme vítreo mostrou-se como um meio eficiente para promover uma forte e durável união com da Y-TZP com os cimentos resinosos, independente da temperatura de sinterização utilizada.<br>The yttria stabilized zirconia (Y- TZP) has excellent mechanical properties, however its inert crystalline microstructure makes treatments applied in porcelain and glass ceramics, such as hydrofluoric acid etching and application of silane compounds, are ineffective for the union resin cements. In this work, we propose an alternative to increase the reactivity of the Y- TZP resin cement by a process of surface modification by depositing a glass film. The aim of this study is therefore to characterize a glass film, sintered with different thermal cycles, after deposition on Y- TZP (YZ - 20/19, VITA Blocks Zahnfabrik, Bad Saackingen, Germany) and to evaluate the bond strength immediately after thermocycling (10.000 cycles 5 and 55°C) to two resin cements (Relyx Arc, 3M/ESPE, St. Paul, MN, USA and Rely - X U200 3M/ESPE, Neuss, Germany). The characterization of the glass film was performed by means of scanning electron microscopy to assess the morphology, EDS (Energy Dispersive Spectroscopy), to establish a qualitative and semi-quantitative chemical elements and measuring the contact angle. Been proposed the following experimental conditions on the surface of YTZP: deposition of films sintering at 700°C, 900°C or sintering cycle for VM9 self glaze; primer containing MDP (Alloy Primer, Kuraray Medical Inc., Okayama, Okayama, Japan) and silica coating surface (Rocatec Soft, 3M/ESPE, St. Paul, MN, USA) . After mechanical testing, the fracture pattern was evaluated by light microscopy. For data, the trace of Pillai (p = 0.00) showed that the type of treatment used has a significant effect on the bond strength. To determine the difference between groups was applied multiple comparison test (Tukey). The 900 film showed higher bond strength immediately (42.2 MPa), and this value was statistically superior to silica coat (35.5 MPa) and MDP (28.0 MPa). The results obtained after thermocycling, show that 900 film again showed highest bond strength (36.8 MPa) and was also statistically superior to MDP (16.1 MPa) and silica coating (27.3 MPa). The analysis in stereoscopic microscopes showed a pattern of predominantly cohesive fracture in the resin for immediate microtensile for groups with film deposition and silica coat. In the MDP, the fracture pattern was mostly of the mixed type. The contact angle measured immediately after the surface treatments was lower for groups with film and silica coat and remained with low values only for groups with film after cleaning with absolute alcohol. Analysis by EDS surfaces of the films indicated the presence of silicon at the various points analyzed. It was concluded therefore that the glass film deposition proved to be an efficient way to promote a strong and durable bond with Y- TZP with resin cements, regardless of sintering temperature used.

En la Tesis titulada “Las vidrieras góticas mediterráneas: composición química, técnica, estilo. El caso concreto de Barcelona y Siena en el siglo XIV” se pretende hacer un estudio comparado entre los conjuntos vítreos del área mediterránea, ejecutados desde finales del siglo XIII hasta mediados del siglo XIV, con especial atención al Monasterio de Pedralbes de Barcelona y a la Catedral de Siena (Italia). Asimismo por lo que se refiere al área catalana se analizan de manera crítica la Catedral de Girona, la Catedral de Tarragona y la Iglesia de Santa María del Mar de Barcelona; en Italia se compara la gran obra pictórica de Duccio di Buoninsegna con el antiguo conjunto vítreo de la Iglesia de San Giacomo Maggiore de Bolonia. Para esa finalidad se ha aplicado una innovadora metodología multidisciplinar donde el estudio histórico-artístico de las vidrieras, y documental, se ha complementado e interpretado gracias a los datos proporcionados por los análisis químico-analíticos de los materiales (vidrio, plomo y pintura).<br>In the text “Las vidrieras góticas mediterráneas: composición química, técnica, estilo. El caso concreto de Barcelona y Siena en el siglo XIV” is made a comparative study between Mediterranean stained glass windows, executed from XIII to XIV century, with special attention to Pedralbes Monastery (Barcelona) and the Cathedral of Siena (Italy). Regarding the Catalan area it critically analyzes the Church of Santa Maria del Mar in Barcelona and Cathedrals of Girona and Tarragona. In Italy is it compared the great paintings of Duccio di Buoninsegna with the stained glass windows of the Church of San Giacomo Maggiore in Bologna. For this purpose we have applied an innovative multidisciplinary approach where the history of art studies of stained glass, and the documentation, has been supplemented and interpreted by the analytical chemical analysis of materials (glass, lead, painting).

The system LiHo_<em>x</em>Y_1-<em>x</em>F₄ is a nearly perfect example of a dilute, dipolar-coupled Ising magnet and, as such, it is an ideal testing ground for many theories in statistical mechanics. At low holmium concentration (<em>x</em> = 0. 045) an unusual spin liquid or "anti-glass" state was discovered in previous work [1]. This state does not exhibit a spin glass freezing transition as is expected for a long-range interaction. Instead, it shows dynamics which are consistent with a collection of low-frequency oscillators [2]. It was also seen to have sharp features in its specific heat [3]. <br /><br /> We present heat capacity measurements on three samples at and around the concentration of the spin liquid state in zero magnetic field and in a temperature range from around 50 mK to 1 K. In contrast to previous measurements, we find no sharp features in the specific heat. The specific heat is a broad feature which is qualitatively consistent with that of a spin glass. The residual entropy as a function of <em>x</em>, obtained through a numerical integral of the data, however, is consistent with numerical simulations which predict a disappearance of spin glass ordering below a critical concentration of dipoles [4]. <br /><br /> Also presented here, is ac susceptibility data on an <em>x</em> = 0. 45 sample which exhibits a paramagnetic to ferromagnetic transition and is found to be consistent with previous work.

[ES] Las fibras ópticas son dispositivos muy utilizados en el campo de las telecomunicaciones desde su descubrimiento. En las últimas décadas, las fibras ópticas comenzaron a utilizarse como sensores fotónicos. Los primeros trabajos se centraron en la medición de unas dimensiones físicas en un punto específico. Posteriormente, surgió la posibilidad de medir las propiedades de la fibra óptica en diferentes puntos a lo largo de la fibra. Este tipo de sensores se definen como sensores distribuidos. Los componentes optoelectrónicos fueron desarrollados e investigados para telecomunicaciones. Los avances en las telecomunicaciones hicieron posible el desarrollo de sistemas de interrogación para sensores de fibra óptica, creciendo en paralelo con los avances de las telecomunicaciones. Se desarrollaron sistemas de interrogación de fibra óptica que permiten el uso de una única fibra óptica monomodo estándar como sensor que puede monitorear decenas de miles de puntos de detección al mismo tiempo. Los métodos que extraen la información de detección de la señal reflejada en la fibra óptica son los más empleados debido a la facilidad de acceso al sensor y la flexibilidad de estos sistemas. Los más estudiados son la reflectometría en dominios de tiempo y frecuencia. La reflectometría óptica en el dominio del tiempo (OTDR) fue la primera técnica utilizada para detectar la posición de los fallos en las redes de comunica-ción de fibra óptica. El OTDR sensible a la fase hizo posible detectar la elongación y la temperatura en una posición específica. Paralelamente, los gratings de Bragg (FBG) se convirtieron en los dispositivos más utilizados para implementar sensores en fibra óptica discretos. Se desarrollaron técnicas de multiplexación para realizar la detección en múltiples puntos utilizando FGBs. La reflectometría realizada interrogando arrays de FBG débiles demuestra que mejora el rendimiento del sistema en comparación al uso de una fibra monomodo. Los sistemas de interrogatorio actuales tienen algunos inconvenientes. Algunos de ellos son velocidad de interrogatorio limitada, grandes dimensiones y alto costo. En esta tesis doctoral se desarrollaron nuevos sistemas de interrogación y sensores de fibra óptica para superar algunos de estos inconvenientes. Los sensores de fibra óptica de plástico demuestran ser una plataforma innovadora para desarrollar nuevos sensores y sistemas de interrogación de bajo costo y fáciles de implementar para fibras de plástico comerciales. Se investigó la reflectometría en el dominio del tiempo y las técnicas fotónicas de microondas para la interrogación de una matriz de rejillas débiles que permitieron simplificar el sistema de interrogación para la detección de temperatura y vibración.<br>[CA] Les fibres òptiques són dispositius molt utilitzats en el camp de les telecomunica-cions des del seu descobriment. En les últimes dècades, les fibres òptiques van començar a utilitzar-se com a sensors fotònics. Els primers treballs es van centrar en el mesurament d'unes dimensions físiques en un punt específic. Posteriorment, va sorgir la possibilitat de mesurar les propietats de la fibra òptica en diferents punts al llarg de la fibra. Aquest tipus de sensors es defineixen com a sensors distribüits. Els components optoelectrònics van ser desenvolupats i investigats per a telecomunicacions. Els avanços en les telecomunicacions van fer possi-ble el desenvolupament de sistemes d'interrogació per a sensors de fibra òptica, creixent en paral·lel amb els avanços de les telecomunicacions. Es van desenvolupar sistemes d'interrogació de fibra òptica que permeten l'ús d'una única fibra òptica monomodo estàndard com a sensor que pot monitorar desenes de milers de punts de detecció al mateix temps. Els mètodes que extreuen la informació de detecció del senyal reflectit en la fibra òptica són els més utilitzats a causa de la facilitat d'accés al sensor i la flexibilitat d'aquests sistemes. Els més estudiats són la reflectometría en dominis de temps i freqüència. La reflectometría òptica en el domini del temps (OTDR) va ser la primera tècnica utilitzada per a detectar la posició de les fallades en les xarxes de comunicació de fibra òptica. El OTDR sensible a la fase va fer possible detectar l'elongació i la temperatura en una posició específica. Paral·lelament, els gratings de Bragg (FBG) es van convertir en els dispositius més utilitzats per a implementar sensors en fibra òptica discrets. Es van desenvolupar tècniques de multiplexació per a realitzar la detecció en múltiples punts utilitzant FGBs. La reflectometría realitzada interrogant arrays de FBG febles demostra que millora el rendiment del sistema en comparació a l'ús d'una fibra monomodo. Els sistemes d'interrogatori actuals tenen alguns inconvenients. Alguns d'ells són velocitat d'interrogatori limitada, voluminositat i alt cost. En aquesta tesi doctoral es van desenvolupar nous sistemes d'interrogació i sensors de fibra òptica per a superar alguns d'aquests inconvenients. Els sensors de fibra òptica de plàstic demostren ser una plataforma innovadora per a desenvolupar nous sensors i siste-mes d'interrogació de baix cost i fàcils d'implementar per a fibres de plàstic comercials. Es va investigar la reflectometría en el domini del temps i les tècniques fotòniques de microones per a la interrogació d'una matriu de reixetes febles que van permetre simplificar el sistema d'interrogació per a la detecció de temperatura i vibració.<br>[EN] Optical fibers are devices largely used in telecommunication field since their discovery. In the last decades, optical fibers started to be used as photonic sensors. The first works were focused on the measurement of physical dimensions to a specific point. Afterward, emerged the possibility to measure the optical fiber properties at different locations along the fiber. These kinds of sensors are defined as distributed sensors. The optoelectronic components were developed and investigated for telecommunications. The progress in telecommunication made possible the development of optical fiber sensors interrogation systems, growing in parallel with the advances of telecommunications. Optical fiber interrogation systems were developed to use a single standard monomode optical fiber as a sensor that can monitor tens of thousands of sensing points at the same time. The methods that extract the sensing information from the backscattered signal in the optical fiber are widely employed because of the easiness of access to the sensor element and the flexibility of these systems. The most studied are the reflectometry in time and frequency domains. The optical time domain reflectometry (OTDR) was the first technique used to detect the position of the failures in the optical fiber communication networks. Using phase sensitive OTDR it is possible to sense strain and temperature at a specific position. In parallel, fiber Bragg gratings (FBGs) became the most widely used devices to implement discrete optical fiber sensors. Multiplexing techniques were developed to perform multi points sensing using these gratings. The reflectometry performed interrogating weak FBGs arrays demonstrate to improve the performance of the system employing a single mode fiber. The interrogation systems nowadays have some drawbacks. Some of them are limited speed of interrogation, bulkiness, and high cost. New interrogation systems and optical fiber sensors were developed in this doctoral thesis to overcome some of these drawbacks. Plastic optical fiber sensors demonstrate to be an innovative platform to develop both new sensors and low cost, easy to implement interrogation systems for commercial plastic fibers. Reflectometry in time domain and microwave photonic techniques were investigated for the interrogation of weak gratings array allowed to simplify the interrogation system for the sensing of temperature and vibration.<br>I would like to greatly thank the European Union’s Horizon 2020 Research and Innovation Program that funded the research described in this thesis under the Marie Sklodowska-Curie Action Grant Agreement 722509.<br>Sartiano, D. (2021). Design of optical fiber sensors and interrogation schemes [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/161357<br>TESIS

La presente investigación realiza un análisis sobre las barreras del crecimiento profesional en las mujeres trabajadoras de entre 20 y 45 años en la ciudad de Lima Metropolitana, que ocupan puestos gerenciales y de mandos medios, basados en un caso de estudio en tres empresas del Grupo Romero: Corporación de Servicios GR S.A., Corporación Primax S.A. y Ransa Comercial S.A. Asimismo, se cuenta con la posición de expertos en temas sobre la igualdad de género y la participación del Estado. Los tres factores mencionados, las tres empresas de estudio, la posición de los expertos y el Estado, fueron analizados y comparados para evaluar si existen similitudes o diferencias para identificar las barreras que la mujer tiene que afrontar para desarrollarse profesionalmente. En el primer capítulo se define el tema, el problema, la hipótesis, el objetivo general y los objetivos específicos y se describe la situación problemática inicial de la investigación. El segundo capítulo desarrolla el marco teórico y la relevancia del estudio sobre el impacto económico y social que se obtendría en una sociedad donde la brecha de género no existiera. En el tercer capítulo se define la metodología que se utilizó para el desarrollo de la tesis. En el cuarto capítulo se menciona los hallazgos encontrados en el proceso de la investigación. Por último, se presentan las conclusiones que responde al objetivo general y los objetivos específicos realizados, así como las recomendaciones que se hacen para reducir la brecha de género.<br>This research analyzes the barriers to professional growth in working women between 20 and 45 years of age, in the city of Lima - Peru, which performs is managerial and middle management positions, this Study cases is based on three enterprise of Romero Group: Corporación de Servicios GR S.A., Corporación Primax S.A. y Ransa Comercial S.A Likewise, this is a perception of experts on issues of gender equality and participation of competent government authorities. The three mentioned factors, the three study companies, the position of the experts and the government, were analyzed and compared to assess if there are similarities or differences to identify the barriers that the woman has to face in order to develop professionally. In the first chapter the subject, the problem, the hypothesis, the general objective and the specific objectives are defined and the initial problematic situation of the investigation is described. The second chapter develops the theoretical framework and the relevance of the study on the economic and social impact that would be obtained in a society where the gender gap did not exist. In the third chapter the methodology that was used for the development of the thesis is defined. In the fourth chapter, the findings found in the research process are mentioned. Finally, conclusions are presented that respond to the general objective and the specific objectives, as well as the recommendations made to reduce the gender gap.<br>Tesis

Los suelos arcillosos tienen la característica de hincharse cuando son expuestos a la humedad y de contraerse cuando existe sequedad, esto representa un problema especialmente en las cimentaciones que se construyen sobre este tipo de suelo. Por ello, la presente investigación tiene como finalidad evaluar el efecto en las propiedades mecánicas al adicionar vidrio y valvas de molusco triturados a este suelo problemático. La presente tesis tuvo un enfoque cuantitativo, ya que el estudio del suelo arcilloso se realizó mediante la medición de indicadores tales como Corte directo, Proctor Modificado, Límites de Atterberg y Granulometría. Además, el uso del vidrio y valvas de molusco disminuirá los costos de mejoramiento del suelo arcilloso, ya que son materiales que se encuentran por abundancia en la zona de estudio. Y los costos para adquirir estos productos son mínimos. Con esta clase de mejora presentada en la investigación, el suelo arcilloso mejora notablemente, ya que este aumenta su capacidad de soporte. Los resultados muestran que el uso de las valvas de molusco y polvo de vidrio brindan un aumento de la resistencia del suelo arcilloso, además muestra una disminución de las deformaciones transversales que están presentes por la aplicación de cargas sobre el terreno arcilloso. Finalmente, se observó que, al combinar el suelo arcilloso con el polvo de valvas de molusco y polvo de vidrio, esta mezcla disminuye la absorción de agua, convirtiendo de esta manera más estable al terreno arcilloso.<br>Clayey soils have the characteristic of swelling when exposed to moisture and shrinking when there is dryness, this represents a problem especially in foundations that are built on this type of soil. Therefore, the purpose of this research is to evaluate the effect on mechanical properties by adding glass powder and mollusk shell powder to this problem soil. The present thesis had a quantitative focus, since the study of clay soil was carried out by measuring indicators such as Direct Cut, Modified Proctor, Atterberg Limits and Granulometry. In addition, the use of glass powder and mollusk shells will decrease the costs of clay soil improvement, since they are materials found in abundance in the study area. And the costs to purchase these products are minimal. With this kind of improvement presented in research, clayey soil improves markedly as it increases its bearing capacity. The results show that the use of mollusk shells and glass powder provide an increase in the resistance of the clay soil, in addition it shows a decrease in the transverse deformations that are present by the application of loads on the clay soil. Finally, it was observed that, when combining clay soil with shellfish powder and glass powder, this mixture decreases the absorption of water, thus making clay soil more stable.<br>Tesis

Desde a descoberta das ligas amorfas em 1960, os motivos pelos quais algumas ligas podem ser facilmente amorfizadas enquanto outras não podem, não é claramente conhecido, assim não há teoria universal para predizer a habilidade de formação vítrea em sistemas metálicos. No presente trabalho, um critério de seleção foi aplicado ao sistema Ni-Nb-Zr com o objetivo de predizer as melhores estequiometrias com as mais altas tendências de formação vítrea. As habilidades de formação vítrea das ligas foram avaliadas pelo parâmetro térmico &#947;m e os resultados mostraram uma pobre correlação com as predições. Este critério preditivo correlaciona as taxas de resfriamento para a formação vítrea com a instabilidade topológica de estruturas cristalinas, as diferenças médias de função trabalho e densidade eletrônica entre os elementos constituintes da liga. O parâmetro térmico depende de temperaturas características de transformações de fases que podem ser facilmente determinadas a partir de curvas de calorimetria exploratória diferencial dos vidros metálicos. As hipóteses iniciais para explicar a pobre correlação entre os resultados e as predições foram atribuídas às influências de fatores não considerados nos cálculos como os compostos intermetálicos desconhecidos e contaminação por oxigênio. Assim, algumas ligas solidificadas rapidamente foram investigadas com mais rigor com o objetivo de entender a formação das fases cristalinas que competem contra a formação vítrea. As fases cristalinas foram caracterizadas e comparadas com estruturas cristalinas encontradas na literatura como também alguns diagramas de fases. Os diagramas de fases foram utilizados como guias para o melhor entendimento do comportamento de cristalização. Em adição, o critério de seleção também foi utilizado para predizer o melhoramento da tendência de formação vítrea de uma liga do sistema Ni-Nb-Zr com pequenas adições dos elementos terras-raras Y ou Er. É bem conhecido que uma pequena adição de um elemento terra-rara apropriado pode aumentar significativamente a habilidade de formação vítrea de algumas ligas. As tendências de formação vítrea da liga base e das ligas dopadas com terras-raras também foram avaliadas pelo parâmetro térmico &#947m e os resultados concordaram muito bem com a tendência predita pelo cálculo. As amostras amorfas volumosas foram produzidas por injeção em molde de cobre. A natureza amorfa foi analisada por difração de raios-X e calorimetria exploratória diferencial. As fases cristalinas foram analisadas por microscopia eletrônica de transmissão, microscopia eletrônica de varredura, espectroscopia de raios-X por dispersão em energia e difração de raios-X. A contaminação por oxigênio foi quantificada pelo método de fusão em gás inerte.<br>Since the discovering of amorphous alloys in 1960, the actual causes of why some alloys can be easily formed into glasses while others cannot, are not clearly known, thus there is no universal theory to predict the glass forming ability in metallic systems. In the present work, a selection criterion was applied in the Ni-Nb-Zr system in order to predict the best stoichiometries with high glass forming ability. The actual glass forming ability of alloys were evaluated by the thermal parameter &#947;m and the results have shown a poor correlation with the predictions. This criterion correlates critical cooling rate for glass formation with topological instability of stable crystalline structures; average work function difference and average electron density difference among the constituent elements of the alloy. The thermal parameter depends on the characteristic temperatures of phase transformations which can be easily measured from differential scanning calorimetry curves of metallic glasses. The initial hypotheses to explain the poor correlation between the experimental results and the predictions concerned with the influence of factors not considered in the calculation, such as unknown intermetallic compounds and oxygen contamination. Thus some rapidly quenched alloys were investigated with more accuracy in order to understand the formation of crystalline phases which compete against the glass formation. We characterized the crystalline phases and compared them to crystalline structures found in literature as well as some phase diagrams. The phase diagrams were used as guides in order to understand the crystallization behavior. In addition, the selection criterion also was used to predict the glass forming ability improvement of a Ni-Nb-Zr alloy with minor additions of rare-earth elements Y or Er. It is well known that the minor amount addition of proper rare-earth elements can greatly enhance the glass forming ability of some glass-forming alloys. The actual glass forming ability of the base alloy and rare-earth doped alloys also were evaluated by the thermal parameter &#947m and the results agree very well with the tendency predicted by the calculation. Bulk amorphous specimens were produced by injection casting. The amorphous nature was analyzed by X-ray diffraction and differential scanning calorimetry. The crystalline phases were analyzed by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and x-ray diffraction. Oxygen contamination was quantified by the inert gas fusion method.

Abstract Biodegradable starch-glycerol based films were obtained. The influence of lipid compounds (palmitic, stearic and oleic acid), other polymers (hydroxypropylmethylcellulose and sodium caseinate) and bioactive compounds (¿-tocoferol, D-limonene and orange essential oil) on film properties (oxygen and water vapour barrier, optical, mechanical, nano- and microstructural). Furthermore the effect of storage time on films¿ properties was also considered. Fatty acids addition did not improve the water vapour ability of films except for non-stored saturated fatty acids containing films. X-ray diffraction results showed that cristallinity of films increased with storage time, thus increasing the stiffness and decreasing the gloss of films. Furthermore, crystallinity affected the water sorption capacity of films as function of relative humidity and temperature. Glass transition temperature of starch films varied with saturated fatty acids addition. However, oleic acid did not affect this parameter. The presence of fatty acids promoted the formation of V-type structures, thus indicatin the formation of amylose-lipid complexes that inhibited the developmet of other crystalline structures. The effect of the incorporation of other biopolymers to improve the functionality of starch films was also studied. Hydroxypropylmethylcellulose (HPMC) addition inhibited starch retrogradation. However, obtained films were more permeable, specially in case of oxygen. HPMC addition produced phase separation as it was observed by scanning electron microscopy. On the contrary, sodium caseinate incorporation (NaCas) allowed to obtain homogeneous films and less permeable to oxygen. Obtained films showed less mechanical resistance in comparison with pure starch films but a greater flexibility without increasing the water vapour permeability. Rearrangement of polymers chains during storage reduced the mechanical resistance, the extensibility and the gloss of composite films. Regarding the obtained results, the film including a starch:protein ratio of 50:50 was choosen as the film with the most adequate properties. Composite film (starch:Nacas ratio = 50:50) was studied as a matrix for the incorporation o active compounds (¿-tocopherol, D-limonene and orange essential oil). The effect of ¿-tocopherol addition was compared with the incorporation of oleic acid and their mixture. Lipids addition promoted phase separation between starch and NaCas due to the different interactions between each polymer and the lipids. Furthermore, oleic acid addition increased significantly the oxygen permeability whereas ¿-tocopherol greatly improved the antioxidant capacity of films without affecting the oxygen permeability. D-limonene and orange essential oil incorporation was carried out by forming rapeseed and soy nanoliposomes, which acted as carriers of bioactive components. Nanoliposomes incorporation was performed directly in starch-NaCas dispersions without any homogenization, to avoid nanoliposomes damages. Bioactive compounds addition did not confer antimicrobial capacity to the films (except for soy-orange oil nanoliposomes containing film) probably due to the high stability of nanoliposomes and the low antibacterial activity of D-limonene and orange essential oil.<br>Se han desarrollado y caracterizado films biodegradables a base de almidón de maíz y glicerol como plastificante, evaluando al mismo tiempo el efecto de la adición de componentes lipídicos (ácido palmítico, esteárico y oleico), otros polímeros (hidroxipropilmetilcelulosa y caseinato de sodio) y compuestos bioactivos (¿-tocoferol, aceite esencial de naranja y D-limoneno) sobre las propiedades de los films (propiedades barrera al vapor de agua y al oxígeno, ópticas, mecánicas, micro y nanoestructurales). Asimismo se evaluó la influencia del tiempo de almacenamiento en las propiedades de los films. La adición de ácidos grasos no mejoró notablemente la permeabilidad al vapor de agua excepto en el caso de los films con ácidos grasos saturados y solo en films no almacenados. Los resultados de difracción de rayos X mostraron que la cristalinidad aumentó con el tiempo de almacenamiento, incrementándose la rigidez, y disminuyendo el brillo de los films. Del mismo modo, la cristalinidad afectó a la capacidad de sorción de agua de los films en función de la humedad relativa y la temperatura. La temperatura de transición vítrea de los films de almidón se vio afectada por la adición de ácidos grasos saturados pero no por la adición de ácido oleico. La presencia de dichos componentes promovió la formación de estructuras cristalinas tipo V, indicando la formación de complejos entre los lípidos y las cadenas de amilosa e inhibiendo la formación de otros tipos de formas cristalinas. Se analizó también el efecto de la incorporación de otros biopolímeros en la posible mejora de la funcionalidad de los films de almidón. En las mezclas con hidroxipropilmetilcelulosa (HPMC), se inhibió la retrogradación del almidón en los films composite, pero se observó un efecto negativo en las propiedades barrera de los mismos, que fueron más permeables, principalmente al oxígeno. La adición de HPMC produjo separación de fases en los films (observada por microscopía electrónica de barrido). Por el contrario, la incorporación de caseinato de sodio (NaCas) permitió formar films homogéneos y menos permeables al oxígeno. Los films presentaron una resistencia mecánica algo menor que los films de almidón puro pero una mayor flexibilidad sin incrementar los valores de permeabilidad al vapor de agua. La reorganización de las cadenas de los polímeros con el tiempo de almacenamiento provocó la disminución de la resistencia mecánica, la deformabilidad y el brillo de los films composite. Atendiendo a los efectos observados, se eligió como formulación más adecuada el film composite formado por almidón y NaCas con un ratio de polímeros del 50:50. El film composite de almidón y NaCas (50:50) se estudió como matriz para la incorporación de compuestos bioactivos como son el ¿-tocoferol y el aceite esencial de naranja o su principal componente, el D-limoneno. El efecto de la adición de ¿-tocoferol se comparó con la influencia de la adición de ácido oleico y también con la adición de ambos compuestos. La adición de lípidos provocó una separación de fases entre el almidón y el NaCas debido a la diferente interacción entre cada polímero y los lípidos. Asimismo la adición de ácido oleico incrementó significativamente la permeabilidad al oxígeno, al contrario que el ¿-tocoferol, que además impartió a los films una elevada capacidad antioxidante. La incorporación de aceite esencial de naranja y D-limoneno se realizó utilizando nanoliposomas de lecitina de soja y lecitina de colza que encapsularon los compuestos activos. La incorporación de nanoliposomas en los films se realizó directamente en las dispersiones acuosas sin posterior homogeneización para evitar su ruptura. La adición de los compuestos bioactivos en forma de nanoliposomas no confirió capacidad antimicrobiana a los films, salvo en el caso de los nanoliposomas de lecitina de soja con aceite esencial, debido probablemente a la dificultad de los compuestos encapsulados para difundir en el film por la gran estabilidad de los liposomas y a la baja actividad antilisteria del D-limoneno y el aceite esencial de naranja.<br>Jiménez Marco, A. (2013). Propiedades de films de almidón de maíz. Influencia de la incorporación de lípidos, biopolímeros y compuestos bioactivos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28214<br>TESIS<br>Premiado

Le but de ce travail est l'etude de la reponse hyperfrequence des vortex dans des films minces supraconducteurs a haute temperature critique, ceci pour des champs magnetiques compris entre quelques oersted et sept tesla. Pour ce faire, il a fallu mettre au point une technique de mesure de l'impedance complexe de lignes microruban supraconductrices dans la gamme de frequence 5 mhz-5 ghz et pour des temperatures comprises entre 4 k et 100 k. L'etude sous champ magnetique a permis la mesure de la variation de la profondeur de penetration avec la temperature et egalement la determination de la conductivite complexe. Une nouvelle methode d'obtention de la valeur absolue de la profondeur de penetration a tres basse temperature a egalement ete mise au point. Sous champ magnetique, les mesures indiquent l'existence d'un changement de regime dans la variation en frequence de l'impedance complexe, aussi bien pour la partie reelle que pour la partie imaginaire. Ces mesures sont comparees aux theories en vigueur comme celle des verres de vortex ou celle de type champ moyen (extension du modele de gittleman et rosenblum)

Los resultados del estudio que se expone en la presente tesis, tratan sobre las arcillas expansivas en “Talara”, en base a resultados obtenidos en los ensayos de laboratorio como el Análisis Granulométrico por Tamizado, ensayo de Límite Líquido, Límite Plástico e Índice de Plasticidad, ensayo de Proctor modificado y el ensayo Corte Directo. Cabe decir que dichos ensayos se realizaron tomando como punto de partida las características geológicas, geomorfológicas, geotécnicas y la evaluación de daños en las diversas estructuras de la zona como viviendas producto de la expansión y consolidación del terreno. La problemática se origina a raíz del suelo arcilloso, ya que la principal característica que puede tener ese tipo de suelo es que sea un suelo expansivo, por lo tanto, se debe tener en consideración mejorar el suelo para evitar posteriormente daños estructurales. En la investigación se describirán las principales consecuencias y factores que intervienen en el fenómeno de la expansión y el cómo enfrentar a este tipo de suelo. El presente estudio busca la mejora del suelo mediante una técnica innovadora, eco amigable y factible como es la estabilización física usando el vidrio reciclado y las fibras de polipropileno (materiales de desecho en las operaciones de la construcción), ya que en la actualidad estos dos tipos de materiales generan un impacto negativo en el medio ambiente, por lo cual se trata de reutilizar dichos materiales en el mejoramiento del suelo. El estudio se basó en una muestra de suelo medianamente expansivo, debido al registro del Límite Líquido, Límite Plástico e Índice de Plasticidad, extraído de la Urbanización Sudamérica, localizado en Talara, Piura con el fin de mejorarlo, para luego verificar el comportamiento de mejora de las propiedades de resistencia al corte del suelo. Como parte del desarrollo de la investigación se realizaron los diversos ensayos para comprobar con datos numéricos la mejora del suelo, otorgando porcentajes de sustitución con respecto al peso seco (0%, 5%, 6% y 7.5%) a la muestra en estado natural. Finalmente, se obtuvieron las mejoras de las propiedades de resistencia al corte con un porcentaje de sustitución equivalente a 5%, el cual registra las mejoras en cohesión y ángulo de fricción.<br>The results of the study that is presented in this thesis, deals with the expansive clays in "Talara", based on results obtained in laboratory tests such as the Granulometric Analysis by Screening, Liquid Limit test, Plastic Limit and Plasticity Index, modified Proctor test and the Direct Cut test. It is possible to say that these tests were carried out taking as a starting point the geological, geomorphological, geotechnical characteristics and the evaluation of damages in the different structures of the area as houses product of the expansion and consolidation of the land. The problem originates from the clay soil, since the main characteristic that this type of soil can have is that it is an expansive soil, therefore, it is necessary to consider improving the soil to subsequently avoid structural damage. The research will describe the main consequences and factors involved in the phenomenon of expansion and how to deal with this type of soil. The present study seeks to improve the soil through an innovative, eco-friendly and feasible technique such as physical stabilization using recycled glass and polypropylene fibers (waste materials in construction operations), since these two are currently Types of materials generate a negative impact on the environment, so it is about reusing these materials in soil improvement. The study was based on a sample of moderately expansive soil, due to the registry of the Liquid Limit, Plastic Limit and Plasticity Index, extracted from the South American Urbanization, located in Talara, Piura in order to improve it, and then verify the improvement behavior of the properties of resistance to the cut of the floor. As part of the development of the research, the various tests were carried out to verify the improvement of the soil with numerical data, granting replacement percentages with respect to dry weight (0%, 5%, 6% and 7.5%) to the sample in its natural state . Finally, the improvements of the properties of resistance to the cut with a percentage of substitution equivalent to 5% were obtained, which records the improvements in cohesion and angle of friction.<br>Tesis

碩士<br>國立臺灣海洋大學<br>材料工程研究所<br>92<br>The purpose of this study was to investigate the amorphization behavior and to explore the glass forming ability (GFA) of mechanically alloyed Mg-Y-Cu powders. After 10 hours milling, Mg85-xY15Cux (X=40~84) powders exhibit a broad diffraction peak in the 2θ range between 37~43o, which is characteristics of amorphous structure. The DSC evaluation of the as-milled powders shows the exothermic peaks corresponding to the crystallization of amorphous structure was existed. However, the glass transition temperature was only observed for Mg85-xY15Cux amorphous powders with compositions X=40~48. The index of GFA as represented by atomic size difference (∆a) was calculated. Although the maximum value was obtained at composition X=66, the GFA as indicated by the appearance of supercooled liquid region was not observed. In contrast, it is noted the GFA of Mg-Y-Cu amorphous alloys can be represented by the increment of atomic size difference with Cu content, ∆R (∆R=∆a / ∆Cu%), since the ∆R of Mg85-xY15Cux (x=40~48%)were larger than that of Mg85-xY15Cux (X=52~84%). As-milled Mg85-xY15Cux (X=40~48) amorphous powders were successfully consolidated into bulk samples by vacuum hot pressing method. The highest Vickers hardness was 350 kg/mm2 and the maximum porosity is less than 4 μ m. TEM investigation indicated the nanostructure with the precipitation of Mg24Y5 nanograin from amorphous matrix was formed for Mg45Y15Cu40 bulk samples.

碩士<br>國立中興大學<br>高階經理人碩士在職專班<br>102<br>Business strategy is a long term plan of action designed to achieve a particular goal or objectives. In order to achieve these objectives under certain environmental conditions of the market, all the actions, policies, programs and competitive methods are included. Automotive glass can be divided into laminated glass for front windshield, and tempered glass for side windows and rear windshield. The annual car sales in 2014 are 378,000 in Taiwan and up to 21.984 million in mainland China, representing growth of 13.9 % over last year. Booming automobile industry will bring greater development of automotive glass industry. Differentiated product development, research and development investment, independent design development, reduction of production costs and market development are necessary to ensure a competitive advantage. This is a qualitative study. We collected the information about the company business strategy, competitive strengths, weaknesses, opportunities, threats and the status of automotive glass industry, as well as reviewed the relevant literature journals, doctoral theses, newspapers, and internet-related information. Hope to provide some help for industry and academia.

碩士<br>國立臺北科技大學<br>材料科學與工程研究所<br>98<br>In this study, 15 at.% of boron is added to increase amorphous forming ability of Al87Y8Ni5 alloy ribbons by single roller melt-spinning process. Thermal properties including crystallization activation energy and the Avrami exponent of crystallization are obtained by non-isothermal and isothermal analyses. The (Al87Y8Ni5)85B15 amorphous alloy ribbon demonstrates a glass transition temperature (Tg) at 529 K, and its ΔTx (=Tx-Tg) value is 24.6 K. Crystallization kinetic study show that the 15 at.% of boron increases the activation energy for crystallization from 159 to 228 kJ/mol. The Avrami exponent n value of Al87Y8Ni5 amorphous alloy is 1.5~2.1 indicating a decreasing nucleation rate with crystallization time, whereas the n value of (Al87Y8Ni5)85B15 amorphous alloy ribbon is 2.3~3.1 or the nucleation rate increases with time. The maximum hardness is obtained for both non-boron and boron added alloys after crystallization at 593-598 K due to formation of nano-crystallites. The highest hardness achieved is 566 and 575Hv for Al87Y8Ni5 and (Al87Y8Ni5)85B15 alloys, respectively. It is further found that the Al3Y and AlNi phases delay their precipitations till higher temperatures due to boron addition. The boron addition apparently improves the stability of Al87Y8Ni5 amorphous alloy.

碩士<br>國立臺灣海洋大學<br>材料工程研究所<br>92<br>The main purpose of this study is to investigate the effect of rare earth addition (Gd) on the glass forming ability (GFA) and crystallization behavior of mechanically alloyed Mg-Y-Cu-Gd powders, in addition, the feasibility of fabricating Mg-Y-Cu-Gd bulk amorphous alloy by vacuum hot pressing was also studied. According to the results, after 10 hours of milling, mechanically alloyed powders exhibited a mixing structure of amorphous /nanocrystalline phase. The improvement on the GFA of mechanically alloyed Mg-Y-Cu-Gd powders can be accompolised by the replacement of Mg and Y with Gd addition. Comparing the result of non-isothermal and isothermal thermal analysis data, it is found that amorphous alloy Mg44Cu36Y15Gd5 has the best thermal stability. The Avrami exponent of amorphous alloy Mg44Cu36Y15Gd5 and Mg49Cu33Y15Gd3 were 2.19 and 2.17 by using Johnson-Mehl-Avrami(JMA) analysis. This implies that the crystallization is governed by diffusion-controlled three-dimensional growth but the nucleation rate shows decreased tendency. The maximum porosity for the hot-pressed Mg44Cu36Y15Gd5 and Mg49Cu33Y15Gd3 bulk sample were around 2~3 μm and the Vickers hardness were 418 and 391 Kg/mm2, respectively.

碩士<br>中臺科技大學<br>醫學工程暨材料研究所<br>97<br>All-ceramic dental restorations are attractive to the dental community because of their higher strength, abrasion resistance, better biocompatibility, and aesthetics. Recently, Yttria stabilized tetragonal zirconia polycrystal(Y-TZP) is gaining recognition as a candidate material in dentistry owing to its excellent mechanical properties. However, these kinds of ceramics are usually fabricated via solid state sintering at high temperature, while it is a very expensive fabrication method and will inevitably increase the production cost. In this study, MgO-CaO-Al2O3-SiO2-P2O5 glass powders were introduced as additives to lower the sintering temperature of TZP and to evaluate the influence of glass additives on sintering and mechanical properties. Zirconia specimens containing 0, 1, 3, 5, 10 wt. % glass powders, respectively were presintered at 700, 800, 900 ℃ and sintered at 1200, 1300, 1400, 1500 ℃. The results indicate that the specimens presintered at 900 ℃ have an optimal cutting performance. The relative density with 5% glass additives achieved 94.8 % when sintered at 1200 ℃. X-ray diffraction patterns indicate that all specimens are tetragonal phase (t-ZrO2), except the specimen presintered at 700 ℃. The best mechanical strength was occurred with the specimen containing with 3 wt% glass when sintered at 1300℃. The hardness and bending strength were 1098.9 HV and 503.1 MPa, respectively. According to this work, the use of the MgO-CaO-Al2O3-SiO2-P2O5 glass as additives can decrease the sintering temperature of Y-TZP. The adapted mechanical strengths can be reached at relatively lower sintering temperatures.

Indiana University-Purdue University Indianapolis (IUPUI)<br>The use of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), normally employed as a framework for all-ceramic restorations, has now started to be used without any veneering ceramics in patients with parafunctional activities. The aims of this study were to evaluate the influence of Y-TZP surface roughness on the wear behavior (volume/height loss) against glass-based ceramics (i.e., IPS Empress CAD and IPS e.max CAD, Ivoclar-Vivadent). Thirty-two Y-TZP full-contour zirconia (Ardent®) sliders (ϕ=2 mm, 1.5 mm in height) were milled in a CAD/CAM unit and sintered according to the manufacturer instructions. Sliders were embedded in brass holders using acrylic resin and then randomly allocated into 2 groups according to the surface treatment (n=16): G1-as-machined and G2-glazed (Diazir®). Empress and e.max antagonists were cut into tabs (13×13×2 mm) wet-finished and also embedded in brass holders. Two-body pin-on-disc wear testing was performed at 1.2 Hz for 25,000 cycles under a 3-kg load. Non-contact profilometry was used to measure antagonist height (μm) and volume loss (mm3). Qualitative data of the testing surfaces and wear tracks were obtained using SEM. Statistics were performed using one- and two-way ANOVAs (α=0.05). The results indicated that G1 yielded significantly higher mean roughness values (Ra=0.83 μm, Rq=1.09 μm) than G2 (Ra=0.53 μm, Rq=0.78 μm). Regarding antagonist loss, G1 caused significantly less antagonist mean height and volume loss (68.4 μm, 7.6 mm3) for Empress than G2 (84.9 μm, 9.9 mm3) while no significant differences were found for e.max. Moreover, Empress significantly showed lower mean height and volume loss than e.max (p<0.0001). SEM data revealed morphological differences on wear characteristics between the two ceramics against Y-TZP. Within the limitations of this study, e.max wear was not affected by Y-TZP surface roughness. However, Empress wear was greater when opposing glazed Y-TZP. Overall, based on our findings, surface glazing on full-contour Y-TZP did not minimize glass-ceramic antagonist wear when compared with as-machined group.

碩士<br>國立成功大學<br>材料科學及工程學系碩博士班<br>94<br>Abstract Mg-based amorphous alloys exhibit highest specific strength among bulk metallic glass systems. In this study, a bulk Mg65Cu25Y10 deposit was produced successfully via spray forming process with higher cooling rate than conventional mold casting route. The deposit is 150mm in diameter, 10 mm in thickness and 650 g in weight. The average porosity is about 10%. The XRD and DSC results of the deposit look similar to that obtained from corresponding amorphous melt-spun ribbon. However, the measured composition of deposit varies slightly with the distance from substrate, which attribute to gravity effect of relative heavy element, like Y and Cu. The deposit is almost amorphous phase from TEM image and diffraction pattern. Twins are induced with deformation for the unique of spray forming process. The supercooled liquid region of the deposit determined from TMA technique is about 20K smaller than that obtained from DSC trace due to the stress induced nanocrystallzation occurred in the former. In addition, the volume reduction of deposit during TMA test was also smaller than that of ribbon and shows better dimension stability. In compressive test，the strength of bulk amorphous alloys is about 269 MPa，strain is about 2.6 %.

OBJECTIVES: Objectives of this study were to evaluate and compare the failure load and mode of failure of aged (4 years) monolithic and veneered Y-TZP and glass ceramic subjected to static loading, cyclic loading, and thermo-cycling. MATERIALS AND METHODS: 2 ceramic materials were used: Vita In-Ceram YZ and IPS e. max CAD. Each material was designed into 60 veneered copings and 30 monolithic crowns (180 specimens). 10 specimens per group were loaded under compression using an Instron universal testing machine at a rate of 0.5 mm/minute until fracture. Another 10 specimens were subjected to cyclic loading (chewing simulation) in a water bath for 50,000 cycles at a frequency of 1 Hz at 30% of the mean failure load, and then were loaded under compression to fracture. Another 10 specimens were subjected to a thermo-cycling test, then loaded under compression to fracture. Data were analyzed using the ANOVA test at α=0.05. RESULTS: The mean failure load (standard deviation) values for veneered zirconia and e.max CAD copings and monolithic zirconia and e.max CAD crowns under static loading were: In-Ceram YZ 14830 N (2494), VM9 2491 N (1047), PM9 3909 N (783), IPS e.max CAD 4197 N (1011), IPS e. max Ceram 1206 N (296), IPS e.max press 2949 N (710). The values for veneered standard zirconia and e.max CAD copings and monolithic zirconia and e.max CAD crowns after cyclic fatigue were: In-Ceram YZ 11039 N (2720), VM9 2849 N (840), PM9 3170 N (1156), IPS e.max CAD 3539 N (526), IPS e. max Ceram 1291 N (1051), IPS e.max press 3093 N (742). For veneered standard zirconia and e.max CAD copings and monolithic zirconia and e.max CAD crowns after thermo- cycling: In-Ceram YZ 15695 N (1517), VM9 3177 N (816), PM9 2860 N (783), IPS e.max CAD 4265 N (681), IPS e. max Ceram 1149 N (375), IPS e.max press 2832 N (717). There was a significant difference in failure load between veneered and monolithic ceramic crowns subjected to static loading, cyclic loading, and thermo-cycling, and a significant difference in the mode of failure between veneered or monolithic crowns. CONCLUSIONS: 1. There was a significant difference in the static failure load of different veneered (Hand layered and pressed-on) YTZP zirconia and e.max CAD copings, monolithic YTZP zirconia, and e.max CAD Crowns, (p < 0.05). 2. The highest static failure loads were shown by high strength monolithic (In-Ceram YZ) material, which were more resistant to cyclic loading compared to other veneered and monolithic systems. 3. The failure load of IPS e.max ceram group was significantly the lowest compared to all other groups. 4. The failure load data for IPS e.max CAD and Vita In-Ceram YZ structures revealed a significant difference in the effect of these structures on the failure loads (p < 0.05). Comparing structures, monolithic Vita In-Ceram YZ crowns showed the highest failure load. 5. There was a significant difference in failure mode among various veneered and monolithic systems (p < 0.05). Only the variable treatment had no impact on the mode of failure of various veneered and monolithic systems (p > 0.05).<br>2020-10-24T00:00:00Z

碩士<br>國立中山大學<br>材料科學研究所<br>94<br>This thesis is divided into two parts. The main purpose of the first part is only to confirm further whether adding B can really improve the glass forming ability (GFA) and thermal stability. It is recently suggested that the addition of the even smaller sized B (0.08 nm) in the Mg65Cu25Y10 alloys to a certain level can further enhance GFA and provide the chance in fabricating larger bulk amorphous billet. The current study extends the concept of adding B to the Mg65Ni25Y10 based alloy, including the replacement of Ni by 1-5 at % (1, 3, and 5 at %) using the arc melting and melt spinning methods. The second part, this experiment drops magnesium element to 58 at% boldly, even lower, and the big element atom neodymium (Nd) improves to 11 at% or more upwards, different from everybody commonly used 65 at %, 25 at % , 10 at % as the main proportion composition , then to observe whether its supercooled liquid region

碩士<br>國立中正大學<br>物理所<br>94<br>Magnetic properties, glass-forming ability, and thermal stability of Y6Fe72B22 system bulk amorphous have been investigated. For (Y0.06Fe0.72B0.22)100-xMx series (M=Ti, Ta, Nb, Al, Hf, and Zr; x=0, 2, and 4), with the increase of M content, the saturation magnetization σ10kOe and Cure temperature TC decreased. Among them, Ta and Nb addition enhanced the glass-forming ability, which increased the diameter of bulk glassy rod from 2 mm for Y6Fe72B22 alloy to 3 mm for (Y0.06Fe0.72B0.22)98M2 and (Y0.06Fe0.72B0.22)96M4 (M=Ta and Nb) alloys. The optimal magnetic properties of σ10kOe=106 emu/g, Hc=0.33 Oe, and TC=247 ℃ were achieved in (Y0.06Fe0.72B0.22)98Nb2 alloy. The supercooled liquid region of ΔTx=65 ℃ in (Y0.06Fe0.72B0.22)96Nb4 alloy is maximum in these series alloy. Substituting 2 at% Ti for Fe and B in Y6Fe70B22Ti2 and Y6Fe72B20Ti2 alloys, respectively, decreased the σ10kOe and the glass-forming ability. On the other hand, substitution of 2 at% Ti for Y in Y4Fe72B22Ti2 not only made the bulk glassy rod as large as 3 mm in diameter, but also resulted in the superior soft magnetic properties of σ10kOe=126 emu/g, and coercivity Hc=0.28 Oe. Next, Ta, Nb, Al and Hf were adopted to substitute 2 at% for Y in the Y4Fe72B22M2 alloys. For Ta and Nb substitution, the diameter of bulk glassy rod can be enhanced from 2 mm for Y6Fe72B22 alloy to 4 mm for Y4Fe72B22M2 (M=Ta and Nb) alloys. Besides, Y4Fe72B22Ta2 had the optimal magnetic properties of σ10kOe=123 emu/g, Hc=0.25 Oe and TC =298 ℃. The supercooled liquid region of ΔTx=37 ℃ in Y4Fe72B22Ta2 alloy is maximum for Y4Fe72B22M2 series bulk. Finally, the effect of the glass-forming ability for C in Y6Fe72B22-xCx alloys was also investigated. The best glass-forming ability in Y-Fe-B-C alloys occurred when 0.2 at % C was added. Its maximum diameter of bulk amorphous is also as large as 3 mm. The supercooled liquid region of ΔTx=46 ℃ in Y6Fe72B21.8C0.2 alloy is maximum for Y6Fe72B22-xCx series.

The glass-forming composition ranges in Al-La-Ni and Mg-TM (Cu, Zn)-Y alloys were predicted using Miedema’s model. Glass-forming abilities of Al-La-Ni alloys and Mg-Cu-RE alloys were studied in terms of reduced glass transition temperature (Trg), supercooled liquid region (∆Tx) and γ parameters. The glass-forming ability parameters of Mg-Cu-RE (RE: rare-earth) alloys were correlated with Mendeleev number. The Miedema model has been used to determine glass-forming composition range in binary Al-La, Al-Ni and La-Ni alloy systems and the ternary Al-La-Ni system by neglecting the ternary interactions. The glass-forming composition range for Al-La, Al-Ni and La-Ni alloy systems extends from 5 to 90 at% La, 30 to 80 at% Ni and 5 to 95 at% Ni, respectively. In these systems the predicted glass-forming composition range is wider than the experimentally observed range. Miedema model, restricting the difference of enthalpy of formation between the amorphous and solid solution phases to within –10000 J/mole to –55000 J/mole gives rise to better prediction of glass-forming composition range compared to the original models. The concept of mixing enthalpy and mismatch entropy has been used in order to quantify Inoue’s criteria of glass formation. The mixing enthalpy and normalised mismatch entropy of the ternary Al-La-Ni alloys, calculated by the extended regular solution model, vary between –12 to –40 kJ/mol and 0.16 to 0.65, respectively. The enthalpy contour plot has been constructed to distinguish the glass-forming compositions on the basis of the increasing negative enthalpy of the composition. Six Al rich Al-La-Ni alloys with nominal compositions Al89La6Ni5, Al85La10Ni5, Al85La5Ni10, Al82La8Ni10, Al80La10Ni10 and Al60La20Ni20 three La rich Al-La-Ni alloys with nominal compositions Al34La33Ni33, Al40La40Ni20 and Al25La50Ni25 have been chosen from the Al-La-Ni ternary phase diagram, to study the glass-forming ability of Al-La-Ni ternary alloy system and the correlation between La-based and Al-based glasses. All the alloys have been prepared using arc melting unit. All the alloy ribbons have been prepared using single-wheel vacuum melt-spinning unit. Two different wheel speeds of 20 m/s and 40 m/s were used for preparing ribbons of all the nine alloys. All the Al-La-Ni compositions, excluding equi-atomic composition (Al34La33Ni33) and Al60La20Ni20, give rise to amorphous phases. The supercooled liquid region and reduced glass transition temperature of this system increases with a decrease in Al content and an increase in La content. The glass-forming ability of the Al rich Al-La-Ni alloys is lower than that of the La-rich Al-La-Ni alloys. The glass-forming ability has been explained by taking into account the binary heat of mixing and the atomic radius mismatch of the constituent elements. Preferential crystallisation takes place during the heat treatment of glassy ribbons. The crystalline products are partially influenced by composition and binary heat of mixing between elements. Mg65Cu25Y10 alloy is a classical glass former of a family of Mg-based alloys. The partial or complete substitution of Y with other rare earth elements has been introduced to correlate the Mendeleev Number with the glass-forming ability parameters: reduced glass transition temperatures (Trg = Tg/Tl), supercooled liquid regions (∆Tx = Tx – Tg) and γ-criterion (TX/(Tg + Tm)). Mg-Cu-RE alloys with nominal compositions Mg65Cu25Y10, Mg65Cu25Y5Gd5, Mg65Cu25Y5Nd5, Mg65Cu25Gd10 and Mg65Cu25Nd10 were chosen for this work. The high reduced glass transition temperature, wider supercooled liquid region and higher γ value of Mg-Cu-Gd-Y amorphous alloy compared to Mg-Cu-Y and Mg-Cu-Nd-Y systems indicates that Mg-Cu-Gd-Y alloys possess higher glass-forming ability. The devitrification of all Mg-Cu-RE glassy alloys used for this work give rise to Mg2Cu (oF48) phase, which is known as anti-Laves phase. The glass-forming composition range for binary and ternary Mg-Cu-Y systems was calculated using Miedema’s model. The development of accurate methods of prediction of glass-forming ability in metallic systems is an important challenge. Pettifor has pioneered the Structure Mapping approach to binary intermetallics. The Pettifor approach can be adapted to the designing of bulk metallic glasses (BMGs). This method has been used to design Al-based and Mg-based BMG’s. Pettifor introduced an integer parameter to characterize the elements, which he called the Mendeleev Number. Essentially, Pettifor’s scheme orders the elements in a sequence of increasing electronegativity. With respect to Mendeleev Number, the Mg-Cu-RE system can be regarded as a binary system, because of the closeness of Mg and Cu (Mg:73, Cu:72, Y:25, Gd:27 and Nd:30). For this system, Mendeleev Number is a more effective parameter than atomic size (Mg: 1.60 Å, Cu: 1.27 Å), as a predictor of glass-forming ability. The effect of Y and rare earth elements on glass forming ability is similar. The atomic number of Y (39) is away from that of the rare earth elements and the Mendeleev Number of Y (25) comes in between those of the rare earth elements. Mg-Zn-Y system is an interesting system for researchers because of higher strength of these alloys. This system draws the crystallographers’ attention due to its composition-dependent structure variations. The Mg-rich RS/PM Mg-Zn-Y alloys yield superior mechanical properties. Therefore, the Mg-rich Mg-Zn-Y system has been chosen to study the microstructural evolution, even though the theoretical calculations for the glass-forming composition range for the Mg-Zn-Y system shows that this system is not a good glass former. Mg-Zn-Y system with nominal compositions Mg97Zn1Y2, Mg97Zn2Y1, Mg97−xZn1Y2Zrx and Mg92Zn6.5Y1.5 were chosen to study the microstructural evolution of these alloys. A small increase in Zn amount (above 2 at.%) in Mg-rich Mg-Y system results in quasicrystalline particles embedded in the matrix, whereas the addition of Zn up to 2 at.% leads to microstructural changes in the α-Mg solid solution.

The glass-forming composition ranges in Al-La-Ni and Mg-TM (Cu, Zn)-Y alloys were predicted using Miedema’s model. Glass-forming abilities of Al-La-Ni alloys and Mg-Cu-RE alloys were studied in terms of reduced glass transition temperature (Trg), supercooled liquid region (∆Tx) and γ parameters. The glass-forming ability parameters of Mg-Cu-RE (RE: rare-earth) alloys were correlated with Mendeleev number. The Miedema model has been used to determine glass-forming composition range in binary Al-La, Al-Ni and La-Ni alloy systems and the ternary Al-La-Ni system by neglecting the ternary interactions. The glass-forming composition range for Al-La, Al-Ni and La-Ni alloy systems extends from 5 to 90 at% La, 30 to 80 at% Ni and 5 to 95 at% Ni, respectively. In these systems the predicted glass-forming composition range is wider than the experimentally observed range. Miedema model, restricting the difference of enthalpy of formation between the amorphous and solid solution phases to within –10000 J/mole to –55000 J/mole gives rise to better prediction of glass-forming composition range compared to the original models. The concept of mixing enthalpy and mismatch entropy has been used in order to quantify Inoue’s criteria of glass formation. The mixing enthalpy and normalised mismatch entropy of the ternary Al-La-Ni alloys, calculated by the extended regular solution model, vary between –12 to –40 kJ/mol and 0.16 to 0.65, respectively. The enthalpy contour plot has been constructed to distinguish the glass-forming compositions on the basis of the increasing negative enthalpy of the composition. Six Al rich Al-La-Ni alloys with nominal compositions Al89La6Ni5, Al85La10Ni5, Al85La5Ni10, Al82La8Ni10, Al80La10Ni10 and Al60La20Ni20 three La rich Al-La-Ni alloys with nominal compositions Al34La33Ni33, Al40La40Ni20 and Al25La50Ni25 have been chosen from the Al-La-Ni ternary phase diagram, to study the glass-forming ability of Al-La-Ni ternary alloy system and the correlation between La-based and Al-based glasses. All the alloys have been prepared using arc melting unit. All the alloy ribbons have been prepared using single-wheel vacuum melt-spinning unit. Two different wheel speeds of 20 m/s and 40 m/s were used for preparing ribbons of all the nine alloys. All the Al-La-Ni compositions, excluding equi-atomic composition (Al34La33Ni33) and Al60La20Ni20, give rise to amorphous phases. The supercooled liquid region and reduced glass transition temperature of this system increases with a decrease in Al content and an increase in La content. The glass-forming ability of the Al rich Al-La-Ni alloys is lower than that of the La-rich Al-La-Ni alloys. The glass-forming ability has been explained by taking into account the binary heat of mixing and the atomic radius mismatch of the constituent elements. Preferential crystallisation takes place during the heat treatment of glassy ribbons. The crystalline products are partially influenced by composition and binary heat of mixing between elements. Mg65Cu25Y10 alloy is a classical glass former of a family of Mg-based alloys. The partial or complete substitution of Y with other rare earth elements has been introduced to correlate the Mendeleev Number with the glass-forming ability parameters: reduced glass transition temperatures (Trg = Tg/Tl), supercooled liquid regions (∆Tx = Tx – Tg) and γ-criterion (TX/(Tg + Tm)). Mg-Cu-RE alloys with nominal compositions Mg65Cu25Y10, Mg65Cu25Y5Gd5, Mg65Cu25Y5Nd5, Mg65Cu25Gd10 and Mg65Cu25Nd10 were chosen for this work. The high reduced glass transition temperature, wider supercooled liquid region and higher γ value of Mg-Cu-Gd-Y amorphous alloy compared to Mg-Cu-Y and Mg-Cu-Nd-Y systems indicates that Mg-Cu-Gd-Y alloys possess higher glass-forming ability. The devitrification of all Mg-Cu-RE glassy alloys used for this work give rise to Mg2Cu (oF48) phase, which is known as anti-Laves phase. The glass-forming composition range for binary and ternary Mg-Cu-Y systems was calculated using Miedema’s model. The development of accurate methods of prediction of glass-forming ability in metallic systems is an important challenge. Pettifor has pioneered the Structure Mapping approach to binary intermetallics. The Pettifor approach can be adapted to the designing of bulk metallic glasses (BMGs). This method has been used to design Al-based and Mg-based BMG’s. Pettifor introduced an integer parameter to characterize the elements, which he called the Mendeleev Number. Essentially, Pettifor’s scheme orders the elements in a sequence of increasing electronegativity. With respect to Mendeleev Number, the Mg-Cu-RE system can be regarded as a binary system, because of the closeness of Mg and Cu (Mg:73, Cu:72, Y:25, Gd:27 and Nd:30). For this system, Mendeleev Number is a more effective parameter than atomic size (Mg: 1.60 Å, Cu: 1.27 Å), as a predictor of glass-forming ability. The effect of Y and rare earth elements on glass forming ability is similar. The atomic number of Y (39) is away from that of the rare earth elements and the Mendeleev Number of Y (25) comes in between those of the rare earth elements. Mg-Zn-Y system is an interesting system for researchers because of higher strength of these alloys. This system draws the crystallographers’ attention due to its composition-dependent structure variations. The Mg-rich RS/PM Mg-Zn-Y alloys yield superior mechanical properties. Therefore, the Mg-rich Mg-Zn-Y system has been chosen to study the microstructural evolution, even though the theoretical calculations for the glass-forming composition range for the Mg-Zn-Y system shows that this system is not a good glass former. Mg-Zn-Y system with nominal compositions Mg97Zn1Y2, Mg97Zn2Y1, Mg97−xZn1Y2Zrx and Mg92Zn6.5Y1.5 were chosen to study the microstructural evolution of these alloys. A small increase in Zn amount (above 2 at.%) in Mg-rich Mg-Y system results in quasicrystalline particles embedded in the matrix, whereas the addition of Zn up to 2 at.% leads to microstructural changes in the α-Mg solid solution.

碩士<br>國立成功大學<br>資源工程學系碩博士班<br>98<br>It is a great challenge for chip-type magnetic components because it need to be co-fired with Ag electrode. Effects of B2O3–Bi2O3–ZnO–SiO2 (BB35SZ, where 35 = the mole fraction of Bi2、O3 in the glass) glass addition on the sintering behavior , magnetic and dielectric properties for Y-type ferrite 2(Ba1-xBixO)．2(ZnyCo0.8-yCu0.2O)．6(Fe2-x/3Znx/3O3) ceramics were investigated in developing low temperature co-fired ceramics (LTCC) for electronic components. The results indicate that the samples doped with minor Bi and Zn (x = 0.1、0.2 ， y =0.3、0.4) and without glass addition , pure Y-type hexagonal ferrite can be obtained. The Bi samples (x =0.1 y =0.3) added with 4wt% BB35SZ can be densified under 9000C. As a result, BB35SZ glass can be used as a sintering aid to reduce the densification temperature of Y-type ferrites from 10500C to 9000C without secondary phase formation. Y-type ferrite ceramics added with 4wt% BB35SZ glass and sintered at 9000C showed a relative density higher than 90%, a high permeability higher than 3, a permittivity lower than 20. The Bi–Zn co-doped (x =0.1，y =0.3) sample added with 4wt% BB35SZ glass exhibited excellent magnetic and dielectric properties in hyper frequency, which can be a promising candidate material for multi-layer chip-inductive components.

Tesis (Lic. en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2011.<br>El objetivo del presente trabajo es el de sintetizar, caracterizar y describir la microestructura y los mecanismos que controlan la coercitividad en un composite RE-TM policristalino basado en el sistema NdFeAl de fácil amorfización, para la composición Nd60Fe30Al10, cubriendo un amplio rango de velocidades de solidificación. La elaboración de los nanocomposites es realizada mediante dos métodos de producción y procesamiento de aleaciones: la técnica de twin roller melt-spinning o elt-spinning doble rodillo y la técnica de chill-casting. Se correlacionan y caracterizan las propiedades magnéticas duras que el sistema posee con la velocidad de enfriamiento desde el estado líquido de la aleación. A partir de la histéresis magnética y la relajación magnética térmicamente activada se determinan los parámetros de activación y las longitudes magnéticas características del composite. Los mecanismos de la coercitividad se describen sobre la base de un mecanismo de anisotropía aleatoria o de strong pinning según el método de producción.<br>Jorge M. Levingston.<br>Imanes -- Dominios y procesos de magnetización -- Elaboración de nanoestructuras -- Compuesto Nd60Fe30Al10 nanoestructurado -- El factor desmagnetizante -- Producto de energía -- Factores de conversión y relaciones útiles -- Análisis térmico y calorimetría diferencial.