Search

Este vídeo muestra cómo calcular la frecuencia de resonancia compleja de un sistema resonante mediante el uso de funciones de MATLAB que permiten la búsqueda de vecros reales y complejos.

Este vídeo muestra la deducción de la expresión del factor de ruido de un cuadripolo y los círculos de ruido constante

Esta función simula el comportamiento de un medidor de Onda Estacionaria (ROE) dada una impedancia normalizada. También permite generar una aleatoria y ver la onda estacionaria, para encontrar la impedancia incógnita

[EN] Today, many industrial applications require components that work under extreme conditions, especially at very high temperatures (>1200 °C) for a long time. An excellent combination of properties such as low thermal conductivity, low coefficient of thermal expansion and high chemical resistance are required for such applications. Advanced ceramic materials based on zircon-zirconia composites (ZrSiO4–ZrO2) possess these properties, thus making them attractive for, i.e., high-level radioactive waste immobilisation. The main drawback of these materials are the high temperatures and long residence times required to sinter them and obtain high densities, which entails high energy consumption and costs. Therefore, non-conventional microwave sintering is a very powerful and efficient technique capable of reducing sintering temperatures and holding times. The objective of this study is to evaluate the microwave sinterability of zircon-zirconia powders obtained by colloidal methods (80–20 vol% and 20–80 vol% ZrSiO4–ZrO2). A stability study of the phases present was carried out by X-ray diffraction and the mechanical and microstructural properties were evaluated in order to obtain the best materials with outstanding final properties.

Se muestra cómo conectar dos redes eléctricas entre sí, caracterizadas por su matriz de dispersión (o matriz S)

Este vídeo muestra un resumen de la obtención de las ecuaciones de onda en medios guiados, teniendo en cuenta las ondas progresivas y regresivas

Este vídeo muestra la problemática a la resolución de ecuaciones con MATLAB. Se muestran algunos métodos, y se ven los problemas de la selección de la semilla, incluso para funciones muy sencillas.

Búsqueda de ceros de una función por el método de Newton Raphson

[ES] In this project, the student will need to analyse, design and implement a dielectric measurement software system which can be used to characterise the dielectric properties of samples inside rectangular waveguides. The developed software system should be complemented with comparisons from commercial software, or measurements to validate the results., [EN] In this project, the student will need to analyse, design and implement a dielectric measurement software system which can be used to characterise the dielectric properties of samples inside rectangular waveguides. The developed software system should be complemented with comparisons from commercial software, or measurements to validate the results.

[ES] In this project, the student will need to analyse, design and implement a dielectric measurement software system which can be used to characterise the dielectric properties of single and double layered materials. The developed software system should be complemented with comparisons from commercial software, or measurements to validate the results., [EN] In this project, the student will need to analyse, design and implement a dielectric measurement software system which can be used to characterise the dielectric properties of single and double layered materials. The developed software system should be complemented with comparisons from commercial software, or measurements to validate the results.

The aim of this work is to study the physical, chemical, and mechanical properties of 3 mol% Yttria-stabilized Tetragonal Zirconia Polycrystalline (3Y-TZP) materials doped with varying amounts of iron oxide (0, 400, 800, and 1000 ppm). We carried out full dense consolidation using two different sintering methods: fast-microwave technology at 1200°C and 1300°C, and conventional furnace at 1400°C. It was observed an improvement in density and hardness values, as well as great fracture toughness, and more intense color was achieved resulting in more natural color, similar to that of human teeth, using the microwave technique at 1300°C compared to the conventional method. However, the microwave-sintered specimens exhibited an increase in zirconia grains size and high color intensity along with iron oxide content when compared to conventional process, where the grain size does not vary with the coloring agent content. The results obtained in this work suggest that microwave technology can produce an increase in sintering activity due to the different dielectric properties of 3Y-TZP materials doped with Fe2O3. Another interesting confirmed result is that the addition of Fe2O3 presents a high resistance to low temperature hydrothermal degradation producing a delay in the aging process.

[ES] Se pretende diseñar un panel "user firendly" para la caracterización de materiales (permitividad) con sondas coaxiales. Se programarán diferentes procedimientos de caracterización disponibles en la bibliografía

[ES] Para la caracterización dieléctrica de materiales planares, como sustratos de placas de circuitos impresos, se programarán varios algoritmos algoritmos disponibles en la bibliografía y se validarán.

[ES] Las comunicaciones inalámbricas de oído a muñeca centradas en el cuerpo se han estudiado en esta tesis. El principal centro de atención ha estado en las antenas y la propagación a 2,45 GHz. Se simularon, prototiparon y midieron dos antenas de uso corporal. La presencia cercana de tejido humano varió las características de las antenas. Por lo tanto, la piel debe considerarse una extensión de las antenas cuando se diseñan para uso corporal. La ganancia de la trayectoria en el cuerpo del oído a la muñeca entre dos antenas de uso corporal ha sido simulada en Ansys HFSS y medida en diez personas en una cámara shielded de radiofrequencia. Se ha encontrado que los movimientos del brazo tienen una gran influencia en las variaciones de la ganancia de la trayectoria. Además, se han encontrado diferencias significativas cuando las antenas se colocan en el mismo lado del cuerpo, por ejemplo, oreja izquierda-muñeca izquierda. La variación se puede estimar en 35 dB para el ejemplo anterior y 40 dB cuando las antenas están en lados opuestos. Se ha visto que la rotación de la muñeca podría variar la ganancia para el peor de los casos en 20 dB. Dos personas evaluadas con la misma longitud anatómica del brazo obtuvieron resultados diferentes. Por lo tanto, se concluyo que otros parámetros tienen una mayor influencia. La línea de visión entre las antenas se ha encontrado como un factor relevante, donde la presencia de ondas incidentes mejora los resultados., [EN] Body-centric ear-to-wrist wireless communications have been studied in this thesis. The main focus has been on the antennas and propagation at 2.45 GHz. Two body-worn antennas were simulated, prototyped and measured. The presence of the human tissue nearby varied the antennas¿s features. Therefore, the skin should be considered an extension of the antennas when they are designed. The ear-to-wrist on-body path gain between the two body-worn antennas has been simulated in Ansys HFSS and measured on ten people in a shielded radiofrequency chamber. The movements of the arm have been found that have a high influence on the variations of the path gain. Further, significant differences have been found when the antennas are placed at the same side of the body, e.g., left ear-left wrist. The variation can be estimated as 35 dB for previous example and 40 dB when the antennas are at different sides. The rotation of the wrist has been seen that could in addition vary the path gain for the worst case in 20 dB. Two tested people with the same anatomical arm¿s length obtained different results. Therefore, it was concluded that other parameters have a higher influence. The Line-of-Sight between the antennas has been found as a relevant factor, where the presence of incident waves improve the results.

[ES] Th goal of this project is to find out if it is possible to use tensor decomposition schemes to compute and analyze broadband MIMO channels. It is well known that SVD decomposition can be used and it is used to implement a MIMO channel and it is also useful implement it. In short, we can relate transmitter and receiver through a matrix with the channel gain. Our goal it is to use tensor decomposition in a MIMO channel. It would provide a different approach to the physical meaning of the decomposition; hopefully it will show the relation between the transmitter and the receiver over delays,of the same instant, symbol, with the channel gain in each moment. The questions we are looking would be: What is SVD? Which is the use of SVD in MIMO channel? What types of tensor decomposition can be used? What type of tensor decomposition suits the most? What is the benefit of tensor decomposition versus SVD? Last part of the project will be testing the different types of tensor decomposition or algorithms we have available., [EN] Th goal of this project is to find out if it is possible to use tensor decomposition schemes to compute and analyze broadband MIMO channels. It is well known that SVD decomposition can be used and it is used to implement a MIMO channel and it is also useful implement it. In short, we can relate transmitter and receiver through a matrix with the channel gain. Our goal it is to use tensor decomposition in a MIMO channel. It would provide a different approach to the physical meaning of the decomposition; hopefully it will show the relation between the transmitter and the receiver over delays,of the same instant, symbol, with the channel gain in each moment. The questions we are looking would be: What is SVD? Which is the use of SVD in MIMO channel? What types of tensor decomposition can be used? What type of tensor decomposition suits the most? What is the benefit of tensor decomposition versus SVD? Last part of the project will be testing the different types of tensor decomposition or algorithms we have available.

Innovative non-conventional approaches, such as microwave sintering, are being developed as a method for sintering a variety of materials which shown advantages over conventional sintering procedures. This work involves an investigation of the microwave sintering of an ATZ composite with two different microwave applicators and frequency generators: 2.45 GHz and 5.8 GHz. Zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) is the composite used in this study. The samples were sintered by microwave in air at 1200 and 1300 °C with 10 min of dwell time at 2.45 and 5.8 GHz in order to evaluate their effects on sintering, using an optimized experimental configuration. In addition, the mechanical properties of MW-sintered samples were compared with those obtained for the same composites sintered by the conventional method (1500 °C/120 min), such as relative density, hardness and fracture toughness.

Dense alumina toughened zirconia nanocomposites (ATZ, 3Y-TZP with 20 wt% Al2O3) were densified by non-conventional microwave sintering technology at relatively low temperatures (1200 and 1300 °C). The sintering method and its effect on densification, microstructure, mechanical properties and tribological behaviour were investigated. The outcomes demonstrated that the density rose as the sintering temperature was higher, and therefore the mechanical properties were enhanced, reaching a maximum hardness (18.4 ± 0.4 GPa) and fracture toughness (5.7 ± 0.3MPa· m1/2). In addition, the samples were subjected to a tribological test in dry and wet conditions, using artificial saliva. In both cases, the coefficient of friction and wear volume for samples obtained by microwave sintering are lower than conventional samples, with the wear volume being two times higher in dry conditions than in wet conditions.

[ES] El ruido de origen humano puede tener impactos negativos en los animales marinos, tanto peces como mamíferos. El ruido de baja frecuencia se puede propagar a grandes distancias a través del agua, y hay evidencias de que afectan a las capturas de peces o a su comportamiento. Para estudiar este efecto,se modela la propagación del ruido de pistolas de aire comprimido en el agua, siendo el medio modelado como un fuido elástico., [EN] Man-made sounds can have strong negative effects on marine fish and mammals. Low frequency sound/noise by seismic airgun, pile-driving and subsea mining has high-level power can propagates long distance and affect fishes. There is evidence that the noise can cause reactions on the behavior of the fish resulting in reduced catches. In order to study this effect, airgun noise propagation in the ocean waveguide will be modelled by ray tracing model: Bellhop. The model can deal with range-dependent bathymetry and depth-dependent sound-speed profiles. The bottom is modelled as fluid/elastic layered system. Different scenarios will be modelled using measured sound speed profile and bathymetry information obtained in a recent experiment. The modelling results will be analyzed.

[EN] Liquid Crystal (LC) is an anisotropic liquid material which flows like a liquid, but at the same time its molecules have an orientational order like in the solid state [1]. Thus, LC is a promising dielectric material for designing reconfigurable devices at microwave frequencies. In order to optimize the design of reconfigurable microwave devices, accurate values of the dielectric permittivity and the loss tangent of LCs are needed. However, new LCs are not well characterized at these frequencies because of its recent use for microwave applications. Therefore, the characterization in this frequency range is required for its practical use within microwave components and devices [2]. In this work, the split-cylinder resonator method has been used for the characterization of LCs at two frequency points, i.e. 5 and 11 GHz. The method is based on the measurement of the resonance frequency and quality factor of the two states of the LC molecules for extracting the complex dielectric permittivity [3]. For achieving these two states, no electric or magnetic fields are needed, just the cell must be turned 90º inside the cavity. The dielectric properties (permittivity and loss tangent) of four different LC samples, GT3-23002 from Merck and QYPD193, QYPD142, and QYPD036 from Qingdao QY Liquid Crystal Co, have been obtained. The highest values of the dielectric anisotropy are presented for the samples QYPD036 and QYPD193, together with the highest values of the corresponding loss tangent parameters. Furthermore, it is observed for all the LCs that the loss tangent decreases and the dielectric anisotropy increases at higher frequencies, which must be taken into account in the development of reconfigurable microwave devices.

[EN] Zirconia is one of the most used ceramics, especially for biomedical applications, due to its exceptional mechanical properties. However, it is commonly known that its properties can be diminished owing to a low temperature degradation (LTD). This phenomenon consists on a spontaneous phase transformation, from tetragonal to monoclinic, under certain conditions, which is accelerated when the samples are exposed under high levels of humidity at a temperature range between 20-300 ºC. In addition to the fact that the monoclinic phase presents worse mechanical properties than the tetragonal one, there is a volume change of 4% between phases that gives rise to defects in the material as microcracks. Due to this reason, zirconia prostheses failed catastrophically inside the human body between 1999 and 20011. Previous researches reveal that Al2O3 addition suppress the propagation of phase transformation2. Thus, the aim of the present work is to study the hydrothermal ageing of zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) composite, which has been sintered by microwave employing two different frequencies: 2.45 and 5.8 GHz. Microwave heating technology is based on the absorption of electromagnetic radiation by the material, which allows the sample to be heated. So far, most microwave heating equipments use 2.45 GHz; accordingly, the novelty of this study is to employ a frequency of 5.8 GHz and to investigate its effect on LTD. LTD is carried out in an autoclaved in steam at 120 ºC and 1.2 bar, because these conditions accelerate the hydrothermal aging process3. In order to characterize the degraded samples, micro-Raman spectroscopy, AFM, nanoindentation technique and electronic microscopy have been performed. References 1. Norton, M. R., Yarlagadda, R., Anderson, G. H. J. Bone Joint Surg. Br., 2002, 84–B, 631–635. 2. Fabbri, P., Piconi, C., Burresi, E., Magnani, G., Mazzanti, F., Mingazzini, C. Dent. Mater., 2014. 3. Presenda, Á., Salvador, M. D.

[EN] At present, ZrTiO4 nanopowders are used as a dielectric in the electroceramic field, applications of catalysis, microwave telecommunications devices, pigments, composites, etc. One of the most interesting applications is the potential as structural material and similar applications that require a high thermal resistance. However, all the properties of zirconium titanate are still a subject of interest for the industrial field.12 There are several routes of synthesis of ZrTiO4; among them is the sol-gel method and lyophilization. These methods have been used to make powders or small pieces of zirconium titanate. However, structural applications require materials in large quantities, so it is necessary to identify the differences between the methods of synthesizing and allowing the preparation of powders suitable for the generation of green materials for subsequent sintering.3 To develop a new generation of nanomaterials with microstructural differences it is necessary to innovate in the sintering process. Years ago, the use of conventional oven for sintering material was the usual procedure. Nowadays, non-conventional methods as Microwave sintering (MW) are a bright way to produce high dense materials, using heating rates in reduce dwell times and lower consumption using 70%-80% less energy. 4 This reactive sintering technique achieves excellent mechanical properties, homogeneous microstructure employing lower sintering temperatures. All these energy and economic advantages generate a new vision for the future on ceramic materials and their industrial production. The main objective of this study is to make a comparison of the mechanical properties of the materials synthesized by sol-gel method and lyophilization and sintered by microwaves.

[ES] Debido a la importancia de los campos de aplicación del sensor de radar de banda ultraancha, y también a los requisitos de cada aplicación específica, existe una demanda creciente de diseño compacto, de bajo coste y alta precisión del sensor de radar de banda ultraancha. Para responder a estas exigencias, esta tesis pretende proponer un sensor de radar UWB avanzado. Este trabajo de investigación se centra en el diseño del sensor de radar de banda ultraancha (UWB) para aplicaciones no destructivas (END). Los detalles de diseño incluyen el diseño de un generador de pulsos ultracorto, de alta potencia con un timbre mínimo. El radar desarrollado fue construido con una configuración biestática. El objetivo de este trabajo es medir el rango de distancia y las propiedades eléctricas de un objetivo, por ejemplo, metales y materiales dieléctricos, como el cloruro de polivinilo (PV C). Para lograr este objetivo, se ha desarrollado un novedoso generador de pulsos de alta potencia ultra-corto (pulsador de radar). El nuevo generador de pulsos consiste en un transistor que funciona en modo de avalancha y un circuito de afilado de pulsos que utiliza un nuevo modelo de diodo de recuperación de paso (SRD). Para convertir el pulso gaussiano en un monociclo, se ha añadido una red de formación de monociclo (MFN). El generador de impulsos desarrollado produce un impulso eléctrico con una amplitud de 12 V, un tiempo de subida de 112 ps y un ancho de impulso (FWHM) de 155 ps. Con el fin de aumentar la amplitud de los pulsos, se han propuesto dos técnicas útiles en este trabajo. El primero consiste en agregar dos generadores en paralelo, en este diseño propuesto se tuvo en cuenta alguna especificación para hacer que este circuito funcione. Sin embargo, la segunda técnica adoptada en este trabajo consiste en dos etapas de generadores, ambas técnicas dan lugar a un buen rendimiento; en lugar de un solo módulo de un generador de impulsos, las técnicas propuestas en este trabajo aumentan, [CA] A causa de la rellevància dels camps d'aplicació del sensor de radar d'ultra banda ampla, i també l'exigència de cada aplicació específica, hi ha una demanda creixent de disseny compacte, de baix cost i alta precisió del sensor de radar d'ultra banda ampla. Amb la intenció d'atendre aquestes demandes, aquesta tesi pretén proposar un sensor avançat de radar UWB. Aquest treball de recerca tracta del disseny del sensor de radar d'ultra-banda ampla (UWB) per a aplicacions no destructives (NDT). Els detalls del disseny inclouen el disseny d'un pols de monocicle amb pols de potència d'alta potència i amb un mínim de timbre. El radar desenvolupat va ser construït en configuració bi-estàtica. L'objectiu d'aquest treball és mesurar el rang de distància i les propietats elèctriques d'un objectiu, per exemple, materials metàl·lics i dielèctrics, com el clorur de polivinil (PV C). Per assolir aquest objectiu, s'ha desenvolupat un nou ultrasò, generador de pols d'alta potència (polsador de radar). El nou generador de pols està format per un transistor que funciona en mode d'allaus i un circuit d'afilat de pols mitjançant un nou model de díode de recuperació de pas (SRD). Per a convertir el pols gaussiano en un monocicle, s'ha afegit una xarxa de formació de monocicles (MFN). El generador de polsos desenvolupat produeix un pols elèctric amb una amplitud de 12 V, un temps d'augment de 112 ps i un ample de pols (FWHM) de 155 ps. Amb l'objectiu d'augmentar l'amplitud dels polsos, s'han proposat dues tècniques útils en aquest treball. El primer consisteix a afegir dos generadors de forma paral·lela, en aquest disseny proposat, cal tenir en compte algunes especificacions per a fer la viabilitat d'aquest circuit. No obstant això, la segona tècnica adoptada en aquest treball consisteix en una doble etapa de generadors, ambdues tècniques donen lloc a una bona actuació; en lloc d'un únic mòdul d'un generador de pols, les tècniques proposades en aquest treball augmenten l'amplitud al, [EN] Due to the relevance of application fields of ultra-wideband radar sensor, and also the requirement of each specific application, there is an increasing demand of compact, low cost and high accuracy design of ultra-wideband radar sensor. With a view to addressing these demands, this thesis aims to propose an advanced UWB radar sensor. This research work deals with the design of the ultra-wideband (UWB) radar sensor for non-destructive (NDT) application. The design details include the design of ultra-short, high power pulse generator monocycle pulse with a minimum of ringing. The developed radar was build in bi-static configuration. The goal of this work is to measure the distance range and electrical properties of a target e.g, metal and dielectric materials, such as Polyvinyl chloride (PV C). To achieve this goal, a novel ultrashort, high power pulse generator (radar pulser) has been developed. The new pulse generator consists of a transistor operating in avalanche mode and a pulse sharpening circuit using a new model of step recovery diode (SRD). In order to converts the Gaussian pulse to a monocycle, a monocycle forming network (MFN) has been added. The developed pulse generator produces an electrical pulse with an amplitude of 12 V, a rise-time of 112 ps and pulse width (FWHM) of 155 ps. For the purpose to increase the amplitude of the pulses, two useful techniques have been proposed in this work. The first one consist of adding two generators in parallel, in this proposed design some specification was be taking into account to making the workability of this circuit. However, the second technic adopted in this work consists of a two-stage of generators, both technics give rise to a good performance; instead of a single module of a pulse generator, the techniques proposed in this work increase the amplitude around the double. In order to transmit and receive the generated ultra-short pulses, two different types of UWB antennas have been used. First, a Vivald

[EN] At present, ZrTiO4 nanopowders are used as a dielectric in the electroceramic field, applications of catalysis, microwave telecommunications devices, pigments, composites, etc. One of the most interesting applications is the potential as structural material and similar applications that require a high thermal resistance. However, all the properties of zirconium titanate are still a subject of interest for the industrial field.12 There are several routes of synthesis of ZrTiO4; among them is the sol-gel method and lyophilization. These methods have been used to make powders or small pieces of zirconium titanate. However, structural applications require materials in large quantities, so it is necessary to identify the differences between the methods of synthesizing and allowing the preparation of powders suitable for the generation of green materials for subsequent sintering.3 To develop a new generation of nanomaterials with microstructural differences it is necessary to innovate in the sintering process. Years ago, the use of conventional oven for sintering material was the usual procedure. Nowadays, non-conventional methods as Microwave sintering (MW) are a bright way to produce high dense materials, using heating rates in reduce dwell times and lower consumption using 70%-80% less energy. 4 This reactive sintering technique achieves excellent mechanical properties, homogeneous microstructure employing lower sintering temperatures. All these energy and economic advantages generate a new vision for the future on ceramic materials and their industrial production. The main objective of this study is to make a comparison of the mechanical properties of the materials synthesized by sol-gel method and lyophilization and sintered by microwaves.

[EN] In this study, real-time and in-situ permittivity measurements under intense microwave electromagnetic fields are proposed as a powerful technique for the study of microwave-enhanced thermal processes in materials. In order to draw reliable conclusions about the temperatures at which transformations occur, we address how to accurately measure the bulk temperature of the samples under microwave irradiation. A new temperature calibration method merging data from four independent techniques is developed to obtain the bulk temperature as a function of the surface temperature in thermal processes under microwave conditions. Additionally, other analysis techniques such as Differential Thermal Analysis (DTA) or Raman spectroscopy are correlated to dielectric permittivity measurements and the temperatures of thermal transitions observed using each technique are compared. Our findings reveal that the combination of all these procedures could help prove the existence of specific non-thermal microwave effects in a scientifically meaningful way.

Aim of the present study is to sinter zirconia nanocomposite powders doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) by non-conventional means, i.e. microwave sintering technology. The sintering effects of various microwave applicators and frequency generators were evaluated using an optimised experimental set-up. The microwave-sintered samples were compared with the composites sintered by the conventional method. The mechanical properties of the ceramic composites were evaluated by their hardness, fracture toughness and Young's modulus. Likewise, their density and microstructure were analysed.