Laboratorio de Microondas

La asignatura pretende ser una puesta en práctica de los conocimientos adquiridos en las asignaturas cursadas en los años previos, tales como Electrónica de Comunicaciones, Microondas y Antenas, además de asignaturas más generales de carácter electrónico, e incluso de programación. El objetivo del Laboratorio es la ejecución de un ciclo de diseño completo, tal y como se realizaría en un departamento de I + D de la industria electrónica, más concretamente centrado en el campo de la RF. Los pasos típicos de este ciclo serían: Especificaciones de producto > recopilación información > simulaciones > 1er. diseño > 1er prototipo de laboratorio > medidas y contraste con lo simulado y con lo especificado > 2º prototipo si es necesario Por tanto es un laboratorio que busca que los alumnos y alumnas se enfrenten al reto de diseñar algo y ejecutarlo. Por supuesto la duración limitada del curso, provocará que también se tenga que manejar el gran caballo de batalla en los desarrollos de productos industriales: el tiempo de desarrollo. La limitación frecuencial al rango de los 3GHz de la mayoría de las prácticas a realizar pone de manifiesto su clara relación con el costo de la instrumentación a manejar e, indirectamente, nos conduce a tener en cuenta el otro factor clave: el costo del producto a desarrollar. De nuevo, cobra especial relevancia la ejecución cuidadosa y concienzuda de las operaciones que se vayan a realizar: cálculos y simulaciones, diseño de layouts, consideración de encapsulados y cubiertas metálicas (cajas envolventes), medidas, interpretación de resultados, etc. Como final del desarrollo, se integrará el circuito diseñado en un sistema superior a través de una simulación y se completará el trabajo con una exposición pública en la que se exponga el proceso y los resultados

Microondas

Quizá el contenido de la asignatura corresponda mejor con un título como Circuitos de Frecuencias de Microondas o Dispositivos Utilizados en Frecuencias de Microondas, considerando a estas frecuencias como parte de las denominadas históricamente como Radio Frecuencias.El uso de frecuencias altas,con longitudes de onda del orden de las dimensiones físicas y fenómenos como pérdidas por disipación, conducción y radiación en aumento constante,obliga a especificidades en todos los órdenes: dispositivos, tecnologías, instrumentación, ausencia habitual de economías de escala, etc. Todo ello desemboca en una mayor dificultad a la hora de medir y caracterizar dispositivos y circuitos, cobrando especial relevancia la ejecución cuidadosa y concienzuda de las operaciones que se vayan a realizar: cálculos y simulaciones, diseño de layouts, consideración de encapsulados y cubiertas metálicas (cajas envolventes), medidas, interpretación de resultados, etc

Thermal Mass Effect on the Solution Cooling Rate and on HIPped Astroloy Component Properties

Astroloy is a Ni-based superalloy with high-volume fraction of γ′, which gives high temperature properties but reduces its forgeability. Therefore, powder metallurgy manufacturing processes such as Near Net Shape HIPping are the most suitable manufacturing technology for Astroloy. However, NNSHIP has its own drawbacks, such as the formation of prior particle boundaries (PPBs), which usually tend to decrease material mechanical properties. The detrimental effect of PPBs can be reduced by optimizing the entire HIP processing route. Conventional HIP cycles have very low cooling rates, especially in big components from industry, and thus a series of post-heat treatments must be applied in order to achieve desirable microstructures and improve the mechanical properties. Standard heat treatments for Astroloy are long and tedious with several steps of solutioning, stabilization and precipitation. In this work, two main studies have been performed. First, the effect of the cooling rate after the solutioning treatment, which is driven by the materials’ thermal mass, on the Astroloy microstructure and mechanical properties was studied. Experimental analyses and simulation techniques have been used in the present work and it has been found that higher cooling rates after solutioning increase the density of tertiary γ′ precipitates by 85%, and their size decreases by 22%, which leads to an increase in hardness from 356 to 372 HB30. This hardness difference tends to reduce after subsequent standard heat treatment (HT) that homogenizes the microstructure. The second study shows the effect of different heat treatments on the microstructure and hardness of samples with two different thermal masses (can and cube). More than double the density of γ′ precipitates was found in small cubes in comparison with cans with a higher thermal mass. Therefore, the hardness in cubes is between 4 and 20 HB 30 higher than in large cans, depending on the applied HT

Synthesis and electrochemical properties of Ti-Si alloys prepared by mechanical alloying and heat treatment

The aim of this work was to study the synthesis and electrochemical properties of Ti 2 wt %-Si alloys prepared by mechanical alloying (MA) and heat treatment. The MA process was performed under Ar atmosphere. The structural, morphological, and compositional evolutions during the milling and subsequent heat treatment were investigated by X-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. The electrochemical behavior was evaluated by open circuit potential and linear sweep voltammetry measurements. The results showed that the MA process promotes the formation of a supersaturated α-Ti-Si solid solution. During heat treatment, the Si remaining in the mechanically alloyed powders and the Si from the α-Ti-Si supersaturated solid solution reacted with Ti to form Ti-Si intermetallic compounds. These compounds have a fine and homogeneous distribution in the α-Ti matrix, which cannot be achieved by conventional casting methods. Additionally, the electrochemical evaluations revealed that the mechanically alloyed and heat-treated Ti 2 wt %-Si powders have better corrosion resistance in 1.63 M H2SO4 than the pure Ti and MA Ti-Si samples. This is likely due to the particular microstructure produced during the milling and subsequent heat treatment

Fabrication and arc erosion behavior of Ag-SnO2-ZnO electrical contact materials

This study investigated the synthesis of Ag-SnO2-ZnO by powder metallurgy methods and their subsequent electrical contact behavior. The pieces of Lambda g-SnO2-ZnO were prepared by ball milling and hot pressing. The arc erosion behavior of the material was evaluated using homemade equipment. The microstructure and phase evolution of the materials were investigated through X-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy. The results showed that, although the mass loss of the Ag-SnO2-ZnO composite (9.08 mg) during the electrical contact test was higher than that of the commercial Ag-CdO (1.42 mg), its electrical conductivity remained constant (26.9 +/- 1.5% IACS). This fact would be related to the reaction of Zn2SnO4's formation on the material's surface via electric arc. This reaction would play an important role in controlling the surface segregation and subsequent loss of electrical conductivity of this type of composite, thus enabling the development of a new electrical contact material to replace the non-environmentally friendly Ag-CdO composite

Fertilización de base en un cultivo inicial de pecan con dos marcos de plantación de alta densidad

91-97The fruit of the pecan tree, Carya illinoensis Koch, is considered a very healthy food. In Argentina, pecan cultivation has been expanding rapidly but very little research has been conducted on pecan fertilization and planting systems. The objectives of this study were to characterize some physical-chemical and chemical properties in a pecan crop, and compare different basal fertilization (FB) treatments under two high density plantation frames (MP). Plantation was conducted in Villanueva (Buenos Aires province), on a Tapthoargic Hapludoll, with 10 x 10 m frames (real part: MR) and 8 x 8 m frames (staggered: TR). The experimental design was a split plot with four replications. The main plots were the two frames and the subplots were the different fertilization treatments: Compost (C), Phosphorus (P), slow release Nitrogen (N), and an unfertilized control (T). The determinations to assess the growth of pecan plants were: plant height and stem diameter. With regard to soil fertility, phosphorus fertilization and the addition of compost significatively increased the levels of Bray-P. The organic fertilizer treatment (compost) showed a significant increase in the height of the pecan plantation under the 8 x 8 m frame, which was not apparent in any case for the stem diameter, with a MP x FB significant interaction (P = 0.01) for height variation in the first year. The plantation frame with or without basal fertilization had no effect on pecan volume during the study period

Propiedades físicas de un compost obtenido a partir de residuos de poda

p.95-99El compostaje es el destino ideal para los residuos de poda. Esta práctica ayuda a prolongar la vida útil de los rellenos sanitarios y produce un abono orgánico. Se evaluaron las propiedades físicas de un compost obtenido a partir de residuos de poda provenientes del área de influencia del Complejo Norte III del CEAMSE. Se determinó la densidad aparente y actual, la capacidad de retención del agua gravimétrica y el tamaño de las partículas. Los valores de la densidad aparente fueron 0,38g cm - 3 promedio (DSt. 0,01). La capacidad promedio de retención del agua gravimétrica fue de 58,3 por ciento (DSt. 1,68). La distribución de partículas luego del proceso de tamizado en el laboratorio fue de 7,6 por ciento para partículas mayores a 4,75 mm de diámetro, 8,1 por ciento para mayores a 3,35 mm, 15,2 por ciento para mayores a 2 mm, 18,9 por ciento para mayores a 1 mm, 14,4 por ciento para mayores a 0,5 mm, 14,3 por ciento para mayores a 0,3 mm y 19,9 por ciento de partículas más finas que 0,3 mm. Las características físicas del compost lo muestran apto para su uso como sustrato

evaluation of advanced routing strategies with information theoretic complexity measures

Based on hierarchy and recursion (shortly, HR), recursive networking has evolved to become a possible architecture for the future Internet. In this paper, we advance the study of HR-based routing by means of the Gershenson-Fernandez information-theoretic framework, which provides four different complexity measures. Then, we introduce a novel and general approach for computing the information associated to a known or estimated routing table. Finally, we present simulation results regarding networks that are characterized by different topologies and routing strategies. In particular, we discuss some interesting facts we observed while comparing HR-based to traditional routing in terms of complexity measures

ODS ferritic steels obtained from gas atomized powders through the STARS processing route: Reactive synthesis as an alternative to mechanical alloying

Oxide Dispersion Strengthened Ferritic Stainless Steels (ODS FS) are candidate materials for structural components in fusion reactors. Their ultrafine microstructure and the presence of a very stable dispersion of Y-Ti-O nanoclusters provide reasonable fracture toughness, high mechanical and creep strength, and resistance to radiation damage at the operation temperature, up to about 750 °C. An innovative route to produce ODS FS with composition Fe-14Cr-2W-0.3Ti-0.3Y2O3 (wt.%), named STARS (Surface Treatment of gas Atomized powder followed by Reactive Synthesis), is presented. This route avoids the mechanical alloying (MA) of the elemental or prealloyed powders with yttria to dissolve the yttrium in the ferritic matrix. In this study, starting powders containing Ti and Y are obtained by gas atomization at laboratory and industrial scale. Then, a metastable Cr- and Fe- rich oxide layer is formed on the surface of the powder particles. During consolidation by HIP the metastable oxide layer at Prior Particle Boundaries (PPBs) dissociates, the oxygen diffuses towards saturated solutions or metallic Ti- and Y-rich particles, and Y-Ti-O nano-oxides (mainly Y2TiO5) precipitate in the ferritic matrix. Detailed Microstructural characterization by X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) of powders and consolidated materials is presented and correlated with mechanical behaviour

99mTc-Ciprofloxacin Imaging: Still an Unsettled Issue?

The objective of this work consisted in the assessment of 99mTc-ciprofloxacin imaging performance as a diagnostic tool in an experimental rat model of osteomyelitis. Bone (tibia) infection was induced in adult rats by inoculation of a suspension containing S. aureus suspended in fibrin glue. In vivo studies by means of small animal imaging were conducted using a gamma camera. The study shows the correlation between 99mTc-ciprofloxacin positive images with bacterial bone count but also with histopathological findings in an osteomyelitis animal model, highlighting its potential as a tool in preclinical research and the accomplishment of 3Rs concept regarding welfare of laboratory animals. 99mTc-MDP scintigraphy, failed to show these correlations and therefore it may be proposed as a complementary method to diagnose and follow up the bone physiopathology in this animal model. Future perspectives of small animal imaging in order to potentiate osteomyelitis basic research will derive from numerous research works, and 99mTc-ciprofloxacin may still be a candidate for infectious diagnose and follow-up as demonstrated in this study