Fresnel coefficients as hyperbolic rotations

We describe the action of a plane interface between two semi-infinite media in terms of a transfer matrix. We find a remarkably simple factorization of this matrix, which enables us to express the Fresnel coefficients as a hyperbolic rotation.Comment: 6 pages, 3 figure

In-situ preparation of a highly accessible Pt/CNF catalytic layer on metallic microchannel reactors. Application to the SELOX reaction

A general method to prepare a catalytic coating on the surface of stainless steel microreactors has been developed. The catalytic support consists of a layer of randomly oriented, highly accessible carbon nanofibers (CNFs), directly grown on the surface of the channels by chemical vapor deposition (CVD) of ethanol. These CNFs are functionalized to acquire a positive charge before a solution containing metallic nanoparticles (Pt) is flown through the channels. The nanoparticles adhere to the surface of the CNFs thanks to electrostatic interactions. This process is carried out in-situ and the method can be easily adapted to larger scale production. These catalyst-coated microchannel reactors have been tested in the selective oxidation (SELOX) of CO in the presence of H2. The results were compared to those obtained in a conventional fixed bed reactor packed with Pt/CNTs. The microreactor clearly outperformed the fixed bed reactor at the same space velocity (WSHV = 2220 l/h gPt),), achieving total CO conversion at temperatures 50ºC lower

Constructing Fresnel reflection coefficients by ruler and compass

A simple and intuitive geometical method to analyze Fresnel formulas is presented. It applies to transparent media and is valid for perpendicular and parallel polarizations. The approach gives a graphical characterization particularly simple of the critical and Brewster angles. It also provides an interpretation of the relation between the reflection coefficients for both basic polarizations as a symmetry in the plane

Producción de subjetividad y cárcel

El siguiente trabajo se enmarca dentro de las Prácticas Pre-Profesionales y el proyecto de extensión “Hacer valer la pena: Universidad y cárcel” ambos pertenecientes a la Cátedra Psicoterapia II de la Facultad de Psicología de la UNLP desarrollados en la Unidad Penitenciaria N° 18 de Gorina, La Plata. Se abordará la temática del posicionamiento de los sujetos privados de la libertad dentro de la cárcel y para la sociedad toda. A partir de entrevistas y talleres realizados en dicha unidad fue posible observar la existencia de una diferenciación constante entre quienes se encuentran dentro de la cárcel y aquellos, como nosotros, que vienen desde afuera.Eje: Psicología Social Publicado en: Memorias del IV Congreso Internacional de Investigación de la Facultad de Psicología: conocimiento y práctica profesional: perspectivas y problemáticas actuales - Tomo IIFacultad de Psicologí

Producción de subjetividad y cárcel

El siguiente trabajo se enmarca dentro de las Prácticas Pre-Profesionales y el proyecto de extensión “Hacer valer la pena: Universidad y cárcel” ambos pertenecientes a la Cátedra Psicoterapia II de la Facultad de Psicología de la UNLP desarrollados en la Unidad Penitenciaria N° 18 de Gorina, La Plata. Se abordará la temática del posicionamiento de los sujetos privados de la libertad dentro de la cárcel y para la sociedad toda. A partir de entrevistas y talleres realizados en dicha unidad fue posible observar la existencia de una diferenciación constante entre quienes se encuentran dentro de la cárcel y aquellos, como nosotros, que vienen desde afuera.Eje: Psicología Social Publicado en: Memorias del IV Congreso Internacional de Investigación de la Facultad de Psicología: conocimiento y práctica profesional: perspectivas y problemáticas actuales - Tomo IIFacultad de Psicologí

Growth of carbonaceous nanomaterials over stainless steel foams. Effect of activation temperature

Some of the problems that occur during the operation of chemical reactors based of structured catalytic substrates, as monoliths, foams, membranes, cloths, fibres and other systems, are related to the preparation of long term stable coatings. Frequently, the deposition of the catalytic layer is carried out by washcoating, requiring this step a cautious attention, especially in the case of complex geometries, like of that of foams or cloths. In the case of the deposition of layers of carbonaceous materials (CNMs), an alternative route, avoiding the washcoating, it is their direct growth by catalytic decomposition light hydrocarbons (also called CCVD), over the surface of the metallic substrate. In this case, if the metallic substrate is of stainless steel, it already contains the catalytic active phases like Fe and Ni. In order to optimize the process of CNMs growth over structured metallic substrates, we are studying the effect of the main operational variables of the ethane decomposition reaction on stainless steel foams. In this contribution we present a study of the influence of the temperature of the activation (oxidation and reduction) stage on the type and morphology of the carbonaceous materials formed. The results obtained allow us to determine the optimal operating conditions to maximize the amount and the selectivity of the process to obtain a given type of CNM

Producción de subjetividad y cárcel

El siguiente trabajo se enmarca dentro de las Prácticas Pre-Profesionales y el proyecto de extensión “Hacer valer la pena: Universidad y cárcel” ambos pertenecientes a la Cátedra Psicoterapia II de la Facultad de Psicología de la UNLP desarrollados en la Unidad Penitenciaria N° 18 de Gorina, La Plata. Se abordará la temática del posicionamiento de los sujetos privados de la libertad dentro de la cárcel y para la sociedad toda. A partir de entrevistas y talleres realizados en dicha unidad fue posible observar la existencia de una diferenciación constante entre quienes se encuentran dentro de la cárcel y aquellos, como nosotros, que vienen desde afuera.Eje: Psicología Social Publicado en: Memorias del IV Congreso Internacional de Investigación de la Facultad de Psicología: conocimiento y práctica profesional: perspectivas y problemáticas actuales - Tomo IIFacultad de Psicologí

Performance of AISI 316L-stainless steel foams towards the formation of graphene related nanomaterials by catalytic decomposition of methane at high temperature

This work explores the preparation of graphene-related materials (GRMs) grown on stainless steel foams via catalytic decomposition of methane (CDM). The main active phases for the reaction are the Fe nanoparticles segregated from the stainless-steel after the activation stage of the foam. The effect of the feed composition and reaction temperature has been studied in order to maximize the productivity, stability and selectivity to GRMs. The maximum productivity attained was 0.116 gC/gfoam h operating at 950 °C with a feed ratio of CH4/H2 = 3 (42.9 %CH4:14.3 %H2). The carbonaceous nanomaterials (CNMs) obtained were characterized by X-Ray diffraction, Raman spectroscopy and by transmission and scanning electron microscopy. The parameters of the kinetic model developed are directly related to the relevant stages of the process, including carburization, diffusion-precipitation and deactivation-regeneration. The balance among these sequential stages determines the overall performance of the activated foam. In conditions of rapid carburization of the Fe NPs (pCH4 > 14 %), the productivity to CNMs is favoured, avoiding an initial deactivation of the active sites by fouling with amorphous carbon. After a rapid carburization, the selectivity to the different CNMs is governed by the ratio CH4/H2, and mainly by the temperature. Thus, the formation of GRMs, mainly Few Layer Graphene (FLG) and even graphene, is favoured at temperatures above 900 °C. At lower temperatures, carbon nanotubes are formed

Mechanical and microstructural features of wire-and-arc additively manufactured carbon steel thick plates

Metal additive manufacturing (AM), in particular wire-and-arc additive manufacturing (WAAM), has become over the last few years the breakthrough technology to reduce the environmental impact and increase the efficiency of steel structures. Although intense research effort has been paid toward the mechanical characterization of WAAM-produced thin walls, little attention has been devoted to the investigation of multi-layered thick parts. These latter would indeed expand the application of WAAM for large-scale constructions requiring thicker cross-sections to withstand high loading conditions. The present work provides a comprehensive experimental investigation of mild steel WAAM thick plates from the fabrication to the mechanical and microstructural characterization. First, the fabrication process is presented in full details. From that, microstructural and mechanical characterization is described and discussed, showing a homogeneous microstructure with little influence on the mechanical response along the wall plate thickness, also considering different specimen orientations with respect to the printing directions. The results confirm good mechanical properties of the printed outcomes, in line with those of structural mild steels manufactured with conventional technologies. Little influence on the response along the thickness is reported, thus proving the required quality of WAAM thick parts for applications in the construction sector

Generación de biogas a partir de la degradación de residuos orgánicos de frigoríficos

Se presentan los primeros resultados obtenidos del estudio de los parámetros característicos de la degradación de residuos orgánicos colectados en un frigorífico de peces ubicado en Bella Vista – Corrientes- Argentina. Se armaron 8 reactores a escala de laboratorio y un digestor de 200 l instalado a campo abierto. Las temperaturas de trabajo en ambas situaciones fueron entre 25 y 35 °C, tiempo de retención hidráulico 30 días, y el contenido de estiércol en la suspensión: 10%, 25%, 50% y 100% en el laboratorio y 50% en el digestor de campo. Los reactores de laboratorio se hicieron funcionar de manera discontinua. Se midieron la cantidad de biogás generado y acumulado. La concentración de metano en el biogás generado a campo abierto varió entre 45% y 60%. Se concluyó que el tratamiento anaerobio del efluente colectado en el frigorífico es una opción de depuración biológica y técnica de generación de energía útil.The characteristic parameters of the degradation of organic waste collected in a fish slaughterhouse located in Bella Vista – Corrientes- Argentina were study using 8 laboratory scale reactors and 200 l digester. Temperatures in both situations were between 25 and 35 ° C, hydraulic retention time 30 days, and the content of manure in suspension: 10%, 25%, 50% and 100% in the laboratory and 50% in the digester field. Laboratory reactors were operated batchwise. Biogas generated and accumulated were measured. Methane concentration varied between 45% and 60%. The anaerobic treatment of effluent collected in a slaughterhouse, is an option of biological and technical debugging generating useful energy.Tema 6: Energía eólica, geotermia, biomasa y otras energías no convencionales.Facultad de Arquitectura y Urbanism