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Synthesis of sources with Markovian features

Gabriel Cosntantino Martínez Niconoff PATRICIA MARTINEZ VARA ESTEBAN ANDRES ZARATE Javier Silva Barranco Javier Muñoz López (2013)

We realize the design and synthesis of partially coherent secondary sources illuminating an ensemble of mobile transmittances in a tandem array. The motion states of the transmittances are random variables which are synchronized by means of the conditional probability density function whose control allows generating sources whose light emission corresponds with a Markov chain. The experimental results are shown. [DOI: http://dx.doi.org/10.2971/jeos.2013.13005]

Article

Coherence Stochastic process CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Statistical Modelling of Pitting Corrosion: Extrapolation of the Maximum Pit Depth-Growth

JULIO CESAR VELAZQUEZ ALTAMIRANO J.A.M. van der Weide ENRIQUE HERNANDEZ SANCHEZ Héctor Herrera Hernández (2014)

Pitting corrosion is one of the main threats in the pressure vessels integrity and also causes the failure of buried pipelines steels that transport sour gas, crude oil or condensate hydrocarbon, for this reason, a reliability assessment of pressurized vessels and buried pipelines based on probabilistic mathematical modelling to estimate the remaining life-time due to pitting corrosion damage is extensively employed. Herein, a methodology for probabilistic mathematical modelling of the pits initiation process and its depth growth process is developed; both uncertain processes are well represented by stochastic models. In this methodology two stochastic models are applied; Poisson process is used to model pit initiation and Gamma process to model the pit depth-growth. Such methods are validated using data produced by computer modeling procedures. On the other hand, in the oil industry it is common not to inspect the entire vessels surface; instead of this only a small part of the surface is under inspection. According to this, the use of Block Maxima (BM) and Peak-Over-Threshold (POT) models “EXTREME VALUE STATISTICS” to characterize the probability distribution of maximum pit depths is also approached. The results indicate that POT model can evaluate efficiently the maximum pitting corrosion depths.

Aknowledge and express their gratitude to CONACyT for the SNI distinction as research membership and the monthly stipend received.

Article

Pitting corrosion Stochastic models Pressure vessels Steel pipelines BIOLOGÍA Y QUÍMICA

Inmersión de nanopartículas de oro y plata en una matriz de TiO2 para fotocatálisis plasmónica

Immersion of gold and silver nanoparticles in a TiO2 matrix for plasmonic photocatalysis

Christian Andrés Palacios Torrez (2022)

En este trabajo se probaron tres diferentes rutas para la inmersión de nanopartículas de oro (AuNPs) o plata (AgNPs) en una matriz de Degussa P25 (TiO2): 1) Mezcla y secado de dispersiones coloidales; 2) modificación de cargas superficiales (previo a la mezcla de dispersiones); 3) reducción directa de sales metálicas sobre TiO2. Posteriormente, se evaluó su actividad fotocatalítica en la degradación de azul de metileno (MB) con luz UV y visible, buscando registrar un mejoramiento inducido por la resonancia de plasmón de superficie localizado (LSPR) excitada en las nanopartículas metálicas. La respuesta óptica de todos los materiales fue monitoreada por espectroscopía UV-Vis y su estructura fue analizada a partir de imágenes elaboradas con microscopía electrónica de transmisión (TEM). La síntesis de AuNPs y AgNPs coloidales dio como resultado dispersiones con absorción máxima en λ∼543 nm y λ∼420 nm, respectivamente. El análisis de imágenes TEM permitió registrar diámetros de 56±4 nm para AuNPs y 31±3 nm para AgNPs, así como su inmersión en la matriz de TiO2 (rutas 2 y 3). Las constantes de reacción representativas de la fotodegradación de MB (obtenidas a partir de la absorción en λ∼664 nm) fueron, en su mayoría, menores a las pruebas control con TiO2. El uso de AgNPs@TiO2 (ruta 2) bajo luz UV+Visible (352 nm+420 nm) reflejó una constante de reacción 0.005 unidades mayor a la exhibida por TiO2 bajo las mismas condiciones, siendo el único caso en que se registró un incremento en la actividad fotocatalítica. En conjunto con los resultados obtenidos, la presencia de una capa de polielectrolito (PAH) entre las AgNPs y el TiO2 en este sistema permitió concluir que, de haberse generado un mejoramiento plasmónico en la fotocatálisis de MB, éste se habría dado a través del mecanismo de transferencia de energía resonante inducida por plasmones (PIRET).

The present work aimed to achieve the immersion of gold (AuNPs) or silver (AgNPs) nanoparticles in Degussa P25 (TiO2) via three different routes: 1) Mixing and drying of colloidal dispersions; 2) surface charge modification (prior to dispersion mixing); 3) direct reduction of metallic salts over TiO2. Subsequently, photocatalytic activity for methylene blue (MB) degradation was evaluated under UV y visible light, hoping to register an enhancement induced by the localized surface plasmon resonance (LSPR) exhibited by the metallic nanoparticles. Optical response for each material was monitored by UV-Vis Spectroscopy measurements, and its overall structure was analyzed with transmission electron microscopy (TEM) imaging. The products of the synthesis of coloidal AuNPs and AgNPs were dispersions with maximum absorption at λ∼543 nm and λ∼420 nm, respectively. Diameters of 56±4 nm (AuNPs) and 31±3 nm (AgNPs) were confirmed with TEM image analysis, as well as the immersion of said nanoparticles in TiO2 (routes 2 and 3). Most of the reaction constants for MB photodegradation (calculated from absorption at λ∼664 nm) were lower than those obtained for only TiO2. Use of AgNPs@TiO2 (route 2) under UV+Visible light (352 nm+420 nm) yielded a reaction constant 0.005 units higher than that obtained with only TiO2. This was the only instance where an enhancement of the photocatalytic activity was registered. Based on the aforementioned results, as well as the presence of a polyelectrolite layer (PAH) between AgNPs and TiO2, it can be concluded that: If any significant enhancement over the photocatalytic activity of TiO2 was achieved, it would have been generated via the Plasmon-Induced Resonant Energy Transfer (PIRET) mechanism.

Master thesis

Nanopartículas de oro (AuNPs), nanopartículas de plata (AgNPs), dióxido de titanio (TiO2), resonancia de plasmón de superficie localizado (LSPR), fotocatálisis heterogénea, inyección de electrones calientes, transferencia de energía resonante ind Gold nanoparticles (AuNPs), silver nanoparticles (AgNPs), titanium dioxide (TiO2), localized surface plasmon resonance (LSPR), heterogeneous photocatalysis, hot electron injection, plasmoninduced resonant energy transfer (PIRET) INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS TECNOLOGÍA DE MATERIALES PROPIEDADES DE LOS MATERIALES PROPIEDADES DE LOS MATERIALES