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Estudio de fenómenos electromagnéticos en la Interfase de dos medios

GERARDO DIAZ GONZALEZ (2013)

Ninguna superficie es perfectamente plana en cada escala de longitud,

es decir, todas las superficies naturales y las hechas por la mano del hombre

muestran un cierto grado de rugosidad. Por tanto, es imprescindible conocer

cómo afecta la rugosidad de las superficies a los procesos físicos en la

superficie o en su vecindad inmediata. Uno de estos procesos es el

esparcimiento de la luz por superficies rugosas, el cual a pesar de ser objeto

de estudio desde hace más de cien años, aún sigue siendo un campo con

características y aplicaciones fascinantes. En este trabajo nos centramos en

el estudio del esparcimiento de luz por superficies que poseen rugosidad

aleatoria, en particular por superficies cuya rugosidad es aleatoria y en una

sola dimensión, así como la generación teórica y experimental de este tipo de

superficies. Se presenta el desarrollo de la teoría de esparcimiento por

superficies rugosas, desde los conceptos matemáticos básicos hasta la

deducción de las expresiones que describen al campo esparcido. Se

muestran resultados obtenidos a través de simulaciones del esparcimiento

por superficies con rugosidad aleatoria, que además presentan un perfil

parabólico, parecido al de algunos elementos ópticos como son los espejos

utilizados en telescopios reflectores. Se presenta también la implementación

de un arreglo interferométrico donde se utilizan las superficies rugosas

generadas experimentalmente, obteniendo como resultado interferencia entre

patrones de speckle. Se muestran resultados experimentales y se identifican

efectos de bifurcación presentes en las franjas de interferencia, Se

mencionan aplicaciones futuras de las superficies experimentales y de los

resultados obtenidos con el interferómetro.

Doctoral thesis

Electromagnectic wave scattering Rough surfaces Speckle CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA

SECOND HARMONIC GENERATION AS AN OPTICAL PROBE OF BURIED INTERFACES

Sergio Felipe Beltrán Valencia (2019)

"In this manuscript, we present a method for the determination of defects in the crystalline morphology of buried surfaces using SHG. This is done by calculating the second order nonlinear susceptibility using DFT, length gauge and the cut function for surface responses. We analyzed the change in the SHG response of GaAs 110 crystalline slabs due to systematically induced defects. We found that SHG can be used to obtain the position of periodical defects like the displacement of a atom in the periodic crystalline cell, also, SHG can be used to detect dislocation of sections in the slab and misfits between stacked slabs. Finally, we give a scheme for the experimental determination of this defects by using the values of nonlinear susceptibility measurements."

Master thesis

Second harmonic Nonlinear optics TINIBA Crystalline structure Crystalline defects Buried surfaces CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA FÍSICA DEL ESTADO SÓLIDO FÍSICA DEL ESTADO SÓLIDO. LÁMINA DELGADA FÍSICA DEL ESTADO SÓLIDO. LÁMINA DELGADA

SECOND HARMONIC GENERATION AT CRYSTALLINE SEMICONDUCTOR SURFACES

Norberto Arzate (2000)

"First, we obtain linear and non-linear optical spectra of clean Si(100) 2x1 reconstructed surfaces based on the model of polarizable bonds. The crystal is is modeled as an array of point-like polarizable dipoles where each dipole is considered to be at the middle of every Si-Si bond. The model incorporates the reconstruction of the surface through the local field effect. We calculate the optical spectra as a function of dimer buckling and it is shown that the structure which nicely reproduce the experimental reflectance anisotropy and second harmonic generation (SHG) spectra for the c(4 X 2) Si(100) surface. On the other hand, we apply a microscopic formalism to calculate the different contribution to the nonlinear second-order susceptibility required in the calculation of SHG."

Doctoral thesis

SHG RAS Semiconductor surfaces CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

INTERFEROMETRIC TESTING OF ASPHERICAL CONVEX SURFACES

JOSE ZACARIAS MALACARA HERNANDEZ (2001)

"Convex aspherical optical surface testing, has inherently several difficulties. They are considered as the most challenging to perform. Recent failures in achieving high performance telescopes like the Hubble Space telescope, have made a deep concern about the difficulties and importance of the tests. The importance in testing aspherical optical testing is evident from the constantly increasing papers in specialized journals around this subject. This document is built around three main subjects in three chapters. Chapter 1: Convex Surface Testing; Chapter 2: Projection of the Pupil in Non-Null Tests and Chapter 3: Digitization of Interferograms of Aspheric Wavefronts."

Doctoral thesis

Convex surfaces Convex surface testing Interferometry Interferogram digitization Interferometer Wavefronts CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Superficies flexibles para fomentar el juego cooperativo en niños de preescolar

Flexible surfaces to promote cooperative play in preschoolers

ESTHELA VIANEY VAZQUEZ MEDINA (2017)

La práctica de juego cooperativo comienza en la edad preescolar, a partir de los 4 años. Practicar juego cooperativo ayuda a los niños en edad preescolar (preescolares) a reducir su agresividad y estar más dispuestos a colaborar. La práctica de actividades cooperativas, puede enseñar a los preescolares a ser más tolerantes, atentos y respetuosos con los demás. Las maestras de preescolar utilizan el trabajo en equipo como principal estrategia para fomentar el juego cooperativo entre sus alumnos. Sin embargo, los preescolares tienen dificultades para aprender a trabajar juntos. Actualmente, existen superficies interactivas cooperativas para niños que se enfocan en mejorar sus habilidades de creatividad y socialización. Sin embargo, poco se ha explorado el uso de superficies interactivas para promover el juego cooperativo en preescolares; menos aún, se ha estudiado el uso de superficies interactivas flexibles. Música Flexible es una tela interactiva desarrollada en CICESE que permite crear música a los preescolares. Un estudio exploratorio de su uso en salones de preescolar indica que puede promover la socialización entre preescolares. Sin embargo, no implementa mecanismos para juego cooperativo. En esta tesis se describe el diseño, implementación y evaluación de una tela interactiva para fomentar, explícitamente, el juego cooperativo en preescolares llamada Estrellitas Elásticas. Durante el diseño de Estrellitas Elásticas se siguió una metodología centrada en el usuario. Para interactuar con Estrellitas Elásticas, los preescolares usan un guante con una lámpara de color. El color se utiliza para inferir la identidad del niño. Durante el juego, los preescolares realizan las actividades del juego cooperativo, como trabajar juntos y tomar turnos, mientras acompañan a dos pequeños astronautas durante su viaje por el espacio. Se realizó una evaluación de Estrellitas Elásticas con treinta preescolares y cuatro maestras de preescolar durante tres semanas. Durante la evaluación, los preescolares tuvieron sesiones de juego en equipo con Estrellitas Elásticas y al terminar contestaron cuestionarios sobre experiencia de juego. Los resultados de esta evaluación indican que Estrellitas Elásticas fomenta el juego cooperativo entre los preescolares, además de resultarles un juego divertido y entretenido. Las maestras de preescolar encontraron a Estrellitas Elásticas como una opción para su material didáctico.

The practice of cooperative play begins at the preschool, starting at age 4. Practicing cooperative play, preschoolers can reduce their aggressiveness and be more willing to collaborate. The practice of cooperative activities, can teach preschoolers to be more tolerant, attentive and respectful of others. Preschool teachers use teamwork as the main strategy to encourage cooperative play among their students. However, preschoolers find difficult learn how to work together. Nowadays, there are cooperative interactive surfaces for children that focus on improving their creativity and socialization skills. However, there have been few studies on the use of interactive surfaces to promote cooperative play in preschoolers, even less research about the implementation of flexible interactive surfaces. Bendable Sound is a fabric-based interactive surface developed at CICESE that allows preschoolers to create music. An exploratory study of its use in preschool classrooms indicates that Bendable Sound can promote socialization. However, the surface does not implement cooperative play mechanisms. This thesis describes the design, implementation and evaluation of a fabric-based interactive surface to encourage explicitly cooperative play in preschoolers called Estrellitas Elasticas. Preschoolers wear a glove with a color lamp to interact with Estrellitas Elasticas. The color in lamps facilitates inferring the identity of the child. Preschoolers perform cooperative play activities, like working together and taking turns, while accompanying two little astronauts during their journey through space. The evaluation of Estrellitas Elasticas for three weeks included thirty preschoolers and four preschool teachers. In the evaluation, preschoolers had team play sessions with Estrellitas Elasticas and they completed game experience questionnaires. The results of this evaluation indicate that Estrellitas Elasticas promotes cooperative play among preschoolers, as well as being a fun and entertaining game. Preschool teachers find Estrellitas Elasticas like a good option for their teaching material. As future work, we propose, among other things, the development of a second version of Estrellitas Elasticas with more activities and game themes

Master thesis

Superficies interactivas, superficies flexibles, juego cooperativo, preescolares Interactive surfaces, flexible surfaces, cooperative play, preschoolers INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS PROCESOS TECNOLÓGICOS OTRAS OTRAS

On the Existence of Gauge Functions for Space-Like Separations

Andrew Chubykalo Augusto Espinoza (2017)

In this paper we have a threefold objective. 1. To propose a method for the determination of gauge transformations. 2. to prove that some gauge transformations are local, in the sense that they are not defined all along the space-time. 3. To show that the Cauchy problem for Maxwell equations depends on the geometry of space-time, so the choice of gauge cannot be convential. After developing our method we compare it with Jackson´s well known procedure of [1]. Our first result is that the methods are not coextensive, but they have, however, a common class of solutions in some important cases, e.g. the class of gauge functions transforming the Lorenz gauge into the velocity gauge which is treated in detail. However, our scope in the paper is wider and much more theoretical than that of [1], because we advance to prove that there are certain regions in space-time where no gauge transformation exists, so the results of any method to determine a gauge function are “local” in the sense that they produce results valid for a bounded space-time región, and not for all. So our second and main result in the paper is that gauge transformations in electromagnetic theory are always local. We give also a discussion of the Cauchy problem for classical space-times in order to show that Maxwell equations for these space-times allow instantaneous solutions.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Gauge transformations space-like surfaces

On the Existence of Gauge Functions for Space-Like Separations

Andrew Chubykalo (2017)

In this paper we have a threefold objective. 1. To propose a method for the determination of gauge transformations. 2. to prove that some gauge transformations are local, in the sense that they are not defined all along the space-time. 3. To show that the Cauchy problem for Maxwell equations depends on the geometry of space-time, so the choice of gauge cannot be convential. After developing our method we compare it with Jackson´s well known procedure of [1]. Our first result is that the methods are not coextensive, but they have, however, a common class of solutions in some important cases, e.g. the class of gauge functions transforming the Lorenz gauge into the velocity gauge which is treated in detail. However, our scope in the paper is wider and much more theoretical than that of [1], because we advance to prove that there are certain regions in space-time where no gauge transformation exists, so the results of any method to determine a gauge function are “local” in the sense that they produce results valid for a bounded space-time región, and not for all. So our second and main result in the paper is that gauge transformations in electromagnetic theory are always local. We give also a discussion of the Cauchy problem for classical space-times in order to show that Maxwell equations for these space-times allow instantaneous solutions.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Gauge transformations space-like surfaces

An amplitude-phase (Ermakov–Lewis) approach for the Jackiw–Pi model of bilayer graphene

HARET CODRATIAN ROSU (2009)

"In the context of bilayer graphene we use the simple gauge model of Jackiw and Pi to construct its numerical solutions in powers of the bias poten-tial V according to a general scheme due to Kravchenko. Next, using this numerical solutions, we develop the Ermakov-Lewis approach for the same model. This leads us to numerical calculations of the Lewis-Riesenfeld phases that could be of forthcoming experimental interest for bilayer graphene. We also present a generalization of the Ioffe-Korsch nonlinear Darboux transformation."

Article

Condensed matter: electrical, magnetic and optical Surfaces, interfaces and thin films Nanoscale science and low-D systems CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA

Patrones gestuales para la identificación de autismo en niños

Gestural patterns for the detection of autism in children

GLORIA IVONNE MONARCA PINTLE (2018)

El autismo es uno de los trastornos de desarrollo más frecuentes y su prevalencia va en aumento. En México se estima que 1 de cada 115 niños tiene autismo. El diagnóstico del autismo es una tarea compleja, tardada y subjetiva, se basa en el auto-reporte y la observación de comportamientos. En los últimos años se han realizado investigaciones para encontrar marcadores bio-conductuales computacionales del autismo –un marcador bio-conductual computacional es una característica del autismo que se puede identificar por herramientas computacionales-. En particular se ha encontrado que la fuerza que usan los niños con autismo al jugar en una tableta es diferente a la fuerza que usan los niños neurotípicos. Sin embargo, los gestos realizados en una tableta rígida no brindan información suficiente para evaluar la fuerza que se usa. Las superficies elásticas representan una mejor oportunidad que las tabletas para evaluar aspectos relacionados con la fuerza. En esta tesis se propone la identificación del autismo en niños mediante el análisis de los gestos que realizan al usar una superficie elástica. Durante esta tesis se realizó un estudio en sitio donde participaron 46 niños neurotípicos y 26 niños con autismo. Todos los niños realizaron 7 actividades en una superficie elástica llamada Música Flexible, la cual es una superficie elástica que permite a los niños con autismo crear música y practicar patrones de movimiento. Para analizar los gestos que realizan los niños y evaluar si podemos distinguir autismo, se utilizaron técnicas de aprendizaje de máquina y se realizaron 3 experimentos. Los resultados indican que es posible distinguir entre niños con autismo de niños neurotípicos con una precisión de 97.2 % y una sensibilidad de 94.6%, utilizando la fuerza como variable de control cuando interactúan con una superficie elástica. Un análisis de los patrones gestuales de los niños con autismo al interactuar con una superficie elástica reveló que realizan gestos más pequeños, más angostos y más duraderos. Esto implica que los niños con autismo realizan menos gestos y usan menos fuerza que los niños neurotípicos.

Currently, autism is one of the most frequent developmental disorders and its prevalence is increasing. In México 1 out of 155 children has autism. Etiology of autism is multifactorial and yet to be completely determined, consequently there is no cure for autism. Detection, the earliest the better, and subsequent remedial therapies is the only option. However, detection of autism is time-consuming, based on self-reporting and behavioral observation. As a consequence, the detection of autism is highly subjective. In recent years, research has been conducted to uncover the computational bio-behavioral markers associated to autism. A computational bio-behavioral marker is a behavioral feature able to be identified by computational tools. In particular, it has been found that children with autism use a different amount of force than neurotypical children when playing games with a tablet. However, a tablet using a rigid display can hardly uncover the amount of force its users use when manipulating its interface, making elastic surfaces a more appropriate technology to evaluate aspects related to force. In this work, we hypothesize that autism can be detected by analyzing the gestures used by children when interacting with an elastic surface. We conducted a deployment study where 46 neurotypical children and 26 children with autism used an elastic surface called Bendable Sound. Bendable Sound is a spandex fabric that allows children with autism to create music and practice movement patterns. We conducted 3 experiments analyzing our data by participant, gesture, and activity. We were able to distinguish between neurotypical and autistic children with 97.2% precision and 94.6 recall using only the interaction with an elastic surface as diagnostic tool. An analysis of the gestural movement patterns of children with autism shows that they tend to do smaller, narrower and slower gestures than neurotypicals. This implies that children with autism practiced fewer gestures and used less force than neurotypicals. This encouraging result seem to indicate that automated detection of autism is feasible.

Master thesis

detección de autismo, superficies elásticas, gestos, aprendizaje de maquina autism detection, flexible surfaces, gestures, machine learning INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS TECNOLOGÍA DE LOS ORDENADORES INTELIGENCIA ARTIFICIAL INTELIGENCIA ARTIFICIAL

The design of two-dimensional random surfaces with specified scattering properties

EUGENIO RAFAEL MENDEZ MENDEZ (2005)

"A method is proposed for designing a two-dimensional randomly rough Dirichlet surface which, when illuminated at normal incidence, scatters a scalar plane wave with a specified angular distribution of its intensity. It is validated by computer simulation calculations."

Article

Scattering, Random surfaces, Kirchoff approximation, Inverse problem CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA