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Intermediate Resolution Near-Infrared Spectroscopy of 36 late-M Dwarfs

Carlos del Burgo Díaz (2012)

We present observations of 36 late-M dwarfs obtained with the KeckII/NIRSPEC in the J-band at a resolution of ∼20,000. We have measured projected rotational velocities, absolute radial velocities, and pseudo-equivalent widths of atomic lines. 12 of our targets did not have previous measurements in the literature. For the other 24 targets, we confirm previously reported measurements. We find that 13 stars from our sample have v sin i below our measurement threshold (12 km s⁻¹) whereas four of our targets are fast rotators (𝜐 sin 𝒾 > 30 km s⁻¹). As fast rotation causes spectral features to be washed out, stars with low projected rotational velocities are sought for radial velocity surveys. At our intermediate spectral resolution we have confirmed theidentification of neutral atomic lines reported in McLean et al. (2007). We also calculated pseudo-equivalent widths (p-EW) of 12 atomic lines. Our results confirm that the p-EW of K I lines are strongly dependent on spectral types. We observe that the p-EW of Fe I and Mn I lines remain fairly constant with later spectral type. We suggest that those lines are particularly suitable for deriving metallicities for late-M dwarfs.

Article

Planetary system Stars: low-mass, brown dwarfs Stars: fundamental parameters, equivalent width Stars: rotation, heliocentric velocity Techniques: radial velocity CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Intermediate Resolution Near-Infrared Spectroscopy of 36 late-M Dwarfs

Carlos del Burgo Díaz (2012)

We present observations of 36 late-M dwarfs obtained with the KeckII/NIRSPEC in the J-band at a resolution of ∼20,000. We have measured projected rotational velocities, absolute radial velocities, and pseudo-equivalent widths of atomic lines. 12 of our targets did not have previous measurements in the literature. For the other 24 targets, we confirm previously reported measurements. We find that 13 stars from our sample have v sin i below our measurement threshold (12 km s⁻¹) whereas four of our targets are fast rotators (𝜐 sin 𝒾 > 30 km s⁻¹). As fast rotation causes spectral features to be washed out, stars with low projected rotational velocities are sought for radial velocity surveys. At our intermediate spectral resolution we have confirmed theidentification of neutral atomic lines reported in McLean et al. (2007). We also calculated pseudo-equivalent widths (p-EW) of 12 atomic lines. Our results confirm that the p-EW of K I lines are strongly dependent on spectral types. We observe that the p-EW of Fe I and Mn I lines remain fairly constant with later spectral type. We suggest that those lines are particularly suitable for deriving metallicities for late-M dwarfs.

Article

Planetary system Stars: low-mass, brown dwarfs Stars: fundamental parameters, equivalent width Stars: rotation, heliocentric velocity Techniques: radial velocity CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Estudio de polarización vectorial

NESTOR EDUARDO CRUZ OJEDA (2017)

En este trabajo se usó la teoría de Polarización óptica con el objetivo de construir un polarímetro de Stokes. Este sistema óptico fue instalado y probado midiendo algunos vectores de Stokes conocidos para su validación. El sistema incluye polarizadores, placas retardadoras de luz, un objetivo de microscopio, un pinhole, un láser y una cámara CCD para registrar las distribuciones de intensidad. El procesamiento de las imágenes se realizó a través de un programa en MATLAB®. La estructura del programa se basa en el método de “Análisis de Fourier usando un retardador de un cuarto de onda rotando” y permite calcular el vector de Stokes resultante de un conjunto de imágenes pixel por pixel. Posteriormente, con la experiencia adquirida, se propuso generar haces vectoriales con simetría axial. Para lograrlo, se utilizó una placa retardadora de luz de media onda espacialmente variable (S-waveplate). Este elemento óptico convierte un haz de luz con polarización lineal a uno con polarización radial o azimutal. Las distribuciones de intensidad generadas por la S-waveplate se analizaron con el programa descrito en el párrafo anterior para su validación. Los resultados confirmaron una distribución de polarización radial y azimutal uniforme, además también fue posible obtener nuevos estados de polarización usando diferentes placas retardadoras de onda. La S-waveplate será empleada para atrapar y manipular micropartículas de poliestireno en un trabajo futuro.

Master thesis

Polarization Radial Azimuthal CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA

Classical Electrodynamics: The Problems in the Theoretical Description of the Intra-Dipole Radiation

Andrew Chubykalo Augusto Espinoza (2017)

In our paper we would like to analyze some mathematical and physical problems which arise in the interior of an electric dipole during its oscillation along the vector of the dipole moment. A hypothesis is advanced that only electric dipole can radiate electromagnetic waves rather than an electric charge.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Classical electrodynamics Intra-Dipole radiation Velocity Acceleration Poynting vector Electromagnetic field Density Umov vector Dipoles Charges Mathematical physics Lorentz condition D’alembert’s equation Homogeneous wave equations

Classical Electrodynamics: The Problems in the Theoretical Description of the Intra-Dipole Radiation

Andrew Chubykalo (2017)

In our paper we would like to analyze some mathematical and physical problems which arise in the interior of an electric dipole during its oscillation along the vector of the dipole moment. A hypothesis is advanced that only electric dipole can radiate electromagnetic waves rather than an electric charge.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Classical electrodynamics Intra-Dipole radiation Velocity Acceleration Poynting vector Electromagnetic field Density Umov vector Dipoles Charges Mathematical physics Lorentz condition D’alembert’s equation Homogeneous wave equations

Pulse propagation through a slab with a time-periodic dielectric function Ɛ(t)

JESUS HUMBERTO ABUNDIS PATIÑO (2010)

In this thesis we embark in the study of the electromagnetic interaction between a

pulse and an active or dynamic slab whose dielectric function varies periodically in

time. In a recent paper [Zurita-Sánchez, Halevi, and Cervantes-González, Phys. Rev.

A 79, 053821 (2009)], the basic properties of a dynamic dielectric medium whose

dielectric constant varies harmonically with time (angular frequency W) were

established. It was found, in particular, that the group velocity becomes infinite at

frequencies that are integer multiples of W 2 . In response to these divergences,

herein the pulse transmission through a slab of dynamic-periodic medium is

analyzed. It is found that the peak of a Gaussian pulse, with its carrier frequency

tuned to W 2 , traverses the plate with a finite velocity that is smaller than the

vacuum speed of light. The peak velocity depends on the plate thickness, the strength

of modulation, and the carrier frequency. It is also found that the velocity of the peak

oscillates with the thickness of the slab. Such oscillatory behavior is associated with

the interference occurring inside the plate. These conclusions are based on detailed

numerical calculations of pulse transmission through a dynamic-periodic slab, applied

to Gaussian pulses. Numerous graphical results are shown for the transmission and

reflection coefficients in both the time- and the frequency-domain. By increasing the

strength of modulation, a greater number of harmonics comes into play, distorting the

pulse and line shapes. This also results in shifts of the carrier frequency. Finally, it is

shown that the transmitted and reflected pulses carry more energy than the incident

pulse! This is explained by the fact that we studied an open system; the excess energy

is supplied by the external agent that modulates our dynamic medium.

En esta tesis abordamos el estudio de la interacción electromagnética entre un

pulso y una placa activa o dinámica cuya función dieléctrica varía periódicamente en

el tiempo. En un artículo reciente [Zurita-Sánchez, Halevi, and Cervantes-González,

Phys. Rev. A 79, 053821 (2009)] se establecieron las propiedades básicas de un

medio dinámico dieléctrico de constante dieléctrica con variación armónica temporal

(con frecuencia angular W). En particular, se encontró que para frecuencias que son

múltiplos enteros de W, la velocidad de grupo se vuelve infinita. En respuesta a estas

divergencias, se ha simulado la transmisión del pulso a través de una placa dinámica

con variación periódica. Se encuentra que el pico de un pulso Gaussiano con

frecuencia portadora W 2 , atraviesa la placa con una velocidad finita que es menor a

la velocidad de la luz en el vacío. El valor específico de la velocidad del pico depende

del grosor de la placa, la fuerza de modulación y la frecuencia portadora. También se

muestra que esta velocidad oscila con el grosor de la placa. Este comportamiento está

asociado a la interferencia que ocurre al interior del medio dinámico. Estas

conclusiones se basan en cálculos detallados de la transmisión del pulso a través de

una placa dinámica con variación periódica, aplicados al caso de pulsos Gaussianos.

Se muestra una serie de resultados gráficos para los coeficientes de transmisión y

reflexión en los dominios del tiempo y la frecuencia. Al incrementar la fuerza de la

modulación se introduce el efecto de un mayor número de harmónicos,

distorsionando la forma del pulso y las líneas espectrales. Esto resulta en cambios en

la frecuencia portadora. Finalmente, se observa que los pulsos reflejados y

transmitidos transportan más energía que el pulso incidente. Esto se explica del hecho

que hemos estudiado un sistema abierto; el exceso de energía es suministrado por un

agente externo que modula el medio dinámico.

Master thesis

Wave propagation Dynamic responce Velocity CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA

Análisis y clasificación de firmas espectrales utilizando técnicas de aprendizaje automático.

ANA PATRICIA (2019)

The study of spectral signatures makes it possible to identify different objects of earth and sky, present in digital images. The elements that are in it make it have a particular feature, it is analogous to a fingerprint. Researcher’s study its spectral signature, which is made up of the physical, chemical, biological and wavelength properties of electromagnetic energy. It has multiple applications in different areas, such as geoscience and astronomy. In geoscience, the spectra are captured by satellites, once the solar radiation has penetrated the atmosphere, each type of surface interacts with the radiation in a way that absorbs wavelengths and reflects different ones. In astronomy, the spectra of the stars are captured by sensors, the electromagnetic radiation that comes from the stars emits wavelengths of the spectrum and several absorption lines. In relation to the study of stellar spectra, the National Institute of Astrophysics, Optics, and Electronics has at its disposal the set of digitized images of the astronomical plates that were taken with Schmidt Camera of Tonantzintla, from 1944 to 1994, during this period observations, it sampled the entire center of the galaxy and one of its poles. The collection of digitized images has been used in other works; researchers have dedicated to the study of stellar spectra, visually and automatically. With respect to automatic methods, in the present thesis work, a set of data is proposed, obtained from algorithms of extraction and selection of feature which results in the spectral signature of each stellar object. In this way, classification of stellar spectra of the proposed data set was made, using machine learning. The objective is to classify the largest number of stellar spectra and increase the classes and subclasses reported in previous works. To finish with the proposed, the results are reported up to 90.32% accuracy, for the main classes and subclasses of spectral type.

El estudio de firmas espectrales, hace posible la identificación de distintos objetos de la tierra y del cielo, presentes en imágenes digitales. Los elementos que en ella se encuentran la hacen poseer características particulares que contiene información sobre la materia con la que interaccionó; es análoga a una huella digital. Los investigadores estudian firmas espectrales, que representan propiedades físicas, químicas y biológicas, a través de su interacción con la radiación emite determinadas longitudes de onda del espectro electromagnético. Tiene múltiples aplicaciones en diferentes áreas, tales como la geociencia y la astronomía. En geociencia, los espectros son captados por satélites. Una vez que la radiación solar ha traspasado la atmósfera, cada tipo de superficie interactúa con la radiación de manera que absorbe longitudes de onda y refleja otras diferentes. En astronomía, los espectros estelares son captados por sensores. La radiación electromagnética que proviene de las estrellas en las que llega poca o ninguna radiación, es emitida en determinadas longitudes de onda del espectro y tiene líneas de absorción. En relación con el estudio de espectros estelares, el Instituto Nacional de Astrofísica, Óptica y Electrónica tiene a su resguardo el acervo de imágenes digitalizadas de las placas astronómicas que fueron tomadas con la Cámara Schmidt de Tonantzintla, desde 1944 hasta 1994, durante este período se realizaron observaciones del cielo, donde se muestreo todo el centro de la galaxia y uno de sus polos. El acervo de imágenes digitalizadas, se ha utilizado en otros trabajos; investigadores se han dedicado al estudio de espectros estelares, tanto de forma visual como automática. Con respecto a métodos automáticos, en el presente trabajo de tesis se propone un conjunto de datos, obtenido de algoritmos de extracción y selección de características que da como resultado la firma espectral de cada objeto estelar. De este modo, se realizó una clasificación de espectros estelares del conjunto de datos propuesto, utilizando técnicas de aprendizaje automático. El objetivo es clasificar el mayor número de espectros estelares e incrementar las clases y subclases reportadas en trabajos previos. Para finalizar con lo propuesto, se reportan los resultados hasta un 90.32% de exactitud, para las clases y subclases principales de tipo espectral.

Master thesis

Techniques Learning Automatic CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA CIENCIAS DE LA TIERRA Y DEL ESPACIO CIENCIAS DEL ESPACIO CIENCIAS DEL ESPACIO

Marco de evaluación para cocinas solares de pequeñas dimensiones

Evaluation framework for small-dimension solar cookers

MAURICIO GONZALEZ AVILES LUIS BERNARDO LOPEZ SOSA HERMELINDA SERVIN CAMPUZANO (2017)

Este documento presenta un marco de evaluación para las cocinas solares con base en tres parámetros: eficiencia energética, facilidad de uso y accesibilidad económica. Cada parámetro evalúa diversos indicadores cuantificables: a) eficiencia energética: potencia de cocción estándar, tiempo de calentamiento, el rendimiento térmico; b) facilidad de uso: la masa en relación al área del colector, orientaciones por hora y capacidad de carga de la olla y; c) accesibilidad económica: el coste por vatio generado y la durabilidad del reflector y/o acumulador térmico. A cada indicador se le asigna una escala máxima y mínima de la evaluación y los datos obtenidos de estos indicadores se integran en un gráfico radial. La suma de los indicadores constituye el aspecto que debe compararse, pero el gráfico también nos permite interpretar las fortalezas y debilidades descritas. Este marco no se puede analizar una sola cocina solar, ya que es una herramienta comparativa que requiere dos o más dispositivos que deseen evaluarse.

The present work introduces an evaluation framework for small-dimension solar cookers based on three parameters: energy efficiency, ease of use, and economic accessibility. Each parameter evaluates various quantifiable indicators, as a) energy efficiency: standardized

cooking power, heating time, and thermal performance, b) ease of use: load capacity in the pot, mass in relation to collector area, orientations per hour, and c) economic accessibility: cost per watt generated and durability of the reflector and/or thermal accumulator. Each indicator has been assigned a maximum and minimum evaluation; data obtained from these indicators were integrated in a radial graph. The sum of the indicators constitutes the aspect to be compared, but the graph also allows us to interpret the strengths and weaknesses described above. This framework requires two or more devices, since it is a comparative tool.

Article

INGENIERÍA Y TECNOLOGÍA Cocinas solares Marco de evaluación Gráfico radial Solar cookers Evaluation framework Radial graph

A model for the settling velocity of flocs; application to an aquaculture recirculation tank

Humberto Salinas Tapia JAVIER MORENO GUEVARA VICTOR DIAZ PALOMAREZ SAMUEL TEJEDA VEGA (2014)

Se generalizó un modelo para velocidad de caida de flocs para diferentes tipos de agregados ; de plantas de tratamiento, estuarios y acuacultura.

A general model for fl ocs settling velocity is still an open fi eld of research in the scientific literature. In this work, a reduced model of an aquaculture recirculation tank was used to validate a model for floc settling velocity. Cohesive sediments from non-used food and fi sh excreta are a main concern in those tanks design. Excess concentrations of sediments can cause fi sh death or additional costs of energy for aeration. This research is aimed to understand the settling behavior of fl ocs when subjected to a liquid shear rate. A reduced scale model of an aquaculture recirculation tank was build in Plexiglas in order to use particle image velocimetry and particle tracking velocimetry techniques to measure fl uid velocities, solid settling velocities, flocs shape and size. Different fl ow rates and solid concentrations were used to develop varied confi gurations in the system; models for floc settling velocity based on fractal theory were calibrated. Cohesive sediments from fi sh food were observed in long-term experiments at constant fl uid shear rate in the recirculation tank. A group of 50 images were obtained for every 5 min. Image analysis provided us with fl oc settling velocity data and fl oc size. Using fl oc settling velocity data, fl oc density was obtained for different diameters at equilibrium conditions, after 1 h or larger experiments. Statistical analysis of fl oc velocities for different floc sizes allowed us to obtain an expression for the drag coefficient as a function of floc particle Reynolds number (Rep). The results were compared with floc settling velocity results from different researchers. The model is able to define the general behavior of fl oc settling velocity, which shows a reduction for larger fl ocs that is not taken into account in classical models. Only two parameters of the drag coefficient model for a permeable spherical particle are needed to be calibrated, for different types of sediments, in order to have more general applicability.

UAEM

Article

Aquaculture drag coeffi cient flocs flocs density fractal dimension permeable particle PIV PTV recirculation tank settling velocity BIOLOGÍA Y QUÍMICA

Experimental observations of cohesive sediment dynamics in aquaculture recirculation tanks

JUAN ANTONIO GARCIA ARAGON Humberto Salinas Tapia (2013)

se describe un modelo para velcocidad de caida de agregados validado experimentalmente.

Cohesive sediments from non-used food and fish excreta are a main concern in aquaculture recirculation tank design. Excess concentrations of sediments can cause fish death or additional costs of energy for aeration. Flow dynamics in these tanks is represented as a multiphase flow with two disperse phases: one of solids (cohesive sediments) and one of gas (oxygen) because aeration is always needed. This research was carried out to understand the settling behavior of flocs when subjected to a liquid shear rate. A reduced scale model of an aquaculture recirculation tank was built in Plexiglas in order to use Particle Image Velocimetry and Particle Tracking Velocimetry techniques to measure fluid velocities, solid settling velocities, floc shape, and size. The optical techniques provided a description of how the phases organize in space and how this organization is related to the microphysics. Different flow rates and solid concentrations were used to develop varied configurations in the system. Models for floc settling velocity based on fractal theory were calibrated. Cohesive sediments from fish food were observed in long-term experiments at constant fluid shear rate and constant gas flow rates in the recirculation tank. Images were obtained each five minutes. Image analysis provided us with floc settling velocity data and floc size. Using floc settling velocity data, floc density data were obtained for different diameters at equilibrium conditions, after one hour or larger experiments. Statistical analysis of floc velocities for different floc sizes allowed us to obtain an expression for the drag coefficient as a function of floc particle Reynolds number (R*=ρwWsD/μ) where Ws is the floc settling velocity, D is floc diameter, ρw is the liquid mass density and μ is the liquid viscosity. The results are helpful to improve cohesive sediment removal in aquaculture recirculation tanks by providing a tool to obtain optimum sedimentation rates as a function of fluid shear rates

UAEM

Article

floc settling velocity aquaculture recirculation tank fractal dimension drag coefficient PTV PIV BIOLOGÍA Y QUÍMICA