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Climatología y meteorología de tornados en México
Full text link"La presente investigación exhibe las principales características de la tornadogénesis en México. Se expone una climatología actualizada de estos fenómenos y se relaciona con la variación estacional de las características ambientales prevalentes en el territorio mexicano. Con base en este análisis general, se establece a la región de influencia de la Faja Volcánica Transmexicana (FVTM) como la zona de mayor ocurrencia de tornados en México. Dadas las peculiaridades de terreno complejo, las interacciones atmosféricas y la alta densidad de población en esta zona, se estudian, a través de datos de reanálisis, los patrones de circulación de escala sinóptica relacionados a la generación de tornados. Asimismo, se examinan y describen a través de productos satelitales del sensor MODIS, los mecanismos de convección profunda asociados a estos eventos de tiempo severo. Se explora, a través del modelo WRF- ARW, el rol del terreno complejo en la generación de condiciones inestables precedentes a la formación de tornados no-supercelda en el centro de México. Los resultados muestran, además del importante rol de las circulaciones locales moduladas mayormente por la orografía, que los tornados en esta zona poseen una misma probabilidad de giro ciclónico o anticiclónico, lo que contradice a lo reportado por la literatura. Finalmente, los mecanismos de tornadogénesis encontrados en la región centro de México, se comparan con los obtenidos en un tornado supercelda al noreste del territorio, identificando diferencias importantes. Los tornados en México exhiben características únicas de generación, distribución y ocurrencia. El estudio de las condiciones bajo las que estos fenómenos se han documentado en el país busca el entendimiento de los mecanismos involucrados en su formación, desarrollo y futura predicción.""The present research shows the principal characteristics of tornadogenesis in Mexico. Is
exposed an updated climatology of these phenomena and related to the seasonal variability
of environmental features that prevail in Mexican territory. This general analysis reveals that
the influence region of the Trans-Mexican Volcanic Belt (TMVB) as the zone with the
highest occurrence of tornadoes in Mexico. Given the particularities of the complex terrain,
the atmospheric interactions and, the high population density in the TMVB, the synoptic
patterns related to the generation of tornadoes are studied from reanalysis data. Likewise, the
mechanisms of deep and moist convection associated with these severe weather events are
examined through the satellite products of MODIS data. Through the application of the
WRF-ARW model, the role of the complex terrain in the generation of instability conditions
precedent to the formation of non-supercell tornadoes in central Mexico is explored. The
results show that the tornado phenomenon in this region has the same probability of cyclonic
or anticyclonic rotation, which contradicts previous literature. Local circulations in the
complex orography play a vital role in this process. The mechanisms of tornadogenesis found
in the central region of Mexico are compared to those obtained from a supercell event in the
northeast portion of the territory. It was possible to identify essential differences. The
tornadoes in Mexico exhibit unique features in the sense of generation, distribution, and
occurrence. The study of the meteorological conditions under which these phenomena occur
is a relevant issue. The documented tornadoes in the country seek the understanding of the
mechanisms involved in their formation, development, and future prediction.
Modificación y evaluación de polímeros semiconductores para su potencial uso en dispositivos fotovoltaicos
Full text link"Actualmente las celdas perovskitas de vanguardia presentan una configuración convencional tipo n-i-p que consisten en óxido de titanio (TiO2), semiconductor tipo n, cubierto por la perovskita y una capa transportadora de huecos (HTL). Sin embargo la configuración invertida p-i-n también ha ganado importancia significativa por su compatibilidad en los procesos de fabricación de alto rendimiento. En este tipo de dispositivos las capas transportadoras de carga convencionales son el polímero PEDOT:PSS y el PCBM C60 para extraer huecos y electrones de la capa perovskita, respectivamente. Sin embargo, la naturaleza ácida e higroscópica de PEDOT:PSS se ha comprobado que acelera la degradación de los dispositivos ya que absorbe agua del ambiente lo que deteriora la capa de perovskita. Por lo cual, se están realizando grandes esfuerzos en la búsqueda y desarrollo de nuevos materiales poliméricos que disminuyan los efectos negativos de dicho material en las celdas de perovskita. El objetivo principal de esta tesis es la obtención un material semiconductor sulfonado con características eléctricas adecuadas para utilizarse como capa HTL en dispositivos fotovoltaicos. Diversas investigaciones acerca de las propiedades eléctricas de polímeros semiconductores en forma de películas delgadas, han establecido que el transporte eléctrico y las propiedades ópticas dependen fuertemente de la estructura molecular, y a su vez, éstas dependerán del método de deposición y las condiciones de preparación de las mismas. Tomando en cuenta estas aseveraciones se modificó la estructura de la polisulfona con la inserción del grupo sulfonato, logrando incrementar su conductividad, además se determinó que el tratamiento térmico posterior a la deposición de las películas delgadas tenía un efecto positivo sobre esta propiedad. Como experimento de exploración se formaron compositos de la polisulfona sulfonada (PSF-S) con ZnO funcionalizado con plata u óxido de grafeno. La adición de ZnO funcionalizados redujo la resistividad de la PSF-S, obteniendo las menores resistividades con los compositos de ZnO funcionalizado con óxido de grafeno. Sin embargo no fue posible obtener películas delgadas con estos compositos. Por tal motivo solo se evaluaron los PSF-S en celdas solares tipo perovskita de configuración invertida. Los resultados indican que un mayor porcentaje de sulfonación mejora el rendimiento eléctrico de los dispositivos (Factor de relleno y eficiencia de conversión de potencia). Además, los resultados obtenidos abren la posibilidad de usar un polímero flexible y no convencional, desde el punto de vista eléctrico, como HTL, ya que muestra un nivel de energía comparable al de los polímeros usados convencionalmente como el PEDOT: PSS.""Currently, cutting-edge perovskite cells have a conventional n-i-p type configuration
consisting of titanium oxide (TiO2), a semiconductor n-type, covered by perovskite and
hole transport layer (HTL). However, the inverted configuration p-i-n has also gained
significant importance due to its compatibility in high-performance manufacturing
processes. In these types of devices, the conventional transport charge layers are the
polymer PEDOT: PSS and the PCBM C60 for extracting holes and electrons from the
perovskite layer, respectively. However, the acidic and hygroscopic nature of PEDOT:
PSS accelerates the degradation of the devices because of the absorbed water from
the environment which deteriorates the perovskite layer. Therefore, great efforts are
being made in the search and development of new polymeric materials that diminish
the negative effects of said material on perovskite cells.
The main objective of this thesis is to obtain a sulfonated semiconductor material with
electrical characteristics suitable for use as an HTL layer in photovoltaic devices.
Several investigations about the electrical properties of semiconductor polymers thin
films, have established that electrical transport and optical properties strongly depend
on the molecular structure, and in turn, these will depend on the deposition method
and preparation conditions from the same. Taking into account these assertions, the
structure of the Polysulfone was modified with the insertion of sulfonate groups,
achieving an increase in its conductivity, and it was determined that the heat treatment
after the deposition of thin films had a positive effect on this property.
As exploration experiment, sulfonated polysulfone (PSF-S) composites were formed
with silver or graphene oxide functionalized ZnO. The addition of functionalized ZnO
reduced the resistivity of PSF-S, obtaining the lower resistivities with graphene oxide
functionalized ZnO composites. However, it was not possible togenerate thin films with
these composites. For this reason, only PSF-S were evaluated in perovskite-type solar
cells with an inverted configuration. The results indicate that a higher percentage of
sulfonation improves the electrical performance of the devices (Fill factor and power
conversion efficiency). Also, the obtain results open the possibility of using a flexible unconventional polymer,
from the electrical point of view, such as HTL, since it shows an energy level
comparable to that of conventionally used polymers such as PEDOT: PSS.
Aspectos caóticos de una clase de mapeos discretos sin puntos fijos
Full text linkEl estudio de sistemas dinámicos discretos ha sido de gran utilidad para el desarrollo de distintas áreas de las ciencias naturales, exactas y sociales. Una de las características que pueden poseer los sistemas dinámicos discretos es el de presentar comportamiento caótico. Este rasgo ha sido aprovechado por la criptografía en la generación de secuencias pseudoaleatorias. Es por ello que la importancia de generar nuevos sistemas que exhiban mapeos caóticos resulta de gran utilidad.
En esta tesis se presentan dos familias de mapeos discretos que tienen la particularidad de no presentar puntos fijos: la primera definida por mapeos racionales y la segunda por mapeos lineales por partes. En cada una de estas familias se dan las condiciones que deben tener para que se consiga obtener tal particularidad. Además, para la familia de mapeos lineales por partes y sin puntos fijos se hace un análisis a través de los exponentes de Lyapunov para determinar caos para ciertos valores de los parámetros. Finalmente se toma un mapeo lineal por partes y sin puntos fijos con valores particulares y se demuestra la existencia de caos en el sentido de Devaney.The study of discrete dynamical systems has been very useful for the development of different areas in science, such as natural sciences, exact sciences and social science. One of the
properties that, discrete dynamical systems have, is that they can exhibit chaotic behavior.
This feature has been exploited by cryptography in the generation of pseudorandom sequences. Because of this, the importance of generating new systems that exhibit chaotic maps is
worth it.
In this thesis, two families of discrete maps are presented, both of them have the particularity that they do not have fixed points: the first of them, is defined by rational maps, the second one is describred by piecewise linear maps. In each of these families the conditions
are given so that they do not have fixed points. Furthermore, for the piecewise linear maps
and non fixed points family, an analysis is done through the Lyapunov exponents to detect
chaos. Finally, a particular piecewise linear map with not fixed points is taken and the existence of chaos at Devaney sense for this map is proved
Supersimetría y propagación de solitones en guías de onda
Full text link"Se hace el estudio teórico de la propagación de pulsos a través de un medio, descrito por las ecuaciones de Maxwell considerando las características materiales del medio, a través de la “ecuación de onda”; y se implementa un procedimiento para la obtención de una solución analítica de la misma ecuación bajo el uso de métodos supersimétricos, tal como se hace en mecánica cuántica para el caso de la ecuación de Schrödinger, ya que esta ecuación y la ecuación de onda son similares en una aproximación paraxial. El tratamiento supersimétrico nos permite proponer una aplicación tecnológica haciendo un filtrado de modos, a través de la aplicación iterativa del método de manera jerárquica. Por otra parte, en este mismo contexto óptico, se trabaja con sistemas dinámicos de óptica no lineal, tomando como sistema principal el modelo en guías de onda y fibras ópticas. Como es bien sabido, en estos sistemas ópticos generalmente se presentan soluciones que se pueden ver como soluciones de tipo onda solitaria y de tipo switcheo (kinks). Teniendo como referencia que, una de las principales aplicaciones de estos sistemas, es aquella que en sus ecuaciones la solución se presenta en el entorno de solitones ópticos, soluciones que presentan características específicas y bien definidas del pulso. Para ser exactos principalmente estas soluciones se observan en ecuaciones no lineales, como lo son las ecuaciones de Schrödinger (NLSE por sus siglas en inglés) y de Ginzburg-Landau (NLGLE). Entonces, tomando en cuenta lo mencionado anteriormente, para hacer una contribución en la obtención de soluciones de este tipo de problemas, en este trabajo se propone un método para encontrar soluciones solitónicas de las ecuaciones no lineales de Schrödinger y Ginzburg-Landau en casos generalizados de ecuaciones de coeficientes variables, en las cuales se hace el tratamiento con solitones no autónomos, mismos que están descritos bajo el manejo de dispersión y no linealidad, relacionados con ejemplos concretos en aplicaciones tecnológicas presentadas en la literatura. También, se presenta una descripción de un modelo no lineal comúnmente trabajado en óptica, pero bajo un esquema supersimétrico de factorización con ayuda del método propuesto por Rosu y Cornejo-Pérez para la factorización de ecuaciones diferenciales no lineales de segundo orden, en donde en esta tesis este problema es propuesto como una extensión del método, obteniendo soluciones solitónicas supersimétricas.""Initially, to make the theoretical study of the propagation of pulses through a medium, it is necessary to work through the development of Maxwell’s equations, contemplating the material characteristics of the medium, from which the differential equation of the second order called “wave equation”, this equation that when is solved, gives us information of the explicit form of the pulse propagation in the medium. In this thesis a procedure was implemented to obtain an analytical solution of the wave equation under the use of supersymmetric methods, as is done in quantum mechanics for the case of the Schr¨odinger equation. Classical Schr¨odinger equation and the wave equation are similar in a paraxial approximation, the supersymmetric treatment is used to obtain a solution starting from the own factorization of the method. Where you get a parametric family solution by propagation constants analogous to energy in quantum mechanics, which generate in optics “ isomodespectrality” (i.e, is obtains the same propagation constants for the waveguides by supersymmetry method except for the fundamental mode or first mode), which correspond to the real and discrete eigenvalues of the linear Schr¨odinger spectral problem in its optic paraxial treatment, at the same time, by this method a partner waveguide is obtained, represented by the index of refraction and this is called “supersymmetric waveguide”, it means we are able to generate the type of structure that will support the modes of propagation partners, also, this supersymmetric method can be applied in a hierarchical manner, with which we realize that, it is guaranteed a filtering structures of propagation modes. On the other hand, in this same optical context, we work with dynamic systems of nonlinear optics, taking the model in waveguides and optical fibers as the main system. As is well known, in these optical systems solutions are usually presented that can be seen as solutions of solitary wave type and switching type (kinks). Taking as reference that one of the main applications of these systems is that in their equations the solution is presented in the environment of optical solitons whose solutions have specific and well defined characteristics of the pulse. To be exact, these solutions are mainly observed in non-linear equations, such as the Schrödinger (NLSE) and Ginzburg-Landau (NLGLE) equations. Then, taking into account the aforementioned, to make a contribution in obtaining solutions for this type of problems, in this work we propose a method to find solitonic solutions of the non-linear equations of Schrödinger and Ginzburg-Landau in generalized cases of variable coefficients equation, in which the treatment is done with non-autonomous solitons, which are described under the dispersion and non-linearity management, related to concrete examples in technological applications presented in the literature. Finally, a description is made of a nonlinear model commonly worked in optics, but under a supersymmetric scheme of factorization with the help of the method proposed by Rosu and Cornejo-Pérez for the factorization of nonlinear second order differential equations, where in this thesis this problem is proposed as an extension of the method, obtaining solitonic supersymmetric solutions.
Reguladores de voltaje basados en convertidores con capacitores conmutados
Full text link"En los últimos años, los nuevos desarrollos tecnológicos demandan sistemas de procesamiento de energía con alta eficiencia y, para aplicaciones que realizan conversión de la energía proveniente de fuentes renovables, una mayor relación de conversión entre los voltajes de entrada y salida. Convertidores conmutados de CD-CD son comúnmente utilizados para elevar el nivel de voltaje en aplicaciones tan diversas como sistemas de energías renovables, sistemas de transporte, sistemas industriales y equipos médicos entre otros. Algunas características deseables en convertidores conmutados de CD-CD son una alta ganancia de voltaje, corrientes de entrada y salida del convertidor no-pulsantes y voltaje de estrés reducido en los dispositivos de conmutación. En este trabajo de tesis, se proponen dos topologías de convertidores elevadores con una alta ganancia de voltaje; la primera de ellas se logra al unir un convertidor elevador convencional con una celda multiplicadora de voltaje y la segunda al unir un convertidor elevador cuadrático con una celda multiplicadora de voltaje. Para ambos convertidores se analizan las condiciones en estado estable y se obtienen todas las expresiones que permiten realizar un diseño apropiado de los convertidores. También se obtienen los modelos en el espacio de estados bilineal conmutado, no lineal promediado y el modelo a pequeña señal. Posteriormente, se obtienen las funciones de transferencia de la corriente en el primer inductor respecto al ciclo de trabajo y la de voltaje de salida respecto al ciclo de trabajo. La respuesta en frecuencia teórica y experimental se comparan para verificar la validez de los modelos. Adicionalmente se diseñan controladores en modo-corriente promedio para construir reguladores conmutados. Se construyeron dos prototipos de 300 W en el laboratorio de procesamiento eficiente de energía, el primero de ellos con un voltaje de entrada de 24 V y un voltaje de salida de 200 V; el segundo con un voltaje de entrada de 24 V y un voltaje de salida de 220 V. Por último, se obtuvieron la respuesta en frecuencia de los lazos de voltaje de manera experimental para garantizar estabilidad y robustez. Por último, se realizaron pruebas con cambios abruptos de carga y se obtuvieron pruebas de eficiencia de conversión; en el primero de los prototipos se obtuvo el 97% de eficiencia, mientras que en el segundo un 82% de eficiencia, ambos a plena carga.""In recent years, new technological developments require the processing of
energy with high efficiency and a wider conversion rate between the input and the
output voltages. A common solution is to use switch-mode DC-DC step-up
converters for applications such as renewable energy systems, transportation
systems, industrial systems and medical equipment among others. Some of the
desirable characteristics of the switch-mode DC-DC converters for the above
applications are a high gain voltage, non-pulsating input-output currents and a
reduce voltage stress in the switching devices. In this doctoral dissertation, two
topologies for high gain switching converters are studied; the first one combines a
conventional boost converter with a voltage-multiplying cell and the second one
combines a quadratic boost converter with a voltage-multiplying cell. The
mathematical expressions for the proper design of both converters are given. The
corresponding switching bilinear, nonlinear average and linear average models are
developed. Furthermore, the corresponding transfer functions for the first inductor
current to the duty cycle and output voltage to the duty cycle are also developed.
The models are validated by experimental frequency responses of each converter.
Later a methodology for the design of the corresponding controllers using average
current-mode control is given. In the laboratory, two prototypes were built with a
power of 300 W; the first one with an input voltage of 24 V and an output voltage of
200 V, the second one with an input voltage of 24 V and an output voltage of 220 V.
The corresponding frequency responses for the voltage loop gains are obtained to
show the stability and robustness of the voltage regulator. Experimental test for step
changes of load and efficiency are given where the first prototype exhibits an
efficiency of 97%, meanwhile for the second one exhibits an efficiency of 82% at full
load.
Estabilización en tiempo finito de sistemas mecánicos: un estudio comparativo y algunos aspectos de robustez
Full text link"Los algoritmos de control continuos en tiempo finito son frecuentemente motivados en la literatura argumentando ventajas sobre los esquemas asintóticos, tales como mayor robustez ante incertidumbre y perturbaciones. Esto incentiva a estudiar más de cerca la certitud de estas afirmaciones y las condiciones bajo las cuales se cumplen. En este sentido, en este trabajo se consideran cuatro leyes de control continuas existentes en la literatura para la regulación de sistemas mecánicos en tiempo finito y mediante simulaciones se realiza un estudio comparativo de su desempeño. Posteriormente, se estudian analíticamente algunos aspectos de robustez de una ley de control continua para el seguimiento en tiempo finito de sistemas mecánicos con entradas acotadas, recientemente propuesta en la literatura, demostrando que ante pequeñas perturbaciones las soluciones del sistema en lazo cerrado son uniformemente ulteriormente acotadas y que su variación post transitoria alrededor de la trayectoria deseada es más pequeña en el caso en que el control es en tiempo finito que cuando es de tipo asintótico, logrando dar un sustento más sólido sobre las ventajas que presentan los controladores en tiempo finito sobre los asintóticos en relación al aspecto de robustez tratado.""Finite-time controllers are frequently motivated in the literature claiming advantages over asymptotical schemes, such as improved robustness to uncertainties and
disturbance. This has motivated us to investigate conditions under which such advantages take place. In this sense, in the first part of this work four continuous control laws
previously presented in the literature are considered —referred to here by the acronyms
HXH02GC, HXH02ID, SB15 and ZZ17— which solve the finite-time regulation problem
for mechanical systems and, through simulation implementations, a comparative study
of their performance is carried out —under different criteria— particularly under the
consideration of constrained inputs and parametric uncertainty. Subsequently, in the
second part of the thesis, in a more general context, some robustness aspects of a recently proposed continuous control law dealing with tracking of mechanical systems in
finite-time are established analytically. For this controller, it results possible to choose
among finite-time and exponential convergence of the closed-loop system responses to
desired trajectories, through a simple control parameter. It is shown then that in the
case of disturbances with sufficiently small bound, the closed-loop system solutions are
uniformly ultimately bounded and that the post transient response of the error variables around the origin is smaller for the finite-time controller than for the asymptotic
one, thus giving a stronger support on the advantages of finite-time controllers over
asymptotical ones in relation to the considered robustness aspect.
Construction of 3D self-supported electrodes of amorphous Ni(OH)2 with rationally nanostructued architecture for supercapacitor applications
Full text link"Amorphous Ni(OH)2 coating on nanostructured nickel scaffolds with rational archietcture have been successfully fabricated by a facile process of templated-directed electrodeppsition and surface oxidation treatment. Nitrocellulose membrane with interconnected fibers and fiber diameter of a few hundred nanometers was used to fabricate nanoprpous nickel (NPN) at low cost. The as-prepared NPN has interconnected pore channels with pore diameter of a few hundred nanometers providing enough inner space for the formation of Ni(OH)2 nanosheets and short pathways for fast diffusion of electrolyte ions. Upright self-supported nickel nanowire array (USNWA) and self-supported nickel nanowire array (INWA) were fabricated with porous polycarbonate template and porous polyester template, respectively. Both of USNWA and INWA can be used as miniature conductive scaffolds ensuring excellent electrical/ionic conductivity, and providing large surface area. The amorphous Ni(OH)2 nanosheets coating on the miniatuer nickel scaffold was converted from the metallic surface by oxidation treatment. The conversion of metallic surface to amorphous Ni(OH)2 nanosheets creates a stable core-shell structure, a low contact resistane and guarantees a high utilization of Ni(OH)2. Because of the material and architecture advantages, the Ni(OH)2@NPN/USNWA/INWA show enhanced electrochemical performance of ultrahigh specific capacities more than 3500 F g-1 at a current density of 5 A g-1, remarkable rate capability and excellent cycling stability. The asymmetric supercapacitor of Ni(OH)2@INWA//rGO delivers a high energy density of 53 Wh kg-1 at a power density of 395 W kg-1, and an energy density of 31 Wh kg-1 can be maintained at a power density of 4973 W kg-1. It also shows long-term stability with 91 % retention of the initial capacitance after 10000 cycles at a current density of 2 A g-1. The excellent electrochemical performance of Ni(OH)2@NPN/USNWA/INWA makes them promising for supercapacitor applications.
Identificación de zonas potenciales para exploración geotérmica aplicando imágenes ópticas multiespectrales e interferometría SAR
Full text link"La energía generada por el calor de la Tierra o energía geotérmica, que se deriva dentro de la superficie de la Tierra. Es una energía renovable clave que cubre una parte significativa de la demanda de electricidad en varios países como Estados Unidos de América (EE.UU.), Filipinas, Indonesia y México. México tiene una capacidad instalada total de 1017 MW aproximadamente, lo que representa el 14 % de la capacidad instalada global total de energía geotérmica. En este trabajo se presenta una metodología para la identificación de sitios potenciales para exploración geotérmica mediante un enfoque innovador de técnicas de percepción remota. Se utilizaron imágenes de sensores pasivos provenientes de la plataforma Landsat 8, para obtener datos de anomalías térmicas superficiales, así como de presencia de alteraciones hidrotermales empleando un Análisis de Componentes Principales (PCA). Además, mediante imágenes de Radar de Apertura Sintética (SAR) de la misión Sentinel-1 se obtuvieron datos de deformación de superficie empleando la técnica DInSAR (Interferometría Diferencial). La zona de la caldera de Acoculco, Puebla, fue elegida como el sitio de prueba, la cual ya está identificada como potencial fuente de energía geotérmica por varios estudios de la Comisión Federal de Electricidad, y que aportan información adicional para la validación de la metodología propuesta. Los datos obtenidos en el sitio estudiado se integraron y relacionaron mediante una modelación multi-paramétrica, que genera varios mapas y ayuda a identificar un sitio potencial para la exploración geotérmica. Además, la presencia de alteraciones hidrotermales, anomalías térmicas y deformaciones de superficie, apoya a ser un sitio probable para la exploración geotérmica.""The energy generated due the heat of the earth and geothermal energy is one of them, which derived within the sub-surface of the earth. This key renewable energy covers a significant share of electricity demand in several countries like United States of America (USA), Philippines, Indonesia and Mexico. Mexico has total installed capacity of 1017 MW approximately, which accounts for 14% of the total global installed capacity of geothermal energy. This work presents a methodology for the identification of potential sites for the geothermal exploration by an innovative approach of remote sensing techniques. Passive sensor images from the Landsat 8 platform were used to obtain data from superficial thermal anomalies as well as the presence of hydrothermal alteration using a Principal Component Analysis (PCA). In addition, Synthetic Aperture Radar (SAR) images of Sentinel-1 mission, surface deformation data were obtained using the DInSAR (Differential Interferometric) technique. The caldera area of Acoculco, Puebla was chosen as the test site, which is already identified as potential sources of geothermal energy by several studies of Comision Federal de Electricidad (CFE) that provide additional information for the validation of the proposed methodology. The data obtained by the studied site were integrated and related through multi-parametric modelling, which generates several maps and helps to identify a potential site for geothermal exploration. In addition, the existence of hydrothermal alteration, thermal anomalies and surface deformation supports to be a probable site for geothermal exploration.
Propiedades magnéticas de agregados de metales 3d adsorbidos sobre superficies no magnéticas
Full text linkThe magnetic elements of the 3d row of the periodic table, have been extensively studied from an experimental and theoretical points of view. The study of these systems has been encouraged because their possible applications in electronics and the magnetic recording industry. Mn is one of the most intriguing elements of this series because it has a quite peculiar magnetic and crystallographic behavior, which depends on its environment. Also, at the atomic scale, it has been observed that the aggregates have physical properties that depend on their size. It is important to highlight that the size of the structures, geometry, and mobility are influenced by the intrinsic defects of the surface and by the temperature.
In this work, phenomena related to the absorption of elements of the 3d series on noble metal surfaces and perfect graphene with defects were studied. In the first case, we report the results of the calculation of the stability, electronic and magnetic structure of the adsorption of a Mn trimer, forming a linear chain and when they are adsorbed in triangular form, on non-magnetic metal surfaces (Cu and Au) on the surface (111), using the functional theory of density. As a result, we find that the physical properties of the trimer depend on both the interaction between the Mn atoms and the surface of the substrate. Which could be studied from a qualitative analysis of the distribution of the electronic charges of the Mn/Cu(111) system [Mn/Au(111)]. The atoms that actively participate in adsorption energy are mainly those in the vicinity of the trimer. In the case of the Cu (111) substrate, there is also an important interaction with those neighbors of the second layer. On the other hand, we find that the most stable magnetic state is that in which the atoms in the trimer couple antiferromagnetically. The non-collinear and ferromagnetic states are close in energy but are less bounded. In the case of the adsorbed trimer in a triangular arrangement, two geometric configurations are described; we call them Delta and Hexagonal. We found that the Delta configuration has lower energy states compared to their counterparts in H. The energies differ energetically between 230 and 350 meV.
The second system describes the interaction of an adsorbed Ni atom in a pristine graphene network and with a simple vacancy. For this, a large cell (88) was used. The stability, electronic and magnetic structure was calculated and the influence of the adsorbed Ni atom at different sites in the network, both on the perfect graphene and in the presence of defects, was analyzed. For this, a study of the electronic localization function, charge distribution, and magnetic charge of the Ni/graphene system (pristine and vacancy) was carried out. To understand the mobility of Ni adatom on its surface, the energy barriers associated with its mobility were calculated and the characteristics of the potential energy surface along several trajectories were calculated. As a result, we find that a simple vacancy in graphene generates a total magnetic moment of 1.15 muB, which is mainly due to the magnetic contribution of the atoms with a loose bond, which suffer a break in symmetry due to the effect Jahn-Teller On the other hand, when the Ni adatom occupies the vacancy, the magnetic moment of the surface is almost null. To study the migration of Ni adatoms through the graphene network, calculations of energy barriers were performed across different points using the elastic band method (cNEB). As a result, we found that in pristine graphene the smallest barrier has a value of 224 meV. While in graphene with a simple vacancy, we found that, around the vacancy, the energy barriers are a few tens of meV, and in areas farther from the vacancy these increases to several hundreds of meV. These barriers are small enough to guarantee the mobility of the Ni adatom at room temperature.
Finally, we report the results of the growth of metallic Ni clusters based on the porosity of a graphene surface and the temperature of the system using a semi-classical molecular dynamics method. For this study, a graphene surface of 1010 nm was used with a defect concentration of 0.5% (21 single vacancies) and 200 Ni atoms smoothly deposited for 2 ns. We found that at low temperatures the islands of Ni are formed mainly by monomers. In contrast, as the temperature rises to 1600 K, the average cluster size of up to 40 atoms also increases. It should be noted that despite the easy mobility of the clusters through the network, when they find a vacancy they anchor and remain fixed, even at temperatures above 2000 K
Geometría diferencial de las curvas y ecuación de Riccati
Full text link"En este trabajo se examina el método de Darboux y Lie para obtener las ecuaciones paramétricas de las curvas tres y dos dimensionales a partir de la ecuación de Riccati que contiene los parámetros intrínsecos de las curvas como coeficientes en la ecuación. En este método se usa como herramienta principal el sistema de ecuaciones de Frenet-Serret que caracteriza la evolución de un triedro móvil formado por los vectores unitarios tangente, normal y binormal a lo largo de las curvas, llegando a dos ecuaciones de Riccati idénticas para dos funciones diferentes w y z que se expresan en función de las componentes del triedro móvil de Frenet-Serret. Para ilustrar el método se trabajan ejemplos de varias curvas notables tanto en dos como en tres dimensiones con distintos parámetros de curvatura y torsión.""In this thesis work, the Darboux-Lie method to obtain the parametric
equation of three and two-dimensional curves starting from the Riccati equation with the intrinsic parameters of the curves as coefficients
of the equation is examined.
In this method, the main tool is the system of Frenet-Serret differential equations which characterizes the evolution of the moving trihedron of unit vectors of tangent, normal and binormal along the curve.
It provides two identical Riccati equations for two different functions,
w and z, which are related to the components of the Frenet-Serret
trihedron.
To illustrate the method, several examples of noted curves are worked
out both in two and three dimensions, with various curvature and
torsion intrinsic parameters."CONACY