Preparación y caracterización de micro esferas huecas de hematita por el método sol gel

Publicación a texto completo no autorizada por el autorReporta la formación de microesferas huecas de α-Fe2O3 (hematita), mediante el método de burbujeo. Técnica que es sencilla, porque no demanda plantillas, surfatactes, condiciones especiales de presión o pasos complejos. Para concretar ese propósito, lo primero que realizamos fue comprobar la generación de esferas huecas cristalizadas de hematita hueca, para ello, se reaccionaron nitrato férrico nanohidratado y ácido cítrico en agua con el método sol-gel. Luego, esta mezcla se sometió a un horno tubular en atmósfera de aire a temperaturas entre 180 y 600ºC. Se reporta burbujeo entre 550 y 600º C -después de producida la condensación. La morfología y evolución de cristal, fue sometida a estudio mediante difracción de rayos-X, microscopio electrónico de barrido, espectroscopía Mössbauer, termogravimetría y dispersión a pequeño ángulo (SAXS). La muestra consistió en una mixtura de magnetita, maghemita y hematita. Se calentó entre 250-400ºC. En ella observamos que la fase cristalizada de hematita se formó adoptando la forma de microesferas huecas; las mismas que se obtuvieron, luego de su cocimiento entre 500 y 600ºC. De ese modo, se demostró que la cristalización y la medida de las esferas de hematita se incrementan con la temperatura. Las medidas magnéticas registradas, sugieren claramente la transición de Morin en las esferas huecas. Además, se presenta un modelo para la formación de las microesferas huecas de hematita sin plantillas duras.Tesi

Analysis of high-order sub-harmonically injection-locked oscillators

High-order subharmonically injection-locked oscillators have recently been proposed for low phase-noise frequency generation, with carrier-selection capabilities. This work focuses on the analysis of this frequency-synthesis procedure, with emphasis on the oscillator capability to discriminate the input tones, under the variation of a tuning voltage. The oscillator is described with an analytical envelopedomain formulation, leading to an expression for the oscillator phase shift with respect to the input source. The average of this phase shift is shown to evolve in a continuous manner in the distinct synchronization bands obtained versus the tuning voltage. Then, the subsynchronized operation at a high frequency ratio (N = 30) is considered, showing the applicability of envelopedomain simulations under various Fourier decompositions and sampling rates. The synchronization bands are obtained through the phase averaging technique. The analysis has been applied to a prototype at 2.7 GHz that has been manufactured and measured.This work was supported by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (ERDF/FEDER) under the research project TEC2017-88242-C3-1-R

Analysis of superregenerative oscillators in nonlinear mode

Superregenerative oscillators in a nonlinear mode are investigated in detail using methodologies based on envelope transient, complemented with additional algorithms. A maximum-detection technique is applied to obtain the input-power threshold for nonlinear operation under different implementations of the quench signal. A mapping procedure enables the prediction of hangover and self-oscillation effects. It is based on the detection of the sequence of local maxima in the envelope amplitude after the application of a single input pulse. Using a contour-intersection method, and depending on the analysis time interval, it is possible to quantify the hangover effects and obtain the oscillation boundary, in terms of any two significant parameters. Then, a compact time-variant behavioral model is derived, valid in the absence of hangover and self-oscillation effects. It consists of a single time-variant Volterra kernel and is applicable provided that the amplitude transitions occur outside the sensitivity interval. Various methodologies are tested in a practical FET-based oscillator at 2.7 GHz. The prototype has been manufactured and measured, obtaining good agreement with the analysis results.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under the research project TEC2017-88242-C3-1-R

The potential of drama techniques in the bilingual classroom: A new perspective on Social Theatre with a focus on Infant Education

Theatre has been used in education since middle ages and this has been reflected in the successive educational laws. However, global society has brought about two requirements to our schools: learning a second language and the development of cultural and social awareness. Social Theatre seems to give an answer to both needs, being not just a tool for real communication in the bilingual classroom but a way to achieve the required holistic and comprehensive child development, considering always a ludic approach. That is why this study would like to demonstrate the potential of socio-bilingual drama techniques in the infant education classroom, focusing on the adaptation of Listening Theatre (Mato, 2006), Poor Theatre (Grotowski, 1970) and Theatre of the Oppressed (Boal, 1992) techniques in the CLIL context

Systematic methodology for the global stability analysis of nonlinear circuits

A new methodology for the detection of Hopf, flip, and turning-point bifurcations in nonlinear circuits analyzed with harmonic balance (HB) is presented. It enables a systematic determination of bifurcation loci in terms of relevant parameters, such as input power, input frequency, and bias voltages, for instance. It does not rely on the use of continuation techniques and is able to globally provide the entire loci, often containing multivalued sections and/or disconnected curves, in a single simulation. The calculation of Hopf and flip bifurcations is based on the extraction of a small-signal admittance/impedance function from HB and the calculation of its zeros through a geometrical procedure. The method is ideally suited for the investigation of the global stability properties of power amplifiers and other nonlinear circuits. The turning-point locus, associated with either jump phenomena or synchronization, is obtained by taking into account the annihilation/generation of steady-state solutions that is inherent to this type of bifurcation. A technique is also presented for the exhaustive calculation of oscillation modes in multidevice oscillators and oscillators loaded with multiresonance networks. The new methodologies are illustrated through their application to a power amplifier and a multimode oscillator.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under research projects TEC2014-60283-C3-1-R and TEC2017-88242-C3-1-R

Envelope-domain analysis and modeling of super-regenerative oscillators

An envelope-domain methodology for the numerical modeling of super-regenerative oscillators (SROs) is presented. The main advantage is its generality of application to transistor-based oscillators with arbitrary topology. Initially, a stability analysis of the nonoscillatory steady-state solution, forced by the quench signal, is performed. It is based on the calculation of a linear-time-variant (LTV) transfer function, obtained by linearizing the circuit envelope-domain equations about the nonoscillatory regime. Under moderate quench frequencies, it will be possible to estimate the SRO normalized envelope and sensitivity function from the detected dominant pair of complex-conjugate poles. In the general case, the SRO oscillatory response is modeled with a numerical method, valid under linear operation with respect to the input signal. This is based on the calculation of the LTV impulse response from a time-frequency transfer function obtained under a small-signal sinusoidal excitation. The LTV impulse response enables a straightforward determination of the sensitivity time interval and time distance to the envelope maximum. An integral expression, in terms of the LTV transfer function, will provide the SRO response to any small-signal input with any arbitrarily carrier frequency and modulation. The methodology has been successfully validated through its application to an SRO at 2.7 GHz, which has been manufactured and measured.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under Research Project TEC2014-60283-C3-1-R and Research Project TEC2017-88242-C3-1-

Actividades de refuerzo para estudiantes de once grado alrededor de sus habilidades comunicativas en matemáticas: una alternativa de preparación para el ingreso a la universidad

Exponemos en este documento algunos resultados de una investigación cualitativa que tiene como objetivo diseñar experiencias que posibiliten el desarrollo de habilidades comunicativas (NCTM, 2000) en estudiantes de once grado, y analizar como dichas habilidades contribuyen en el progreso de su pensamiento algebraico. Este estudio surge para atender una problemática identificada en estudiantes de nuevo ingreso a la universidad, quienes en una prueba inicial dejan ver que sus respuestas incorrectas refieren más a su baja interpretación de enunciados que a la incorrecta aplicación de algoritmos. Para la consecución de dicho objetivo se diseña e implementa un plan de intervención con algunos casos de estudio, quienes en las primeras etapas de implementación del plan diseñado recaen en las mismas dificultades

Presaberes matemáticos con los que ingresan estudiantes a la universidad

Exponemos en este documento los resultados de un estudio realizado en el año 2012 que consistió en la elaboración e implementación de una prueba diagnóstica para identificar algunos presaberes matemáticos con los que ingresan los estudiantes a la universidad. Dicha prueba tiene como propósito establecer su nivel de desempeño en los componentes variacional y algebraico. Para el diseño de este instrumento se tomó como apoyo las competencias matemáticas enunciadas por los lineamientos curriculares de matemáticas (Ministerio de Educación de Colombia MEN, 1997) y los estándares básicos de matemáticas para Colombia (Ministerio de educación de Colombia MEN, 2006), fue aplicada a 255 estudiantes matriculados en el curso de cálculo diferencial. El desempeño de los estudiantes fue básico presentando mayor dificultad en el componente variacional

Literature and PBLL in the EFL Secondary Education Classroom: A Literary Project about Women Writers

This dissertation seeks to prove that a literary project about women writers and feminism can help a group of students in 2nd year of ESO to develop their key competences, as well as their communicative competence, at the same time they work on curricular themes and values such as gender awareness and equality. With this study, I also intend to demonstrate that students’ interest in literature and poetry, which is the chosen genre, can increase thanks to a literary project. In order to conduct this research, I reviewed the most important literature on Second Language Acquisition (SLA), Communicative Language Teaching (CLT), Project-Based Learning (PBL) and Project-Based Language Learning (PBLL), together with works about the use of literature in the EFL classroom, in order to lay the theoretical foundations of this work. Then, I designed some tools so as to select literary texts appropriate for the students’ level. Next, I conducted a pre-test to evaluate their needs and level. Afterwards, I designed the project following the aforementioned theoretical framework, as well as the curricular framework that governs the teaching of English as a Foreign Language (EFL) in Spain. The implementation of this project, together with a post-test, revealed that the students’ communicative competence and gender awareness actually improved, as they successfully completed the project’s challenge and proved to have learnt about feminism by communicating in English. Finally, this study has also uncovered some issues related to the use of literature in the EFL classroom, such as the time necessary to conduct a literary project successfully, which may help other teachers implement this type of project.<br /

Natural language processing and semantic technologies. The application on Brand Rain and Anpro21

Este artículo presenta la aplicación y resultados obtenidos de la investigación en técnicas de procesamiento de lenguaje natural y tecnología semántica en Brand Rain y Anpro21. Se exponen todos los proyectos relacionados con las temáticas antes mencionadas y se presenta la aplicación y ventajas de la transferencia de la investigación y nuevas tecnologías desarrolladas a la herramienta de monitorización y cálculo de reputación Brand Rain.This paper presents the application and results on research about natural language processing and semantic technologies in Brand Rain and Anpro21. The related projects are explained and the obtained benefits from the research on this new technologies developed are presented. All this research have been applied on the monitoring and reputation system of Brand Rain