Noise analysis of super-regenerative oscillators in linear and nonlinear modes

A rigorous analysis of noise effects in super-regenerative oscillators (SROs), operating in both linear and nonlinear modes, is presented. For operation in the linear mode, two different analysis methods are presented. One is based on the calculation of linear-time variant (LTV) transfer function with respect to the input signal and the noise sources. The second method is based on a compact semianalytical formulation of the pulsed oscillator under the effect of the quench signal. The compact formulation also enables the analysis of the SRO in the nonlinear mode. It constitutes a fully new mathematical description of SROs, with general applicability, as it is not restricted to a particular oscillator topology. It relies on a numerical nonlinear black-box model of the stand-alone free-running oscillator, extracted from harmonic-balance simulations. This model is introduced into an envelope-domain formulation of the SRO at the fundamental frequency. Both the method based on LTV transfer functions and the semianalytical formulation take into account the cyclostationary nature of the SRO response to the noise sources. In the nonlinear mode, the variances of the amplitude and phase are calculated linearizing the formulation of the pulsed steady-state solution. The particular time variation of the phase variance is explained in detail and related to the onset and extinction of the oscillation in the presence of an RF input signal. The new analysis methods have been validated with both independent circuit-level simulations and measurements.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under Project TEC2017-88242-C3-1-R

Cyclostationary noise analysis of superregenerative oscillators

A rigorous analysis of noise effects in super regenerative oscillators (SRO) operating in linear mode is presented. The analysis takes into account the cyclostationary nature of the SRO response to the noise sources, due to the effect of the quench signal. It is based on the determination of envelope-domain linear-time-variant (LTV) transfer function with respect to each noise source, plus the application of a detailed stochastic analysis of the SRO output. Initially, the autocorrelation of the output signal is calculated, which varies at two different time scales, and is periodic with respect to the quench signal, so it can be expressed in terms of the frequency-dependent harmonic components of the LTV transfer functions. This enables the calculation of the output spectral density, depending on these harmonic components. Once the spectral density is known, the signal-to-noise ratio can be obtained in a straightforward manner. The analysis method has been validated with both independent circuit-level simulations and measurementsThis 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

EFFECTS OF LOUVERS SHADING DEVICES ON VISUAL COMFORT AND ENERGY DEMAND OF AN OFFICE BUILDING. A CASE OF STUDY

This paper evaluates the building energy demand and visual comfort of a real case with a glazed façade office building placed in Málaga (Mediterranean city in the south of Spain). South oriented facades receive such a high solar gain that cooling demand cannot be handled by the current HVAC system. As an environmental friendly solution, a shading control strategy based on vertical and horizontal louvers is proposed. The study consists of a comparison between the actual and the refurbished building with shading devices. Daylighting simulation is done with Daysim (Daysim, 2016). A group of offices with south, east and north oriented facades is chosen for the study. Horizontal louvers in the south façade and vertical louvers in the east facade are modelled and simulated. The simulation changes the angle of the louver: 0º (perpendicular to the glazing), -30º, 30º, -60º, 60º. Visual comfort parameters analyzed are: illuminance, daylight autonomy (DA) and useful daylight index (UDI). With respect to the thermal comfort, not only louvers orientation try to provide solar protection for glazed areas in cooling period but also maximize solar gains in heating period. However, an excessive daylight could affect discomfort glare. Shading control strategy must provide the equilibrium between both aspects. Thermal demand is calculated with Trnsys (TRNSYS, 2016).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Revisión de la producción científica sobre webquest en los últimos 20 años: análisis bibliométrico en scopus y web of science

Tras la primera formulación en 1995 sobre qué es una Web Quest ¿cuál es el estado de su desarrollo en el campo de la educación? Esta pregunta exige muchas miradas y respuestas. Este trabajo busca ser parte de esta evaluación poniendo en evidencia el desarrollo de la producción científica sobre WebQuest en las dos principales bases de datos científicas: WOS (Web of Science) y Scopus desde su formulación hasta la actualidad (1995-2014). El método es el análisis bibliométrico en base a las siguientes variables: número de artículos publicados, número de citas recibidas, principales revistas citantes, promedio de citas por año, nombre y país de los autores más citados y palabras clave. Se ha procedido a la identificación del perfil y las características de las publicaciones científicas que lo tratan, sobre la conclusión de una evidente dispersión y atomización de resultados, destacando la existencia de una significativa comunidad científica sobre Webquest en Españ

Experimental measurement of the quality factor of a Fabry-P\'erot open-cavity axion haloscope

The axion is a hypothetical boson arising from the most natural solution to the problem of charge and parity symmetry in the strong nuclear force. Moreover, this pseudoscalar emerges as a dark matter candidate in a parameter space extending several decades in mass. The Dark-photons \& Axion-Like particles Interferometer (DALI) is a proposal to search for axion dark matter in a range that remains under-examined. Currently in a design and prototyping phase, this haloscope is a multilayer Fabry-P\'erot interferometer. A proof-of-principle experiment is performed to observe the resonance in a prototype. The test unveils a quality factor per open cavity of a few hundred over a bandwidth of the order of dozens of megahertz. The result elucidates a physics potential to find the, so far elusive, axion, in a sector which can simultaneously solve the symmetry problem in the strong interaction and the enigma of dark matter.Comment: 5 pages, 6 figure

Retrospective health impact assessment for ozone pollution in Mexico City from 1991 to 2011

AbstractAir pollution is the main environmental issue in Mexico City, where ozone is one of the most damaging pollutants for human health. In this work we present a retrospective health impact assessment (HIA) study split up by age groups for evaluating the benefits of ozone regulatory strategies from 1991 to 2011 in Mexico City. Since people move from one place to another during the day, which may affect their potential exposure to pollutants, we consider time-dependant spatial population distributions during the day. Ozone data is made up of observations taken with hourly frequency from January 1, 1991 to December 31, 2011, at approximately 22 stations of the monitoring network of Mexico City. Interpolated values for unknown locations are also taken into account in the HIA. The Cressman objective analysis method is applied for interpolating the observed ozone concentrations from monitoring stations to grids of convenient resolution. We demonstrate that different age groups present different spatial patterns of exposure, being the working-age people (between 18 and 64 years) the most benefited. We also confirm the hypothesis that, in general, people move to less polluted regions during the day

Brain MRI study for glioma segmentation using convolutional neural networks and original post-processing techniques with low computational demand

Gliomas are brain tumors composed of different highly heterogeneous histological subregions. Image analysis techniques to identify relevant tumor substructures have high potential for improving patient diagnosis, treatment and prognosis. However, due to the high heterogeneity of gliomas, the segmentation task is currently a major challenge in the field of medical image analysis. In the present work, the database of the Brain Tumor Segmentation (BraTS) Challenge 2018, composed of multimodal MRI scans of gliomas, was studied. A segmentation methodology based on the design and application of convolutional neural networks (CNNs) combined with original post-processing techniques with low computational demand was proposed. The post-processing techniques were the main responsible for the results obtained in the segmentations. The segmented regions were the whole tumor, the tumor core, and the enhancing tumor core, obtaining averaged Dice coefficients equal to 0.8934, 0.8376, and 0.8113, respectively. These results reached the state of the art in glioma segmentation determined by the winners of the challenge.Comment: 34 pages, 12 tables, 23 figure

Automatic quantification of abdominal subcutaneous and visceral adipose tissue in children, through MRI study, using total intensity maps and Convolutional Neural Networks

Childhood overweight and obesity is one of the main health problems in the world since it is related to the early appearance of different diseases, in addition to being a risk factor for later developing obesity in adulthood with its health and economic consequences. Visceral abdominal tissue (VAT) is strongly related to the development of metabolic and cardiovascular diseases compared to abdominal subcutaneous adipose tissue (ASAT). Therefore, precise and automatic VAT and ASAT quantification methods would allow better diagnosis, monitoring and prevention of diseases caused by obesity at any stage of life. Currently, magnetic resonance imaging is the standard for fat quantification, with Dixon sequences being the most useful. Different semiautomatic and automatic ASAT and VAT quantification methodologies have been proposed. In particular, the semi-automated quantification methodology used commercially through the cloud-based service AMRA R Researcher stands out due to its extensive validation in different studies. In the present work, a database made up of Dixon MRI sequences, obtained from children between 7 and 9 years of age, was studied. Applying a preprocessing to obtain what we call total intensity maps, a convolutional neural network (CNN) was proposed for the automatic quantification of ASAT and VAT. The quantifications obtained from the proposed methodology were compared with quantifications previously made through AMRA R Researcher. For the comparison, correlation analysis, Bland-Altman graphs and non-parametric statistical tests were used. The results indicated a high correlation and similar precisions between the quantifications of this work and those of AMRA R Researcher. The final objective is that the proposed methodology can serve as an accessible and free tool for the diagnosis, monitoring and prevention of diseases related to childhood obesity.Comment: 14 pages, 9 figures, 3 table

Perfil de función y discapacidad en pacientes pediátricos ambulatorios con cáncer

Introducción. El cáncer infantil, aunque tiene una baja prevalencia, genera un alto impacto en las metas de desarrollo y funcionalidad esperadas para la edad, impacto que puede ser descrito utilizando la nomenclatura propuesta por la Clasificación Internacional del Funcionamiento, la Discapacidad y la Salud (CIF). Objetivo. Describir los perfiles de función y discapacidad de los pacientes menores de 18 años atendidos en consulta externa del Servicio de Rehabilitación Oncológica del Instituto Nacional de Cancerología de Bogotá (Colombia). Métodos. Estudio observacional retrospectivo de corte transversal. Se construyeron perfiles de función y discapacidad mediante análisis de correspondencia múltiple. Resultados. Se incluyeron 127 historias clínicas analizadas en tres grupos etarios. En el de 0 a 5 años (15,75%) predominó la leucemia linfoblástica (40%) y los tumores de sistema nervioso central (20%), con mayor compromiso en estructuras del sistema nervioso, funciones sensoriales y la movilidad. En el de 6 a 10 años (19,68%) el diagnóstico más frecuente fue el tumor del sistema nervioso central (56%), con mayor compromiso en dominios de actividades y participación. En el de 11 a 18 años (64,56%) predominaron los tumores osteomusculares (52,43%), con compromiso en estructuras relacionadas con el movimiento, funciones sensoriales relacionadas con el dolor, funciones neuromusculoesqueléticas y restricciones para la movilidad y para la participación en actividades principales de la vida. Conclusión. El dominio funcionalcon mayor peso estadístico en la construcción de los perfiles funcionales es el de actividades y participación, el cual debe ser evaluado con medidas ajustadas a la edad para facilitar el seguimiento de rehabilitación en términos de metas del desarrollo y participación esperada para la edad

Revisión de la producción científica sobre WebQuest en los últimos 20 años: análisis bibliométrico en Scopus y Web of Science

Tras la primera formulación en 1995 sobre qué es una Web Quest ¿cuál es el estado de su desarrollo en el campo de la educación? Esta pregunta exige muchas miradas y respuestas. Este trabajo busca ser parte de esta evaluación poniendo en evidencia el desarrollo de la producción científica sobre WebQuest en las dos principales bases de datos científicas: WOS (Web of Science) y Scopus desde su formulación hasta la actualidad (1995-2014). El método es el análisis bibliométrico en base a las siguientes variables: número de artículos publicados, número de citas recibidas, principales revistas citantes, promedio de citas por año, nombre y país de los autores más citados y palabras clave. Se ha procedido a la identificación del perfil y las características de las publicaciones científicas que lo tratan, sobre la conclusión de una evidente dispersión y atomización de resultados, destacando la existencia de una significativa comunidad científica sobre Webquest en España.