Sparse Linear Models applied to Power Quality Disturbance Classification

Power quality (PQ) analysis describes the non-pure electric signals that are usually present in electric power systems. The automatic recognition of PQ disturbances can be seen as a pattern recognition problem, in which different types of waveform distortion are differentiated based on their features. Similar to other quasi-stationary signals, PQ disturbances can be decomposed into time-frequency dependent components by using time-frequency or time-scale transforms, also known as dictionaries. These dictionaries are used in the feature extraction step in pattern recognition systems. Short-time Fourier, Wavelets and Stockwell transforms are some of the most common dictionaries used in the PQ community, aiming to achieve a better signal representation. To the best of our knowledge, previous works about PQ disturbance classification have been restricted to the use of one among several available dictionaries. Taking advantage of the theory behind sparse linear models (SLM), we introduce a sparse method for PQ representation, starting from overcomplete dictionaries. In particular, we apply Group Lasso. We employ different types of time-frequency (or time-scale) dictionaries to characterize the PQ disturbances, and evaluate their performance under different pattern recognition algorithms. We show that the SLM reduce the PQ classification complexity promoting sparse basis selection, and improving the classification accuracy

Analogías de redes eléctricas como herramienta educativa para el estudio de diversos fenómenos físicos

La resolución de problemas correspondientes a fenómenos físicos regidos por ecuaciones diferenciales en derivadas parciales, lineales o no, implica un conocimiento profundo de cálculo analítico o numérico por lo que, en general, estos problemas no se encuentran al alcance de los alumnos de facultades de ciencias o escuelas de ingeniería, desconocedores en su fase de formación de estas modernas y complejas técnicas matemáticas.A pesar de ello, es posible, en muchos casos, abordar la resolución de los mismos recurriendo al empleo de analogías y resolviendo los modelos formalmente equivalentes (es decir, regidos por el mismo conjunto de ecuaciones) mediante programas de ordenador adecuados a tal fin. Este es el caso de las analogías eléctricas ya que, una vez elaborado el modelo en red, se dispone de programas de resolución de circuitos de fácil manejo

Finite-dimensional Gaussian approximation with linear inequality constraints

International audienceGaussian process (GP) modulated Cox processes are widely used to model point patterns. Existing approaches require a mapping (link function) between the unconstrained GP and the positive intensity function. This commonly yields solutions that do not have a closed form or that are restricted to specific covariance functions. We introduce a novel finite approximation of GP-modulated Cox processes where positiveness conditions can be imposed directly on the GP, with no restrictions on the covariance function. Our approach can also ensure other types of inequality constraints e.g. monotonicity, convexity), resulting in more versatile models that can be used for other classes of point processes (e.g. renewal processes). We demonstrate on both synthetic and real-world data that our framework accurately infers the intensity functions. Where monotonicity is a feature of the process, our ability to include this in the inference improves results

The in-plane electrodynamics of the superconductivity in Bi2Sr2CaCu2O8+d: energy scales and spectral weight distribution

The in-plane infrared and visible (3 meV-3 eV) reflectivity of Bi2Sr2CaCu2O8+d (Bi-2212) thin films is measured between 300 K and 10 K for different doping levels with unprecedented accuracy. The optical conductivity is derived through an accurate fitting procedure. We study the transfer of spectral weight from finite energy into the superfluid as the system becomes superconducting. In the over-doped regime, the superfluid develops at the expense of states lying below 60 meV, a conventional energy of the order of a few times the superconducting gap. In the underdoped regime, spectral weight is removed from up to 2 eV, far beyond any conventional scale. The intraband spectral weight change between the normal and superconducting state, if analyzed in terms of a change of kinetic energy is ~1 meV. Compared to the condensation energy, this figure addresses the issue of a kinetic energy driven mechanism.Comment: 13 pages with 9 figures include

Nutritional status of adults and children under 5 years of age in two areas of Guatemala Project results for “His and Hers, time and income: how intra-household dynamics impact nutrition in agricultural households”.

Proyecto IMMANAIn this info-note, we explain the body mass index calculations (BMI) for adults in agricultural Guatemalan households, as well as the implementation of indicators to assess the nutritional status of children under 5 years (height for age, weight for age and weight for height). This work is part of the project “His and Hers, time and income: How intra-household dynamics impact nutrition in agricultural households,” led by the International Center for Tropical Agriculture (CIAT) and the University de Florida 1 with funding from the program Innovative Methods and Metrics for Agriculture and Nutrition Actions (IMMANA).2 The prevalence of stunting in Guatemalan children under 5 years is 46 percent, according to Guatemala’s Ministry of Public Health (INE, 2015). Stunting refers to insufficient height with respect to age. It is a consequence of inadequate socioeconomic conditions that are often associated with insufficient nutrition and health of the mother, which is in turn reflected in inadequate care of the infant. Stunting prevents children from fully developing their physical and cognitive potential (WHO, 2018). Simultaneously and paradoxically, Guatemala also shows a significant presence of overweight and obesity rates among its population. The prevalence of overweight in adults is 56% and of obesity is 21% (WHO, 2017)

Aves del departamento de Cundinamarca, Colombia: conocimiento, nuevos registros y vacíos de información

El departamento de Cundinamarca, Colombia, constituye un territorio con variedad de condiciones geográficas y ecosistémicas que hacen de este una de las regiones con mayor diversidad de aves en el país. Se actualizó el listado de aves y se determinaron los cambios en la composición, así como los vacíos de información. Se recopilaron los datos de campo de los autores entre 1990 y 2015, se revisó la literatura y las bases de datos y se consultaron observadores de aves expertos en la región. Fueron registradas 941 especies de las cuales 24 son endémicas, 72 casi endémicas, 1 especie extinta, 39 amenazadas a nivel nacional, 101 migratorias y 45 con migración local o altitudinal. En total, 701 especies fueron registradas por los autores en 45 localidades (48 registros nuevos para el departamento). Se concluye que existen vacíos de información en los límites departamentales, especialmente hacia la región del río Magdalena y los Llanos Orientales. Sin embargo, regiones donde existe mayor muestreo no se encuentran inventariadas en su totalidad, ya que en estas zonas se siguen encontrando nuevas especies de importancia para la ciencia

Aves del departamento de Cundinamarca, Colombia: conocimiento, nuevos registros y vacíos de información

The department of Cundinamarca in Colombia is an area with diverse geographic and ecosystemic characteristics, a condition that makes it one of the regions in the country with highest diversity of birds. This study updates the list of birds in the department, as well as identifies changes in composition and gaps of information, through the recopilation of field data developed by the authors from 1990 to 2015, revision of different papers and databases, and consultation of experienced birdwatchers in the region.We found 941 records of bird species, of which 24 are endemic, 72 near endemic, 1 extinct, 39 nationally threatened, 101 migratory, and 45 present local and/or altitudinal migration. Of the total number of records, 701 correspond to the authors in 45 localities (48 are new records for the department). We note that there are gaps of information in departmental boundaries, especially in the region of the Magdalena River valley and Llanos Orientales. However, regions that have been more extensively sampled are not fully inventoried since new species for science are still being found.El departamento de Cundinamarca, Colombia, constituye un territorio con variedad de condiciones geográficas y ecosistémicas que hacen de este una de las regiones con mayor diversidad de aves en el país. Se actualizó el listado de aves y se determinaron los cambios en la composición, así como los vacíos de información. Se recopilaron los datos de campo de los autores entre 1990 y 2015, se revisó la literatura y las bases de datos y se consultaron observadores de aves expertos en la región. Fueron registradas 941 especies de las cuales 24 son endémicas, 72 casi endémicas, 1 especie extinta, 39 amenazadas a nivel nacional, 101 migratorias y 45 con migración local o altitudinal. En total, 701 especies fueron registradas por los autores en 45 localidades (48 registros nuevos para el departamento). Se concluye que existen vacíos de información en los límites departamentales, especialmente hacia la región del río Magdalena y los Llanos Orientales. Sin embargo, regiones donde existe mayor muestreo no se encuentran inventariadas en su totalidad, ya que en estas zonas se siguen encontrando nuevas especies de importancia para la ciencia

Computational simulation of aerodynamic interaction between bodies for wind energy harvesting applications

Los dispositivos de cosecha de energía eólica representan una potencial alternativa a pequeñas baterías para alimentar dispositivos electrónicos de baja potencia, tales como sensores inalámbricos, transceptores de radiofrecuencia, cámaras, etc. Entre los mecanismos de cosecha de energía, se destacan los basados en los fenómenos aeroelásticos de flutter y de vibraciones inducidas por vórtices. En este artículo, se analiza el fenómeno de vibraciones inducidas por vórtices en un arreglo de dos cuerpos inmersos en una corriente de aire. Se emplea el software OpenFoam para realizar las simulaciones de CFD. Se analiza la influencia de la separación entre los cuerpos sobre la frecuencia y la amplitud de la potencia transferida por el fluido al cuerpo móvil. El fin de este estudio es cuantificar la potencialidad de estas configuraciones para su aplicación en la cosecha de energía eólica.Facultad de Ingenierí