A control system for reducing the hydrogen consumption of PEM fuel cells under parametric uncertainties

Este artículo presenta un sistema de control para reducir el consumo de hidrogeno para una celda de combustible de Membrana de Intercambio Protónico, considerando incertidumbres paramétricas. El sistema de control incluye un modelo no lineal en el espacio de estado para la celda de combustible, un filtro de Kalman/estimador, un regulador óptimo cuadrático y algoritmo de seguimiento de puntos de máxima potencia (MPP). El objetivo de control es suministrar la potencia de carga demandada, evitando el agotamiento del oxígeno y minimizando el consumo de hidrógeno por medio de un algoritmo de Perturbación y Observación (P&O). El desempeño del sistema de control es evaluado ante incertidumbres paramétricas al simular escenarios de perdida de desempeño como producto del envejecimiento del compresor. De esta forma, dos escenarios fueron simulados: un primer escenario simula un error entre la ganancia (de lazo abierto) del compresor de la celda de combustible y la del modelo; y un segundo escenario, con un error entre la corriente de pérdidas y del compresor de la celda de combustible con respecto al modelo. Los resultados de simulación muestran que el filtro Kalman/estimador logra contrarrestar las incertidumbres producidas por los cambios paramétricos del sistema. Igualmente, el algoritmo MPP logra suministrar el voltaje del compresor adecuado sin necesidad de un perfil óptimo en condiciones ideales.This paper presents a control system for reducing the hydrogen consumption for a Polymer Electrolyte Membrane fuel cell, also considering parametric uncertainties. The control system is based on a non-linear state space model of the fuel cell, a Kalman filter/estimator, a linear state feedback controller and a Maximum Power Point (MPP) tracking algorithm. The control objective is to supply the requested load power, avoiding oxygen starvation with minimum fuel consumption using a Perturb and Observe (P&O) algorithm. The performance of the control system was assessed under parametric uncertainties by simulating a performance degradation of the compressor due to aging. Thus, two cases were simulated: first, a mismatch between the system and the linear model in the (open-loop) air compressor gain; and second, a mismatch between the system and the linear model in the current compressor and losses. The simulation results showed that the Kalman filter/estimator overcome the uncertainties produced by the parametrical variations. Besides, the P&O algorithm accomplished to provide the suitable compressor voltage without identifying an optimal profile under ideal operating conditions and empirical data

MED 25 años: el nacimiento de una idea hecha realidad

Nos sentimos honrados y agradecidos de tener la oportunidad de contar la historia nunca antes contada sobre cómo surgió Med. Honrados por haber sido los estudiantes que fundaron la revista y agradecidos con todos aquellos que en estos 25 años han mantenido vivo ese sueño casi inalcanzable de tener un órgano de difusión científica de la Facultad de Medicina de la Universidad Militar Nueva Granada y el Hospital Militar Central. Gracias a 25 años de esfuerzos continuos, la esencia de Med sigue intacta, ser una revista médica propia, en busca de la excelencia, de todos y para todos

XVI International Congress of Control Electronics and Telecommunications: "Techno-scientific considerations for a post-pandemic world intensive in knowledge, innovation and sustainable local development"

Este título, sugestivo por los impactos durante la situación de la Covid 19 en el mundo, y que en Colombia lastimosamente han sido muy críticos, permiten asumir la obligada superación de tensiones sociales, políticas, y económicas; pero sobre todo científicas y tecnológicas. Inicialmente, esto supone la existencia de una capacidad de la sociedad colombiana por recuperar su estado inicial después de que haya cesado la perturbación a la que fue sometida por la catastrófica pandemia, y superar ese anterior estado de cosas ya que se encontraban -y aún se encuentran- muchos problemas locales mal resueltos, medianamente resueltos, y muchos sin resolver: es decir, habrá que rediseñar y fortalecer una probada resiliencia social existente - producto del prolongado conflicto social colombiano superado parcialmente por un proceso de paz exitoso - desde la tecnociencia local; como lo indicaba Markus Brunnermeier - economista alemán y catedrático de economía de la Universidad de Princeton- en su libro The Resilient Society…La cuestión no es preveerlo todo sino poder reaccionar…aprender a recuperarse rápido.This title, suggestive of the impacts during the Covid 19 situation in the world, and which have unfortunately been very critical in Colombia, allows us to assume the obligatory overcoming of social, political, and economic tensions; but above all scientific and technological. Initially, this supposes the existence of a capacity of Colombian society to recover its initial state after the disturbance to which it was subjected by the catastrophic pandemic has ceased, and to overcome that previous state of affairs since it was found -and still is find - many local problems poorly resolved, moderately resolved, and many unresolved: that is, an existing social resilience test will have to be redesigned and strengthened - product of the prolonged Colombian social conflict partially overcome by a successful peace process - from local technoscience; As Markus Brunnermeier - German economist and professor of economics at Princeton University - indicates in his book The Resilient Society...The question is not to foresee everything but to be able to react...learn to recover quickly.Bogot

Estudio zonal de películas de GaInAsSb/GaSb por fotorreflectancia

Por medio de la técnica de fotorreflectancia en el Infrarrojo cercano (FR-IR) se realizó el estudio zonal en la superficie de dos películas de Ga 1-X In X As Y Sb 1-Y fabricadas por la técnica de epitaxia en fase líquida. Las muestras AS12 y M45TQ fueron crecidas a 529 °C y 530 °C respectivamente, sobre sustratos de GaSb:Te con orientación cristalográfica (100), a partir de dos soluciones que difieren levemente en el contenido de As. Los espectros fueron tomados a una temperatura de 12 K para diferentes posiciones espaciales en la superficie de las películas y analizados con expresiones reportadas extensamente en la literatura especializada. De los respectivos análisis se obtuvieron para cada una de las muestras las dependencias de las energías de transición y los parámetros de ensanchamiento con la posición espacial. En este trabajo también se presenta el estudio comparativo de la respuesta óptica de cada material, logrando identificar las zonas espaciales en las cuales las muestras exhiben mayor densidad de defectos

Virtual BUOY: A video-based approach for measuring near-shore wave peak period

A new approach to estimate the peak period using time stack images from a video monitoring system is presented. The method is an improvement of the one developed by Stockdon and Holman (Stockdon, H.F., Holman, R.A., 2000. Estimation of wave phase speed and nearshore bathymetry from video imagery. J. Geophys. Res. Ocean. 105, 22015–22033), (S&H) including thresholding of the image to automatically identify free foam zone in the image, improved filtering procedure and windowing of the pixel intensity series in order to avoid noisy signals and spectral leakage. Results are tested against measurements in four beaches showing an absolute error below 2 s for 75% of the analyzed images despite the variable light conditions and noisy signals. Comparison with the S&H method is given showing that the new method reduces relative error on average by 28%. These results are achieved without taking into account the camera configuration requiring only the identification of a representative amount of land pixels in order to adequately eliminate noisy signals produced by environmental light fluctuations.Authors acknowledge financial support from Convocatoria Nacional de proyectos para el fortalecimiento de la investigación, creación e innovación de la Universidad Nacional de Colombia through project “Analysis of the hydrodynamic and morphodynamic characteristics of a sandy beach by means of numerical modeling and image processing” and “Estrategia de transformación del sector energético Colombiano en el horizonte de 2030″ supported by Colciencias Ecosistema Científico Contract FP44842-210-2018, as well as from the Spanish MINECO/FEDER through project MUSA(CTM-2015-66225-C2-2-P). The authors also wish to express thanks to the OCEANICOS, MARUM, IMEDEA and SOCIB research groups for the data used in this work. Data from the HZG COSYNA “Bunkerhill” wave buoy was obtained from the open COSYNA data portal. This work was partially performed while A. Orfila was a visiting scientist at the Earth, Environmental and Planetary Science Department at Brown University through a Ministerio de Ciencia, Innovacion y Universidades fellowship (PRX18/00218).Peer reviewe

Analysis of the airflow features and ventilation efficiency of an Ultra-Clean-Air operating theatre by qDNS simulations and experimental validation

Ultra-Clean-Air (UCA) operating theatres aim to minimise surgical instrument contamination and wound infection through high flow rates of ultra-clean air, reducing the presence of Microbe Carrying Particles (MCPs). This study investigates the airflow patterns and ventilation characteristics of a UCA operating theatre (OT) under standard ventilation system operating conditions, considering both empty and partially occupied scenarios. Utilising a precise computational model, quasi-Direct Numerical Simulations (qDNS) were conducted to delineate flow velocity profiles, energy spectra, distributions of turbulent kinetic energy, energy dissipation rate, local Kolmogorov scales, and pressure-based coherent structures. These results were also complemented by a tracer gas decay analysis following ASHRAE standard guidelines. Simulations showed that contrary to the intended laminar regime, the OT’s geometry inherently fosters a predominantly turbulent airflow, sustained until evacuation through the exhaust vents, and facilitating recirculation zones irrespective of occupancy level. Notably, the occupied scenario demonstrated superior ventilation efficiency, a phenomenon attributed to enhanced kinetic energy induced by the additional obstructions. The findings underscore the critical role of UCA-OT design in mitigating MCP dissemination, highlighting the potential to augment the design to optimise airflow across a broader theatre spectrum, thereby diminishing recirculation zones and consequently reducing the propensity for Surgical Site Infections (SSIs). The study advocates for design refinements to harness the turbulent dynamics beneficially, steering towards a safer surgical environment

Celebración día del médico

Evento realizado en la Universidad del Rosario dentro del marco de la celebración del día del médico en el año 2019. Se dan a conocer los resultados de la totalidad de la gran encuesta en salud, en ciencia, tecnología e innovación, en la que participaron más de 5.300 personas y que permitió conocer que piensa el ecosistema de salud, sobre ciencia y tecnología, educación, bienestar de los investigadores, propuestas que desde el foco ciencias de la vida y de la salud se hacen al gobierno nacional desde la Misión de Sabios

Reflexiones y aportes a la construcci?n de paz desde la Universidad del Tolima

144 p

Predicting critical illness on initial diagnosis of COVID-19 based on easily obtained clinical variables: development and validation of the PRIORITY model

Objectives: We aimed to develop and validate a prediction model, based on clinical history and examination findings on initial diagnosis of coronavirus disease 2019 (COVID-19), to identify patients at risk of critical outcomes. Methods: We used data from the SEMI-COVID-19 Registry, a cohort of consecutive patients hospitalized for COVID-19 from 132 centres in Spain (23rd March to 21st May 2020). For the development cohort, tertiary referral hospitals were selected, while the validation cohort included smaller hospitals. The primary outcome was a composite of in-hospital death, mechanical ventilation, or admission to intensive care unit. Clinical signs and symptoms, demographics, and medical history ascertained at presentation were screened using least absolute shrinkage and selection operator, and logistic regression was used to construct the predictive model. Results: There were 10 433 patients, 7850 in the development cohort (primary outcome 25.1%, 1967/7850) and 2583 in the validation cohort (outcome 27.0%, 698/2583). The PRIORITY model included: age, dependency, cardiovascular disease, chronic kidney disease, dyspnoea, tachypnoea, confusion, systolic blood pressure, and SpO2 ≤93% or oxygen requirement. The model showed high discrimination for critical illness in both the development (C-statistic 0.823; 95% confidence interval (CI) 0.813, 0.834) and validation (C-statistic 0.794; 95%CI 0.775, 0.813) cohorts. A freely available web-based calculator was developed based on this model (https://www.evidencio.com/models/show/2344). Conclusions: The PRIORITY model, based on easily obtained clinical information, had good discrimination and generalizability for identifying COVID-19 patients at risk of critical outcomes