Análisis y simulación de un rectificador trifásico controlado Active Front End (AFE)

Este artículo presenta un resultado de investigación financiado con recursos propios en el que se expone un modelo en espacio de estados de un rectificador trifásico controlado active front end. Utilizando este modelo se deriva una ley de control orientado al voltaje (VOC), enfocado en el comportamiento como carga resistiva, factor de potencia unitario, el cual es probado mediante simulación usando el Toolbox SimPowerSystem en Simulink de Matlab®.

Nanofiltration membranes modified with aromatic polyamide dendrimers active layers

This thesis describes the modification of the commercial TFC-S nanofiltration membrane with shape-persistent dendritic architectures. Amphiphilic aromatic polyamide dendrimers (G1-G3) are synthesized via a divergent approach and used for membrane modification by direct percolation. The permeate samples collected from the percolation experiments are analyzed by UV-Vis spectroscopy to instantly monitor the influence of dendrimer generations on percolation behaviors and new active layer formation. The membrane structures are further characterized by Rutherford backscattering spectrometry (RBS) and atomic force microscopy (AFM) techniques, suggesting a low-level accumulation of dendrimers inside the TFC-S NF membranes and subsequent formation of an additional aramide dendrimer active layer. Thus, all the modified TFC-S membranes have a double active layer structure. A PES-PVA film is used as a control membrane showing that structural compatibility between the dendrimer and supports plays an important role in the membrane modification process. The performance of modified TFC-S membrane is evaluated on the basis of rejection abilities of a variety of water contaminants having a range of sizes and chemistry. As the water flux is inversely proportional to the thickness of the active layer, we optimize the amount of dendrimers deposited for specific contaminants to improve the solute rejection while maintaining high water flux.

The Repellent DEET Potentiates Carbamate Effects via Insect Muscarinic Receptor Interactions: An Alternative Strategy to Control Insect Vector-Borne Diseases.

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Brain emotional learning based control of a SDOF structural system with a MR damper

This paper describes the application of a Brain Emotional Learning (BEL) controller to improve the response of a SDOF structural system under an earthquake excitation using a magnetorheological (MR) damper. The main goal is to study the performance of a BEL based semi-active control system to generate the control signal for a MR damper. The proposed approach consists of a two controllers: a primary controller based on a BEL algorithm that determines the desired damping force from the system response and a secondary controller that modifies the input current to the MR damper to generate a reference damping force. A parametric model of the damper is used to predict the damping force based on the piston motion and also the current input. A Simulink model of the structural system is developed to analyze the effectiveness of the semi-active controller. Finally, the numerical results are presented and discussed.

Development of a 1-D Catalyzed Diesel Particulate Filter Model for Simulation of the Performance and the Oxidation of Particulate Matter and Nitrogen Oxides Using Passive Oxidation and Active Regeneration Engine Experimental Data

Back-pressure on a diesel engine equipped with an aftertreatment system is a function of the pressure drop across the individual components of the aftertreatment system, typically, a diesel oxidation catalyst (DOC), catalyzed particulate filter (CPF) and selective catalytic reduction (SCR) catalyst. Pressure drop across the CPF is a function of the mass flow rate and the temperature of the exhaust flowing through it as well as the mass of particulate matter (PM) retained in the substrate wall and the cake layer that forms on the substrate wall. Therefore, in order to control the back-pressure on the engine at low levels and to minimize the fuel consumption, it is important to control the PM mass retained in the CPF. Chemical reactions involving the oxidation of PM under passive oxidation and active regeneration conditions can be utilized with computer numerical models in the engine control unit (ECU) to control the pressure drop across the CPF. Hence, understanding and predicting the filtration and oxidation of PM in the CPF and the effect of these processes on the pressure drop across the CPF are necessary for developing control strategies for the aftertreatment system to reduce back-pressure on the engine and in turn fuel consumption particularly from active regeneration. Numerical modeling of CPF's has been proven to reduce development time and the cost of aftertreatment systems used in production as well as to facilitate understanding of the internal processes occurring during different operating conditions that the particulate filter is subjected to. A numerical model of the CPF was developed in this research work which was calibrated to data from passive oxidation and active regeneration experiments in order to determine the kinetic parameters for oxidation of PM and nitrogen oxides along with the model filtration parameters. The research results include the comparison between the model and the experimental data for pressure drop, PM mass retained, filtration efficiencies, CPF outlet gas temperatures and species (NO2) concentrations out of the CPF. Comparisons of PM oxidation reaction rates obtained from the model calibration to the data from the experiments for ULSD, 10 and 20% biodiesel-blended fuels are presented.

Flexible Power Control of Photovoltaic Plants Connected to Distribution Networks

This paper presents a system to control the power injected by a photovoltaic (PV) plant on the receiving network. This control is intended to mitigate some of the negative impacts that these units may produce on such networks, while increasing the installed power of the plant. The controlled parameters are the maximum allowed value of injected active power and the corresponding power factor, whose setpoints values may be fixed or dynamic. The developed system allows a local and a remote control. The injected power and the corresponding power factor may be set by following a predetermined profile or by real time adjustments to fulfill specific operation constraints on the receiving network. The system acts by adjusting the control parameters on the PV inverters. The main goal of the system is, in the end, to control the PV plant, ensuring the accomplishment of technical constraints and, at the same time, maximizing the installed power of the PV plant, which may be an important issue concerning the economic performance of such plants

Towards a smart semi-active prosthetic leg: preliminary assessment and testing

This paper presents a development of a semi-active prosthetic knee, which can work in both active and passive modes based on the energy required during the gait cycle of various activities of daily livings (ADLs). The prosthetic limb is equipped with various sensors to measure the kinematic and kinetic parameters of both prosthetic limbs. This prosthetic knee is designed to be back-drivable in passive mode to provide a potential use in energy regeneration when there negative energy across the knee joint. Preliminary test has been performed on transfemoral amputee in passive mode to provide some insight to the amputee/prosthesis interaction and performance with the designed prosthetic knee.

Demanda y control de la tarea y presencia de síntomas de estrés y osteo-musculares en personal de una institución hospitalaria de IV nivel, Bogotá, 2016.

El ejercicio de labores asistenciales en el personal de la salud, las largas horas de trabajo y la responsabilidad en la ejecución de sus tareas, llevan consigo la exposición a riesgos psicosociales; que de no ser debidamente controlados pueden llevar al individuo a generar respuestas inadecuadas a nivel cognitivo, emocional e intelectual, las cuales se manifiestan en algunos casos con la aparición de sintomatología osteomuscular y/o asociada al estrés. OBJETIVO Identificar la relación entre las demandas de la tarea, el control sobre las mismas y la presencia e intensidad de síntomas de estrés y osteo-musculares en médicos, especialistas y personal de enfermería de una institución hospitalaria de IV nivel en Bogotá. Métodos Estudio de corte transversal en una muestra de 100 profesionales de la salud. Se utilizaron tres instrumentos: cuestionario Nórdico para la detección y análisis de síntomas músculo esqueléticos, cuestionario Karasek para identificar la percepción del trabajo y la relación del entorno profesional y el cuestionario de Estrés del Ministerio de la Protección Social validado para la población colombiana. Se obtuvo previa autorización del Comité de Investigaciones y Comité de Ética del Hospital. El análisis estadístico se realizó con el IBM SPSS Statistics versión 2.0 Resultados Se observó que los síntomas osteomusculares con mayor prevalencia estuvieron relacionados con afectaciones en espalda 43% y cuello 36%; no se observan diferencias estadísticamente significativas entre los distintos profesionales. En cuanto a presencia de sintomatología asociada al estrés, la mayor prevalencia se presentó en síntomas osteomusculares en cuello y espalda en el 84% de los casos, dolor de cabeza en el 74%, trastornos del sueño y cansancio en el 64% y percepción de sobrecarga laboral en el 63%. Para el análisis de prevalencia de los factores psicosociales laborales se utilizó la clasificación de la combinación de altas o bajas demandas y alto o bajo control, el resultado de estos teniendo en cuenta el modelo Demanda-control fue la siguiente: trabajo de alta tensión 34%; trabajo activo 40%; trabajo aburrido 13% y trabajo pasivo 13%. Se encontró una asociación entre la sintomatología y las variables toma de decisiones en médicos especialistas (OR 3,12; IC 95%: 2,80 – 3,49) lo que ratifica que este tipo de profesional tiene una mayor libertad para generar decisiones en su actuar médico y control sobre la tarea para especialistas (OR 3,23; IC 95%: 2,82 – 3,70) y enfermeros jefes (OR 3,36; IC 95%: 2,91 – 3,89); lo que permite inferir que cada uno de estos profesionales posee las herramientas para asumir las exigencias y dar respuesta a los distintos aspectos que están ligados a la tarea. Conclusiones: La presencia de síntomas osteo musculares en zonas como cuello y espalda son propios de la actividad del personal de la salud y se asocia a las posturas inadecuadas y el puesto de trabajo, así como al estrés. En cuanto a la sintomatología asociada al estrés se ratifica la presencia de sintomatología osteo muscular (cuello y espalda), como manifestaciones asociadas al cansancio, trastornos del sueño, sobrecarga laboral, dolor de cabeza y en menor porcentaje dificultades para relacionarse con otros. Respecto a los factores de riesgo psicosocial, se observó que el trabajo activo es la condición predominante en el personal de la salud, pero se observa además que un porcentaje importante experimenta episodios de tensión laboral, asociados a condiciones propias de las demandas psicológicas y el control sobre la tarea. Por lo anterior, se deben establecer acciones encaminadas a favorecer espacios saludables, y programas tendientes a la mejora de las condiciones de tal manera que disminuya la presencia de sintomatología osteomuscular y/o sintomatología derivada del estrés.

A second order control-volume finite-element least-squares strategy for simulating diffusion in strongly anisotropic media

An unstructured mesh �nite volume discretisation method for simulating di�usion in anisotropic media in two-dimensional space is discussed. This technique is considered as an extension of the fully implicit hybrid control-volume �nite-element method and it retains the local continuity of the ux at the control volume faces. A least squares function recon- struction technique together with a new ux decomposition strategy is used to obtain an accurate ux approximation at the control volume face, ensuring that the overall accuracy of the spatial discretisation maintains second order. This paper highlights that the new technique coincides with the traditional shape function technique when the correction term is neglected and that it signi�cantly increases the accuracy of the previous linear scheme on coarse meshes when applied to media that exhibit very strong to extreme anisotropy ratios. It is concluded that the method can be used on both regular and irregular meshes, and appears independent of the mesh quality.