Displacer-type liquid level sensor with liquid density auto-compensation

In the classic displacer-type liquid level measuring method, liquid level is calculated via the buoyancy force exerted by the liquid on a displacer. This technology has high linearity, precision, accuracy, ease of installation and low cost. Nonetheless, displacer level sensors have significant sensitivity to variations in liquid density, which hinder its use in industrial applications that such quantity is not held constant. In this paper a novel displacer-type liquid level sensor is presented and analyzed. The innovation of the new sensor consists of adding another displacer and thus calculating the new measured value by the quotient of the buoyancy forces of both displacers. Therefore, the new measurement is ideally insensitive to the variations in liquid density. A prototype was built and prototype results presented high linearity, being able to mitigate the sensitivity to the liquid density, increasing accuracy in the measurements

Inductancia Umbral Transitoria de un Convertidor Reductor para el Método de Espacio de Estados

En este trabajo se analiza el comportamiento del modelo en el espacio de estados del convertidor reductor bajo la condición de frontera entre el modo de conducción continuo y discontinuo. El modelo matemático que representa el convertidor, está desarrollado específicamente para el modo de conducción continua, y apoyándonos en este, es caracterizado su comportamiento dinámico cuando se acerca al punto umbral entre los modos de conducción. De esta forma es posible comprender los efectos que produce la proximidad al punto umbral sobre la respuesta del convertidor, cómo se comporta la respuesta transitoria y estable, lo que permite conocer si el comportamiento del modelo es parcial o totalmente utilizable. Como novedad, se determinas las condiciones limitantes del modelo con respecto a la operación cercana del punto umbral, entre conducción continua o discontinua y qué tipo de respuesta es la correcta en la simulación

Mechanical behavior and water absorption in sisal/glass hybrid composites

This study aimed to assess the effect of hybridization on thermomechanical properties and water absorptionof composite materials, by introducing sisal fiber tissue into the material. To that end, two composite materialplates were manufactured, the first with five layers of E-glass reinforcement mat and the second with threelayers of E-glass fiber interspersed with two layers of sisal fibers, both used as an orthophthalic polyesterresin matrix. The material was then submitted to tensile, three-point bending and water absorption tests. Itwas observed that hybridization causes a change in both the final strength and stiffness of the material.Keywords: Composite material, water absorption, mechanical properties, natural fibers

A comparison between S-N Logistic and Kohout-Věchet formulations applied to the fatigue data of old metallic bridges materials

A new formulation of a Logistic deterministic S-N curve is applied to fatigue data of metallic materials from ancient Portuguese riveted steel bridges. This formulation is based on a modified logistic relation that uses three parameters to fit the low-cycle- (LCF), finite-life- and high-cycle-fatigue (HCF) regions. This model is compared to the Kohout-Věchet fatigue model, which has a refined adjustment from very low-cycle fatigue (VLCF) to very high-cycle fatigue (VHCF). These models are also compared with other models, such as, Power law and fatigue-life curve from the ASTM E739 standard. The modelling performance of the S-N curves was made using the fatigue data considering the stress fatigue damage parameter for the materials from the Eiffel, Luiz I, Fão and Trezói riveted steel bridges. Using a qualitative methodology of graphical adjustment analysis and another quantitative using the mean square error, it was possible to evaluate the performance of the mean S-N curve formulation. The results showed that the formulation of the S-N curve using the Logistic equation applied to the metallic materials from the old bridges obtained superior performance to the analysed models, both in the estimation of fatigue behaviour in the low-cycle fatigue (LCF) region and in the lowest mean square error

Fatigue damage mechanism and failure prevention in fiberglass reinforced plastic

Damaging of composite laminates was monitored during fatigue tests, revealing the formation and propagation stages for compressive, tensile, or alternate cyclic loading. Two different laminate stacking sequences, with different number of layers, were tested. The laminates consisted of E-glass fibers reinforced orthoftalic polyester resin (FGRP) shaped as mats or (bi-direction) woven fabric textile. Preliminary density, calcination tests and static compressive and tensile mechanical tests were carried out. Then, tensile (R = 0.1), compressive (R = 10) and alternate axial (R = - 1) fatigue tests were performed at different maximum stresses. Tensile cyclic loading resulted in crack formation and propagation confirming the findings reported in other studies. On the other hand, damage from alternate and compressive fatigue depicted peculiar features. Less extended damage and better fatigue resistance were observed for the laminate with symmetrically distributed layers

Sistema de supervisión para el monitoreo de redes eléctricas inteligentes

In the present work a computer application is made responsible for supervising the monitoring of an intelligent network in the conditions of a less developed infrastructure and through the use of free software. Currently with incorporation of renewable sources of energy, new systems of tariffs, services and the Internet of Things; Electrical power systems have also evolved towards the smart grid. These require a communications infrastructure and Internet access that is sometimes not available, so the platform developed can cover these deficiencies and provide an environment for growth and technological independence. The system is implemented using the Python programming language and a SQLite database. The communication network for the measurement nodes is deployed using the ZigBee protocol, which is low consumption and fault-tolerant.En el presente trabajo se realiza una aplicación informática encargada de supervisar el monitoreo de una red inteligente en las condiciones de una infraestructura menos desarrollada y mediante el uso de software libre. Actualmente con la incorporación de fuentes renovables de energía, nuevos sistemas de tarifas, servicios y el Internet de las Cosas; los sistemas eléctricos de potencia también han evolucionado hacia la red inteligente. Estos sistemas requieren de una infraestructura de comunicaciones y acceso a Internet que en ocasiones no está disponible, por lo cual la plataforma desarrollada puede dar cobertura a estas deficiencias y brindar un entorno para el crecimiento y la independencia tecnológica. El sistema es implementado usando el lenguaje de programación Python y una base de datos SQLite. La red de comunicaciones para los nodos de medición es desplegada mediante el protocolo ZigBee, de bajo consumo y tolerante a fallos

Procede de telemesure : applications aux capteurs de micro-deplacements et de micro-deformations utilises dans les secteurs industriels et en genie biomedical

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc