Demandas-control y salud: El rol mediador del tiempo libre

Esta investigación explora el papel mediador que tiene la utilización del tiempo libre en la relación existente entre las altas demandas mentales y el escaso control en el trabajo y las respuestas de engagement, burnout y sintomatología percibida. Participantes: 9.090 trabajadores y trabajadoras de 13 empresas colombianas. Metodología: verificación por medio de análisis de ecuaciones estructurales siguiendo los pasos propuestos por Baron y Kenny (2014). Resultados: disponer de tiempo libre y poderlo emplear en actividades de recuperación reduce el efecto desfavorable de las altas demandas y un bajo control en el trabajo, promoviendo mayores niveles de engagement y una menor presentación de sintomatología general de enfermedad, y del cinismo y agotamiento emocional relacionados con el burnoutThis research explores the mediating role of the use of free time in the relationship between high mental demands and t low control at work and the responses of engagement, burnout and perceived symptoms. Participants: 9,090 workers from 13 Colombian companies. Methodology: verification through structural equation analysis following the steps proposed by Baron and Kenny (2014). Results: having free time and being able to use it in recovery activities reduces the adverse effect of high demands and low control at work, promoting higher levels of engagement, lower appearance of illness symptoms, cynicism and emotional exhaustion related to the burnout

Influencia del tiempo de gelificación sobre las propiedades estructurales, vibracionales y eléctricas del compósito PEG0.2/V2O5

Se estudiaron las propiedades estructurales, vibracionales y eléctricas de películas V2O5·nH2O y PEG0.2/V2O5 en función del tiempo de gelificación. Las películas fueron sinterizadas por sol-gel mediante la ruta del pentóxido de vanadio sobre sustratos de vidrio previamente tratados. La caracterización se llevo a cabo mediante Difracción de Rayos-X, Espectroscopía Raman y el método de las cuatro puntas convencional de van der Pauw. Los resultados indican que el aumento en el tiempo de gelificación del sol precursor (V2O5.nH2O) incrementa la calidad cristalina, el grado de hidratación, y la concentración de iones V5+ en las películas. En el compósito híbrido (PEG0.2/V2O5) los iones VO2+ actúan como enlazantes entre las cadenas poliméricas haciéndolas más compactas, lo cual facilita la movilidad de los portadores de carga eléctrica entre los iones vanadios. Los resultados mostraron una transición de fase semiconductormetal alrededor de 34°C, una transición óptica del tipo indirecta (para V2O5·nH2O) y una transición vítrea alrededor de Tg=-69°C.Structural, vibrational and electrical properties of V2O5·nH2O and PEG0.2/V2O5 films as a function of gelation time were studied. The films were sintered by sol-gel using vanadium pentoxide route on glass substrates previously treated. Films were characterized by X-Ray Diffraction, Raman Spectroscopy and the four-point van der Pauw conventional method. The results indicated that when the gelation time of the precursor (V2O5·nH2O) is increased, the crystalline quality, the degree of hydration, and V5+ ion concentration are increased. In the hybrid composite (PEG0.2/V2O5), VO2+ ions act as bonding between the polymer chains, making them more compact to facilitate the mobility of electric charge carriers between vanadium ions. The results showed a semiconductor-metal transition about 34°C, an indirect optical transition (V2O5·nH2O) and a vitreous transition around Tg=-69°C.Fil: Londoño Calderon, Cesar Leandro. Universidad Nacional de Colombia; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jurado, J. F.. Universidad Nacional de Colombia; ColombiaFil: Vargas Hernández, C.. Universidad Nacional de Colombia; Colombi

Adoquines en concreto: propiedades físico-mecánicas y sus correlaciones

Este artículo presenta los resultados de los ensayos de diferentes propiedades físico-mecánicas realizados sobre una muestra de adoquines producidos en Colombia, que constituye la base experimental para la actualización de la norma NTC 2017 "Adoquines de concreto para pavimentos" del ICONTEC. Un total de 40 muestras, provenientes de 10 productores colombianos diferentes, fueron ensayadas en desarrollo del proyecto de investigación "Nuevo método para determinar la resistencia al desgaste de pisos", realizada en convenio entre el grupo de investigación en Materiales y Tecnologías de la Construcción -MYTEC del Instituto Tecnológico Metropolitano, el Instituto de Productores de Cemento (ICPC) y la empresa productora de prefabricados INDURAL S.A.Se determinaron las variables físico-mecánicas de las muestras con base en diferentes normas, se discuten y recomiendan las variables a ser controladas en la norma de calidad de producto en Colombia. Se reporta el valor para la resistencia a la abrasión a ser incluido en la norma de producto, y de forma adicional, se presenta la densidad de acabado de pisos en adoquines para efecto del cálculo de cargas muertas de diseño en estructuras (puentes y edificaciones). This papcr shows the testing results for different physical properties ofpaving blocks. The test were driven over 40 samples from 10 different producers in Colombia, in order to build up experimental data base towards an actualization of NTC 2017 "Concrete paving blocks", published by the Instituto Colombiano de Normas Tecnicas -(ICONTEC). This paper is derived from de research program "New Test Method for Determining Abrasion Resistance in Floor Materials", developed at Instituto Tecnológico Metroplitano ITM at Medellín (Colombia), under agreement with Instituto Colombiano de Productores de Cemento (ICPC) and INDURAL S.A.Physical-Mechanical properties for paving-blocks to be specified in Colombian standards are examined, and the upper value for abrasion resistance were determined. It is also introduced the density of concrete block paving as load for structural design

Retention of zinc in biofortified rice and maize during processing and cooking

Biofortification is considered a complementary strategy to reduce micronutrient deficiencies in low- and middle -income countries. Rice and maize are two sta¬ble crops commonly consumed in Latin America where zinc deficiency is com¬mon and biofortified rice and maize could potentially assist in reducing these deficiencies. Improved biofortified varieties contain higher levels of zinc, but not much is known about the effect on zinc retention or on phytate reduction when using these crops in common recipes. Also the biofortified maize contains a bet¬ter protein profile with higher concentrations of tryptophan and lysine, which could be influenced during processing

Experimental workshop in unconventional structures: deployable & tree-like structures SMiA -training and research at Barcelona Tech

The purpose of this paper is to share the experience, training and teaching students in non conventional structures area. The research group SMiA Structural Morphology in Architecture performed a practical and theoretical workshop designed to learn unconventional structures in architecture. The main objective was to propose a practical teaching method, the students gain the necessary tools to design lightweight and membrane structures developing an architectural project. Physical and digital tools are utilized, including WinTess3, Sketch Up, Grasshopper, a parametric-geometry-development-and-testing software.Lightweight Construction Course is an elective architecture program at ETSAV School of Architecture of "El Vallès", leading by Professor Dr.-Arch. Ramon Sastre. The main topics that were developed are: Deployable, Tree-Like, Reciprocal Frame, and Tensegrity Structures. In the present article we explain the practical experience in Deployable and Tree-like Structures. The course was offered to students in the last year of career at UPC, international students (Erasmus) and Master students.Peer ReviewedPostprint (published version

Application of the sine-cosine algorithm to the optimal design of a closed coil helical spring

This paper proposes the application of the sinecosine algorithm (SCA) to the optimal design of a closed coil helical spring. The optimization problem addressed corresponds to the minimization of total spring volume subject to physical constraints that represents the closed coil helical spring such as maximum working load, shear stress, and minimum diameter requirements, among other. The resulting mathematical formulation is a complex nonlinear and non-convex optimization model that is typically addressed in literature with trial and error methods or heuristic algorithms. To solve this problem efficiently, the SCA is proposed in this research. This optimization algorithm belongs to the family of the metaheuristic optimization techniques, it works with controlled random processes guided by sine and cosine trigonometric functions, that allows exploring and exploiting the solution space in order to find the best solution to the optimization problem. By presenting as main advantage an easy implementation at any programming language using sequential quadratic programming; eliminating the need to uses specialized and costly software. Numerical results demonstrating that the proposes SCA allows reaching lower spring volume values in comparison with literature approaches, such as genetic algorithms, particle swarm optimization methods, among others. All the numerical simulations have been implemented in the MATLAB software

Grupo Empresarial Antioqueño. Evolución de políticas y estrategias, 1978-2002

El foco de los temas tratados se centra en la identificación de las políticas y estrategias corporativas del GEA desde su gestación en 1978 hasta 2002. Una forma simple de acercarse al contenido del trabajo es mediante algunas preguntas tales como: ¿Cuáles han sido las principales políticas y estrategias corporativas desde sus inicios? ¿Existen realmente políticas y estrategias comunes? ¿Han existido siempre? ¿Están escritas o han sido tácitas? ¿Existe alguna política general sobre el manejo de las políticas y estrategias? ¿Qué impacto ha tenido la apertura económica en las políticas y estrategias? ¿Hay políticas especiales respecto a los sectores dentro de los cuales opera el GEA, por ejemplo, sólo estar en aquellos sectores en los que pueda ser líder? ¿Es conveniente conservar las políticas hacia el futuro?The main point of the topics exposed is focused on the identification of the corporative policies and strategies of the GEA, since it was founded in 1978 until 2002. A simple way to look at the content of this document is by the use of questions such as: Which have the main corporative policies and strategies been since GEA s foundation? Are there indeed common policies and strategies? Have they always existed? Are they written, or are they understood beforehand? Is there a general policy concerning the management of policies and strategies? What impact has the economic opening had in the policies and strategies? Are there special policies concerning the sectors in which GEA can act as a leader institution? Is it convenient to keep the policies in the future