5257 research outputs found
Sort by
Intermetallic-Rich Layer Formation for Improving Corrosion Resistance of Magnesium Alloys
No full textAbstract: The present work examines the formation of a corrosion protective coating containing intermetallic phases on magnesium alloy substrates. The protective coating was formed on the surfaces of commercially pure magnesium (cp Mg) and AZ31B magnesium alloy by vacuum thermal evaporation of commercially pure aluminium (cp Al) and a subsequent heat treatment of the sample. This coating was continuous, homogenous and its microstructure was a eutectic phase composed by clusters of α-Mg surrounded by β phase (Mg17Al12). This eutectic-type coating provided 168 and 504 h of protection inside the salt spray chamber for the cp Mg and AZ31 alloy samples, respectively. To achieve this, it was required to deposit at least 5.5 µm of cp Al and then perform a combined thermal treatment involving heating the samples to 583 K for 60 min and then raising the temperature to 693 K for 5 min. Graphic Abstract: [Figure not available: see fulltext.] © 2021, The Korean Institute of Metals and Materials
Value chain and economic development: The case of the Colombian coffee industry
No full textDependency on natural resources has made economies unstable because of the fluctuation of commodity prices. However, coffee production has not had this effect on the Colombian economy owing to the process of upgrading the value chain, with the Colombian National Federation of Coffee Growers taking the lead. Using a case study methodology, the present article aims to analyse how the process of upgrading the value chain in the Colombian coffee industry has contributed to the economic development of the country, represented as an improvement of the country's infrastructure and living conditions, economic growth, industrialisation level and education access perspectives. © 2020 Ana-Maria Parente-Laverde. Published by Vilnius University Press
Photocatalytic inactivation of Enterobacter cloacae and Escherichia coli using titanium dioxide supported on two substrates
No full textThe antibacterial photocatalytic activity of TiO2 supported over two types of substrates, borosilicate glass tubes (TiO2/SiO2-borosilicate glass tubes (BGT)) and low-density polyethylene pellets (TiO2-LDPE pellets), which were placed in a compound parabolic collectors (CPC) reactor, was evaluated against Enterobacter cloacae and Escherichia coli under sunlight. Three solar photocatalytic systems were assessed, suspended TiO2, TiO2/SiO2-BGT and TiO2-LDPE pellets, at three initial bacterial concentrations, 1 × 105; 1 × 103; 1 × 101 CFU/mL of E. coli and total bacteria (E. cloacae and E. coli). The solar photo-inactivation of E. coli was achieved after two hours with 7.2 kJ/L of UV-A, while total bacteria required four hours and 16.5 kJ/L of UV-A. Inactivation order of E. coli was determined, as follows, suspended TiO2/sunlight (50 mg/L) > TiO2-LDPE pellets/sunlight (52 mg/L) > TiO2/SiO2-BGT/sunlight (59 mg/L), the best E. coli. inactivation rate was obtained with TiO2-LDPE pellets/sunlight, within 4.5 kJ/L and 90 min. The highest total bacteria inactivation rate was found for TiO2/sunlight (50 mg/L) and TiO2-LDPE pellets/sunlight (52 mg/L), within 11.2 kJ/L and 180 min. TiO2 deposited over LDPE pellets was the most effective material, which can be successfully used for water disinfection applications. Bacterial regrowth was assessed 24 h after all photocatalytic treatments, none of those microorganisms showed any recovery above the detection limit (2 CFU/mL). © 2018 by the authors
Formulations for joint order picking problems in low-level picker-to-part systems
No full textThis article introduces several mathematical formulations for the joint order picking problem (JOPP) in low-level picker-to-part warehousing systems. In order to represent real warehousing environments, the proposed models minimize performance measures such as travel distance, travel time and tardiness, considering multi-block warehouses, due dates, and multiple pickers. The number of constraints and decision variables required for each proposed model is calculated, demonstrating the complexity of solving medium and long-sized problems in reasonable computing time using exact methods, so it is still recommendable to solve these JOPP using metaheuristics. The proposed models can be followed as a reference for new solution methods that yield efficient and fast solutions. © 2020, Institute of Advanced Engineering and Science. All rights reserved
Prediction of noise from wind turbines: A theoretical and experimental study [Predicción del ruido proveniente de los aerogeneradores: Estudio teórico y experimental]
No full textSeveral noise propagation models used to calculate the noise produced by wind turbines have been reported. However, these models do not accurately predict sound pressure levels. Most of them have been developed to estimate the noise produced by industries, in which wind speeds are less than 5 m/s, and conditions favor its spread. To date, very few models can be applied to evaluate the propagation of sound from wind turbines and most of these yield inaccurate results. This study presents a comparison between noise levels that were estimated using the prediction method established in ISO 9613 Part 2 and measured levels of noise from wind turbines that are part of a wind farm currently in operation. Differences of up to 56.5 dBZ, with a median of 29.6 dBZ, were found between the estimated sound pressure levels and measured levels. The residual sound pressure levels given by standard ISO 9613 Part 2 for the wind turbines is larger for high frequencies than those for low frequencies. When the wide band equivalent continuous sound pressure level is expressed in dBA, the residual varies between -4.4 dBA and 37.7 dBA, with a median of 20.5 dBA. © 2018 Universidad de Antioquia.Hay muchos modelos de propagación de ruido que se utilizan para calcular el ruido proveniente de los aerogeneradores. Sin embargo, fallan en la precisión con que pueden predecir los niveles de presión sonora. La mayoría de estos modelos han sido desarrollados para estimar el ruido proveniente de las industrias, con velocidades del viento inferiores a 5 m/s y condiciones favorables a su propagación. Hasta ahora hay muy pocos modelos que se puedan aplicar para la propagación del sonido proveniente de los aerogeneradores y la mayoría de ellos arrojan resultados poco precisos. En este artículo se presenta una comparación entre los niveles de ruido estimados a través del método de predicción establecido en la norma ISO 9613 Parte 2 y los niveles de ruido medidos proveniente de los aerogeneradores instalados en un parque eólico en funcionamiento. Se encontraron diferencias entre los niveles de presión sonora estimados y medidos de hasta 56.5 dBZ, con una mediana de 29.6 dBZ. El nivel de presión sonora residual arrojado por la norma ISO 9613 Parte 2 para los aerogeneradores es mayor para las frecuencias altas que para las frecuencias bajas. © 2018 Universidad de Antioquia
Strategies of the Mexican State to Underestimate Femicides [Estrategias del Estado mexicano para minimizar los feminicidios]
No full textThis article analyses the connections between the militarization processes in Ciudad Juarez (Mexico), from 2008 to 2015, and women's disappearances and femicides. This work provides updated data and analysis on this phenomenon, and aims to demonstrate the existence of strategies by the authorities to underestimate the facts and blame them on the victims. Our analysis relies on seminal works on gender studies, and is supported by documentary work with official data from Ciudad Juarez's Prosecutor Office, as well as on reports from non-governmental organizations. We used a methodology of qualitative approach where ethnography prevailed, conducting participant observation, as well as personal interviews. © 2019, Universidade Federal de Santa Catarina
Impacto de las tecnologías de información y comunicación en el desempeño de la negociación internacional
No full text[No abstract available
In-silico study of the ionic current gradients determining left-to-right atrial frequencies during paroxysmal atrial fibrillation
No full textAtrial fibrillation is the most prevalent cardiac arrhythmia. Paroxysmal atrial fibrillation (pAF) may occur in episodes lasting from minutes to days. Recent studies suggest that some pAF episodes present a left-to-right dominant frequency gradient caused by ionic current gradients. However, how each ionic current gradient affects the left-to-right dominant frequency gradient during pAF has not been studied. In this work, we use a 3D model of human atria to study how the ionic current gradients affect the dominant frequency gradient during pAF induced by continuous ectopic activity. The role of the specific gradients of acetylcholine-activated potassium current (I KACh ) and inward-rectifier potassium current (I K1 ) on determining the left-to-right dominant frequency gradient was assessed. The main outcome of this study is that either or both of the I KACh or I K1 gradients are necessary to induce a left-to-right dominant frequency gradient during pAF. However, both gradients are necessary to the left atrium maintaining, by itself, the pAF episode. These findings have potentially important implications for the development of atrial-selective therapeutic approaches. © The Author(s) 2019
Formulación del plan estratégico para la consecución de ventajas competitivas en la prestación del servicio : caso empresa del sector transporte público (Conducciones Palenque Robledal S.A.)
Get PDFEl trabajo de grado presenta de manera clara la forma como se da respuesta a la pregunta de investigación ¿Qué acciones implementar en la empresa para lograr una ventaja competitiva en la prestación del servicio?, para lo cual se parte de la elaboración de un diagnóstico, a través de un sondeo de 37 preguntas aplicado al 100% de los colaboradores, de manera adicional se utilizan diferentes herramientas para acercarse tanto a la realidad interna como externa de la organización objeto de estudio. La metodología utilizada es cualitativa mediante un estudio exploratorio y documental que lleva a la construcción de un plan estratégico a 5 años y la conclusión general que la empresa es colectiva, de corta distancia jerárquica, baja evasión a la incertidumbre, participativa y flexible.Magíster en Administración MBAMaestrí
Semiótica e história, fotografia e informação
Get PDF¿Estamos preparados para producir contenido de imágenes para la sociedad de la ecología de los nuevos medios? El debate es necesario, tanto por parte de la academia como del mercado. El escenario ofrece algunas transformaciones que no se comprenden. Ocurren de forma natural. Esto sugiere que comprendemos las ideas de Neil Postman y Marshall McLuhan al definir el concepto de ecología de medios como el estudio de los medios como entornos. La preocupación de ambos se produjo en un momento médicamente conflictivo, considerando el desarrollo de la televisión a fines de la década de 1960 y la transformación social posterior. Marshall McLuhan, al escribir el libro Understanding Media, ya expresó su preocupación por reinterpretar la sociedad mediática al declarar que los medios interactúan entre sí. La radio ha transformado la forma de las noticias tanto como ha alterado la imagen en el cine sonoro. La televisión ha provocado cambios drásticos en la programación de radio, etc.
Teniendo en cuenta estas inquietudes, organizamos el trabajo “Semiótica e historia, fotografía e información”, que aborda un debate sobre esta temática a partir de los conceptos de ecología de los medios. Este libro reúne los capítulos resultantes del I Congreso Internacional de Estudios de la Imagen y Ecología de los Medios, realizado por Ria Editorial y GENEM - Grupo de Estudio sobre la Nueva Ecología de los Medios. El congreso, realizado en modalidad 100% virtual, contó con el apoyo de DigiMedia - Centro de Investigación en Medios Digitales, Red INAV - Red Iberoamericana de Narrativas Audiovisuales y la Cátedra Latinoamericana de Narrativas Transmedia. Los textos están redactados en portugués o español, según el idioma de origen de los autores, o los países donde realizan sus investigaciones.http://wp.reno.com.br/index.php/semiotica-e-historia-fotografia-e-informacao