Influence of peak height prior to milling the resulting surface roughness of the ball burnishing process on convex and concave pieces of aluminum

Molds, counterfoils of conformation, and many other industrial pieces with important presentations, face constant the engineers with the problem of obtaining superficial qualities that minimize the friction, optimize the adjustments, or improve the superficial hardness. Among the many procedures to improve surface finish, highlights the ball burnishing, which have been obtained roughness values recommended in diverse applications. The ball burnishing process is a technological operation which is plastically deformed surface irregularities to improve the surface finish, by the action of the force exerted by a cylinder or ball. This process can be used on cylindrical surfaces, flat front, so, conical, with changes in section and radios, etc., which have been previously machined. The ball burnishing process in question is performed after a machining operation, and the results have influence on it. An important parameter to control is the height of the ridge that remains after the machining, because burnishing process will be able to reduce it in a certain percentage. This study is aimed to conduct an analysis of the influence of peak height prior to milling the resulting surface roughness of the ball burnishing process with concave and convex parts of two different types of aluminum (A92017 & A96351). The milling is done with a ball mill of ϕ8mm, rotating at a cutting speed of 3000min-1, with a cutting depth of 1 mm and three values of progress for three different conditions that leave a ridge height: 0.02 mm, 0.06 mm and 0.10 mm. The main contribution of this study is the recommendations on strategies for burnish these pieces, and measuring the roughness.The work is based on experimental data where through DOE techniques are carried out different experiments in which the surface roughness is measured in directions parallel and perpendicular to the previous milling for various conditions. We compare the results and an analysis of how this affects the height of the ridge left by the previous machining on roughness values obtained. Finally, it has been concluded that the burnish process improvement between 33 and 71% surface roughness of the pieces.Postprint (published version

Psoriasis: aspectos comparativos entre la edad pediátrica y adulta de interés para el médico general

Introducao: La psoriasis es una enfermedad sistémica con alto impacto en la calidad de vida, afecta 1 a 2% de la población general y puede iniciarse en el lactante o debutar en la infancia, adolescencia o adultez. Dependiendo de la edad, las características clínicas varían y, por tanto, el tratamiento es diferente. Objetivo: Transmitir al médico general aspectos comparativos útiles para su práctica diaria, que le permitan un abordaje inicial y un manejo interdisciplinario de la psoriasis. Resultados: El 27% de los casos se manifiesta antes de los 15 años con placas delgadas o gotas, con localización retroauricular, facial, umbilical o en el área del pañal, lo que puede retrasar el diagnóstico. Dependiendo de la edad, localización y extensión de las lesiones, los tratamientos tópicos y la fototerapia UVB nb son de elección en las formas leves a moderadas en los niños y adultos, por ser seguros y efectivos, los sistémicos y biológicos se reservan para formas severas, artropáticas, por el potencial riesgo de efectos adversos. Conclusao: Tanto el manejo inicial para mejorar la barrera de la piel como los tratamientos tópicos pueden ser realizados por el médico generalista, de forma interdisciplinaria. Para casos con formas clínicas más complejas y comorbilidades, el manejo debe ser más intensivo. Las formas severas sub tratadas afectan la calidad de vida

Validación lingüística y psicométrica del cuestionario “The princess margaret hospital satisfaction with doctor questionnaire” en pacientes oncológicos

31 PáginasObjetivos: Realizar la validación Lingüística y Psicométrica del cuestionario “The Princess Margaret Hospital Satisfaction with Doctor Questionnaire” en Pacientes Oncológicos. Metodología: Estudio Prospectivo con un Diseño de Validación de Escalas. Población: Pacientes Oncológicos que asisten a consulta externa de las especialidades Oncológicas en la Fundación Cardio Infantil (en Bogotá) y el Hospital Pablo Tobón Uribe (en Medellín). Procedimiento: Validación Lingüística: Posterior a creación del comité de revisión, se realizara traducción y re-traducción por peritos bilingües, realizando homogeneización conceptual y semántica, el formato preliminar se avalara por prueba piloto donde se evaluaran particularidades y su comprensión para definir una versión definitiva. Validación Psicométrica: Se realizara validez de apariencia y de contenido por un grupo focal de expertos, y de constructo por análisis factorial. Se valorara su consistencia interna (alfa de Cronbach), y su validez convergente (Coeficiente de correlación de Spearman); se analizara su confiabilidad test – re test y la correlación inter evaluador (ambos con el Coeficiente de correlación de Spearman); por último, analizaremos la detección de cambios clínicos importantes (Test de U Mann Whitney). Utilidad: Se medirá según el tiempo medio utilizado para la aplicación de la escala, se describirán las necesidades particulares para su ejecución, y el grado necesario de capacitación; al final: se describirá la forma, método y tiempo para la generación de la calificación final

Analysis of harmonic distortion generated by PWM motor drives

This paper evaluates the harmonic distortion generated by PWM motor drives in an electrical industrial system of a wheat flour mill company. For this, a comparative study between two industrial circuits connected at the same point of common coupling with similar characteristics of load and transformers is presented. The difference is that one circuit has PWM motor drives and the other does not have them. In the study, a practical method based on the statistical characterization of the total harmonic distortion of voltage (THDV) and current (THDI), individual voltage distortion (IVD), individual current distortion (ICD) and K-Factor is applied. As result, it was observed that PWM motor drives generated harmonics voltage mainly of fifth and seventh order with values that exceed limits established by standards in both circuits. In the work is also demonstrated that in the analysis of harmonics is necessary to consider various parameters and not only one

Calculation model and methodology for stiffness evaluation in hydraulics cylinders

In the paper an analysis scheme able to considerate of all the main geometric and load factors that affect the behavior of a hydraulic cylinder in its action as a flexural-compression member. Also, experimental validations of the model are shown too. A methodology to identify the conditions leading to the instability of the cylinder is established

Calculation model and methodology for stiffness evaluation in hydraulics cylinders

In the paper an analysis scheme able to considerate of all the main geometric and load factors that affect the behavior of a hydraulic cylinder in its action as a flexural-compression member. Also, experimental validations of the model are shown too. A methodology to identify the conditions leading to the instability of the cylinder is established

Characterization of ball-burnishing vibration-assisted process

Este trabajo está dirigido al estudio del proceso de bruñido con bola asistido por una vibración. Se parte de considerar que dicha vibración ayudará al proceso, facilitando la deformación que se produce sobre la superficie de trabajo. Dado que no existe una herramienta similar en el mercado, con el fin de realizar el estudio, ha sido necesario diseñar, caracterizar y fabricar una herramienta capaz de realizar el proceso de bruñido con bola asistido, teniendo en cuenta los componentes fundamentales que intervienen en dicho diseño y el modelo físico que caracteriza la operación. Bajo estos criterios, la caracterización de la operación de la herramienta también se realiza mediante la evaluación de la rugosidad de la superficie que queda después de que ocurre el proceso. Para la validación experimental se han utilizado piezas de trabajo de aluminio y de acero. Estos resultados se compararon con los obtenidos por la misma herramienta sin utilizar vibraciones. Los resultados de rugosidad que resultan del bruñido con bola asistido, mejoran con respecto a los obtenidos utilizando el proceso sin asistencia, en ambos materiales ensayados.First of all, this work refers to the study of the ball-burnishing process assisted by a vibration. It starts by considering that this vibration helps to make the development of this finishing process easier, because it helps to deform the workpiece material more easily. Since there is no similar tool on the market, in order to conduct the study, it has been necessary to design, characterize and manufacture a tool that can perform the process, taking into account the critical components that are involved in the design, and the physical model characterizing the operation. Under these criteria, the characterization of the tool operation is also done by evaluating the surface roughness that remains after the process occurs. For experimental validation have been used workpieces of aluminium and steel. These results are compared to those obtained by the same tool without using vibration. Roughness results obtained using the ball-burnishing vibration-assisted process improves with respect to those obtained using the process without assistance, in both materials tested.Peer Reviewe

Aspectos estructurales de bosque de cativo en la región del bajo atrato, colombia

El planteamiento de sistemas de manejo de los bosques tropicales, requiere del conocimiento tanto de la estructura actual, como de la estimación racional de la respuesta probable del sistema a prácticas culturales que la modifiquen. En este trabajo se hace un análisis de algunos de los parámetros estructurales más relevantes de una asociación vegetal conocida en Colombia con el nombre de catival. Los aspectos que se analizan tienen que ver tanto con características estáticas como dinámicas de dos tipos de bosques sujetos a diferentes grados de inundación. Los resultados muestran que las agrupaciones presentan diferencias sustanciales tanto en términos de la estructura de diámetros y de la diversidad florística como en el grado de importancia y en el patrón de distribución espacial de la especie predominante (PrioriacopaiferaG.) Además, las tasas de crecimiento difieren significativamente entre las dos comunidades siendo aproximadamente tre veces superior en el catival A2, que en el catival A1. El estudio además de proporcionar información que permite alimentar planteamientos para el manejo de los cativales, describe las aplicaciones de metodologías para su evaluación y análisis

Fat-free/lean body mass in children with insulin resistance or metabolic syndrome: a systematic review and meta-analysis

Background: Lean / Fat Free Body Mass (LBM) is metabolically involved in active processes such as resting energy expenditure, glucose uptake, and myokine secretion. Nonetheless, its association with insulin sensitivity / resistance / glucose tolerance and metabolic syndrome remains unclear in childhood. Methods: The current investigation aimed to examine the differences in fat-free mass /lean body mass according to the presence of insulin sensitivity/insulin resistance/glucose tolerance/metabolic syndrome in children. A systematic search was carried out in Medline/PubMed, Embase, Scopus, Web of Science, and SciELO, covering the period from each database''s respective start to 21 June 2021. Two researchers evaluated 7111 studies according to the inclusion criteria: original human studies, written in English or Spanish, evaluating fat-free mass/lean body mass in children and adolescents including both with and without insulin sensitivity/insulin resistance /glucose tolerance and metabolic syndrome and reported the differences between them in terms of fat free mass/lean body mass. The results of the studies were combined with insulin sensitivity, insulin, resistance, glucose tolerance and metabolic syndrome. The standardized mean difference (SMD) in each study was calculated and combined using the random-effects model. Heterogeneity between studies was tested using the index of heterogeneity (I-2), leave-one-out sensitivity analyses were performed, and publication bias was assessed using the Egger and Begg tests. Results: Finally, 15 studies which compared groups defined according to different glucose homeostasis criteria or metabolic syndrome out of 103 eligible studies were included in this systematic review and 12 studies in the meta-analysis. Meta-analysis showed lower fat-free mass/lean body mass percentage in participants with insulin resistance/glucose tolerance/metabolic syndrome (SMD -0.47; 95% CI, - 0.62 to - 0.32) while in mass units (kg), higher values were found in the same group (SMD, 1.01; 95% CI, 0.43 to 1.60). Conclusions: Our results identified lower values of fat-free mass/lean body mass (%) in children and adolescents with insulin resistance/glucose tolerance/metabolic syndrome and higher values of fat-free mass/lean body mass when these are expressed in kg. The evidence of the impact of lean mass on children''s glucose homeostasis or metabolic syndrome is limited, so future studies research should focus on explaining the effect of fat-free mass/lean body mass on different metabolic outcomes. Moreover, it may be interesting to evaluate the quality (muscle density) or functional (muscle strength) outcomes in addition to both absolute (kg) and relative (%) values in future studies