Micromechanical behavior of thermal barrier coatings after isothermal oxidation

Thermal protection of metallic components by using ceramic coatings like thermal barrier coatings (TBCs) is widely used, in rocket engines, aircraft industry and gas turbines for power generation to reduce the substrate temperature up to 165°C. This technology diminishes the heat transfer in combustor, initial rotor blades and nozzles guide vanes, so that turbines have taken special advantage of these coatings to meet increasing demands for greater fuel efficiency, lower NOx emissions and higher power and thrust [1]. Thermal barrier coatings, apart from thermal protection are also used to protect against abrasion, oxidation and corrosion [2]. The understanding of the mechanical behavior of TBCs in both as-sprayed and thermal loading conditions is of great importance for the evaluation of components life. However, it is challenging to determine the true mechanical behavior because of the substantial differences, between each layer (TC, BC, and substrate), since the difficulty to prepare the sample´s surface and its high contents of pores, cracks and defects. This work reports on the mechanical characterization of APS 6-8 wt.% yttria stabilized zirconia (YSZ) as top layer bonded by an HVOF NiCoCrAlY layer to a superalloy substrate (Inconel 625) using the micro- and nano-indentation techniques on test specimens after being subjected to isothermal-oxidation at 1100°C and different time exposition (0, 200, 400, 600, 800, 1000, and 1700 hours). Observations under optical and SEM microscopy were performed in order to study the variation of the mechanical properties such as hardness, young’s modulus, and fracture toughness within the ceramic top layer after isothermal oxidation. The hardness and Young’s modulus of the ceramic layer showed an increase until 600h exposition which can be explained by sintering phenomenon. From 600h up to 1700h the Young’s showed a stabilization due to the equilibrium of sintering and phase transformation mechanisms, but hardness continued its increasing rate. The fracture toughness of the ceramic coating showed a softening condition of about 23% during the whole range of time for isothermal oxidation as a consequence of the detriment of the ceramic layer. Results show that sintering phenomena, TGO growth and phase transformation give a complex state of stresses of the coating system which will have great influence on its performance during regime operation. It is concluded damage of the coating is proportional to the extent of time exposition

Plan de mejoramiento financiero de la empresa Alejandro Toro Ingeniería Estratégica

El presente artículo presenta las ideas y métodos para realizar evaluación financiera utilizando diferentes tipos de indicadores, además llena de conocimiento al lector para descubrir el significado e importancia que tiene la evaluación financiera en las empresas. El presente texto alimenta el conocimiento en cuanto al funcionamiento, método, aplicación y evaluación de los indicadores financieros con los que se puede tomar decisiones en materia financiera trascendentales para el futuro del empresario y la empresa en general. La lectura establece y destaca la diferencia, ventajas y desventajas de los indicadores privados que se relacionan entre sí para determinar si el proyecto tiene o no prosperidad en el futuro, además de ayudar al gerente con el conocimiento de generación de valor de la empresa y sus proyecciones y de esta manera poder determinar la viabilidad del proyecto y su rentabilidad esperada o expresar los resultados en las decisiones a tomar para generar valor, flujo de caja, rentabilidad tomando decisiones en el corto, mediano y largo plazo, esto con el fin de generar números positivos en los saldos de la compañía. En términos generales los fracasos en los proyectos se deben básicamente a la falta de estudios previos antes de iniciar mi proyecto, en este caso específico se refleja que tan importante es la relación que tiene la evaluación financiera con el desarrollo del proyecto en general, por lo cual la empresa o el empresario pueden perder los recursos que invertirán, ya que con unas bases sólidas de estudios previos el empresario podrá determinar el futuro de la compañía.Universidad Libre Seccional Pereira -- Facultad de Ciencias Económicas, Administrativas y Contables -- Especialización en Alta GerenciaThis article presents the ideas and methods of conducting financial evaluation using different types of financial evaluation indicators, also fills the reader with knowledge to discover the meaning and importance of financial evaluation in companies, This text feeds the knowledge regarding the operation, method, application and evaluation of financial indicators with which transcendental financial decisions can be made for the future of the entrepreneur and the company in general. The reading establishes and highlights the difference, advantages and disadvantages of the private indicators that are related to each other to determine whether or not the project has prosperity in the future, in addition to helping the manager with the knowledge of the generation of value of the company and its projections and thus be able to determine the viability of the project and its expected profitability or express the results in the decisions to be made to generate value, cash flow, profitability, making decisions in the short, medium and long term, this in order to generate positive numbers in company balances. In general terms, the failures in the projects are basically due to the lack of previous studies before starting my project, in this specific case it is reflected how important is the relationship that the financial evaluation has with the development of the project in general, so which the company or the entrepreneur may lose the resources they will invest, since with a solid foundation of previous studies the entrepreneur will be able to determine the future of the company

Aplicación de un esquema 2-D en la solución de ondas de marea

Se presenta un esquema numérico basado en el método de las diferencias finitas que permite construir una solución aproximada de las ecuaciones de aguas pandas en su presentación bidimensional completa, e.d. considera en particular las aceleraciones de tipo convectivo en la conservación del momentum lineal. Para la validación del modelo se presenta una comparación de los campos de niveles obtenidos por el esquema numérico con soluciones analíticas linealizadas válidas en dominios de cálculo rectangulare

Análisis computacional integrado de fotoelasticidad digital y análisis termoelástico de esfuerzos

Stress measurement is useful to identify the operating conditions that can produce the failure of a structure. Among the strategies for stress measurement, the integration between digital photoelasticity and thermoelastic stress analysis has been extensively explored, because it is useful to determine the individual stresses, and because of its full-field capabilities. However, due to the experimental complexity of both techniques, their integration is often limited to semi-static cases, where the calibration of the thermal parameters is usually done independently of the photoelasticity experiment. This paper describes a computational integration of digital photoelasticity and thermoelastic stress analysis. The main contribution of the paper is to show that, under controlled conditions, the application of variable load can be used to determine the stress and temperature fields of a birefringent model. The results achieved of this paper could be useful in industrial environments, where the complexity of the experiments limits the range of applications that require stress field analysis.La medición de los esfuerzos mecánicos es importante en múltiples aplicaciones de ingeniería, porque permite identificar las condiciones de operación que hacen que las piezas fallen. Dentro de las estrategias para medir esfuerzos mecánicos, la integración de la fotoelasticidad digital y el análisis termoelástico de esfuerzos ha sido ampliamente explorada, porque permite obtener información de esfuerzos individuales y no solo de su suma o diferencia; y porque permite análisis no invasivos y de campo completo. Sin embargo, dada la complejidad experimental de ambas técnicas, su integración suele limitarse a casos semi-estáticos, donde la calibración de los parámetros térmicos se suele hacer independientemente al montaje de fotoelasticidad. Este trabajo explora una integración computacional de la fotoelasticidad digital y el análisis termográfico de esfuerzos, mediante la aplicación de carga variable a un modelo birrefringente. Los resultados obtenidos indican que, bajo condiciones controladas, es posible obtener simultáneamente los campos de esfuerzos y de temperaturas del modelo inspeccionado. Estos resultados podrían ser de útiles entornos industriales, donde la complejidad de los experimentos limita el rango de aplicaciones que requieren análisis de campos de esfuerzos

Resistencia al desgaste de cuchillas de arados rotativos en operación en suelos tropicales

Se estudió la resistencia al desgaste de cuchillas de tres tipos de arados rotativos (grada rotativa, rotavator y motazada) en suelos tropicales del municipio de Santa Fe de Antioquia. También se realizaron ensayos de resistencia al desgaste en condiciones de laboratorio (norma ASTM G65). El desgaste más significativo en ensayos de campo lo presentaron las cuchillas tipo grada rotativa y rotavator. Se determinó que la frecuencia rotativa de operación y las fuerzas súbitas de impacto herramienta – suelo son los factores que más inciden. En los ensayos de laboratorio, no se presentaron diferencias significativas en el desgaste de las herramienta

Factors associated with post-traumatic stress disorder symptoms in the post-quarantine context of the COVID-19 pandemic in Peruvian medical students

Background: In March 2020, the Peruvian state introduced quarantine as a measure to control the spread of SARS-CoV-2. It has been suggested that being in quarantine is associated with the development of symptoms of Post-traumatic Stress Disorder (PTSD). The present study aims to explore the factors associated with the development of PTSD in a post-quarantine context due to COVID-19 in medical students. Objectives: To evaluate the factors associated with the development of post-quarantine PTSD symptoms in medical students from a Peruvian university. Methods: Analytical cross-sectional study. The objective will be developed after the lifting of the quarantine in Peru. Medical students enrolled during the 2020-01 academic cycle of the Peruvian University of Applied Sciences will be included. To collect the outcome variable (PTSD), the Impact of Event Scale - Revised (IES-R) will be used. The associated factors will be collected through a form that will be validated by experts and piloted in the field. The crude and adjusted coefficients will be calculated, using bivariate and multivariate linear regression models, respectively. We will use the “manual forward selection” technique to obtain a final model with minimally sufficient fit. After each model comparison and decision, multicollinearity will be evaluated with the variance inflation factor and matrix of independent variables. Results: Not having health insurance, having relatives or close friends who contracted the disease and having a lower family income are factors associated with PTSD in the post-quarantine context of the COVID-19 pandemic in medical students at a Peruvian university. Conclusions: Clinical evaluation is important for medical students with a high probability of having PTSD symptoms. We recommend conducting a longitudinal study to identify causality and other unstudied factors related to PTSD.Revisión por pare

Enseñanza de idiomas en escuelas de medicina humana de Perú

Introducción. Las escuelas de medicina en Latinoamérica deberían asegurar que sus egresados conozcan ciertos idiomas además del español. Sin embargo, poco se ha descrito sobre el tema en Perú.Objetivo. Describir las características de la enseñanza de otros idiomas en escuelas de medicina humana de Perú.Materiales y métodos. Estudio transversal analítico realizado durante agosto de 2015 en escuelas de medicina humana de Perú. Se contactaron al menos dos estudiantes de cada escuela, quienes recolectaron las variables de interés. Después, se compararon los datos recolectados y se analizaron con el programa STATA v13.Resultados. Se obtuvieron datos de 36 escuelas de medicina. Todas contaban con al menos un curso de inglés, obligatorio en 25 escuelas. 6 escuelas tenían un curso de quechua. Las escuelas con cursos obligatorios de inglés se ubicaban en su mayoría fuera de Lima y comenzaron a funcionar antes de 1999. Gran parte de las escuelas públicas tenían cursos de inglés obligatorios, sin seminarios, prácticas, ni talleres, los cuales no se pueden convalidar y son brindados por la misma institución.Conclusión. Se encontró que pocas escuelas tenían al menos un curso de quechua, aunque todas ofrecen cursos de inglés.Introduction: Medical schools in Latin America should ensure that their graduates know certain languages besides Spanish, however, little has been described on the subject in Peru.Objective: To describe the characteristics of second language teaching in medical schools of Peru.Materials and methods: Cross-sectional analytical study carried out in August 2015 in human medicine schools of Peru. At least two students from each school were contacted, and variables of interest were collected. Subsequently, the collected data were compared and analyzed using the STATA v13 program.Results: Data were obtained from 36 medical schools. All of them offered at least one English course —which was mandatory in 25 schools—, while 6 schools offered a Quechua course. The schools with compulsory English courses were located mostly outside Lima and began to operate before 1999. Many of the public schools offered compulsory English courses that include seminars, practices and workshops, which cannot be validated and are offered by the school.Conclusion: Few schools offered at least one Quechua course, although all of them offered English courses

Enseñanza de idiomas en escuelas de medicina humana de Perú

Introducción. Las escuelas de medicina en Latinoamérica deberían asegurar que sus egresados conozcan ciertos idiomas además del español. Sin embargo, poco se ha descrito sobre el tema en Perú.Objetivo. Describir las características de la enseñanza de otros idiomas en escuelas de medicina humana de Perú.Materiales y métodos. Estudio transversal analítico realizado durante agosto de 2015 en escuelas de medicina humana de Perú. Se contactaron al menos dos estudiantes de cada escuela, quienes recolectaron las variables de interés. Después, se compararon los datos recolectados y se analizaron con el programa STATA v13.Resultados. Se obtuvieron datos de 36 escuelas de medicina. Todas contaban con al menos un curso de inglés, obligatorio en 25 escuelas. 6 escuelas tenían un curso de quechua. Las escuelas con cursos obligatorios de inglés se ubicaban en su mayoría fuera de Lima y comenzaron a funcionar antes de 1999. Gran parte de las escuelas públicas tenían cursos de inglés obligatorios, sin seminarios, prácticas, ni talleres, los cuales no se pueden convalidar y son brindados por la misma institución.Conclusión. Se encontró que pocas escuelas tenían al menos un curso de quechua, aunque todas ofrecen cursos de inglés.Introduction: Medical schools in Latin America should ensure that their graduates know certain languages besides Spanish, however, little has been described on the subject in Peru.Objective: To describe the characteristics of second language teaching in medical schools of Peru.Materials and methods: Cross-sectional analytical study carried out in August 2015 in human medicine schools of Peru. At least two students from each school were contacted, and variables of interest were collected. Subsequently, the collected data were compared and analyzed using the STATA v13 program.Results: Data were obtained from 36 medical schools. All of them offered at least one English course —which was mandatory in 25 schools—, while 6 schools offered a Quechua course. The schools with compulsory English courses were located mostly outside Lima and began to operate before 1999. Many of the public schools offered compulsory English courses that include seminars, practices and workshops, which cannot be validated and are offered by the school.Conclusion: Few schools offered at least one Quechua course, although all of them offered English courses

Effect of dilute sulfuric acid pretreatment on the physicochemical properties and enzymatic hydrolysis of coffee cut-stems

Coffee-cut stems are a potential fermentable sugars source, which can be upgraded in different value-added products and energy vectors. Nevertheless, there are few reports focused on the acid pretreatment and saccharification processes. Thus, this paper evaluates the effect of the acid pretreatment and saccharification conditions of coffee cut-stems to find the highest sugar yield. Thereafter, the influence of the residence time in the acid pretreatment and the -glucosidase supplementation in the saccharification process were analyzed. The combined severity factor and crystallinity index were used as metrics to evaluate both processes. In all assays, an increase in the crystallinity index was observed. Furthermore, a nonlinear trend of the combined severity factor respect to the residence time in the acid pretreatment was evidenced. The highest sugar yield was 66.75% with a combined severity factor of 1.84. The better saccharification process was achieved at combined severity factor of 2.01 with a digestibility of 43%. The addition of -glucosidase in the enzymatic hydrolysis allows increasing the value to 69.07%. Hence, low temperatures, acid concentrations, and the -glucosidase supplementation allows obtaining a high sugar yield from coffee cut stems.The authors express their gratitude for the financial support to the Programme of ERASMUS + - International Credit Mobility celebrated between the Universidad Nacional de Colombia at Manizales and the University of Minho. The COLCIENCIAS program “Jóvenes Investigadores e Innovadores, Convocatoria 761 de 2016”, the international collaboration project COLCIENCIAS – CONICYT with code PCCI140052, HERMES code 23567 (23876) entitled “Análisis Tecno-económico y Ambiental de Biorefinerías a partir de Residuos Lignocelulósicos con Esquemas de Recirculación de Microorganismos”, the research program entitled “Reconstrucción del tejido social en zonas posconflicto en Colombia” SIGP code: 57579 with the project entitled “Competencias empresariales y de innovación para el desarrollo económico y la inclusión productiva de las regiones afectadas por el conflicto colombiano” SIGP code 58907. Contract number: FP44842-213-2018.info:eu-repo/semantics/publishedVersio