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Search Results: 1 - 10 of 495705 matches for " Elkin Alonso Cortés Marín "
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ESTUDIO PRELIMINAR DEL COMPORTAMIENTO REOLOGICO BAJO COMPRESIóN UNIDIRECCIONAL DE LA PULPA DE PLáTANO (Musa AAB Simmonds)
CIRO VELáSQUEZ,HéCTOR JOSé; MONROY LAITON,FABIAN ARMANDO; CORTéS MARíN,ELKIN ALONSO;
DYNA , 2008,
Abstract: samples of plantain pulp (musa aab simmonds) were subjected to tests of unidirectional compression using an analyzer of texture ta-xt2i. the true flow curves (stress-strain) and rheological properties such as stress, strain and toughness to failure point were evaluated. the material was subjected under two loading direction (longitudinal and transversal) and three positions throughout the longitudinal axis of the product: initial, middle and final. the statistical analyses showed that the product is highly anisotropic, where the direction of load and the position within the material are significant effects in the rheological response of the material.
ESTUDIO PRELIMINAR DEL COMPORTAMIENTO REOLOGICO BAJO COMPRESIóN UNIDIRECCIONAL DE LA PULPA DE PLáTANO (Musa AAB Simmonds)
HéCTOR JOSé CIRO VELáSQUEZ,FABIAN ARMANDO MONROY LAITON,ELKIN ALONSO CORTéS MARíN
DYNA , 2008,
Abstract: Pulpa de plátano Dominico-Hartón fue sometida a ensayos de compresión unidireccional usando un analizador de textura TA-XT2i. Las curvas de flujo y las propiedades reológicas del producto a condición de falla como esfuerzo, deformación y tenacidad fueron determinadas. La pulpa fue sometida a dos direcciones de carga (longitudinal y transversal) en tres posiciones a lo largo del eje longitudinal del producto: inicial, medio y final. Los análisis estadísticos mostraron que el material es altamente anisotrópico, donde la dirección de carga y la posición dentro de la material son efectos significativos en la respuesta reológica del producto.
CORRELACIóN ENTRE PROPIEDADES ANATóMICAS, RESISTENCIA A FLEXIóN ESTáTICA Y ENERGíA REQUERIDA PARA EL CORTE DE LA CA?A DE AZúCAR (Saccharum officinarum L.)
González Sánchez,Hugo Alberto; Toro Betancur,Alejandro; álvarez Mejía,Fernando; Cortés Marín,Elkin Alonso;
Revista Facultad Nacional de Agronomía, Medellín , 2008,
Abstract: the microstructure, anatomical structure, bending resistance and the energy required to cut stems of three varieties of sugar cane cultivated in the valle del cauca ( colombia ), were studied in order to have useful data for the development of cutting blades. microestructural and anatomical characterization tasks were performed by optical microscopy ( om), and scanning electron microscopy (sem). the physical and mechanical properties were determined after adaptation of astm standards (which were developed for wood), while the consumption of energy during cutting was evaluated by using a modified charpy type impact pendulum. the fibers and silica particles showed different geometry and distribution in the stems of the three studied varieties, and a relation was established between the microstructure of the stems and the energy required to cut them in the modified charpy pendulum. generally speaking, cutting the internodes required higher specific energy than cutting the nodes, and the use of blades with cutting angle of 20° led to lower levels of energy consumption. also, a relation of proportionality between the effective cross-sectional area of fibers (atef) and the specific energy consumed in cutting, as well as between the flexibility coefficient and the modulus of elasticity in bending were found.
CORRELACIóN ENTRE PROPIEDADES ANATóMICAS, RESISTENCIA A FLEXIóN ESTáTICA Y ENERGíA REQUERIDA PARA EL CORTE DE LA CA A DE AZúCAR (Saccharum officinarum L.) CORRELATIONS AMONG ANATOMIC PROPERTIES, BENDING RESISTANCE AND ENERGY REQUIRED TO CUT SUGAR CANE (Saccharum officinarum L.)
Hugo Alberto González Sánchez,Alejandro Toro Betancur,Fernando álvarez Mejía,Elkin Alonso Cortés Marín
Revista Facultad Nacional de Agronomía, Medellín , 2008,
Abstract: La microestructura, estructura anatómica, la resistencia a la flexión y la energía requerida durante el corte de los tallos de tres variedades de ca a de azúcar cultivadas en el Valle del Cauca (Colombia), fueron estudiados con el propósito de adquirir información útil para el desarrollo de cuchillas para corte de esta especie. Las labores de caracterización microestructural y anatómica se apoyaron en las técnicas de microscopía óptica y electrónica de barrido. Las propiedades mecánicas se determinaron adaptando algunas normas ASTM para maderas, mientras que la energía al corte se evaluó usando un péndulo de impacto tipo Charpy modificado. En los tallos de las tres variedades estudiadas se observaron diferentes distribuciones y dimensiones geométricas de las fibras y se verificó la presencia de partículas de sílice. Se presentó en general mayor requerimiento de energía específica al corte en los entrenudos que en los nudos y un menor consumo específico de energía al corte con las cuchillas con ángulo de afilado de 20°. Se establecieron relaciones entre la microestructura de los tallos, comportamiento a la flexión y al corte, destacándose la relación proporcional entre el área transversal efectiva de fibra (ATEF) y la energía específica al corte, así como entre el coeficiente de flexibilidad y el módulo de elasticidad en flexión. The microstructure, anatomical structure, bending resistance and the energy required to cut stems of three varieties of sugar cane cultivated in the Valle del Cauca ( Colombia ), were studied in order to have useful data for the development of cutting blades. Microestructural and anatomical characterization tasks were performed by optical microscopy ( OM), and scanning electron microscopy (SEM). The physical and mechanical properties were determined after adaptation of ASTM standards (which were developed for wood), while the consumption of energy during cutting was evaluated by using a modified Charpy type impact pendulum. The fibers and silica particles showed different geometry and distribution in the stems of the three studied varieties, and a relation was established between the microstructure of the stems and the energy required to cut them in the modified Charpy pendulum. Generally speaking, cutting the internodes required higher specific energy than cutting the nodes, and the use of blades with cutting angle of 20° led to lower levels of energy consumption. Also, a relation of proportionality between the effective cross-sectional area of fibers (ATEF) and the specific energy consumed in cutting, as well as between the fl
Biocombustibles: búsqueda de alternativas
Cortés Marírr,Elkin Alonso; Ciro Velásquez,Héctor José; Moreno Cárdenas,Edilson León;
CES Medicina Veterinaria y Zootecnia , 2011,
Abstract: today, the world is looking for different alternatives in order to solve the increasing difficulties that face its development, the feeding of its population and, in particular the feeding of developing nations. at the same time, the growing energy demand foreshadows the exhaustion of hydrocarbon reserves in the short and medium term and likewise a significant deterioration of natural resources, especially the contamination of water and the erosion of soil. in order to prevent irreversible changes and reduce the impact of greenhouse gases on the planet's climate, many countries have chosen to gamble on different strategies for the diversification of energy production utilizing renewable energy sources. the replacement of petroleum derived fuel with biofuels provides a reduction in co2 emissions generated by vehicles. this appears to indicate that the biofuels could potentially be an option, but one not without questions. the new agro-energy industry, unlike that of the oil industry, involves a production chain that impacts more directly the different sectors of the economy, especially the generation of employment, agricultural development and the agro-industry. the addition of biofuels to fuel mixtures can partially mitigate the need for the importation of hydrocarbons, which furthers the national biofuel policy versus energy trade balance, and to a certain extent defines the parameters for security at the supply level. the goal of this paper is to assess the possible scenario of replacement of the current energy matrix with vegetable derived alternative products.
BIOCOMBUSTIBLES Y AUTOSUFICIENCIA ENERGéTICA
CORTéS MARíN,ELKIN; SUAREZ MAHECHA,HECTOR; PARDO CARRASCO,SANDRA;
DYNA , 2009,
Abstract: the condition of finite and not renewable resource of fossil fuels, added to high atmospheric contamination in big populated centers, for the automotive park that participates in high proportion in the total consumption of primary energy have been unchaining factors for the promotion and study in the country of new energy or biofuels, starting from organic resources (vegetables or animals). colombia is a vulnerable country in hydrocarbons in front of exploration programs limitations due to absence of new important discoveries and to decrease of its reserves. consecuently, the country is "ad portas" of losing its oil self-sufficiency in the short term (2015 horizon) surround by an unfavorable conjuncture of high prices. everything added to bad quality by the high content of sulphur, particularly in diessel, which overcomes widely the established international levels. to diversify energy sources, to avoid degraded climatic change and to draw social rejection to polluting energy, become important challenges so that science and technology contribute to a sustainable development, well-known and supported by the citizens.
BIOCOMBUSTIBLES Y AUTOSUFICIENCIA ENERGéTICA
ELKIN CORTéS MARíN,HECTOR SUAREZ MAHECHA,SANDRA PARDO CARRASCO
DYNA , 2009,
Abstract: La condición de recurso finito y no renovable de los combustibles fósiles, sumado a la alta contaminación atmosférica generada en los grandes centros poblados, por el parque automotriz, que participa en alta proporción en el consumo total de energía primaria, han sido factores desencadenantes para la promoción y estudio en el país de nuevos energéticos o biocombustibles, a partir de recursos orgánicos (vegetales o animales). Colombia es un país vulnerable en hidrocarburos, debido a las limitaciones de los programas de exploración, ausencia de nuevos hallazgos importantes y disminución de las reservas. En consecuencia, el país está ad portas de perder su autosuficiencia petrolera en el corto plazo (horizonte de 2015) en medio de una desfavorable coyuntura de altos precios. Todo ello, sumado a la mala calidad por el alto contenido de azufre, particularmente en el diesel, el cual supera ampliamente los niveles establecidos internacionalmente. Diversificar las fuentes energéticas, evitar el cambio climático degradado y sortear el rechazo social a las energías contaminantes, constituyen retos importantes para que la ciencia y la tecnología contribuyan a un desarrollo sostenible, conocido y respaldado por los ciudadanos.
DETERMINATION OF THE ISOSTERIC HEAT TO PLANTAIN PULP (musa paradisiaca) BY SORPTION ISOTHERMS
CIRO,HéCTOR; OSORIO,JAIRO ALEXANDER; CORTéS,ELKIN ALONSO;
DYNA , 2008,
Abstract: for sorptional data to be useful in simulation and design of storage and drying systems, they must be represented by equations valid in the conditions usually found in industrial practice. using the modified chung-pfost model and fitted by desorption the net and total isosteric heat of plantain pulp was evaluated. the net isosteric heat decreased with increasing moisture content ranging from 1670 kj/kg (5%.d.b) to 215 kj/kg (26%.d.b) where the better goodness of fit was presented by polynomial and power-law models.
DETERMINATION OF THE ISOSTERIC HEAT TO PLANTAIN PULP (musa paradisiaca) BY SORPTION ISOTHERMS
HéCTOR CIRO,JAIRO ALEXANDER OSORIO,ELKIN ALONSO CORTéS
DYNA , 2008,
Abstract: Las isotermas de sorción para ser usadas en la simulación y dise o de procesos de secado y almacenamiento de alimentos deben ser representadas por modelos válidos dentro de las condiciones encontradas en la práctica industrial. Usando el modelo de Chung-Pfost y ajustado por desorción el calor isostérico neto y totalpara pulpa de plátano fueron determinados. El calor neto isotérico neto decreció con el contenido de humedad del producto variando desde 1670 kJ/kg (5%.d.b) a 215 kJ/kg (26%.d.b) donde esta variación fue representada por el modelo potencial y polinomial.
Levels of physical activity, barriers, and stage of change in an urban population from a municipality in Colombia
Arango,Elkin Fernando; Pati?o,Fredy Alonso; Quintero,Mario Andrés; Arenas,Mónica María;
Colombia Médica , 2011,
Abstract: objective: to assess the levels of physical activity, barriers, and stage of change in an urban population 25 to 50 years of age from the municipality of santa rosa de osos, department of antioquia. materials and methods: a prevalence study was conducted, with a two-stage random sampling among 357 individuals not suffering from any known cardiovascular disease. a pre-designed survey was conducted to assess the levels of physical activity, the stage of change, and physical activity barriers. results: the total low physical activity was 9%, and by domains: work 66.9%, transport 60.8%, household and garden (yard work) 44.8%, and leisure-time 76.2%. the most important physical activity barriers were ?lack of willpower? (70%) and ?lack of time? (46.2%). the most prevalent stages of change were ?contemplation? (40.3%) and ?preparation? (17.1%). conclusion: low physical activity levels were found in different domains of daily life, together with a high prevalence of barriers and stages prior to physical activity practice, mainly among women and obese subjects.
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