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Search Results: 1 - 10 of 607656 matches for " Arzola de la Pe?a Nelson "
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Valoración económica sobre la aplicabilidad de inspección ultrasónica a los árboles de los molinos de ca?a de azúcar para la industria azucarera cubana
Arzola de la Pea,Nelson;
Ingeniería e Investigación , 2006,
Abstract: this article evaluates the economic feasibility of carrying out ultrasonic inspection of sugar-mill shafts. four alternatives are considered, including the most frequently encountered scenarios. how and when inspections are carried out is analysed, periods between inspections being established by a fatigue-crack growth propagation approach. the lifecycle cost approach was applied for economic evaluation. operation, maintenance and energy consumption costs were thus taken into consideration. the conclusion was drawn that it is highly advisable to use high performance ultrasonic inspection. introducing ultrasonic inspection (according to the period of time obtained by fracture mechanics model) could lead to a saving of half a million dollars per year for the cuban sugarcane industry in the current conditions.
Determinación experimental del coeficiente de rigidez del bagazo
Arzola de la Pea,Nelson;
Ingeniería e Investigación , 2007,
Abstract: the experimentally determined stiffness coefficient of bagasse is described in this paper. this property defines the behaviour of the reaction forces exerted upon the bagasse layer when being compressed during juice-extraction in a sugar-cane mill. this information is important for correctly analysing sugar-cane mill operation and design. an experimental device was used for obtaining the stiffness coefficient; it consisted of a piston, a piston-skirt, a hydraulic press and instrumentation for measuring the pressures so produced and piston position at different times. compression rate, humidity level and degree of bagasse fragmentation were the experimental factors taken into account in the experimental design. the investigation was carried out with 40%-80% humidity level and up to 0.06 compression rates. all experimental factors proved statistically significant in the bagasse stiffness coefficient experimental model so obtained. bagasse was seen to behave as a very rigid elastic material under normal sugar-mill pressure operating conditions, having 50 mpa to 20,000 mpa stiffness coefficient values.
Determinación experimental del coeficiente de rigidez del bagazo Experimental determination of bagasse stiffness coefficient
Arzola de la Pea Nelson
Ingeniería e Investigación , 2007,
Abstract: En el artículo se determina experimentalmente el coeficiente de rigidez del bagazo comprimido. Esta propie-dad define el comportamiento de la reacción que ejerce el colchón de bagazo a su paso por los molinos de ca a de azúcar en el proceso de extracción de los jugos, siendo de importancia para un correcto análisis del funcionamiento y el dise o de los molinos. En la obtención del coeficiente de rigidez se empleó un dispositivo experimental compuesto por un pistón, camisa, prensa hidráulica e instrumentación para el registro de las pre-siones generadas, y la posición del pistón en función del tiempo. Los factores experimentales tenidos en cuenta en el dise o experimental son: relación de compresión, porcentaje de humedad y grado de fragmentación del bagazo. Se experimentó con un porcentaje de humedad entre el 40% y el 80%, y se alcanzaron relaciones de compresión de hasta 0,06. Se obtuvo un modelo experimental para el coeficiente de rigidez del bagazo donde todos los factores experimentales resultaron estadísticamente significativos. Se concluye que el bagazo se com-porta como una fundación elástica muy rígida bajo las condiciones de presión existentes en un molino de ca a, con valores del coeficiente de rigidez en el rango de 50 MPa a 20.000 MPa. The experimentally determined stiffness coefficient of bagasse is described in this paper. This property defines the behaviour of the reaction forces exerted upon the bagasse layer when being compressed during juice-extraction in a sugar-cane mill. This information is important for correctly analysing sugar-cane mill operation and design. An experimental device was used for obtaining the stiffness coefficient; it consisted of a piston, a piston-skirt, a hydraulic press and instrumentation for measuring the pressures so produced and piston position at different times. Compression rate, humidity level and degree of bagasse fragmentation were the experimental factors taken into account in the experimental design. The investigation was carried out with 40%-80% humidity level and up to 0.06 compression rates. All experimental factors proved statistically significant in the bagasse stiffness coefficient experimental model so obtained. Bagasse was seen to behave as a very rigid elastic material under normal sugar-mill pressure operating conditions, having 50 MPa to 20,000 MPa stiffness coefficient values.
Valoración económica sobre la aplicabilidad de inspección ultrasónica a los árboles de los molinos de ca a de azúcar para la industria azucarera cubana Economic feasibility study regarding the applicability of ultrasonic inspection of the Cuban sugar industry’s sugarcane mill shafts
Arzola de la Pea Nelson
Ingeniería e Investigación , 2006,
Abstract: Se presenta un análisis económico que evalúa la factibilidad de emplear inspección ultrasónica para los árboles de los molinos de ca a de azúcar. Se emplean cuatro variantes de sustitución de los árboles de los molinos que recrean los escenarios más frecuentes. Se incluye la alternativa de utilizar inspección ultrasónica, con periodos de tiempo entre inspecciones filados según un modelo de propagación de grietas de fatiga. En la valoración económica se utiliza el criterio del costo del ciclo de vida; teniendo en cuenta los costos de operación, mantenimiento y energía que influyen sobre los árboles de los molinos de ca a de azúcar. Se llega a la conclusión de que es bastante recomendable emplear inspección ultrasónica con un nivel alto en las especificaciones del procedimiento. Con la introducción de la inspección ultrasónica, según los tiempos obtenidos por el modelo de mecánica de la fractura, es posible lograr un ahorro de medio millón de dólares por a o para las condiciones existentes en la industria azucarera cubana. This article evaluates the economic feasibility of carrying out ultrasonic inspection of sugar-mill shafts. Four alternatives are considered, including the most frequently encountered scenarios. How and when inspections are carried out is analysed, periods between inspections being established by a fatigue-crack growth propagation approach. The lifecycle cost approach was applied for economic evaluation. Operation, maintenance and energy consumption costs were thus taken into consideration. The conclusion was drawn that it is highly advisable to use high performance ultrasonic inspection. Introducing ultrasonic inspection (according to the period of time obtained by fracture mechanics model) could lead to a saving of half a million dollars per year for the Cuban sugarcane industry in the current conditions.
Predicción de vida remanente en ejes de masa superior de molino de ca?a
Rodríguez Pulecio,Sara; Coronado Marín,John Jairo; Arzola de la Pea,Nelson;
Ingeniería e Investigación , 2006,
Abstract: a fracture mechanics-based method is presented for determining critical crack size and residual life of upper sugar-mill shafts having semi-elliptical and circumferential cracks. due to the multiaxial stress field, an equivalent strain energy release rate stress intensity solution is used in paris? law to predict crack growth. ultrasonic inspection intervals for the shaft were established. the crack zone evaluated was located in the shoulder of the bearing nearest to the square box coupling where about 25% of service failures in these types of shaft are observed.
Técnicas de dise?o óptimo multidisciplinario
Tovar,Andrés; Arzola de la Pea,Nelson; Gómez,Alexander;
Ingeniería e Investigación , 2007,
Abstract: design optimisation of a multidisciplinary project in engineering involves the decomposition of a system into disciplines and the subsequent association of their contributions. this work was aimed at presenting the most common decomposition and association techniques currently used in multidisciplinary design optimisation (mdo). amongst the decomposition techniques this work includes hierarchical and non-hierarchical approaches as well as the most popular numerical procedures. the association techniques include: one-level methods (e.g. all-at-once optimisation and simultaneous analysis and design), multilevel methods (e.g. concurrent subspace optimisation and collaborative optimisation) and robust design. this work also incorporates an illustrative numerical example.
Predicción de vida remanente en ejes de masa superior de molino de ca a Predicting remaining life in upper sugar-mill shafts
Rodríguez Pulecio Sara,Coronado Marín John Jairo,Arzola de la Pea Nelson
Ingeniería e Investigación , 2006,
Abstract: En este artículo se presenta un método basado en la mecánica de fractura para el cálculo del tama o critico de fisuras y la vida remanente de un ele de masa superior de molino de ca a de azúcar, con fisuras semielípticas y circunferenciales. Debido a la presencia de un campo de esfuerzos multiaxiales es necesario usar en la ley de París un factor de intensidad de esfuerzos equivalente. Se obtuvieron los intervalos entre inspección requeridos para evitar una falla por fatiga de estos elementos. Para el cálculo de vida residual y tama o de fisura máxima se considera la zona localizada en el cambio de diámetro del guilo más próximo al acoplamiento cuadrado, donde se encontró el 25% de las fallas. A fracture mechanics-based method is presented for determining critical crack size and residual life of upper sugar-mill shafts having semi-elliptical and circumferential cracks. Due to the multiaxial stress field, an equivalent strain energy release rate stress intensity solution is used in Paris’ law to predict crack growth. Ultrasonic inspection intervals for the shaft were established. The crack zone evaluated was located in the shoulder of the bearing nearest to the square box coupling where about 25% of service failures in these types of shaft are observed.
Técnicas de dise o óptimo multidisciplinario Multidisciplinary design optimisation techniques
Tovar Andres,Arzola de la Pea Nelson,Gómez Cassab Alexander
Ingeniería e Investigación , 2007,
Abstract: El proceso de optimización de un proyecto multidisciplinario en ingeniería involucra la descomposición de un sistema en distintas disciplinas y la posterior asociación de sus contribuciones. El objetivo de este trabajo es presentar los esquemas de desagregación y asociación más utilizados actualmente en procesos de dise o óptimo multidisciplinario — Multidisciplinary Design Optimization (MDO). Entre los esquemas de desagregación se presentan la descomposición jerárquica y no jerárquica, así como los métodos computacionales más comunes. Los esquemas de asociación incluyen: formulación de un solo nivel (e.g., optimización integrada y análisis y dise o simultáneos), formulación de múltiples niveles (e.g., optimización en espacios concurrentes y optimización colaborativa) y dise o robusto. El trabajo presenta también un ejemplo de aplicación resuelto numéricamente. Design optimisation of a multidisciplinary prolect in engineering involves the decomposition of a system into disciplines and the subsequent association of their contributions. This work was aimed at presenting the most common decomposition and association techniques currently used in multidisciplinary design optimisation (MDO). Amongst the decomposition techniques this work includes hierarchical and non-hierarchical approaches as well as the most popular numerical procedures. The association techniques include: one-level methods (e.g. all-at-once optimisation and simultaneous analysis and design), multilevel methods (e.g. concurrent subspace optimisation and collaborative optimisation) and robust design. This work also incorporates an illustrative numerical example.
Reconocimiento a la vida y obra del Profesor Dr. C. Julio Noel González Jiménez autor del primer trasplante de corazón en Cuba Acknowledge professor and Doctor Julio Noel González Jiménez's life and work as the first performer of a heart transplant in Cuba
Nelson Aguiar González de la Pea
Revista Habanera de Ciencias M??dicas , 2011,
Abstract:
Aproximación a la historia de la medicina en Cuba: La colonia
Aguiar González de la Pea,Nelson Miguel; Benítez Pi?ón,Lourdes Matilde;
Revista Habanera de Ciencias M??dicas , 2010,
Abstract: a literature review was carried out aining at highlighting the most important landmarks that influenced on the development of medicine in the colonial stage, from the beginning up to the first us army intervention in 1899. a synthesis of the relevant moments of the organization of the public health in the period was made, with emphasis on the first adopted hygienic-sanitary measures and their implementation in the different phases; on the beginning of medical training and their later evolution; on the foundation of the first educational centers in the country and on the support and promotion given by economic societies and scientific institutions which offered an impulse to the development of science in general and of medicine in particular. a reference is also made to the most significant personalities at that time, who due to their for cultural and medical knowledge, their personal example and their contributions to the different specialties, constitute forced referents and paradigms of healthcare sciences in cuba.
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