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Simulation of Plain Bearings in Turbo-Generators Using the Stand ISO7902 Simulación de cojinetes de deslizamiento en turbogeneradores con empleo de la norma ISO 7902
Alejandra Elena García Toll,David Hernández Moncisbaez,Yerisey González Hernández
Revista Cubana de Ingeniería , 2011, DOI: 10.1234/rci.v2i1.40
Abstract: The study of plain bearings is fundamental in guaranteeing the full running and maintenance of machines. Due to the fluctuations in working conditions, the simulation of plain bearing in turbines and generators has become increasingly necessary. The procedure used to obtain data is based on ISO Standards 7902:1998 which involves the calculation of the load capacity of plain bearings under hydrodynamic lubricant conditions. This method can be used to determine if the plain bearing under load and working conditions will be able to form and maintain a film of lubricant which is important to separate completely the shaft and bearing sliding surfaces in order to prevent friction between these two. Also, with this method it is possible to determine the ideal working conditions and limiting factors in the functioning of plain bearing. Some of these factors are: relative bearing clearance, shaft velocity, lubricant viscosity, diameter and width of bearing, average peak-to-valley height of sliding surfaces and nominal radial. Additionally, a calculation sample is presented El estudio de pares tribológicos de deslizamiento es indispensable para garantizar el adecuado funcionamiento y correcto mantenimiento de las máquinas. En el presente artículo se muestran resultados en la simulación de cojinetes de deslizamiento de un turbogenerador para diferentes condiciones de trabajo con el uso de un método de cálculo que valora la capacidad de carga de cojinetes en condiciones de lubricación hidrodinámica. El método de cálculo que se propone consiste en determinar si el cojinete, bajo el efecto de las cargas y en las condiciones de trabajo, es capaz de formar y mantener una cu a de lubricante que impida el contacto de las superficies. Con el uso de este método se pueden determinar los factores que influyen en el buen establecimiento de la cu a de lubricante, lo que permite garantizar las correctas condiciones de funcionamiento de los cojinetes de deslizamiento. Algunos de estos factores son: la holgura radial, la velocidad de giro del árbol, la viscosidad del lubricante, el diámetro y la longitud del cojinete, la rugosidad superficial y la carga radial. Adicionalmente, en el artículo se muestra un ejemplo de cálculo.
The Role of PET/CT Imaging in Lung Cancer  [PDF]
David Ladrón de Guevara Hernández
Journal of Cancer Therapy (JCT) , 2015, DOI: 10.4236/jct.2015.68076
Abstract: Lung cancer presents a high prevalence around the world and constitutes the leading cause of death due to cancer in men and women. Proper staging is essential in order to provide the correct treatment and estimate survival. PET/CT imaging is the method of choice for the staging of lung cancer patients with a better performance than the traditional imaging methods. It allows defining the primary tumor more clearly, separating it from the atelectasis and neighboring fibrotic changes, thus achieving an improved T evaluation while optimizing the target definition for radiotherapy. It presents greater sensibility and specificity than Computed Tomography (CT) when assessing the extra-thoracic and thoracic lymph nodes, modifying the N stage with regard to the traditional study in up to 25% of patients. PET/CT imaging is the method with the best performance for detecting extra-encephalic metastasis and for detecting unexpected lesions in up to 30% of patients. In order to achieve proper encephalic staging, a Magnetic Resonance Imaging scan must be performed or, a CT scan of the brain concomitant to the PET/CT. One to eight percent of lung cancer patients who are subjected to PET/CT imaging present a synchronous secondary extra pulmonary or pulmonary cancer when being diagnosed, with significant prognostic and therapeutic implications. PET/CT imaging has proven to be a valuable tool for survival prognosis with regard to the initial uptake of the tumor and the early response (interim) or final response to chemotherapy, although it is not routinely used for evaluating therapy. The PET/MRI is an emerging hybrid technique with certain advantages, such as less exposure to radiation in comparison to PET/CT and greater contrast resolution of the MRI images. However, its usefulness has not been validated yet for lung cancer patients.
El compromiso de Eneas. Virtud y democracia radical tras la dialéctica de la Ilustración
Hernández Castro, David
Isegoría , 2009,
Abstract: The aporia resulting from Horkheimer and Adorno’s critique of the Dialectic of Enlightenment has been raised after the hermeneutic turn of the tradition started by Nietzsche and Heidegger. Essentially it proposes a new Western philosophy beginning, starting from the ontological duality established by the presocratics and maintained by Aristotle against the monological reason of Plato’s teachings. Starting from a new point of view on the Nicomachean and Eudemian ethics, the author puts forward a critique of modern views on Aristotle’s virtue theory, including MacIntyre, in order to propose a new approach to connect the practice of virtue to radical democracy. La aporía de la dialéctica de la Ilustración ha sido replanteada después de Horkheimer y Adorno por el giro hermenéutico de la tradición que nace con Nietzsche y Heidegger, y que básicamente propone un nuevo comienzo de la filosofía occidental volviendo a la raíz de la dualidad ontológica establecida por los presocráticos y sostenida por Aristóteles frente a la razón monológica de la Academia de Platón. A partir de una nueva interpretación de las éticas Eudemia y Nicomaquea, el autor afrontará una crítica de las visiones modernas de la teoría aristotélica de la virtud, incluida la de MacIntyre, para exponer un nuevo enfoque que vincula la práctica de la virtud con la democracia radical.
La formación del contrato electrónico en el marco de la Comunidad Andina
William David Hernández
Civilizar Ciencias Sociales y Humanas , 2012,
Abstract: The influence of the Information and Communication Technology (ICT) in all the aspects of the society is an unquestionable fact that implies, for the Law, the inescapable responsibility of fostering the fulfillment of the declarations or objectives of the Society of Information. Today′s world, framed in a process of globalization and regional integration, heads to the normative harmonization. In line with the above, the present document studies the elements supporting the normative unification concerning the formation of the contract by electronic means in the Andean Community.
RNA interference is ineffective as a routine method for gene silencing in chick embryos as monitored by fgf8 silencing
Hernández Victor Hernández,Bueno David
International Journal of Biological Sciences , 2005,
Abstract: The in vivo accessibility of the chick embryo makes it a favoured model system for experimental developmental biology. Although the range of available techniques now extends to miss-expression of genes through in ovo electroporation, it remains difficult to knock out individual gene expression. Recently, the possibility of silencing gene expression by RNAi in chick embryos has been reported. However, published studies show only discrete quantitative differences in the expression of the endogenous targeted genes and unclear morphological alterations. To elucidate whether the tools currently available are adequate to silence gene expression sufficiently to produce a clear and specific null-like mutant phenotype, we have performed several experiments with different molecules that trigger RNAi: dsRNA, siRNA, and shRNA produced from a plasmid coexpressing green fluorescent protein as an internal marker. Focussing on fgf8 expression in the developing isthmus, we show that no morphological defects are observed, and that fgf8 expression is neither silenced in embryos microinjected with dsRNA nor in embryos microinjected and electroporated with a pool of siRNAs. Moreover, fgf8 expression was not significantly silenced in most isthmic cells transformed with a plasmid producing engineered shRNAs to fgf8. We also show that siRNA molecules do not spread significantly from cell to cell as reported for invertebrates, suggesting the existence of molecular differences between different model systems that may explain the different responses to RNAi. Although our results are basically in agreement with previously reported studies, we suggest, in contrast to them, that with currently available tools and techniques the number of cells in which fgf8 gene expression is decreased, if any, is not sufficient to generate a detectable mutant phenotype, thus making RNAi useless as a routine method for functional gene analysis in chick embryos.
APROVECHAMIENTO DE CHAPA DE CORTAS DIMENSIONES PARA AUMENTAR LA PRODUCCION DE TRIPLAY
Zavala,David; Hernández,Yeriley;
Maderas. Ciencia y tecnología , 2002, DOI: 10.4067/S0718-221X2002000200001
Abstract: the mechanical properties and the revenue of plywood from pinus duranguensis martínez with traditional o standard cores of 1.22 m and modified cores of 0.61 m long were analyzed. boards of 9, 12, 16 y 19 mm thick were mechanically evaluated, integrated by four standards, four modified with one core and one additional board of 19 mm with two cores of 0.61 m. it was determined that the modified boards of 9, 12 and 16 mm are less strong than the traditional boards of the same thickness and that the 19 mm boards modified with one core have statistically similar values in strength and stiffness that the standard boards of the same thickness. the production costs for the modified boards increased in the assembling and pressing areas in a proportional percentage of the assembling time. it is concluded that the 19 mm boards modified with one core are profitable, can be commercialized and used in a similar way as the standard boards of the same thickness. it is considered that part of the veneer that is lost (11%) in the green area and in the clippers can be recovered to produce boards of 19 mm thickness, modified in one core
Medición de calidad en los procesos judiciales del Sistema Penal Acusatorio colombiano*
Hernández García,David;
Revista de Derecho , 2012,
Abstract: this article presents the results obtained during project of design, validation and implementation of a standard -and its associated index-, to measure the quality of the judicial process in the colombian accusatory penal system. this project was developed to attend the needs of measurement of justice sector and provide specific tools to assess quality comparatively over time and create opportunities for continuous improvement. this project required two stages of research and implicated different issues and processes to improve the organization and administration of justice in colombia.
APROVECHAMIENTO DE CHAPA DE CORTAS DIMENSIONES PARA AUMENTAR LA PRODUCCION DE TRIPLAY UTILIZATION OF SHORT DIMENSION VENEER TO INCREASE PLYWOOD PRODUCTION
David Zavala,Yeriley Hernández
MADERAS : Ciencia y Tecnología , 2002,
Abstract: Se analiza la resistencia mecánica y la rentabilidad de tableros contrachapados de Pinus duranguensis Martínez con centros tradicionales o estándares de 1.22 m y centros modificados de 0.61 m de longitud. Se evaluaron mecánicamente tableros de 9, 12, 16 y 19 mm de espesor, integrados por cuatro tradicionales, cuatro modificados con un centro y un tablero adicional de 19 mm con dos capas de centros de 0.61 m. Se determinó que los tableros modificados de 9, 12 y 16 mm son menos resistentes que los tradicionales del mismo espesor y los de 19 mm modificados con un centro presentan valores de resistencia y rigidez estadísticamente iguales a los tableros estándares del mismo espesor. Los costos de producción para los tableros modificados aumentaron en las áreas de ensamblado y prensado en un porcentaje proporcional al incremento del tiempo de armado. Se concluye que es rentable fabricar tableros de 19 mm modificados con un centro, que pueden comercializarse y utilizarse en forma similar que los tableros estándares del mismo espesor. Se considera que parte de la chapa que actualmente se pierde (11%) en las áreas de "mesa verde" y "perfilado" se puede aprovechar para la producción de tableros de 19 mm, modificados en un centro The mechanical properties and the revenue of plywood from Pinus duranguensis Martínez with traditional o standard cores of 1.22 m and modified cores of 0.61 m long were analyzed. Boards of 9, 12, 16 y 19 mm thick were mechanically evaluated, integrated by four standards, four modified with one core and one additional board of 19 mm with two cores of 0.61 m. It was determined that the modified boards of 9, 12 and 16 mm are less strong than the traditional boards of the same thickness and that the 19 mm boards modified with one core have statistically similar values in strength and stiffness that the standard boards of the same thickness. The production costs for the modified boards increased in the assembling and pressing areas in a proportional percentage of the assembling time. It is concluded that the 19 mm boards modified with one core are profitable, can be commercialized and used in a similar way as the standard boards of the same thickness. It is considered that part of the veneer that is lost (11%) in the green area and in the clippers can be recovered to produce boards of 19 mm thickness, modified in one core
Los medios de comunicación y la estructuración de las audiencias masivas
David González Hernández
Estudios sobre las Culturas Contemporaneas , 2009,
Abstract: El trabajo es un planteamiento conceptual para el estudio de la relación medios-audiencia desde una perspectiva estructural pero con énfasis en lo que comúnmente se denomina recepción. Para ello, se examinan avances en tres sistemas de interpretación que encontraron un sustento esencial en la teoría de la estructuración de Anthony Giddens; Klaus Bruhn Jensen desde el pragmatismo y la semiótica peirciana; John B. Thompson desde la teoría social y el marco interpretativo de la hermenéutica profunda; y Guillermo Orozco desde las mediaciones, la comunicación y educación. Tres autores que han re-establecido algunas certezas teórico-metodológicas en relación con la comunicación y su estudio. Esto supone discutir fuentes teóricas, tradiciones y articulaciones para enfocarse en los conceptos claves y abarcar lo que queda nebuloso en las teorías y maneras de acercarse al estudio de la relación de los sujetos con los medios.
En busca del entretenimiento: televisión y audiencia juvenil en la frontera norte
David González Hernández
Comunicación y sociedad , 2006,
Abstract: Este artículo ofrece un análisis intercultural de la recepción televisiva estadounidense y mexicana entre los jóvenes de la ciudad de Tijuana mediante la exploración de la subjetividad, así como una descripción de la oferta televisiva en la frontera. Lo anterior, busca enfatizar el potencial y papel legitimador, especialmente de entretenimiento, que conllevan los programas estadounidenses en la configuración de la cultura televisiva en la frontera, estructurada, en este caso, mediante interacciones trasfronterizas en tiempos de globalización.
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