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Glass fibre is the most widely used material for reinforcing thermoplastic matrices presently and its use continues to grow. A significant disadvantage of glass fibre, however, is its impact on the environment, in particular, due to the fact that glass fibre-reinforced composite materials are difficult to recycle. Polyamide 6 is an engineering plastic frequently used as a matrix for high-mechanical performance composites. Producing polyamide monomer requires the use of a large amount of energy and can also pose harmful environmental impacts. Consequently, glass fibre-reinforced Polyamide 6 composites cannot be considered environmentally friendly. In this work, we assessed the performance of a road cycling pedal body consisting of a composite of natural Polyamide 11 reinforced with lignocellulosic fibres from stone-ground wood, as an alternative to the conventional glass fibre-reinforced Polyamide 6 composite (the most common material used for recreational purposes). We developed a 3D model of a pedal with a geometry based on a combination of two existing commercial choices and used it to perform three finite-element tests in order to assess its strength under highly demanding static and cyclic conditions. A supplementary life cycle analysis of the pedal was also performed to determine the ecological impact. Based on the results of the simulation tests, the pedal is considered to be mechanically viable and has a significantly lower environmental impact than fully synthetic composites.
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Newspapers have a limited lifespan, and therefore represent a focus of used and disposed paper. While these refuses have a considerable value and can be easily recycled, a considerable fraction ends in landfill. The authors show the possibility of adding value to used newspaper and enlarge its value chain. Old newspaper incorporates a high amount of wood fibers able to be used as reinforcement. On the other hand, this material also incorporates inks and other components inherent to newspaper production. In this work, the authors disintegrate old newspaper to recover and individualize wood fibers. A morphological analysis showed that the recovered fibers had aspect ratios higher than 10, revealing, a priori, their strengthening capabilities. Thereupon, these fibers were compounded with polypropylene at different contents, ranging from 20% to 50% w/w. It is well known that wood fibers are hydrophilic, while polyolefin are hydrophobic. This is a drawback to obtaining strong interfaces. Thus, two sets of composites were produced, with and without a coupling agent. The results showed that uncoupled composites increased the flexural strength of the matrix but reached an equilibrium point from which adding more reinforcement did not changer the flexural strength. On the other hand, the coupled composites showed a linear increase of the flexural strength against the reinforcement content. The flexural moduli of the coupled and uncoupled composites were very similar and evolved linearly with the reinforcement content.
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BACKGROUND AND OBJECTIVE: Currently, many orthopedic operations are planned by analyzing X-rays. The exact position of the focus is needed to calculate the real size of an object that is represented in conical projection, although in practice, this position is difficult to determine using current X-ray commercial systems. In this paper, a new geometric model is proposed in order to determine accurately, practically, and economically the location of the emitting source of commercial imaging systems using a single standard X-ray image. METHOD: The method requires a specific reference locator object to be positioned in the visual field of radiographic image. Because this object cannot implement ideal geometric points, but instead works with small spheres, it was necessary to experimentally validate the proposed methodology. The implemented software that was developed to validate the model was used in four series of tests. In these tests, we studied the influence on the final result of: 1. the selection of a specific set of markers in radiography, 2. the focus position variation in relation to radiograph and 3. the possible rotated angle of locator object about Z axis. RESULTS: The results for 164 tests that were performed with this software showed that the expected error for 99.5% of values ranges with maximum error of [-0.35%, +0.39%], which shows that the model is independent of the design of locator object and its position and orientation in the radiographic field. The software used to validate the proposed model has been found useful to verify its reliability, effectiveness, ease of implementation, and accuracy. CONCLUSIONS: This model is effective to calculate the precise position of the X-ray focus of any standard radiographic system accurately.
Assuntos
Algoritmos , Modelos Teóricos , Tomografia Computadorizada por Raios X , Humanos , Raios XRESUMO
El objetivo del trabajo fue revisar, a través de la base de datos JCR del Web of Science (ISI), los trabajos realizados sobre la categoría temática de Ciencias de la Computación en Venezuela y publicados en revistas internacionales con factor de impacto entre los años 1997 y 2007. Se encontraron 181 trabajos en 95 revistas, todos en inglés. Cuatro universidades aglutinan el 93,92% de toda la producción científica universitaria: Universidad Simón Bolívar (USB), Universidad de los Andes (ULA), Universidad Central de Venezuela (UCV) y La Universidad del Zulia (LUZ), destacando la USB con 57 artículos (32,95%) y habiéndose observado un notable incremento de la producción científica a partir del año 2005. Sin embargo, en cuanto a factor de impacto, destaca la ULA. Las Instituciones de Investigación solo aportaron el 7,73% de toda la producción científica analizada. Asimismo se destacó una alta colaboración internacional.
The objective of this study was to review, through the JCR database in the Web of Science (ISI), the scientific production in the Computer Science subject category in Venezuela and published in international journals with impact factor between the years 1997 and 2007. We found 181 articles in all 95 journals, all of them in English. Four universities aggregate 93.92% of the entire university scientific output: Universidad Simón Bolívar (USB), Universidad de los Andes (ULA), Universidad Central de Venezuela (UCV) and La Universidad del Zulia (LUZ), USB standing out with 57 items (32.95%) and a remarkable increase in scientific output from 2005 having been observed. However, in terms of impact factor outstands ULA. Research institutions only accounted for 7.73% of all the scientific analysis. A remarkable international collaboration is also highlighted.
O objetivo deste estudo foi revisar, através da base de dados JCR da Web of Science (ICI), os trabalhos realizados sobre a categoria temática de Ciências da Computação na Venezuela e publicados em revistas internacionais com fator de impacto entre os anos 1997 e 2007. Encontraram-se 181 trabalhos em 95 revistas, todos em inglês. Quatro universidades aglutinam 93,92% de toda a produção científica universitária: Universidade Simón Bolívar (USB), Universidade dos Andes (ULA), Universidade Central de Venezuela (UCV) e A Universidade del Zulia (LUZ), destacando a USB com 57 artigos (32,95%) e tendo-se observado um notável incremento da produção científica apartir do ano 2005. No entanto, quanto ao fator de impacto, destaca a ULA. As Instituições de Investigação somente aportaram 7,73% de toda a produção científica analisada. Também se destacou uma alta colaboração internacional.
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Se muestra el estudio hidráulico de una típica instalación de un batán, situado en el término de Alfoz (Lugo, España) y que representa fielmente las características comunes a todos ellos. Asimismo se ha realizado un modelo virtual del mismo, modelándose en 3D y dotándolo de animación por ordenador para comprender su funcionamiento. Igualmente se expone un estudio realizado sobre la rueda vertical de los batanes, para obtener conclusiones a partir de la comparación con el estudio realizado con las ruedas horizontales de los molinos hidráulicos obteniendo, por tanto, datos sobre la eficiencia de ambas tecnologías.
Assuntos
Arqueologia , Desenho Assistido por Computador , Processamento de Imagem Assistida por Computador , Indústrias , Engenharia , EspanhaRESUMO
El artículo presenta una visión actual de las diferentes técnicas utilizadas para la difusión del patrimonio cultural, centrado fundamentalmente en los museos y el diseño de sus páginas web. Se introducen conceptos relativos al citado patrimonio, tales como la conservación, la preservación y la difusión del mismo, y se presentan los contendedores de dicho patrimonio en la forma de archivos, bibliotecas y museos. Por otro lado, se hace hincapié en la necesidad de pasar de la sociedad de la información a la sociedad del conocimiento, lo que conlleva una redefinición de los diseños museísticos, de forma que el visitante interactúe con el website, y acceda a comprender mejor sus contenidos. Por último, se presenta un estudio realizado sobre los websites de Museos de Ciencia y Tecnología de Venezuela, estableciendo propuestas de mejora
Assuntos
Internet , Museus , Ciência , Tecnologia , VenezuelaRESUMO
En este artículo se muestran algunos aspectos tecnológicos, como el estudio hidráulico, el del rodezno y el rendimiento industrial de una instalación molinera típica del sureste español, así como un modelo virtual de la misma, dado su defectuoso estado. Se trata de un molino hidráulico, situado en el término de Baza (Granada, España), que representa fielmente las características comunes a todos ellos. Dado el estado en el que se encuentra se ha modelado en 3D y se ha realizado una animación por ordenador, para comprender su funcionamiento
