Revistas Universidad del Bío-Bío
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Effects of microcrystalline cellulose on some performance properties of chitosan aerogels
Get PDFThe aim of this research was to investigate the effect of the microcrystalline cellulose reinforcement on some physical, mechanical, thermal, and morphological properties of the chitosan aerogels. The bio-based chitosan aerogels were produced using chitosan as a matrix and the microcrystalline cellulose as a reinforce material through freeze-drying method. The aerogel suspensions were prepared in five different ratios to investigate the effect of microcrystalline cellulose content. The density, porosity, thermogravimetric analysis, and compressive resistance tests were conducted according to relevant standards. Morphological properties were investigated using scanning electron microscope. The introduction of microcrystalline cellulose significantly improved the compressive resistance, thermal properties (Tonset and T%50) of the chitosan aerogels. The optimum performance properties determined as 0,12 MPa for compressive resistance, 0,27 MPa for compressive modulus, 292,45 °C for Tonset and 365 °C for T%50. According to scanning electron microscope images, aerogels showed microporous structure as expected. As a result, the bio-based chitosan aerogels reinforced with microcrystalline cellulose were successfully manufactured. The mechanical and thermal properties including compressive resistance, compressive modulus, Tonset and T%50 of chitosan- microcrystalline cellulose aerogels found promising
Evaluation of Eucalyptus woodchip utilization as fuel for thermal power plants
Get PDFThis paper aims to evaluate the implications of Eucalyptus woodchip utilization as an alternative solid fuel for thermal power plants, highlighting its energy properties, power generation expenses and unit variable costs. Woodchip samples were collected from different sources and a proximate analysis was carried out in order to determine their moisture content, basic and bulk densities, ash content and higher heating value. Then, with these properties, empirical indices of a 10-megawatt thermal power plant were used to simulate the potential woodchip consumption, the forest area needed and the unit variable cost (US$·MWh−1) for each sample. The results indicate that woodchip samples with lower moisture content and improved higher heating value presented: reduced woodchip consumption for the same power generation, decreased generation expenses, reduced unit variable costs and smaller Eucalyptus plantations area needed to supply the woodchip consumption. Greater energy density may result in lower transportation and storage expenses, however, does not indicate better generation performance, since it is influenced by biomass field conditions. All samples obtained satisfactory levels of ash content, which may result in lower emissions of pollutants and superior operational efficiency. Finally, all samples presented unit variable costs below the limit established by the government for participation in the regulated energy market, which might be an economic attraction for this kind of project. Therefore, Eucalyptus woodchip moisture content, higher heating value and energy density are key issues in sustainable thermal power generation, and should be managed by Eucalyptus power plants in order to reach better generation performance and reduced expenses
Shear and adhesion strength of open and closed system heat-treated wood samples
Get PDFThis paper investigated the effects of heat treatment in open (atmospheric pressure) and a closed (under pressure) system on the shear and adhesion strength of Scots pine (Pinus sylvestris) wood. In addition, pull-off adherence testing was carried out of the coatings with water-based, polyurethane-based and oil/wax-based varnishes. Shear strength decreased significantly after heat treatment in Scots pine (31 % to 39 %) in open system, while it decreased between 2 % and 38% in the closed system without glue. The shear strength of the wood samples glued with glue was higher than the samples without glue at laboratory scale. The lower shear strength of modified wood could be attributed to other factors, such as the reduced chemical bonding or mechanical interlocking of adhesives, and the reduced strength of brittle modified wood substrate. With increasing heat treatment temperature adherence decreased. Maximum pull-off adhesion (4,80 MPa) was observed in the control samples coated with PUR
Bonding quality of two lesser-used wood species Brachystegia spiciformis and Julbernardia globiflora, from mozambique
Get PDFThe objective of this study was to evaluate the density, chemical properties and bonding quality of two lesser-used Mozambican wood species known as messassas (Brachystegia spiciformis and Julbernardia globiflora) aiming at edge-glued panel production. The bonding was performed using structural adhesive polyvinyl acetate D4, semi-structural adhesive emulsion polymer isocyanate and non-structural polyvinyl acetate D3 applied at 120·m-2 and 180·m-2 weights. Density, chemistry, edge shear bonding, wood failure percentage and the finger-joint tests were performed in accordance with ISO 13061-2:2014 (E), TAPPI, EN 13354:2008, ABNT-NBR ISO 12466-1:2006 and ASTM 5572:2005 standards, respectively. The results showed that both species have medium density, high extractives and lignin contents typical of tropical wood. The emulsion polymer isocyanate adhesive was approved with better performance compared to polyvinyl acetate D3 and D4 adhesives. It can also be affirmed that Brachystegia spiciformis and Julbernardia globiflora have similar bonding behaviour and the potential for producing edge glued panel panels, especially for indoor use
Biochemical features of organic extractives from Eucalyptus and Corymbia woods using ethanol as a solvent
Get PDFThe objective of this study is to evaluate chemical characteristics, as well as antioxidant and antibacterial activities of organic compounds extracted from three Eucalyptus woods and Corymbia maculate wood using ethanol as a solvent. To obtain the ethanolic extracts, 15 g of a powdered wood sample was mixed with 150 mL of ethyl alcohol 99 % PA by constant mechanical stirring, which was further magnetically mixed at 60 ºC for 24 h. The extractives were analyzed by means of percent yield, Fourier-transform infrared spectrum, inhibitory index (measured after antimicrobial tests), antioxidant activity, and condensed tannins content. The Eucalyptus dunnii extract showed the highest percent yield. The infrared spectra of all the extractives presented similar profiles, with remarkable bands ascribed to the presence of lipophilic extracts, sterols, fatty acids, and other hydroxylated substances, such as carbohydrates and phenolic compounds. In all cases, the higher the concentration of the extractive was, the higher the antioxidant activity was. The antioxidant activity of Eucalyptus saligna extract stood out since overcame that of the positive control (ascorbic acid). Regarding the condensed tannins content, that extract from Eucalyptus grandis excelled
Spatial and aspatial indicators: a complementary approach to the quantitative analysis of residential segregation in Managua
Get PDFEl polimorfismo de su concepto y la complejidad de sus múltiples dimensiones espaciales, hacen de la medición de la segregación un tema desafiante. A través de los años se han desarrollado enfoques metodológicos que han producido diversos indicadores para cuantificar el fenómeno. Por un lado, se hallan los indicadores tradicionales, criticados por las fallas que se les aducen, entre las que destaca su incapacidad para revelar la forma en que se distribuye espacialmente el fenómeno. Y, por otro lado, se encuentran los indicadores espaciales, creados a partir del desarrollo de la estadística espacial y la disponibilidad de softwares de Sistemas de Información Geográfica (SIG), a los cuales se les adjudica superioridad conceptual y operacional. Esto ha empujado a algunos investigadores latinoamericanos a proponer el abandono del uso de los indicadores tradicionales y recurrir exclusivamente a los indicadores considerados espaciales. No obstante, a través de este artículo se muestra cómo, desde un enfoque complementario, los indicadores espaciales y no espaciales pueden articularse para revelar las distintas dimensiones espaciales de la segregación residencial, y así disminuir las arbitrariedades en su medición, representación e interpretación, a la vez que se atiende la limitada disponibilidad de datos espaciales individuales que caracteriza a Latinoamérica. Los resultados del estudio de la segregación residencial socioeconómica de la ciudad de Managua, a través del Índice de Disimilitud y el Índice de Moran Global, exhiben que Managua se caracteriza por una segregación a pequeña escala y que el grupo más segregado, en términos de concentración y agrupamiento, es la población con estudios universitarios completos. Asimismo, demuestran que, si bien los indicadores espaciales buscan capturar la naturaleza inherentemente geográfica de la segregación residencial, su exclusiva utilización falla en atender la multidimensionalidad espacial del fenómeno y puede conducir a vacíos en su cuantificación.The polymorphism of its concept, as well as the complexity of its multiple spatial dimensions, make the measurement of segregation a challenging subject. Which is why, over the years, methodological approaches have been developed, which have produced different indicators to quantify the phenomenon. On the one hand, there are the traditional indicators, which have been criticized for the flaws attributed to them, among which their inability to reveal the way in which the phenomenon is spatially distributed stands out. On the other hand, there are spatial indicators, created from the development of spatial statistics and the availability of Geographic Information System (GIS) software, which are believed to be conceptually and operationally superior. This has led some Latin American researchers to propose abandoning the use of traditional indicators altogether, and to exclusively use the indicators considered as spatial. However, this article shows how, from a complementary approach, spatial and aspatial indicators can be articulated to reveal the different spatial dimensions of residential segregation, and thus reduce arbitrariness in their measurement, representation, and interpretation. While, at the same time, it addresses the limited availability of individual spatial data that characterizes Latin America. The results of the study of socioeconomic residential segregation in Managua, through the Dissimilarity Index and the Global Moran´s Index, show that the city exhibits small-scale segregation, and that the most segregated group in terms of concentration and grouping is the population with a college degree. It also reveals that although spatial indicators seek to capture the inherently geographical nature of residential segregation, their exclusive use fails to address the spatial multidimensionality of the phenomenon and can lead to gaps in its quantification
Vivienda para estudiantes indígenas: permanencia, representatividad y proceso de diseño participativo
Get PDFEste artigo apresenta o processo de projeto adotado para a concepção da moradia estudantil indígena na Universidade Federal de Santa Catarina – Brasil e discute seus impactos tanto no processo formativo dos estudantes de arquitetura e urbanismo quanto nas vivências dos estudantes indígenas na universidade. Além da relevância dessa arquitetura como suporte à permanência dos estudantes no ensino superior público, destaca-se sua importância como símbolo de acolhimento e respeito aos povos indígenas na universidade. Para tanto foi construído um percurso projetual participativo que iniciou com etapas de diálogos com os estudantes indígenas na universidade e interações com uma das etnias envolvidas em seu território tradicional (a Aldeia) para definição das diretrizes projetuais e programa de necessidades. Posteriormente, para a apresentação e discussão da proposta, foram realizadas vivências na área proposta para a implantação do projeto e apresentação de maquetes físicas e desenhos utilizados para facilitar o diálogo e a participação dos estudantes indígenas no processo de projeto. O artigo apresenta o percurso trilhado, os resultados espaciais desse processo, as percepções dos futuros usuários do espaço e reflexões acerca da importância de ações de extensão na formação de profissionais da área de arquitetura e urbanismo, valorizando o papel social da profissão e construindo um repertório projetivo mais sensível e preparado para considerar a diversidade humana que constitui a contemporaneidade.This article presents the project process adopted for the design of indigenous student housing at the Federal University of Santa Catarina, Brazil, and discusses its impact both on the formative process of architecture and urbanism students, regarding the experiences of indigenous students at the University. Aside from the relevance of that architecture as support for the permanence of students in public higher education, its importance as a symbol of shelter and respect for indigenous peoples at the university stands out. For this purpose, a participatory project was built that began with dialogues stages with indigenous students at the university and interactions with one of the ethnicities involved in its traditional territory (its village), for the definition of project guidelines and the needs’ program. Subsequently, for the proposal’s presentation and discussion, experiences were gathered in the proposed area for the project’s implementation and the physical models and drawings were presented, which were used to facilitate dialogue and participation of Indigenous students in the project process. The article presents the path followed, the spatial results of this process, the perceptions of the future users of the space, and reflections on the importance of outreach actions in the training of professionals in the area of architecture and urbanism, valuing the social role of the profession, and building a more sensitive projective repertoire, prepared to consider the human diversity that contemporaneity constitutes.Este artículo presenta el proceso de diseño adoptado para el diseño de viviendas indígenas en la Universidad Federal de Santa Catarina - Brasil y analiza sus impactos tanto en el proceso educativo de los estudiantes de arquitectura y urbanismo como en las experiencias de los estudiantes indígenas en la universidad. Además de la relevancia de esta arquitectura como soporte para la permanencia de los estudiantes en la educación superior pública, se destaca su importancia como símbolo de aceptación y respeto a los pueblos indígenas en la universidad. Para ello, se construyó una ruta de diseño participativo, que comenzó con etapas de diálogo con estudiantes indígenas de la universidad e interacciones con una de las etnias involucradas en su territorio tradicional (la Aldea) para definir lineamientos de diseño y necesidades del programa. Posteriormente, para la presentación y discusión de la propuesta, se llevaron a cabo experiencias en la zona propuesta para la ejecución del proyecto y la presentación de modelos físicos y dibujos utilizados para facilitar el diálogo y la participación de los estudiantes indígenas en el proceso de diseño. El artículo presenta el camino recorrido, los resultados espaciales de este proceso, las percepciones de los futuros usuarios del espacio y reflexiones sobre la importancia de las acciones de extensión en la formación de profesionales en el campo de la arquitectura y el urbanismo, valorando el rol social de la profesión y la edificación. un repertorio proyectivo más sensible y preparado para considerar la diversidad humana que constituye la contemporaneidad
Advances in digital economy some latin american countries
Get PDFLas actuales condiciones del mercado exigen que las compañías adopten nuevos modelos de negocios bajo los factores que aumentan la productividad como la innovación tecnológica, adopción del e-commerce, entre otras herramientas del marketing digital, enfocadas hacia la competitividad de pymes que incluya una gestión digital de las relaciones con el cliente.
El presente estudio se realizó con el propósito de realizar una revisión en temáticas y tendencias del ecosistema digital en la región latinoamericana, y su impacto en la aplicación de estrategias de innovación en los nuevos modelos de negocios, ecosistema de digital que le permita a la Pymes en el mediano y largo plazo la toma de decisiones en cuanto a comercio electrónico, desarrollo de habilidades para la transformación digital. La metodología utilizada se basó en una investigación descriptiva con método de la Norma UNE 166006:2006. Se analizaron aspectos del desarrollo de las TIC. Se evidenció que el grado de adopción del comercio electrónico difiere entre los países de la región, políticas públicas en la economía digital.The current market conditions demand that companies adopt new business models under factors that increase productivity such as technological innovation, adoption of electronic commerce, other digital marketing tools, focused on the competitiveness of SMEs that affect digital management of customer relationships.
The present study was carried out with the purpose of conducting a review on issues and trends of the digital ecosystem in the Latin American region, and its impact on the application of innovation strategies in new business models, a digital ecosystem that will allow SMEs in the medium and long term, decision-making regarding electronic commerce, skills development for digital transformation. The methodology used was based on quantitative research using the UNE 166006: 2006 method. Aspects of ICT development were analyzed. It is evident that the degree of adoption of electronic commerce differs between the countries of the region, public policies in the digital economy
Attitude and motivation in professional training students
Get PDFLa consideración socio-académica y laboral de la Formación Profesional en las últimas décadas, ha supuesto un cambio importante de modelo, tanto en el mundo educativo como en el laboral, necesitados de una transformación sustancial para el afrontamiento de nuevos retos. Dentro de este contexto y a nivel educativo, el objetivo del presente trabajo, ha sido la descripción y explicación de las variables intervinientes en la motivación, a fin de determinar los elementos motivacionales en el proceso enseñanza-aprendizaje para la formación de los futuros profesionales. Para tal fin se ha realizado el estudio utilizando 103 participantes de dos Centros de Formación Profesional y en los tres niveles: Ciclo de Formación Profesional Básica, Ciclo Formativo de Grado Medio y Ciclo Formativo de Grado Superior. Los resultados han manifestado la influencia que las “necesidades” y los “conflictos” producidos por dichas necesidades han sido los elementos determinantes de la Motivación, más allá de la “satisfacción” del aprendizaje. Se ha pretendido aportar información para posibles intervenciones en el ámbito metodológico y curricular en la formación de los futuros profesionales del mundo laboral.The socio-academic and labor consideration of Vocational Training in recent decades has led to an important change in the model, both in the educational world and in the workplace, in need of a substantial transformation to face new challenges. Within this context and at the educational level, the objective of this work has been the description and explanation of the variables involved in motivation, in order to determine the motivational elements in the teaching-learning process for the training of future professionals. For this purpose, the study has been carried out using 103 participants from two Vocational Training Centers and at the three levels: Basic Vocational Training Cycle, Middle Grade Training Cycle and Higher-Grade Training Cycle. The results have shown the influence that the “needs” and the “conflicts” produced by those needs, have been the determining elements of Motivation, beyond the “satisfaction” of learning. It has been intended to provide information for possible interventions in the methodological and curricular field in the training of future professionals in the labor world
Culture and organizational performance: contrasts between high and low simce’ score in Ñuble Highscools
Get PDFThe purpose of this research is to analyze the culture and organizational performance of municipal schools in the, recently created, Ñuble county, Chile. Within these schools, a distinction between municipal schools will be made, those in the top 25% and those in the bottom 25% of SIMCE test results in the last 5 years. Two schools are analyzed, one in Chillán and the other one in San Nicolás, considering 80 teachers in total. In both cases, the characteristics of the organizational culture, established by the Denison model, are analyzed, through a quantitative comparative study between the sub-dimensions involvement, consistency, adaptability, and mission, as well as an analysis of the organizational performance perceived by its members. Based on the results obtained, it is observed that both schools have a perception of organizational performance focused on flexibility and stability; In addition, significant differences are obtained in some dimensions, where one of the schools has a more developed perception of culture in contrast to the other. It is concluded that more studies should be carried out on the evaluation of teachers and the school organization as a whole, for education.La presente investigación tiene como propósito analizar la cultura y desempeño organizacional de los establecimientos municipales de la nueva región de Ñuble. Dentro de estos, se hará una distinción entre los establecimientos municipales entre el 25% superior y el 25% inferior de resultados SIMCE en los últimos 5 años en Ñuble. Se analizan dos establecimientos, uno en Chillán y otro en San Nicolás, considerando 80 docentes en total. En los dos establecimientos se analizan los rasgos de la cultura organizacional, establecidos por el modelo de Denison a través de un estudio comparativo cuantitativo entre las subdimensiones involucramiento, consistencia, adaptabilidad y misión, así como también un análisis sobre el desempeño organizacional percibido por sus integrantes. Entre los resultados obtenidos se puede observar que ambos establecimientos poseen una percepción de desempeño organizacional centrado en la flexibilidad y estabilidad; se obtiene, además, diferencias significativas en algunas dimensiones, donde uno de los establecimientos posee una percepción de cultura más desarrollada en contraste con el otro. Se concluye que se deben realizar más estudios sobre la valoración de los docentes y la organización escolar como un todo, para la educación