Revistas Universidad del Bío-Bío
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Formaldehyde free tannin-based adhesive with epoxy as hardener for plywood
Get PDFA renewable tannin-based resin adhesive with enhanced bonding strength, good water resistance and long storage life has been prepared based on tannin, furfural and furfuryl alcohol coming from forest and agricultural products. Fourier transform infrared spectroscopy (FT-IR), Electrospray ionization mass spectroscopy (ESI-MS) and Differential scanning calorimetry (DSC) indicated that furfuryl alcohol and furfural can react with tannin under acidic conditions, with the involvement of –CH2–O– groups in the cross-linking of tannin-furfuryl alcohol-furfural resin (TFF) adhesive. The gel time of TFF was longer than that of tannin-furfural resin (TF), while the shear strength of TFF-bonded plywood suggested that the cured TFF adhesive acquired a performance superior to that of tannin (T) and TF adhesives. Furthermore, water resistance of TFF adhesive could be further enhanced with respect to T and TF adhesives through cross-linking with 3 % epoxy resin (EPR)
Investigations on the sorption behaviour of selected wood species from cameroon
Get PDFThe sorption isotherms during adsorption and desorption of 25 wood species from Cameroon (included 3 species from plantation in Togo) were determined. In addition, the chemical compositions of these wood species were tested. The equilibrium moisture contents in a normal climate varied between 10,55 % and 15,6 %. A clear influence of the proportion of extractives can be seen. The maximum differences between adsorption and desorption varied between 2,3 % and 3,6 %
Matemática para jóvenes con Síndrome de Asperger en la Educación Secundaria. Análisis bibliométrico (2010 – 2021)
Get PDFEsta investigación está orientada al ámbito bibliométrico aportando información cuantitativa y necesaria sobre el síndrome de Asperger entendido como trastorno del desarrollo que lleva asociada una alteración neurobiológica la cual manifiesta un conjunto de características mentales y conductuales que forman parte de los trastornos del espectro autista (TEA). El objetivo del trabajo fue analizar líneas temáticas y las estrategias para el proceso de enseñanza y aprendizaje de las matemáticas de los alumnos con síndrome de asperger en la educación secundaria. La búsqueda fue realizada en las bases de datos Web of Science, Scopus y Scielo, se hizo en base a 11 trabajos que cumplieron los criterios de inclusión señalada en la estrategia de búsqueda. Los resultados indican un aumento de los trabajos en los últimos años y una alta valoración de las metodologías para la enseñanza de la matemática en el estudiantado con síndrome de Asperger. Las principales conclusiones permiten afirmar que, pese al escaso número de trabajos sobre esta temática, existe una clara preocupación por la inclusión de este grupo de personas en el ámbito escolar.This research is oriented to the bibliometric field providing quantitative and necessary information on the Asperger syndrome understood as a developmental disorder associated with a neurobiological alteration which manifests a set of mental and behavioral characteristics that are part of the autism spectrum disorders (ASD). The objective of the work was to analyze thematic lines and strategies for the teaching and learning process of mathematics of students with Asperger syndrome in secondary education. The search was conducted in the Web of Science, Scopus and Scielo databases, based on 11 papers that met the inclusion criteria indicated in the search strategy. The results indicate an increase in the number of papers in recent years and a high evaluation of methodologies for teaching mathematics to students with Asperger syndrome. The main conclusions allow affirming that, in spite of the scarce number of works on this subject, there is a clear concern for the inclusion of this group of people in the school environment
Booktube como recurso pedagógico para el aprendizaje en la Educación Superior
Get PDFThe current society has experienced a series of changes and technological transformations, which at the educational level, are a challenge for teachers, who interact with young digital natives, more accustomed to use these technological advances in their daily activities and study and learning processes. The present work aims to identify the contribution of the booktube, as a pedagogical resource that promotes learning and emotional development, in the subject of Educational Guidance at the Universidad del Bío-Bío. An educational experience, that contemplated the use of booktube, was designed and implemented with third year Primary Education Teaching students. Specifically, 50 students who are taking the subject of Educational Guidance. At the end of the course, a perception questionnaire was applied. The results indicate a positive evaluation by the students, with averages per item ranging from 4.02 to 4.68 (out of a maximum of 5 points), the indicators with the highest average were "improving oral expression competence" and "acquiring a didactic tool for the emotional development of my future students". On a small scale, these results evidence the learning potential provided by technologies, when their use is intended to support a formal learning process.La sociedad actual ha experimentado una serie cambios y transformaciones tecnológicas, que a nivel educativo son un desafío para los docentes, que interactúan con jóvenes, nativos digitales, más habituados a usar estos avances tecnológicos en sus actividades diarias, estudio y aprendizaje. El presente trabajo tiene como objetivo identificar el aporte del booktube, como recurso pedagógico que promueve el aprendizaje y desarrollo emocional, en la asignatura de Orientación Educacional de la Universidad del Bío-Bío. Se diseñó e implementó una experiencia educativa que contempló el uso de booktube, dirigido al tercer año de la carrera de Pedagogía en Educación Básica, concretamente a 50 estudiantes que cursan la asignatura de Orientación Educacional y al finalizar se aplicó un cuestionario de percepción. Los resultados indican una valoración positiva de los estudiantes, con promedios por ítems que oscilan entre 4,02 y 4,68 (sobre un máximo de 5 puntos), los indicadores con mayor promedio fueron “mejorar la competencia de la expresión oral” y “adquirir una herramienta didáctica para el desarrollo emocional de mis futuros estudiantes”. Estos resultados son una evidencia, a menor escala, del potencial de aprendizaje que brindan las tecnologías al intencionar su utilización en un proceso de aprendizaje formal
Preliminary evaluation of the incorporation of cellulose nanofibers as reinforcement in waterborne wood coatings
Get PDFThe wood is exposed to possible damages caused by weather, requiring the application of a finishing coat to provide extra protection. The aim of this work was to evaluate the influence of the addition of microfibrillated cellulose in waterborne varnish on the colorimetric parameters, wettability and finish characteristics of wood products. Color was evaluated with a CM-5 spectrophotometer; surface wettability was analyzed by contact angle measurement using a drop shape analysis goniometer; and abrasion, adhesion and impact tests were performed to evaluate the quality of the coating. The coating’s optical characteristics were not affected by the addition of microfibrillated cellulose. The changes in wood wettability were small, with no statistical difference between the wood treated with plain varnish and that with unbleached microfibrillated cellulose. In the analysis of the variation of the contact angle during the elapsed time, the coating containing unbleached microfibrillated cellulose presented the best results. The results of finish quality did not show numerical changes after the addition of the microfibrillated cellulose, but qualitatively the microfibrillated cellulose caused better anchoring of the coating to the specimens. Therefore, the use of microfibrillated cellulose as reinforcement in coatings has potential, but tests with different consistencies and tests of other properties are necessary
Modelling the influence of radiata pine log variables on structural lumber production
Get PDFWe run logit models to explain the variability of Pinus radiata structural lumber in 71 second and third unpruned logs. The response variable was the proportion of lumber with a static modulus of elasticity greater or equal than 8 GPa, pMSG8+, and the explanatory variables were log volume, branch index, largest branch, log internode index, wood basic density, and acoustic velocity. The average pMSG8+ volume was 44,30 % and 36,18 % in the second and third log respectively. Ten models were selected based on meeting statistical assumptions, their goodness of fit, and the statistical significance of their parameters. The best models (R2 - adj. > 0,75) included acoustic velocity (AV) as explanatory variable, which explained 56,25 % of the variability of pMSG8+. Models without AV presented goodness of fit ranging from 0,60 to 0,75 (R2 - adj.), and variables with the highest weight to explain the variability of pMSG8+ were volume, followed by wood basic density, branch index, and largest branch. It is possible to model pMSG8+ from log variables even when acoustic velocity is not available; however, this requires wood basic density models calibrated for the Pinus radiata growing zone
La redensificación urbana de la Ciudad de México y el COVID 19
Get PDFPublic policies such as urban redensification, rather than mere technical interventions addressing concrete problems, work as a power mechanism. Analyzing the visibility of the politics of life - biopolitics - and of death - necropolitics - in Mexico City derived from the COVID-19 pandemic will allow an understanding of this. In addition, it will allow revealing the paradox that the same policy, redensification, is a failure as a public policy and, simultaneously, a success as a policy of life and death. Starting from sociology and based on a genealogical methodology, data on the effects of urban redensification and the pandemic in Mexico City were analyzed, to subsequently intertwine them and recognize a relationship between them. Special attention was paid to the period of non-compulsory confinement and two neighboring districts of Mexico City: Iztapalapa and Benito Juárez. Thus recognizing a class configuration of space linked to urban design that influenced the localized consequences of the pandemic.Políticas públicas como la redensificación urbana, antes que meras intervenciones técnicas ante problemas concretos, funcionan como mecanismos de poder. Analizar la visibilización de las políticas de vida –biopolítica– y de muerte –necropolítica– en la Ciudad de México derivada de la pandemia del COVID-19, permitirá comprender esta función. Además, dará cuenta de la paradoja de que una misma política, la redensificación, sea un fracaso como política pública y simultáneamente un éxito como política de vida y de muerte. A partir de la sociología y con base en una metodología genealógica, se estudian datos relativos a los efectos de la redensificación urbana y de la pandemia en la Ciudad de México, para entrecruzarlos y reconocer una relación entre ambos. Se presta especial atención al periodo de confinamiento no obligatorio y a dos demarcaciones colindantes de la Ciudad de México: Iztapalapa y Benito Juárez. Se reconoce así una configuración de clase del espacio ligada a la planificación urbana que incidió en las consecuencias localizadas de la pandemia
Planificación de la franja urbano rural de Santa Eufemia, Córdoba, Argentina
Get PDFEl objetivo de este artículo es mostrar cómo diseñar y evaluar la visión estratégica territorial de la Franja Urbano Rural (FUR) en la localidad de Santa Eufemia, Córdoba, Argentina. La metodología se basa en un procedimiento multicriterio por fases dirigido al gobierno municipal y los actores que éste involucró. En la fase 1, se identificaron los problemas (oportunidades) y aspiraciones locales mediante entrevistas en profundidad. En la fase 2, se diseñó y valoró un menú de alternativas para dos decisiones estratégicas que emergen de las entrevistas: la regulación hídrica (desagües) y la provisión de alimentos de proximidad. En la fase 3, se relevaron las preferencias de los actores y se evaluaron las alternativas mediante el algoritmo Promethee. Las alternativas elegidas fueron incluidas a la visión de FUR y complementan tres decisiones estructurales (localización de un parque industrial, poblamiento urbano futuro y gestión de residuos). Comparada con las prognosis, dichas alternativas presentan mejor performance, aunque se reconocen algunas limitaciones. Una de ellas reduce 50% los escurrimientos hídricos que potencialmente afectarían a la localidad y otra incrementa la producción de alimentos de proximidad 27%, genera excedentes económicos (12 puestos de trabajo) y minimiza significativamente los riesgos de enfermedades zoonóticas y de contaminación por agroquímicos. Ahora bien, las alternativas requieren más inversiones y un esfuerzo político institucional mayor que la prognosis. Por último, los actores valoraron las alternativas diseñadas junto a las tres dimensiones de la sostenibilidad (criterios de comparación) y acordaron avanzar en una decisión de compromiso sobre la visión de FUR.This article seeks to show how to design and evaluate the territorial strategic vision of the Rural-Urban Fringe (RUF) in Santa Eufemia, Córdoba, Argentina. The methodology is based on a multi-phase multi-criteria procedure for the municipal government and the actors involved. In phase 1, local problems (opportunities) and aspirations were identified through in-depth interviews. In phase 2, a menu of alternatives was designed and assessed for two strategic decisions that emerged within the interviews, namely, rainwater drainage and local food provision. In phase 3, the actors’ preferences were revealed, and the alternatives were evaluated using the Promethee algorithm. The chosen alternatives were included in the RUF vision and complemented three structural decisions (location of an industrial park, future urban settlements, and waste management). Compared with the prognosis, the alternatives chosen, have a better performance, although some limitations are recognized. One of the alternatives reduces the water runoff that could potentially affect the locality by 50%. Another alternative increases local food production by 27%, generating an economic surplus (12 jobs) and significantly minimizing the risks of zoonotic diseases and agrochemical contamination. However, the alternatives require more investment and an increased institutional political effort than in the prognosis. Finally, the actors appreciated the alternatives designed with the three sustainability dimensions (comparison criteria) and agreed to move forward on a compromise decision about the RUF vision