Revistas Universidad del Bío-Bío
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Mechanıcal and fıre propertıes of orıental beech ımpregnated wıth fıre-retardants and coated wıth polyurea/polyurethane hybrıd and epoxy resıns
Get PDFThis study was performed to investigate some mechanical properties such as modulus of rupture and compression strength parallel to grain and some fire properties such as weight loss and temperature values of Oriental beech (Fagus orientalis) treated with fire-retardants and coated with polyurethane/polyurea hybrid resin and epoxy resin were investigated. The coatings are based on epoxy and polyurethane\polyurea hybrid resins. Firstly, an impregnation method was applied by using fire-retardants which are boron chemicals and ammonium sulfate before coating process. Oriental beech was impregnated with 3 % aqueous solution of boric acid, borax, boric acid and borax mixture (1:1), and ammonium sulfate. Oriental beech was primed with epoxy resin by using Sikafloor®-156, and then coated with Sikalastic®-851, a polyurethane/polyurea hybrid resin. Results showed that modulus of rupture and compression strength parallel to grain values of polyurethane/polyurea and epoxy resin coated Oriental beech wood were higher than that of un-treated and non-coated (control) group. Fire-retardants treatment before polyurethane/polyurea and epoxy resin coatings caused to decrease modulus of rupture and compression strength parallel to grain values of Oriental beech in some extent. Weight loss and temprature values of polyurethane/polyurea and epoxy resin coated Oriental beech were higher than that of un-treated and non-coated (control) group. Hovewer, fire-retardants treatment before polyurethane/polyurea and epoxy resin coatings improved fire properties of Oriental beech wood
Prediction of surface roughness of CO2 laser modified poplar wood via response surface methodology
Get PDFDue to the advantages of short treatment period, no wastewater and oil produced, the CO2 laser is applied as an environment friendly thermal treatment for wood materials to improve the wood properties, such as appearance, color and wettability, etc. However, the morphological features of treated wood surface are also changed, which have negative effects on wooden product properties. To reveal the change tendency of surface roughness during laser irradiation, the common indexes of average roughness (Ra) and mean peak-to-valley height (Rz) were chosen to evaluate the surface roughness. The response surface methodology was selected to arrange the experiments and analyze the influences of laser parameters on surface roughness. The results showed that the poplar wood got rougher with the increased laser power, but the surface roughness decreased with increased feed speed and path spacing, due to the total heat absorption varied under different combination of laser parameters. The ANOVA results showed that the selected quadratic models for Ra∥, Rz∥, Ra⊥ and Rz⊥were significant due to the values of probability value (“Prob>F”) less than 0,05. In this case, all the input laser parameters were also the significant model terms for variation of surface roughness. The values of correlation coefficient were very close to 1, which meant the selected quadratic models could give accurate prediction of surface roughness for laser treated wood. Therefore, it is of great significance to predict the surface roughness of the modified wood surface scientifically and to guide the selection of reasonable modification process parameters
Exploratory studies on effects of growth location and conditioning on treatability and permeability of southern pine lumber
Get PDFSouthern pine lumber is often treated with preservatives, but issues related to initial kiln-drying conditions and geographic source across the wide southern pine growth range have been suspected to negatively affect subsequent permeability and treatability. These effects remain poorly understood. In this series of exploratory studies, southern pine from across part of the growing range subjected to different kiln-drying regimes was evaluated in three phases exploring the effects of geographic source and initial kiln-drying conditions on permeability, pit structure and eventual preservative treatment of southern pine lumber. The results suggest that elevated temperatures coupled with poor humidity control at the start of the kiln drying process may negatively influence permeability and preservative penetration, but had only negligible effects on several other wood properties
Optimización multiobjetivo de la eficiencia energética y el confort térmico en edificios de oficina públicos. Periodo crítico de verano en la ciudad de San Juan, Argentina
Get PDFEl 40% de la demanda mundial de energía y de emisiones de CO2 proviene de las edificaciones. En Argentina, los edificios son también responsables del 40% del consumo total anual de energía. El problema radica en el desequilibrio provocado entre la necesidad de proveer de una elevada calidad de vida y confort a los espacios de oficina y el costo de energía requerido para acudir a tal propósito. Tanto un alto nivel de confort como el ahorro energético representan dos objetivos a alcanzar. En ese sentido, este artículo propone una nueva metodología que combina la medición in situ con herramientas de simulación matemática. Se incorporan técnicas y modelos innovadores para la elaboración de la herramienta aplicando una optimización multiobjetivo termo-energética, que opera dinámicamente durante el horario laboral. Los resultados muestran un importante ahorro en el consumo energético para refrigeración de espacios de oficinas en verano (del 57,5% al 83,3%), junto con un aumento en la calidad del confort térmico de entre el 4,7% y el 29,4%.Buildings represent 40% of the world's energy demand and CO2 emissions. In Argentina, buildings are responsible for 40% of the total annual energy consumption. The problem lies in an imbalance between the need to provide a high quality of life and comfort in office spaces, and the high energy cost required to meet that goal. Both a high comfort level and energy savings represent two objectives to be achieved. In this sense, this paper proposes a new methodology that combines onsite measurement with mathematical simulation tools. Innovative techniques and models are incorporated to make the tool, applying thermal-energy multi-objective optimization, which operates dynamically during working hours. The results show significant savings in energy consumption regarding cooling office spaces in the summer, from 57.5% to 83.3%, together with an increase in the thermal comfort quality, with improvements between 4.7% and 29.4%
Hacia un proyecto educativo centrado en las comunidades
Get PDFDesde la “municipalización” del sistema educativo chileno en la década de los 80´, ha existido una tendiente centralización de las decisiones educativas en diversos organismos que se posicionan lejos del contexto real en que los centros educativos se desarrollan, y que han generado un alejamiento de las comunidades hacia dichos centros. El predominio de sistemas educativos homogeneizantes y centralizados se han transforman en decisiones comunes en los diversos gobiernos que han legislado sobre educación, y han invisibilizado el valor real de la comunidad en el proceso formativo. Es por ello que resulta importante una reflexión sobre los dispositivos que puedan incluir en las decisiones educativas a los contextos. Aquí resurge el valor emancipador de los proyectos centrados en las comunidades, desde donde el dialogo consiente, reflexivo y que se centre en la participación democrática de sus actores, se transforma en el dispositivo faltante para la emancipación de la educación centralizada.Since the “municipalization”1 of the Chilean educational system in the 1980s, there has been a tendency to centralize educational decisions in various organizations that are positioned far from the real context in which educational centers are developed, and which have generated a distancing from the communities to these centers. The predominance of homogenizing and centralized educational systems have been transformed into common decisions in the various governments that have legislated on education, and have made invisible the real value of the community in the training process. For this reason, it is important to reflect on the mechanisms that contexts can include in educational decisions. Here, the emancipatory value of community-focused projects resurfaces, from which the conscious and reflective dialogue which focuses on the democratic participation of its actors, becomes the missing mechanism for the emancipation of centralized education
Effect of microwave treatment on drying and water impregnability of Pinus pinaster and Eucalyptus globulus
Get PDFWood is a material that has been used by humankind for a long time. However, wood researchers and industry have always been concerned about the issues during wood drying and the permeability problems of certain species. In this sense, microwave technology has been applied for wood drying and improving permeably. This paper investigates the microwave drying of two Portuguese wood species, Pinus pinaster sap and heartwood and Eucalyptus globulus heartwood using small clear specimens. The samples were grouped into six during each microwave treatment run according to their similarity of initial moisture content. Once the drying was completed, control and microwave -treated samples were impregnated with desalinated water to analyze their improvement in water absorption, and the compression strength parallel to the grain was analyzed. The results showed that each wood species behaves differently under microwave drying and initial moisture content. The impregnation results demonstrated that pine and eucalyptus microwave -treated heartwood samples improved their capability to absorb water. Finally, only the microwave -treated specimens of eucalyptus heartwood presented a decrease in the values of compression strength parallel to the grain compared to the control group. Therefore, MW treatment presents possibilities for further applications for the wood industry with supporting results
Las intervenciones en el Palacio de La Moneda de los siglos XIX, XX y XXI. Los proyectos y sus arquitectos
Get PDFO Palácio de La Moneda é a sede da presidência e do poder executivo do Chile, do Ministério do Interior e Segurança Pública, da Secretaria-Geral da Presidência e da Secretaria-Geral de Governo. Constitui-se como um dos principais edifícios históricos do Chile e o mais importante no que diz respeito à sua função representativa atual, já que é o palácio de governo. Desde a sua origem, em 1786, o edifício foi testemunha e protagonista da evolução histórico-política e sócio-urbana da nação, de fatos que se traduziram em sua própria metamorfose arquitetônica e na evolução do entorno urbano. Projetado pelo arquiteto Joaquín Toesca, discípulo de Francesco Sabatini, discípulo de Francesco Sabatini e profissional da corte de Carlos III, Rei da Espanha (1759-1788), o Palácio é a principal obra do Neoclassicismo no Chile, inaugurada em 1805 como Real Casa da Moeda de Santiago para a cunhagem da circulação monetária do reino. Após a independência do Chile, em 1845, a sede do governo e a residência presidencial foram transferidas ao Palácio. É nesta data que adota sua função representativa e, portanto, o momento em que se estabelece a primeira modificação importante do seu plano, dando início a um processo de evolução contínua que se caracterizará pela transformação dinâmica e adaptação permanente de sua arquitetura, mediante sucessivas intervenções, atualizações funcionais e sua reconstrução após o bombardeio de 1973. A falta de um registro sistemático e detalhado das permanentes alterações dificulta sua compreensão em seu estado atual e levando em consideração possíveis intervenções futuras. Por este motivo, no presente texto procedemos à exposição daquelas de maior alcance e de caráter significativo para a percepção do edifício, com o intuito de estabelecer um primeiro registo sistemático de intervenções contemporâneas no Palácio de La Moneda.
The Palacio de La Moneda, or La Moneda Palace, is the seat of the Presidency and the Executive Power of Chile, the Ministry of the Interior and Public Security, the General Secretariat of the Presidency, and the General Secretariat of the Government. It is one of the main historical and most important buildings in Chile in terms of its current representative function, as the Government Palace. Since its construction, in 1786, it has been the witness and star of the historical-political and social-urban evolution of the nation, of events that have been expressed in its own architectural metamorphosis and the evolution of the urban fabric. Designed by architect Joaquín Toesca, a disciple of Francesco Sabatini, a professional of the court of Carlos III, King of Spain (1759-1788), the Palace is the main example of Neoclassicism in Chile. It was inaugurated in 1805 as the Royal Mint of Santiago, to mint the kingdom's currency. After the independence of Chile, in 1845, the Seat of Government and Presidential Residence moved to the building. It is on this date that it adopts its representative function, and therefore, the moment where the first important modification of its floorplan took place, beginning a process of continuous evolution characterized by the dynamic transformation and permanent adaptation of its architecture, through successive interventions, functional updates, and its reconstruction after the 1973 air raid. The lack of an organized and detailed record of its permanent alterations makes it difficult to understand them from their current state and for possible future interventions. As a result, this article presents the most important and significant changes on the perception of the building, thus becoming the first organized record of contemporary interventions of La Moneda Palace.El Palacio de La Moneda es la sede de la presidencia y del poder ejecutivo de Chile, del Ministerio del Interior y Seguridad Pública, la Secretaría General de la Presidencia y la Secretaría General de Gobierno. Se constituye como uno de los principales edificios históricos de Chile y el más importante en cuanto a su función representativa actual, ser el palacio de gobierno. Desde su origen, en 1786, el edificio ha sido testigo y protagonista del recorrido histórico-político y social-urbano de la nación, de hechos que se han expresado en su propia metamorfosis arquitectónica y en la evolución del entorno urbano. Diseñado por el arquitecto Joaquín Toesca, discípulo de Francesco Sabatini y profesional de la corte de Carlos III, Rey de España (1759-1788), el Palacio es la principal obra del Neoclasicismo en Chile, la que fue inaugurada en 1805 como Real Casa de Moneda de Santiago para la acuñación de los caudales del reino. Luego de la independencia de Chile, en 1845, se traslada al inmueble la sede de gobierno y residencia presidencial. Es en esta fecha cuando adopta su función representativa y, por consiguiente, cuando se establece la primera modificación importante de su planta, con la cual comienza una dinámica transformadora y de adaptación permanente de su arquitectura, a través de intervenciones sucesivas, actualizaciones funcionales y su reconstrucción tras el bombardeo de 1973. La falta de un registro ordenado y detallado de las permanentes alteraciones, dificulta su comprensión desde su actual estado y hacia futuras intervenciones posibles. Por lo referido, en el presente escrito se procede a la exposición de aquellas de mayor envergadura y carácter significativo para la percepción del edificio, a fin de configurar un primer registro ordenado de intervenciones contemporáneas del Palacio de La Moneda
Transformar mentalidades en centros formadores de docentes: Vía para emprender las reformas educativas. Experiencia en países de Latinoamérica
Get PDFLa experiencia que he obtenido a través de asesorías y consultoras en países latinoamericanos, y que son la fuente de praxis de este trabajo, me ha permitido arribar a la tesis de que el fracaso o el éxito de las reformas educativas descansa en los centros formadores de docentes.
De hecho, lo más difícil de la reforma educativa es querer y generar una actitud de cambio. De la capacidad que tengan estas instituciones para cambiar su mentalidad, dependen las transformaciones que se deben operar en la formación de maestros y profesores y las proyecciones de éstas en la educación.
La intervención que he realizado en centros formadores de docentes, dirigida a la capacitación de los profesores universitarios, me ha permitido arribar a conclusiones que expongo en el trabajo, entre las cuales se destacan las siguientes: 1) para cambiar es necesario sentir la necesidad de cambio 2) hay que incidir en un cambio global de la mentalidad, integrada multidimencionalmente 3) cambiar la mentalidad docente supone adquirir o desarrollar habilidades que capaciten para nuevos y más eficientes desempeños profesionales
Evaluation and comparison of control and heat treated l-shape furniture joints produced from scotch pine and ash wood under static bending and cyclic fatigue bending loadings
Get PDFThis study investigated how the mechanical properties of L-shape joints produced from heat treated Scotch pine or ash wood behaved under cyclic fatigue loading and compared this with the mechanical properties of non-heat treated wood materials. Additionally, static bending performances of the L-shape of joints were investigated and compared to fatigue bending performance of same type of joints. Results indicated that increasing number of staple from 6 to 8 and density generally increased static bending of L-shape joints. Static bending resistance of L-shape joints produced from control Ash wood significantly higher than those of L-shape joints produced from heat treated Ash wood while no significant difference were observed between static bending resistance L-shape joints produced from control Scotch pine and L-shape joints produced from heat treated Scotch pine wood. The fatigue bending resistances of L-shape joints produced from heat treated samples generally passed and failed the same loading steps with those produced from control samples which means both L-shape joints could be used in same service area. L-shape joints under static and fatigue loadings mostly indicated staple leg shear mode. The one under fatigue loading was more than the one under static loading. Additionally, some joints under fatigue loading indicated staple rupture. The overall ratio of static bending loading to cyclic fatigue bending loading for L-shape joints was obtained as 2.85
Changes in the content and composition of the extractives in thermally modified tropical hardwoods
Get PDFChemical composition of wood is known to change during thermal treatments. Two species grown in Turkey, afrormosia (Pericopsis elata) and duka (Tapirira guianensis) were heat treated according to Thermowood® method. Lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol and water were determined. Wood extracts were analysed by gas chromatography with mass detection and existing compounds were identified by NIST17 database. Results show that hemicelluloses and cellulose content decreased for both heat-treated woods along the treatment while lignin percentage increased. The analysis of extractives has shown several compounds normally associated to lignin thermal degradation that increased along the treatment. At the same time several compounds associated to carbohydrate thermal degradation were found in all the extracts for both heat-treated woods. These founding have allowed the understanding of the degradation pattern of wood during thermal modification. There was not much difference between afrormosia and duka woods structural compounds behaviour along thermal modification. However, the variation of the amount of extractives along the treatment depended on the species