Revistas Universidad del Bío-Bío
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Time-moisture superposition principle in creep behavior of white oak with various earlywood vessel locations
Get PDFCreep behavior of wood plays a fundamental role in precision processing of wood. In this work, experi- mental creep tests have been conducted to determine the influence of earlywood vessel location and moisture content on creep behavior of Quercus alba (white oak). Time-moisture superposition principle was applied to predict long-term creep behavior of white oak. Results revealed that both of instantaneous and 45-min strain of specimens increased with the increasing of moisture content and decreased with increasing distance between earlywood vessel belt and load-bearing surface significantly. Additionally, the time-moisture superposition principle was found to have feasibility to predict creep behavior of white oak with various earlywood vessel locations and moisture content ranges (6 % - 18 %). We believe that the proposed investigation was beneficial for the processing precision and civil engineering applications of wood
Representaciones sociales de estudiantes de enseñanza media en la convivencia escolar durante la pandemia COVID-19
Get PDFLas representaciones sociales permiten comprender aquellos conocimientos que se producen en la interacción comunicativa, que se desarrolla en un contexto social. La pandemia del COVID-19 y las medidas sanitarias tomadas a nivel escolar repercutieron en las relaciones sociales de los estudiantes y en la convivencia escolar. La convivencia es uno de los ejes claves para el desarrollo del aprendizaje en las comunidades educativas, para promover la democracia, la inclusión, la participación y resolución pacífica de conflictos. El objetivo de esta investigación es comprender la construcción de las representaciones sociales acerca de la convivencia escolar de los estudiantes de enseñanza media de cuatro establecimientos educativos de Concepción. La metodología se desarrolló desde un paradigma comprensivo interpretativo, con un enfoque cualitativo; como instrumento de elaboración de información se utilizaron entrevistas grupales semi estructuradas, las que fueron analizadas por medio de la técnica de análisis categorial temático, donde se estableció como tema principal la convivencia escolar. Para ello, se utilizó Nvivo como software de apoyo para el análisis realizado. Las representaciones de los estudiantes se configuraron en torno a la subjetividad de construcción identitaria, comunicación y las normas que regulan las interacciones dentro de los contextos escolares.Social representations allow us to understand the knowledge that is produced in communicative interaction, which takes place in a social context. The covid-19 pandemic and the sanitary measures taken at the school level had an impact on the social relations of students and on school coexistence. Coexistence is one of the key axes for the development of learning in educational communities, to promote democracy, inclusion, participation and peaceful conflict resolution. The objective of this research is to understand the construction of social representations about the school life of high school students from four educational establishments in Concepción. The methodology was developed from a comprehensive interpretative paradigm, with a qualitative approach; Semi-structured group interviews were used as an instrument for preparing information, which were analyzed through the thematic categorical analysis technique, where school coexistence was established as the main theme. For this, Nvivo was used as support software for the analysis carried out. The representations of the students were configured around the subjectivity of identity construction, communication and the norms that regulate the interactions within the school contexts
Effect of ultra-low temperature on some mechanical properties of painted and film-coated plywood
Get PDFPlywood is used for insulation systems in liquid natural gas cargo ships because of its good thermal properties. However, there are only a few research investigating the mechanical properties of plywood exposed to ultra-low temperatures. This study aims to determine how plywood reacts when exposed to ultra-low temperatures, such as - 196 °C. To achieve this purpose, the present study investigated the bending strength, modulus of elasticity, and tensile-shear strength of painted and film-coated plywood under ultra-low temperatures. The mechanical properties of plywood were discovered to be significantly impacted by the ultra-low temperature as a result of this research.. Moreover, not only the bending strength of the painted and film-coated plywood increased with decreasing temperature, but also the modules of elasticity of the painted and film-coated plywood increased. At decreasing temperature, the tensile shear strength of the painted and film-coated oven-dried plywood increased, but the ensile-shear strength of painted and film-coated air-dried plywood decreased. The tensile shear strength of air-dried plywood was determined to be more sensitive to the temperature change. Therefore, attention should be paid to plywood used in liquefied natural gas cargo ships with high humidity
Comparing the structure of spruce wood biodegraded by Trametes versicolor and Gloeophyllum trabeum and further utilization of this material
Get PDFDevelopment of new materials puts a great emphasis on saving production costs, energy, decreasing the amount and number of chemicals used during the manufacturing process. Bio-based materials can be ecologically produced and recycled after their lifespan, which saves the environment. The recent interest in bio-based materials led to the objective of this work. In this article, the structure of spruce wood (Picea abies) biodegraded by the white-rot fungus Trametes versicolor and brown-rot fungus Gloeophyllum trabeum was studied. Structure of the wood was observed macroscopically and microscopically. Classic and unusual stain combinations were used in this work. Ethanol was intentionally omitted in the process of making permanent mounts. It was done to preserve the coherence of the decayed microsections and to keep small fragments from being rinsed away. Results of the observations suggest that spruce wood decayed by these fungi could be used as an insulation material. Wood decaying fungi decrease the density of wood and increase its porosity. A low density and high porosity are important properties for insulation materials. According to the results, spruce wood decayed by Trametes versicolor would be more suitable to be used as an insulating material
Sampling sufficiency for mechanical properties of wood
Get PDFBased on most recently published studies, there is a large variability in both the mechanical properties of wood and sample sizes selected to evaluate them. This study aims to define sampling sufficiency for some mechanical properties of wood, which were bending strength, bending modulus, compressive strength, compressive modulus, hardness, and shear strength. The mechanical tests were carried out according to the ASTM D143 on wood samples cut from clonal Eucalyptus planted in southern Brazil. Sampling sufficiency was determined by an intensive computational method based on resampling of original data using Monte Carlo simulations. The experimental tests data conformed to the normal distribution and most of the obtained sufficient sample sizes determined by Monte Carlo simulation were above those sample sizes used in most already published studies. Furthermore, properties related to wood stiffness presented smaller variabilities than their respective properties associated with wood strength, leading to smaller sample sizes for the former cases
Influence of pretreatment on properties of bamboo portland cement particle board
Get PDFBamboo contains water-soluble saccharides and carboxylic acid which have an anticoagulation effect on Portland cement, and the anticoagulation ingredients can directly influence the hydration reaction extent. Hydration product varieties and hydration product-bamboo shaving binding interfaces of the Portland cement, and finally the mechanical properties of bamboo cement particle boards. In this paper, bamboo shavings are pretreated by carbonizing treatment, hydro-thermal treatment and alkali treatment; high performance liquid chromatography is adopted to analyze the influences of three different pretreatment methods on contents of water-soluble saccharides and carboxylic acid in the bamboo shavings; a Fourier infrared spectrometer and an X-ray diffractometer are respectively utilized to analyze the characteristic peak changes and crystallization property changes of chemical ingredients of the bamboo shavings before and after the three types of pretreat- ment. This paper discusses effects of three types of pretreatment methods in eliminating water-soluble saccha- rides and carboxylic acid in the bamboo shavings. Bamboo Portland cement particle boards was prepared using bamboo shavings, which are pretreated in three ways, and influences and mechanisms of different pretreatment methods on properties of the bamboo Portland cement particle boards were studied. Research indicates that the mechanical properties of the Portland cement particle board prepared from bamboo shavings pretreated with 3 % NaOH solution are superior to requirements of qualified products and superior products specified in the Standard
Patrones sociales y espaciales: Estudio comparativo entre dos espacios públicos en la ciudad de Quito, Ecuador
Get PDFThe public space is the ideal scenario to analyze and evaluate the correlation between behavior and morphological conditioning factors in the urban structure. This relationship between the behavior of inhabitants and the spatial configuration is experienced as a social result. From this perspective, the success of urban design is perceived from the capacity it has to reconcile spatial conditions with the alternatives it allows for collective relations, from a close and bidirectional relationship. According to urban studies on morphological approaches, from the second half of the twentieth century two formal configurations are recognized: first, one identified as the traditional city layout, understanding cities as interconnected structures of buildings, with the gaps between them forming the blocks; second, the so-called functionalist, whose configuration of buildings includes a free and isolated arrangement in space, generating undefined layouts (Carmona, 2010, p. 77). This research presents a comparative analysis study for public spaces, which combines studies related to the city’s type-morphology and crucial treatises on behavior in public spaces. Spatial and behavioral patterns are evaluated in two areas in the city of Quito, Ecuador: on one hand, a square in the Historic Center with a traditional layout: Plaza "La Merced"; and on the other, an urban space with a functionalist layout: Plaza "La República". The study focuses on the generation of diagnostic information that comes directly from the observation of social behavior and the analysis of the morphological elements of the studied space. Finally, this study contrasts the review of specific spatial conditions of a place with the behavioral dynamics of its inhabitants.El espacio público es el escenario idóneo para analizar y evaluar la correlación existente entre el comportamiento y las condicionantes morfológicas en la estructura urbana. Esta relación entre el comportamiento de habitantes y la configuración espacial se experimenta como un resultante social. Desde esta perspectiva, se percibe el éxito del diseño urbano desde la capacidad que tiene de conciliar las condiciones espaciales con las alternativas que permite a las relaciones colectivas, desde una relación estrecha y bidireccional. De acuerdo con los estudios urbanos sobre aproximaciones morfológicas, a partir de la segunda mitad del siglo XX se reconocen dos configuraciones formales: primero, la que se identifica como esquema de ciudad tradicional, en tanto entender las ciudades como estructuras interconectadas de edificaciones, por lo que los vacíos que quedan entre ellas son los que configuran las manzanas; segundo, la denominada funcionalista, cuya configuración de edificaciones comprende una disposición libre y aislada en el espacio, generando esquemas indefinidos (Carmona, 2010, p. 77). Esta investigación presenta un estudio comparativo de análisis para los espacios públicos, el cual conjuga estudios relacionados con tipo-morfología de la ciudad y tratados cruciales sobre el comportamiento en los espacios públicos. Se evalúan los patrones espaciales y de comportamiento en dos áreas en la ciudad de Quito, Ecuador: por un lado, una plaza en el Centro Histórico con un esquema tradicional: Plaza “La Merced”; y por otro, un espacio urbano con un esquema funcionalista: Plaza “La República”. El estudio se enfoca en la generación de información diagnóstica que proviene directamente de la observación sobre el comportamiento social y el análisis de los elementos morfológicos del espacio estudiado. Finalmente, este estudio contrasta la revisión de condiciones espaciales específicas de un lugar con las dinámicas de comportamiento de sus habitantes
Caracterización de las tipologías de representación a través de la Etnografía virtual. Los caminos Purépecha en la región lacustre de Pátzcuaro como corredor patrimonial
Get PDFLos caminos han comenzado en época reciente a valorarse como un recurso patrimonial que trascienden más allá de considerarse una infraestructura vinculada a la antropización del territorio. Actualmente, son escasas las propuestas metodológicas para su caracterización patrimonial. Por ello, este artículo muestra el diseño y aplicación de una metodología interdisciplinar apoyada en la Etnografía Virtual y basada en un análisis histórico-cartográfico que permite registrar y categorizar tipologías de representación asociadas a la evolución de los caminos. Se toma como caso de estudio la región lacustre de Pátzcuaro, en México. El análisis histórico-cartográfico a través de la etnografía virtual permite identificar tipologías de representación asociadas no solo a la evolución histórica de los caminos, sino que también de su vínculo con la antropización del entorno lacustre. Al llegar al periodo contemporáneo, la cartografía muestra los caminos como una mera infraestructura y visibiliza a los pueblos lacustres como piezas separadas en torno al turismo cultural. Con la aplicación de esta metodología, se confirma que la cartografía es una herramienta estratégica y que su evolución ha permitido establecer que, históricamente, los caminos han sido un eje vertebrador en la ordenación y el desarrollo del este territorio en distintos procesos históricos. Su vigencia es reflejo de que esta región se mantenga vigente, dada su actual transferencia al turismo cultural. Es importante visibilizar que son todas estas poblaciones en su conjunto las que le confieren una identidad cultural a la región lacustre y que los caminos son el medio que ha permitido que este territorio evolucione históricamente de acuerdo con la necesidad de sus poblaciones, situación que justifica su consideración como corredor patrimonial.Roads have recently begun to be valued as a heritage resource that transcends being considered solely as an infrastructure linked to the anthropization of the territory. Currently, there are few methodological proposals for their heritage characterization. Therefore, this article shows the design and application of an interdisciplinary methodology supported by Virtual Ethnography and based on a historical-cartographic analysis that allows recording and categorizing representation typologies associated with the evolution of roads. The lake region of Patzcuaro, Mexico, is taken as a case study. Its historical-cartographic analysis through virtual ethnography allows identifying typologies of representation associated not only with the historical evolution of roads but also with their ties to the anthropization of the lake setting. The cartography, in the contemporary period, shows roads as a mere infrastructure and makes the lake villages visible as separate pieces for cultural tourism. With the application of this methodology, it is confirmed that cartography is a strategic tool and that its evolution has made it possible to establish that, historically, roads have been a backbone in the management and development of this territory in different historical processes. Its validity is a reflection of the fact that this region is still valid, given its current transfer to cultural tourism. It is important to make visible that it is these populations as a whole that confer a cultural identity to the lake region and that the roads are the means that have allowed this territory to evolve historically considering the needs of its population, a situation that justifies its consideration as a heritage corridor
Mechanical and acoustic characteristics of four wood species subjected to bending load
Get PDFThe mechanical and acoustic properties of four commonly used wood species, including poplar (Populus tomentosa), mahogany (Swietenia mahagoni), beech (Fagus orientalis), and Ash (Fraxinus excelsior) wood were investigated through using three-point bending and notched bending tests synchronizing with power spectrum analysis method and fractal dimension theory. The results showed that the bending modulus of elasticity and modulus of rapture changed in the same trend with the order ranging from high to low was ash, beech, poplar and mahogany, successively. The brittle fracture occurred in mahogany samples and ductile fracture raised in the other three wood species. Positive proportional correlation was observed between maximum acoustic pressure and fractal dimension of power spectrum regardless of seeing four wood species as independent or population samples. The failure modes can be identified by amplitude-frequency curve and fractal dimension of power spectrum with following laws: the peak value in amplitude-frequency curve and fractal dimension of power spectrum were relatively higher when a single crack developed at latewood; for crack developed at earlywood, only one peak was observed in power amplitude-frequency curves, and the corresponding fractal dimension of power spectrum was smaller than the that of latewood; in case of failure modes with two cracks developed at earlywood, there are two peaks in amplitude-frequency curve and the fractal dimension of power spectrum was between those of single crack developed at earlywood and latewood. The vibrational properties of the four wood species can be characterized through using power spectrum analysis method and notched bending test method can be used to distinguish the failure modes of samples
Evaluación del coeficiente de conductividad y transmitancia térmica de elementos constructivos de tierra
Get PDFO objetivo deste trabalho é determinar a condutividade térmica de diferentes elementos construtivos de terra produzidos com materiais característicos do centro-leste da província de Santa Fé (Argentina) e avaliar sua adequação para uso na construção de envelopes de edifícios que atendam aos requisitos de isolamento térmico dos regulamentos nacionais correspondentes. Para isso, foram feitos corpos de prova de acordo com as diferentes técnicas de construção com terra utilizadas na região (bloco de terra comprimida, adobe, tapia, quincha e gesso) e foi medido seu coeficiente de condutividade térmica, com o qual foi calculada a transmitância térmica de diferentes pacotes construtivos de terra. Os resultados obtidos indicam que as técnicas de construção com terra avaliadas apresentam, em todos os casos, melhor desempenho térmico do que as tradicionais paredes sólidas de tijolos cerâmicos ou blocos de concreto, sendo a quincha a técnica com maior capacidade de isolamento térmico.En este trabajo se pretende determinar la conductividad térmica de diferentes elementos constructivos de tierra producidos con materiales característicos del centro este de la provincia de Santa Fe (Argentina) y evaluar su aptitud para ser empleados en la construcción de envolventes que cumplan con los requerimientos de aislación térmica solicitados por la normativa nacional correspondiente. Para ello se confeccionaron probetas siguiendo las diferentes técnicas de construcción con tierra empleadas en la región (bloque de tierra comprimida, adobe, tapia, quincha y revoques) y se midió su coeficiente de conductividad térmica, con el cual se calculó la transmitancia térmica de diferentes paquetes constructivos de tierra. Los resultados obtenidos indican que las técnicas de construcción con tierra evaluadas presentan, en todos los casos, un mejor desempeño térmico que los tradicionales muros de ladrillo cerámico macizo o bloques de hormigón, siendo la quincha la técnica con mayor capacidad de aislamiento térmico.The aim of this work is to determine the thermal conductivity of different earthen constructive elements produced with materials typical of the central-eastern part of the Province of Santa Fe (Argentina), and to evaluate their suitability to be used in the construction of envelopes that comply with the thermal insulation requirements of the corresponding National Regulations. For this purpose, test specimens were made following the different earth construction techniques used in the region (compressed earth block, adobe, rammed earth (tapia), wattle and daub (quincha), and plaster), and their thermal conductivity coefficient was measured, with which the thermal transmittance of different earth construction packages was calculated. The results obtained indicate that the earth construction techniques evaluated show, in all cases, a better thermal performance than traditional solid ceramic brick or concrete block walls, with wattle and daub being the technique with the highest thermal insulation capacity