Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This paper introduces a systematic deterministic framework for planning and the analysis of facility layouts aimed at manufacturing a variety of parts, being components of specific end products. The essence of the proposed approach lies in the decomposition of a traditional job-shop into layout modules of generic material flow patterns, that inherently yields improved efficiency of the entire system. It entails the use of a relevant reasoning scheme based on production flow analysis and the method of hierarchical clustering of specified process routings for parts. The approach has been studied in the aspect of its application in an actual woodworking facility, dealing with fabrication of wooden toy sets. The respective workflows were subjected to the analysis in order to identify production bottlenecks using data derived from the real case study. As a result, the designated process layout alternatives have been evaluated in terms of assumed measures of the operational performance. An inseparable part of the research was exploring the capability for the optimum selection of a multi-part product mix , to be fabricated in defined time frames. In this regard, the usability as well as the computational efficacy of the integer linear programming modelling have been fully confirmed. The results gained show in particular that the suggested methodical scheme could be a useful tool in planning optimised manufacture of customised wood products of modular construction.

Timber grading is an essential step into the value process to determine wood usability for structural uses. It requires well-described characteristics obtained easily by taking non-destructive measurements to quantify reliable indicators of mechanical properties. In this paper we present an approach based on both timber scale and clear-wood scale measurements using the case of Mountain pine (Pinus uncinata). An important experimental plan have been performed from collected trees of French and Spain Pyrenean regions allowing significantly the use of inter-correlations between measurements. The physical properties of clear wood present an important adaptation of tree growth condition with a lower modulus of elasticity as a consequence of microstructure at cell-wall level but a conventional modulus or rupture in bending for pines. However, the results on timber presents an important the difference between visual and machine grading for this species in view of mechanical properties considered. The results obtained also show possible improvement and limitations of current regulation in the grading mountain pine timber for structural use.

Fibre morphology of some Nigerian tropical timber species were evaluated to determine their potentials as suitable source of raw material for pulp and paper making. The fibre dimension of the species showed that Syzygium guineense had the longest fibre length (2.0 mm) followed by Anogeissus leiocarpa (1.75 mm) while Albizia zygia had the shortest fibre length of 1.05 mm. Irvingia gabonensis had the largest fibre diameter while Vernonia colorata had the smallest. Vitellaria paradoxa had the widest lumen of 8.87µm while  Irvingia gabonensis had the smallest lumen and thickest  (6.87µm) cell wall while Vernonia colorata had the thinnest (4.40µm). Albizia zygia had the most slender fibres while Vitellaria paradoxa had the most rigid fibres. All the species had narrow fibre lumens and the cell walls were thick, which may have given poor results to the pulp made from them. The results of the ANOVA showed that there was high significant variation in all the fibre dimensions and the derived values of the species. DMR test showed that no statistical difference existed in the fibre length of Isoberlina doka, Khaya ivorensis and Albizia zygia. However, Vernonia colorata, Irvingia gabonensis and Vitellaria paradoxa had similar fibre length as well as Afzelia africana and Lannea welwitchii. All the species passed the Runkel Ratio < 1 acceptable values for paper making fibre except Vitellaria paradoxa and Anogeissus leiocarpa with RR value of 1.38 and 1.03. Syzygium guineense and  Irvingia gabonensis passed FC > 0.55 for an acceptable value for paper making. All the fibres were elastic except Vitellaria paradoxa and Anogeissus leiocarpa.

Ground contact speeds up timber decay because of the large number of microorganisms in soil. This study, we assessed the natural durability of seven tropical species using the European standard EN 807 (2001). We embedded samples of Dalbergia granadillo, Cordia elaeagnoides, Swietenia humillis, Tabebuia donell-smithii, Hura polyandra, Enterolobium cyclocarpum and Tabebuia rosea and temperate species Fagus sylvatica (as a control) in sandy, clay-sandy-loam and clay-loam for 8, 16, 24 and 32 weeks. We evaluated durability of the samples by determining the mass loss and modulus of elasticity (MOE) loss. The results varied significantly (p < 0.001) depending on timber species and soil type considered. The D. granadillo and C. elaeagnoides were the most durable, with mass losses of 4.5%, 6.5% and MOE losses of 4.5%, 20.5%, respectively. F. sylvatica, T. rosea and E. cyclocarpum samples were the least durable, with mass losses of 22.3-25% and MOE losses of 35.8-59.8%, respectively. Decay was most aggressive in sandy-clay-loam soil followed by the clay-loam soil and finally the sandy soil.

This study was performed to determine the surface properties of novel wood-based reinforced composites made from poplar veneers and phenolic resins. The veneers with different thickness (1.8, 4, 6, 8 mm) were finely crushed and then were impregnated with phenolic resins to achieve different resin loading (12, 14, 18%). Finally, they were laminated or random paved to manufacture novel wood-based reinforced composites with different target densities (0.8-1.1 g cm-3). With increased veneer thickness or resin content, the hardness of novel wood-based reinforced composites decreased and their roughness increased. The increase of density contributed to the increased hardness and decreased roughness. The surface wettability of novel wood-based reinforced composites appeared to be closely related to their surface roughness. There was a negative correlation between contact angle and roughness. The novel wood-based reinforced composites prepared by laminated mat formation showed higher hardness, lower roughness than those by random mat formation. Such data of surface properties can be applied to design the novel wood-based reinforced composites products with desired quality and provide basic information for further panel processing.

This study aimed to analyze the resistance of the thermally treated wood of Pinus caribaea and Eucalyptus saligna to the biological attack of wood rotting fungi. The heat treatment processes were carried out in electric oven under nitrogen atmosphere, starting from 100 °C until reaching each one of the final temperatures of the process: 120, 140, 160, and 180 °C. The resistance assays were performed for white rot, brown rot, and soft rot fungi. The increase in decay resistance was observed for heat-treated wood of Pinus caribaea at higher temperatures. On the other hand, Eucalyptus saligna showed increased resistance to rotting fungi at all tested temperatures, except for white and soft rot at 120 °C. In general, the heat treatment process showed good results for its use as a wood preservative method.

Alternative and higher value uses are needed for residual materials generated from wood products processing. Western redcedar sawdust contains an array of unique chemicals and has the potential to be used to alter the appearance, stability and durability of non-durable timbers. Here it was hypothesized that impregnation of Western redcedar heartwood extractives into Pacific silver fir would decrease shrinkage, hygroscopicity, and susceptibility to decay. Western redcedar hot water extracts were obtained from sawdust and used to pressure-treat Pacific silver fir blocks. Extractive impregnation enhanced the wood’s appearance and gave it a more cedar-like brown colour. Impregnated samples had reduced shrinkage, but were not as dimensionally stable as Western redcedar heartwood. Pacific silver fir blocks impregnated with water-soluble extractives were also highly susceptible to leaching, and leached samples had similar shrinkage values to untreated controls. In contrast, leaching had little effect on the hygroscopicity of the Western redcedar heartwood. Extractive-impregnated Pacific silver fir blocks had increased resistance to decay by two brown-rot fungi, and showed resistance similar to that of Western redcedar heartwood. However, leached blocks did not have the same decay resistance.

Eucalyptus, with the commercial name of Blue gum, is a viscoelastic material strongly influenced when under constant load (Creep), being this phenomenon - in the context of displacements - exacerbated with transient relative humidity (variations of the water content in the wood material). The evaluation of bending creep was done in indoor / constant and transient humidity conditions. In the latter, mechano-sorptive effect, the creep bending tests were done for a period of 60 days with cycles of wetting-and-drying. Each cycle has 7 days of duration. Defect free specimens with dimensions of 20*20*400 mm3 (approximately to the scale 1:10) of Eucalyptus globulu. wood species were used. To fit the creep behaviour and extrapolate results for different periods (1, 10 and 50 years) a survey of different numerical models was done. Rational, parabolic and polynomial functions were chosen. In bending, Blue gum wood species presented a behaviour without a creep limit, therefore labile. Through the models used for extrapolations a significant variability was found for different periods. Values of the main standard of wood design (Eurocode 5) were exceeded. The most consistent mathematical model was the rational model because it is the one that has led to closer and stable results.

El paseo es un arte individual. Su naturaleza puede que tenga como fin —como acicate secreto—, todo lo que hay entre nosotros y la metamorfosis incesante de los paisajes rurales o urbanos, hacia la inquietud del tiempo. Ineluctablemente se convierte en un  medio, principio y  fin preventivo del cuidado del cuerpo, ya que, de hecho, no obedece sólo a la  natural necesidad de un afán biológico, sino, en cierto modo, configura y vertebra la identidad de  cada persona.  Los médicos lo aconsejan. La publicidad lo afirma. Los paseantes lo confirman. El apogeo del paseo en nuestra sociedad y época posmoderna podía legitimarnos a  creer  que hemos ganado la partida contra las claras inclinaciones hacia la vida sedentaria en las ciu- dades. Por eso, muchas veces pasear con los pies desnudos por la playa sobre la fina arena húme- da o recalentada y con la brisa marina acariciando nuestra piel se ha  erigido, esencialmente  para muchos de nosotros, habitantes de ciudad, en una vía física para conservar la salud y aumentarla. Puede recordarnos nuestro origen acuático. Tal vez si evocamos prudentemente lo que podía significar en sus textos para los griegos antiguos, siempre tan familiares como extra- ños, tan cercanos como lejanos, los primeros paseos en la civilización occidental, con el fin de valorarlos adecuadamente como norma de vida que garantice el disfrute de la movilidad natural podamos transformar su arcaico significado dotándole de una ejemplar extensión  metafísica1.Andando se hace camino.Vamos a ello, paso a paso.

La sociedad actual se encuentra inmersa en un proceso de cambio impulsado por los pro- gresos acaecidos en las tecnologías. El sistema educativo debe estar preparado para hacer frente  a esos avances, siendo la formación del profesorado el elemento clave para facilitar la integra- ción curricular de las nuevas tecnologías, tal y como se demanda desde diferentes ámbitos sociales, institucionales, etc. La formación del profesorado debe ir orientada a innovar, experimentar con las Tecnolo- gías de la Información y Comunicación (TIC) y reflexionar sobre su uso, favoreciendo el desa- rrollo y la adquisición de diferentes competencias tecnológicas que le capaciten para utilizar didácticamente las herramientas y aplicaciones procedentes de la Web 2.0, convirtiéndose en un recurso más dentro del aula.