Influence de la température et de la teneur en humidité sur les propriétés mécaniques du bois associées au procédé de fragmentation par équarrisseuse-fragmenteuse

Cette étude a évalué l’influence de la température et de la teneur en humidité du bois sur son comportement mécanique lors du procédé d’obtention des copeaux papetiers. Les propriétés mécaniques qui furent étudiées sont le cisaillement parallèle au fil, le fendillement et la flexion statique. Des échantillons jumelés du duramen et de l’aubier ont été pris des billes d’épinette noire et de sapin baumier pour chaque propriété mécanique. Les essais mécaniques ont été conduits à des températures variant entre -30ʻC et 20ʻC et à des intervalles de 10ʻC. La teneur en humidité des échantillons était largement au-dessus du point de saturation des fibres. La teneur en humidité, la masse volumique basale et la largeur des cernes ont aussi été mesurées pour chaque échantillon. Les résultats montrent que, pour les deux espèces et pour toutes les propriétés mécaniques étudiées, la température a eu un effet significatif sur les propriétés mécaniques uniquement au-dessous de 0ʻC. Dans ce cas, cet effet a été plus évident pour l’aubier que pour le duramen. En général, pour des températures de 0ʻC et plus, la température n’a pas affecté différemment les propriétés mécaniques étudiées, autant pour l’aubier que pour le duramen. Le fendillement a été la propriété mécanique la plus sensible à la variation de la température, suivi par le cisaillement et le MOR et le MOE en flexion. En outre, la teneur en humidité a été l’élément le plus important pour expliquer les propriétés mécaniques au-dessous de 0ʻC. En revanche, pour les températures de 0ʻC et plus, la masse volumique basale fut le facteur principal pour expliquer les propriétés mécaniques. La largeur des cernes de croissance n’a pas constitué un élément significatif pour prédire aucune propriété mécanique. Les résultats de ce travail devraient servir à améliorer la performance des équarrisseuses-fragmenteuses autant en hiver qu’en été

Étude du comportement physique des bois au-dessus et au-dessous du point de saturation des fibres

Le but principal de ce travail fut d'étudier les changements des propriétés physiques et des relations eau-bois de quatre espèces de feuillus au-dessous et au-dessus du point de saturation des fibres (PSF). Deux espèces tropicales, une tempérée et une provenant de plantation, avec des plans ligneux très variables, furent étudiées. Dans un premier volet de ce travail, des échantillons des quatre espèces furent soumis à trois conditions de désorption à 21°C à partir de la saturation intégrale ou de l’état vert jusqu'à atteindre des humidités d’équilibre (Héq) au-dessous du PSF. L'état de l'eau et la distribution de l’eau liée et liquide ont été analysés par résonance magnétique nucléaire et par imagerie par résonance magnétique (IRM). Le temps de relaxation transversale (T2) a indiqué la présence d’eau liquide dans le bois au-dessous du PSF. L’IRM a permis d'identifier les éléments anatomiques où cette eau liquide pourrait être localisée. En outre, l'eau liée n’était pas répartie uniformément dans la structure du bois même à l’équilibre global, étant les tissus plus denses plus hygroscopiques que les plus légers. Les deux techniques ont révélé que l'anatomie du bois joue un rôle majeur dans le drainage et diffusion de l'eau. Le deuxième volet a étudié l'effet de quatre taux de désorption sur le comportement dimensionnel du bois d’Eucalyptus saligna dans une gamme de teneurs en humidité couvrant tout le domaine hygroscopique. Des taux de désorption plus lents ont entrainé des retraits plus élevés, mais ces différents taux n’ont pas changé la pente des courbes retrait-Héq. Le collapse du bois fut plus important pour les taux de désorption plus lents et il fut plus grand dans la direction tangentielle. Le PSF établi par l’extrapolation de la portion linéaire des courbes retrait-Héq ne s’est pas montré adéquat pour des espèces sujettes au collapse. Enfin, les résultats ont montré le phénomène de début de perte d'eau liée avant que toute l'eau liquide soit drainée.The main purpose of this work was to study the changes in the physical properties and in the wood-water relations of four hardwood species below and above the fiber saturation point (FSP). Two tropical, one temperate and one plantation grown species with high variable anatomical structure were investigated. In the first part of this work, samples of all species were destined to three desorption conditions at 21°C from full saturated state or from green condition until reach equilibrium moisture contents (EMC) below the FSP. The water state and the distribution of liquid and bound water were analysed by nuclear magnetic resonance and magnetic resonance (MR) microimaging. Transverse relaxation times T2 showed entrapped liquid water below the FSP. The MR microimaging study allowed identifying in which anatomical elements this water could be located. Also, bound water was not uniformly distributed in wood structure even at a global EMC, being the denser tissues more hygroscopic than the lighter ones. Both techniques revealed that wood anatomy plays a major role in water drainage and diffusion. The second part of this work was dedicated to study the effect of four desorption rates on the dimensional behaviour of Eucalyptus saligna wood under a range of moisture contents covering the whole hygroscopic domain. Slower desorption rates implied higher shrinkages, but these different rates have not affected the slope of shrinkage-EMC curves. The collapse of Eucalyptus saligna wood was more important for slower desorption rates and it was greater in the tangential direction. The FSP determined by the extended linear portion of the shrinkage-EMC curves revealed to be not adequate for collapse-prone species. Finally, the results indicated the phenomenon of the beginning of the loss of bound water before all liquid water has been drained

Cyber-physical systems design: transition from functional to architectural models

Normally, the design process of Cyber-Physical Systems (CPSs) starts with the creation of functional models that are used for simulation purposes. However, most of the time such models are not directly reused for the design of the architecture of the target CPS. As a consequence, more efforts than strictly necessary are spent during the CPS architecture design phase. This paper presents an approach called Assisted Transformation of Models (AST), which aims at transforming functional (simulation) models designed in the Simulink environment into architectural models represented in the Architecture Analysis and Design Language. Using AST, designers can perform a smooth transition between these two design phases, with an additional advantage of assuring the coupling between functional and architectural models. The use and benefits of AST are exemplified in the paper in a study devoted to for the design of a typical CPS: an Unmanned Aerial Vehicle.CAPE

Uso de microrganismos de efluente industrial no controle biológico de vetores

Justificativa e Objetivos: a utilização de microrganismos como controle biológico de vetores sanitários pode ser considerada uma prática menos agressiva ao ambiente, em comparação com os produtos químicos utilizados. O presente estudo avaliou a eficiência de suspensões celulares de fungos e bactérias isolados de efluentes industriais têxteis no controle sanitário dos vetores naturais Aedes aegypti e Dermacentor nitens como alternativa sustentável de controle biológico. Métodos: foram avaliadas sete linhagens de fungos e seis de bactérias. Os isolados foram cultivados em caldo nutriente e caldo de batata, para bactérias e fungos, respectivamente. Alíquotas de 2 mL de cada suspensão microbiana foram adicionadas diretamente nas larvas dos mosquitos e nos carrapatos adultos. Foram analisadas alterações de movimentação e paralisação dos vetores em diferentes tempos de exposição entre zero e 20 minutos e três e 24 horas. Resultados: duas bactérias e um fungo promoveram uma desaceleração dos movimentos e/ou um aumento da movimentação dos ectoparasitas logo após a administração. Dois isolados bacterianos promoveram a paralisação dos movimentos de uma larva do mosquito Aedes aegypti em seu primeiro estágio de desenvolvimento, enquanto que um fungo provocou aumento da movimentação das larvas em seu estágio de desenvolvimento mais avançado. Conclusão: os microrganismos mostraram potencial uso no controle de vetores sanitários. Testes subsequentes de atividade dos possíveis metabólitos secundários produzidos e das formas de administração das culturas microbianas serão executados. Os resultados encontrados encorajam futuros estudos de otimização e caracterização dos extratos celulares, os quais poderão ser utilizados como ferramenta sustentável no controle biológico

Water State Study of Wood Structure of Four Hardwoods Below Fiber Saturation Point with Nuclear Magnetic Resonance

Nuclear magnetic resonance (NMR) is a useful, powerful, and noninvasive technique to study the dynamics of wood-water relations, both quantitatively and qualitatively. The main objective of this study was to use NMR to characterize the state of water below the FSP. Two tropical hardwood species, huayruro (Robinia coccinea Aublet) and cachimbo (Cariniana domesticata [C. Martius] Miers), a plantation-grown eucalyptus species (Eucalyptus saligna Smith), and a temperate species, red oak (Quercus rubra L.), were studied. These species were chosen for their diversity in terms of anatomical and physical properties. Desorption tests were carried out at 21°C in a single-step procedure from full saturation state for huayruro, cachimbo, and red oak and from green condition for E. saligna. Discrete T2 times were obtained for each species and equilibrium moisture content (EMC). The results showed that even under EMC, there was a region in the hygroscopic range in which the loss of bound water takes place before all liquid water was drained. This region varies according to wood species. Furthermore, variation in the fast T2 values among the different wood species gives an indication of how bound water is distributed and arranged in sorption sites

CELL WALL DOMAIN AND MOISTURE CONTENT INFLUENCE SOUTHERN PINE ELECTRICAL CONDUCTIVITY

Recent work has highlighted the importance of movement of chemicals and ions through the wood cell wall.  Movement depends strongly on moisture content and is necessary for structural damage mechanisms such as fastener corrosion and wood decay.  Here we present the first measurements of electrical resistance of southern pine at the subcellular level as a function of wood moisture content by using a 1 µm diameter probe.  Measurements were taken with the probe contacting the S2 layer of the cell wall and the cell corner compound middle lamella in the latewood and the cell corner compound middle lamella in the earlywood.  The resistance decreased with increasing relative humidity in all locations.  The resistance decreased more rapidly with relative humidity in the S2 layer than in any of the middle lamellae.  These results give insight into how some moisture-dependent wood properties affecting ion movement may be partitioned across cell wall layers

Salt Damage in Wood: Controlled Laboratory Exposures and Mechanical Property Measurements

Salt damage in wood can be recognized by its stringy appearance and is frequently observed in wood used in maritime structures and buildings built near the ocean. Whereas salt-damaged wood is common, little is known about the mechanism by which salt water alters the wood structure. There is no information on the effects of salt damage on the mechanical properties of wood. In this study, a laboratory method for creating salt damage in other porous materials was applied to wood. Wood pillars were placed in a reservoir of 5 M NaCl and exposed to a 40% RH environment. Capillary action pulled the salt water to the upper part of the pillars which were dry. Large deposits of effloresced salts were observed. The changes in mechanical properties caused by the salt were measured by the high-energy multiple impact (HEMI) test. Salt damage caused a reduction in the resistance to impact milling (RIM) of 6.5%, and it was concluded that salt damage causes only minor effects on the strength of wood. The tests were not conclusive as the exact mechanism of salt damage in treated wood. However, diffusion of mineral ions through the cell wall was found to be a key step in the salt damage mechanism

<b>Aplicação do software Zotero para apoiar a prática de Inteligência Competitiva</b><br><i>The application of Zotero software as a tool to support the practice of Competitive Intelligence</i>

Existem softwares que podem ser aplicados às várias fases do ciclo de Inteligência Competitiva – IC, como por exemplo, os que fazem a garimpagem de informações. Porém esses softwares são deficientes quando se trata de atividades realizadas entre as fases da coleta e análise que necessitam da leitura humana de documentos. Em geral, um software não consegue analisar dados puramente qualitativos nas fases do ciclo de IC. Por essa razão é de suma importância estudar softwares que tenham cunho colaborativo para saber até onde podem ser efetivos na prática de IC. Este artigo relata a aplicação do software Zotero por coletores e analistas de IC. Para averiguar seu apoio foi realizado um experimento simulando-o em um projeto de inteligência competitiva dividido em duas partes: sem o uso do software e com o uso do software. A simulação teve a participação de duas equipes locadas em diferentes pontos tendo a comunicação somente via web. O resultado indicou que com o uso do software foi possível comprovar que efetivamente o Zotero auxilia coletores e analistas em suas atividades. Palavras-chave: Inteligência competitiva. Informação tecnológica. Zotero. Abstract There are softwares which can be applied to various stages of the cycle of Competitive Intelligence - CI, such as, the ones which can sort the information. However, these softwares are defficient when it comes to activities to be carried out between the stages of collection and analysis which require the human reading of documents. Generally, a software cannot analize purely qualitative data in the stages of CI. Therefore, it is of paramount importance to study softwares which have a collaborative nature to know how far it can be effective in the practice of CI. This article reports the applicaiton of the software Zotero by CI collectors and analists. To assess its support, an simulating experiment was conducted in a CI project divided into two parts: one without the use of the software and the other with the use of the softwared. Two teams, located in different points and being connected only via web, participated in the simulation. The result indicated that with the use of the software it was possible to prove that Zotero effectivelly helps collectors and analysts in their activities. Keywords: Competetive intelligence. Technological information. Zotero