29 research outputs found
Développement d'une méthode d'inventaire de la qualité de la fibre au Québec
La valeur du panier de produits des peuplements rĂ©sineux dĂ©pend des dimensions et du dĂ©filement des tiges, de la prĂ©sence de dĂ©fauts internes, mais aussi des propriĂ©tĂ©s physiques et mĂ©caniques du bois, principalement de la rigiditĂ© du bois, puisque le bois dâĆuvre rĂ©sineux est utilisĂ© essentiellement Ă des fins structurales. La rigiditĂ© du bois dâĆuvre rĂ©sineux est estimĂ©e en usine lors du classement visuel ou mĂ©canique des sciages. En forĂȘt, cette connaissance nâexiste pas et il nâest pas possible aujourdâhui de localiser les rĂ©gions ou les peuplements avec un fort potentiel de bois rigide, ni dâĂ©valuer la valeur des bois ou encore de comparer la rentabilitĂ© des scĂ©narios sylvicoles, en considĂ©rant ce critĂšre de qualitĂ© dĂ©terminant. Cette absence de connaissances sâexplique principalement par les efforts et les coĂ»ts considĂ©rables associĂ©s Ă la rĂ©alisation dâun inventaire de la qualitĂ© de la fibre, lequel suppose en effet lâĂ©chantillonnage de milliers dâarbres et des analyses en laboratoire trĂšs exigeantes. Câest dans ce contexte que la spectroscopie proche infrarouge a Ă©tĂ© Ă©valuĂ©e, comme technologie rapide et non destructive, pour mesurer les propriĂ©tĂ©s physiques et mĂ©caniques du bois. Dans un premier temps, nous avons Ă©valuĂ© la variabilitĂ© Ă©cogĂ©ographique des propriĂ©tĂ©s du bois de lâĂ©pinette noire pour les deux principales vĂ©gĂ©tations potentielles de la forĂȘt borĂ©ale amĂ©nagĂ©e du QuĂ©bec (chapitre 1). Nous avons observĂ© que le bois poussant dans les peuplements purs dâĂ©pinettes noires avait des fibres matures plus longues, un bois significativement plus dense et de meilleures caractĂ©ristiques mĂ©caniques que le bois poussant dans des peuplements mĂ©langĂ©s avec le sapin baumier. Une approche de modĂ©lisation par saut dâĂ©chelle, basĂ©e sur des mesures de cernes provenant de 3350 placettes dâinventaire, a permis dâamĂ©liorer la performance de tous les modĂšles, en expliquant, Ă lâĂ©chelle du peuplement, 47%, 57%, 63% et 63% de la variabilitĂ© de la densitĂ© du bois, du module dâĂ©lasticitĂ©, de lâangle des microfibrilles, et de la longueur des fibres matures, avec des erreurs quadratiques moyennes, de 8.9 kg/mÂł, 0.52 GPa, 0.60° et 0.06 mm respectivement. Nous avons ensuite Ă©valuĂ© le potentiel de la spectroscopie proche infrarouge pour mesurer les propriĂ©tĂ©s du bois de lâĂ©pinette noire (chapitre 2). De bonnes et dâexcellentes statistiques de calibration (RÂČ, rapport de la performance Ă l'Ă©cart) ont Ă©tĂ© obtenues pour la densitĂ© basale (0.85, 1.8), lâangle des microfibrilles (0.79, 2.2), et le module dâĂ©lasticitĂ© (0.88, 2.9). Une rĂ©gression segmentĂ©e a Ă©galement Ă©tĂ© appliquĂ©e au profil radial de lâangle des microfibrilles afin de dĂ©terminer lâĂąge de transition du bois juvĂ©nile au bois mature. Les valeurs obtenues avec SilviScan ont Ă©tĂ© comparĂ©es Ă celles obtenues par spectroscopie. LâĂąge moyen de transition (23 ans ± 7 ans) a Ă©tĂ© lĂ©gĂšrement sous-estimĂ©, par spectroscopie proche infrarouge, avec une erreur de prĂ©diction moyenne de â2.2 ± 6.3 ans et des intervalles de confiance Ă 95% de â14.6 et 10.1. Ces rĂ©sultats suggĂšrent que lâĂąge de transition du bois juvĂ©nile au bois mature peut Ă©galement ĂȘtre prĂ©dit par spectroscopie proche infrarouge. Finalement, la spectroscopie proche infrarouge a Ă©tĂ© utilisĂ©e pour Ă©valuer la variabilitĂ© rĂ©gionale de la densitĂ© basale et de la rigiditĂ© du bois des principales essences borĂ©ales du QuĂ©bec (Ă©pinette noire, sapin baumier, pin gris, bouleau Ă papier et peuplier faux-tremble) (chapitre 3). Un systĂšme automatisĂ© a Ă©tĂ© dĂ©veloppĂ© Ă cette fin et calibrĂ© Ă partir de donnĂ©es SilviScan. La densitĂ© basale et la rigiditĂ© du bois ont Ă©tĂ© estimĂ©es sur 30159 carottes de bois provenant de 10573 placettes dâinventaire. Les observations de densitĂ© et de rigiditĂ© Ă©taient spatialement autocorrĂ©lĂ©es sur de plus longues distances chez les feuillus que chez les rĂ©sineux. Un gradient latitudinal uniforme reliĂ© au climat Ă©tait apparent pour le bouleau Ă papier et le peuplier faux-tremble. La distribution spatiale de ces mĂȘmes propriĂ©tĂ©s nâĂ©tait pas uniforme chez les rĂ©sineux, suggĂ©rant une adaptabilitĂ© environnementale plus restreinte en comparaison aux essences feuillues Ă©tudiĂ©es. Cette thĂšse prĂ©sente de grandes avancĂ©es dans le dĂ©veloppement dâune mĂ©thode dâinventaire de la qualitĂ© de la fibre au QuĂ©bec. La variabilitĂ© rĂ©gionale de la densitĂ© et de la rigiditĂ© du bois est maintenant connue pour les principales essences borĂ©ales du QuĂ©bec. Les prochains travaux porteront sur lâestimation de ces propriĂ©tĂ©s Ă lâĂ©chelle du peuplement forestier.The value of forest products from softwood stands depends on stems volume and taper, internal defects, but also on physical and mechanical wood properties, especially stiffness, since softwood lumber is primarily used for structural purposes. The lumber stiffness is evaluated in sawmills through visual or mechanical gradings. In forest, this knowledge does not exist and it is not possible to locate the regions or the forest stands with a high lumber stiffness, neither to evaluate the value of forest products and the economic profitability of forest management scenarios considering this key attribute. This lack of knowledge is mainly due to substantial investments associated with an inventory of wood fibre quality, which involves the sampling of thousands of trees and very demanding laboratory tests. It is in this context that the near-infrared spectroscopy was evaluated as a rapid, non-destructive method for estimating physical and mechanical wood properties. Ecogeographic variation in black spruce clear wood properties was first investigated for the two main vegetation types of the managed boreal forest of the province of Quebec (chapter 1). Wood growing in pure black spruce stands had longer mature fibers, a significantly denser wood with better mechanical characteristics than the wood growing in stands mixed with balsam fir. A scaling-up modeling approach, based on ring data from 3,350 inventory plots, has improved the performance of all models, explaining, at the stand level, 47%, 57%, 63% and 63% of variance in wood density, modulus of elasticity, microfibril angle and mature fiber length with estimated root mean square errors of 8.9 kg/mÂł, 0.52 GPa, 0.60° and 0.06 mm respectively. The potential of near-infrared spectroscopy to determine the transition from juvenile to mature wood in black spruce was then assessed (chapter 2). Good to excellent calibration statistics (RÂČ, ratio of performance to deviation) were obtained for basic density (0.85, 1.8), microfibril angle (0.79, 2.2), and modulus of elasticity (0.88, 2.9). Two-segment linear regressions were applied to microfibril angle profiles to determine the transition age. The values obtained using SilviScan data were compared with those obtained using near-infrared spectroscopy predicted data. The average transition age (23 years ± 7 years) was slightly underestimated by near-infrared spectroscopy with a mean prediction error (and 95% limits of agreement) of -2.2 ± 6.3 years (-14.6/10.1). These results suggest that the transition age from juvenile to mature wood could be predicted by near-infrared spectroscopy. Finally, the near-infrared spectroscopy was used for estimating the regional variation in wood density and stiffness for the main boreal species of Quebec (black spruce, balsam fir, jack pine, paper birch, trembling aspen) (chapter 3). An automated near-infrared system was developed for this purpose and calibrated using SilviScan data. Basic density and wood stiffness were estimated on 30,159 increment cores from 10,573 inventory plots. The observations in wood density and stiffness were spatially autocorrelated on longer distances in hardwoods than softwoods. A uniform latitudinal gradient related to climate was observed in paper birch and trembling aspen. Conversely, spatial distribution in wood density and modulus of elasticity was not uniform in softwoods, suggesting a more limited environmental adaptability in comparison to the hardwood species studied. This thesis has made major advances in the development of a method for inventorying wood fibre quality in Quebec. Regional variation in wood density and stiffness is now known for the main boreal species of Quebec. Future work will focus on estimating these properties at the forest stand level
Caractérisation de la proportion de bois d'aubier et de duramen chez le bouleau à papier (Betula papyrifera Marsh.)
Cette Ă©tude vise Ă caractĂ©riser les proportions de bois dâaubier et de duramen chez le bouleau Ă papier (Betula papyrifera Marsh.) en relation avec les caractĂ©ristiques du feuillage, de la cime et de lâarbre. Les rĂ©sultats indiquent que la proportion dâaubier est significativement reliĂ©e au feuillage, selon la thĂ©orie du modĂšle tubulaire. Dâautre part, la probabilitĂ© de prĂ©sence de duramen Ă hauteur de souche est plus Ă©levĂ©e pour des arbres Ă fort dĂ©filement. Les proportions dâaubier et de duramen sont Ă©galement dĂ©pendantes de lâĂąge de lâarbre. En outre, le dĂ©veloppement vertical du duramen Ă lâintĂ©rieur de la tige semble ĂȘtre affectĂ© par lâeffet dâempattement et par la base de la cime vivante. Le duramen prĂ©sente une valeur maximale Ă une hauteur relative de 9% et dĂ©croĂźt par la suite. Finalement, la quasi-totalitĂ© du volume de duramen est situĂ©e sous la base de la cime vivante.This study aims to characterize sapwood and heartwood proportions in White Birch (Betula papyrifera Marsh.) in relation with foliage, crown and stem characteristics. The results indicate that sapwood proportion is significantly related to foliage following the pipe model theory. Furthermore, the probability of heartwood presence at stump height is higher for trees with high stem taper. Sapwood and heartwood proportions are also tree age dependant. In addition, the vertical development of heartwood within the stem seems to be affected by the stump effect and by the live crown base. Heartwood shows a maximum value at 9% relative tree height and decreases afterwards. Finally, almost all the heartwood volume is located under the live crown base
Movilidades y cambio urbano : BogotĂĄ, Santiago y SĂŁo Paulo
482 pĂĄginasEsta obra es fruto de una investigaciĂłn colectiva: el proyecto metal (âMetrĂłpolis
de América Latina en la mundialización: reconfiguraciones territoriales, movilidad
espacial, acciĂłn pĂșblicaâ), coordinado por Françoise Dureau y apoyado
financieramente por la ANR y la AIRD de 2007 a 2011 en el marco del programa
âLes Suds aujourdâhuiâ. Cinco equipos se asociaron a travĂ©s de convenios para
la realizaciĂłn del proyecto: la UMR 7301 Migrinter; la UMR 201 IRD-Universidad
de ParĂs I, DĂ©veloppement et sociĂ©tĂ©s; la UMR 6590 eso, Espaces et sociĂ©tĂ©s;
la UMR LPED, IRD-Universidad de Aix-Marseille; el CIDS de la Universidad Externado
de Colombia
Toucher lâinterface, interfacer le toucher
Cet article vise Ă monter lâimportance de lâinterface dans la comprĂ©hension du toucher. Nous commencerons tout dâabord par le dĂ©crire selon une approche phĂ©nomĂ©nologique. Le toucher est spĂ©cifiquement le sens de la proximitĂ©, de la soliditĂ©, et de la forme, faisant de celui-ci le sens de la prĂ©sence immĂ©diate. Ensuite, nous montrerons que le numĂ©rique est intouchable, car dâune part, il nâest pas une chose que lâon peut saisir avec les mains, dâautre part, il est constituĂ© de signes formels abstraits, enfin, il est inaccessible car protĂ©gĂ© par un copyright. Nous dĂ©montrerons alors que lâinterface permet de rĂ©soudre cette difficultĂ©. En tant que sousface constituĂ©e de symboles informatiques, elle touche la couche matĂ©rielle de lâordinateur; en tant quâinterface homme/machine, câest-Ă -dire surface, elle est touchable. Nous conclurons alors que nous ne touchons pas immĂ©diatement le numĂ©rique, et que le toucher est nĂ©cessairement mĂ©diat, remettant en cause la conception premiĂšre du toucher. Nous substituerons alors au terme de toucher celui de contact qui conserve lâidĂ©e de mĂ©diation. Nous distinguerons enfin le contact opĂ©rĂ© par lâinterface homme/machine qui capture, du contact humain qui caresse, câest-Ă -dire qui prend soin de maintenir autrui intouchable
Benjamin H. Bratton, Le Stack. Plateformes, logiciels et souveraineté
On ne peut que saluer la traduction partielle de cet ambitieux ouvrage du thĂ©oricien Benjamin Bratton. PrĂ©sentĂ© comme « hĂ©naurme » (p. 16) par Yves Citton, ce livre volumineux a Ă©tĂ©, en accord avec lâauteur, divisĂ© en deux volumes par UGA Ăditions. IntitulĂ© Le Stack. Plateformes, logiciels et souverainetĂ©, ce premier volet correspond ainsi â comme lâindique lâajout dans le sous-titre du terme plateformes â aux premiĂšre (The Models) et troisiĂšme (The Projects) parties de lâĂ©dition anglaise, da..
Regional variation in wood discoloration in paper birch trees
Wood discoloration was investigated in 721 paper birch trees from 146 sites across the managed forest of Quebec, Canada. Discoloration was present at breast height in 85% of trees, but its impact was limited in terms of tree basal area and volume, with proportions of 6.4% and 3.6%, respectively. These two measures were strongly correlated. Discoloration changed wood appearance but had no effect on microfibril angle and modulus of elasticity. Discolored wood was nevertheless denser, probably due to the accumulation of colored extractives. Predictive models were also developed and applied to 415,711 paper birch trees from 51,689 inventory plots across the province to study regional variation. Higher proportions of discolored basal area were obtained in the southwestern areas of the province where the climate is warmer and drier. In these areas, paper birch trees are larger and, likely, support bigger branches which can cause larger columns of discoloration when broken. Lower proportions were found in eastern regions where snowfall is more abundant. Smaller, more flexible branches in trees growing in these areas could explain this result. This study confirms the feasibility of large-scale mapping of wood discoloration in standing trees based on forest inventory and climate data.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Emotion Feedback during Computer-Mediated Collaboration: Effects on Self-Reported Emotions and Perceived Interaction
Emotions play a crucial role in collaboration. They help to make inferences about the partner and can strongly influence task performance. Due to limitations of emotional cues in computer-mediated collaboration (CMC), the collaborative process can be impacted. In this study, we report on the effect of an Emotion Awareness Tool (EAT) designed to facilitate the sharing of emotions between partners, on the perceived emotions after collaboration and the perceived quality of the interaction. Results showed that the EAT stimulated participants to engage in a mutual modeling of emotions. In the EAT condition, the perceived amount of time spent on emotion modeling process was positively correlated to the perceived intensity of positive emotions after collaboration. The EAT increased the perceived degree of transactivity, but only for women. This study provides a first step in exploring the effect of emotion awareness in CMC tasks including a comparing approach for its gender-specific relevance
Modeling black spruce wood fiber attributes with terrestrial laser scanning
International audienceA model comparison approach, based on the Akaikeâs information criterion, was used to evaluate the contribution of terrestrial laser scanning (TLS) to the estimation of wood fiber attributes at the tree level for black spruce (Picea mariana (Mill.) B.S.P.) trees growing in Newfoundland, Canada. Substantial efforts were made to acquire, process, and develop accurate and detailed metrics of the tree, its crown, and its immediate environment. Based on the resulting data set, significant relationships were found, and models were successfully developed, using only TLS metrics, for predicting wood fiber attributes. The models accounted for 47%, 33%, 51%, 44%, and 52% of variance in wood density, coarseness, fiber length, microfibril angle, and modulus of elasticity respectively, with root mean square error values of 46 kg/m3, 37 ”g/m, 0.20 mm, 3.5 Âș, 2.3 GPa. Our ability to estimate the wood fiber attributes was improved by combining TLS metrics with conventional field measurements. This study demonstrates that the use of TLS metrics improves the estimation of the wood fiber attributes at the tree level beyond that possible with conventional field measurements
Feedback émotionnel et collaboration médiatisée par ordinateur : Quand la perception des interactions est liée aux traits émotionnels
Nous nous interrogeons sur la relation entre les caractĂ©ristiques Ă©motionnelles des individus et la façon dont ils perçoivent la qualitĂ© des Ă©changes avec leur partenaire au cours d'une tĂąche de conception collaborative Ă distance. Nous nous demandons Ă©galement dans quelle mesure un outil de feedback Ă©motionnel, permettant le partage des Ă©motions pendant la collaboration, peut modifier la relation entre traits Ă©motionnels et perception des interactions. Dans la condition sans feedback Ă©motionnel, la perception des interactions est liĂ©e Ă la capacitĂ© des coĂ©quipiers Ă extĂ©rioriser leurs Ă©motions. Dans la condition oĂč les coĂ©quipiers reçoivent des informations sur les Ă©motions de leur partenaire, la qualitĂ© perçue des interactions est liĂ©e Ă la contagion Ă©motionnelle. Plus les coĂ©quipiers ont tendance Ă synchroniser leurs Ă©motions Ă celles de leur partenaire, et plus ils perçoivent les interactions comme convergentes et co-constructives