LIFE CYCLE ASSESSMENT OF A HEMP CONCRETE WALL: IMPACT OF THICKNESS AND COATING.

International audienceIn a context of sustainable development and energy sparing, a life cycle assessment (LCA) may be useful to make good choices. Thus, this study concerns the LCA of an environmentally friendly material used for building construction, hemp concrete. The functional unit is first defined per square such that the wall may provide the function of bearing wall meter and its thermal performance is described by a thermal resistance of 2.78 m².K/W. The results then showed that the production phase of raw materials is mainly responsible for the environmental impact of the wall, mostly due to the binder production. It was also shown that, compared to traditional construction materials, hemp concrete has a low impact on environment. Moreover, hemp concrete contributes to reduce climate change as photosynthesis-mediated carbon sequestration and carbonation serve to reduce atmospheric carbon dioxide. A sensitivity analysis is performed on three criteria: wall thickness, renewal of coatings and compounds of the indoor coating. Our results show that environmental indicators evolve with wall thickness, except for the climate change indicator. It improves with thickness due to carbon sequestration and carbonation. Moreover the increase in the wall's thermal resistance with wall thickness is not taken into account in such an LCA performed at the material level. The renewal of coating slightly impacts the environmental indicator for small numbers of renewals but it leads to negative effects if they are too numerous. It appears that hemp-lime coating has a greater impact than sand-lime coating as it embeds more binder

L’évaluation dans les rapports de signalement

Les énoncés concessifs relevés dans les rapports de signalement d’enfant en danger apparaissent comme des lieux privilégiés pour observer les modalités particulières de l’activité d’évaluation des scripteurs. L’article tente de montrer comment ces énoncés produisent des distinctions entre les propriétés qu’ils attribuent aux objets qu’ils évaluent (comportements, logement, situation familiale, situation scolaire, etc.) et configurent ainsi la notion de danger.The concessive statements noted in the descriptive reports signalling children in danger appear to be privileged settings in which to observe the particular modalities of the activity of evaluating scripture. This first approach attempts to demonstrate how these statements produce distinctions between the characteristics that they attribute to the discursive objects they are evaluating (behavior, housing, family circumstances, academic standing, etc.) thereby configuring the value system on which the evaluation is set

L’évaluation dans les rapports de signalement

Les énoncés concessifs relevés dans les rapports de signalement d’enfant en danger apparaissent comme des lieux privilégiés pour observer les modalités particulières de l’activité d’évaluation des scripteurs. L’article tente de montrer comment ces énoncés produisent des distinctions entre les propriétés qu’ils attribuent aux objets qu’ils évaluent (comportements, logement, situation familiale, situation scolaire, etc.) et configurent ainsi la notion de danger.The concessive statements noted in the descriptive reports signalling children in danger appear to be privileged settings in which to observe the particular modalities of the activity of evaluating scripture. This first approach attempts to demonstrate how these statements produce distinctions between the characteristics that they attribute to the discursive objects they are evaluating (behavior, housing, family circumstances, academic standing, etc.) thereby configuring the value system on which the evaluation is set

Towards Skeleton based Reconstruction : From Projective Skeletonization to Canal Surface Estimation

International audienceWe present a novel approach to reconstruct a 3D object from images corresponding to two different viewpoints: we estimate the skeleton of the object instead of its surface. The originality of the method is to be able to reconstruct a tubular object with a limited number of input images. Unlike classical reconstruction methods, like multi-view stereo or more recently structure-from-motion, this approach does not rely on interest points but estimates the topology of the object and derives its surface. Our contribution are twofold. First, given two perspective images of the 3D shape, the projection of the skeleton is computed in 2D. Secondly the 3D skeleton is reconstructed from the two projections using triangulation and matching. A mesh is finally derived for each skeleton branch

Caractérisation de la projection du squelette d'une surface canal 3D : Application à la reconstruction 3D à partir de deux images

International audienceNous présentons dans cet article une nouvelle approche pour reconstruire un objet 3D à partir de deux images de celui-ci. L'originalité de notre approche vient du fait que nous n'estimons pas directement la surface de l'objet 3D mais son squelette. Ce travail s'appuie sur les deux contributions suivantes. Premièrement, nous décrivons la relation existant entre un squelette 3D et sa projection, orthographique ou perspective, sur un plan image. Ensuite, nous montrons comment retrouver le squelette 3D à partir de deux de ses projections. Contrairement aux méthodes de reconstruction 3D classiques qui génèrent un nuage de points sans maillage, cette approche a pour avantage de reconstruire aussi la topologie de l'objet, c'est-à-dire d'en retrouver un maillage sans traitement annexe. Nous traitons ici des objets représentables par un squelette 3D curviligne et nous supposons aussi que les points de vue sont calibrés

Functional traits help predict post-disturbance demography of tropical trees

How tropical tree species respond to disturbance is a central issue of forest ecology, conservation and resource management. We define a hierarchical model to investigate how functional traits measured in control plots relate to the population change rate and to demographic rates for recruitment and mortality after disturbance by logging operations. Population change and demographic rates were quantified on a 12-year period after disturbance and related to seven functional traits measured in control plots. The model was calibrated using a Bayesian Network approach on 53 species surveyed in permanent forest plots (37.5 ha) at Paracou in French Guiana. The network analysis allowed us to highlight both direct and indirect relationships among predictive variables. Overall, 89% of interspecific variability in the population change rate after disturbance were explained by the two demographic rates, the recruitment rate being the most explicative variable. Three direct drivers explained 45% of the variability in recruitment rates, including leaf phosphorus concentration, with a positive effect, and seed size and wood density with negative effects. Mortality rates were explained by interspecific variability in maximum diameter only (25%). Wood density, leaf nitrogen concentration, maximum diameter and seed size were not explained by variables in the analysis and thus appear as independent drivers of post-disturbance demography. Relationships between functional traits and demographic parameters were consistent with results found in undisturbed forests. Functional traits measured in control conditions can thus help predict the fate of tropical tree species after disturbance. Indirect relationships also suggest how different processes interact to mediate species demographic response. (Résumé d'auteur

Avez-vous dit « autorité » ? Les défis de l’interdépendance positive dans le cadre de l’enseignement des sciences à l’école secondaire

Concernant l’éducation scientifique, le gouvernement du Québec insiste sur la nécessité d’agir en interdépendance et de privilégier le travail de groupe dans des classes hétérogènes du secondaire. Or, l’acte d’enseigner est très complexe. Les enseignants sont conviés à des changements majeurs sur le plan des attitudes et des comportements. Leur autorité dépend de plus en plus de l’adoption d’un contrat pédagogique fondé sur l’interdépendance positive entre eux et leurs élèves.On the subject of scientific education, the Government of Quebec insists on the need for acting in interdependence and for privileging group interventions in secondary schools and heterogeneous classes. However, the act of teaching is very complex. The science teachers are invited to major changes in their attitudes and behaviors. Their authority depends more and more on the adoption of an educational contract based on positive interdependence between them and their students