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L’oeil synthétique de la machine : la perception temporelle des systèmes de capture de mouvement (MOCAP)
Get PDFEn proposant une solution utilisant certains procédés issus des technologies de l'intelligence artificielle Open Source pour la capture de mouvement, ce mémoire examine certains paramètres qui définissent les performances de la vision artificielle synthétique, notamment les mécanismes d'apprentissage et la latence. Dans le contexte actuel de la prolifération de nouveaux métavers, reproduire la capture de mouvement de l'oeil et la synthétiser avec un ordinateur nécessite des connaissances dans les sous-domaines de la vision par ordinateur tels que l'apprentissage automatique, l'intelligence artificielle, le traitement du transfert de données et l'animation 3D. C'est en étudiant les paramètres de la latence que nous avons hypothétiquement établi que ce champ de recherche converge vers une seule et grande question : Dans les systèmes de capture de mouvement industriels, comment fonctionne, sur le plan temporel, l’oeil de la machine? Basée principalement sur l'analyse des technologies de la production virtuelle les plus utilisées, la solution Open Source proposée dans le cadre de ce mémoire permet de pointer et de mieux évaluer certaines limites du système perceptif informatique par rapport aux solutions existantes. En définitive, ce sont les dimensions qualitatives de la vision humaine qui devraient prédominer sur les systèmes de mesure de la vision et du mouvement par ordinateur. C'est le point de départ des démarches industrielles dont les objectifs reposent d’abord et avant tout sur la production d'effets narratifs
Validation of the Body Appreciation Scale-2 in cisgender, heterosexual and sexual and gender minority adolescents and sexuality-related correlates
Get PDFBody dissatisfaction has received considerable scientific attention, while research about positive body image has been neglected, particularly among adolescents. The aims of the present study were to examine (1) the factor structure of the Body Appreciation Scale-2 (BAS-2) in a large sample of cisgender, heterosexual and sexual and gender minority adolescents, (2) measurement invariance across language, gender and sexual orientation-based groups, (3) convergent validity with sexuality-related outcomes and (4) one-year temporal stability. Results of a confirmatory analysis among 2419 adolescents (Mage=14.6 years, SD=0.62; 52.6% girls) corroborated the proposed one-dimensional factor structure of the scale. The BAS-2 demonstrated adequate reliability and one-year temporal stability. The scale was partially invariant across gender and fully invariant across language and cisgender heterosexual and sexual and gender minority adolescents. Boys (cis and trans) had higher levels of body appreciation than girls (cis and trans), while no significant differences were observed between heterosexual and sexual minority adolescents. The BAS-2 correlated positively with sexual satisfaction and sexual body-esteem as well as negatively with sexual distress. Our findings support the validity and reliability of the BAS-2 in French and English for measuring body appreciation in adolescents
Chapter 19: Governance of extractive industries
Get PDFMarred with intricate socio-environmental problems, human rights abuses and disproportionate impacts on marginalized communities, including indigenous peoples, extractive industries (EI)-led development has often disappointed. This chapter asks whether 'better' governance is the panacea for EI to spearhead development in the Global South and if so, how. We argue that the 'Modes of Governance' approach offers the most useful perspective. Nested within heterodox political economy, this approach emphasizes the need to take into account the structural relations of power and authority, as well as the plurality of actors that have a significant influence on the investment environment for the sector and the norms which regulate it. The chapter first provides an overview of EI development in the Global South. It then details how, over the past three decades, different analysts have identified 'governance' as a key variable while significantly disagreeing on how to define this intricate concept. Building on the Modes of Governance approach, we then turn to the analysis of key contemporary debates over EI. We conclude that neo-liberalism and the externally driven nature of EI and governance reforms in the Global South have profoundly constrained the capacity of the state to make economic and socio-environmental decisions around EI
Modélisation mathématique de la formation d'agrégats et de la dissolution de l'alumine dans le bain d'électrolyse
Get PDFPour l’industrie de l’aluminium, la compréhension de l’injection à la dissolution de l’alumine dans le bain électrolytique est critique pour identifier le point optimal des conditions d’opération. De l’injection à la complète dissolution, plusieurs mécanismes physiques et chimiques interagissent : mécanique des solides et des fluides, transfert de chaleur, changement de phase et dissolution. Le modèle mathématique présenté dans cette thèse utilise la méthode des éléments discrets (DEM) pour considérer la poudre d’alumine solide sous la forme d’un matériau granulaire. Il est couplé à la méthode « hydrodynamique des particules lissées (SPH) pour simuler le liquide électrolytique. Dans l’optique d’accélérer le calcul, le simulateur utilise les cartes graphiques pour utiliser le potentiel du calcul parallèle. Le modèle permet également le calcul du transfert thermique et la formation de l’agrégat lié au frittage de l’alumine. De plus, le changement de phase est intégré au modèle pour considérer l’effet de la solidification du bain sur la formation du radeau. Finalement, le rythme de dissolution de l’alumine est calculé localement selon les conditions présentes. Une analyse des résultats de ces effets combinés permet de mettre en évidence les pistes d’amélioration du processus et des conditions d’injection de l’alumine. Le développement d’un modèle nécessite plusieurs validations pour calibrer le modèle. Les expériences de validations sont divisées en deux méthodologies : le développement de validation avec des expériences analogues à basse température et des validations d’injection sous des conditions rapprochées des conditions industrielles (alumine + bain en fusion). La faciliter d’approche des modèles analogues permet d’apporter une meilleure compréhension des phénomènes physiques présents lors de l’injection d’un matériau granulaire dans un liquide. Ces validations consistent en l’injection de graines de moutarde refroidies à l’azote liquide dans l’eau pour observer la mécanique des solides et des fluides, le transfert thermique et le changement de phase. Certaines validations à basse température sont aussi réalisées avec des échantillons de sel pour étudier les liens entre le transfert thermique, le changement de phase et la dissolution. Ces validations utilisent plusieurs technologies pour observer les phénomènes : caméra haute vitesse, imagerie schlieren et vélocimétrie par images de particules. Pour effectuer les validations à haute température, la température de la surface supérieure du radeau a été suivie avec une caméra thermique suivant l’injection dans le bain électrolytique. Dans d’autres cas, il y a eu repêchage des radeaux pour permettre de faire une analyse visuelle de ses propriétés. À la suite du développement du modèle et de la validation, une simulation de référence a été établie utilisant plusieurs paramètres correspondant aux validations, ou bien à des conditions typiques de l’industrie. Ce cas a permis d’identifier certains comportements typiques de l’ensemble du processus. Subséquemment, une étude paramétrique est réalisée pour analyser l’influence de ces paramètres sur la formation du radeau d’alumine. Les résultats permettent de mettre en évidence les paramètres d’entrée qui ont la plus forte influence sur le processus de dissolution d’alumine tout en offrant une explication détaillée concernant les conséquences observées suite à la modification de chacun des paramètres étudiés, que ce soit: la variation de surface de contact alumine-bain, la quantité de bain solidifié ou principalement, le rythme de dissolution d’alumine.
For primary aluminum producers, understanding each step of alumina feedings is critical to reach optimal process conditions. From the injection of the powder to its complete dissolution, several physical and chemical mechanisms are interacting: solid and fluid mechanics, heat transfer, phase change and dissolution. The mathematical model presented in this thesis uses the discrete element method (DEM) to consider the solid alumina powder as an individual particle. It is coupled to the "smoothed particle hydrodynamics" (SPH) method to simulate the liquid electrolyte. In order to decrease the computational time, the simulator uses graphics cards to use the benefits of parallel computing. The model is also used to calculate the heat transfer and coalescence of solid materials resulting from alumina sintering. Then, phase change is integrated into the model to consider the cohesion effect caused by bath. Consecutively, the dissolution rate of alumina particles is calculated locally for each respective set of conditions. A detailed study of the combined effect of these mechanisms will lead to enhanced injection conditions leading to improved alumina dissolution in electrolysis cells. The development of a model requires several validations to tune the model. Validation experiments are divided into two methodologies: validation development with analogous low temperature experiments and alumina injection validations at high temperature. The versatility offered from analogue validations provides deeper understanding of the physical phenomena in effect during the injection of a granular material into a liquid. The setup used consists of injecting mustard seeds cooled with liquid nitrogen into water to observe solids and fluids mechanics, heat transfer and phase change. Low temperature validations were also carried out with salt samples to study the interactions between heat transfer, phase change and dissolution. Several technologies were used to observe these phenomena: high-speed camera, schlieren imaging and particle image velocimetry. High-temperature validations were performed while injecting alumina into electrolytic bath. Under a controlled environment, the temperature of the upper surface of the generated raft was monitored using an infrared camera. In other experiments, the raft itself was collected after a specific time to perform a visual analysis of its structure. Following the development of the model and the validations, a reference scenario was used using parameters corresponding to the validations and typical industrial values. This scenario can pinpoint the expected behaviour during the injection and dissolution process. Finally, a parametric study is carried out to analyze the influence of input parameters on the formation of the alumina raft. The results make it possible to highlight the parameters with the upmost effect on the process, which pave forward potential applications for further optimization of the dissolution of alumina, whether it is by enhancing the surface contact between the alumina and the bath, or reducing the amount of solidified bath, in order to directly improve the alumina dissolution rate
Upscaling xylem phenology : sample size matters
No full textBackground and Aims : Upscaling carbon allocation requires knowledge of the variability at the scales at which
data are collected and applied. Trees exhibit different growth rates and timings of wood formation. However, the factors explaining these differences remain undetermined, making samplings and estimations of the growth dynamics a complicated task, habitually based on technical rather than statistical reasons. This study explored the variability in xylem phenology among 159 balsam firs [Abies balsamea (L.) Mill.].
Methods : Wood microcores were collected weekly from April to October 2018 in a natural stand in Quebec, Canada, to detect cambial activity and wood formation timings. We tested spatial autocorrelation, tree size and cell production rates as explanatory variables of xylem phenology. We assessed sample size and margin of error for wood phenology assessment at different confidence levels.
Key Results : Xylem formation lasted between 40 and 110 d, producing between 12 and 93 cells. No effect of spatial proximity or size of individuals was detected on the timings of xylem phenology. Trees with larger cell production rates showed a longer growing season, starting xylem differentiation earlier and ending later. A sample size of 23 trees produced estimates of xylem phenology at a confidence level of 95 % with a margin of error of 1 week.
Conclusions : This study highlighted the high variability in the timings of wood formation among trees within an area of 1 km2. The correlation between the number of new xylem cells and the growing season length suggests a close connection between the processes of wood formation and carbon sequestration. However, the causes of the observed differences in xylem phenology remain partially unresolved. We point out the need to carefully consider sample size when assessing xylem phenology to explore the reasons underlying this variability and to allow reliable upscaling of carbon allocation in forests
Warming-induced increase in carbon uptake is linked to earlier spring phenology in temperate and boreal forests
Get PDFUnder global warming, advances in spring phenology due to rising temperatures have been widely reported. However, the physiological mechanisms underlying the advancement in spring phenology still remain poorly understood. Here, we investigated the effect of temperature during the previous growing season on spring phenology of current year based on the start of season extracted from multiple long-term and large-scale phenological datasets between 1951 and 2018. Our findings indicate that warmer temperatures during previous growing season are linked to earlier spring phenology of current year in temperate and boreal forests. Correspondingly, we observed an earlier spring phenology with the increase in photosynthesis of the previous growing season. These findings suggest that the observed warming-induced earlier spring phenology is driven by increased photosynthetic carbon assimilation in the previous growing season. Therefore, the vital role of warming-induced changes in carbon assimilation should be considered to accurately project spring phenology and carbon cycling in forest ecosystems under future climate warming
A critical thermal transition driving spring phenology of Northern Hemisphere conifers
No full textDespite growing interest in predicting plant phenological shifts, advanced spring phenology by global climate change remains debated. Evidence documenting either small or large advancement of spring phenology to rising temperature over the spatio-temporal scales implies a potential existence of a thermal threshold in the responses of forests to global warming. We collected a unique data set of xylem cell-wall-thickening onset dates in 20 coniferous species covering a broad mean annual temperature (MAT) gradient (−3.05 to 22.9°C) across the Northern Hemisphere (latitudes 23°–66° N). Along the MAT gradient, we identified a threshold temperature (using segmented regression) of 4.9 ± 1.1°C, above which the response of xylem phenology to rising temperatures significantly decline. This threshold separates the Northern Hemisphere conifers into cold and warm thermal niches, with MAT and spring forcing being the primary drivers for the onset dates (estimated by linear and Bayesian mixed-effect models), respectively. The identified thermal threshold should be integrated into the Earth-System-Models for a better understanding of spring phenology in response to global warming and an improved prediction of global climate-carbon feedbacks
Women with breast cancer’s perceptions of nurse-led telephone-based motivational interviewing consultations to enhance adherence to adjuvant endocrine therapy: a qualitative study
No full textBackground: Daily adjuvant endocrine therapy (AET) for 5 or 10 years is the standard of care for women diagnosed with non-metastatic hormone receptor-positive breast cancer. However, many women experience AET-related issues that may hamper quality of life and adherence. Here, we aimed to describe women's perceptions of motivational interviewing (MI)-guided consultations delivered by a trained nurse navigator over the telephone to enhance AET adherence.
Methods: Eighteen women who were first prescribed AET for non-metastatic breast cancer in the last 5 years, who self-reported AET-related issues, and who participated in at least two MI-guided consultations over a year were interviewed about their perceptions of the intervention, using a semi-structured interview guide. Audio recordings were transcribed verbatim and analyzed using a thematic analysis approach.
Results: Three main themes emerged from the data about women's perceptions on MI-guided consultations. These consultations were described as (1) a person-centred experience, (2) providing key information about AET, and (3) supportive of present and future AET experience, by contributing to AET side-effect management, motivation, adherence, calming negative emotions, improving well-being and self-esteem, and making women to feel empowered.
Conclusions: Nurse-led telephone-based MI-guided consultations about AET were found to respond to participants' needs and to enhance participants' perceptions of being informed and being supported in experiencing various facets of AET. Telephone-based consultations for AET are perceived as a promising strategy in an increasing virtual care world
Photoacclimation and light thresholds for cold temperate seagrasses
Get PDFWater quality deterioration is expected to worsen the light conditions in shallow coastal waters with increasing human activities. Temperate seagrasses are known to tolerate a highly fluctuating light environment. However, depending on their ability to adjust to some decline in light conditions, decreases in daily light quantity and quality could affect seagrass physiology, productivity, and, eventually, survival if the Minimum Quantum Requirements (MQR) are not reached. To better understand if, how, and to what extent photosynthetic adjustments contribute to light acclimation, eelgrass (Zostera marina L.) shoots from the cold temperate St. Lawrence marine estuary (Rimouski, QC, Canada) were exposed to seven light intensity treatments (6, 36, 74, 133, 355, 503, and 860 μmol photons m–2 s–1, 14:10 light:dark photoperiod). Photosynthetic capacity and efficiency were quantified after five and 25 days of light exposure by Pulse Amplitude Modulated (PAM) fluorometry to assess the rapid response of the photosynthetic apparatus and its acclimation potential. Photoacclimation was also studied through physiological responses of leaves and shoots (gross and net primary production, pigment content, and light absorption). Shoots showed proof of photosynthetic adjustments at irradiances below 200 μmol photons m–2 s–1, which was identified as the threshold between limiting and saturating irradiances. Rapid Light Curves (RLC) and net primary production (NPP) rates revealed sustained maximal photosynthetic rates from the highest light treatments down to 74 μmol photons m–2 s–1, while a compensation point (NPP = 0) of 13.7 μmol photons m–2 s–1 was identified. In addition, an important package effect was observed, since an almost three-fold increase in chlorophyll content in the lowest compared to the highest light treatment did not change the leaves’ light absorption. These results shed new light on photosynthetic and physiological processes, triggering light acclimation in cold temperate eelgrass. Our study documents an MQR value for eelgrass in the St. Lawrence estuary, which is highly pertinent in the context of conservation and restoration of eelgrass meadows