HAL Université de Savoie
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Enhancing stainless steel activity for the Oxygen Evolution Reaction in Alkaline Electrolyte using Co3O4 spinel deposition
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High-coercivity HRE-free Nd-Fe-B magnets by laser powder bed fusion
No full textInternational audienceAdditively manufactured NdFeB permanent magnets with no Heavy Rare Earth (HRE) such as Dy and Tb were fabricated by Laser Powder Bed Fusion (LPBF). As-built samples exhibited relative densities up to 97 % and magnetic properties up to Br = 0.667 T, H = 1173 kA.m and (BH) = 59.4 kJ.m. After an adequate annealing, a substantial increase of the magnetic properties up to Br = 0.691 T, H = 1443 kA.m and (BH) = 77.9 kJ.m was achieved. These magnets have been elaborated using a specific powder fabricated with an in-house experimental pilot line allowing the possibility to adapt both the size (in the case of this study a narrowly-distributed powder with a volumetric D50 of 40 μm) and the chemical composition of the material as desired. The microstructure of the printed magnets has been investigated and is shown to be mainly constituted of untextured submicronic magnetic Nd2Fe14B grains surrounded by an intergranular Nd rich phase, the same phases as reported in standard sintered magnets but with an average grain size several times smaller. Due to the presence of the Nd rich intergranular phase, the obtained intrinsic coercivity is significantly higher than the one reported in studies of the literature working on LPBF with a commercial MQP S powder. Nanosized Nd-rich oxide inclusions are often observed within the NdFeB grains. It is suggested that these Nd-rich oxide inclusions could act as nucleants for the Nd2Fe14B grains during the solidification process
Fatigue et déclin de la démarche dans la paralysie cérébrale de l'adulte : déterminants physiopathologiques et apport d'une activité physique ciblée
No full textThe objectives of this thesis were to investigate the effects of ageing amongst adults with Cerebral Palsy (CP) compared to a Typically Developed (TD) control population. First, we aimed to understand the effect of ageing from early adulthood and onwards through a narra-tive review of the literature. Here we found that a large proportion of adults with all degrees of cerebral palsy severity will experience a palpable decline in mobility and walking perfor-mance around their third to fifth decade of life. This appears to stem from various factors such as comorbidities, alterations to the neuromuscular and cardiovascular system and changes in environment. Secondly, we aimed to quantify differences between young and older adults with cerebral palsy on measures pertaining to walking performance. This was achieved through a four-day study protocol in which each participant completed an array of tests related to mo-bility and walking performance. The protocol can be subdivided into three themes or articles, the first on general measures of walking performance. In this theme, we explored walking re-lated parameters such as cardiopulmonary capacity, strength, walking performance in clinical tests, the cost of locomotion and self-reported measures pertaining. The second theme con-cerned fatigability (the acute reduction in functional capacity following a given workload) and was investigated using an adapted bike-ergometer allowing for neuromuscular assessments. The third theme concerned quantification of gait through the use of an instrumented gait anal-ysis in which 46 markers were attached to the lower limbs and monitored during normal walk-ing. The results indicate that older adults with CP exhibit lower walking performance, strength, voluntary activation and endurance compared to younger counterparts. When com-paring adults with CP to TD peers, only older adults with CP showed a deterioration in mobil-ity and walking performance, younger adults with CP are not, in our sample, significantly dif-ferent. The thesis is not powered to infer relationships between singular factors and their ef-fect on walking performance, but may guide future research and physiotherapy strategies to-wards improving or maintaining walking performance through a focus on, for example power, balance and improving cost of walking.L'objectif de cette thèse était d'étudier les effets du vieillissement chez les adultes atteints pa-ralysie cérébrale (CP) par rapport à une population témoin au développe typiquement (TD). Tout d'abord, nous avons cherché à comprendre l'effet du vieillissement à partir du début de l'âge adulte à travers une revue narrative de la littérature. Nous avons constaté qu'une grande proportion d'adultes atteints de paralysie cérébrale à tous les degrés de gravité connaîtra un déclin palpable de la mobilité et de la marche entre la troisième et la cinquième décennie de leur vie. Ce phénomène semble résulter de divers facteurs tels que les comorbidités, les altéra-tions du système neuromusculaire et cardiovasculaire et les changements d’environnement d’habituelle. Apres, nous avons cherché à quantifier les différences entre les jeunes adultes (18-25 ans) et les adultes plus âgés (35-50 ans) atteints de paralysie cérébrale en ce qui con-cerne les mesures relatives à la performance de la marche. Pour ce faire, nous avons mis en place un protocole d'étude de quatre jours au cours duquel chaque participant a effectué une série de tests liés à la mobilité et à la performance de la marche. Le protocole peut être subdi-visé en trois thèmes ou articles, le premier portant sur les mesures générales de la performance de marche. Dans ce thème, nous avons exploré les paramètres liés à la marche tels que la capa-cité cardio-pulmonaire, la force, la performance de la marche dans les tests cliniques, le coût de la marche et les mesures auto-rapportées. Le deuxième thème concernait la fatigabilité (la réduction aiguë de la capacité fonctionnelle à la suite d'une charge de travail) et a été étudié à l'aide d'un vélo-ergomètre adapté permettant des évaluations neuromusculaires. Le troisième thème concernait la quantification de la marche par l'utilisation d'une analyse instrumentée de la marche dans laquelle 46 marqueurs ont été fixés aux membres inférieurs et surveillés pen-dant la marche normale. Les résultats indiquent que les adultes plus âgés atteints de CP pré-sentent des performances de marche, une force, une activation volontaire et une endurance inférieure à celles de leurs homologues plus jeunes. Lorsque l'on compare les adultes atteints de CP à leurs pairs TD, seuls les adultes âgés atteints de CP ont montré une détérioration de la mobilité et des performances de marche, les adultes plus jeunes atteints de PC n'étant pas, dans notre échantillon, significativement différents. La thèse ne permet pas de déduire des relations entre des facteurs singuliers et leur effet sur les performances de marche, mais elle peut orienter les recherches futures et les stratégies de physiothérapie vers l'amélioration ou le maintien des performances de marche en mettant l'accent, par exemple, sur la puissance, l'équi-libre et l'amélioration du coût de la marche
Porosity Analysis of Mortars Incorporating Glass Powder and Coffee Grounds Using X-Ray Tomography
No full textInternational audienceThe production of concrete is a sector with a high environmental impact, particularly due to CO₂ emissions associated with cement manufacturing. At the same time, waste management, particularly of bottle glass, exacerbates the environmental situation. When they are not recycled or reused, these materials are often sent to landfills. The decomposition of certain elements can generate significant pollution contaminating soils and groundwater. In the face of these challenges, using waste materials such as glass powder and coffee grounds presents a promising solution, combining ecological benefits with technical performance. This study aims to assess the effect of partially replacing cement with glass powder (at rates of 5, 10, 15, 20, and 25%) and coffee grounds (at rates of 2, 3, and 5%) on the porosity characteristics of mortars. The porosity of the prepared samples was quantified through post-treatment with DragonFly 3D software of images obtained by X-ray tomography. The results obtained show that mortars incorporating glass powder have a porosity 50% lower than that of the control mortar, without addition. This indicates that the addition of glass does not degrade the microstructure of the material. This is not the case with coffee grounds since the latter increases the porosity of the mortars as its percentage (a maximum of 3.4%).On the other hand, a reduction in water absorption is observed in mortars containing glass powder, with a more pronounced decrease at high substitution rates. This behavior indicates that glass contributes to densifying the mortar matrix, thus limiting water propagation and potentially increasing its strength. Again, coffee grounds lead to an inverse reaction; the insertion of coffee grounds leads to an increase in water absorption. This phenomenon is more pronounced with a 5% coffee grounds content. Thus, it appears relevant to continue research on the use of glass powder and coffee grounds in cementitious materials
Energy Justice in Latin America. Towards energy justice in Argentina. Learning from inclusion experiences
No full textInternational audienceIn Argentina, despite the extension of electricity and natural gas networks, a portion of its population and territories still lack access to adequate energy services. 700,000 inhabitants use firewood for cooking (1.5% of total population), according to data from the 2022 national census (INDEC, 2022).1 These situations are considered energy poverty (Ise et al., 2020; Ayroles, 2019; Ayroles and Forget,2022). Lack of access to energy networks is not a trustworthy indicator of poverty. There are satisfactory services in places without networks and regions with energy deficits despite the existence of energy infrastructure (Jacinto et al., 2019). The differences in energy availability are linked to spatial disparities. Urban areas experienced faster improvements in the expansion of energy networks, while rural and isolated regions often faced accessibility and cost challenges in expanding the services (Haesbaert, 1995; Clementi et al., 2014). However, people with inadequate connections to the networks and/or who are unable to meet their energy needs are also found in urban settings, as a result of low economic resources, inappropriate spatial expansion, lack of service provision planning and infrastructure deficits. Many people struggle to pay energy bills and seek, therefore, informal and unsafe alternatives (Techo, 2016). Others, located in some provinces of the country, pay considerably larger bills for energy services than inhabitants of the capital city, Buenos Aires. Examples of these situations will be explored in the following sections of the chapter
Low-loaded catalyst layers for proton exchange membrane fuel cell dynamic operation Part 2: Modeling study
No full textInternational audienceAbstract The interplay between i) cathodic electrocatalytic layer (EC layer) features of proton exchange membrane fuel cell (PEMFC), focusing on the oxygen reduction reaction (ORR) electrocatalyst (EC) and the Pt loading; and ii) the PEMFC performance and durability is evaluated. An innovative hierarchical “core–shell” carbon nitride multimetallic ORR electrocatalyst ( “PtCuNi/C” H‐EC) is compared with a conventional Pt/C benchmark. The various contributions to PEMFC performance at beginning of test (BOT) are isolated and correlated to the physicochemical features of the ORR EC and the cathodic EC layer. The PEMFC durability is investigated extensively via accelerated stress tests (ASTs) mimicking long‐term operation. Particular attention is dedicated to determine how ageing affects: i) PEMFC cell voltage; and ii) the cathode electrochemically active surface area (ECSA). “Post‐mortem” studies are carried out to probe how ageing influences the cathodic EC layer features, including: i) chemical composition; ii) elements distribution; iii) EC morphology; and iv) structure and crystal size of the Pt‐based metal nanoparticles bearing the active sites. Integrating the experimental results allows to identify both the positive and the detrimental effects triggered by the introduction of transition metals (TMs) in the ORR EC on the factors modulating PEMFC performance and long‐term operation
Indoor air treatment of formaldehyde by N-enriched activated carbon beads with or without CuO/Cu supported nanoparticles
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The failure of the theory of "happy globalization" and the return to a mercantilist race for global economic, technological, and civilizational leadership
No full textInternational audienceFollowing the collapse of the Soviet-style managed economic system, Francis Fukuyama predicted the “End of history”, with a supposed monopoly of ideological liberalism and democracy - a new version of Adam Smith's “invisible hand” - as the only possible means of promoting growth, development and peace. In reality, armed conflicts in their various forms have not ceased. International terrorism, civil or extra-territorial wars and the application of economic sanctions by a group of States against one or more “rogue States” have highlighted the conflicting power relations between States, but also between social groups. The quest for political domination, the application of the economic values of mercantilism, the race for global supremacy between the United States and China, the rise of civil or theocratic autocracies and the technological colonialism of developed countries, the considerable power of multinational corporations and international finance, all lead to major inequalities and open or latent conflicts that are not always economic in nature. From a nationalist or imperialist perspective, Russia has reactivated the military action of a country possessing nuclear weapons. A new global arms race is underway, at a time when humanity has yet to eradicate global extreme poverty, and when the ravages of global warming are looming in the short term
Partial discharge withstand for typical PCB geometries
No full textInternational audienceRising voltage towards medium voltage (MV), paired with high performant wide band-gap (WBG) semiconductors, lead to a significant increase of power electronics converters performances. Printed circuit boards (PCBs) are facing today higher electrical stress, resulting in early degradations due to partial discharges (PDs). This study focuses on the PD localization and the measurement of partial discharge inception voltage (PDIV) of typical metal geometries in PCBs. The considered objects are: pads, which are metallic layers on the PCB surface in contact with air, face-to-face copper strips and parallel covered tracks. PDs were observed thanks to a camera coupled with an image intensifier. Hence, pads demonstrated that corners are favorable to PD activity. A voltage gain of +25% can be obtained by a curving the corners to 1.5 mm. For the interlayer strips, the PDIV is increased by +103% when the insulation distance rises from 200 μm to 1.3 mm within the PCB. However, for the largest insulation gap (1.6 mm), the close distance with air leads to the appearance of early PDs. Covered tracks illustrated that almost doubling the coating thickness results in a voltage gain of +17%, and +28% when it is tripled