Influence of design parameters on the starting torque of a single-phase PM brushless DC motor

The starting torque of a single-phase permanent magnet brushless DC motor is investigated, for both radial and parallel magnetization. Finite element analysis is used to assess the relative merits of alternative methods of introducing the required air gap asymmetry, viz. tapered air gap, stepped air gap, asymmetric air gap, and slotted teeth. The predicted results are validated experimentall

CIRCULAR COMPARISON OF CONVENTIONAL PRESSURE STANDARDS USING A TRANSPORTABLE OPTICAL REFRACTOMETER: PREPARATION AND TRANSPORTATION

Using a transportable Fabry-Pérot cavity refractometer, a circular comparison of existing primary standards at several national metrology institutes is currently underway. This paper provides information about the refractometer, the preparation for the comparison, and the transportation procedur

Quantum-based realizations of the pascal: status and progress of the EMPIR-project: quantumpascal

The QuantumPascal (QP) project combines the capabilities of 12 European institutions to enable traceable pressure measurements utilizing quantum-based methods that evaluate the number density instead of force per area to target the wide pressure range between 1 Pa and 3 MPa. This article summarizes the goals and results since the project start in June 201

Forest and woodland replacement patterns following drought-related mortality

Forest vulnerability to drought is expected to increase under anthropogenic climate change, and drought-induced mortality and community dynamics following drought have major ecological and societal impacts. Here, we show that tree mortality concomitant with drought has led to short-term (mean 5 y, range 1 to 23 y after mortality) vegetation-type conversion in multiple biomes across the world (131 sites). Self-replacement of the dominant tree species was only prevalent in 21% of the examined cases and forests and woodlands shifted to nonwoody vegetation in 10% of them. The ultimate temporal persistence of such changes remains unknown but, given the key role of biological legacies in long-term ecological succession, this emerging picture of postdrought ecological trajectories highlights the potential for major ecosystem reorganization in the coming decades. Community changes were less pronounced under wetter postmortality conditions. Replacement was also influenced by management intensity, and postdrought shrub dominance was higher when pathogens acted as codrivers of tree mortality. Early change in community composition indicates that forests dominated by mesic species generally shifted toward more xeric communities, with replacing tree and shrub species exhibiting drier bioclimatic optima and distribution ranges. However, shifts toward more mesic communities also occurred and multiple pathways of forest replacement were observed for some species. Drought characteristics, species-specific environmental preferences, plant traits, and ecosystem legacies govern post drought species turnover and subsequent ecological trajectories, with potential far-reaching implications for forest biodiversity and ecosystem services.Peer reviewe

Forest and woodland replacement patterns following drought-related mortality

Forest vulnerability to drought is expected to increase under anthropogenic climate change, and drought-induced mortality and community dynamics following drought have major ecological and societal impacts. Here, we show that tree mortality concomitant with drought has led to short-term (mean 5 y, range 1 to 23 y after mortality) vegetation-type conversion in multiple biomes across the world (131 sites). Self-replacement of the dominant tree species was only prevalent in 21% of the examined cases and forests and woodlands shifted to nonwoody vegetation in 10% of them. The ultimate temporal persistence of such changes remains unknown but, given the key role of biological legacies in long-term ecological succession, this emerging picture of postdrought ecological trajectories highlights the potential for major ecosystem reorganization in the coming decades. Community changes were less pronounced under wetter postmortality conditions. Replacement was also influenced by management intensity, and postdrought shrub dominance was higher when pathogens acted as codrivers of tree mortality. Early change in community composition indicates that forests dominated by mesic species generally shifted toward more xeric communities, with replacing tree and shrub species exhibiting drier bioclimatic optima and distribution ranges. However, shifts toward more mesic communities also occurred and multiple pathways of forest replacement were observed for some species. Drought characteristics, species-specific environmental preferences, plant traits, and ecosystem legacies govern postdrought species turnover and subsequent ecological trajectories, with potential far-reaching implications for forest biodiversity and ecosystem services.Additional co-authors: Lucía Galiano, Joseph L. Ganey, Patrick Gonzalez, Anna L. Jacobsen, Jeffrey Michael Kane, Thomas Kitzberger, Juan C. Linares, Suzanne B. Marchetti, George Matusick, Michael Michaelian, Rafael M. Navarro-Cerrillo, Robert Brandon Pratt, Miranda D. Redmond, Andreas Rigling, Francesco Ripullone, Gabriel Sangüesa-Barreda, Yamila Sasal, Sandra Saura-Mas, Maria Laura Suarez, Thomas T. Veblen, Caroline Vincke, and Ben Zeema

Realization, characterization and measurements of standard leak artefacts

Predictability of gas flows through leak elements in various conditions (geometry of leak elements, gas species, pressure) from the results of only a few measurements in a specific configuration is an issue for the gas dynamics theory. This paper aims to provide results of leak flow rate measurements performed by national metrology institutes (NMIs) in the framework of the European project JRP IND12. Leak artefacts made of different materials with well defined geometry, were calibrated by means of primary standards with different gas species flowing to vacuum or atmospheric pressure. The numerous collected data are made available to allow the experts in gas dynamics to use this large database to improve the knowledge of gas flow in narrow ducts in terms of predictability for different gas species and find a simple model to describe the gas flow inside microchannels

Réponse homogène de l'architecture des arbres au climat dans de nombreux biomes : conséquences sur l'adaptation des forêts au changement climatique

International audienceDes forêts semi-arides aux forêts boréales, en passant par les biomes méditerranéens, tempérés, et montagnards, 19 équipes ont étudié la plasticité du développement architectural de 18 espèces d'arbres soumis à des variations et stress climatiques dans 8 pays sur 3 continents. L'analyse porte sur la croissance des branches, leur ramification, le nombre et la taille des feuilles, la reproduction qui interfère avec ce développement et la phénologie qui en est l'un des moteurs. Le tout dans le milieu naturel, suivant de larges gradients d'altitude et de latitude, et dans des expérimentations contrôlant le climat (température, exclusion de pluie, irrigation). De façon très homogène, tous les arbres étudiés quel que soit le milieu réagissent aux stress en réduisant leur taux de ramification et le nombre de feuilles, en réduisant la taille des feuilles si la contrainte est hydrique et en modifiant leur stratégie reproductive. Nous montrons que l'adaptation de la surface foliaire à la ressource en eau est largement pilotée par la branchaison. L'inertie architecturale restreint l'adaptation foliaire et tamponne la production de biomasse longtemps après un stress fort ou répété. Le changement climatique modifie la phénologie de ces arbres, ajoutant des contraintes à leur développement. La modélisation du développement architectural des arbres dans ses relations au climat est une avancée significative pour comprendre leur capacité d'adaptation au changement climatique et les risques qui en découlent pour la production forestière

Forest and woodland replacement patterns following drought-related mortality

Forest vulnerability to drought is expected to increase under anthropogenic climate change, and drought-induced mortality and community dynamics following drought have major ecological and societal impacts. Here,we showthat tree mortality concomitant with drought has led to short-term (mean 5 y, range 1 to 23 y after mortality) vegetation-type conversion in multiple biomes across the world (131 sites). Self-replacement of the dominant tree species was only prevalent in 21% of the examined cases and forests and woodlands shifted to nonwoody vegetation in 10% of them. The ultimate temporal persistence of such changes remains unknown but, given the key role of biological legacies in long-term ecological succession, this emerging picture of postdrought ecological trajectories highlights the potential for major ecosystem reorganization in the coming decades. Community changes were less pronounced under wetter postmortality conditions. Replacement was also influenced by management intensity, and postdrought shrub dominance was higher when pathogens acted as codrivers of tree mortality. Early change in community composition indicates that forests dominated by mesic species generally shifted toward more xeric communities, with replacing tree and shrub species exhibiting drier bioclimatic optima and distribution ranges. However, shifts toward more mesic communities also occurred and multiple pathways of forest replacement were observed for some species. Drought characteristics, species-specific environmental preferences, plant traits, and ecosystem legacies govern postdrought species turnover and subsequent ecological trajectories, with potential far-reaching implications for forest biodiversity and ecosystem services