1,720,956 research outputs found
Multiphysics Thermo-Structural Design of the Rotor in High-Speed Permanent Magnet Machines for Aerospace Propulsion Applications
No full textHigh temperatures, thermal and mechanical stresses, rotor imbalances in high-speed Surface Permanent Magnet Synchronous machines (SPMSM) often dictates the maximum power output of the machine. Hence, a trade-off should be made between the cooling design, and machine structure stiffness, and the power rating. This work discusses the modelling and design process of the high-speed machine rotor by means of thermo-structural and modal analyses to minimize the trade-offs between the structural and thermal designs. The study discusses the design and modeling of SPMSM machine rotor thermally and structurally to achieve the highest power output of the machine while targeting rotor weight reduction. The design of the rotor shows safe operating temperatures and stress levels at the machine rated speed and power output as a result of the minimized and well-distributed thermal and mechanical stresses. A power density of 7.1 kW/kg is achieved by designing the machine within safe operating limits without using excessive safety margins
Low Resistance Heat Paths Application to Electric Machines Rotor Cooling
No full textThermal non-uniformities in electric machines manifested as local hotspots and high temperature gradients, pose significant risks to machine safety, leading to heightened thermal stresses and an increased likelihood of component failures. In this research, a newly developed 150 kW high-speed machine exhibited significant thermal imbalances, leading to hot spots near bearing seats. To mitigate these challenges, the paper proposes the use of integrated low-resistance heat paths in the steel rotor, replacing traditional void entities with lightweight, highly conductive materials such as aluminum or copper. Computational Fluid Dynamics (CFD) simulations demonstrate the effectiveness of an aluminum insert, resulting in a significant 47°C reduction in maximum shaft temperature and improved thermal uniformity. Structural analysis guides the optimization of fit parameters, defining a transition fit for maximum stress within yield strength. This comprehensive approach offers a strategic solution for enhancing rotor thermal management in high-speed electrical machines
Innovations in Axial Flux Permanent Magnet Motor Thermal Management for High Power Density Applications
Full text linkFor aerospace applications, power density is a major driving force in the design of electrified powertrains. At the forefront is the challenging design of electric motors with high efficiencies, torque, and power capabilities. Due to its high performance, the axial flux permanent magnet (AFPM) motor is expected to be one of the leading technologies to meet the demands of these industries. Finding the balance between the cooling system's effectiveness and subsequent parasitic losses is key to utilizing these performance benefits. Single-stator double-rotor topologies achieve the best torque density and lower stator losses and, however, are more challenging to cool as the stator is in the center of the motor. Single-stator single-rotor and double-stator machines are less challenging to cool but typically have lower power density. Rotor air cooling is discussed, including the effectiveness of blades, meshes, and vents, which can be optimized to prevent demagnetization. Stator cooling is critical as many machines maximize current density, producing a large amount of heat. The chosen strategy depends on the machine topology and can be accomplished by several strategies, including jackets, fins, channels, immersion cooling, hollow coils, and heat pipes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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