30,951 research outputs found
Maximum-torque-per-ampere control of phase advance modulation of an SPM wind generator
No full textSurface permanent-magnet (SPM) machines are normally operated by controlling the d- and q-axis currents. This paper examines the control of SPM generators based on controlling the terminal voltage magnitude V and power-factor angle 8. This is well suited for generator operation when using a switched-mode rectifier and avoids the need for a rotor position sensor. The parameters required for generating a given value of torque with minimum phase current in order to minimize copper losses are derived in this paper. This will be achieved by controlling V and 8 to keep the d-axis current equal to zero at low speed, before switching to field-weakening control at higher speeds. Simulated and experimental results will be used to verify the control strategy and the efficiency achieved.Mehanathan Pathmanathan, Wen L. Soong and Nesimi Ertugru
Comparison of AC/DC converters and the principles of a new control strategy in small-scale wind turbine systems
No full textThis paper provides a detailed comparison of AC/DC converters commonly used in small-scale wind turbine systems. The paper reviews the main AC/DC converter topologies first including rectifier, switch-mode rectifier and inverter, and provides their operational features and characteristics. Then based on the previous analytical and comparison studies, it describes a novel multi-mode control strategy, which aims to improve the performance of small-scale wind turbines over a wide operating speed range while considering trade-off between performance and control complexity in such converters.Lujie Chen, Wen. L. Soong, Mehanathan Pathmanathan and Nesimi Ertugrulhttp://aupec2012.org
Dynamic wind turbine output power reduction under varying wind speed conditions due to inertia
No full textABSTRACTThe inertia of wind turbines causes a reduction in their output power due to their inability to operate at the turbine maximum co‐efficient of performance point under dynamic wind conditions. In this paper, this dynamic power reduction is studied analytically and using simulations, assuming that a steady‐state optimal torque control strategy is used.The concepts of the natural and actual turbine time‐constant are introduced, and typical values for these parameters are examined. It is shown that for the typical turbine co‐efficient of performance curve used, the average turbine speed can be assumed to be determined by the average wind speed. With this assumption, analytical expressions for the power reduction with infinite and then finite turbine inertia are determined for sine‐wave wind speed variations. The results are then generalized for arbitrary wind speed profiles.A numerical wind turbine system simulation model is used to validate the analytical results for step and sine‐wave wind speed variations. Finally, it is used with real wind speed data to compare with the analytical predictions. Copyright © 2012 John Wiley & Sons, Ltd.Chun Tang, Wen L. Soong, Peter Freere, Mehanathan Pathmanathan and Nesimi Ertugru
Distributed human computation framework for linked data co-reference resolution
No full textDistributed Human Computation (DHC) is a technique used to solve computational problems by incorporating the collaborative effort of a large number of humans. It is also a solution to AI-complete problems such as natural language processing. The Semantic Web with its root in AI is envisioned to be a decentralised world-wide information space for sharing machine-readable data with minimal integration costs. There are many research problems in the Semantic Web that are considered as AI-complete problems. An example is co-reference resolution, which involves determining whether different URIs refer to the same entity. This is considered to be a significant hurdle to overcome in the realisation of large-scale Semantic Web applications. In this paper, we propose a framework for building a DHC system on top of the Linked Data Cloud to solve various computational problems. To demonstrate the concept, we are focusing on handling the co-reference resolution in the Semantic Web when integrating distributed datasets. The traditional way to solve this problem is to design machine-learning algorithms. However, they are often computationally expensive, error-prone and do not scale. We designed a DHC system named iamResearcher, which solves the scientific publication author identity co-reference problem when integrating distributed bibliographic datasets. In our system, we aggregated 6 million bibliographic data from various publication repositories. Users can sign up to the system to audit and align their own publications, thus solving the co-reference problem in a distributed manner. The aggregated results are published to the Linked Data Cloud
Precipitation of supersaturated solute in H ion irradiated Fe-Au and Fe-Au-W alloys studied by positron annihilation spectroscopy
No full textThe effect of thermal aging of homogenized Fe-Au and Fe-Au-W alloys, irradiated at room temperature with hydrogen ions, was studied for an aging treatment at 300 °C for aging times up to 100 h. The aging behavior of the Fe-based alloys is compared to the results for pure Fe. The precipitation behavior of Au-rich and W-rich precipitates and its correlation to the H+ irradiation-induced defects is investigated by variable energy positron annihilation spectroscopy (VEPAS). The formation of open-volume defects after irradiation is monitored by an increase in the S parameter, while the recovery of the vacancy-like defects and the formation of precipitates are signalled by an increase in the W parameter. Au-rich precipitation continuously develops during long-term aging, as indicated by the increase in the W parameter. The change of the W parameter in the Fe-Au-W alloy is not only due to the effect of solute W on the Au precipitates, but also because of the interface of W-rich Laves phase with matrix.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Novel Aerospace MaterialsRST/Fundamental Aspects of Materials and Energ
Lateral Inverse Proximity Effect in Ti/Au Transition Edge Sensors
No full textWe report measured Tc of superconducting Ti/Au bilayer strips with a width W varying from 5 to 50 µm. The strips were fabricated based on a Ti/Au bilayer that consists of a 41-nm-thick Ti layer to which a 280-nm-thick Au layer was added. We find that the Tc drops as W decreases and the declining trend almost perfectly follows Tc/ [mK] = - 738.4 [μ m] 2/ W2+ 91.0 , where Tc(W= ∞) of 91 mK is consistent with the intrinsic Tc of the bilayer. The result is interpreted as a consequence of the lateral inverse proximity effect originated in normal-metal microstructures, namely Au overhangs that exist at the edges of the Ti/Au bilayer. The Tc shift from the intrinsic Tc should be anticipated in addition to the longitudinal proximity effect from superconducting Nb leads when one designs Ti/Au TESs.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ImPhys/Optic
Le suicide et les politiques sociales au Québec
No full textÀ partir de trois documents émanant d'instances mises sur pied par le gouvernement du Québec, nous tentons, dans cet article, de déceler comment ce dernier s'apprête à encadrer et à orienter l'intervention sur le suicide. Nous nous intéressons au sort que les politiques sociales pourraient et, selon nous, devraient réserver au suicide. Nous préconisons une approche qui reconnaît pleinement la dimension sociale du suicide et qui met l'accent sur la prévention primaire ainsi que sur le soutien par l'État d'un réseau communautaire autonome constituant, par rapport au réseau public, un partenaire égal.Starting from three documents published by organizations set up by the Québec government, the author examines how the government intends to give direction to and build a framework for social intervention in the area of suicide. The article looks at the fate that social policies could and, according to the author, should reserve for suicide. The author argues for an approach that fully recognizes the social dimension of suicide and that emphasizes primary prevention as well as government support for an autonomous community network that would have equal footing with the public network
Assessing the scientific integrity of the collected work of one author or author group
No full textObjectives: No published methods for research integrity review include both statistical techniques applied to groups of randomized trials and individual assessment of papers. We propose a method based on practical experience of investigating data integrity across the collected papers of an author or author group. Study Design and Setting: We report our approach to investigating the collected papers of an author or author group suspected of academic misconduct. Results: In the investigation of the work of an author or author group, we recommend a systematic search for the work of the involved authors in PubMed, Google Scholar, and the Retraction Watch database, as well as a search of trial registries for unpublished clinical trials. Summary information from studies should be tabulated to assess consistency between study registration, execution, and publication. Each paper should be investigated for unfeasible features of the governance, methodology, execution, results, and reporting of the study. Pairwise comparison of baseline and outcome tables between papers may reveal data duplication or unfeasibly large differences between baseline characteristics in similar studies. Assessment of baseline characteristics from multiple randomized trials using Carlisle’s method can determine whether the data are consistent with a properly executed randomization process, as can checking whether reported baseline characteristics follow expected patterns for random variables such as Benford’s law. If serious concerns are raised, a more thorough investigation should be performed by journals, publishers, and institutions. Conclusion: These methods provide a systematic and reproducible way to assess the collected work of an author or group of authors.Jeremy Nielsena, Esmée M. Bordewijka, Lyle C. Gurrinc, Siddharth Shivanthad, Madeline Flanagana, Sue Liud, May M. Linna, Kelly X. Zhoua, Rik van Eekelenb, Nicholas J.L. Browne, Jim Thorntonf, Ben W. Mo
Face au Sida, les recours parallèles
No full textInternational audienceBased on an anthropological research conducted in Marseille in a hospital setting, the author describes, in the early 1990s and before the advent of triple therapies, the complexity of care practices and remedies for people with AIDS. The article testifies to daily difficulties managing the disease and stigma fears for people with the virus.A partir d'une recherche anthropologique menée à Marseille en milieu hospitalier, l'auteur décrit, au début des années 1990 et avant l'arrivée des trithérapies, la complexité des pratiques de soins et des recours des personnes atteintes du SIDA . L'article témoigne des difficultés quotidiennes à gérer la maladie et les craintes stigmatisation pour les personnes atteintes du virus
La langue au théâtre : expression d'une identité culturelle ?
No full textThe title of our dissertation points to the key elements of this study. To probe contemporary theatre, especially in France and in Italy, we rely on a specific tool: the rhythm. We propose a comparative study of four plays, each one by a different author, two Italians and two French : Juste la fin du monde (1990) by Jean-Luc Lagarce, Clôture de l’amour (2011) by Pascal Rambert, Italia-Brasile 3 a 2 (2002) by Davide Enia and Dissonorata (2006) by Saverio La Ruina. The definition of rhythm, as given by Henri Meschonnic, allows us to study these plays without a precise linguistic, theatrical, and sociological point of view. This is because the poetics of the author manifests itself via and thanks to the rhythm. A rhythm that is certainly rooted in the linguistic structure of the play, but which is also the accomplishment of the historical and cultural expression of the voices of the authors.Dans le titre de notre thèse nous avons souligné les éléments au cœur de cette recherche. Pour interroger les pratiques théâtrales contemporaines, notamment en France et en Italie, nous avons eu recours à un outil particulier : le rythme. Ainsi, nous proposons une étude comparée de quatre pièces chacune d’un auteur différent, deux français et deux italiens : Juste la fin du monde (1990) de Jean-Luc Lagarce, Clôture de l’amour (2011) de Pascal Rambert, Italia-Brasile 3 a 2 (2002) de Davide Enia et Dissonorata (2006) de Saverio La Ruina. La définition de rythme donnée par Henri Meschonnic nous a permis d’étudier ces pièces sans adopter un point de vue uniquement linguistique, théâtral ou sociologique. Car la révélation de la poétique de l’auteur se dévoile et se rend manifeste précisément grâce au rythme. Un rythme qui relève certes de la structure linguistique de la pièce, mais qui est aussi l’accomplissement de la manifestation historique et culturelle de la voix de ces auteurs
- …
