1,720,955 research outputs found
A two-phase HVAC-integrated cooling system for traction motors: modelling and performance analysis
No full textTwo-phase fluid flows have been regarded as a candidate cooling method for electric motors in order to boost torque density. Low-temperature, two-phase refrigerant is inherently available in vapour-compression Heat Ventilation Air Conditioning (HVAC) systems which are typically on-board vehicles. This paper explores the potential of bleeding a refrigerant fraction from the HVAC vapour-compression “core” cycle and feed it into the traction motor windings to achieve a radical cooling. In order to evaluate the features and performance of this integrated two-phase motor cooling concept, the paper proposes a simplified modelling technique that integrates the HVAC vapour compression cycle with the motor cooling sub-models. The objective is to assess the reduction in losses and the associated benefits in mitigating the extra burden on the motor and the oversizing requirements of the HVAC compressor
A Sensor Fusion Based Temperature Estimation Model for Oil-Cooled Windings
No full textThis article introduces an innovative method to monitor the average winding temperature in real-time during the operation of an oil-cooled electric motor, particularly suitable for high-performance automotive applications. It is based on the sensor fusion of two distinct dynamic models: one considering the measurement of local temperature through a thermal sensor positioned on the end-winding of the motor, and the other utilizing a first-order model to predict the average winding temperature. The integration of these models significantly enhances the accuracy in estimating the average winding temperature, particularly for short-duty and high current densities
A two-phase refrigerant based cooling system for traction electric motors
No full textDOTTORATOL'attività di ricerca presentata in questa tesi contribuisce allo sviluppo di un nuovo concetto di raffreddamento per i motori dei veicoli elettrici (EV), con l’obiettivo di migliorare le prestazioni del gruppo propulsore. L’approccio proposto si basa sull'utilizzo di un refrigerante bifase a bassa temperatura, già disponibile nei sistemi di climatizzazione a compressione di vapore (HVAC), comunemente presenti a bordo dei veicoli. La tesi esplora la possibilità di estrarre una frazione di refrigerante dal ciclo principale di compressione di vapore del sistema HVAC e di convogliarla negli avvolgimenti del motore, per favorire l’estrazione del calore dissipato dalle perdite negli avvolgimenti e garantire un raffreddamento efficace. L’aspetto chiave di questa soluzione è il cambiamento di fase del refrigerante, che permette di ottenere coefficienti di scambio termico estremamente elevati e di mantenere gli avvolgimenti del motore a temperature significativamente inferiori a quelle tipiche nei motori elettrici con raffreddamento convenzionale. L'obiettivo di questa ricerca è quello di sfruttare la conseguente riduzione della resistività elettrica con la temperatura per diminuire le perdite Joule negli avvolgimenti e migliorare l'efficienza del motore elettrico. Per valutare le caratteristiche e le prestazioni di questo concetto di raffreddamento bifase integrato, la tesi analizza diverse configurazioni progettuali volte a massimizzare il contatto tra il refrigerante e gli avvolgimenti, evidenziandone vantaggi e svantaggi. Inoltre, viene sviluppata una tecnica di modellazione semplificata che integra il ciclo di compressione di vapore dell'HVAC con i sottosistemi di raffreddamento del motore. A tale scopo, è stato sviluppato un modello in Matlab per analizzare configurazioni pratiche dei canali della struttura dell’evaporatore nelle cave degli avvolgimenti. L'obiettivo principale è quantificare la riduzione delle perdite negli avvolgimenti rispetto all'inevitabile aumento del consumo di potenza del compressore dell’HVAC e identificare il miglior compromesso progettuale per massimizzare l’efficienza complessiva del sistema motore-elettrico + HVAC.The research work presented in this thesis provides a contribution to the development of a new disruptive electric motor cooling concept for Electric Vehicles (EVs) to boost power-train performance. This innovative cooling approach is based on the use of low-temperature, two-phase refrigerant that is inherently available in vapour-compression Heat Ventilation Air Conditioning (HVAC) systems, which are typically on-board vehicles. The thesis explores the potential of bleeding a refrigerant fraction from the HVAC vapour-compression core cycle and channelling it into the traction motor windings to extract the rejected heat from winding losses and achieve radical cooling. The central aspect of the proposed solution is the refrigerant phase-change unlocking extremely high heat-transfer coefficients, so as to maintain the motor windings at relatively low temperatures. The ambition is to capitalise on the consequent electric resistivity drop with temperature to reduce winding Joule losses and improved the electric motor drive efficiency. In order to evaluate the features and performance of this integrated two-phase motor cooling concept, the thesis proposes and explores different configurations to bring the refrigerant in close contact with the windings and their pros and cons. Furthermore, the thesis presents a simplified modelling technique that integrates the HVAC vapour compression cycle with the motor cooling sub-models. This is done by building an integrated modelling tool in Matlab and evaluating some practical slot-channel configurations for the evaporator structure. The key objective is to assess the reduction in winding losses against the inevitable increase in the HVAC compressor power demand and identify the best design trade-off.DIPARTIMENTO DI ENERGIA36PERINI, ROBERTOMUSSETTA, MARC
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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