1,720,959 research outputs found
Time domain modelling of soft ferrite inductors for power converters applications
No full textIn this paper, we discuss about the accuracy and robustness of a time domain model for the analysis of soft ferrite core inductors, particularly applicable in the design of power converters. The model is based on the division of the magnetic field into three components, which are suitably defined on the basis of the static and dynamic behavior of a magnetic material and are identified by experimental data. A detailed description of the model and the obtained results are presented in the paper. The results obtained are also compared with the ones calculated from different approaches, known in literature. The model is applied to the prediction of losses and peak current of a family of ring shape core inductors
Modelling of dynamic losses in soft ferrite cores
No full textIn this paper a time domain model of the dynamic behavior of ferrite cores is implemented and discussed. This model is based on the magnetic field decomposition in three parts dealing with the static anhysteretic magnetization, the static hysteretic magnetization and the dynamic magnetization processes. These three components are depending on the magnetic induction values and derivative in time domain by means three functions properly identified. In particular, the capability of the model for power losses prediction is discussed, also in comparison with the classical approaches defined on both frequency domain and time domain by Steinmetz. The model parameters are identified for a suitable Mn–Zn ferrite inductor with toroidal core, and the reliability of the method for the prediction of the magnetization processes, under sinusoidal and not sinusoidal excitations, is assessed for the typical work frequency range of magnetic components in power electronics devices
Measurements of magnetic characteristics of laminated Fe-Si steel filter inductors in grid interface converters
No full textThe knowledge of the magnetic characteristic of an inductor is a key factor for the design of filters of power converter systems for electric grid interfaces. The accurate and reliable definition and measurement of the parameters such as the differential inductance, the saturation level and the linearity range is a difficult task, in particular for high current inductors. In this paper a comparison between different methods of measure of the magnetic characteristic of a gapped filtering inductor versus current, in the range from zero magnetization to the saturation, is presented and discussed. It is shown that the different measurement methods provide appreciable differences in the evaluation of the magnetic characteristic of a benchmark inductor. The differences found are also analyzed by suitable numerical simulations
On the Use of Feedforward Neural Networks to Simulate Magnetic Hysteresis in Electrical Steels
No full textThe present investigation aims at the definition of an efficient and robust neural network-based model to simulate the magnetic hysteresis in performing magnetic alloys suitable for aircraft applications. Starting from a set of measured hysteresis loops, a convenient and effective method to train the network consists to identify the Preisach model and use it for the generation of the training set. The obtained neural network turned out to be particularly robust and able to reproduce the behaviour of the Preisach model with a significant reduction of the computational time. The comparative analysis between the two approaches takes into account different kinds of excitation waveforms
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
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