1,720,959 research outputs found
Numerical simulations of vector hysteresis processes via the Preisach model and the Energy Based Model: An application to Fe-Si laminated alloys
No full textThe paper presents the state of the art and the problems already open in modelling the hysteresis phenomenon in 2-D for laminated soft ferromagnetic materials. Firstly, a thorough experimental investigation has been carried out at a very low frequency by a single disk tester (SDT) for a specimen of innovative NGO electrical steel sheet. Scalar, rotational and elliptic magnetization processes have been experimentally measured under controlled waveforms of the magnetic induction vector thanks to an effective digital feedback algorithm. Two numerical model of hysteresis have been taken into account to reproduce the measured magnetization processes: the vector Preisach model (VPM) and the Energy Based Model (EBM). The main advantages and limitations in the use of the two hysteresis models are comprehensively analysed and discussed, taking into consideration both the problem of identification and the simulation results. In particular, the effective capability of the models to reproduce the vector field trajectories and to predict the hysteresis power losses has been shown. Conclusive considerations involve the memory usage and the computational time for the low level of abstraction implementation of the two hysteresis models
Comparison between different models of magnetic hysteresis in the solution of the TEAM 32 problem
No full textThe numerical modeling of magnetic materials in simulators is a difficult task, above all in real devices with specific excitation. The aim of this work is to compare the accuracy of scalar and vector Preisach models in a well know test benchmark: the TEAM 32 problem. The availability of measured data for this benchmark test and the simple geometry allow us to build hysteresis models and to test them in a 2D finite element analysis (FEA) scheme. The specific numerical formulation of each hysteresis model implemented is described, including the technique for the numerical identification of parameters starting from measured data. The comparison among the models is done in terms of accuracy, but also in terms of easy implementation in the FEA scheme and of computational cost
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
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
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
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