1,721,015 research outputs found
Comprehensive investigation of alternating and rotational losses in non-oriented steel sheets
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Loss decomposition under two-dimensional flux loci in nonoriented steel sheets
No full textEnergy losses have been investigated as a function of magnetizing frequency (DC - 200 Hz) and peak polarization value (0.25 T- 1.7 T) in non-oriented Fe-Si laminations under controlled alternating, elliptical, and circular flux loci. It is shown that, exploiting the concept of loss decomposition and the ensuing interpretative framework provided by the statistical theory of losses, a phenomenological approach to the energy loss prediction under two-dimensional fluxes can be formulated. The treatment conspicuously relies on the analysis of the excess loss component and its frequency dependence, which is observed to follow to a good approximation a law of the type W exc ∝ f 1/2, whatever the flux loci. It is concluded that the behavior of the energy loss under elliptical flux can be predicted to a good approximation as a function of frequency, peak polarization, and degree of ellipticity by preemptive experimental determination of the energy loss under alternating field and circular polarization at selected frequencie
13th International Workshop on 1&2 Dimensional Magnetic Measurement and Testing, 3-6 September 2014, Turin, Italy
No full textGuest Editorial of the 13th International Workshop on 1&2 Dimensional Magnetic Measurement and Testing, 3-6 September 2014, Turin, Ital
Magnetic characterization of water suspensions of iron nanoparticles for groundwater remediation
No full textIron nanoparticles are a potential answer to the need for effective in-situ groundwater remediation technologies. Nanoscale iron slurries can be injected in the subsurface allowing to target directly the source of contamination reducing times and costs of remediation. Unfortunatelly the use of this material is strongly hindered by magnetic interactions. Several studies [1] have shown that this system is unstable and tends to separate into water and solid phases after a relatively short time. The colloidal instability is due to the aggregation of the nanoparticles into micrometric dendritic structures which tend to sediment. In this study a magnetic characterization was performed on some samples of iron nanopowders with and without the addition of hydrocolloids to prevent the aggregation and settling. Hysteresis loops have been measured on water dispersed Fe nanoparticles by means of an alternating gradient field magnetometer, at room temperature. The studied systems are characterized by a soft, isotropic magnetic behaviour. However, even though the samples are constituted by nanometer-sized Fe particles, the magnetization processes do not follow a Langevin-type curve, typical of superparamagnetic systems. On the contrary it has been shown that the particles form multi-domain aggregates [2]. An extension of the Stoner-Wohlfarth model can be applied, in which a new switching rule for the local magnetization is postulated, accounting for a nucleation of a new magnetic domain and consequent domain wall displacement within any agglomerate of particles. A so-called cut coefficient r (0 _ r _ 1) parametrizes the nucleation field, being r = 1 the case of magnetization reversal due only to reversible or irreversible rotations (thus corresponding to the “classical” Stoner-Wohlfarth case), whereas when r tends to 0 the domain wall movements become increasingly important in inverting the sample magnetization. Samples with different concentrations of Fe nanoparticles, dispersed in water bare or after coating with hydrocolloids, have been studied through their room temperature hysteresis loops. Proper application of the “extended” Stoner-Wohlfarth model allows an estimation of the effectiveness of the coating to prevent the formation of large aggregates; in fact, if the particles are more separated, their magnetic behaviour should progressively tend towards that of smaller clusters (with a cut coefficient r closer to 1) or even non-interacting particles (with a superparamagnetic behaviour)
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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