1,721,025 research outputs found
Magnetocaloric characterization of materials
No full textThe magnetocaloric effect manifests itself as a change in temperature of a magnetic material following the variation of an applied magnetic field. This effect constitutes the basis for the development of important applications such as magnetic refrigeration and, in general, thermomagnetic energy conversion technologies. Accurate and reliable characterization of the magnetocaloric effect is crucial for identifying and selecting the most promising materials and for realistic design of refrigerant machines. This chapter provides a comprehensive and critical review of the methods and experimental setups developed for measuring the magnetocaloric effect. It offers an in-depth discussion and analysis of both indirect magnetometric and calorimetric methods and direct methods, along with detailed descriptions of the experimental setups adopted. Each technique is examined to highlight its primary advantages and potential issues, providing a practical guide for obtaining accurate magnetocaloric characterizations of materials. The chapter also addresses the measurement of the effect across first-order transitions, emphasizing the importance of proper measurement protocols. Special conditions, such as rapid field changes or low-mass samples, are considered carefully, as they can provide new insights into material properties or simulate real application conditions. Additionally, some recent advanced experimental techniques are presented, which are capable of simultaneously measuring different physical properties of materials or coupled multicaloric effects
Singular point detection of energy losses in hard magnetic materials
No full textThe real and the imaginary part of the reversible parallel susceptibility (RPS) and it harmonics was measured using the modulation technique. Singular Point Detection (SPD) peak in the second harmonic of the complex susceptibility was observed
On the direct measurement of the adiabatic temperature change of magnetocaloric materials
Full text linkThe direct measurement of the adiabatic temperature change of magnetocaloric materials is
fundamental to design efficient and eco-friendly magneto cooling devices. This work reports an
overview of the measurement principle and of the main experimental issues that have to be
considered to obtain a reliable characterization of materials. The effect of non-ideal adiabatic
conditions, the role of the temperature sensor and the influence of specific properties of the
material are discussed on the basis of finite-difference thermal simulations and special designed
experiments. Two cases are considered in detail: the characterization of thin samples and the
measurement of caloric response to fast field changes. Finally, the impact of different
measurement protocols is discussed in the case of materials with first-order transitions
Magnetic analysis of MnAs films grown on GaAs and Si substrates for potential spintronics and magnetocaloric applications
No full textWe present a magnetic characterisation of MnAs films grown by MOVPE on semiconductor substrates, for comparing the effect of thickness and substrate on their magnetic and magneto-thermal properties, with particular focus on the nature of the magneto-structural transition between the ferromagnetic hexagonal α-phase and the paramagnetic orthorhombic β-phase. The nature of this transformation depends on the presence of strain and turns out to be of second-order type for epitaxial-crystalline MnAs/(0 0 1)GaAs films and closer to a first-order type for polycrystalline MnAs/SiO2/Si films. The magnetocaloric effect at the transition has been estimated for thin film samples, resulting appreciably lower than that of bulk MnAs. © 2009 Elsevier B.V. All rights reserved
A new semimagnetic compound: Cd1-xFexIn 2S4 single crystal grown by CVT
No full textSingle crystals of the Cd1-xFexIn2S 4 compounds were grown by the chemical vapour transport method using iodine as transport agent. The crystals were grown by placing the ampoule in a two zone furnace, keeping the source temperature and the deposition temperature at 850 and 800 °C respectively. The resulting crystals with nominal concentrations: x = 0.25, 0.5, 0.75 were characterized by X-ray powder diffraction, electron probe micro-analysis and magnetic measurements. Electron probe micro-analysis showed that the actual concentration of Fe was lower than the nominal one. X-ray diffractograms were taken at room temperature for each sample, revealing that the compounds form a solid solution in the whole range of compositions and crystallize with cubic symmetry in the space group Fd3m. All samples show a spinel structure with a random arrangement of cations. The magnetic behavior of the samples was investigated by low-field magnetization measurements in the range 5-300 K. The observed magnetic behavior does not show any magnetic transition in the studied temperature range. However an irreversibility has been observed between zero-field-cooled (ZFC) and field-cooled (FC) cycles. High temperature susceptibility data follow the Curie-Weiss law with a negative paramagnetic Curie temperature, indicating the predominance of antiferromagnetic interactions. The optical absorption data for sample with x = 0.75 shows a direct energy gap of 1.28 eV at RT. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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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