1,720,958 research outputs found
Magnetic and dielectric properties of cobalt ferrite/titania composites
No full textIn order to develop materials with both magnetic and dielectric properties, recently a lot of researchers concentrate their work to process and study composite ceramics with both magnetic and dielectric phases. Cobalt ferrite Co Fe2O4 and TiO2 are good candidates for this type of composites as they have good magnetic and dielectric properties respectively.
New cobalt ferrite/titania (CFO/TO) ceramics composites were prepared by conventional solid state reaction with a CFO/TO ratio ranging from 2 to 8. Composition, crystalline structure and microstructure of the sintered ceramic composite bodies were investigated and the phases content volume percentage were determined. Dielectric permittivity ( real part of permittivity and dielectric losses) and magnetic permeability (real part of permeability and magnetic losses) were measured at room temperature in a range of frequency from 100 Mhz-1 GHz. Dielectric and magnetic properties were analyzed as function of the microscopic structure (SEM analysis) and phase compositions (XRD analysis). The formation of the ternary compound (FCTO) was found in composites with the TO/CFO bigger than 3
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
Preparation and dielectric investigations of Ba0.60Sr0.40TiO3 ferroelectric ceramics with different degree of porosity, presenting
No full textBy introducing a controlled porosity into the ceramic systems, the properties can be improved and make the material proper for being used as high-frequency ultrasonic transducers or for tunable applications. The tailored porosity exposes special properties and characteristics of the materials, which might be completely different than their conventional dense equivalents. The aim of this study was to characterize (Ba,Sr)TiO3 ceramics with different porosity levels. Powders with the composition Ba0.60Sr0.40TiO3 (BST) were prepared following the mixed oxide method by solid-state reaction at a sintering temperature of 1450°C for 2h. The BST ceramics with various porosities have been prepared by addition of lamellar graphite in concentration of 10, 20 and 35%. The effect of addition of graphite on dielectric properties was investigated. We noticed that the increasing of the amount of graphite increases the graded porosity and leads to a low mechanical quality factor. The relative density of the obtained samples varies from values around 95% for the dense ceramic to 66% for porous ceramics. Graphite was burned out through the sintering process and this resulted in a modification of morphology, microstructure and pore density of the ceramic product. The porous samples produced with homogeneous or graded porosity show a strong difference of the dielectric properties and microstructure in comparison with the dense ceramic samples. The role of anisotropic porosity on the functional properties on the dielectric properties is discussed. Microstructural, morphological and dielectric investigations have been performed and data were compared with other literature studies. From SEM analysis it was found that with addition of graphite as pore forming the samples present a fracture mode transformation from intragranular fracture to an intergranular fracture and a decreasing of grain size of BST. Furthermore, as BST grain size becomes smaller, the volume of grain boundary increases and the crack prefers spreading along grain boundary to splitting the strengthened grain. The Impedance Spectroscopy analyse was performed in the temperature range of (21-200)°C and frequency of 20Hz–2MHz. The dielectric investigations have shown that the dielectric constant of the Ba0.60Sr0.40TiO3 (BST) ceramics with different degree of porosity, decrease and remains constant at higher frequency, indicating dielectric dispersion. The frequency dependence of the real and imaginary part of permittivity present a few characteristic relaxations which appear in the specific frequency ranges: (i) the increasing of the real and imaginary parts of permittivity at low frequencies below 100Hz for the compositions with x=10, 20 and 35% graphite is most probably associated to the thermally activated space charge effects (Maxwell–Wagner phenomena) and (ii) anomalies of the imaginary part of permittivity above 103Hz, for samples with x=10 and 20% porosity, which seems to be related to a Debye-type relaxation process. The dielectric properties of the investigated ceramics were characterized and correlated with their microstructure. From dielectric constant dependence with temperature, a shift of Curie temperature of ceramics was observed and possible reasons for these effects were interpreted. Acknowledgements: This work was financially supported by CNCS-UEFISCDI projects PNII-ID-PCE-2011-30745 and by ERASMUS placement programme between Univ. “Al. I. Cuza” Iasi & ISTEC-CNR Faenza, Italy. The collaboration in frame of the COST Action MP0904 is highly acknowledgements
Electrophoretic deposition of bilayer composite films based on CoFe2O4/TiO2 and PZT
No full textIn the recent years the interest of the research community towards multiferroic composite materials was growing fast. A number of papers relates to bulk materials while less attention is focused on films. Electrophoretic deposition (EPD) was applied to prepare magnetoelectric (ME) composite bilayer thick films based on perovskite phase and spinel cobalt ferrite as some of the best piezoelectric and magnetostrictive oxides belong these crystal groups. The co-deposition of titanium oxide (TO) and cobalt ferrite (CFO) nanoparticles and the deposition of niobium-doped lead titanate zirconate (PZTN) were made from colloidal suspensions in ethanol keeping constant voltage and recording the current. Good adhesion and compaction of the green film were achieved by optimization of deposition voltage and time while high density of the film and minimized interphase reactions occurred after sintering. The deposited volume, the mixing of dielectric and magnetic phases and the density and ordering of the films have been verified by electron scanning microscopy after heat treatment. No reactions between the different phases was found. The piezoelectric properties were measured on the sintered films
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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