1,720,961 research outputs found
Design Optimization of Integrated Magnetic Core Inductors
No full textThis paper presents a design study of novel geometrical configurations for miniaturized toroidal planar core thin-film inductors. A standard core with square-shaped toroidal geometry is compared to a new core with serpentine toroidal geometry. The mathematical model of the inductor demonstrates the possibility to further increase the maximum inductance value for closed or air-gap core inductors in a given footprint area (up to +35% in 16 mm2), by means of a more efficient use of the core surface area in case of serpentine geometry, assuming the same coupling factor for both windings. Furthermore, the presented serpentine geometry increases performances in terms of magnetic energy density and quality factor while retaining higher inductance values, at the cost of a limited increase of layout complexity. This paper provides also a more accurate estimation of the inductance of a square shaped toroidal inductor based on the evaluation of the mean magnetic path length accounting for the non-uniformity of the magnetic flux density in the core cross section and for the corner effect
Design and optimization techniques of over-chip bond-wire microtransformers with LTCC core
Full text linkThis paper describes the realization of bond-wire micromagnetics by using standard bonding wires and a toroidal ferromagnetic low-temperature co-fired ceramic core with high resistivity. The proposed fabrication procedure is suitable for the development of magnetic components on the top of an integrated circuit with a small profile and a small size (<;15 mm 2 ). A transformer is designed and applied over chip, working in the MHz range with high inductance (~33 μH) and high effective turns ratio (~20). Applications include bootstrap circuits and micropower conversion for energy harvesting. Measurements demonstrate a maximum secondary Q-factor of 11.6 at 1.3 MHz, and a coupling coefficient of 0.65 with an effective turns ratio of 19, which are among the highest values reported for toroidal miniaturized magnetics. The achieved inductance density is 2 μH/mm 2 , along with an inductance per unit core volume of 15.6 μH/mm 3 , and a dc inductance-to-resistance ratio of 2.23 μH/Ω. The presented technique allows to obtain over-chip magnetics trough a postprocessing of the core, and it is also suitable for high-density power supply in package and power supply on-chip. Finally, a series of optimization techniques for planar core magnetic devices in order to maximize the inductance per unit area is discussed and applied to the considered case
Design and fabrication of a 315 uH bondwire micro-transformer for ultra-low voltage energy harvesting
No full textThis paper presents a design study of a new topology for miniaturized bondwire transformers fabricated and assembled with standard IC bonding wires and toroidal ferrite as a magnetic core. The micro-transformer realized on a PCB substrate enables the build of magnetics on-top-of-chip thus leading to the design of high power density components . Impedance measurements in a frequency range between 100 kHz to 5 MHz show that secondary self-inductance is enhanced from 300 nH with an epoxy core to 315 μH with a ferrite toroidal core. Moreover the micro-machined ferrite improves the coupling coefficient from 0.1 to 0.9 and increases the effective turns ratio from 0.5 to 35. Finally an IC integrated solution with the transformer mounted on-top of a low-voltage DC-DC converter for energy harvesting applications is propose
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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