1,720,964 research outputs found
Design of a RF-to-dc Link for in-body IR-WPT with a Capsule-shaped Rotation-insensitive Receiver
No full textThis paper proposes the design and experimental validations of a 6.78 MHz IR-WPT with one conformal transmitter (Tx) and a couple of receiver (Rx) coils, suitable for powering implantable devices. The Rx coils are arranged in such a way that quasi-constant dc-output voltage and conversion efficiency are obtained, regardless of the receiver rotation, with respect to the transmitter. A 3-D miniaturized receiver, consisting of two elliptical coils wrapped around a capsule and orthogonal to each other, is faced to a conformal transmitter designed to maximize the magnetic flux in the receiver region. In order to avoid dark areas for energy transfer, due to unknown capsule rotations, each Rx coil is connected to one rectifier and the dc output ports are series-connected
Criticality mitigation in a quasi-constant coupling position independent resonant IPT network
No full textThis paper discusses some significant design issues that are faced in resonant inductive system for wireless power transfer ‘on the move’. The targeted system adopts a single AC source to power a sequence of transmitting (Tx) coils, placed along the Rx path, whose geometry is optimized to minimize the variations of coupling for every possible Rx position. To retain a constant coupling coefficient, two nearby Tx coils are series-connected and simultaneously activated, establishing a path without any theoretical bound on its length, by a suitable switching network. This work analyzes the effects of asynchronous switching times, which are rigorously accounted for and minimized by a proper design of the compensating circuit elements, minimizing both the voltage spikes and the over currents on the coils, while keeping the system at resonance. A prototype operating at 6.78 MHz is built and experimental validations are carried out to verify the feasibility of a constant coupling link without experiencing the mentioned effects, but the adopted procedure is general and independent on its size or frequency
Geometry optimization of sliding inductive links for position-independent wireless power transfer
No full textIn this paper we describe a geometry design solution to minimize performance variations of a wireless power transfer system “on the move” (WPT-Mob). A sequence of switchable couples of coils, connected in series or in parallel, is adopted at the fixed transmitting link side; the geometry of the moving receiver is optimized to keep the coupling factor, and thus the power transfer, constant during the movement. First the analytical formulation of the link coupling factor is derived as a function of its circuit-equivalent parameters computed by full-wave simulation. Then selected geometry parameters of the receiver side are optimized to keep the coupling factor constant while the link is moving. A set of TX-RX arrangements are simultaneously analysed to emulate the sliding movement of the WPT-Mob. The final optimized geometry demonstrates that a constant power transfer on-the-move is enabled, even for variable TX-to-RX link distances. Design and experimental verification are carried out for a geometry suitable for medium power transfer (tens of Watts) at 6.78 MHz, but the method is formulated in such a way that the system can be scaled up and down to accomplish different application needs.© Copyright IEEE – All rights reserved.
Published version available at https://doi.org/10.1109/MWSYM.2016.754007
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
Theoretical and experimental characterization of moving wireless power transfer systems
No full textThe idea of this paper is to develop a moving resonant wireless power transfer (WPT) system capable of keeping the coupling factor, and thus the power transfer, invariable with respect to the reciprocal system sides positions. A typical scenario is the WPT to moving objects on a platform equipped with a sequence of coils underneath. If a single TX coil is active at a time, the receiver movement would cause the coupling coefficient, and consequently the transmitted power, to oscillate. To cope with this problem, in this work we propose to make use of two active Tx coils. Different coil geometries and coil connections have been investigated, trying to get an insight into the coupling mechanism. This have been done by full-wave simulations and measurements of the selected structures and by varying some key parameters of the geometry itself. The connections between coils have been done in post-processing and the results have been plotted for comparison. Future work has been proposed.© Copyright IEEE – All rights reserved.
Published version available at https://doi.org/10.1109/EuCAP.2016.748191
A theoretical and numerical approach for selecting miniaturized antenna topologies on magneto-dielectric substrates
Full text linkAn increasing interest is arising in developing miniaturized antennas in the microwave range. However, even when the adopted antennas dimensions are small compared with the wavelength, radiation performances have to be preserved to keep the system-operating conditions. For this purpose, magneto-dielectric materials are currently exploited as promising substrates, which allows us to reduce antenna dimensions by exploiting both relative permittivity and permeability. In this paper, we address generic antennas in resonant conditions and we develop a general theoretical approach, not based on simplified equivalent models, to establish topologies most suitable for exploiting high permeability and/or high-permittivity substrates, for miniaturization purposes. A novel definition of the region pertaining to the antenna near-field and of the associated field strength is proposed. It is then showed that radiation efficiency and bandwidth can be preserved only by a selected combinations of antenna topologies and substrate characteristics. Indeed, by the proposed independent approach, we confirm that non-dispersive magneto-dielectric materials with relative permeability greater than unit, can be efficiently adopted only by antennas that are mainly represented by equivalent magnetic sources. Conversely, if equivalent electric sources are involved, the antenna performances are significantly degraded. The theoretical results are validated by full-wave numerical simulations of reference topologies.
Published version available at: https://doi.org/10.1017/S1759078715000859Copyright Cambridge University Press and EuMA.
Published version available at: https://doi.org/10.1017/S1759078715000859
Subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms
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
Load- and Position-Independent Moving MHz WPT System Based on GaN-Distributed Current Sources
Full text linkThis paper describes the modeling, analysis, and design of a complete (dc-to-dc) inductive wireless power transfer (WPT) system for industrial moving applications. The system operates at 6.78 MHz and delivers up to 150 W to a load moving along a linear path, providing a quasi-constant dc output voltage and maintaining a zero voltage switching operation, regardless of position and load, without any retuning or feedback. The inductive link consists of an array of stationary transmitting coils and a moving receiving coil whose length is optimized to achieve a constant coupling coefficient along the path. Each Tx coil is individually driven by a constant amplitude and phase sinusoidal current that is generated from a GaN-based coupled load-independent Class EF inverter. Two adjacent transmitters are activated at a given time depending on the receiver’s position; this effectively creates a virtual series connection between the two transmitting coils. The Rx coil is connected to a passive Class E rectifier that is designed to maintain a constant dc output voltage independent of its load and position. Extensive experimental results are presented to show the performance over different loading conditions and positions. A peak dc-to-dc efficiency of 80% is achieved at 100 W of dc output power and a dc output voltage variation of less than 5% is measured over a load range from 30 to 500 Ω . The work in this paper is foreseen as a design solution for a high-efficient, maintenance-free, and reliable WPT system for powering sliders and mass movers in industrial automation plants
- …
