1,720,977 research outputs found
Bidirectional Monopole Antenna Array with Minimized Ground Plane for WLAN Applications
Full text linkThis paper proposes a new design of printed
monopole antenna array for WLAN applications. In order to
get rid of the parasitic effects of a uniform ground plane on the
array feeding network, the metal shape is specifically cut out to
minimize its interaction with the monopole while ensuring the
proper operation of the array feeding network. Simulations of
a 2-by-2, monopole antenna array with the optimized ground
plane shape shows that the array performance is significantly
improved with miniaturization of ground structure. These results
are validated by the measurements showing that the unique shape
of the ground structure increases the antenna gain by 1.75 dB
and decreases the side lobe level by 5.30 dB with respect to a
standard uniform ground
A Miniaturized Wearable Two-port Loop Rectenna for Energy Harvesting at millimeter wave
Full text link—The design of a novel two-port loop antenna, operating in the 30-GHz band, is proposed as the energy receiver
in a mm-wave WPT link, exploiting Bessel beam launchers
for power transmission. For wearable applications this solution
allows to combine the focusing capabilities of the launchers with
miniaturization, important requirements for wearable devices.
Starting from a rectangular loop length chosen to cover the main
beam area, its geometry is outfitted with meandered sections of
conductors that act as phase shifters, to ensure uniformity of field
distribution and getting rid of field nulls. To further enhance
field uniformity, two differential ports, placed in symmetrical
positions, are selected and the energy transfer capabilities of the
wireless link, consisting of the launcher and the modified loop, are
computed by numerical simulations for several distances, both in
air and in proximity of human tissues. Two identical differential
rectifiers, adopting mm-wave GaAs Schottky diodes, are designed
with the proposed two-port loop as the feeding network. An
RF-to-dc efficiency of 30 % is predicted for an RF power of
10 dBm at 31.67 GHz. The proposed system can be a feasible
solution to be used in compact WPT applications, particularly
when wearability, compactness, and lightness are require
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
Integrated Shielding and Energy Harvesting by an Optimized Near-field Metamaterial-based System
No full textCombined near-field shielding and energy harvesting using a magnetic metamaterial for low-frequency (85 kHz) inductive wireless power transfer (WPT) system is proposed. The paper discusses the potential applications of this technology, along with illustrating the key components and design considerations for energy harvesting through metamaterial-based shields. A reference case study is considered, and a constrained multi-objective optimisation is performed for the tuning of the metamaterial-based energy-harvesting system
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
Efficient Simulation Method for Wireless Power Transfer
No full textWith the development of the internet of things, it becomes necessary to wirelessly power distributed sensors. However, it is not straightforward to accurately estimate the available wireless power at certain points in a specific propagation scenario using traditional methods. This is due to the compro- mised accuracy for large problems and the long time required to run their simulation. In this paper, we present a novel model to accurately calculate the received power by distributed RF sensors using the wave integral equation solver and a developed calculation method using reciprocity theorem. The model is tested in a prototype to simulate a propagation scenario in harsh electromagnetic environments with a reverberation-like behaviour. The propagation scenario consists of a transmitter placed ahead of the prototype aperture and a receiver is moved inside the prototype and the obtained results are compared from both simulation and measurement to rigorously investigate their accuracy and model performance. Based on comparison with measurements and benchmarking with the time domain results, the proposed model is superior for both time and accuracy as it is 20 times faster and gives closer results to measurements than its time domain counterpart
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