1,721,007 research outputs found
Analysis of a Microwave Graphene-Based Patch Antenna
No full textThe possibility of using graphene-based antennas is
a core point in the development of high speed, multifunctional
devices, leading to a new generation of smart nano-systems for
wireless applications. In this work, we present a first analysis
of the electromagnetic radiation from graphene-based antennas,
at microwave frequencies. Moreover, a numerical analysis of the
coupling between graphene patches is reporte
Graphene-based Schottky diode integrated with a graphene bow-tie antenna for energy harvesting in the THz frequency band
No full textDesign of a Coplanar Graphene-Based Nano-Patch Antenna for Microwave Applications
No full textWe analyze a coplanar graphene-based nanopatch
antenna. Besides the fact that graphene is a moderate
conductor at those frequencies, the antenna can still exhibit
sharp resonances. Although the poor graphene conductivity
implies in general low-performance, a remarkable change of the
scattering parameters, radiation pattern and antenna efficiency
can be observed as the graphene surface impedance is changed
by means of an external Bias
Design considerations for tunnel diode non-linear transmission lines
No full textA tunnel diode non-linear transmission line has been investigated for second and third harmonic generation purposes. Design criteria are given and performance predictions have been obtained simulating the single diode behavior by means of a polynomial expression. An optimization of the non-linear transmission line as a harmonic generator has been obtained as a function of the number of diodes, their separation distances and the bias voltage
Exploitation of graphene as HIS and RIS for devices in the MW and THz frequency ranges
No full textGraphene has become an outstanding material for revolutionary wireless applications in the microwave and terahertz/infrared frequency ranges. Due to its unique physical characteristics, a family of completely new devices can be developed by exploiting graphene’s behaviour as High Impedance Surface (HIS) or highly-Reactive Impedance Surface (RIS). In this paper we theoretically investigate first a 10 GHz-resonant gold dipole antenna suspended over a graphene flake acting as a HIS reflector: the radiator can be placed at a very close distance from the graphene ground by keeping at the same time very good radiation performance with respect to classical metal reflectors. Second, we consider a gold dipole antenna operating at 10 THz directly attached to a graphene layer. Excellent radiation performance can be achieved thanks to the highly-inductive surface impedance of graphene at such high frequencies. An in-depth description of the possibility of varying graphene’s conductivity by means of an applied gate voltage is provided, thus demonstrating how radiating properties can be tuned by simply applying a proper voltage to the reflector. Hence, the proposed antennas can be considered in reason as the starting point for innovative graphene-based mm- and μm-systems with unique tunability properties
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
27-GHz Silicon-Integrated Rectenna Based on Novel Multilayer Substrate
No full textThis paper presents the design, fabrication, and characterization of a multi-layer 27-GHz rectenna integrated entirely on silicon, aimed at achieving full CMOS compatibility for energy harvesting applications. The device is fabricated on a high-resistivity silicon (HRSi) substrate, which is selectively etched to create a low-permittivity region for the antenna while maintaining a high-permittivity full substrate for the rectifier circuit. The rectenna, operating in the millimeter-wave (mmWave) band, features a compact single-cell design with dimensions of 13 x 13 mm2 only, making it suitable for integrating IoT devices to support energy autonomy. The rectenna utilizes a GaAs diode rectifier and achieves a measured maximum RF-to-DC power conversion efficiency (PCE) of about 49% at an input power of 12 dBm. This work demonstrates the potential of HRSi-based, silicon-integrated rectennas for efficient energy harvesting in IoT applications. The proposed multilayer fabrication technology allows the realization of high-radiation-efficiency directive antennas and RF circuits directly onto the CMOS substrate, without increasing the overall size of the circuit and maintaining the structural integrity of the device
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
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