1,720,978 research outputs found
Design of an EBG structure by using a transmission line model
No full textAbstract - This paper presents an efficient circuital model based
on a transmission line technique to design a planar circularly
symmetric ERG structure that surrounds a patch antenna
working at 2.45 GHz.
The ERG structure, being printed on the same layer board of the
antenna, is easy to fabricate, prevents the propagation of surface waves and increases the bandwidth and the directivity of the patch antenna
Transmission line model for meander antennas
No full textNowadays valuable and efficient numerical methods allow an empirical approach in the design of antennas for high-frequency wireless communication systems. Generally these numerical techniques apply either time- or frequency-domain algorithms demanding high computational efforts and long-time processing. Moreover, the initially assumed geometrical configuration can strongly affect the numerical convergence efficiency. With reference to a meander antenna, this paper highlights the computational improvement achievable by applying a transmission line model to the definition of an initial geometry, to be numerically optimized, the sizes of which are nearly to the final ones
An Analytical 3D Model of Metal Foams for EM Shielding Applications
No full textIn this paper a preliminary electromagnetic shielding behaviour of metal foams, is developed and discussed. Metal foams represent a novel class of materials which promise new interesting properties employable for various purposes. More specifically, the realization of electromagnetic shields has been considered and experimental Shielding Effectiveness (SE) measurements have been performed, demonstrating very good performance. In order to allow the design of metal foam EM shields, double 3D wire-mesh screens, obtained as a development of a previously 2D laminated shield, has been presented, comparing the relative results with experimental measure. The good agreement among the preliminary data paves the way to obtain an efficient analytical model of the complex electromagnetic behavior of metal foams
E-field distribution improvement by new hyperthermia applicators
No full textIt is well known that the hyperthermia (HT)
treatment method in cancer therapy makes use of the controlled
electromagnetic heating in the patient’s body. With regard to the
deep body hyperthermia therapy, we have reviewed in this paper
the most recent technology and technique of electromagnetic
deep heating (Sigma-Eye applicator) based on annular phased
arrays (APA) antennas. In order to improve the performance of
the Sigma-Eye applicator, a new profile of the antenna was
designed using a substrate material with high permittivity. The
good results of the simulations compared with the classical
Sigma-Eye applicator in terms of SAR deposition and focus
capability lead us to further improvements of both the heat
generation devices and the treatment planning methods
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
Valorization of cigarette butts for synthesis of levulinic acid as top value-added chemicals
Full text linkUnprecedented in the literature, levulinic acid (LA), one of the top value-added intermediates of chemical industry, is obtained from cigarette butts as cellulose feedstock by means of a one-pot hydrothermal process carried out at 200 °C for 2 h and catalysed by phosphoric acid. The protocol avoids the use of more aggressive and toxic H2SO4 and HCl, that are generally employed on several cellulose sources (e.g. sludge paper), thus minimizing corrosion phenomena of plants. Neither chemical pre-treatment of butts nor specific purification procedure of LA are required. Notably, by simply modifying acid catalyst (e.g. using CH3COOH), another top value-added fine chemical such as 5-hydroxymethylfuraldehyde (HMF) is obtained, thus widening the scope of the method. Being cigarette filters a waste available in quantities of megatonnes per year, they represent an unlimited at no cost source of cellulose, thus enabling the up-scale to an industrial level of LA production
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