1,720,958 research outputs found
Wiener-Hopf analysis of the diffraction due to a dielectrically loaded finite thin slot
No full textThe diffraction due to a finite thin slot antenna in a perfectly conducting plane loaded by a dielectric stratified structure was addressed in this paper. A perfectly conducting plane shield is introduced between two volumes, one is filled with air, the other one presents a dielectric stratified structure
Shape analysis and efficiency of arrays of microstrip patch antennas for wireless sensor networks
No full textWith the advancement of wireless communication systems, low cost, minimal weight, compact and low profile antennas are in great demand for both commercial and military applications. Furthermore, as the size of wireless hand-held devices shrinks, it is desirable to integrate the antenna directly on the chip package to cut down cost and provide flexible integration. Conformal low-profile antennas, such as printed dipoles, rectangular patches and slots, are widely used in large arrays on ground based, vehicular, air-borne and shipboard applications. Microstrip patches are usually used as radiating elements also in arrays and planar reflector antennas. These traditional resonant structures are typically half a wavelength in the critical dimensions and have relatively narrow bandwidth. In order to overcome these limitations, circular and annular shaped microstrip elements can be used, where the resonant dimension is related to half the circumference. This leads to a more compact solution, since for the same frequency the size of the patch is smaller. Another advantage of this solution is the possibility of working with double polarization. This paper investigates the performances of microstrip elements with circular annular shapes and suitable additional geometrical features, such as slots, to control the resonance behavior. Especially, a study of efficiency of the antenna has been done. The idea is to use a ring of EBG (electromagnetic band gap) material in order to reduce the surface wave and therefore to increase the antenna efficiency in terms of both received and radiated power by the whole antenna.
The analysis process is done in three steps. First, we characterized the patch in term of an equivalent circuit model. Then we investigated the mutual coupling of an array of patches. Finally we developed a suitable EBG ring in order to increase the efficiency of the antenna. The last operation is important for the optimization and design process
Shape Sensitivity Analysis Of Microstrip Patch Antenna For Use In An Wireless Sensor Net
No full textWith the advancement of wireless communication systems, low cost, minimal weight, compact and low profile antennas are in great demand for both commercial and military applications. Furthermore, as the size of wireless hand-held devices shrinks, it is desirable to integrate the antenna directly on the chip package to cut down cost and provide flexible integration. Conformal low-profile antennas, such as printed dipoles, rectangular patches and slots, are widely used in large arrays on ground based, vehicular, air-borne and shipboard applications. Microstrip patches are usually used as radiating elements also in arrays and planar reflector antennas. These traditional resonant structures are typically half a wavelength in the critical dimensions and have relatively narrow bandwidth. In order to overcome these limitations, circular and annular shaped microstrip elements can be used, where the resonant dimension is related to half the circumference. This leads to a more compact solution, since for the same frequency the size of the patch is smaller. Another advantage of this solution is the possibility of working with double polarization. This paper investigates the performances of microstrip elements with circular annular shapes and suitable additional geometrical features, such as slots, to control the resonance behavior. In this work, both classical shapes (like rectangles, dipoles and rings) and the novel slotted annular patch are analyzed and compared. Figures of merit of the element performance are the bandwidth and the polarization. The shapes analyzed are suitable and versatile for use in a wireless net, both in the sensors and in the main receiver
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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