1,720,989 research outputs found
Innovative antenna designs : Performance and application diversity
Full text linkAdvanced antenna and propagation technology will play a crucial role in transforming the way we live, work, and engage with our environment in order to catch up with the developing technologies. The choice of an antenna system for a specific application will also be a critical component of all nodes and devices and will present several design challenges such as purpose, shape, and placement. In this edited book, the authors bring new approaches for exploiting challenging propagation channels and the development of efficient, cost-effective, scalable, and reliable antenna and other related systems. Various current state-of-the-art technologies have been discussed and future perspectives have been highlighted.
The book is aimed at a wide audience of industry and academic researchers, scientists, and engineers as well as advanced students in the field of antenna, propagation, and related topics. The audience can also use the discussed topics to better understand the effects of the technology on the current market and future developments of advanced communication systems
Development of switchable planar reflectors for beam shaping realization
No full textThis work provides an extensive analysis for the design and performance optimization of planar reflectors within X-band and Ku-band frequency ranges. The objective of this work was to investigate the feasibility of using strategic slot embedded patch element configurations for an efficient reconfigurable reflectarray antenna design. PIN diodes were incorporated with single and multiple slot embedded patch element configurations for the design of beam switchable planar reflectors. Moreover unit cells based on liquid crystal substrates were also designed for comparison between two reconfigurable planar reflector design techniques. 3Dimensional electromagnetic computer models of CST Microwave Studio and Ansoft HFSS were used for the simulations and the results of unit cells were practically verified by waveguide scattering parameter measurements using vector network analyzer. Performance characterization for bandwidth and reflection loss optimization of different slot embedded patch configurations was done based on the scattering parameter measurements. Maximum frequency variation of 2.56GHz with dynamic phase range of 346 ̊ in X-band was demonstrated by rectangular slots in the centre and circular slots along width configuration while Ku-band measured results demonstrated a maximum frequency variation of 2.54GHz with dynamic phase range of 278 ̊ for circular slot with gap configuration. The measured scattering parameter results for the PIN diodes based elements designed in X-band frequency range are shown to provide a maximum frequency tunability of 0.55GHz with 238 ̊ of dynamic phase range in the case of embedded rectangular slots in the centre of patch element. On the other hand liquid crystal based embedded rectangular slots unit cells designed in X-band frequency range are shown to demonstrate comparatively lesser frequency tunability of 0.12GHz with dynamic phase range of 103 ̊. Although liquid crystal based design is shown to offer good frequency tunability and dynamic phase range, however the loss associated with liquid crystals is one of the limitations of this design. Higher tunable loss factor of 1.91dB was demonstrated by liquid crystal based design as compared to tunable loss factor of 1.43dB shown by PIN diode based design. The investigations were further extended by carrying out equivalent circuit analysis of PIN diode based and liquid crystal based designs for detailed characterization of reconfigurable planar reflector designs. Equivalent circuit model is demonstrated to offer a very close agreement between the simulated and scattering parameter measured results where a maximum discrepancy of 0.1dB was observed. A comprehensive mathematical model based on Finite Element Method (FEM) was proposed for progressive phase distribution to develop a novel design technique to create a reconfigurable reflectarray antenna based on strategic slot configurations. The developed model permits the positioning of an individual element of the array, required for progressive phase distribution, independent of its geometrical structure. Furthermore the developed algorithm can be used for both centre fed and off-set fed planar reflector designs while incorporating the effect of material properties of conductor and substrate. Three novel robust periodic reflectarray configurations, consisting of 144, 64 and 36 elements respectively were designed and fabricated for far-field radiation pattern measurements. The measured radiation patterns are shown to offer close agreement with the predicted results where switchable array based on PIN diodes confirmed a beam switching of +6 ̊,0 ̊and -6 ̊ while the passive 144, 64 and 36 elements arrays are observed to give maximum 3dB beamwidth of 10.5 ̊, 11.4 ̊ and 13.2 ̊ respectively
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
