1,721,075 research outputs found
Evolutionary algorithm for bandstop Frequency Selective Surface
No full textIn recent years,there has been an increasing interest on the study of Frequency Selective Surfaces, thanks to their particular electromagnetic properties. One among their broad range of applications is band-stop spatial filter, which is constructed by periodic arrays of usually metallic elements on a dielectric substrate. This paper will present the effectiveness of an Evolutionary Algorithm, namely Meta-PSO, in optimizing multi-dimensional electromagnetic problem. All these concepts are integrated into a case study of dual rectangular ring loop-type frequency selective surface, printed on a FR4 substrate
Optimization of Scattered Far Field of Multiple Magnetic Dipoles on Doubly-Coated Spheroids
No full textIn engineering optimization, the key challenge is often how to properly model the electromagnetic problem. Available simulators are robust, but they cannot always fully describe a number of physical phenomena, including boundary-value problems. The exact radiation of a magnetic dipole located on the symmetry axis of confocal prolate spheroids is determined by separations of variables. In this letter, the feasibility of integrating stochastic optimizer, namely Meta-PSO, and analytical solutions to optimize the radiated far field of multiple dipoles on doubly-coated prolate spheroids is presented and discussed
Exact radiation from dipole antennas on prolate and oblate spheroids coated with two confocal layers of different materials
No full textMetallic prolate and oblate spheroids are coated with two confocal layers of penetrable materials. One layer is isorefractive and the other layer is anti-isorefractive to the space surrounding the structure, thus resulting in four possible configurations. The primary source is an electric or magnetic dipole located on the symmetry axis of the spheroids and axially oriented. Exact solutions to the radiation problem are obtained in the frequency domain, in terms of infinite series of spheroidal wave functions. Numerical results are displayed and discussed
Multi-Net ANN approach for improving antenna optimization
No full textn recent years, evolutionary algorithms have been successfully adopted for the optimization of various electromagnetic problems. One of the most common electromagnetic application is in the framework of microstrip antennas, thanks to the advantage of being low cost and low profile. In order to reduce the computational effort of the electromagnetic optimization, a suitable equivalent model by ANN has been created in order to substitute the commercially available full-wave analysis solvers. In this article, a new solution for multiple-output problem is presented. All the concepts will be integrated into the optimization of multi-layer proximity coupled feed microstrip antenna. Numerical results and efficiency have been reported in order to enlighten the effectiveness of the proposed approach
Antenna optimization based on artificial neural network
No full textn literature heuristic algorithms have been successfully applied to a number of electromagnetic problems. There are a number of approaches to build up the associated cost functions, the most common one is to link with full-wave analysis. However, this modelling method always leads to the point of complexity and high computational expense. Artificial Neural Network is one of the most robust biological inspired technique. In this article, a fast and accurate model is trained to replace the full-wave analysis in optimizing the bandwidth of a microstrip antenna. The comparison between ANN substitution model and full-wave characterization shows significant improvements in time convergence and computational cost. To verify the capability of proposed model, all these concepts are included in a case study of a rectangular ring antenna with proximity-coupled feed antenna
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
Hybridization strategy for microstrip antenna optimization
Full text linkIn the exploding growth of radio mobile and wireless communication applications, microstrip antennas with its advantages of low cost and flexible fabrications, emerge as the most suitable candidate. The direct antenna synthesis could, however do not result in the optimal antenna configuration, and therefore a possible alternative is considering the problem of optimizing the antenna as a system of uncertainty, in which each set of geometrical parameters returns a totally different response; the best set, i.e. the one that gives the best antenna performances, can be obtained using global optimizers, as evolutionary algorithms. The main drawback of this approach is that it is really time and memory consuming. In this article, a technique based on the hybridization between Particle Swarm Optimization (PSO) and Artificial Neural Network (ANN)is introduced with the aim of reducing this nimerical cost and implemented to optimize a dual-annular ring proximity coupled feed antenna
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
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