1,721,265 research outputs found
Electromagnetic Field Coupling between a Horizontal Loop Antenna and a Transmission Line: An Analytical Time-Domain Model
No full textThe time-domain electromagnetic (EM) reciprocity theorem and the Cagniard-DeHoop technique are applied to analyze the pulsed EM coupling between a horizontal small loop antenna and a finite transmission line above the perfect ground. It is demonstrated that this approach yields closed-form analytical formulas describing the impact of transmission, EM propagation, and reception on the exciting pulse signature. Moreover, approximate expressions applying to relatively short transmission lines are given and discussed, thus revealing similarities with the loop-to-loop EM coupling. Numerical results are presented and validated using an alternative analytical solution and an EM computational tool
Transient Close-Range Electromagnetic Field Coupling between Loop Antennas at the Interface of Dissipative Half-Spaces
No full textThe problem of electromagnetic (EM) field short-range coupling between coplanar loop antennas located at the interface of two half-spaces with dielectric and conductive properties is solved analytically in the time domain (TD) via the Cagniard-DeHoop (CdH) technique under the diffusive approximation. It is demonstrated that the thus obtained closed-form TD analytical expressions can be applied to evaluate the close-range EM-field signal transfer between two loops lying on the surface of a dissipative half-space
Lightning-Induced Voltages on Transmission Lines over a Lossy Ground-An Analytical Coupling Model Based on the Cooray-Rubinstein Formula
No full textSpace-time closed-form expressions for the vertical-electric-dipole-induced Thévenin-voltage responses on a transmission line above a lossy ground are derived analytically. The problem is formulated via the electromagnetic reciprocity theorem of the time-convolution type and subsequently solved with the aid of the Cooray-Rubinstein formula and the Cagniard-de Hoop method. It is demonstrated that the obtained results are readily applicable to calculating lightning-induced voltages on overhead transmission lines over a finitely conducting ground
Electromagnetic Field Coupling to a Transmission Line - A Reciprocity-Based Approach
No full textThe electromagnetic (EM) reciprocity theorem of the time-convolution type is systematically applied to describe an EM-field-to-line coupling model interrelating the (actual) induced voltage and current quantities at the ends of a transmission line with the (testing) ones pertaining to the situation when the line operates as a transmitter. It is demonstrated that under certain conditions, the reciprocity-based coupling model is fully equivalent to the classic models of Agrawal, Taylor, and Rachidi. Furthermore, it is shown for the case of plane-wave incidence that the far-field amplitude radiated in the testing state can be used to replace the forcing functions that are traditionally expressed in terms of the excitation-field distribution along the transmission line. The reciprocity-based formulation is finally validated both analytically and numerically
Cagniard-DeHoop Technique-Based Computation of Retarded Partial Coefficients: The Coplanar Case
Full text linkEfficient computation of partial elements plays a key role in the Partial Element Equivalent Circuit (PEEC) method. A novel analytical method for computing retarded partial coefficients based on the Cagniard-DeHoop (CdH) technique is proposed. The methodology is first theoretically developed and then illustrated on the computation of a surface retarded partial coefficient pertaining to two coplanar rectangular surface elements. An efficient way for incorporating loss mechanisms in the time domain (TD) via the Schouten-Van der Pol theorem is proposed. Illustrative numerical examples demonstrating the validity of the introduced solution are given
Pulsed Electromagnetic Excitation of a Thin Wire – an Approximate Numerical Model Based on the Cagniard-DeHoop Method of Moments
Full text linkAn approximate computational model of an electromagnetic (EM) pulse excited thin-wire antenna is developed. The presented solution methodology is based on the Cagniard-deHoop method of moments (CdH-MoM) and Hallén's approximation of the thin-wire model. It is shown that the proposed time-domain (TD) solution leads to an inversion-free, efficient updating procedure that mitigates the marching-on-in-time accumulation error. An illustrative numerical example demonstrates the validity of the proposed model
Pulsed EM field transfer between a horizontal electric dipole and a transmission line: A closed-form model based on the Cagniard-DeHoop technique
No full textThe pulsed electromagnetic (EM) field transfer between a horizontal electric dipole (HED) and a transmission line is described analytically with the aid of the time-domain (TD) reciprocity theorem and the Cagniard-de Hoop technique. A suitably chosen wave-slowness representation makes it possible to cast the pertaining interaction integrals into a form amenable to analytical solution. The closed-form coupling model thus obtained clearly reveals the dependence of configurational parameters on the wireless signal transfer. Numerical results are presented and validated using a 3-D EM computational tool.Electrical Engineering Educatio
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
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