1,720,965 research outputs found
Cyclic Symmetry in Volume Integral Formulations for Eddy Currents: Cohomology Computation and Gauging
No full textThis contribution addresses the solution of eddy-current problems by means of a volume integral formulation based on the electric vector potential on a computational domain that exhibits a cyclic symmetry. Even if grids discretizing the domain are typically composed of tetrahedral or hexahedral elements, the proposed approach also works for general polyhedral meshes, such as those ones obtained by subgridding. In this article, an algorithm to compute a set of suitable cohomology generators needed when the conductors are not simply connected is introduced first. Besides being purely combinatorial, with linear-time worst case complexity and suitable with polyhedral meshes, it reuses a code that computes generators for triangular surface meshes, with obvious advantages concerning the implementation effort. Second, the formulation and the algorithm for cohomology computation are tweaked to be able to solve eddy-current problems with cyclic symmetry reserving specific attention to the construction of suitable tree-cotree decomposition for the problem gauging
A Fast and Efficient Simulation Method for Inductive Position Sensors Design
No full textInductive position sensors (IPSs) are contactless sensors used for detecting the absolute position of an item in case of angular or linear motion. The active sensing part is manufactured by positioning copper traces on a printed circuit board (PCB) in order to obtain a system of transmitting and receiving coils. A designing procedure based on trial-and-error method is not considerable because of the low time and costs efficiency of the process. Therefore, the here presented coil design process aims at efficiently evaluating the performance of each sensor before its industrial production and application. The simulation is based on the sequential solution of different eddy current problems in the frequency domain by using a fast and efficient surface integral formulation in place of the much more widely diffused commercial finite element (FE) codes. Due to this innovative practice, simulation time can be reduced to some tens of seconds thus allowing the evaluation of many design and the final performance of the sensor can be deeply enhanced, reducing the maximum linearity error from more than 2% up to 0.2% FS
Simulation and measurements of a rotary inductive position sensor
No full textIn this work a method for the fast simulation of a rotary inductive position sensor with the Surface Integral Method in order to predict the non linearity error of the sensor is provided. Experimental analysis shows the effectiveness of the method and the effect of the rotation speed on the receivers
Foundations of volume integral methods for eddy current problems
No full textIntegral methods for solving eddy current problems use Biot–Savart law to produce non-local constitutive relations that lead to fully populated generalized mass matrices, better known as inductance matrices. These formulations are appealing because—unlike standard Finite Element solutions—they avoid the generation of a mesh in the insulating regions. The aim of this paper is to alleviate the three main problems of volume integral methods. First, the computation of the inductance matrix elements is slow and also delicate because of the singularity in the integral equation. This paper introduces novel face basis functions that allow a much faster inductance matrix construction with respect to the standard one based on the Rao–Wilton–Glisson (RWG) or Raviart–Thomas (RT) basis functions. Second, our basis functions work for polyhedral elements formed by any number of faces (including prisms, hexahedra and pyramids), while producing the same results as RWG and RT basis functions for tetrahedral meshes. Third, the new basis functions allow to factorize the inductance matrix and to introduce a novel family of groundbreaking low-rank inductance matrix compression techniques that show several orders of magnitude improvement in memory occupation and computational effort than state-of-the-art alternatives, allowing to solve problems that otherwise cannot be faced
Mirror Symmetry in Integral Formulations for Eddy Currents
No full textThis contribution addresses the exploitation of mirror symmetry (formally, the abelian D1 and D2 dihedral symmetry groups) in various integral formulations for eddy current problems. The novelty of the contribution is in particular how to rigorously treat non simply-connected conductors when computing first cohomology group generators on the symmetry cell of the problem only
Fast Iterative Schemes for the Solution of Eddy-Current Problems Featuring Multiple Conductors by Integral Formulations
No full textIntegral formulations lead to full matrices that, despite the use of efficient low-rank approximation techniques, are impossible to be solved when the number of unknowns is large enough. To overcome this limitation, we propose a novel direct-iterative hybrid technique to solve eddy currents by taking advantage of the domain splitting into disjoint conductors: each subproblem is solved via direct solvers on each subdomain, whereas the Krylov subspace techniques are applied to compute the mutual effects between the substructures iteratively. In this way, the entries related to the mutual contributions between the subdomains are not stored. In particular, this article focuses on testing the convergence of the iterative method
Exploiting Cyclic Symmetry in Stream Function-Based Boundary Integral Formulations
No full textThis contribution addresses the exploitation of cyclic symmetry in boundary integral formulations for eddy current problemsformulated with a magnetic scalar potential. The novelty of the contribution is how to rigorously treat non-simply connectedconductors. In particular, a general algorithm to compute a set of suitable cohomology generators is introduced. The algorithm ispurely combinatorial and exhibits a linear-time worst-case complexit
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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