1,720,964 research outputs found
A Direction-of-Arrival Approach for the Subsurface Localization of a Dielectric Object
No full text"In this paper, a technique based on Sub-Array Processing and Direction of Arrival estimation is applied, for the localization of buried cavities and dielectric cylinders. The same approach has been previously employed for the sensing of perfectly-conducting objects, with good results. Here, several scenarios are examined, assuming different permittivity values for both the scatterer and hosting medium. The position and size of the cylinder are also varied. Results for air cavity detection are particularly interesting. The proposed procedure can be useful for near-surface probing applications.
Application of a SAP-DoA method to GPR data for the location of reinforcing elements in concrete
No full textA Sub-Array Processing approach was recently developed and implemented by the Authors, to detect targets lying in the near field of an antenna array. In such method, an array of receivers is partitioned in sub-arrays; for each of them, the number of incoming signals and their directions are predicted by using Direction-of-Arrival algorithms. In this paper, the technique is revised and extended to the case of ultra wideband signals, in order to investigate its applicability to Ground-Penetrating Radar (GPR) data processing. Tests are performed on reference synthetic data, calculated by using a freeware tool implementing the finite-difference time-domain method and included in the database of COST Action TU1208 "Civil engineering applications of Ground Penetrating Radar." In particular, three concrete cells are considered: the first cell hosts five circular-section steel rods, with different radii and positions, in the second cell four metallic and dielectric rods are embedded, in the third cell an angle bar, a box section and a u-channel are present. The first and second tests aimed at demonstrating the capability of the procedure to correctly locate multiple objects in concrete. The third more ambitious test aimed at verifying whether the procedure could distinguish between different shapes of typical reinforced concrete elements. This work was carried out within the Short-Term Scientific Mission COST-STSM-TU1208-26649. The paper is concluded with a brief overview of the activities carried out within Working Group 3 of COST Action TU1208, dealing with the development of electromagnetic modelling, imaging, inversion and data-processing tools for GPR
SPOT-GPR: a freeware tool for target detection and localizationin GPR data developed within the COST action TU1208
Full text linkSPOT-GPR (release 1.0) is a new freeware tool implementing an innovative Sub-Array Processing method, for the analysis of Ground-Penetrating Radar (GPR) data with the main purposes of detecting and localizing targets. The software is implemented in Matlab, it has a graphical user interface and a short manual. This work is the outcome of a series of three Short-Term Scientific Missions (STSMs) funded by European COoperation in Science and Technology (COST) and carried out in the framework of the COST Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar” (www.GPRadar.eu). The input of the software is a GPR radargram (B-scan). The radargram is partitioned in subradargrams, composed of a few traces (A-scans) each. The multi-frequency information enclosed in each trace is exploited and a set of dominant Directions of Arrival (DoA) of the electromagnetic field is calculated for each sub-radargram. The estimated angles are triangulated, obtaining a pattern of crossings that are condensed around target locations. Such pattern is filtered, in order to remove a noisy background of unwanted crossings, and is then processed by applying a statistical procedure. Finally, the targets are detected and their positions are predicted. For DoA estimation, the MUltiple SIgnal Classification (MUSIC) algorithm is employed, in combination with the matched filter technique. To the best of our knowledge, this is the first time the matched filter technique is used for the processing of GPR data. The software has been tested on GPR synthetic radargrams, calculated by using the finite-difference timedomain simulator gprMax, with very good results
Detection of buried objects by means of a SAP technique: Comparing MUSIC- and SVR-based approaches
No full textA SAP-DoA Method for the Localization of Two Buried Objects
Full text linkA localization technique for buried metallic and dielectric objects is proposed and tested. An array of isotropic antennas investigates a scenario with cylindrical targets buried in a dielectric soil. The targets are in the near field of the array, and a Sub-Array Processing (SAP) approach is adopted: the array is partitioned into subarrays, and Direction of Arrival (DoA) algorithms are used to process the electromagnetic field received by each subarray and estimate the dominant arrival direction of the signal. By triangulating all the estimated DoAs, a crossing pattern is obtained. It is filtered by a Poisson-based procedure and subsequently elaborated by the -means clustering method in order to distinguish between targets and background, estimate the number of targets, and find their position. Several simulations have been performed to compare different DoA algorithms and to test the localization method in the presence of two buried cylinders. Different values of the permittivity of the involved dielectric materials have been considered; the target positions and size have also been varied. The proposed procedure can be useful for ground-penetrating radar applications, near-surface probing, and for the detection and localization of defects in a hosting medium
Detection of subsurface metallic utilities by means of a SAP technique: Comparing MUSIC- and SVM-based approaches
No full text"The identification of buried cables, pipes, conduits, and other cylindrical utilities is a very important task in civil engineering. In the last years, several methods have been proposed in the literature for tackling this problem Most commonly employed approaches are based on the use of Ground Penetrating Radars, i.e., they extract the needed information about the unknown scenario starting from the electromagnetic field collected by a set of antennas. In the present paper, a statistical method, based on the use of smart antenna techniques, is used for the localization of a single buried object In particular, two efficient algorithms for the estimation of the directions of arrival of the electromagnetic waves scattered by the targets, namely the MUltiple SIgnal Classification and the Support Vector Regression, are considered and their performances are compared. (c) 2013 Elsevier B.V. All rights reserved.
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
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