1,721,061 research outputs found
Sparse Ground Penetrating Radar Acquisition: Implication for Buried Landmine Localization and Reconstruction
No full textThe effectiveness of the ground penetrating radar (GPR) imaging process and its capability of correctly reconstructing buried objects is strictly bounded to a correct acquisition strategy, both in terms of data density and regularity. In some GPR applications, such as landmine detection, these requirements may not be fulfiled due to logistical limitations and environmental obstacles. In the light of autonomous platform, possibly driven by a positioning device, the knowledge of the maximum affordable grid irregularity is essential. This experimental work, employing a data set acquired at a landmine test site, provides a demonstration that the same information content could be maintained even with a sparser data grid, compared to the commonly adopted requirements, mitigating the pressing demand for a precise samples positioning
Influence of internal structure on landmine radar signatures
Get PDFCheap and easy to use, landmines are among the favourite weapons in civil wars and wars of insurgency and are used by governments and guerrillas alike. These 'eternal sentinels' stand guard long after the conflicts have ended and kill and maim without mercy or discrimination. Therefore, there is a pressing need to remove these devices and to clear the contaminated land. As many landmines have low metal content they are difficult to detect using traditional techniques such as metal detectors, hence Ground Penetrating Radar (GPR) is an attractive tool in landmine clearance. Many investigations of landmine detection using GPR make use of surrogate landmine targets, since real landmines are difficult to obtain. This paper investigates the importance of the fidelity of such surrogates in terms of their external design, internal structure and explosive content
Landmine Internal Structure Detection from Ground Penetrating Radar Images
Get PDFReliable landmine detection is still an unresolved problem. Demining operations are complex activities because of the large variety of existing landmine types, many different possible soil and terrain conditions, and environmental circumstances. Due to its ability of detecting both metallic and non-metallic objects, ground penetrating radar (GPR) is a promising method for detecting landmines that may allow faster and safer operations. As the performance of GPR is mainly governed by the target signature, the potential of discriminating target based on the presence of internal reflections could be a valuable advantage for identification and recognition process. This study demonstrates that from a set of high resolution GPR slices the internal design of the landmine can be properly imaged and characterised, confirming the applicability of the methodology and the validity of such an approach
Multi-perspective high range resolution profiles of landmines
Get PDFLandmine clearance is a severe and unresolved humanitarian issue. The development of low-cost, smaller, faster and lighter Ground Penetrating Radars (GPR), which can be mounted on unmanned platforms, will allow faster and safer 24/7 operations. This technology will make it possible to survey affected areas with more flexible trajectories and these will provide measurements of landmine signatures from many different aspect angles. As a result, multi-perspective information over wide angular windows and the behaviour of the signature as a function of the angle of illumination can be exploited. Landmine signatures are expected to present features that are less sensitive to the angle of illumination with respect to those of common cluttered objects, and this can lead to an improvement in detection and discrimination performance. In this paper, we present the results of an experimental trial carried out to collect the High Range Resolution Profiles (HRRPs) of two landmines, the SB-33 and the VS-50, off the ground. An analysis of the auto-correlation function of each range bin as a function of the aspect angle is presented together with that of the cross-correlation between profiles collected from different aspect angles
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dependence of landmine radar signature on aspect angle
Get PDFAntipersonnel landmines have been indiscriminately used since World War II, and their longterm persistence in the ground creates a barrier to development in a large number of countries, forcing people to live in constant fear. Therefore, there is a growing demand for reliable landmine inspection systems that could achieve an exhaustive detection to and return the land to its normal use. Due to its ability of detecting both metallic and non-metallic objects, Ground Penetrating Radar (GPR) has successfully been demonstrated to be a meaningful method for detecting landmines, allowing faster and safer operations. Most landmines may be considered as multiple layered dielectric cylinders, which each interface causes a reflection, properties that are hardly expected in other commonly encountered clutter objects. Considering that these features have their own angular pattern and will respond differently to different illumination, landmines are expected to produce signatures that present some discriminant features that could be used for reducing the false alarm rate of GPR equipment. In this paper, a set of measurements of three inert landmines has been acquired to study and characterise landmine signatures as a function of the antenna orientation relative to the landmine and target aspect angle.IET Radar Sonar and Navigatio
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