Analysis of approximations and aperture distortion for 3D migration of bistatic radar data with the two-step approach

The two-step approach is a fast algorithm for 3D migration originally introduced to process zero-offset seismic data. Its application to monostatic GPR (Ground Penetrating Radar) data is straightforward. A direct extension of the algorithm for the application to bistatic radar data is possible provided that the TX-RX azimuth is constant. As for the zero-offset case, the two-step operator is exactly equivalent to the one-step 3D operator for a constant velocity medium and is an approximation of the one-step 3D operator for a medium where the velocity varies vertically. Two methods are explored for handling a heterogeneous medium; both are suitable for the application of the two-step approach, and they are compared in terms of accuracy of the final 3D operator. The aperture of the two-step operator is discussed, and a solution is proposed to optimize its shape. The analysis is of interest for any NDT application where the medium is expected to be heterogeneous, or where the antenna is not in direct contact with the medium (e.g., NDT of artworks, humanitarian demining, radar with air-launched antennas)

Multi-azimuth ground penetrating radar surveys to improve the imaging of complex fractures

Ground Penetrating Radar (GPR) images are affected, to some degree, by the relative orientation of antennas and subsurface targets. This is particularly true not only for targets that show a significant directivity, but also for inclined planes, such as fractures and faults. Depending on the relative geometry between the antennas and the orientation of the target, radar waves can be preferentially scattered, which causes changes in the reflected signal amplitude. Therefore, traditional single polarization and single azimuth surveys may produce inadequate results. The work presented here examines the use of a multi-azimuth GPR survey to increase the imaging performance of inclined fractures, showing the shortcomings of single-profile surveying and highlighting the benefits that such a strategy has on detection and characterization

Complementarietà delle indagini termografiche e georadar nella diagnostica degli edifici

Le indagini non distruttive sugli edifici stanno avendo un progressivo sviluppo nell’ingegneria civile. Le tecniche di geofisica applicata trovano in questo settore numerose applicazioni e stimoli per nuove ricerche. I restauratori e gli ingegneri civili, dall’applicazione di queste tecnologie richiedono informazioni sulla geometria degli elementi non visibili, sul loro stato di ammaloramento e sulla matrice che compone i materiali dell’edificio. Una tale quantità di informazioni eterogenee richiede l’utilizzo di più sistemi basati su principi fisici di funzionamento diversi. In questo lavoro ci si è occupati dell’analisi delle potenzialità di individuazione e ricostruzione delle geometrie degli elementi non visibili di un edificio. Le tecnologie considerate sono state la Termografia (attiva e passiva) e il Georadar, metodologie differenti nei principi fisici di funzionamento, nelle possibilità operative e investigative. È presentato il caso di studio di una campagna di misure sperimentali Georadar e Termografica su di un edificio storico per verificare la complementarietà delle due metodologie

Landmine Detection From Gpr Data Using Convolutional Neural Networks

The presence of buried landmines is a serious threat in many areas around the World. Despite various techniques have been proposed in the literature to detect and recognize buried objects, automatic and easy to use systems providing accurate performance are still under research. Given the incredible results achieved by deep learning in many detection tasks, in this paper we propose a pipeline for buried landmine detection based on convolutional neural networks (CNNs) applied to ground-penetrating radar (GPR) images. The proposed algorithm is capable of recognizing whether a B-scan profile obtained from GPR acquisitions contains traces of buried mines. Validation of the presented system is carried out on real GPR acquisitions, albeit system training can be performed simply relying on synthetically generated data. Results show that it is possible to reach 95% of detection accuracy without training in real acquisition of landmine profiles. Document type: Conference objec

Safety Evaluation of New Polymer Materials Proposed for Relining Drinking Water Pipes in the City of Milano

Relining is a trenchless technology of recoating the inside walls of damaged water pipes using composite materials. In the Safe Pipe project, co-financed by Regione Lombardia, alternative polymeric materials for relining the drinking water distribution system of the city of Milan have been developed. Relining polymers have been evaluated for their toxicity. The identification of product impurities was performed by HPLC/HRMS and GC/MS analysis and safety evaluation was conducted applying toxicity data, when available, or applying QSAR models. Results showed low level of toxic substances in polymerized resins and in water samples in a migration/leaching test performed in a field experiment

Characterisation of the internal structure of landmines using ground penetrating radar

One of the principal limitations of employing Ground Penetrating Radar (GPR) for landmine detection is the presence of clutter, i.e. reflections from the surrounding environment which might interfere with the landmine echoes. Clutter presents similar scattering characteristics of typical targets and may significantly raise the detection threshold of the system. A capability to characterise the internal structure of a buried target might provide key unique information to develop advanced landmine-clutter discrimination algorithms, considering that the presence of internal scattering components can be univocally associated to man-made targets. In this paper, the possibility of identifying and characterising these contributions from the GPR signature of a landmine is numerically assessed and experimentally validated. The simulated response from a landmine-like target shows that the presence of the internal structure generates additional reflection peaks, as a consequence of the layered structure of the object, and the field trials corroborate that it is possible to identify these scattering components and delineate their spatial distribution

Convolutional Autoencoder for Landmine Detection on GPR Scans

Buried unexploded landmines are a serious threat in many countries all over the World. As many landmines are nowadays mostly plastic made, the use of ground penetrating radar (GPR) systems for their detection is gaining the trend. However, despite several techniques have been proposed, a safe automatic solution is far from being at hand. In this paper, we propose a landmine detection method based on convolutional autoencoder applied to B-scans acquired with a GPR. The proposed system leverages an anomaly detection pipeline: the autoencoder learns a description of B-scans clear of landmines, and detects landmine traces as anomalies. In doing so, the autoencoder never uses data containing landmine traces at training time. This allows to avoid making strong assumptions on the kind of landmines to detect, thus paving the way to detection of novel landmine models

In vitro recapitulation of the site-specific editing (to wild-type) of mutant IDS mRNA transcripts, and the characterization of IDS protein translated from the edited mRNAs

The transfer of genomic information into the primary RNA sequence can be altered by RNA editing. We have previously shown that genomic variants can be RNA-edited to wild-type. The presence of distinct “edited” iduronate 2-sulfatase (IDS) mRNA transcripts ex vivo evidenced the correction of a nonsense and frameshift variant, respectively, in three unrelated Hunter syndrome patients. This phenomenon was confirmed in various patient samples by a variety of techniques, and was quantified by single-nucleotide primer extension. Western blotting also confirmed the presence of IDS protein similar in size to the wild-type. Since preliminary experimental evidence suggested that the “corrected” IDS proteins produced by the patients were similar in molecular weight and net charge to their wild-type counterparts, an in vitro system employing different cell types was established to recapitulate the site-specific editing of IDS RNA (uridine to cytidine conversion and uridine deletion), and to confirm the findings previously observed ex vivo in the three patients. In addition, confocal microscopy and flow cytometry analyses demonstrated the expression and lysosomal localization in HEK293 cells of GFP-labeled proteins translated from edited IDS mRNAs. Confocal high-content analysis of the two patients’ cells expressing wild-type or mutated IDS confirmed lysosomal localization and showed no accumulation in the Golgi or early endosomes

Significance of GPR polarisation for improving target detection and characterisation

This paper focuses on the application of ground penetrating radar (GPR) technique for civil engineering purposes, addressing the issues related to wave polarisation and antennas geometry. Even if polarisation of GPR signal is often an underestimated feature during data analysis and post processing, detection or avoidance of a specific target can be managed handling its polarimetric response. This opportunity is of high importance in this field of application, where the mixture of target with different polarimetric response is a commonly encountered situation. To provide an insight of this, two multicomponent GPR surveys have been performed: a first survey to show the effect of antenna-target mutual alignment variation and a second experiment in which the benefits of acquiring with different antenna arrangements are clearly evident. Because each antenna arrangement is sensitive towards different features of the received wavefield, this strategy is able to discriminate targets depending on their geometrical shape, thus delivering better detailed image of the acquired area