On the introduction of canny operator in an advanced imaging algorithm for real-time detection of hyperbolas in ground-penetrating radar data

This paper focuses on the use of the Canny edge detector as the first step of an advanced imaging algorithm for automated detection of hyperbolic reflections in ground-penetrating radar (GPR) data. Since the imaging algorithm aims to work in real time; particular attention is paid to its computational efficiency. Various alternative criteria are designed and examined, to fasten the procedure by eliminating unnecessary edge pixels from Canny-processed data, before such data go through the subsequent steps of the detection algorithm. The effectiveness and reliability of the proposed methodology are tested on a wide set of synthetic and experimental radargrams with promising results. The finite-difference time-domain simulator gprMax is used to generate synthetic radargrams for the tests, while the real radargrams come from GPR surveys carried out by the authors in urban areas. The imaging algorithm is implemented in MATLAB

Gamma Irradiation Effects in Optical Fibres, Splitters, and Connectors

The paper presents a brief overview of contemporary ELION techniques with stress on their use for material modification and dosimetry. In the attempt to avoid some common misjudges of irradiation effects, special attention is paid to exact definition of irradiation geometry and careful adjustment of dose rates, which enable a proper elaboration of experimental results. In particular, effects of gamma-rays irradiation on properties of commercial optical fibres, splitters, connectors, and fibre joints are examined, which enables monitoring of irradiation effects in complex configurations made of materials with different radiation hardness (resistance). It has been established that gamma-rays irradiation of the investigated elements influences, in different ways, the transmission of laser beam signals of various wavelengths, under different modulation regimes. After irradiation, the signal attenuation is noticeably larger, both in optical connectors and optical splitter, than before it, and the effect increases in time. The effects are more pronounced at the 99 % than at the 1 % Y-splitter output at both measured wavelengths, and are more pronounced at 1310 nm than at 1550 nm

Interaction of laser beams with carbon textile materials

Purpose - The purpose of this paper is to present the results of interaction occurring during the exposition of some specific carbon textile materials obtained in laboratory conditions to beams of various laser types. Design/methodology/approach - Carbon fabric materials - fiber, felt and cloth - obtained from different precursor materials and prepared at various process conditions (oxidized, partially carbonized, carbonized, graphitized), were exposed to pulses of various lasers (Nd3+:YAG, alexandrite, ruby). Findings - Depending on the laser power, plasma and destructive phenomena occurred. In the case of an interaction between a Nd3+: YAG laser beam and specimens of thickness in millimeter range, the authors have estimated the threshold of the energy density for drilling and discussed the possible models of the interaction. Research limitations/implications - The results have implications in the estimations of quality as well as in the improvement of material processing, giving some new light to the changes of mechanical and optical constants of the material, as well as to the changes of carbon groups of the material, which would be useful for different types of modeling. Future research will be in the interaction of laser beams with various textile materials, where the investigation would cover the microstructure changes and the implications on cloth cutting and welding, concerning the damages as well as relief structures, specially renew for fs laser regimes. Originality/value - The area of laser applications in the textile industry is supported by scientific and applicative exploration. However, fewer results are concerned with deep introspection into the microstructure of the damages considering the laser interaction with carbon fiber and other carbon-based textiles

Automated data extraction from synthetic and real radargrams of complex structures

This paper presents a comparative study of two algorithms for detecting and analyzing the characteristic shapes of reflection obtained as a result of Ground-Penetrating Radar (GPR) scanning technology. The first algorithm is a sub-array processing method that uses direction-of arrival algorithms and the matched filter technique; this approach is implemented in SPOT-GPR (release 1.0), a new freeware tool for the detection and localization of targets in radargrams. The second algorithm, APEX, is based on machine learning and pattern recognition techniques and it allows finding the coordinates of apexes and further characteristic points of hyperbolas in radargrams. Both software solutions are implemented in MATLAB environment. As a first step, we compare the accuracy of our algorithms when applied to synthetic data, calculated by using the open-source finite-difference time-domain simulator gprMax; the scenarios are two concrete cells hosting different metallic and dielectric targets. Then, we compare the accuracy of our algorithms when applied to experimental data, recorded over district heating pipes in a trench, with known geometry and depth of the pipes. For the latter scenario, we have also generated a gprMax radargram, matching the geometry and scanning settings of the real one; both algorithms are tested on this synthetic radargram, as well. Overall, both algorithms perform well and rather uniformly in localizing the targets. The accuracy of the algorithms is at centimeter level, which is sufficient in most applications