• Journal of the Korean GEO-environmental Society
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• v.19 no.3
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• pp.15-24
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• 2018

As electromagnetic waves are affected by electrical conductivity or permittivity, they are widely used to evaluate geotechnical characteristics. In this study, a probe for measuring electromagnetic waves using a time domain reflectometry is manufactured to evaluate heavy metal concentration in saline water. In the experiments, a copper is used as a heavy metal, and a probe is demonstrated with the concentration of copper. Solutions were set for 8 different copper concentration (0, 0.01, 0.05, 0.1, 0.5, 1, 5, 10 mg/L) in saline water with 3% salinity. The probe is coated by electrical insulating materials such as epoxy, top-coat, varnish, acrylic paint, heat-shrinkage tube to measure electromagnetic waves in saline water. The measured signals are compared according to coating material. As results, for probes coated with acrylic paint and heat-shrinkage tube, signal variation is not detected. For epoxy, top-coat, and varnish coated probes, the voltage decreases with an increase of copper concentration. Probes coated by epoxy at once and top coat can estimate under 5 mg/L of copper concentration and the probe coated by epoxy twice can estimate over 5 mg/L of copper concentration. This study shows that the probe using the time domain reflectometry can be used to evaluate the concentration of heavy metal in saline water by coating the probe with insulating material.

• Composites Research
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• v.36 no.6
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• pp.429-434
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• 2023

In this study, aimed at improving the existing acoustic emission sensor for real time monitoring, a macro-fiber composite (MFC) transducer was employed as the acoustic emission sensor in the gas leak detection system. Prior to implementation, structural analysis was conducted to optimize the MFC's design. Consequently, the flexibility of the MFC facilitated excellent adherence to curved pipes, enabling the reception of acoustic emission (AE) signals without complications. Analysis of AE signals revealed substantial variations in parameter values for both high-pressure and low-pressure leaks. Notably, in the parameters of the Fast Fourier Transform (FFT) graph, the change amounted to 120% to 626% for high-pressure leaks compared to the case without leaks, and approximately 9% to 22% for low-pressure leaks. Furthermore, depending on the distance from the leak site, the magnitude of change in parameters tended to decrease as the distance increased. As the results, in the future, not only will it be possible to detect a leak by detecting the amount of parameter change in the future, but it will also be possible to identify the location of the leak from the amount of change.