• 한국지하수토양환경학회지:지하수토양환경
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• 제16권1호
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• pp.19-31
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• 2011

This study had been carried out to investigate spatial and temporal variations of the concentrations of trace metals for contaminated surface water in creek affected by leachate from the tailings impoundment of the Yeonhwa II mine for about 2 years. It was also to ascertain the metal removal efficiency for potentially deleterious metals by the artificial and natural attenuation processes such as retention ponds and hydrologic mixing of uncontaminated tributaries. The concentrations of As, Pb, Cd, and Cu for leachate in the rainy season were not detected. On the other hand, the concentrations of Zn, Fe, Mn, Al, and $SO_4^{2-}$ in the rainy season for leachate were 2-66 times higher than those in the dry season, due to the oxidation of the sulfide minerals and the dissolution of the secondary minerals. The concentrations of Zn and Cd for leachate and surface water of the upper creek in the rainy season exceeded the criteria of River Water Quality and Drinking Water Quality but in the dry season, those of analyzed all the metals (As, Pb, Cd, Cu, Zn, Cd, Fe, Mn, and Al) for surface water sampled at the study area were below the criteria of River Water Quality and Drinking Water Quality. In regard of the attenuation efficiency for the concentrations of metals, Fe, Mn, Al, Zn, Cd, As, and Cu were removed highly at retention ponds, while the removal efficiency for major cations and sulfate ($SO_4^{2-}$) were related to mixing of the uncontaminated tributaries. Therefore, the major attenuation processes of the metal and sulfate contents in creek affected by leachate from a tailing dump were precipitation (accompanied by metal co-precipitation and sorption), water dilution, and neutralization.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1634-1641
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• 2021

Exposure to gamma-rays is hazardous for humans and other living beings because of their high penetration through the materials. For this reason, shielding materials (usually lead, copper and stainless steel) are used to protect against gamma rays. This study's objective was to prepare ceramic materials for gamma radiation shielding by using different natural bentonite clays. Gamma-ray attenuation performances of the prepared shielding materials at different thicknesses were investigated and evaluated for different gamma-ray energies from different standard point gamma radiation sources (²⁵¹Am, ⁵⁷Co, ¹³⁷Cs, ⁶⁰Co, and ⁸⁸Y). The mass and linear attenuation coefficients of the prepared ceramics vary between 0.238 and 0.443 cm² g^-1 and between 0.479 and 1.06 cm^-1, respectively, depending on their thicknesses. Results showed that these materials could be prioritized because of their evidential properties of gamma radiation protection in radiation applications.

• Journal of Multimedia Information System
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• 제6권3호
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• pp.155-164
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• 2019

We intended to confirm that microwave attenuation by tree leaves is strongly linked to water content in leaves. We sampled natural broadleaves, including Japanese cinnamon, and investigated their effects on the microwave (3 to 20 GHz) frequency characteristics using a network analyzer. Experiments determined that microwave attenuation by foliage increases as a linear function of frequency per unit weight (gram). As the frequency increases, the spatial resolution increases, but the phase difference (imaginary component) increases. So we solved the dispersion of phase difference by sweeping the frequency and taking the intermediate value. Based on these experimental results, we developed a microwave scanner on 10Ghz to describe foliage moisture as a image and to enable assessments of leaf condition. Photosynthesis is the process whereby plants synthesize oxygen and sugars from carbon dioxide and water, thereby converting light energy into chemical energy. Since water is a major parameter of photosynthesis, the quantity of water accumulated inside a leaf reflects leaf health. The equipment described here and related microwave technologies will help assess the capacity of leaves to absorb atmospheric carbon dioxide.

• Structural Monitoring and Maintenance
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• 제9권4호
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• pp.373-388
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• 2022

A USW based diagnostic procedure is presented for estimating the depth of surface-breaking cracks. The diagnosis is demonstrated on seven lab-scale SFRC beam specimens, which are subjected to the CMOD controlled three-point bending test to create real bending cracks. Then, the recorded multiple ultrasonic signals are examined with the signal processing techniques, including wavelet transform and two-dimensional Fourier transform, to investigate the relationships between the crack depth and two diagnostic indices, namely the attenuation coefficient and dispersion index (DI). Finally, the reliabilities of these indices for depth estimation are verified with the visually measured crack depths as well as the crack features obtained with a digital image processing algorithm. It is found that the DI outperforms the attenuation coefficient in depth estimation, where this index displays good agreement with the visual inspection for 86% of the inspected specimens.

• 한국지하수토양환경학회지:지하수토양환경
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• 제6권1호
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• pp.85-88
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• 2001

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2001년도 정기총회 및 제3회 특별지포지움
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• pp.34-56
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• 2001

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1476-1484
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• 2023

Laboratory experiments and point monitoring of reservoir sediments have proven that stable sulfate reduction (SSR) can lower the concentrations of toxic metals and sulfate in acidic groundwater for a long time. Here, we hypothesize that SSR occurred during in situ leaching after uranium mining, which can impact the fate of acid groundwater in an entire region. To test this, we applied a sulfur isotope fractionation method to analyze the mechanism for natural attenuation of contaminated groundwater produced by acid in situ leaching of uranium (Xinjiang, China). The results showed that δ³⁴S increased over time after the cessation of uranium mining, and natural attenuation caused considerable, area-scale immobilization of sulfur corresponding to retention levels of 5.3%-48.3% while simultaneously decreasing the concentration of uranium. Isotopic evidence for SSR in the area, together with evidence for changes of pollutant concentrations, suggest that area-scale SSR is most likely also important at other acid mining sites for uranium, where retention of acid groundwater may be strengthened through natural attenuation. To recapitulate, the sulfur isotope fractionation method constitutes a relatively accurate tool for quantification of spatiotemporal trends for groundwater during migration and transformation resulting from acid in situ leaching of uranium in northern China.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.944-949
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• 2018

The mass attenuation coefficients (${\mu}/{\rho}$) of food waste samples (pomegranate peel, acorn cap, lemon peel, mandarin peel, pumpkin peel, grape peel, orange peel, pineapple peel, acorn peel and grape stalk) have been measured employing a Si(Li) detector at 13.92, 17.75, 20.78, 26.34 and 59.54 keV. Also, the theoretical values of the mass attenuation coefficients have been evaluated utilizing mixture rule from WinXCOM program. The results showed that the lemon peel has the highest values of ${\mu}/{\rho}$ among the selected samples. From the obtained mass attenuation coefficients, we determined some absorption parameters such as effective atomic number ($Z_{eff}$), electron density ($N_E$) and molar extinction coefficient (${\varepsilon}$). It was found that the $Z_{eff}$ values of all food wastes lie within the range of 4.034-7.595, whereas the $N_E$ of the studied food wastes was found to be in the range of $0.301-1.720{\times}10^{25}$ (electrons/g) for present energy region.

• 한국지하수토양환경학회지:지하수토양환경
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• 제27권spc호
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• pp.92-98
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• 2022

Although various methods have been proposed to assess groundwater vulnerability, most of the models merely consider the mobility of contaminants (i.e., intrinsic vulnerability), and the attenuation capacity of vadose zone is often neglected. This study proposed an evaluation model for the attenuation capacity of vadose zone to supplement the limitations of the existing index method models for assessing groundwater vulnerability. The evaluation equation for quantifying the attenuation capacity was developed from the combined linear regression and weighted scaling methods based on the lab-scale experiments using various vadose zone soils having different physical and biogeochemical properties. The proposed semi-quantifying model is expected to effectively assess the attenuation capacity of vadose zone by identifying the main influencing factors as input parameters together with proper weights derived from the coefficients of the regression results. The subsequent scoring and grading system has great versatility while securing the objectivity by effectively incorporating the experimental results.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.2025-2037
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• 2021

The influence of lead cations on natural quartz (QZ) from Egypt as a glass shielding material for the composition with nominal formula (10Na₂O - (90 - x) QZ - xPbO (where x = 30, 35, 40, 45 and 50 mol %)) was examined. The studied samples are synthesized via the melt quenching method at 1050 ℃. The X-ray diffraction XRD patterns were confirmed the glass nature for studied samples. Moreover, the optical properties, and the transparency for all compositions were examined by UV-Vis spectroscopy. Also, the major elemental composition of the natural quartz were estimated via the X-ray fluorescence (XRF) technique. Further, the density and molar volume were determined. Furthermore, the nuclear shielding parameters such as, mass attenuation coefficient, effective atomic number, electronic density, the total atomic, and electronic cross sections as well as the mean free path, and the half value layer with different gamma ray energies (81 keV-1407 keV) were calculated. Besides, the results showed that the shielding behavior towards the gamma ray radiation for all glass samples was increased as the increment in PbO concentration in the glass system.