• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.136-142
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• 2022

The crystal structure, grain growth behavior, and dielectric properties of BaTiO₃ have been studied with the addition of Dy₂O₃. The powders were synthesized at ratios of (100-x)BaTiO₃-xDy₂O₃ (mol%, x = 0, 0.5, 1.0, 2.0) by a conventional solid-state synthesis, and the powder compacts were sintered at 1250℃ for 2 hours in air. As the amount of added Dy₂O₃ was increased, the crystal structure of the sintered samples changed from a tetragonal to a pseudo-cubic structure, and the tetragonality decreased. In addition, a secondary phase of Ba₁₂Dy_4.67Ti₈O₃₅ appeared when Dy₂O₃ was added. The average grain size after sintering decreased and abnormal grains appeared as the amount of Dy₂O₃ increased. It can be explained that the grain growth behavior of the Dy₂O₃ added-BaTiO₃ occurs due to the two-dimensional nucleation and growth, and is governed by the interface reaction. Further, the correlation between crystal structure, microstructure, and dielectric properties was discussed.

• Journal of Practical Agriculture & Fisheries Research
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• v.9 no.1
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• pp.33-46
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• 2007

We conducted this research to develop the medium for some edible mushroom cultivation using shiitake waste log which is abandoned after cultivation of shiitake mushroom because those bed logs can not be recycled. The isolates of P. ostreatus(POS-012), P. eryngii(PER-005), G. frondosa(GFR-001) and F. velutipes(FVE-001) were selected and examined for mycelial growth on sawdust media prepared from shiitake waste log. Mycelial growth of selected isolate were satisfactory on the sawdust extract media using acasia(Robinia pseudo-acacia), neutinamu(Zelkova serrata) and kangchamnamu(sangsuri, Quercus acutissima) which are no shiitake-inoculated. Although the mycelial growth of the isolate were poor on the sawdust media prepared from Quercus spp., sawdust of neutinamu, (Zelkova serrata), beotnamu, (Prunus serrulata), orinamu(Alnus japonica), eunsuweonsasinamu(Populus tomentiglandulosa) and chestnut(Castanea crenata) were excellent for mycelial growth. However, shiitake logs which are infected with harmful fungi such as Hypocrea spp. were useful as recycle materials for mushroom cultivation.

• (The) Research of the performance art and culture
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• no.42
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• pp.321-359
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• 2021

This paper examines the unique features of Korean farmer's music-or nongak-in Hawaii by exploring three nongak groups from different decades beginning in the 1970s. The first community-based nongak group began in the 1970s, with the establishment of the Wahiawa Korean Seniors Club. In the 1980s, there was another group supported by the Kalihi-Palama Immigrant Service Center. And in the 1990s, the Hawaii Korean Farmer's Music Assoiation, which is still active, was founded. I ullustrate the overall changes made by the three nongak groups as follows. First, they show a shift from social groups playing music to a music group doing social activities. Second, from a group of people negotiating their music, through a group led by musical leadership, to a group with a leader who created his own musical leadership. Third, from a music group began out of a pseudo-shaman ritual, through a group purely playing music, to a group adding samulnori and further creating a new rhythmic pattern. These changes occurred because, while the members are all first-generation immigrants, their experience of nongak in the motherland was different because of their age differences. In addition, they emerged because the level of awareness and acceptance of samulnori-which has gained huge popularity in Korea-were different.

• Clean Technology
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• v.15 no.3
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• pp.194-201
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• 2009

Reductive reactivity of zero-valent iron nanoparticles was investigated for removal of nitrate-nitrogen which is considered one of the major water pollutants. To elucidate the difference in reactivity between preparation methods, iron nanoparticles were synthesized respectively from microemulsion and aqueous solution of ferric ions. Iron nanoparticles prepared from microemulsion were deposited on aluminum by electrophoretic method, and their reaction kinetics was compared to that of the same nanoparticles suspended in aqueous batch reaction. With an approximation of pseudo-first-order reaction, rate constants for suspended nanoparticles prepared from microemulsion and dilute aqueous solution were $3.49{\times}10^{-2}min^{-1}$ and $1.40{\times}10^{-2}min^{-1}$, respectively. Iron nanoparticles supported on aluminum showed ca. 30% less reaction rate in comparison with the identical nanoparticles in suspended state. However, supported nanoparticles showed the superior effectiveness in terms of nitrate-nitrogen removal per zero-valent iron input especially when excess amounts of nitrates were present. Iron nanoparticles deposited on aluminum maintained reductive reactivity for more than 3 hours, and produced nitrogen gas as a final reduction product of nitrate-nitrogen.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.57-70
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• 2010

Recent earthquakes have demonstrated that the tunnels, which were once considered to be highly resistant to earthquakes, are susceptible to substantial damage under severe seismic loading. Among various modes of deformation under an earthquake loading, the response of the tunnel in the transverse direction is known to be the critical mode. This paper investigates the seismic response of the tunnel in the transverse direction using the method of seismic displacement, which is a type of pseudo-static analysis. Firstly, the methods of calculating the ground deformation are compared. It is shown that the single and double cosine may not provide an accurate estimation of the ground deformation, and that a one-dimensional site response analysis needs to be performed for a more reliable evaluation. Secondly, the tunnel responses are calculated using the simplified, analytical, and numerical solutions. It is demonstrated that the simplified method provides poor estimates of the tunnel response ground deformation. The analytical solution is shown to be effective in modeling circular tunnels in uniform ground, but has serious limitation in modeling tunnel response in non-uniform ground. Numerical analyses are shown to be applicable to all cases, and give the most accurate estimates of the tunnel response. It is also demonstrated that the linear solutions can be so conservative that the soil nonlinearity needs to be accounted for more accurate evaluation of the tunnel response.

• The Korean Journal of Mycology
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• v.51 no.1
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• pp.39-49
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• 2023

This study aimed to screen and investigate the microbiological characteristics, enzyme activity, and physiological functionality of unrecorded wild yeasts from the Wolsung valley of South Deogyu mountain and Jinjamcheon in Daejeon city, Korea. Candida sorboxylosa WSC25-4 (NNIBRFG47336), Arxula adeninivorans WSC6-3 (NNIBRFG47335), Farysizyma taiwaniana JRC6-2 (NNIBRFG47339), Saturnispora dispora JTS19-1 (NNIBRFG47334), Vanderwaltozyma polyspora JJCH5-3 (NNIBRFG47337), and Vanrija fragicola SW-9 (NNIBRFG47338) have not been previously recorded. None of these formed spores or pseudo-mycelium, and four strains, including C. sorboxylosa WSC25-4, were global in shaped. Except for V. polyspora JJCH5-3, all strains grew well in the yeast extract-peptone-dextrose (YPD), potato-dextrose and yeast malt extract media. A. adeninivorans WSC6-3 and S. dispora JTS19-1 grew well in 40% glucose-containing YPD medium and V. fragicola SW-9 in 5% NaCl-containing YPD medium. The supernatant of A. adeninivorans WSC6-3, F. taiwaniana JRC6-2, and V. fragicola SW-9 exhibited 58.0, 59.0, and 59.0% of glucoamylase activity, respectively. C. sorboxylosa WSC25-4 also produced extracellular alkaline protease. Antioxidant activity of the supernatant from F. taiwanian JRC6-2 was high (79.8%), while the other five unrecorded yeasts demonstrated elevated antiaging superoxide dismutase (SOD)-like activity (99%). Anti-gout xanthin oxidase inhibitory activity of S. dispora JTS19-1 and V. fragicola SW-9 was also elevated at 79 and 80%, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.3
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• pp.321-335
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• 2023

Monitoring sediment loads in natural rivers is the key process in river engineering, but it is costly and dangerous. In practice, suspended loads are directly measured, and total loads, which is a summation of suspended loads and bed loads, are estimated. This study proposes a real-time sediment discharge monitoring system using the horizontal acoustic Doppler current profiler (H-ADCP) and support vector regression (SVR). The proposed system is comprised of the SVR model for suspended sediment concentration (SVR-SSC) and for total loads (SVR-Q_TL), respectively. SVR-SSC estimates SSC and SVR-Q_TL mimics the modified Einstein procedure. The grid search with K-fold cross validation (Grid-CV) and the recursive feature elimination (RFE) were employed to determine SVR's hyperparameters and input variables. The two SVR models showed reasonable cross-validation scores (R²) with 0.885 (SVR-SSC) and 0.860 (SVR-Q_TL). During the time-series sediment load monitoring period, we successfully detected various sediment transport phenomena in natural streams, such as hysteresis loops and sensitive sediment fluctuations. The newly proposed sediment monitoring system depends only on the gauged features by H-ADCP without additional assumptions in hydraulic variables (e.g., friction slope and suspended sediment size distribution). This method can be applied to any ADCP-installed discharge monitoring station economically and is expected to enhance temporal resolution in sediment monitoring.

• Korea Trade Review
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• v.43 no.5
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• pp.25-45
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• 2018

This paper estimates the export losses of the Korean domestic automobile industry due to US trade pressure and its economic ripple effects. Using the HS 6 digit tariff and export data from 2010 to 2017, this paper estimates the tariff elasticity of Korea's US automobile exports against a US tariff increase by applying the Poisson Pseudo maximum likelihood estimation method. After estimating Korea's export losses to the US in three trade pressure scenarios, we estimate its impact on Korean domestic production, value-added and job creation by applying the tariff impact accumulation model based on the industry input-output analysis. Empirical results show that the impact of 25% global tariff by the US on the Korean domestic economy is estimated to result in $30.8 billion in export losses for the five years from 2019 to 2023, about 300 thousand job losses, 88.0 trillion in production inducement losses, and 24.0 trillion in value-added inducement losses. The impacts of withdrawal of the automobile tariff concession are estimated at $4.27 billion export losses and 41.7 thousand job losses. A 15% tariff rate on automobile parts for 3 years is estimated to result in $1.93 billion export losses and 18.7 thousand job losses.

• Journal of the Korea Society of Computer and Information
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• v.28 no.10
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• pp.133-153
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• 2023

In this paper, we propose a novel approach to investigating brain-signal measurement technology using Electroencephalography (EEG). Traditionally, researchers have combined EEG signals with bio-signals (BSs) to enhance the classification performance of emotional states. Our objective was to explore the synergistic effects of coupling EEG and BSs, and determine whether the combination of EEG+BS improves the classification accuracy of emotional states compared to using EEG alone or combining EEG with pseudo-random signals (PS) generated arbitrarily by random generators. Employing four feature extraction methods, we examined four combinations: EEG alone, EG+BS, EEG+BS+PS, and EEG+PS, utilizing data from two widely-used open datasets. Emotional states (task versus rest states) were classified using Support Vector Machine (SVM) and Long Short-Term Memory (LSTM) classifiers. Our results revealed that when using the highest accuracy SVM-FFT, the average error rates of EEG+BS were 4.7% and 6.5% higher than those of EEG+PS and EEG alone, respectively. We also conducted a thorough analysis of EEG+BS by combining numerous PSs. The error rate of EEG+BS+PS displayed a V-shaped curve, initially decreasing due to the deep double descent phenomenon, followed by an increase attributed to the curse of dimensionality. Consequently, our findings suggest that the combination of EEG+BS may not always yield promising classification performance.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.404-411
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• 2022

The main function in operating the satellite navigation system is to accurately determine the orbit of the navigation satellite and transmit it as a navigation message. In this study, we developed software to determine the orbit of a navigation satellite by combining an extended Kalman filter and an accurate dynamic model. Global positioning system (GPS) and quasi-zenith satellite system (QZSS) orbit determination was performed using international gnss system (IGS) ground station observations and user range error (URE), a key performance indicator of the navigation system, was calculated by comparison with IGS precise ephemeris. When estimating the clock error mounted on the navigation satellite, the radial orbital error and the clock error have a high inverse correlation, which cancel each other out, and the standard deviations of the URE of GPS and QZSS are small namely 1.99 m and 3.47 m, respectively. Instead of estimating the clock error of the navigation satellite, the orbit was determined by replacing the clock error of the navigation message with a modeled value, and the regional correlation with URE and the effect of the ground station arrangement were analyzed.