• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.101-114
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• 2019

In this study, we carry out the numerical simulation to trace the yearly shoreline change of Mang-Bang beach, which is suffering from erosion problem. We obtain the basic equation (One Line Model for shoreline) for the numerical simulation by assuming that the amount of shoreline retreat or advance is balanced by the net influx of longshore and cross-shore sediment into the unit discretized shoreline segment. In doing so, the energy flux model for the longshore sediment transport rate is also evoked. For the case of cross sediment transport, the modified Bailard's model (1981) by Cho and Kim (2019) is utilized. At each time step of the numerical simulation, we adjust a closure depth according to pertinent wave conditions based on the Hallermeier's analytical model (1978) having its roots on the Shield's parameter. Numerical results show that from 2017.4.26 to 2017.10.15 during which swells are prevailing, a shoreline advances due to the sustained supply of cross-shore sediment. It is also shown that a shoreline temporarily retreats due to the erosion by the yearly highest waves sequentially occurring from mid-October to the end of October, and is followed by gradual recovery of shoreline as high waves subdue and swells prevail. It is worth mentioning that great yearly circulation of shoreline completes when a shoreline retreats due to the erosion by the higher waves occurring from mid-March to the end of March. The great yearly circulation of shoreline mentioned above can also be found in the measured locations of shoreline on 2017.4.5, 2017.9.7, 2017.11.7, 2018.3.14. However, numerically simulated amount of shoreline retreat or advance is more significant than the physically measured one, and it should be noted that these discrepancies become more substantial for the case of RUN II where a closure depth is sustained to be as in the most morphology models like the Genesis (Hanson and Kraus, 1989).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.298-317
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• 2019

The physical characteristics of the Ulleung Warm Eddy (UWE) and its relationship with the East Korea Warm Current (EKWC) were analyzed using the CMEMS (Copernicus Marine Environment Monitoring Service) satellite altimetry data and the CTD data of the National Institute of Fisheries Science (NIFS) near the Ulleung Basin from 1993 to 2017. The distribution of the UWEs coupled with EKWC accounts for 81% of the total number of the UWEs. Only 7% of the total eddies are completely separated from the EKWC. The UWE has the characteristics of high temperature and high salinity water inside of it when it is formed from the EKWC. However, when the UWE is wintering, its internal structure changes greatly. In the winter, surface homogeneous layer of $10^{\circ}C$ and 34.2 psu inside of the UWE is produced by vertical convection from sea-surface cooling, and deepened to a maximum depth of approximately 250 m in early spring. In summer, the UWE changes into a structure with a stratified structure in the upper layer within a depth of 100 m and a homogeneous layer made in winter in the lower layer. 62 UWEs were produced for 25 years from 1993 to 2017. on average, 2.5 UWEs were formed annually, and the average life span was 259 days (approximately 8.6 months). The average size of the UWEs is 98 km in the east-west direction and 109 km in the north-south direction. The average size of UWE using satellite altimetric data is estimated to be 1~25 km smaller than that using water temperature cross-sectional data.

• Journal of agriculture & life science
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• v.51 no.1
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• pp.57-67
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• 2017

We conducted this study to investigate vegetation structure and soil conditions of six Viburnum erosum Thunb.(V. erosum) populations which showed high dominance. A total of 68 woody plants were observed to distribute: 13 in tree layer; 38 in subtree layer; and 48 in shrub layer. Based on the Mean Importance Value(MIV), the dominant tree species in the V. erosum populations were as follows in order of: Acer pseudosieboldianum(Pax) Kom., Callicarpa japonica Thunb., Indigofera kirilowii Maxim. ex Palib., Lindera obtusiloba Blume, Prunus sargentii Rehder, Quercus variabilis Blume, Rhododendron mucronulatum Turcz. and Vaccinium oldhamii Miq. In paticular, the species observed in all of the study sites were Quercus serrata Murray and Styrax japonicus Siebold & Zucc. It was found that the presence of V. erosum was positively correlated with that of Albizia julibrissin Durazz. and Symplocos chinensis f. pilosa (Nakai) Ohwi, while negatively correlated with that of Platycarya strobilacea Siebold & Zucc. According to the result, means of species diversity(H'), maxim species diversity(H' max), evenness(J') and dominance(1-J') were measured at 0.887, 1.102, 0.803, and 0.196, respectively. The soil conditions properties of pH value, organic matter content, total nitrogen content, and the amount of available phosphorous indices in the study sites were 4.3, 10.6%, 0.34% and $0.68mg{\cdot}kg^{-1}$, respectively. Meanwhile, the total amount of exchangeable cations of $Ca^{2+}$, $K^+$, and $Mg^{2+}$ were $16.84cmol_c{\cdot}kg^{-1}$, $6.41cmol_c{\cdot}kg^{-1}$, and $4.26cmol_c{\cdot}kg^{-1}$, respectively. Overall, Viburnum erosum Thunb. populations tend to grow in the strongly acid soil, which has great abundance of soil organic matters, a lot of exchangeable cations, and has higher amount available phosphorous than that of nitrogen.

• Journal of Food Hygiene and Safety
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• v.36 no.3
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• pp.264-270
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• 2021

In this study we investigated the elution level of lead (Pb), cadmium (Cd), arsenic (As), zinc (Zn), nickel (Ni), antimony (Sb), germanium (Ge), aluminum (Al) and hexavalent chromium (Cr⁶⁺) from 69 home-cooking utensils into a food stimulants. The results of migration testing according to the Korea standards and specifications for utensils, containers and packages showed values the allowable migrantion limits. Al was detected in all 7 utensil materials with the average concentration ranging from 0.002-5.989 mg/L. According to the migration conditions for (180℃, 30 min), the average concentration of Al in paper was 7.2 times higher than 25℃, 10 min (P<0.05). The results of migration testing at 180℃, 30 min were also below the allowable migrantion limits. When comparing with the provisional tolerable weekly intake (PTWI) of Al, the estimated weekly intakes (EWI) accounted for 0.000-0.045% for Al.

• Economic and Environmental Geology
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• v.54 no.3
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• pp.399-408
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• 2021

Natural soil was artificially contaminated with heavy metals (Cd, Pb, and Zn), and the movement of earthworm was characterized in real time using the ViSSET system composed of vibration sensor and the other components. The manifestation mechanism of ecological toxicity of heavy metals was interpreted based on the accumulative frequency of earthworm movement obtained from the real-time monitoring as well as the conventional indices of earthworm behavior, such as the change in body weight before and after tests and biocumulative concentrations of each contaminant. The results showed the difference in the earthworm movement according to the species of heavy metal contaminants. In the case of Cd, the earthworm movement was decreased with increasing its concentration and then tended to be increased. The activity of earthworm was severely increased with increasing Pb concentration, but the movement of earthworm was gradually decreased with increasing Zn concentration. The body weight of earthworm was proved to be greatly decreased in the Zn-contaminated soil, but it was similarly decreased in Cd- and Pb-contaminated soils. The bioaccumulation factor (BAF) was higher in the sequence of Cd > Zn > Pb, and particularly the biocumulative concentration of Pb did not show a clear tendency according to the Pb concentrations in soil. It was speculated that Cd is accumulated as a metallothionein-bound form in the interior of earthworm for a long time. In particular, Cd has a bad influence on the earthworm through the critical effect at its higher concentrations. Pb was likely to reveal its ecotoxicity via skin irritation or injury of sensory organs rather than ingestion pathway. The ecotoxicity of Zn seemed to be manifested by damaging the cell membranes of digestive organs or inordinately activating metabolism. Based on the results of real-time monitoring of earthworm movement, the half maximal effective concentration (EC50) of Pb was estimated to be 751.2 mg/kg, and it was similar to previously-reported ones. The study confirmed that if the conventional indices of earthworm behavior are combined with the results of newly-proposed method, the mechanism of toxicity manifestation of heavy metal contaminants in soils is more clearly interpreted.

• Journal of Applied Biological Chemistry
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• v.64 no.4
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• pp.453-463
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• 2021

This study investigated that comparison of the nutrients (including fatty acids, amino acids, and minerals) and ginsenoside, total phenolic (TP) and total flavonoid (TF) contents and antioxidant activities in 5-year-old cultivated ginseng (CG), mountain-cultivated ginseng (MCG), and whole plant parts of MCG (WPMCG). The contents of total fatty acids and unsaturated fatty acids were determined highest in MCG (1215.9 and 751.2 mg/100 g), and saturated fatty acid was determined highest in WPMCG (486.4 mg/100 g) respectively. Characteristically, the α-linolenic acid content was detected up to 10 times higher in MCG (139.3 mg/100 g) and WPMCG (194.4 mg/100 g) compared to CG (18.1 mg/100 g). Total free and essential amino acid contents were high with CG < MCG < WPMCG (1006.35 mg/100 g and 839.46 mg/100 g). Notably, γ-aminobutyric acid and arginine were detected as the main non-essential amino acids with highest levels detected in WPMCG (163.10 mg/100 g) and MCG (305.23 mg/100 g), respectively. Total mineral content was high in CG (30.36 mg/100 g) and WPMCG (29.82 mg/100 g). Particularly, Calcium (Ca) was detected more than twice as high in WPMCG (6.68 mg/100 g) as compared to CG and MCG. TP and TF contents were 5.12 gallic acid mg/g and 3.04 RE mg/g respectively. Ginsenoside content was the highest in WPMCG (42.44 mg/g) in general and the highest antioxidant activity was also observed in WPMCG.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.19-29
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• 2022

The result of a questionnaire survey conducted on fishermen using coastal fish traps shows that fall accidents during trap dropping and pulling constitute the highest proportion of accidents at 42.1 %, whereas slipping accidents on the deck or stricture accidents to the body due to the trap winding device constitute 21.1 % each. In addition, 53.2 % of all surveyed subjects responded that trap pulling is the most dangerous task, followed by fish sorting 33.8 %, and trap dropping 9.1 %. As for the main items requested by fishermen for improving the trap winding device, 36.8 % indicated a method to easily lift the trap from the water to the work deck, and 31.6 % indicated a method to overcome the rope tension and prevent slip when pulling the trap to reduce the accidents. The small trap fishing vessel winding device proposed herein can increase the winding force by strengthening the rope contact area and friction coefficient via an appropriate contact angle between the driving roller of the winding device and the rope. When the contact angles between the driving roller and the rope are 1°, 5°, 9°, 14° and 19°, the rope tension showed a difference according to each contact angle. When the contact angle is 9°, the rope tension is the highest at 392.62 kgf. Based on these experimental results, a prototype winding device is manufactured, and 25 traps are installed on a rope with a total length of 100 m at 4 m intervals in the sea, and then the rope tension is measured during trap pulling. As a result, the rope tension increases rapidly at the initial stage of trap pulling and shows the highest value of 31.89 kgf, which subsequently decreases significantly. Therefore, it is appropriate to design the winding force of a small trap fishing vessel winding device based on the maximum tension value of the rope specified at the beginning of the trap pulling operation.

• Journal of Korean Society of Forest Science
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• v.111 no.3
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• pp.405-417
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• 2022

The purpose of this study was to describe the photosynthetic features of Prunus maximowiczii and Prunus serrulate Lindl. var. pubescens (Makino) Nakai in response to drought stress. Specifically, we studied the effects of drought on photosynthetic ability and photosystem II activity. Drought stress (DS) was induced by cutting the water supply for 30 days. DS decreased the moisture contents in the soil, and between the 10th and 12th days of DS, both species had 10% or less of x., After the 15th day of DS, it was less than 5%, which is a condition for disease to start. We observed a remarkable decrease of maximum photosynthesis rate starting from 10th day of DS; the light compensation point was also remarkable. Dark respiration and net apparent quantum yield decreased significantly on the 15th day of DS, and then increased on the 20th day. In addition, the stomatal transpiration rate of P. maximowiczii decreased significantly on the15th day of DS, and then increased on the 20th day. Water use efficiency increased on the 15th day of DS, and then decreased on the 20th day. The stomatal transpiration rate of P. serrulate decreased significantly on the 20th day of DS, and then increased afterward, while its water use efficiency increased on the 20th day of DS, and then decreased afterward. These results indicate that the closure of stoma prevented water loss, resulting in a temporary increase of water use efficiency. Chlorophyll fluorescence analysis detected remarkable decreases in the functional index (PI_ABS) and energy transfer efficiency in P. maximowiczii after the 15th day of DS. Meanwhile, photosystem II activity decreased in P. serrulate after 20 days of DS. In addition, Ts-Ta, PI_ABS, DI_O/RC, ET_O/RC followed similar trends as those of the soil moisture content and photosynthetic properties, indicating that they can be used as useful variables in predicting DS in trees.

• Journal of Food Hygiene and Safety
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• v.37 no.4
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• pp.249-259
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• 2022

This study investigated pesticide residues in 7,069 agricultural products distributed in the city of Incheon from 2019 to 2021. Ingestion of pesticides can cause serious carcinogenic, endocrine, neurological, and reproductive problems. Pesticide residues in the samples were analyzed using various multi-residue methods (GC-MS/MS, GC-ECD/NPD, LC-MS/MS, and HPLC-UVD) on the Korean Food Code. The violation rate of the samples exceeding the maximum residue level (MRL) of pesticide residues for the years 2019, 2020, and 2021 was 1.0%, 1.4%, and 1.1%, respectively. Diazinon, flubendiamide, procymidone, fluxametamide, and fluquinconazole were the most frequently reported violative pesticide residues. Most commonly encountered agricultural products exceeding MRLs were coriander leaves, chamnamul, chwinamul, welsh onion, and crown daisy. Agricultural products and pesticides frequently exceeding MRLs should be continuously inspected for food safety. Continuous monitoring of pesticide residues in agricultural products is indispensable to improve consumer safety by preventing the distribution of agricultural products exceeding MRLs.

• Korean Journal of Ecology and Environment
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• v.55 no.2
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• pp.120-131
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• 2022

Microcystins (MCs) are cyano-toxins mainly produced by cyanobacteria in the genera of Microcystis, Anabaena, and Oscillatoria. The concentrations of MCs in the water bodies and fish tissues taken from the four weirs (Ipo, Gangjeong-goryeong, Baekje, and Juksan) in the four main rivers in Korea, and the health risk of human due to consumption of toxin-detected fish was examined. The maximum values of MCs concentration in the water samples were as follows: Juksan (3.261 ㎍ L^-1), Gangjeong-goryeong (1.014 ㎍ L^-1), Baekje (0.759 ㎍ L^-1), and Ipo (0.266 ㎍ L^-1) weirs. The MC-RR concentration was the highest among the MCs, and MC-YR was not detected. MCs of 0.222~9.808 ㎍ g^-1 dry weight were detected in the liver of 3 out of 215 fishes of 16 species, and below the detection limit in muscle. As a result of comparing the feeding characteristics of the collected fishes and toxin concentrations in water and fish tissue, it was concluded that the biomagnification of MCs through the food chain did not occur. It was judged that there was no health risk due to the consumption of the fish detected the toxin, based on the amount of the fish intake of the Korean people and the allowable daily intake of MCs. However, in order to reduce the health risk due to MCs, further studies should be conducted to analyze the concentration of MCs contained in fish tissues collected at various times in the area dominated by harmful cyanobacteria to obtain data on the exposure of MCs due to fish consumption. In addition, it is necessary to establish the management guidelines for MCs in fish tissues.