• Korean Journal of Remote Sensing
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• v.36 no.2_2
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• pp.309-323
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• 2020

Estimation of chlorophyll a concentration (CHL) on coastal areas using remote sensing has been mostly performed through multi-spectral satellite image analysis. Recently, various studies using hyperspectral imagery have been attempted. In particular, airborne hyperspectral imagery is composed of hundreds of bands with a narrow band width and high spatial resolution, and thus may be more effective in coastal areas than estimation of CHL through conventional satellite image. In this study, comparative analysis of hyperspectral and satellite-based CHL images was performed to estimate CHL in coastal areas. As a result of analyzing CHL and seawater spectrum data obtained by field survey conducted on the south coast of Korea, the seawater spectrum with high CHL peaked near the wavelength bands of 570 and 680 nm. Using this spectral feature, a new band ratio of 570 / 490 nm for estimating CHL was proposed. Through regression analysis between band ratio and the measured CHL were generated new CHL empirical formula. Validation of new empirical formula using the measured CHL showed valid results, with R² of 0.70, RMSE of 2.43 mg m^-3, and mean bias of 3.46 mg m^-3. As a result of applying the new empirical formula to hyperspectral and satellite images, the average RMSE between hyperspectral imagery and the measured CHL was 0.12 mg m^-3, making it possible to estimate CHL with higher accuracy than multi-spectral satellite images. Through these results, it is expected that it is possible to provide more accurate and precise spatial distribution information of CHL in coastal areas by utilizing hyperspectral imagery.

• Journal of Practical Agriculture & Fisheries Research
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• v.14 no.1
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• pp.107-115
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• 2012

In juvenile size, the maximum clearance rate and ingestion rate were 15mm, which is the 70.8 mL/h, 4245.0×104cells/h, respectively. But the lowest clearance rate and ingestion rate were found at 5mm, which is the 4.1 mL/h, 246.0×104cells/h, respectively. The highest clearance rate and ingestion rate of AFDW seen at 7.5mm, with 3.3 mL/mg AFDW/h, 196.0×104cells/mg AFDW/h, respectively. According to the results of water temperature, clearance rate and ingestion rate were lowest at 10℃, showing the 0.3 mL/h, 20.3×104cells/h, respectively. The highest clearance rate and ingestion rate were 25℃, which is the 16.6 mL/h, 993.4×104cells/h, respectively. But in 30℃, clearance rate and ingestion rate decreased to the 12.9 mL/h, 772.6×104cells/h, respectively. With respect to the food density, the experiment groups with 30×104 cells/mL and 240×104 cells/mL showed the clearance rate of 21.1 mL/h and 2.3 mL/h, respectively. But the experimental group with 120×104 cells/mL or more showed decreased clearance rate. While, the maximum ingestion rate was at 60×104 cells/m, showing the 876.2×104cells/h.

• The Korean Journal of Ecology
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• v.26 no.1
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• pp.13-18
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• 2003

We examined water flux, concentrations and contents in nutrients in precipitation, throughfall, stemflow and soil solution in natural deciduous hardwood forest(Quercus variabilis and Q. mongolica) in Chunchon, Kangwon Province. The volume of throughfall was 2∼3% higher in Q. variabilis than in Q. monglica while volume of stemflow, Ao, A and B soil solution was 10∼15% higher in Q. variabilis compared to Q. monglica. Concentrations of K/sup +/ increased in throughfall H while concentrations of Ca/sup 2+/, Mg/sup 2+/ and NO₃/sup -/ increased in Ao soil solution. The former might be related to the canopy leaching and the latter related to leaching and nitrification in Ao horizon. Nutrient concentrations in throughfall, Ao, A and B soil solution decreased with increasing amount of water and especially the decreases in concentrations of K/sup +/, Mg/sup 2+/ and Cl/sup -/ were significant. Nutrient concentrations of Ca/sup 2+/ in Ao soil solution was 1.5 times higher in Q. variabilis than in Q. mongolica. However, there were no significant nutrient concentration differences in throughfall, stemflow and A and B soil solution between the two forest types. Stemflow was less than 10% of total water volume (throughfall + stemflow) to the forest floor, and contribution of stemflow to nutrient cycling seemed to be low in the study forest.

• Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.171-179
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• 2021

To better understand the ecological functioning of the coastal ecosystem in Gamak Bay on the southern coast of Korea, seasonal changes in the density, biomass, and secondary production of the copepod community were investigated. Environmental measurements (temperature, salinity, and chlorophyll a) and copepod sampling were performed seasonally from January to December 2006. The mean density of copepods (excluding nauplii) varied from 949 to 5,999 ind · m^-3; copepod density was at its highest from March to July. The copepod community comprised 32 taxa, including Calanoida, Cyclopoida, and Harpacticoida. The predominant species were Paracalanus parvus s. l., Acartia omorii, Eurytemora pacifica, Oithona similis, A. erythraea, Centropages abdominalis, Pseudodiaptomus marinus, and Calanus sinicus. There were significant spatial and seasonal variations in copepod total biomass, which ranged from 0.33 to 43.10 mg C m^-3. Mean secondary production of the copepods in Gamak Bay, estimated as 2.05 ± 1.63 mg C m^-3 d^-1 using the Huntley and Lopez growth model, was over 2 times higher than the value given by application of the Hirst and Bunker model (1.09 ± 0.85 mg C m^-3 d^-1). The daily production rate to biomass (P/B) ratio varied between 0.08 and 0.86 d^-1 (Huntley and Lopez model), and 0.18 and 0.33 d^-1 (Hirst and Bunker model). Our results emphasize the ecological significance of using models to estimate the secondary production of copepods and provides the first report of copepod production in Gamak Bay.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.3
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• pp.172-179
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• 2022

Sweet potato varieties with high fiber content in the storage root have poor texture when steamed or roasted. This study investigates the difference in fiber content among sweet potato varieties by soil and climate. The average fiber content of 'Hogammi', 'Sodammi', 'Pungwonmi', 'Danjami', and 'Jinyulmi' cultivars from the samples collected at farms in Haenam, Muan, and Unbong, Korea were 95.71, 66.73, 44.55, 40.55, and 38.53 mg/100g FW, respectively. There was no significant difference between site-specific conditions and varieties. Based on the degree of visual fibrousness, 'Hogammi' has an average of 3.6-4.0 with many thick stringy fibers. The fiber content of the 'Hogammi' cultivar was measured across 19 sites representing the main sweet potato growing regions of Korea. The fiber content was between 115.82 and 114.6 mg/100g in Haenam 2 and Boryeong 1, and 87.46 mg/100g in Hamyang. However, the fiber content at the remaining 16 sites was within the range of 94.63-108.52 mg/100g, although there were some site-level differences. The fiber content of the sweet potato storage roots were positively correlated with soil phosphorus (R² = 0.58^**), organic matter (R² = 0.52^*), and pH (R² = 0.51^*), which had a significance of 1% and 5%. The fiber content of sweet potato storage roots was found to have increased with increasing phosphorus content, organic matter and pH in the soil. However, there was no correlation with the amount of precipitation, days of precipitation and hours of sunshine with the fiber content of sweet potato at the selected sites.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.1-5
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• 2022

We investigate the effect of surface disorder on the lower critical field (H_c1) of MgB₂ thin films with a thickness of 850 nm, where the disorder on the surface region is produced by the irradiation of 140 keV Co ions with the dose of 1 × 10¹⁴ ions/cm². The thickness of the damaged region by the irradiation is around 143 nm, corresponding to ~17% of the whole thickness of the film, thereby forming the disordered MgB₂ overlayer on the pure MgB₂ layer. The magnetic field dependence of magnetization, M(H), for the pristine MgB₂ thin film and the film with overlayer is measured at various temperatures, and H_c1 is determined from the difference (△M) between the Meissner line and magnetization signal with the criterion of △M = 10^-3 emu. Intriguingly, the film with the disordered overlayer shows a remarkably large H_c1(0) = 108 Oe compared to the H_c1(0) = 84 Oe of pristine film, indicating that the disordered MgB₂ overlayer on the pure MgB₂ layer serves to prevent the penetration of vortices into the sample. These results provide new ideas for improving the superheating field to design high-performance superconducting radio-frequency cavities.

• Journal of Soil and Groundwater Environment
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• v.20 no.6
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• pp.28-36
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• 2015

Simultaneous mobility reduction of explosives and heavy metals in an operational range by monopotassium phosphate (MKP) and bentonite spreading technology was investigated. Potassium ion and phosphate ion in MKP act as explosives sorption enhancer and insoluble heavy metal phosphate formation, respectively, while bentonite acts as the explosives adsorbent. Then, the decrease in surface water concentration of the pollutants and resulting risk reduction for local residents of the operational range, by MKP/bentonite application was estimated. Under untreated scenario, the noncancer hazard index (HI) exceeded unity on February, July and August, mainly due to 2,4,6-trinitrotoluene (TNT); however, MKP/bentonite treatment was expected to lower the noncancer hazard index by decreasing the surface water concentration of explosives and heavy metals (especially TNT). For example, on July, estimated surface water concentration and HI of TNT were 0.01 mg/L and 1.1, respectively, meanwhile the sorption coefficient of TNT was 3.9 mg¹⁻ⁿkg⁻¹Lⁿ. However, by MKP/bentonite treatment, the TNT sorption coefficient increased to 113.8 mg¹⁻ⁿkg⁻¹Lⁿ and the surface water concentration and HI decreased to about 0.002 mg/L and 0.2, respectively. Based on the result, it can be concluded that MKP/bentonite spreading is a benign technology that can mitigate the risk posed by the pollutants migration from operational ranges.

• Journal of Marine Life Science
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• v.7 no.2
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• pp.102-112
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• 2022

Crucian carp, Carassius carassius (Weight 39.7±3.1 g, Length 14.8±0.5 cm) were exposed to waterborne nickel at 0, 10, 20, 40, 80 and 160 mg Ni²⁺/l. The lethal concentration 50 (LC₅₀) of C. carassius exposed to waterborne nickel was 117.69 mg Ni²⁺/l. In hematological parameters, RBC counts was significantly increased at 48 hours, whereas a significant decrease was observed at 96 hours. The MCV and MCH were significantly increased in the concentration of 80 mg Ni²⁺/l at 96 hours. The plasma components such as calcium, magnesium, glucose, cholesterol, total protein, AST, ALT and ALP were significantly changed by waterbonre nickel exposure. The results of this study suggest that the nickel exposure to C. carassius affects the survival rates, hematological parameters and plasma components as toxicity

• 한국해양학회지
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• v.29 no.3
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• pp.258-268
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• 1994

Nitrogenous new production and regenerated production were measured in the southern part of the Yellow Sea (Hwanghae) using a stable isotope /SUP 15/N nitrate and ammonia between April 25∼30, 1993. Nitrogen production varied between 155 and 688 mg N m/SUP -2/ d/SUP -1/, which belongs to meso to eutrophic area values. This is equivalent to 881∼3909 mg C m/SUP -2/ d/SUP -1/, assuming the Redfield ratio for C:N of 5.7:1 (by weight). the f0ratio which is the fraction of new production from primary production, varied between 0.12 and 0.26, indicating that 74 to 88% of primary production was supported by the regeneration of nutrients within the euphoric zone. This low f0ratio is the characteristics of the oligo- to mesotrophic area. Contrary to the expected, the ambient nutrient concentration was not an important factor for controlling productivity in this area during the study period. The difference in productivity among stations was mainly due to the variations in phytoplankton biomass in different water masses.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.355-364
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• 2022

BACKGROUND: Pre-harvest interval and decline pattern of thiamethoxam were determined in kiwifruit using liquid chromatography-tandem mass spectrometry (LCMS/MS). The study was carried out to propose import tolerance using OECD maximum residue limit (MRL) calculator for the export promotion of kiwifruit to Taiwan. METHODS AND RESULTS: The thiamethoxam residue in kiwifruit was determined by using the LC-TriQ-MS/MS with the analytical process to set up the import tolerance under greenhouse conditions for Taiwan. Excellent linearity was observed for all of the analytes with a determination coefficient (R²)≥0.99. The limit of quantification was determined to be 0.01 mg/kg for both thiamethoxam and clothianidin in kiwifruit. Linearity was determined from the co-efficient of determinants (R²) obtained from the seven-point calibration curve. The standard calibration curve showed as follows; 1) Site 1 (Gimje): y = 944,406X + 1,583 (R²=0.9995), 2) Site 2 (Goheung): y = 1,356,205X + 934 (R²=0.9983), and 3) Site 3 (Jangheung): y = 1,239,937X - 3,090 (R²=0.9908). The residue of thiamethoxam in the kiwifruit for three decline trials showed the range of 0.35 to 0.56 mg/kg in site 1 (Gimje), 0.24 to 0.55 mg/kg in site 2 (Goheung), and 0.28 to 0.42 mg/kg in site 3 (Jangheung), respectively. However, clothianidin was not detected in all of the treatments. The maximum residual amounts (decline) in the samples, sprayed according to the safe-use standard for thiamethoxam 10% WG in kiwifruit (30 days before harvest, 3 sprays every 7 days) were 0.56 mg/kg in site 1, 0.55 mg/kg in site 2, and 0.42 mg/kg in site 3, respectively. CONCLUSION(S): The import tolerance (IT) of thiamethoxam for kiwifruit may be proposed to be 0.9 mg/kg by using the OECD MRL calculator.