• The Korean Journal of Pesticide Science
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• v.12 no.4
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• pp.315-322
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• 2008

In this study, a simple, effective, and sensitive method has been developed for the quantitative residue analysis of cyhalofop-butyl and its metabolite cyhalofop acid in water and soil when kept under laboratory conditions. The content of cyholofop-butyl and cyhalofop acid in water and soil was analyzed by first purifying the compounds through liquid-liquid extraction and partitioning followed by Silica gel (adsorption) chromatography. Upon the completion of the purification step the residual levels were monitored through high-performance liquid chromatography (HPLC) using a UV absorbance detector. The recoveries of cyhalofop-butyl from three replicates spiked at two different concentrations ranged from 82.5 to 100.0% and from 66.7 to 97.9% in water and soil, respectively. The limit of detection and minimum detection level of cyhalofop-butyl in water and soil was 0.02 ppm and 10 ng, respectively. The recoveries of cyhalofop acid ranged from 80.7 to 104.8% in water and from 76.9 to 98.1 % in soil. The limit of detection of cyhalofop acid was 0.005 ppm in water and 0.01 ppm in soil, while the minimum detection level was 2 ng both in water and soil. The half-live of cyhalofop-butyl was 4.14 and 6.6 days in water and soil, respectively. The method was successfully applied to evaluate cyhalofop-butyl residues in water and soil applied aj. 30% emulsion, oil in water (EW) product.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.416-421
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• 2002

This paper dealt with an experimental study on the hydro-elastic vibration of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the analytical method based n the relation between the reference kinetic and maximum potential energy and compared with the experimental results. Good agreement between the results was found for the natural frequencies of the perforated plates in air. It was empirically found that the natural frequencies of the perforated plate in air increase with an increase of P/D, on the other hand, the natural frequencies of the perforated plate in contact with water decrease with an increase of P/D. Additionally, the effect of the submerged depth on the natural frequency was investigated.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.4 no.4
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• pp.25-35
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• 2001

This study aims to find out the growth characteristics of riparian plants on the artificial floating islands (AFI). Three types of experiments were performed. The vegetation growth were compared by the plant-supporting materials; natural cotton mat, coir mat on the AFI or in the water, and natural soil at the waterfront. Major findings are; 1. The survival rate of riparian plants was 100% on both coir-mat and cotton-matislands, which implies that we may substitute cheaper cotton for expensive coir-mat. 2. Both natural cotton mat and coir mat were good for the growth of plants. Especially, the natural cotton mat was good for Sparganium stoloniferum and Miscanthus sacchariflorus, and the coir mat was good for Typha latifolia. 3. The growth rate of stem and root showed difference between the stem-removed plants and stem-remaining plants. As a whole, the growth rate of stem-removed plants was bigger than the one of stem-remaining plants. 4. The growth rate of plants showed difference between those grown on the AFI and those grown in the water. The growth rate of plant on the AFI was bigger than the one in the water. 5. The growth rate of plants on the AFI was bigger than the one on the natural soil at the waterfront.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.750-757
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• 2009

The ammonium ion exchange characteristics of natural zeolite were investigated to remove ${NH_4}^+-N$. The effect of water temperature, particle size and competitive cation on the exchange capacity was examined. Ammonium ion exchange capacity tended to decrease when the temperature increased from $25^{\circ}C$ to $40^{\circ}C$. Exchange capacity was increased according to the particle size of natural zeolite comes to be small. Batch isotherm experiments were conducted for measuring ammonium ion exchange capacity. The ion exchange capacity was well described either by the Langmuir isotherm model or by the Freundlich isotherm model. The ammonium ion exchange capacity ($q_m$) of zeolite carrier can be calculated $11.744mg-{NH_4}^+/g$-carrier. The ion exchange capacity of manufactured zeolite carrier was showed a similar tendency as ion exchange capacity of powder-sized natural zeolite. Therefore, zeolite carrier can be used for increasing of nitrogen removal efficiency in the wastewater treatment plants.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.70-78
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• 2003

This paper dealt with an experimental study on the hydroelastic vibration of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the analytical method based on the relation between the reference kinetic and maximum potential energy and compared with the experimental results. Good agreement between the results was found for the natural frequencies of the perforated plates in air. It was empirically found that the natural frequencies of the perforated plate in air increase with an increase of P/D, on the other hand, the natural frequencies of the perforated plate in contact with water decrease with an increase of P/D. Additionally. the effect of the submerged depth on the natural frequency was investigated.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.160-160
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• 2022

Floods are the most common natural disasters and are annually causing severe destructions worldwide. Human activities, along with expected increased extreme precipitation patterns as a result of climate change enhance the future potential of floods. There are proven evidence that infrastructure based responses to flood disaster is no longer achieving optimum mitigation and have created a false sense of security. Nature-based solutions(NBS) is a widely accepted sustainable and efficient approach for disaster risk reduction and involves the protection, restoration, or management of natural and semi-natural ecosystems to tackle the climate and natural crisis. Adoption of NBS in decision-making, especially in developing nations is limited due to a lack of sufficient scenario-based studies, research, and technical knowledge. This study explores the knowledge gap and challenges on NBS adoption with case study of developing nation, specially for flood management, by the study of multiple scenario analysis in the context of climate, land-use change, and policies. Identification and quantification of the strength of natural ecosystems for flood resilience and water management can help to prioritize NBS in policymaking leading to sustainable measures for integrated flood management.

• ALGAE
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• v.35 no.3
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• pp.225-236
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• 2020

Gymnodinium smaydae is a newly described mixotrophic dinoflagellate that feeds on only Heterocapsa spp. and Scrippsiella acuminata among 19 tested algal prey. It is one of the fastest growing dinoflagellates when feeding, but does not grow well without prey. To investigate its spatial-temporal distributions in Korean waters, we quantified its abundance in water samples that were seasonally collected from 28 stations along the Korean Peninsula from April 2015 to October 2018, using quantitative real-time polymerase chain reactions. This dinoflagellate had a wide distribution, as reflected by the detection of G. smaydae cells at 23 of the sampling stations. However, this distribution had a strong seasonality; it was detected at 21 stations in the summer and only one station in winter. The abundance of G. smaydae was significantly and positively correlated with chlorophyll a concentration as well as with water temperature. However, there were no significant correlations between the abundance of G. smaydae and salinity, concentrations of nutrients, or dissolved oxygen concentration. During the study period, G. smaydae was present when water temperatures were 7.6-28.0℃, salinities were 9.6-34.1, concentrations of NO₃ were not detectable-106.0 μM, and concentrations of PO₄ were not detectable-3.4 μM. The highest abundance of G. smaydae was 18.5 cells mL^-1 in the coastal waters of Jinhae in July 2017 when the chlorophyll a concentration was 127 mg m^-3 and water temperature was 23.8℃. Therefore, the spatial-temporal distribution of G. smaydae in Korean coastal waters may be affected by chlorophyll a concentration and water temperature.

• The Korean Journal of Ecology
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• v.7 no.4
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• pp.232-238
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• 1984

The author hatched the eggs of Korean frog, Rana nigromaculata in natural water, and reared the tadpoles in natural water as control group and in seven copper ion groups contaminated by 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, and 1.0 ppm of copper ion. The influences of copper ion on the growth of the tadpoles were analyzed, and the results were summarized as follows: 1) The copper ion inhibited the growth of the tadpole. 2) The tadpoles were not survived for 20 days in the copper ion of 0.4~0.5ppm, and in the 0.7ppm, the tadpoles were not survived for 1 day after hatch. 3) The critical lethal concentration of Korean tadpole is regarded as 0.6ppm of copper ion. 4) The growth of head with and body length show a convexin increase pattern. 5) In the growth quantity of head width and body length, that of natural water shows the most rapid increase pattern, and that of the copper ion groups 0.1, 0.2, and 0.3ppm follows in that order. 6) The coefficient of relative growth($\alpha$) of control group is the greatest value, and that of the copper ion groups of 0.1, 0.2, and 0.3ppm follows in that order. The natural water shows the positive allometry, the contaminated groups shows the negative allometry in the relative growth of the contaminated groups to the natural water. 7) Body length shows positive allometry in the relative growth to head width.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.519-519
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• 2003

We performed a hydrochemical study on a total of 89 bedrock groundwaters collected from preexisting wells (30 to 300 m deep) in the Boeun area. Hydrochemical data showed significant variations in the area, due to varying degrees of anthropogenic pollution. The waters were mostly enriched in Ca and HCO$_3$ but locally contained significant concentrations of anthropogenic constituents in the general order of Cl >NO$_3$>SO$_4$. In particular, about 11% of the examined wells exceeded the drinking water standard with respect to nitrate. We consider that aquifers in the area are locally highly susceptible to the contamination related to agricultural activities. Diagrams showing the relationships between the summation of cations (∑cations) and the concentration of several anions with different origin (natural versus anthropogenic) were used to estimate the relative role of anthropogenic contamination. A good correlation was observed for the relationship between ∑cations and bicarbonate, indicating that water-rock interaction (namely, hydrolysis of silicate minerals) is most important to control the water quality. Thus, we made an assumption that the equivalent of dissolved cations for a water should be equal to the alkalinity, if the chemistry were controlled solely by a set of natural weathering reactions. If we excluded the equivalent quantities of cations and bicarbonate (natural origin) from the acquired data for each sample, the remainder therefore could be considered to reflect the degree of anthropogenic contamination. Finally, we performed a multiple regression approach for hydrochemical data using the ∑cations as a dependent variable and the concentration data of each anion (natural or anthropogenic) as an independent variable. Using this approach, we could estimate the relative roles of anthropogenic and natural processes. Rather than the conventional evaluation scheme based on water quality criteria, this approach will be more useful and reasonable for the evaluation of groundwater quality in a specific region and also can be used for planning appropriate protection and remedial actions.

• The Journal of Korean Society of Virology
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• v.27 no.1
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• pp.87-95
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• 1997

Methanol and/or boiling water extraction of 201 natural products and subsequent MTT assay using MT-4 cell line was carried out to screen the anti-HIV-1 activity. Among 97 methanol extracts, 7 extracts from Chrysanthemi Indicium Flos, Magnoliae Cortex, Machili Cortex, Reynoutriae Rhizoma, Lithospermi Radix, Agastachis Herba, and Chaenomelis Fructus showed anti-HIV-1 activity and their SI value were 2.25 to 5.77. In addition, among 119 boiling water extracts, 10 extracts from Lonicerae Caulis et Foloium, Elsholtziae Herba, Leonuri Herba, Portulacae Herba, Schizonepetae Herba, Curcumae Rhizoma, Amomi Cardamomi Fructus, Cirsii Radix et Herba, Carpesii Herba, and Siegesbeckiae Herba showed anti-HIV-1 activity and their SI value were 1.30 to 7.64. Methanol extracts of above seven natural products were fractionated and the anti-HIV-1 activity of each fraction was examined. Extraction was carried out with hexane, chloroform, butanol, and water to trace active anti-HIV-1 componets. As a result, the water fraction of Magnoliae Cortex, Machili Cortex, Reynoutriae Rhizoma, Agastachis Herba, Chaenomelis Fructus and the butanol fraction of Chrysanthemi Indicium Flos, Reynoutriae Rhizoma showed anti-HIV-1 activity and their SI value were 1.40 to 8.02. We could reach a conclusion that studies to trace the anti-HIV-1 active component of each natural products in further fractionation and to identify its structure by Infrared spectroscopy, NMR spectroscopy and gel permeation chromatography were needed.