• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.6
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• pp.135-142
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• 2001

Laboratory experiment was performed to evaluate the influence of mixing conditions to the strength of solidified sandy soils with cement. The major physical factors considered in this experiment were the fine particles content(<$\sharp200%$), cement content(%) and water-cement ratio, and unconfined compressive strength test was performed on the samples at 7 and 28 cured day. The results of tests shows that when the cement content is relatively low (7~10 percents) the fine content in the sandy soils is very important, but when cement content is high the water-cement ratio became more important. It was appeared that in the range of the cement content of 7~10 percents, about 20~30 percents of fine content to the total sample weight is the optimum condition to get the maximum strength. In the case of the cement content of 13 percents, the strength of sample was considerably affected by the water-cement ratio rather than the fine content. In this paper, empirical equations were also developed and evaluated to verify the relationship among three factors by the multi-regression analysis.

• Food Science of Animal Resources
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• v.18 no.4
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• pp.285-291
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• 1998

Adsorption isotherms of water vapour for infant formula milk powders manufactured by P. M. and N company in Korea were measured at temperatures between 20, 30 and 40$^{\circ}C$ using COST-90 modified method. Results showed that the isotherms were sigmoidal in shape. The adsorption isotherms of milk powder were depending on the temperature and products. The BET-model were applied and analyzed to compare the experimental value. It was found that the BET-model is fitted with measuring data. Sample P showed the lowest monolayer value and sample N showed the highest. Isosteric heat obtained upon application of BET-model was calculated in this field of temperature using the Clausius-Clapeyron equation. It is suggested that the usage of the BET-model to estimate the heat of water sorption in infant formula milk powder should be in agreement with the results from COST-90 project.

• Journal of the Korean Chemical Society
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• v.62 no.2
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• pp.113-117
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• 2018

The basic hydrogel lens with addition of N,N-dimethylacrylamide (DMA) and N-methyl-N-vinylacetamide (NMV) were manufactured. The optical and physical characteristics of ophthalmic lens were evaluated by measuring water content, oxygen permeability (Dk), refractive index and optical transmittance. The water content & oxygen permeability (Dk) of sample containing Ref., DMA group and NMV group was in the average of 34.48%, 35.54~49.19% & $13.003{\sim}18.468{\times}10^{-11}(cm^2/sec)$($mlO_2/ml{\times}mmHg$) and 36.28~44.95% & $12.270{\sim}16.883{\times}10^{-11}(cm^2/sec)$ ($mlO_2/ml{\times}mmHg$), respectively. And also, refractive index of the sample containing Ref., DMA group and NMV group was in the average of 1.4350, 1.4330~1.4131 and 1.4335~1.4195, respectively. Standard hydrogel monomer containing DMA and NMV was expected to be used usefully as a material for fabricating hydrophilic functional ophthalmic lens.

• Environmental Engineering Research
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• v.24 no.4
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• pp.654-661
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• 2019

This study assessed the stabilization of fluorine (F)-contaminated soil using calcium hydroxide (Ca(OH)₂) and the consequent changes in human health risk. The bioavailable F decreased to 3.5%, (i.e., 57.9 ± 1.27 mg/kg in 6% Ca(OH)₂-treated soil sample) from 43.0%, (i.e., 711 ± 23.4 mg/kg in control soil sample). This resulted from the conversion of water-soluble F to stable calcium fluoride, which was confirmed by XRD spectrometry. Soil ingestion, inhalation of fugitive dust from soil, and water ingestion were selected as exposure pathways for human health risk assessment. Non-carcinogenic risks of F in soils reduced to less than 1.0 after stabilization, ranging from 4.2 to 0.34 for child and from 3.0 to 0.25 for adult. Contaminated water ingestion owing to the leaching of F from soil to groundwater was considered as a major exposure pathway. The risks through soil ingestion and inhalation of fugitive dust from soil were insignificant both before and after stabilization, although F concentration exceeded the Korean soil regulatory level before stabilization. Our data suggested that substantial risk to human health owing to various potential exposure pathways could be addressed by managing F present in soil.

• Bulletin of the Korean Chemical Society
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• v.23 no.10
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• pp.1381-1391
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• 2002

The solvent sublation using ion pairs of metal-2-naphthoate(2-HNph) and tetrabutyl ammonium ($TBA^+$) ion has been studied for the concentration and determination of ultra trace Bi(III), In(III) and Tl(Ⅲ) ions in water samples. The partition coefficients ($K_p$) and the extraction percentages of 2-HNph and the ion pairs to methyl isobutyl ketone (MIBK) were obtained as basic data. After the ion pair $TBA^+$·M$(Nph)_4^-$ was formed in water samples, the analytes were concentrated by the solvent sublation and the elements were determined by GF-AAS. The pH of the sample solution, the amount of the ligand and counter ion added and stirring time were optimized for the efficient formation of the ion pair. The type and amount of optimum surfactant, bubbling time with nitrogen and the type of solvent were investigated for the solvent sublation as well. 10.0 mL of 0.1 M 2-HNph and 2.0 mL of 0.1 M $TBA^+$ were added to a 1.0 L sample solution at pH 5.0. After 2.0 mL of 0.2%(w/v) Triton X-100 was added, the ion pairs were extracted into 20.0 mL MIBK in a flotation cell by bubbling. The analytes were determined by a calibration curve method with measured absorbances in MIBK, and the recovery was 80-120%.

• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.225-233
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• 1999

Electrical resistivity of a rock-sample is dependant on not only formation factor of rock itself but also many parameters such as fluid type, measuring device, temperature, water saturation, electrical contact between electrode and core section, induced polarization, and frequency of electric source. In this study, we attempt to verify various affecting factors in core resistivity measurements and to find a better environment for core resistivity measurement. Particularly great attention has been paid to understanding the effects of temperature, water saturation, contact condition between sample and electrodes, and frequency of electric source. Precise measurement of resistivity can be achieved by utilizing silver paste for better contacts, taping samples for constant moisture contents, and using time-series resistivity data.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.6
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• pp.387-395
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• 2014

A highly sensitive analytical method based on stir bar sorptive extraction (SBSE) technique and gas chromatography/tandem mass spectrometry (GC-MS/MS) has been developed, allowing the simultaneous multi-analyte determination of 11 synthetic fragrances (SFs) in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 40 mL of water sample at pH 3 and stirred at 1,100 rpm for 120 min. Other SBSE parameters (salt effect and presence of organic solvent) were optimised. The method shows good linearity (coefficients > 0.990) and reproducibility (RSD < 10.9%). The extraction efficiencies were above 83% for all the compounds. The limits of detections (LOD) and limits of quantification (LOQ) were 2.1~4.1 ng/L and 6.6~12.9 ng/L, respectively. The developed method offers the ability to detect 11 SFs at ultra-low concentration levels with only 40 mL of sample volume. Matrix effects in tap water, river water, wastewater treatment plant (WWTP) final effluent water and seawater were investigated and it was shown that the method is suitable for the analysis of trace level of 11 SFs. The method developed in the present study has the advantage of being rapid, simple, high-sensitive and both user and environmentally friendly.

• The Korea Journal of Herbology
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• v.20 no.4
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• pp.17-26
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• 2005

Objectives : Antioxidant, Anticancer and Antibacterial Activities of Naesohwangryntang and its composition oriental medicines. Methods : We were experimented anti-oxidation effect and growth inhibition ability on cancer cells and antibacterial activity on various kinds of bacteria of skin. Results : The results were obtained as follows : Electron donating ability(EDA) of water extract Naesohwangryntang and ethanol extract Naesohwangryntang was 60% and 70% at 1000 ppm concentration. In the test of SOD-like activity, ethanol extract showed more activity with 27.4% in 700 ppm, while water extract was low in 19.6%. Clear zones formed by sample against the human skin-resident microflora indicated that anti-microbial activity of ethanol extract Naesohwangryntang was higher than that of water extract Naesohwangryntang. The growth inhibition rates of each sample on lung-cancer(A549), at 1000 ppm cancer cell was over 40%. The growth inhibition rate of the each sample melanoma-cancer(B16F10, G361), at 1000 ppm was over 80%. Conclusions : The results indicated that, ethanol extract which is superior in its anti-oxidation and antibacterial effect is useful to be applied in cosmetic industry.

• Korean Journal of Environmental Agriculture
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• v.13 no.3
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• pp.262-270
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• 1994

The established methods in the residue analysis of endosulfan require an extensive sample clean-up prior to quantification by relatively complex equipment. A radioimmunoassay(RIA) provides a simple procedure with theoretically higher sensitivity and specificity necessitating only a minimum of sample clean-up. Endosulfan-specific antibodies were developed in rabbits by using a bovine serum albumin(BSA) conjugate wherein the alcohol form of endosulfan was multiply bound to the protein via succinylation. Produced antibodies showed the high titers to endosulfan-BSA(1 : 32,000). An RIA method was developed in water and carp by using $^{14}C-labeled$ endosulfan as a tracer. The lowest detection amount of endosulfan was 1 ng in the liver, kidneys, gut and water samples, and 3 ng in the whole body sample of carp without any clean-up, corresponding to 0.1 ppb of endosulfan.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.3
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• pp.34-40
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• 2000

A multisample extraction device was newly designed for efficient extraction of dissolved lipophillic organic compounds from sea water sample. This device allowed extraction of organic compounds from up to 96 sample at a time using 96 multifolder on the principle of solid phase extraction with commercially available octadecyl silane (ODS) cartridges. The recovery yield of the new divice was higher than 90 % while that of conventional liquid-liquid extraction process are only 60 - 70 %. The amount of solvent required for the new device could be reduced to less than 20㎖ per 1ℓ of sample while 1 - 2 ℓ of solvent were used in the conventional liquid-liquid extraction process. The usefulness of this novel method was demonstrated with sea water samples collected from Yellow sea, and the qualitative and quantitative analyses results of the dissolved hydrocarbon showed this method was superior to that of conventional liquid-liquid extraction process in efficiency and reliability.