• YAKHAK HOEJI
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• v.54 no.6
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• pp.429-440
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• 2010

HS-SPME-GC/MS was studied and optimized for the determination of 17 orgarnophosphorous pesiticides (OPPs: chlorpyrifos, chlorpyrifos-methyl, demeton-s-methyl, diazinon, dimethoate, EPN, fenitrothion, fenthion, malathion, methidathion, monocrotophos, parathion, phenthoate, phosphamidon, sulfotep, terbufos, triazophos) in blood. Optimum SPME parameters were selected: choice of SPME fiber (85 ${\mu}m$ polyacrylate), pH effect (0.5 N HCl), salt effect ($Na_2SO_4$, 0.2 g; 20%), headspace incubation temperature ($80^{\circ}C$), headspace incubation time (1 min), headspace adsorption time (30 min) and GC desorption time (2 min). These parameters were optimized using HS-SPME autosampler coupled with gas chromatography-mass spectrometry (GC-MS). Method validation was carried out in terms of linearity, limit of detection (LOD), limit of quantitation (LOQ) and recovery in blood. The assay was linear over 0.5~5.0 mg/l ($r^2$=0.955~1.000). Limit of detection (LOD) and limit of quantitation (LOQ) in blood were determined 0.03~0.3 mg/l (S/N=3) and 0.1~1.1 mg/l (S/N=10), respectively. Relative recovery with 0.5, 1 and 5 mg/l (in blood) were 90.8%, 98.5% and 94.1%, respectively. This method will be applied to the determination of the orgarnophosphorous pesticides in postmortem blood. The proposed protocol can be an attractive alternative to be used in routine toxicological analysis.

• Journal of the Korean Geotechnical Society
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• v.39 no.9
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• pp.35-50
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• 2023

A preliminary study is conducted to develop seismic design guidelines for temporary retaining structures in a deep excavation. The study involved a comprehensive literature review of the seismic design standards applied domestically and internationally, as well as various methods to calculate seismic earth pressure for pseudostatic analysis. The FLAC 2D, a two-dimensional finite difference analysis program, was utilized to perform pseudostatic analysis using the Semirigid pressure method, Wood method, and Mononobe-Okabe method. The resulting analysis data for the wall moment and axial force of the strut were compared with the dynamic analysis outcomes to evaluate the applicability of pseudostatic analysis. The Semirigid pressure method predicted the most reasonable moment for Stiff walls experiencing horizontal displacements up to 0.4%H. Predicting the axial force of the strut exactly was challenging because the pseudostatic analysis cannot consider dynamic soil-structure interaction; however, it is deemed available for conservative preliminary review to ensure safety.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.23 no.6
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• pp.151-166
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• 2020

Various experience keywords were derived through text mining analysis of two National Ecological and Cultural Exploration Routes. The results of this study were drawn as follows: The interaction between the experience keywords was analyzed by the degree centrality, closeness centrality, and betweenness centrality value calculated through the centrality analysis of the research site experience keywords. First, In the text mining analysis, 'walking' appeared as the top keyword in the I, II, and III periods of the two target areas. The keywords related to the stay type of "rental cottage" and "recreational forest" were derived for Masil Road in relation to accommodation facilities. However, the keywords related to the accommodation were not derived in Gubul Road. Second, as a result of the centrality analysis, the degree centrality of the keywords "walking", "sea", "look", "salt flats" of Masil Road and "walking", "lake" and "park" of Gubul Road was high. The keywords located at the center are "walking" and "sea" in the Masil Road, and "walking" in the Gubul Road. As an influential keyword, Masil Road is "experience" and Gubul Road is "history". Third, According to the results of the analysis, the keywords that appeared at the top of the Gubul Road are derived from the keywords related to the 1 ~ 8 course, and it is judged that the visitors are visiting the 1 ~ 8 course trail evenly. However, the Gubul Road only appears in the top keyword only for a few courses. Through this, it seems that three courses are intensively visited as the main course of 6 Gubul Road, 6-1 Gubul Road, and 8 Gubul Road.

• ETRI Journal
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• v.26 no.6
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• pp.647-652
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• 2004

A new ionic liquid, 1-vinyl-3-heptylimidazolium iodide (VHpII), was synthesized and applied as a redox electrolyte for dye-sensitized solar cells. The chemical structure of the synthesized VHpII was confirmed using $^1H$ NMR. Thermogravimetric analysis showed that the VHpII was stable for thermal stress of up to $250^{\circ}C$. The energy conversion efficiencies of the VHpII-based dye-sensitized solar cells were investigated in terms of the effect of a lithium iodide addition. A solar cell containing the redox couple of VHpII and iodine showed a conversion efficiency of 2.63% under 1 sun light intensity at AM 1.5. Adding 0.4 M LiI results in a conversion efficiency of 3.63%, which was an improvement of about 40%. The increased conversion efficiency was ascribed to an increase in external quantum efficiency.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.527-530
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• 2002

In the present study, immersion test using artificial seawater was performed to evaluate the resistance of mortar specimens with or without ground granulated blast-furnace slag (SG) and fly ash (FA). Another variable was the fineness levels of SG (4,450, 6,000 and 8,000 ㎠/g). From the results of the immersion test for 270 days of exposure, the excellent resistance to seawater attack for SG mortar mixtures, especially in a high fineness levels, was confirmed. However, the reductions in compressive strength of FA mortar specimens was similar to those of OPC mortar specimens irrespective of replacement of FA.. In order to understand the deterioration mechanism due to seawater attack, X-ray diffraction (XRD) analysis were also carried out. Some reactants such as ettringite, gypsum, brucite and Friedel's salt were possibly detected through XRD technique.

• Advances in nano research
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• v.2 no.3
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• pp.147-155
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• 2014

Among the various nanoparticles reported for commercial applications, considerable interest has been generated by the use of silver nanoparticles. Owning to extremely small size, silver nanoparticles exhibit enhanced properties when compared with the bulk material. In this research work, silver nanoparticles were prepared by the reduction of silver salt with a reducing agent by a solvothermal method using different solvent mediums such as ethanol, hexane, toluene and acetone with water. The prepared silver nanoparticles were characterized systematically by X-ray diffraction (XRD), particle size analysis and scanning electron microscope (SEM). The results revealed the formation of pure silver phase and nano-sized particles. Among the different solvent mediums used, the silver nanoparticles prepared by hexane and water as solvent mixture resulted in very low particle size.

• Preventive Nutrition and Food Science
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• v.22 no.3
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• pp.223-230
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• 2017

The purposes of this study were to produce polysaccharides from red pepper stems using different extraction methods and evaluate their chemical composition, in vitro biological capacities, and rheological properties. Two polysaccharides were extracted from red pepper stems using an autoclave and alkali treatments, and the extracts were named PAU and PAL, respectively. The contents of total phenolics and flavonoids were significantly higher in PAU than those in PAL. PAU exhibited greater scavenging activities on 2,2-diphenyl-1-picrylhydrazyl radicals, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radicals, superoxide radicals, and nitrite compared to PAL, suggesting that PAU served as better antioxidants. Similarly, in vitro inhibitory abilities against carbohydrate hydrolyzing enzymes of PAU were higher than those of PAL. Steady shear rheological analysis demonstrated that PAU showed higher psuedoplastic shear-thinning behavior compared to PAL. Based on the results from dynamic shear rheological properties, it was found that both samples had predominantly viscous behavior rather than elastic behavior.

• Environmental Analysis Health and Toxicology
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• v.1 no.1
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• pp.77-80
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• 1986

Radiochemical synthesis of $N^{G}$-mono［$^{14}$ C-methyl］-L-arginine is described. The compound was synthesized from radio-active mono［$^{14}$ C］-methylamine as easily and purified by strong cation-exchange resin (NH form) liquid chromatography using a gradient of ammonium hydroxide, and crystallized as flavianate. The free amino acid was successfully prepared by strirring its flavianate and strong anion-exchange resin (OH- form), which could remove the flavianic acid from its salt in water below room temperature. Purity of the compound was tested by thin-layer chromatography, thin-layer electro-phoresis, and scintillation spectrometry.y.

• YAKHAK HOEJI
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• v.7 no.2_3
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• pp.67-71
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• 1963

Studies the reaction mechanism and optimal reaction condition of the process of preparing sodium isocyanate, by means of heating of sodium carbonate and urea. Proposing, at the sametime, the quantitative analyzing method of sodium isocyanate in the presence of impurities of $Na_{2}CO_{3}$, urea and biuret. 1. Sodium isocyanate could be prepared by means of heating reaction of sodium carbonate and urea. 2. Adding urea into the heated sodium carbonate is reasonable. 3. Quantitative analysis of sodium isocyanate in the presence of impurities, $Na_{2}CO_{3}$, urea and biuret could be done by the following method:-adding nitrobarite solution into sample solution in order to remove $CO_{3}"$ and neutralize the solution, filtering off $BaCO_{3}$, and then precipitating isocyanate as a silver salt, filtering off AgNCO, and then, titrating remaining $AgNO_{3}$ with $NH_{4}SCN$, (indicator $FeNH_{4}(SO_{4})_{2})$/TEX>

• Journal of the Korean Ceramic Society
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• v.25 no.4
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• pp.408-414
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• 1988

This thesis is 2nd thesis from "Mechanism of Intercalation Compounds in Graphite with Hydrogen sulfate(J. Korea Cer. Soc. Vol. 22. No.6, 1985). We have oxidized natural Graphite flakes(0.1~0.2mm., Kropfm hl passau in Deutchland. S40) with a solution of CrO3 in H2SO4. Whilst persulfate ions were intercalated, too, below 7$^{\circ}C$, no evidence for intercalation of a peroxo compound was found at 22$^{\circ}C$. The reaction was interrupted after various times by filtering and washing with concentrated H2SO4. X-ray diffraction showed that the 2nd stage compound had already been formed after 2 minutes. We could only follow further oxidation to the blue stage compound which was completed after 35 minutes. We have found six distinct intermediate stage between 2nd stage and 1 stage. Experiments are described on the formation of intermediate stage color and X-ray diffraction analysis.ysis.