• Journal of Korean Society for Atmospheric Environment
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• v.10 no.2
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• pp.130-136
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• 1994

Concentration of volatile particulate nitrate(NH$_4$NO$_3$) in TSP in ambient air was determined from Feb. to Oct 1993. Sampling was carried out using a two-stage Andersen air sampler at the top of a five-story building located at Kon- Kuk University in Seoul Concentration of NH$_4$NO$_3$ in TSP was measured by Pyrolysis of sample filters at 16$0^{\circ}C$ for 1hr. Concentration of NH$_4$NO$_3$ was higher in winter time compared with that in summer time. Also, concentration of NH$_4$NO$_3$ was higher in fine particles compared with that in coarse particle. The range of NH$_4$NO$_3$concentration was between 2.99 and 9.86 $\mu\textrm{g}$/㎥. Weight fraction of NH$_4$NO$_3$ in total particulate nitrate was 31.1~59.5%, and weight fraction of NH$_4$NO$_3$ in YSP was 2.1~11.2%.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.85-88
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• 2005

The properties of pcc using BOF-slag were investigated in order to use as fine aggregate, which has been made in the steel making process and stabilized by air-jet method. The fluidity of flesh concrete has been improved with the usage of BOF-slag and it should be noted that the air content goes up. The compressive strength of hardened concrete was reduced at weight fraction over 50$\%$ and Young's modulus tends toward the trivial change. Also, the flexural and tensile strengths were increased with the usage, especially, the rupture values were increased to 1.2 times at the weight fraction of 30$\%$.

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.64-71
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• 1995

Tests were performed to evaluate the effect of thermal shock behavior on the mechanical properties of PC(poly-carbonate) and PET(polyethylene-terephthalate) with MBS(methylmethacrylate-butadiene-styrene) alloy. Five different material weight fraction for PC/PET were employed : 0/100, 25/75, 50/50, 75/25, and 100/0. Three different weight fraction of MBS were added to each PC/PET : 0, 3, and 9. Therefore fifteen different types of PC/PET/MBS were prepared using single screw extrude. and injection molding machine. One thermal shock cycle consisted of each one hour stay at -$40^{\circ}C$ chamber and $＋80^{\circ}C$ chamber without delay. Specimens were thermal shocked up to 20 and 40 cycles. Specific mechanical properities considered in this study include tensile, izod impact, and high rate Impact behaviors. In addition, the morphology of the fractured surface after Izod impact testing was investigated by the SEM (scanning electron microscope).

• Structural Engineering and Mechanics
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• v.85 no.5
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• pp.645-654
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• 2023

Based on first-order shear deformation theory, a wave propagation model of graphene platelets reinforced metal foams (GPLRMFs) circular plates is built in this paper. The expressions of phase-/group- velocities and wave number are obtained by using Laplace integral transformation and Hankel integral transformation. The effects of GPLs pattern, foams distribution, GPLs weight fraction and foam coefficient on the phase and group velocity of GPLRMFs circular plates are discussed in detail. It can be inferred that GPLs distribution have great impacts on the wave propagation problems, and Porosity-I type distribution has the largest phase velocity and group velocity, followed by Porosity-III, and finally Porosity-II; With the increase of the GPLs weight fraction, the phase- and group- velocities for the GPLRMFs circular plate will be increased; With the increase of the foam coefficient, the phase- and group- velocities for the GPLRMFs circular plate will be decreased.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2008.10a
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• pp.11-12
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• 2008

Poly(ethylene oxide)(PEO) of molecular weight of 300,000 was crosslinked by UV irradiation in the presence of crosslinker. The photochemical crosslinking of PEO was enhanced by the addition of dimethacrylate crosslinkers in the film. Percent conversion of the polymer into gel as well as water absorbency were investigated gravimetrically. Gel fraction of PEO films increased with increasing crosslinker concentration. In the case of photocrosslinked PEO films with benzophenone, gel fraction reached about 95%. The thermal behavior of crosslinked PEO films was characterized by thermogravimetric analysis. The maximum decomposition temperature increased with increasing crosslinker concentration.

• Journal of Life Science
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• v.5 no.3
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• pp.117-120
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• 1995

Human milk was examined for antiangiogenic activities by using the chick embryo chorioallantoic membrane (CAM) assay and endothelial cell growth. The low molecular weight (20 KD>$\sim$ ) fraction of human milk stimulated the angiogenesis and increased the endothelial cell growth. These results suggest that the increase of angiogenesis and endothelial cell growth might be attributed to several growth factors and/or angiogenic factors in low molecular fraction (20 KD>$\sim$) of human milk.

• Archives of Pharmacal Research
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• v.12 no.1
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• pp.22-25
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• 1989

Ethylacetate fraction from Orobanche crenata, contained two phenylpropanoid glycosides, exhibited some pharmacological properties. It was found to be non-toxic to rats in oral doses up to 500mg/100gm body weight. In large doses, it lowered the arterial blood pressure of anaethetised rats, and produced significant analgesic effect in mice and diuretic effect in rats. It further showed smooth muscle relaxant and antispasmodic effects in the isolated rabbit intestine and guinea-pig ileum respectively.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.114-114
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• 2022

There are 28 families and 166 species of exotic weeds on agricultural land and among these, 23 families and 80 species of exotic weeds occur on pastures. Among them, the Solidago altissima is a perennial weed belonging to the asteraceae family and it is an exotic weed that spreads to the surrounding area using methods such as high seed production, vegetative propagation using underground rhizomes and allelochemical. Accordingly, in 2009, the Ministry of Environment designated it as an ecosystem-disrupting species. This study was conducted to obtain basic data about the effects of S.altissima derived allelochemicals on forage crops. The root of S.altissima was separated, dried in the shade and then pulverized to prepare an root powder. Powder was repeatedly extracted with methanol for 3 days and concentrated under reduced pressure to obtain an root methanol extract. Dissolve the extract in distilled water, dispense it in a separate-funnel and proceed with liquid-liquid extraction by adding equal amounts of n-haxane (Hex), chloroform (CHCI₃), ethyl acetate (EtoAC), and butanol (BuOH) in order of increasing polarity. A seed-bioassay was performed using fractions for each solvent, followed by separation and purification by silica gel column chromatography. As a result of the fraction germination test for each solvent, the IC₅₀ values using the fresh weight of each fraction were 898.3 mg L^-1, 676.3 mg L^-1, 1160 mg L^-1 and 1360 mg L^-1. CA, CB, and CC fractions were obtained through primary silica gel column chromatography that used CHCI₃ fraction. As a result of seed-bioassay using each fraction, the IC₅₀ values for the fresh weight of each fraction was 537.3 mg L^-1, 1280 mg L^-1 and 1947 mg L^-1. Based on this, 5 fractions were obtained as a result of secondary silica gel column chromatography using the CA fraction. A seed-bioassay was performed, as a result, the lowest IC₅₀ value was calculated as 226.7 mg L^-1 in the CAE fraction. Based on this, the fraction was analyzed by GC-MS. The results of this study can be used as basic research data on the effects of weeds on forage crops and allelochemicals secreted from S. altissima.

• Korean journal of food and cookery science
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• v.18 no.2
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• pp.200-205
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• 2002

Corn starch was modified by the oxidation with sodium hypochlorite(NaOCl) and the changes in the distribution of molecular weight were examined. Corn starch was oxidized with 0.25, 0.5, 0.75, 1.0, and 1.5% active Cl/g of starch at pH 7.0 and 25$^{\circ}C$ for 10 min. Oxidation of corn starch caused a change in the molecular weight distribution of amylopectin. The fraction of highest molecular weight in native starch decreased gradually and the fraction of lower molecular weight increased with increasing oxidation. Also, λ$\sub$max/ and iodine binding capacities of oxidized starches decreased and the soluble carbohydrate content increased by oxidation. The differential scanning calorimetric results of oxidized starches showed that the temperature and enthalpies of gelatinization were not changed by oxidation; however, the more the starch was oxidized, the greater the extent of retrogradation.

• Journal of Nutrition and Health
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• v.30 no.1
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• pp.25-31
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• 1997

The effects of Trichosanthes kirilowii Max. subfractions, which has long been used as a wild vegetable and folk medicine, on insulin activity and acute toxicity were investigated. Diabetes melitus was induced in male Sprague-Dawley rats by the injection of streptozotocin(STZ) into the tail vein at a dose of 45mg/kg. The hexane fraction of the plant was subfractioned by silica gel column chromatography and were administered orally for 14 days and the normal and STZ-control group were orally administered with tween 80. The body weight gain was monitored and plasma levels of glucose, cholesterol, triglyceride, free fatty acid HDL-cholesterol were determined. The plasma activities of aspartate aminotransferase(AST) and alanine aminotransferase (ALT) were analysed. The subjraction A of hexane fraction lowered plasma glucose levels significantly and increased insulin activity compared to that of STZ-control. The activities of AST and ALT were decreased by administration of subfractions A and C of hexane fraction. The intakes of the hexane fraction of Trichosanthes kirilowii Max. did not showed the acute toxicity. It is suggested from the results that the subfraction A of the hexane fraction of Trichosanthes kirilowii Max. showed a hypoglycemic effect on diabetic rats and that the subfraction may be beneficial for insulin secreation.