• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.179-189
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• 2000

The purpose of this research is to complement the existing researches on landfill bottom liners behavior during the periods of freeze and thaw. Landfill-related researches have been typically focused on small-scale soil samples that are often compacted under conditions different from those used in the field. Although these tests have been invaluable in clarifying the problem of freeze and thaw, extending the results of such experimental studies to prototype landfills are questionable. In this investigation, the author utilized a large scale laboratory simulation allowing inclusion of the field depth of the cover systems, layered soil profiles, rainfall simulation, a cold climate and boundary conditions similar to those encountered in the landfill. The soil materials were stabilized soils (mixed clays, cements, and minerals) instead of clays. The bottom liners are made up of drainage layer (30 cm), stabilized layer (75 cm), and leach collection layer (60 cm). The stabilized layers are made up of supporting layer (45 cm) and low permeable layer (30 cm) - consisting of $P_A\; and\; P_B$ layer. As a results, depths of penetration increased by about 2~5 more centimeters at rainfall simulated designs than those at no rainfall simulated designs (that is design 3, design 5 and design 7) - it increased by about 20mm/day in the bottom liners and frost heaves also increased it by a few millimeters. Also, a few cracks appeared partly. According to these results, we can surmise that the compacted stabilized soil is more reliable than the compacted clay liners for construction of the landfill liners.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.385-394
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• 2017

In this study, reaction mechanism and curing characteristics of adhesives formulated with NaOH- and $H_2SO_4$-hydrolyzed chicken feather (CF) and formaldehyde-based crosslinkers were investigated by FT-IR and DSC. In addition, adhesive properties and formaldehyde emission of medium-density fiberboards (MDF) applied with the adhesives were measured. CF-based adhesives having a solid content of 40% and over were very viscous at $25^{\circ}C$, but the viscosity reduced to $300{\sim}660m{\cdot}Pa{\cdot}s$ at $50^{\circ}C$. Consequently, the adhesives could be used as a sprayable resin. Through the FT-IR spectra of liquid and cured CF-based adhesives, addition reaction of methylol group and condensation reaction between the functional groups with the use of formaldehyde-based crosslinkers were identified. From the analysis of DSC, it was elucidated for CF-based adhesives to require a higher pressing temperature or longer pressing time comparing to commercial urea-formaldehyde (C-UF) resin. MDF bonded with CF-based adhesives, which was formulated with 5% NaOH-hydrolyzed CF (CF-AK-5%) and PF of formaldehyde to phenol mole ratio of 2.5 (PF-2.5), and pressed for 8 min had higher MOR and IB than those with other CF-based adhesives. MOR and IB of MDF bonded with the CF-based adhesives regardless of formulation type and pressing time were higher than those with C-UF resin. When the values compared with the minimum requirements of KS standard, IB exceeded the KS standard in all formulations and pressing time, but MOR of only MDF bonded with CF-AK-5% and PF-2.5 and pressed for 8 min satisfied the KS standard. What was worse, 24-TS of MDF bonded with all CF-based adhesives did not satisfied the KS standard. However, MOR and 24-TS can be improved by increasing the target density of MDF or the amount of wax emulsion, which is added to improve the water resistance of MDF. Importantly, the use of CF-based adhesives decreased greatly the formaldehyde emission. Based on the results, we reached the conclusion that CF-based adhesives formulated under proper conditions had a potential as a sprayable resin for the production of wood panels.

• Journal of Aquaculture
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• v.21 no.2
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• pp.82-88
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• 2008

A 12-week feeding trial was conducted to investigate the effects of dietary supplementation of probiotics as a feed additive for juvenile Korean rockfish Sebastes schlegeli. Four experimental diets supplemented with no probiotic(Control), Bacillus polyfermenticus(BP), Bacillus licheniformis(BL) or Bacillus polyfermenticus plus Saccharomyces cerevisiae(BP+SC) at $1.0{\times}10^7$ CFU/kg diet as a dry-mater(DM) basis were prepared by mixing with a basal diet. After 12 weeks of the feeding trial, fish fed BP+SC diet showed significantly higher weight gain(WG), feed efficiency(FE), specific growth rate(SGR) and protein efficiency ratio(PER) than those of fish fed control diet(P<0.05), however there were no significant differences in WG, FE, SGR and PER among fish fed the BP, BL and BP+SC diets. Fish fed BP and BP+SC diets showed significantly higher condition factor(CF) than that of fish fed control and BL diets. Fish fed BP, BL, BP+SC diets showed significantly higher hepatosomatic index(HSI) than that of fish fed control diet, however there was no significant difference in HSI among fish fed BP, BL and BP+SC diets. Fish fed BP+SC diet showed significantly lower serum glucose than that of fish fed control diet, however there was no significant difference in serum glucose among fish fed BP, BL and BP+SC diets. Fish fed BP+SC diet showed significantly higher respiratory burst activity(NBT assay) than that of the fish fed control and BL diets, however there was no significant difference in NBT assay between fish fed BP and BP+SC diets. Fish fed BP and BL diets showed significantly higher lysozyme activity than that of the fish fed control diet, however there was no significant difference in lysozyme activity among fish fed BP, BL and BP+SC diets. Fish fed BP and BP+SC diets showed significantly lower cumulative mortality than that of the fish fed control diet, however there was no significant difference in cumulative mortality among fish fed BP, BL and BP+SC diets after the challenge test. From these results, dietary B. polyfermenticus, B. licheniformis and B. polyfermenticus plus S. cerevisiae supplementation in juvenile Korean rockfish diet could enhance growth performances, non-speicific immunities and a higher resistance against the specific pathogen.

• Korean Journal of Agricultural Science
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• v.10 no.2
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• pp.354-364
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• 1983

Confonmation of (Z)-cinnamonitrile have been studied by molecular orbital theoretically using extended Huckel theory(EHT) and CNDO/2 molecular orbital calculation methods. The results indicate that the stability of conformation is(Z)-gauch>(Z)-planar. The rate constants for alkalie hydrolysis of cinnamonitrile at pH 7.0-14.0 range have been determined by ultra-violet spectrophotometry in 50% methanol at $25^{\circ}C$ and the following rate equation which can be applied over wide pH range was obtained; $${\therefore}k=({\frac{1.41{\times}10^{-14}+1.21{\times}10^7/[H_3O^+]}{2.65{\times}10^{-7}+1.64/[H_3O^+]})+9.14{\times}10^9/[H_3O^+]$$ The rate equation reveals that, at pH 7.0-10.0, the reaction is initiated by the addition of water molecule to unsaturated cabon-carhon double bond of cinnamonitrile and ${\alpha}C-{\beta}C$ bond scission follow subsequently in neutral and alkalie media. At pH 12.0-14.0, in strong alkalie solution, that so-called Michael type nucleophilic addition that the over-all rate constants is only dependent upon the concentration of hydroxide ion occurs competitively and are very complicated. Hence, the reaction mechanism of alkalie hydrolysis of cinnamonitrile which did not carefully before can be fully explained.

• Journal of dental hygiene science
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• v.14 no.1
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• pp.7-14
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• 2014

This study aims to evaluate the impact of varying exposure to dental amalgam on urinary mercury levels in children by measuring the number of amalgam-filled teeth and the variance of mercury concentration in urine over a period of 2 years. A total of 317 (male 158, female 159) elementary school children (1st~4th graders) attending 2 schools in urban regions participated in this study. At 6-month intervals, 4 oral examinations were conducted to check any variance in the conditions of dental caries and the status of dental fillings. Also, urine tests were conducted followed by a questionnaire survey. To elucidate the factors potentially affecting the mercury concentration in urine, t-test, ANOVA, chi-square test and a mixed model were used for the analysis. Regarding the status of dental fillings in line with examination time periods, deciduous teeth had more amalgam-filled surfaces than those filled with resin, whereas permanent teeth had more resin-filled surfaces than those filled with amalgam. A significant relevance was found between the exposure to dental amalgam and urinary mercury levels. Specifically, subjects whose teeth surfaces had been filled with dental amalgam showed higher urinary mercury levels than those who had no dental amalgam fillings. Based on the analysis using the mixed model, the increase in the number of teeth surfaces filled with amalgam was found to be the factor affecting the increase in urinary mercury levels. The urinary mercury levels were found to be highly associated with the exposure to dental amalgam. The more the teeth surfaces filled with amalgam, the higher the urinary mercury levels. Hence, even a trace of dental amalgam fillings can liberate mercury, affecting the variance in the urinary mercury levels. These findings suggest that some criteria or measures should be developed to minimize the exposure to dental amalgam. Moreover, relevant further studies are warranted.

• Korean Journal of Weed Science
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• v.30 no.4
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• pp.361-370
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• 2010

This study was carried out to establish the analytical method of MCPA residue in brown rice and rice straw by HPLC/UVD. When MCPA was extracted from sample under the pH 3.6 by adding acetone 200 mL and 1N-HCl 100 mL, the extraction efficiency was high by 87%. And purification efficiency was high by 83% when 5 mL of 1% methanol/acetonitrile was eluated by the florisil Sep-pak cartridge column. From spiking of $0.1{\mu}g\;mL^{-1}$ and $0.25{\mu}g\;mL^{-1}$ of MCPA to control sample, respectively, average recovery rate of MCPA in brown rice was 96.0% and 94.9% and that in rice straw was 92.5% and 88.2%, respectively. Precision of experiment was very high by relative standard deviation of 1.5% to 5.7%. In brown rice and rice straw treated with bentazone+MCPA (11+1.2%) of 30 kg and 60 kg per ha at 30 days after rice transplanting, respectively, maximum residue limit was under $0.05{\mu}g\;mL^{-1}$ of the recommended rate of Korean Food and Drug Administration. From the above results, the analytical procedure of MCPA in plants such as hydrolysis, saponification and derivatization were ommited, and retention time was faster and recovery rate was higher than the existed results of HPLC/UVD. Therefore, these results were greatly improved and seemed to be usefully applied for residue analysis of MCPA in plants.

• Journal of the Economic Geographical Society of Korea
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• v.21 no.1
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• pp.20-33
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• 2018

Population distribution in urban space varies with transportation flow changing along time of day. Transportation flow is directly affected by the activities of urbanites and the distribution of related facilities, since the flow is the result of moving to the point where the facilities associated with their activities are located. It is thus necessary to analyze the spatio-temporal characteristics of the urban population distribution by integrating the distribution of activity spaces related to the daily life of urbanites and the flow of transportation. The purpose of this study is to analyze the population distribution in urban space with daily and weekly time bases using the building database and T-card database in the city of Seoul, which is rich in information on land use and transportation flow. For a time-based analysis that is difficult to grasp by general statistical techniques, a four-dimensional visualization method combining time and space using a Java program is devised. Dynamic visualization in the four-dimensional space and time allows intuitive analysis and makes it possible to understand more effectively the spatio-temporal characteristics of population distribution. For this purpose, buildings are classified into three activity groups: residential, working, and commercial according to their purpose, and the number of passengers traveling to and from each stop site of bus and subway networks in the T-card database for one week is calculated in one-minute increments, Visualizing these and integrating transportation and land use, we analyze spatio-temporal characteristics of the population distribution in Seoul. As a result, it is found that the population distribution of Seoul displays distinct spatio-temporal characteristics according to land use. In particular, there is a clear difference in the population distribution pattern along the time axis according to the mixed aspects of working, commercial, and residential activities. The results of this study can be very useful for transportation and location planning of city facilities.

• Journal of Soil and Groundwater Environment
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• v.7 no.4
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• pp.31-39
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• 2002

Pollutants from industry, mining, agriculture, and other sources have contaminated sediments in many surface water bodies. Sediment contamination poses a severe threat to human health and environment because many toxic contaminants that are barely detectable in the water column can accumulate in sediments at much higher levels. The purpose of this study was to make optimal treatment and disposal plan o( sediment for water quality improvement in small-scale resevoir based on an evaluation of degree of contamination. The degree of contamination were investigated for 23 samples of 9 site at different depth of sediment in small-scale J river. Results for analysis of contaminated sediments were observed that copper concentration of 4 samples were higher than the regulation of hazardous waste (3 mg/L) and that of all samples were exceeded soil pollution warning levels for agricultural areas. Lead and mercury concentration of all samples were detected below both regulations. Necessary of sediment dredge was evaluated for organic matter and nutrient through standard levels of Paldang lake and the lower Han river in Korea and Tokyo bay and Yokohama bay in Japan. The degree of contamination for organic matter and nutrient was not serious. Compared standard levels of Japan, America, and Canada for heavy metal, contaminated sediment was concluded as lowest effect level or limit of tolerance level because standard levels of America and Canada was established worst effect of benthic organisms. The optimal treatment method of sediment contained heavy metal was cement-based solidification/stabilization to prevent heavy metal leaching.

• Korean Journal of Food Science and Technology
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• v.36 no.6
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• pp.893-899
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• 2004

Method for sample preparation and quantitative analysis of 19 permitted and non-permitted synthetic colors in foods was developed based on reversed-phase ion-pairing high performance liquid chromatography. For color extraction of samples, deionized water was added, and pH was appropriately adjusted with 1% ammonia water. Any undissolved matters were extracted with 50% ethanol or 70% methanol. Lipid in snacks was first removed using n-hexane with centrifugation, water was added to extract colors, followed by clean-up and concentration using Sep-Pak $C_{18}$ cartridge. Recovery efficiencies at known concentrations of 19 standard food colors spiked into foods were in 90.3-97.9% range far soft drink, 79.2-101.9% for candy, 84.1-103.4% for jelly, 86.4-100.8% for chewing gum, 83.5-103.4% for ice cream, and 78.5-95.6% for snack.

• Korean journal of food and cookery science
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• v.15 no.6
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• pp.555-564
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• 1999

The objective of this study was to investigate the preference of root vegetables and the inhibitory effect of the vegetables on harmful enzymes of intestinal bacteria. Two hundred fifty respondents in Seoul area surveyed to obtain information from Sep. 30 to Oct. 30, 1998. Respondents preferred Inpuomoea batatas (sweet potato, 4.05), Solanum tuberosum(potato, 3.97), Allium cepa(onion, 3.68), Codonopsis lanceolata(3.64) and Raponus sativus(redish, 3.60). The growth of B. breve K-110 was effectively increased by adding 0.5% extract of Solanum tuberosum(139%), Codonopsis lamceolate(145%), Dioscorea japonica(164%), Colocisia antiquorum(144%) extract to the medium. B. breve K-100 for beneficial bacteria, and E. coli HGU-3 or Bacteroides JY-6 for harmful bacteria were used to determine the inhibitory effect of root vegetables on harmful intestinal enzymes after co-culturing harmful and beneficial bacteria. The extract of Solanum tuberosum, Codonopsis lanceolata, Dioscorea japonica (yam) and Colocisia antiquorum (taroes) showed inhibitory effect on ${\beta}$-glucuronidase and tryptophanase of intestinal bacteria. The macromolecules were isolated from Solanum tuberosum, Codonopsis lanceolata, Dioscorea japonica and Colocisia antiquorum by Sephadex G-100 column chromatography. By adding these isolated marcromolecules to the medium, the growth of B. breve K-100 were also increased and high inhibitory effects on the ${\beta}$-glucuronidase and tryptophanase were measured. These results suggested that the harmful enzymes of intestinal bacteria were inhibited by consuming Solanum tuberosum, Codonopsis lanceolata, Dioscorea japonica and Colocisia antiquorum. Therefore, they could prevent gastrointestinal diseases.