• Journal of the Korea Institute of Building Construction
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• v.22 no.5
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• pp.425-430
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• 2022

Concrete used for the foundation of high-rise buildings is often placed through in an integrated pouring to ensure construction efficiency and quality. However, if concrete is placed integrally, there is a high risk of temperature cracking during the hydration reaction, and it is necessary to determine the optimal mixing design of high-performance, high-durable concrete through the replacement of the admixture. In this study, experiments on salt damage, carbonation, and sulfate were conducted on the specimen manufactured from the optimal high-performance low-heating concrete combination determined in the author's previous study. The resistance of the cement matrix to chlorine ion diffusion coefficient, carbonation coefficient, and sulfate was quantitatively evaluated. In the terms of compression strength, it was measured as 141% compared to the structural design standard of KCI at 91 days. Excellent durability was expressed in carbonation and chlorine ion diffusivity performance evaluation. In particular, the chlorine ion diffusion coefficient, which should be considered the most strictly in the marine environment, was measured at a value of 4.09×E-12m²/y(1.2898×E-10m²/s), and is expected to be used as a material property value in salt damage durability analysis. These results confirmed that the latent hydroponics were due to mixing of the admixture and high resistance was due to the pozzolane reaction.

• The Journal of Engineering Geology
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• v.26 no.2
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• pp.207-221
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• 2016

As greater numbers of fill dams and reservoirs become old, the risks of damage or embankment collapse increases. However, few studies have considered the deterioration and hazard classification of the internal core layers of fill dams. This study reports the results of geotechnical investigations of 13 earth-cored fill dams in Korea, based on no-water borehole drilling, Standard Penetration Test, and 2D and 3D electrical resistivity surveys along with in situ and laboratory testing. High-capacity no-water boring minimized core layer disturbance while providing continuous core sample recovery. The results allow the classification of potential hazards related to the existing core layers based on both visual inspection of the recovered samples and the results of engineering surveys and tests. Four types of potential hazard are classified: locally fluidized core with a high water content, rapid water inflow to a borehole, cores with granular materials, and relatively low stiffness of core. Among these, the locally fluidized core is the most critical hazard that requires remedial action because it is related to the potential internal flow path and internal erosion. The other three hazard types are of medium importance and require careful monitoring and regular inspection. Of note, there was no correlation between age and core deterioration. The results are expected to aid the safe management and potential upgrading of aging cored fill dams.

• Polymer(Korea)
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• v.25 no.4
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• pp.558-567
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• 2001

The syntheses of thermal latent catalysts have been carried out by modifying the substituent of pyrazinium salts. The thermal latent properties and cure behaviors of difunctional epoxy resin (diglycidylether of bisphenol-A, DGEBA) with 1 wt% of catalyst as an initiator were investigated by dynamic DSC method. As a result, the synthesized catalysts showed the good latent thermal properties in epoxy system. With increasing the basicity of substituted catalyst, the cure temperature and activation energy of epoxy system were increased, whereas the activity was decreased. This was probably due to the fact that the activity and cure behavior were controlled by ring strain and basicity of substituent. Consequently, the catalyst activity modified by methyl group as an electron donor was decreased in increasing of basicity in an initiation step of epoxy cure system. This is due to a decreasing of stabilities of both leaving group of pyrazinium salts and benzyl cation. However, the catalyst activity modified by cyano group as an electron acceptor was increased in increasing the stability of benzyl cation resulting from organic effects and resonance.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.11-22
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• 2014

The buffer capacity of food waste lowers during the collecting and transportation period. Food waste usually shows deficiency of micro nutrients especially molybdenum(Mo) and cobalt(Co). Therefore, food waste can be considered as a good mixture of livestock waste to enhance methane production. The objective of this study was to investigate the correlation between properties of substrates (local food waste and livestock manure) and methane yields for successive anaerobic fermentation process and its stable management. Food wastes were taken at an intermediate storage or treatment system provided by eight local authorities (Gangnam, Gangdong, Gwanak, Guro, Dongjak, Songpa, Yeongdeungpo, and Younsan) in Seoul. The solid content and potential methane yield of food wastes were average of 16% and $446.6STP-m{\ell}/g-VS$ (range from 334.8 to $567.5STP-m{\ell}/g-VS$) respectively. As for the beef cattle manure, the solid content and potential methane yield had an average of 26% and $280.6STP-m{\ell}/g-VS$ respectively. Potential methane yield had a positive correlation with fat content, and hydrogen content and a negative correlation with carbohydrate content ($r^2>0.8$). Therefore, the potential methane yield can be predicted based on the substrate characterization results with reasonable accuracy. Further research may be needed to investigate the relation of the properties of the mixture substrate and methane production rate. The mixtures may include food waste, livestock waste, and bulking agents (saw dust, rice hull, or agricultural byproducts etc.) to determine best combination of these substrates for maximum methane production rate.

• Journal of Life Science
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• v.18 no.10
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• pp.1390-1394
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• 2008

Previously, we found that the transgenic rice plants over-expressing the Arabidopsis $H^+/Ca^{2+}$ antiporter CAX 1 (accession no. U57411) gene accumulated 2.7 to 7.5-fold more calcium in the T3 rice grains as compared to those of control. To examine physiological safety of the $T_3$ rice grains, the effect of the $T_3$ brown rice on change in levels of body weight and white blood cells was compared with that of the control Ilpum brown rice by feeding trial in mice. During the feeding trial for one month, there was no significant difference between two mice groups, which were fed by the $T_3$ brown rice or Ilpum brown rice. There were no detectable differences in their effects on immune functions including plaque-forming unit, peritoneal macrophage number, and NK-cell activity. In addition, biochemical analysis of the blood failed to exhibit any difference between two mice groups. Together, these results suggested that the $T_3$ brown rice, which was produced from a genetically modified organism (GMO), might be safe and possess a potential to be applicable as calcium-fortified feed or food. Long-term safety of the $T_3$ brown rice, however, remains to be elucidated.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.38-46
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• 2005

This study was carried out to quantify the rates of anaerobic mineralization and sulfate reduction, and to discuss the potential effects of benthic fauna on sulfate reduction in total anaerobic carbon respiration in Ganghwa intertidal flat in Korea. Anaerobic carbon mineralization rates ranged from 26 to 85 mmol $C\;m^{-2}\;d^{-1}$, which accounted for approximately 46 tons of daily organic matter mineralization in the intertidal flat of southern part of the Ganghwa Island (approximately $90\;km^2$). Sulfate reduction ranged from 22.6 to 533.4 nmol $cm^{-3}\;d^{-1}$, and were responsible for $31{\sim}129%$ of total anaerobic carbon oxidation, which indicated that sulfate reduction was a dominant pathway for anaerobic carbon oxidation in the study area. On the other hand, the partitioning of sulfate reduction in anaerobic carbon mineralization in October decreased, whereas concentrations of Fe(II) in the pore water increased. The results implied that the re-oxidation of Fe(II) in the sediments is stimulated by macrobenthic activity, leading to an increased supply of reactive Fe(II), and thereby increasing Fe(III) reduction to depress sulfate reduction during carbon oxidation.

• Proceedings of the Korea Association of Information Systems Conference
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• 1998.10a
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• pp.20-30
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• 1998

고도화된 정보통신의 확산으로 인해 인터넷(internet)을 통한 지역간의 거리를 극복 한 전자상거래가 점점 발달하고 있으며 이에 따른 시장의 잠재성 또한 커지고 있다. 그러나 현재 구축된 인터넷 쇼핑몰도 그 규모나 숫자에 비해서 매출액은 아직 높은 편이 아니다. 이에 대한 많은 이유가 있겠지만 가장 큰 이유중의 하나가 구매자 수의 부족을 들을 수 있 다. 이에 본 연구에서는 인터넷 쇼핑몰에 방문한 고객이 기꺼이 구매할 수 있는 환경을 제 공해 주기 위해 '지능형 메타몰(Intelligent Meta-Mall)'을 제안하고, 인터넷 쇼핑몰 중에서 사용자가 직접 마주치는 부분인 프론트 오피스(Front Office) 부분에서 제공되어야 하는 기 능 37가지를 제안하였다. 그리고 이들 기능을 일반관리 기능 및 소비자 구매과정 모형에 따 라 분류한 후, 현재 국내에서 운영되고 있는 쇼핑 몰의 웹마스터에게 설문조사를 실시함으 로써 상대적으로 중요한 기능과 불필요한 기능들을 파악하였다. 상대적으로 중요한 기능은 (1) One-stop Shopping 기능, (2) 비교쇼핑기능, (3) 단어(keyword) 탐색 기능, (4) 보안 모니터링 기능, (5) 부도 보증 기능, (6) 반품 관리 기능, (7) 속달 기능, (8) One-stop Payment 등으로 조사되었다. 상대적으로 불필요한 기능은 (1) 경매제품 탐색 기능, (2) 인 터페이스 수정 기능, (3) 사이버 머니 제공 기능, (4) 신원확인 기능, (5) No Blank 페이지 제공 기능, (6) 기본 사양 여과(filtering) 기능, (7) 다국어 지원 기능, (8) 보안 모니터링 기 능 등으로 조사되었다.

• Journal of Life Science
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• v.29 no.2
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• pp.231-238
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• 2019

This study evaluated the antioxidant activity of the extract and fractions of Alnus firma. Alnus firma had the highest total phenolic content ($452.80{\pm}7.01{\mu}g$ gallic acid equivalents/mg) in a methanol (MeOH) fraction and the highest total flavonoid content ($112.29{\pm}11.14{\mu}g$ rutin equivalents/mg) and antioxidant capacity ($936.23{\pm}0.07{\mu}g$ ${\alpha}$-tocopherol equivalents/mg) in an ethylacetate (EA) fraction. The antioxidant activities of various solvent extract fractions of Alnus firma were evaluated using various antioxidant assays, including ${\beta}$-carotene-linoleate assay, reducing power assay, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, metal chelating activity assay, superoxide anion radical scavenging assay, and lipid peroxidation inhibition assay using the ferric thiocyanate method. These activities were compared with those of ascorbic acid, butylated hydroxyanisole (BHA), gallic acid (GA), butylated hydroxytoluene (BHT), and ${\alpha}$-tocopherol. First, at a $250{\mu}g/ml$ concentration, the EA and MeOH fractions of A. firma showed 92.43% and 89.20% DPPH radical scavenging activity, respectively. Second, $50{\mu}g/ml$ of the EA fraction exhibited 72.49% superoxide anion radical scavenging activity, a little greater than the same dose of GA (60.88%). Finally, 0.5 and 1 mg/ml of the EA fraction showed 73.45% and 73.29% inhibition of peroxidation in the ${\beta}$-carotene-linoleic acid system, respectively. The decreasing order of reducing power was EA fraction > n-butanol (BuOH) fraction > dichloromethane (DCM) fraction > n-hexane (HX) fraction. The results obtained in the present study indicated that Alnus firma can be used as an easily accessible potential source of natural antioxidants.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.1
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• pp.110-115
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• 2012

Various unripe peach (Prunus persica L. Batsch) seeds, which were picked on late May, were subjected to 80% methanol extracts to investigate the antioxidant activities, whitening effects, and anti-wrinkle activities. The yield of 6 cultivars (Takinosawa Gold, Kawanakawase Hakuto, Madoka, Yumefuji, Nagasawa Hakuho, and Hong Bak) from unripe peaches were the highest on Yumefuji, followed by Madoka, Kawanakawase Hakuto, Takinosawa Gold, Hong Bak, and Nagasawa Hakuho (6.16%, 6.08%, 5.65%, 5.25%, 5.23%, and 5.20%). The content of the total polyphenol of seed extracts ranged from 18.33 to 27.08 mg/g. The antioxidant in vitro assays including the DPPH and ABTS radical scavenging activities were the highest with Hong Bak and Kawanakawase Hakuto. The tyrosinase inhibition activity greatly affected the Takinosawa Gold and Kawanakawase Hakuto. Compared to the elastase inhibition activity of 6 cultivars, Madoka was higher than others, while the lowest was Hong Bak. The significant correlation coefficient values were determined (more than p=0.05) between the yield, total polyphenol content, antioxidant activities, tyrosinase inhibition, and elastase inhibition activities. The results suggested that the total polyphenol content has a high positive value on the DPPH, ABTS radical scavenging activity, and tyrosinase inhibition activity. Also, the tyrosinase inhibition activity and elastase inhibition activity showed a significant correlation (r=+0.594). The ABTS inhibition activity and tyrosinase inhibition activity that is the most suitable character represented significant positive correlation (r=+0.846). This data suggested that the methanol extracts from these unripe peaches could be potential candidates for natural cosmetics.

• Food Science and Preservation
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• v.22 no.1
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• pp.12-18
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• 2015

The objective of this research was to investigate the antioxidant and antimicrobial activities of muscadine grape extracts. Three different cultivars of muscadine grapes including Higgings, Jumbo, and Noble were selected. The skin/pulp and seed parts of three selected muscadine grape cultivars were used for extraction. The total phenolic contents of muscadine grape extracts were expressed as gallic acid equivalents (GAE). The antioxidant activity of muscadine grape extracts were determined by scavenging activity of diphenylpicrylhydrazyl (DPPH) radical and expressed as effective concentration ($EC_{50}$), which represented the concentration of the extract exhibiting 50% DPPH radical scavenging. The antimicrobial activity against E. coli K12 was determined and expressed as the minimum inhibition concentration (MIC). The seed extracts exhibited greater total phenolic contents than the skin/pulp extracts, ranging from 231.24 to 294.81 mg/mL GAE. The seed extracts exhibited greater antioxidant activities than the skin/pulp extracts ($EC_{50}$ of Higgins seed extract=0.026 mg/mL). However, the skin/pulp extracts exhibited greater antimicrobial activities than the seed extracts, exhibiting the minimum inhibition concentration (MIC) in Higgins skin/pulp extract (MIC=4.0 mg/mL). This research indicated that the seed part and skin/pulp parts of the muscadine grapes possessed antioxidant activity and antimicrobial activity, respectively. Therefore, it was concluded that muscadine grapes possess the potential to be utilized as functional foods or nutraceuticals.