• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.145-153
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• 2013

Recently, accelerated chloride diffusion coefficients are used for an evaluation of chloride behavior. Similar as apparent diffusion coefficients, accelerated diffusion coefficients decrease with time. In this study, decrease in diffusion coefficient with time is simulated with porosity. Utilizing DUCOM-program, porosities from 15 mix proportions are obtained and diffusion coefficients are modelled with regression analysis of porosity for 270 days. Considering non-linear binding capacity which means the relation between free and bound chloride ion, chloride behavior in high performance concrete is evaluated. Through utilizing the previous test results for concrete under chlorides for 180 days, the applicability of the proposed technique is verified. The proposed technique is evaluated to reasonably predict the chloride behavior in concrete with various w/c (water to cement) ratios and mineral admixtures (GGBFS and FA). It is also shown that decrease in chloride diffusion should be considered for chloride prediction in concrete with mineral admixture since it has very clear decrease in diffusivity with time.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.205-211
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• 2006

The objective of this study was to evaluate the durability of low shrinkage high performance concrete(LSHPC), which was combined with expansive additives and shrinkage reducing admixtures. We tested for not only LSHPC but also high performance concrete(HPC) and normal concrete(NC) to be compared with the durability of LSHPC. HPC was made in the same water-binder ratio of LSHPC without expansive additives and shrinkage reducing admixture. As a result, it was found that LSHPC had higher compressive and tensile strength than that of HPC. LSHPC showed more excellent performance than HPC and NC in the case of resistance to chloride ion penetration and resistance to carbonation and also showed nearly 100 durability factor in the freeze-thawing test with 500 cycles. From the examination about the watertightness and the pore distribution, it was found that the durability of LSHPC was improved because its hardened cement paste is organized closer. So we can conclude that when LSHPC is applied to structures in field, it is possible to reduce the shrinkage and crack in concrete and improve the durability.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1333-1337
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• 2005

본 연구는 강우로 인한 도시 배수구역에서의 유출량 및 수질을 예측하기 위하여 영산강 유역의 도시하천이며 합류식 배수계통을 갖는 용봉천을 대상으로 SWMM 모형을 적용하였다. SWMM 모형의 매개변수 최적화 및 검증자료로 사용하기 위하여 강우시 2회에 걸쳐 조사하였으며, 매회 시료 채취 주기는 강우유출이 발생하기 전부터 시작하여 첨두유출량이 발생때까지 $1\~2$시간 간격으로 채취한 후 강우 종료 후 유출량 변화가 없을 때까지 $9\~12$단계로 세분하여 유출량과 pH, DO, BOD, COD, SS, T-N, T-P의 농도를 측정하였다. 모형의 입력자료는 국립지리원의 지형도, 환경부의 환경지리정보, 농업과학기술원의 정밀토양도 등을 기초로 각 배수구역의 소유역을 분할하여 물리학적$\cdot$수리학적 매개변수에 해당하는 입력자료를 산출하였으며 그림1과 같다. 모형의 보정자료는 2004년 6월 17일에 실측한 자료를 이용하여 침투능 계수 및 축적계수와 지수, 쓸림계수를 보정하였고, 검증자료로는 2004년 7월 7일에 실측한 자료를 이용하여 검증자료로 사용하였다. SWMM 모델을 적용해서 강우유출에 의한 hydrograph와 pollutograph를 도출하여 부하량을 산정 하였다.

• Clinical and Experimental Reproductive Medicine
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• v.16 no.1
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• pp.15-21
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• 1989

An in vitro fertilization assay employing zona-free hamster embryos was used to investigate human spermatozoal fertilitzing ability. Yanaghimarchi et al.(1976) first introduced this cross species fertilzation technique, with its application as a diagnostic tool for male infertility. Human spermatozoa were preincubated for 3 to 4 hrs in B W W medium at concentration of $4{\times}10^6$ sperm/ml prior to the addition to zona-free hamster embryos. After 3 hrs, human sperm was evaluated for fertilizing potential by the presence of swelling or decondencing sperm head in the cytoplasm. The results of penetration rates for sperm were as follow : 1. The average penetration rate of a 7 fertile donor group was $47.8{\pm}27.67%$(Range 14.3-98.0%) 2. The average penetration rate of 12 infertile patients with normal semen analysis was $21.7{\pm}26.9%$(Range 0-38.8%) 3. The average penetration rate of 10 infertile patients with semen abnormalities was $6.1{\pm}8.1%$(Range 0-25%)

• Environmental Analysis Health and Toxicology
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• v.19 no.2
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• pp.177-182
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• 2004

Alcohol consumption and exposure to endocrine disruptors and industrial solvents have been implicated in impaired spermatogenesis, increase in the incidence of malformed sperm and decrease in the percentage of moving sperm. The aim of this study was to determine and compare the direct effects of some organic solvents(bisphenol A; BPA, dibutyl phthalate; DBP, formaldehyde; HCHO, dimethylsulphoxide; DMSO, ethanol) on mucus penetration distance, motility and survival rate of human sperm in vitro. Semen samples from 3 health subjects were prepared using swim-up method and 0.0005-0.5% organic solvents were added to the test medium. BPA, DBP, HCHO and DMSO produced significant decreases in the motility and survival rate with a different potency. The most potent inhibition of mucus penetration distance, motility and survival rate was observed after exposure to HCHO. A concentration of 0.0005% HCHO significantly inhibited sperm motility. When ethanol m.: added directly to sperm, at concentrations equivalent to that in serum after heavy drinking, these damaging effects were lowest compared with other solvents. Present study shows that each compound has different toxic potency to human sperm and we need special caution for the use of HCHO.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.408-408
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• 2011

수자원관리와 수문모형에 있어 강수, 증발산, 침투, 침루 등의 물 순환과정에 대한 실질적인 이해와 분석연구의 중요도가 높아지고 있는 실정이며, 그중에서도 토양수분은 강수의 침투, 유출 등의 지표면과 대기사이의 질량 및 에너지이동에 관여하는 중요한 요소로서 수자원 및 수문현상에 직접적인 영향을 미친다. 이를 위해 강수, 증발산, 토양수분과 같은 수문변수에 대한 다양한 관측이 실시되어야 하지만 국내에서는 지속적이고 안정적으로 지상관측을 할 수 없는 실정이며 관련 기반기술도 매우 취약하다. 따라서 이를 극복하기 위해서는 위성영상자료를 이용함으로써 한반도 전체에 대한 광역적인 토양수분자료의 획득을 용이하게 한다. 본 연구의 연구유역은 수자원 연구를 위해서 지정된 용담댐 시험유역으로 하였으며, 토양수분 관측지점의 지상관측 수문자료인 각 지점별 강수량, 지면온도, 인공위성자료인 MODIS 정규식생지수 등의 가용자료를 수집하고 신경망모형을 활용한 토양수분자료 생산 모형을 개발하여, 개선된 시공간 분해능과 공간정보 대표성을 가진 광역 토양수분자료를 생산하고 적용타당성을 분석하였다. 산정된 토양수분모형의 적용가능성을 파악하고자 용담댐 유역의 각 지점별 토양수분 관측데이터와 추정데이터를 비교한 결과 추천, 부귀, 상정 지점의 경우 평균 약 0.9257의 상관계수와 약 1.2917의 평균제곱근오차를 보였고, 검증지점인 천천2의 경우 약 0.8982의 상관계수와 약 5.1361의 평균제곱근오차의 결과를 보여주었으며 토양수분 추정모형의 적용가능성이 높음을 확인할 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1167-1172
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• 2004

Recently, runoff characteristics of urban area are changing because of the increase of impervious area by rapid increasing of population and industrialization, urbanization. It needs to extract the accurate topological and hydrological parameters of watersheds in order to manage water resource efficiently. In this paper, rainfall-runoff analysis in An-Yang stream basin was made using GIS(Geographic Information System) and XP-SWMM(Export Stormwater and Wastewater Management Model). The basin was divided into 13 sub-basins using GIS. The area, slope, width of each subcatchment and length, slop of each stream reach were acquired from topographic maps, and imperviousness rate, land use types, infiltration capacities of each subcatchment from land use maps and soil maps using GIS. We gave th runoff management method of urbanization area us ing XP-SWMM.

• Restorative Dentistry and Endodontics
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• v.27 no.3
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• pp.290-298
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• 2002

3차원적으로 잘 충전된 근관은 치근단 누출과 재감염을 방지하며, 조직이 잘 치유될 수 있는 생물학적 환경을 제공해준다. 이 때문에 근관계의 완전한 충전은 근관치료의 중요한 목표 중의 하나이다. 본 연구의 목적은 4가지 방법으로 근관충전 후 디지털 방사선 사진을 촬영하여 근관충전의 질을 평가하고 투명표본을 제작하여 색소침투범위를 측정함으로써, 근관충전방법에 따른 치근단부 폐쇄능을 비교 평가하고자 하는 것이다. 직선형의 단근관을 갖는 80개의 전치를 선택하여 ProFile$^{\circledR}$ 니켈-티타늄 회전식 기구를 사용하여 근관을 성형한 후 무작위로 20개씩 4군으로 나누었다. 사용된 근관충전법은 다음과 같다：MicroSeal$^{\circledR}$(Group A), Thermafil$^{\circledR}$(Group B), Continuous wave 충전법(Group C), 측방가압충전법(Group D), 각 군에서 10개 치아는 Sealapex를, 나머지 10개 치아는 AH26$^{\circledR}$을 충전용 시멘트로 사용하였다. 근관충전이 끝난 치아는 충전의 질과 길이를 평가하기 위해, 근원심과 협설방향으로 디지털 방사선 사진을 이용하여 촬영하였다. 각 치아의 치근단부 2mm를 제외한 나머지 부위는 두겹의 nail varnish를 바르고, 2% methlylene blue용액에 48시간동안 침잠시켰다. 흐르는 물에 깨끗이 세척한 후, 투명치아를 만들었다. 선상의 색소침투를 관찰하고 치관측 최대깊이를 입체현미경하에서 40배율로 평가하여 다음과 같은 결과를 얻었다. 1. 충전방법에 따른 근단부 폐쇄효과를 비교시, 실험군 모두 비교적 양호한 근단부 폐쇄효과를 보였고 통계학적으로 유의성이 없었다. 2. 충전용 시멘트에 따른 근단부 폐쇄효과를 비교시, AH26$^{\circledR}$을 사용한 군에서 Sealapex를 사용한 군보다 더 적은 색소침 투를 나타냈다(p<0.05). MicroSeal$^{\circledR}$을 이용한 실험 1군내에서 AH26$^{\circledR}$을 사용하였을 때 미세누출이 더 적었고(p<0.05), 다른 군내에서는 통계학적으로 유의성이 없었다. 3. 근단부 충전상태에 따른 미세누출 비교시, 저충전, 과충전과 색소침투간에는 상관관계가 없었다. 4.충전방법에 따른 근단부 충전상태 평가시, Thermafil$^{\circledR}$을 이용한 실험 2군에서 과충전이 많이 나타났다(p<0.05). 이상의 결과로, 기존의 측방가압법 및 여러 열가소성 충전법이 유사한 근단부 폐쇄효과를 나타낸 바, 방법에 따른 술자의 숙련도, 충전시간, 재근관치료의 편이성 등을 고려하여 근관충전방법을 선택하는 것이 합리적일 것이라고 사료된다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.995-1005
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• 2005

The study with laboratory sandbox model has been carried out to address potential use of reclaimed water, as a countermeasure artificially recharging the coastal aquifer, to effectively prevent from seawater intrusion due to overexploitation. It also investigated plausibility for either preserving or recovering the freshwater interface facing with seawater intrusion. To do this, we assessed hydraulic properties in artificial aquifer seawater/freshwater interface) depending upon the variation of extraction, storage and injection of reclaimed water. The variation of interface between freshwater and seawater were visualized by Surfer 8(Golden Software, USA) according to given experimental conditions. The interface between seawater and freshwater has been sensitively influenced by the change of extraction rate, where seawater zone migrated much faster into freshwater zone even though extraction rate became decreased. However, decreasing recharge rate could slow down moving of saline water zone toward freshwater zone. When the recharge was solely introduced into the sand box model, saline water intrusion was retarded than those of recharge and extraction working together. And also, the level of salinity of saline water was diluted by artificial recharge. It finally revealed that the artificial recharge would hydraulically avoid seawater intrusion while the freshwater sources could be conservatively utilized.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.49-55
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• 2018

In this study, we investigated the cellular protective effects and mechanisms of nicotiflorin and its aglycone kaempferol isolated from Annona muricata. The protective effect of these components against $^1O_2$-induced cell damage was also studied by using L-ascorbic acid and (+)-${\alpha}$-tocopherol as controls. Kaempferol exhibited the most potent protective effect, followed by (+)-${\alpha}$-tocopherol and nicotiflorin. L-Ascorbic acid did not exhibit any cellular protective effects. To elucidate the mechanism underlying protective effects, the quenching rate constant of the singlet oxygen, free radical-scavenging activity, ROS-scavenging activity, and uptake ratio of the erythrocyte membrane were measured. The results showed that the cell membrane penetration is a key factor determining the cellular protective effect of kaempferol and its glycoside nicotiflorin. The result from L-ascorbic acid demonstrated that the cellular protective effect of a compound depends on its ability to penetrate the cell membrane and is independent of its antioxidant capacity. In addition, it is suggested that cellular protective effects of kaempferol and (+)-${\alpha}$-tocopherol depend not only on the cell permeability, but also on free radical- and ROS-scavenging activities. These results indicate that the cell permeability and free radical- and ROS- scavenging activities of antioxidants are major factors affecting the protection of cell membranes against the oxidative damage induced by photosensitization reaction.