• 한국물환경학회지
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• 제28권5호
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• pp.754-761
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• 2012

Several drinking water treatment plants (DWTPs) produce the bottled tap waters (BTWs) as pilot production and provide them for noncommercial use. In 2008, acetaldehyde and chloral hydrate were detected in some BTWs and the public worry over the safety of the water. In this study, the BTWs produced from 7 DWTPs were tested for 13 chemicals including disinfection byproducts (DBPs). The level of four trihalomethanes (THMs) were increased up to 15 days. The average concentration of them was 0.0075 mg/L at the time of bottling and it was increased to 0.0214 mg/L after 15 days. The average acetaldehyde concentration was 0.0406 mg/L at the time of bottling but it was went up to 0.2251 mg/L after 11 days and then decreased. Although the initial concentrations of DBPs were below the drinking water standard, we also traced them at different storage conditions. Temperature affected the formations of THMs and acetaldehyde concentrations significantly. While the average concentration of THMs ranged from 0.0113 to 0.0182 mg/L at $25^{\circ}C$, it was increased to 0.0132 ~ 0.0256 mg/L at $50^{\circ}C$. In case of acetaldehyde, concentration ranged from 0.0901 to 0.2251 mg/L at $25^{\circ}C$, it was increased to 0.3394 ~ 1.0591 mg/L at $50^{\circ}C$. Throughout the tests with 7 BTWs samples, none of the chemicals was exceeded the drinking water standard of Korea. Therefore, it is recommended to avoid the exposure of BTWs to sunlight or high temperature during distribution and storage.

• Environmental Analysis Health and Toxicology
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• 제18권3호
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• pp.209-217
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• 2003

To investigate the effects of low dosed microcystin -LR (MCLR) on the initial stage of subacute hepatotoxicity in vivo, male Sprague-Dawley rats after weanling were divided in four groups. The orally treated group (OG) was administered orally by 1 $\mu\textrm{g}$/kg B.W. at an interval of three days. The free group (FG) has taken the drinking water including 1 $\mu\textrm{g}$/L freely and the control group (CC) was only treated with 0.9％ saline solution All groups were treated for a period of 3 weeks. There was a significant correlation in body growth rate between OG and FC and especially, a deterioration of the growth of spleen was observed in the FG after 5 days. The protein levels were also decreased in OG and FG after 9 days. Level of total fat was increased to the 9th day but again decreased up to the initial level. High hemolysis of the isolated erythrocytes occurred only in OG. Activities of ${\gamma}$-G7 of 0G and FG were higher twice-fold than CG, but the values of OG were already higher at the first treatment day. No significant change in aspartate aminotransferase (AST) activity was shown in all groups, but the activity of alanine aminotransferase (ALT) was slightly increased at the beginning state. There were much similarities in the results of OG and FG. except the growth inhibition of spleen in FG. It may be concluded that long -term effects of the low doses of mycrocystins in animals including human being can lead to serious health problems, especially to liver and spleen.

• 한국수소및신에너지학회논문집
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• 제27권6호
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• pp.712-720
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• 2016

When bioethanol and water are mixed at a proper ratio, phase separation can occur because of the immiscibility of biobutanol with water. Phase separation in bioethanol blends fuels is a major problem for gasoline vehicle users due to effect of octane number and component corrosion. Thus, in this study, the phase separation of bioethanol was examined effect of bioethanol blends (E3 (3 vo.% bioethanol in gasoline), E5 and E10) in presence of water. The effect were evaluated behavior with phase separation test, simulation test of fuel tank in gas station according to water addition volume and it was investigated change of water content, bioethanol content and octane number for gasoline phase in bioethanol blends (E3, E5 and E10) every 1 week after water addition. The E3 occurred phase separation more easily than the E5 and E10 in small water contents because solubility of water on ethanol content difference in gasoline-ethanol. It was kept a initial level of water content, bioethanol content, and octane number by repeated sample replacing in simulation test of fuel tank.

• 대한통합의학회지
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• 제4권4호
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• pp.109-117
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• 2016

Purpose : This study was designed to provide basic data of effective sanitization method of sprout vegetable for microbiological safety. Methods : Sanitization treatments were performed by dipping the sprout into chlorine and vinegar water. Microbial analysis were composed of the total plate count(TPC) and coliform group count(CGC). Result : Among chlorine water sanitization, the microbial reduction was largest in 100ppm chlorine water, and its TPC and coliform group count decreased to 6.01 log CFU/g and 5.06 log CFU/g. The effective dipping time in 100ppm chlorine water treatment was 5.97 log CFU/g and 5.91 log CFU/g for 30min and 60min, in which TPC were below the microbiological safety limits of 6.00 log CFU/g. Coliform group counts were decreased to 5.44, 5.46, 5.42 log CFU/g in the dipping the spouts for 30min, 60min and 90min. As a result of sanitizing alfalfa spout by vinegar water, a microbial counts tended to decrease with increasing concentration and the dipping time. The effective concentration of vinegar water was 2% for TPC(6.00 log CFU/g) and 1% for coliform group count(5.20 log CFU/g). With 1% vinegar water treatment, TPC became below the microbiological safety limits in all samples and in particular, the sample treated for 60min and 90min(4.93, 4.54 log CFU/g). While coliform group counts were decreased to 3.91 log CFU/g in the dipping the sprouts for 90min, those were still beyond the permitted limit. Conclusion : To secure the food safety of food service facilities including kindergarten feeding, it is considered that along with the systematic study of effective disinfection method for microbiological control at the preconditioning level of spout vegetable within the range of secured maleficence to human body, and the study regarding the measures to lower the initial microbiological pollution of spout vegetable.

• Geomechanics and Engineering
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• 제13권4호
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• pp.671-683
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• 2017

Groundwater control is a significant issue in most underground construction. An estimate of the inflow rate is required to size the pumping system, and treatment plant facilities for construction planning and cost assessment. An estimate of the excavation-induced drawdown of the initial groundwater level is required to evaluate potential environmental impacts. Analytical and empirical methods used in current engineering practice do not adequately account for the effect of the jointed-rock-mass anisotropy and heterogeneity. The impact of geostructural anisotropy of fractured rocks on tunnel inflows is addressed and the limitations of analytical solutions assuming isotropic hydraulic conductivity are discussed. In this paper the unexcavated Zagros tunnel route has been classified from groundwater flow point of view based on the combination of observed water inflow and numerical modeling results. Results show that, in this hard rock tunnel, flow usually concentrates in some areas, and much of the tunnel is dry. So the remaining unexcavated Zagros tunnel route has been categorized into three categories including high Risk, moderately risk and low risk. Results show that around 60 m of tunnel (3%) length can conduit the large amount of water into tunnel and categorized into high risk zone and about 45% of tunnel route has moderately risk. The reason is that, in this tunnel, most of the water flows in rock fractures and fractures typically occur in a clustered pattern rather than in a regular or random pattern.

• 한국환경과학회지
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• 제21권1호
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• pp.57-67
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• 2012

The midge samples were undertaken at three streams, representing different surrounding environments, to investigate the contaminant exposure of midge. The content of heavy metals in midge collected in Singil stream were generally higher as a result of input to the industrial effluents with respect to other streams. Adsorption experiments were done to evaluate the possibility of removing contaminants from water with midge. Diazinon and heavy metals were contaminant target compounds in this study. The removal rate of diazinon in water by midge was 60-75%. In the case of Cu, the removal rate was reached around 90% at the lower initial concentration of 1.87 and 0.81 ppm rather than 4.25 ppm. The reduction of concentration of Cr and Cd according to the lapse of time was similar to the Cu, but their removal rates were shown 50% and 60-74%, respectively. The removal rate of Zn by midge represented relatively high level within the experimental condition. No change in concentration of Cr and As with time were occurred at all experimental conditions. It accounts for the fact that the reduction of Cr and As could not be achieved through the adsorption process, using midge.

• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.38-47
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• 2017

This paper presents experimental data on water droplet breakup in high-speed air flows. Exact-time-dependent evolution of wave and droplet interaction as well as breakup processes were optically visualized using a shadowgraph technique. Droplet experiments were conducted in a shock tube. Five flow conditions were used with an incident shock wave Mach number from 1.40 to 2.19 with Weber number based on the droplet initial diameter from 2300 to 38000, respectively. This corresponds to post-shock flow speeds varying from subsonic to supersonic. The considered droplet diameters were 2.0 mm to 3.6 mm. Some interesting wave patterns in the near wake were found. The present data shows that with an increase in the Weber number the droplet acceleration coefficient decreases and the level of decrease was weaker for the case of higher Mach numbers. This state of affair is different to the existing data in literature. Possible reasons are discussed.

• 한국농공학회지
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• 제45권3호
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• pp.84-93
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• 2003

Photoreactivation of microorganism following UV-disinfection is one of the research topics of interest in assessing the UV-disinfection performance. Apparent photoreactivation was examined under fluorescent lamp and solar radiation as well as in darkness. Total coliform, fecal coliform, and Escherichia coli were used as indicator microorganisms, and their concentration was monitored with time after UV-disinfection. Under the darkness, their initial concentration of 10∼30 MPN/100 mL increased to the level of 100 MPN/100 mL after 24 hours, which implied that part of damaged microorganisms by UV-disinfection might be repairable with time. Under the fluorescent lamp, photoreactivation was more apparent that their concentration increased up to 1,000 MPN/100 mL which might significantly impair the water uses specially in reuse of reclaimed wastewater. However, their concentration further decreased down to below 2 MPN/100 mL under the solar radiation primarily due to additional disinfection by solar radiation rather than photoreactivation. Samples not disinfected by UV-disinfection also demonstrated substantial decrease of their concentration under solar radiation from about 5,000 MPN/100 mL to less than 30 MPN/100 mL in 24 hours. But direct reuse of effluent without disinfection is not recommended because natural decay by solar radiation may take time and be affected by climatic conditions. The result suggests that photoreactivation of pathogenic microorganisms may not be concerned in agricultural reuse of reclaimed wastewater because solar radiation may provide further disinfection after UV-disinfection.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1029-1037
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• 2008

The finite element analysis of transient water flow through unsaturated soils was used to investigate effects of hydraulic characteristics, initial relative degree of saturation, methods to consider boundary condition, and rainfall intensity and duration on water pressure in slopes. The finite element method with shear strength reduction technique was used to evaluate the stability of slopes under rainfall. The slope-related disasters in Korea usually occur between July and September during the typhoon and localized heavy rain. This means that the rainfall is the most important factor that leads to the slope-related disasters. The slope-related disasters can happen at very short time and lead to big damage. To forecast the change of the heave of the groundwater in slope the Seep/w program was used.

• 농업생명과학연구
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• 제53권1호
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• pp.13-21
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• 2019

배양액의 농도 조건과 품종별 양수분 흡수특성을 구명하여 장기 수경재배를 위한 기초자료를 획득하고자 연구를 수행하였다. 시험 품종으로 토마토 대과종으로는 적색계인 '대프니스'와 도색계인 '수퍼도태랑' 소과종으로는 '미니찰' 품종을 이용하였다. 담액재배하였으며 배양액의 EC를 1.0dS·m-1, 2.0dS·m-1, 3.0dS·m-1, 4.0dS·m-1로 다르게 공급하였다. 배양액의 EC가 높은 처리에서 초기에는 엽면적, 생체중이 감소하였으며 염류장해가 발생하면서 생육(초장, 엽면적, 경경, 생체중)이 불량해졌다. 배양액의 EC가 높을수록 수분흡수가 적었다. 수분흡수량은 1차에서는 품종별 차이가 뚜렷하지 않았으나 2차 조사에서는 '대프니스'가 EC 2.0dS·m-1 이상에서도 수분흡수가 크게 감소하지 않았으나 '수퍼도태랑'은 높은 EC 처리에서 수분 흡수가 감소하였다. 배양액의 EC가 낮은 처리에서 무기이온의 흡수는 N, P, K는 급액농도 보다 높게 흡수된 반면에 Ca, Mg, S는 흡수율이 낮았다. 배양액의 EC가 높은 처리에서는 대부분의 이온이 초기 투입농도의 50% 이하로 흡수되었다. 따라서 EC가 낮은 처리가 높은 처리 보다 흡수되고 남은 배양액의 이온간 불균형이 심하였다. 품종 간에는 '대프니스'가 저농도에서 흡수량이 많고 고농도에서는 흡수량이 적어 불량한 양분조건에서 양분을 효율적으로 이용하는 품종이었으나 과잉 흡수된 양분으로 인한 장해 증상은 가장 심하게 나타내었다.