• Journal of Korean Academy of Oral Health
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• 제41권4호
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• pp.296-302
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• 2017

Objectives: The water fluoridation program has been implemented since 2008, in a region of Geoje City. This study aimed to evaluate the effectiveness of the water fluoridation program on caries prevention in the permanent dentition. Methods: Evaluation surveys were conducted on 8-, 10- and 12-year-old children in the fluoridated and non-fluoridated regions of Geoje City, in 2015. The survey included 834 children from the fluoridated regions and 703 from the non-fluoridated regions. The data obtained from the survey were analyzed using the IBM SPSS statistical package version 23.0. The effectiveness of community water fluoridation in caries prevention was estimated by the differences in the decayed, missing, filled teeth (DMFT) and decayed, missing, filled surfaces (DMFS) scores, between the program and control groups. The mean numbers of fissure-sealed teeth and surfaces were adjusted to reduce their confounding effect. Results: The mean DMFT and DMFS scores (0.69 and 0.91, respectively) of 10-year-olds from the fluoridated regions, after adjusting for the numbers of fissure-sealed teeth and surfaces, were significantly lower than those of the 10 year olds (DMFT: 0.95, DMFS: 1.32) from the non-fluoridated regions. The effectiveness of water fluoridation on caries prevention in the permanent dentition, estimated based on the differences in the mean DMFT and DMFS scores, adjusted for the number of fissure-sealed teeth and surfaces, between the program and control groups of 10-year-old children, was 27.4% and 31.1%, respectively. Conclusions: These results suggest that the effectiveness of water fluoridation on caries prevention in the permanent dentition, in Geoje City was so high that this program should be implemented in other regions in Korea as well.

• 한국물환경학회지
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• 제22권5호
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• pp.887-894
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• 2006

Water quality in the Daecheong reservoir has been deteriorated by algal bloom every year. Algal bloom is propagated from eutrophicated tributary into the main body of the reservoir during the wet season. Nutrients from diffuse sources trigger the propagation of the algal bloom. This study is aimed to analyze relationship between the water current by the simulation and algae transport from the main body in the Daecheong reservoir including tributary where algal bloom has occurred seriously every year. Water quality model CE-QUAL-W2 was applied to analyze water movement in draught season (2001) and flooding season (2003). The result of simulation corresponded with the observed water elevation level, 63~80 m and showed stratification of the Daecheong reservoir. In the draught season, as velocity and direction off low in the reservoir was estimated to affect algae transport including nutrient supply from small tributary, algal blooms occurred in the stagnate zone of middle stream of the reservoir. On the other hand, in the flooding season, it was resulted in nutrient transport from upstream of main reservoir and nutrients were delivered up to downstream by fast water velocity. In result, algal blooms occurred in stagnate zone of reservoir downstream as the current of downstream was retarded according to dam outflow control.

• 한국농공학회논문집
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• 제55권6호
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• pp.113-120
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• 2013

Miscanthus is one of the promising energy crops for producing bioethanol or bioenergy in many countries. A field of about 180 ha for miscanthus plantation was started for demonstration near Geum River in 2011. Since the size of the field is much larger than those of traditional cultivation for one single crop in this country, questions were raised if there are any environmental impacts from the energy crop plantation, particularly on water quality. In this study, water quality of runoff water from three different plots was analyzed for assessing the impacts of energy crop production. The results showed that there were no substantial differences among the plots; control, the first, and the second year growth fields. The concentrations of COD, T-N, and T-P were lower than those in runoff water from agricultural crop fields. The second year field showed a slight higher values of COD and T-N concentrations due to the biodegradation of residue of miscanthus which was not cultivated for observation. Commercial planation of miscanthus in a large scale would not result in a water quality problem when avoiding application of fertilizer as practiced in agricultural crop fields.

• 한국물환경학회지
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• 제27권5호
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• pp.710-718
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• 2011

An integrated water quality management of reservoir and river would be required when the quality of downstream river water is affected by the discharge of upstream dam. In particular, for the control of downstream turbidity during flood events, the integrated modeling of reservoir and river is effective approach. This work was aimed to develop a laterally-averaged two-dimensional hydrodynamic and water quality model (CE-QUAL-W2), by which water quality can be predicted in the downstream of Yongdam dam in conjunction with the reservoir model, and to validate the model under two different hydrological conditions; wet year (2005) and drought year (2010). The model results clearly showed that the simulated data regarding water elevation and suspended solid (SS) concentration are well corresponded with the measured data. In addition, the variation of SS concentration as a function of time was effectively simulated along the river stations with the developed model. Consequently, the developed model can be effectively applied for the integrated water quality management of Yongdam dam and downstream river.

• 한국막학회:학술대회논문집
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• 한국막학회 1997년도 심포지움시리즈 Jan-97 수처리용 분리막 기술 및 응용
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• pp.55-62
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• 1997

In Japan, the membrane filtration is becoming a common technology for municipal water supply system especially for small plant. 6 years before (1991), the national research project of membrane filtration for small plant has started. The project was named as "MAC 21", MEMBRANE AQUA CENTURY 21. In the project the Ministry of Health and Welfare, 8 universities and 18 water treatment plant companies have been involved. This was the first attempt to research a common theme in joint with government, universities and private companies. After three years, the guide line for membrane filtration application for small plant has been established. This has promoted to install some actual plant. And also, another joint research for "RESEARCH OF MEMBRANE FILTRATION FOR ADVANCED WATER TREATMENT" has started in 1994 and completed in March, 1997. The project was named as MAC21. In the former project the main objectives were removal of turbidity and bacteria from water. However, in new project the objective was establishment of the further advanced membrane filtration technology which would be applicable for trace chemical components removal such as tri-halo-methane pre-courser, agricultural chemicals removal, offensive smell and taste removal and virus removal. For the objectives, application of nanofiltration and hybrid-system, a combination of micro-filtration ultra-filtration with biological, ozone and activated carbon treatment process have been studied. In addition, application of membrane filtration for treatment of back-wash waste water originated from membrane filters and conventional sand filters has.been studied. At the end of March of this year, about 30 membrane filtration plants are actually supplying the water, the total treatment capacity is about 6,000 m$^{3}$/day and another 20 will be installed within one year.led within one year.

• 한국농공학회논문집
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• 제61권5호
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• pp.1-10
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• 2019

Due to the climate change the drought had been occurring more frequently in recent two decades as compared to the previous years. The change in the pattern and frequency of the rainfall have a direct effect on the farming sector; therefore, the quantitative estimation of water supply is necessary for efficient agricultural water reservoir management. In past researches, there had been several studies conducted in estimation and evaluation of water supply based on the irrigational water requirement. However, some researches had shown significant differences between the theoretical and observed data based on this requirement. Thus, this study aims to propose an approach in estimating reservoir rate based on empirical method that utilized observed reservoir rate data. The result of these two methods in comparison with the previous one is seen to be more fitted for both R2 and RMSE with the observed reservoir rate. Among these procedures, the method that considers the drought year data shows more fitted outcomes. In addition, this new method was verified using 15-year (2002 to 2006) linear regression equation and then compare the preceeding 3-year (1999 to 2001) data to the theoretical method. The result using linear regression equation is also perceived to be more closely fitted to the observed reservoir rate data than the one based on theoretical irrigation water requirement. The new method developed in this research can therefore be used to provide more suitable supply data, and can contribute to effectively managing the reservoir operation in the country.

• 동굴
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• 제65호
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• pp.39-51
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• 2004

To introduce the typical water caves of the northeastern district in China, the Shenyang Water Cave located in the Shenyang city and the Benxi Water Cave located in the Benxi city of the Liaoning province of the northeastern part of China are presented. The caves are very big and long, and the water flows in the cave to drive the motor boat for tourist watching the beautiful sight in the caves through the year. The geological information and the beautiful internal sight of views in the caves are introduced.

• 물과 미래
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• 제14권3호
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• pp.47-54
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• 1981

우리나라의 주요 도시 서울, 부산, 대구, 광주의 지점강우량에 대하여 확률적인 방법과 M년 최대치법에 의하여 그 특성이 해석되었으며 일본의 해석결과와도 비교되었다. 본 연구에서 얻어진 결과는 다음과 같다. T년확률강우가 N년 동안에 발생하지 않은 확률은 관측치로부터 분석된 값과 비교하여 볼 때 이론치보다 작았으며 일본의 결과보다는 컸다. M년 10분 최대치가 N년 동안에 발생하지 않은 확률의 평균치는 이론치보다 컸으며 M년 1시간 최대치는 이론치보다 작았고 M년 1일 최대치는 이론치와 거의 일치했으며 일본의 경우는 이론치보다 작았다. 상기 결과에 의하여 확률적인 면에서 본다면 M년 최대강우를 설계량으로 택하는 것이 T년 확률강우보다 안전측이라고 생각된다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.385-388
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• 2002

We investigated net outflow load and unit load of pollutants from a paddy fields area in dry year 2001. Amount of irrigation water in 2001 was about 61-63% of that in previous years 1999 and 2000 due to drought. The net outflow load and unit load of pollutants in 2001 were negative, showing that paddy fields acts as sink of pollutants due to function of water quality purification. The relationship between unit load of pollutants and net surface outflow (= surface outflow - irrigation water) showed positive correlation. The results showed that abatement of surface outflow by appropriate water management contribute to reduce surface outflow load from paddy fields.

• Journal of Ginseng Research
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• 제20권2호
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• pp.179-183
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• 1996

One exotherm was detected in the intact ginseng seeds containing more than 35% water, but in seeds with 20% there was no exotherm. The shapes of exotherm were remarkably uniform without relation to water content above 35%. The temperature at the initiation of freezing varied from -3.5$^{\circ}C$ to -9.6$^{\circ}C$ with the different water content in the seeds, and the Initial temperature of freezing delayed with the decrease of water content. The resistance damage at low temperature appeared in order of maln body, rhizome, lateral root of 3-year-old yearling rhizome, and fine root of 3-year-old. Ginseng roots didn't receive any damage at -5$^{\circ}C$ for 24 hours. Otherwise they received serious damage below -1$0^{\circ}C$ even for 5 hours'exposure. Hence, alternative low temperature gave more severe damage compared to constant low temperature. This result suggests that the Possibility of receiving injury at low temperature was higher during the thawing season of the early spring than in the winter.