• Water for future
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• v.19 no.2
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• pp.157-166
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• 1986

The objective of this study was to determine the best representative synthetic unit hydrograph that is applicable to ungaged small watershed. A typical unit hydrograph was established with the actual data from a small watershed. Four currently well-known methods for analyzing ungaged small watershed, including Snyder's, Clark's S.C.S. and Nash methods, were evaluated with the data from the same small watershed. The following observations were noted from the analysis of four methods. The Snyder's method yielded the similar peak discharge value as the typical unit hydrograph. With co-ordinates of three discharge values, i.e. 25%, 50% and 75% of peak discharge, were not adequate for deriving a typical unit hydrograph in ungaged small watershed. With Clark's method there shall be some way of obtaining the exact base length of time area diagram and isochrone of each reach of the stream. With Nash method peak discharge and base flow time are affected by the storage constant and gamma function argument; therefore, for deriving a more reliable and workable unit hydrograph one needs to select for the better estimation of storage constant and gamma function argument. In S.C.S. method peak discharge is directly related to the watershed area and inversely related to the time of peak diacharge. Therefore area with faster peak discharge yielded the higer peak discharge value. Although the peak discharge value obtained frome the S.C.S. method higher than the value obtained from the unit hydrograph developed from the actual data, this method contains a number of advantageous factors. The peak discharge value and the time of peak discharge can be claculated easity from the morphological characteristics of the watershed, and in S.C.S method co-ordinates of the unit hydrograph can be calculated easily from that of the dimensionless unit hydrograph. When the four currently used methods were evaluated with a typical unit hydrograph obtained from the actual data, the S.C.S method was show to be the best method in deriving a synthetic unit hydrograph for ungaged small watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.831-835
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• 2007

금강은 우리나라 중부 내륙에서 서해로 흐르는 유로연장 401km, 유역면적이 전 국토면적의 약 10%에 해당하는 $9,886km^2$에 이르는 남한의 5대강 중 하나이다. 1981년, 이 강의 하구로부터 150km 상류지점인 대전시 동북쪽 16km, 청주시 남쪽 16km의 대전시와 충청북도가 만나는 지점에 대청다목적댐이 준공되었다. 대청다목적댐은 높이 72m, 길이 495m, 체적 123만$4,000m^3$의 콘크리트 중력식 댐과 석괴식 댐으로 구성된 복합형 댐으로서, 이 댐의 주요시설로는 저수용량 14억9,000만$m^3$의 본 댐과 조정지 댐이 있다. 그 후 1992년에는 대청 조정지 댐 하류 200m 지점에 현도 지방 산업단지 취수장(시설용량: $17,600m^3$/일)이 건설되었으며, 통상 하루 약 7,500톤의 물을 인근의 공단에 공급해오고 있다. 하지만 최근, 취수량이 급격히 감소됨에 따라, 인근 공단으로의 물 공급에 많은 어려움이 발생하고 있다. 이에 대한 대처 방안으로서 한국수자원공사는 취수장 관리자의 요구에 따라 조정지 댐 방류 수문 위치조정 및 방류량 조절 등의 조치를 취하고 있지만, 그 효과는 정량적으로 검토되어지지 않았다. 그러므로 본 연구에서는 위에서 명기한 조치의 실효성을 파악 하고자, 수문의 위치변화에 따른 취수구 부근의 수리특성을 조사하였다. 구체적인 조사항목은 다음과 같다. 첫째, 하천용 유량측정장비 (StreamPro ADCP (Teledyne RD Instruments))를 이용한 방류구와 취수구 사이의 유량 조사 둘째, 다 항목 수질 및 3차원 유속 측정장비 (ADV6600 (Sontek / YSI, Inc.))를 이용한 취수구 앞에서의 유속, 유향 및 수위변동 조사 셋째, 수위계 (Orphimedes (OTT MESSTECHNIK GmbH & Co. KG)) 및 파고계 (Compact-WH (Alec Electronics Co., Ltd.))를 이용한 하천을 횡단하는 취수구 좌 우 지점에서의 수위변동 모니터링 그 결과 방류수문의 위치변화에 따른 취수구 인근의 수리학적 특성은 조정지 댐의 방류수문으로부터 약 100 - 150 m 하류의 횡단면에서는 유속분포의 차이가 발견 되었으나 하류로 흐름이 진행됨에 따라 그 차이는 감쇄되고 약 200m 떨어진 취수구 앞의 횡단면에서는 유속분포가 거의 동일함을 알 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.855-861
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• 2013

Small-pore Cu-chabazite SCR catalysts with high NOx conversion at low temperatures are of interest for marine diesel engines with exhaust temperatures in the range of 150 to $300^{\circ}C$. Unfortunately, fuels for marine diesel engines can contain a high level of sulfur of up to 1.5% by volume, which corresponds to a $SO_2$ level of 500 ppm in the exhaust gases for an engine operating with an A/F ratio of 50:1. This high level of $SO_2$ in the exhaust may have detrimental effects on the NOx performance of the Cu-chabazite SCR catalysts. In the present study, a bench-flow reactor is used to investigate the effects of sulfur poisoning on the NOx performance of Cu-chabazite SCR catalysts. The SCR catalysts were exposed to simulated diesel exhaust gas stream consisted of 500 ppm $SO_2$, 5% $CO_2$, 14% $O_2$, 5% $H_2O$ with $N_2$ as the balance gas at 150, 200, 250 and $300^{\circ}C$ for 2 hours at a GHSV of 30,000 $h^{-1}$. After sulfur poisoning the low-temperature NOx performance of the SCR catalyst is evaluated over a temperature range of 150-$300^{\circ}C$ to determine the extent of the catalyst deactivation. Desulfation is also carried out at 600 and $700^{\circ}C$ for 30 minutes to determine whether it is possible to recover the NOx performance of the sulfur-poisoned SCR Catalysts.

• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.147-153
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• 2015

Various adverse effects can occur due to direct exposure from toxic substances when toxic materials are used to restore river ecosystems. Thus, this study performed analysis on the development of toxicity in terms of survival and abnormality rates using embryos of Bombina orientalis living in Korea to analyze the toxicity of materials used in the river projects. The results showed that the toxicity in cement (C group) was the strongest whereas the toxicity in plant-based polyurethane (P1 group) was the weakest. Survival rates of B. orientalis embryos were 100%, 94 - 95%, 66 - 89% and 0% in control, P1, polyurethane (P2) and C groups, respectively. Abnormalities of embryos were 10.5%, 5.3 - 10.5%, 26.3 - 27.8% and 35.7% in control, P1, P2 and C groups, respectively. Furthermore, we verified that having a sufficient curing time reduced toxic substances that were extracted. The above result suggest that cement and polyurethane hamper the early development of amphibians. In conclusion, it is highly important to review biological safety with respect to the selection of materials used to restore rivers. This study shows the importance of the selection of eco-friendly materials and processes.

• Korean Journal of Ecology and Environment
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• v.56 no.3
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• pp.187-195
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• 2023

Almost all of the water from agricultural dams located to the upper of the Yeongsan river is supplied as irrigation water for farmland and thus is not discharged to the main stream of the river. Also, most of the irrigation water does not return to the river after use, adding to the lack of flow in the main stream. As a result, the water quality and aquatic health of the river have become the poorest among the four major rivers in Korea. Therefore, in this study, several strategies for water quality improvement of the river were developed considering pollution reduction and flow rate increase, and their effect analysis was performed using a water quality model. The results of this study showed that the target water quality of the Yeongsan river could be achieved if flow increase strategies (FISs) are intensively pursued in parallel with pollution reduction. The reason is because the water quality of the river has been steadily improved through pollution reduction but this method is now nearing the limit. In addition, rainfall-related FISs such as dam construction and water distribution adjustment may be less effective or lost if a megadrought continues due to climate change and then rainfall does not occur for a long time. Therefore, in the future, if the application conditions for the FISs are similar, the seawater desalination facility, which is independent of rainfall, should be considered as the priority installation target among the FISs. The reason is that seawater desalination facilities can replace the water supply function of dams, which are difficult to newly build in Korea, and can be useful as a climate change adaptation facility by preventing water-related disasters in the event of a long-term megadrought.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.931-939
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• 2016

Bangudae Petroglopys of the national treasure No. 285 located in elevation of 53 m to 57 m have been damaged by repetition of submergence and exposure due to the Sayeon-dam of EL.60 m constructed in down stream. In this study, as a preservation plan of the petroglyphs from the contact with water, the construction of eco-levee was suggested and its effect was investigated in the views of hydraulic engineering. It was designed to be located aside of 80 m from Bangudae Petroglyphs with the length of 440 m in streamwise direction, and it was need to construct a new channel maintaining the original hydraulic capacity and conveyance. Hydraulic characteristics such as water surface elevations and velocities near Bangudae Petroglyphs were measured after the eco-levee was installed in the hydraulic model with the scale of 1:50. It showed that there were not much changes of water surface elevations and velocities between sayeon-dam spillway EL. 60 m (Suggestion 1) and EL. 54 m (Suggestion 2). It was concluded the eco-levee could be made of natural materials like soil, pebble, gravel in terms of allowable velocity and shear stresses. The slope of water surface at Suggestion 2 was steeper, and velocities near Bangudae Petroglyphs were also faster than Suggestion 1. As the vorties occured at the left side in Suggestion 2, more detailed study is required.

• Ocean and Polar Research
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• v.24 no.2
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• pp.123-134
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• 2002

Seasonal variations of settling particles and metal fluxes were monitored at a nearshore site of Marian Cove, King Geroge Island, Antarctica from 28th February 1998 to 22nd January 2000. Near-bottom sediment traps were deployed at 30m water depth of the cove, and sampling bottles were recovered every month by SCUBA divers. Total particulate flux and metal concentrations were determined from the samples. Total particulate flux showed a distinct seasonality, high in austral summer and low in austral winter: the highest flux $(21.97g\;m^{-2}d^{-1})$ was found in February of 1999, and the lowest $(2.47g\;m^{-2}d^{-1})$ in September of 1998, when sea surface was frozen completely. Lithogenic particle flux accounted for 90% of the total flux, and showed a significantly negative correlation with the thickness of snow accumulation around the study site. It was suggested that the most of the lithogenic particles trapped in the bottles was transported by melt water stream from the surrounding land. Fluxes of Al, Fe, Ti, Mn, Zn, Cii, Co, Ni, Cr, Cd, and Pb showed similar seasonal variations with the total flux, and their averaged fluxes were 34000, 9000,960, 180, 13.8, 17.6, 3.0,2.1, 5.4, 0.02, and $1.5nmol\;m^{-2}d^{-1}$ respectively. Among the metals, Cu and Cd showed the most noticeable seasonal patterns. The Cd flux correlated positively with the fluxes of biogenic components while the Cu flux correlated with both the lithogenic and biogenic particle fluxes. The Cu flux peak in the late summer is likely related to a substantial amount of inflow of ice melt water laden with Cu-enriched lithogenic particles. On the other hands, the Cd flux peak in the early spring may be associated with the unusually early occurred phytoplankton bloom.

• Restorative Dentistry and Endodontics
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• v.15 no.1
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• pp.107-119
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• 1990

The purpose of this study was to evaluate the marginal adaptability of the amalgam restorations in applying the cavity varnish (Copalite$^{(R)}$) and dentin bonding agent (Scotchbond 2$^{(R)}$) under the scanning electron microscope. For this study, eighteen sound extracted human molars were selected. Class I cavities in 12 teeth and class V cavities in 6 teeth were prepared using an air turbine with No. 701 tungsten carbide bur and finished using a low speed handpiece with No. 557 fissure bur. The prepared specimens were then divided into three groups including 4 class I cavities and 2 class V cavities in each group and restored as follows ; Group I. All the prepared cavities were restored with amalgam only (Control). Group II. Two layers of Copalite$^{(R)}$ cavity varnish were applied to the cavities with a gentle stream of air after each application and cavities were restored with amalgam. Group III. The enamel cavity margins were etched with 37% phosphoric acid gel for 60 sec., rinsed for 30 sec. and dried. One layer of visible lightcured Scotchbond Dental Adhesive$^{(R)}$ was applied and immediately cured for 20 seconds with visible light-cure unit and cavities were restored with amalgam. All the specimens were cut at the neck of the teeth and the occlusal halves of specimens were sectioned buccolingually in the longitudinal axis centering the amalgam restorations, using the disk. The cut specimens were ground with sandpapers (400, 600, 800, 1000 grit), and cleaned for 5 minutes in the ultrasonic cleaner (Brason Co. U.S.A.). In the cut surfaces, the amalgam - tooth interfaces were examined under the scanning electron microscope (JSM, 35C type, JEOL). The obtained results were as follows ; 1. The amalgam-tooth interfaces were reduced more significantly in the Copalite$^{(R)}$ and Scotchbond 2$^{(R)}$ application group than in the control group. 2. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed the findings similar to the Copalite$^{(R)}$ application group in the cavity floor, and the marginal adaptability was better in the side wall than in the cavity floor. 3. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed better marginal adaptability in the occlusal margin than in the gingival margin. 4. The marginal adaptability was in the order of the Scothbond 2$^{(R)}$ application group, the Copalite$^{(R)}$ application group and the control group.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.5
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• pp.469-484
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• 2016

HR-ToF-AMS was applied for a seasonal and size-distributional measurements for inorganic ($SO{_4}^{2-}$, $NO_3{^-}$, $NH_4{^+}$, $Cl^-$) and organic components in Baegryung Island Super Site. The average concentration of $PM_{1.0}$ remarks $12.9{\mu}g/m^3$ while $14.5{\mu}g/m^3$ in Spring time, $14.2{\mu}g/m^3$ in Winter, $13.1{\mu}g/m^3$ in Summer and $9.86{\mu}g/m^3$ in Autumn. The mass of measured $PM_{1.0}$ shows 54.6% of $PM_{2.5}$ which is similar to those of Beijing and Lanzhou, China. The highest portion of Chemical composition is $SO{_4}^{2-}$ marking 41.0%, 31.8% by organics, 13.5% by $NH_4{^+}$, 12.8% by $NO_3{^-}$ and 1% by $Cl^-$. In every seasons, except winter, $SO{_4}^{2-}$ remarks the highest level, organic components take place the highest in winter time. The size-distribution of $PM_{1.0}$ components scattered at accumulation mode of 200 nm~800 nm which means the influence of primary emission is low. In case of air stream from the industrialized area of Sandung, Shanghai, China, the concentrations of such components were distributed a bit higher.

• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.729-734
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• 2005

A sensitive and selective method for quantitation of sofalcone and its active metabolite in human plasma has been established using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS). Plasma samples were transferred into 96-well plate using an automated sample handling system and spiked with 10 $\mu$L of 2 $\mu$g/mL $d_3$-sofalcone and $d_3$-sofalcone metabolite solutions (internal standard), respectively. After adding 0.5 mL of acetonitrile to the 96-well plate, the plasma samples were then vortexed for 30 sec. After centrifugation, the supernatant was transferred into another 96-well plate and completely evaporated at 40 ${^{\circ}C}$ under a stream of nitrogen. Dry residues were reconstituted with mobile phase and were injected into a $C_{18}$ reversed-phase column. The limit of quantitation of sofalcone and its metabolite was 2 ng/mL, using a sample volume of 0.2 mL for analysis. The reproducibility of the method was evaluated by analyzing 10 replicates over the concentration range of 2 ng/mL to 1000 ng/mL. The validation experiments of the method have shown that the assay has good precision and accuracy. Sofalcone and its metabolite produced a protonated precursor ion ([M+H]$^+$) of m/z 451 and 453, and a corresponding product ion of m/z 315 and 317, respectively. Internal standard ($d_3$-sofalcone and $d_3$-sofalcone metabolite) produced a protonated precursor ion ([M+H]$^+$) of m/z 454 and 456 and a corresponding product ion of m/z 315 and 317, respectively. The method has been successfully applied to a pharmacokinetic study of sofalcone and its active metabolite in human plasma.