• Structural Monitoring and Maintenance
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• 제2권2호
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• pp.145-164
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• 2015

Bridge scour is the predominant cause of overwater bridge failures in North America and around the world. Several sensing systems have been developed over the years to detect the extent of scour so that preventative actions can be performed in a timely manner. These sensing systems have drawbacks, such as signal inaccuracy and discontinuity, installation difficulty, and high cost. Therefore, attempts to develop more efficient monitoring schemes continue. In this study, the viability of using optical dissolved oxygen (DO) probes for monitoring scour depths was explored. DO levels are very low in streambed sediments, as compared to the standard level of oxygen in flowing water. Therefore, scour depths can be determined by installing sensors to monitor DO levels at various depths along the buried length of a bridge pier or abutment. The measured DO is negligible when a sensor is buried but would increase significantly once scour occurs and exposes the sensor to flowing water. A set of experiments was conducted in which four dissolved oxygen probes were embedded at different soil depths in the vicinity of a mock bridge pier inside a laboratory flume simulating scour conditions. The results confirmed that DO levels jumped drastically when sensors became exposed during scour hole evolution, thereby providing discrete measurements of the maximum scour depth. Moreover, the DO probes could detect any subsequent refilling of the scour hole through the deposition of sediments. The effect of soil permeability on the sensing response time was also investigated.

• 한국물환경학회지
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• 제37권1호
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• pp.1-9
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• 2021

The depletion of dissolved oxygen (DO) in urban streams has a profound effect on the aquatic ecosystem; however, the change in DO by resuspension of sediments and the cause have not been sufficiently investigated. In this study, the physicochemical properties (particle size, and the content of organic and heavy metals) of the sediments of an urban stream (Anyang Stream) and the characteristics of water quality changes (DO, dissolved organic carbon (DOC), dissolved nitrogen (DN), sediment oxygen demand (SOD), and adenosine triphosphate (ATP)) by sediment resuspension were investigated. The sediment content of fine particles (< 0.2 mm) increased from 36.7% to 52.7% from the upstream to the downstream, and the contents of heavy metals and organic matter of the sediment were also higher towards the downstream. The depletion of DO by resuspension was observed in the sediment at the downstream sites (P8, P9), where the fine particle content was high, and biological SOD (BSOD) was more than 88% compared to the total SOD. The increase in BSOD coincided with the increase in ATP. It was also confirmed that the depletion of DO could increase the amount of heavy metals (such as Fe, Mn, and Pb) released from the sediment. Based on the above results, it can be concluded that resuspension of sediments induces rapid water quality changes and may cause accidents, such as fish mortality, during rainfall, and such a water quality effect can be more pronounced in sediments with a high content of fine particles and organic matter and high biological activity.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.408-412
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• 2004

A total of 23 springs distributed in the southern and northern sides of Mt. Hala in Jeju Island were seasonally sampled and analyzed for their major ion chemistry and oxygen and hydrogen isotope compositions to investigate their hydrogeochemical and isotopic characteristics. Dissolved ion concentrations of the south-side springs slightly increase with decreasing altitude. This indicates that dissolved ion concentrations of groundwater recharged at higher altitudes increase by water-rock interaction during the downgradient migration of groundwater through highly permeable volcanic aquifer. Dissolved ion concentrations of the north-side springs also slightly increase with decreasing altitude, but dramatically increase at ～300 m.a.s.l. This may indicate a sudden input of contaminants to the north-side groundwater system around ～300 m.a.s.l. Springs located in areas above ～300 m.a.s.l. have very low concentrations of dissolved ions, showing little seasonal variations. Whereas springs located in areas below ～300 m.a.s.l. show a big seasonal variation in the concentration of dissolved ions. Seasonal variation of oxygen isotope compositions of springs is ～3$\textperthousand$ for high-altitude springs (～1700 m.a.s.l.) and is ～2$\textperthousand$ near shore, indicating an attenuation of the variation through mixing with other groundwater bodies during migration.

• 대한토목학회논문집
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• 제41권5호
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• pp.493-504
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• 2021

와류에 의해 물과 산소의 충돌을 반복적으로 일으켜 산소를 용존시키는 Multistage Vortex Aerator를 하천 정화에 적용하였다. 본 연구의 대상 현장인 괴정천은 부산시 사하구 도심을 흘러 낙동강 하구로 연결되는데, 우천 시에는 비점 오염물질이 유입되고 평시에도 하수 슬러지가 일부 유입되어 퇴적을 반복함에 따라 하천수의 용존산소 농도가 혐기성 상태에 가까웠다. 산소농도가 최소 0.1 ppm인 하천수를 흡입하여 22 ppm 이상으로 산소를 용존시켜 분당 1 m³을 순환시켰을 때, 하천에 나타나는 수질과 악취 변화를 2개월간 모니터링하였다. 운영 결과, 용존산소가 하천 전체적으로 약간 나쁨(4)~나쁨(5)에서, 좋음(1b)~보통(3) 등급으로 개선되었고, 총인 농도는 평균 76 % 감소되었다. 복합악취는, 하천 전체가 혐기화된 측정일에 최대 84.5 % 저감을 관찰할 수 있었다.

• 환경위생공학
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• 제15권1호
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• pp.7-13
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• 2000

To develop the removal technique of algal bloom the efficiencies of algal flocculation/ autoflotation by the kinds of coagulant and oversaturated oxygen concentration were investigated. The summarized results are as follow. 1. In the algae flocculation test with alum[$Al_2(SO_4)_3{\cdot}18H_2O$], optimum pH was 5.5 and, with chitosan optimum pH was 7.0. 2. Chitosan which was natural polymer showed the 5~10 times higher algal biomass flocculation efficiency than alum in the condition of same algal concentration. 3. For the each coagulant, the higher ${\Delta}DO$(oversaturated dissolved oxygen concentration - saturated dissolved oxygen) was, the faster the rising velocity of the algal floc was. 4. In the condition of about 4mg/L ${\Delta}DO$, the rising velocity of chitosan is about 2 times higher than that of alum, and chitosan formed the stronger algal floc.

• 한국물환경학회지
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• 제24권4호
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• pp.458-464
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• 2008

Bulking phenomena and scum formation are common problem in suspended growth system like the activated sludge plants for wastewater treatment. Apart from wastewater composition, operating conditions, such as mechanical stress by insufficient oxygen supply, are often decisive for the occurrence of a bulking or scumming problem. There were the comparative aeration tanks in terms of sludge bulking caused by the difference of mechanical aeration facilities in the wastewater treatment plant of N paper mill company. In this study the cause of bulking was investigated through not only the biological isolation and identification but also a series of operational data consideration. On the basis of the investigation results for bulking cause, the operational criteria on dissolved oxygen concentration was derived to decrease the bulking problem.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.343-346
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• 2001

The effect of agitation speed and aeration rate on mTG production and cell growth by Streptoverticillum morbarense was investigated. Dissolved oxygen was controlled by on-line computer-controlled fermentation system. The agitation speed and aeration rate of 2.5 L fermentor ranged from 330 to 360 게m and 1 vvm to 4 vvm, respectively. The highest mTG production was 2.1 U/mL when dissolved oxygen level was 20%, and it was improved almost 1.1 times in comparison with that without dissolved uxygen control.

• 한국해양학회지
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• 제11권2호
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• pp.89-95
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• 1976

우리 나라 연안에 대한 해양학적 조사는 그렇게 조직적으로 조사된 편이 못된다. 1960년대 이후로 수질오염과 관련해서 연안수질조사를 많이 실시해왔지만(원;1963, 1964, 1970, 장과 배;1968, 박 등;1969, 이 등;1969, 김;1970, 원과 박;1970, 1973, 최와 정;1971, 1972, 강;1972, 이 등;1972a, b, 1973, 1974a, b, c, d, e, 1975a, b, 변 등;1973, 한 등;1973, 황 등;1973, 1974, 1975, 김과 조;1974a, b, 박 등;1974a, b 박과 조;1974, 이 등;1974, 정과 권;1974, 곽과 이;1975, 박 등;1975, 박;1975a, b, 김 등;1976, 김 등;1976, 김과 김;1976) 대부분이 해양의 특성을 파악하는데 불충분했고 단 한번을 조사하더라도 면밀한 조사를 실시한 예는 그리 많지 못하다.

• 조명전기설비학회논문지
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• 제19권4호
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• pp.79-84
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• 2005

본 논문은 액중 이온교환수 발생장치 내에 양${\cdot}$음이온교환격막을 중심으로 불평등전계를 형성할 수 있는 사선빗살형 전극을 설치하였다. 그리고 정극성과 부극성의 펄스전압을 인가하여 펄스전압의 극성변화에 의한 산화환원전위 변화가 이온교환수 발생장치 내에서 발생된 용존산소량에 미치는 영향을 비교 검토하였다. 실험결과, 이온교환수 발생장치 내에 인가된 펄스전압의 극성변화와 전기비저항의 차에 의한 산화환원전위 및 용존산소농도 변화를 관찰할 수 있었다. 그리고 인가된 펄스전압의 극성변화와 전기 비저항 차에 의한 전위변화가 용존산소농도를 증가시켜 액중에서 고농도의 이온들을 생성시킴을 알 수 있었다.

• Corrosion Science and Technology
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• 제16권5호
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• pp.265-272
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• 2017

Inhibition of pitting corrosion of the copper sprinkler tubes by removing dissolved oxygen in water with sodium sulfite was studied on the wet sprinkler systems operated in 258 household sites. First, air in the sprinkler tubing was removed by vacuum pumping. The tube was then filled with sodium sulfite dissolved in water. Sodium sulfite was very effective in maintaining a very low dissolved oxygen concentration in water in the sprinkler tube for the observation period of six months. Water leakage from the copper sprinkler tube was reduced significantly by using sodium sulfite. Both pitting corrosion process and pitting corrosion inhibition mechanism were investigated by examining microscopical and structural aspects of corrosion pits formed in failed copper sprinkler tube. Pitting corrosion was caused by pressurized air as well as sediments such as sand particles in copper tubes through oxygen concentration cells. It was confirmed microscopically that growth of corrosion pits was stopped by reducing dissolved oxygen concentration to a very level by using sodium sulfite.