• 상하수도학회지
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• 제28권6호
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• pp.713-723
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• 2014

Biofouling in brackish water reverse osmosis (RO) membranes still needs extensive research to understand cause and mechanism and to obtain methods for reduction of its impact on RO applications. Natural compounds with biofilm formation inhibitory properties are being investigated. Two compounds, vanillin and Epigallocatechin gallate (EGCG), were selected due to their great potential on biofilm formation inhibition. Vanillin shows inhibition on quorum sensing mechanisms of biofilm formation. EGCG has potential to inactivate microbial activity. The two compounds were incorporated in typical polyamide reverse osmosis membranes and evaluated on flux behaviours and biofilm formation potential. The surface properties of membrane coated with vanillin were changed tremendously compared to those with EGCG. As a result, the flux was reduced substantially. The biofilm formation seems hindered with EGCG coated membranes compared to the virgin membranes. More research is needed to optimize coating methods applicable to RO membranes and to enhance biofouling reduction.

• 상하수도학회지
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• 제27권2호
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• pp.185-196
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• 2013

In Yongwon channel, its natural flow of seawater is blocked by the construction of Busan Newport including the container berth. The channel was transformed into a narrow and long one, where it is possible that ships are only allowed to pass through the north-side channel of Gyeonmado located at the point of river mouth to Songjeongcheon. In addition, Yongwon channel is approximately 100 m wide on average and 3,600 m long, which has the highest slenderness ratio (length/width=36). So it is considered that the changes in the terrain characteristics of Yongwon channel is likely to alter the circulation of sea water, thereby changing its water quality. In this study, the seasonal change and the spatial variation of the water quality in Yongwon channel was analyzed for the effect of land pollution using the measurement data. The mass balance calculation method is used to analyze the water pollution resulting from sediment pollutants. This result shows that the improvement of the water quality in Yongwon channel can be obtained from the sewer pipe modification and the environmental dredging.

• 상하수도학회지
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• 제17권4호
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• pp.567-573
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• 2003

The pretreatment process was carried out to solubilize the sewage sludge for enhancing its biodegradability using alkaline treatment, ultrasonic treatment(15kHz), ozone treatment and different combination of these three methods: alkaline followed by ultrasonic as well as ozone, and ultrasonic followed by alkaline. The solubilization efficiency was evaluated based on the SCOD/TCOD ratio and VSS/TS ratio. In results, the proper condition of alkaline treatment was shown as 30meq/l of NaOH, pH 12 and 3hours of reaction time. Solubilization efficiency increased to 17% from initial 2% based on SCOD/TCOD ratio under this condition. In ultrasonic treatment, the higher ultrasonic power, the longer treatment time and the lower sludge volume resulted in higher solubilization respectively. There was a rapid increase in solubilization efficiency after 20 minute, then it was measured as 32% of SCOD/TCOD ratio in 1 hour at a ultrasonic power of 1,300W with 1/sludge. Solubilization efficiencies in combined treatment using alkaline and ultrasonic were 47-53% higher than single treatment at a sonicated time of 1 hour. Ozone treatment followed by alkaline treatment also represented the enhanced solubilization compared to ozone treatment. Therefore, ultrasonic or ozone treatment assisted by alkaline could achieve the short treatment time as well as high solubilizetion efficiency.

• 상하수도학회지
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• 제21권1호
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• pp.101-112
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• 2007

This study has used RMA2 model and RMA4 model, which are depth-averaged two-dimensional flow and water-quality prediction models, to analyze the variation of the water-quality by the gates operation in the Seonakdong River. Sensitivity analysis is performed to get the Manning coefficient and the coefficient of eddy viscosity for RMA2 model, and to get the diffusion coefficient for RMA4 model. Since the numerical simulation using RMA2 and RMA4 models did not consider tributary pollutant load except for that of Joman River, it could make a little difference from the natural phenomenon. Nevertheless, the numerical simulation shows that the discharge of $30m^3/s$, which is the continuous inflow from the Daedong-gate, can make it possible to achieve the target water-quality (BOD 4.3mg/L) of Nakbon-N watershed about 10 days later if the Daejeo-gate could remain opened in connection with the Noksan-gate operation.

• 상하수도학회지
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• 제24권1호
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• pp.15-24
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• 2010

Coagulation can be used for pretreatment of NF membrane filtration. Foulants such as organic matter and particulate can be removed effectively with the process while high flux recovery is maintained. Recently various types of polyaluminium coagulants including polyaluminium chloride(PAC) are commercially available for water treatment. This study examines effects of polymeric Al and hydrolysis products of PAC on nanofiltration membrane performance. Dominant hydrolysis products were polymeric Al, $Al(OH)_3$, and ${Al(OH)_4}^{-1}$ at acidic, neutral, and alkaline pH conditions, respectively. Under acidic pH condition, flux decline was increased with increasing PAC concentrations, possibly due to polymeric Al adsorption on membrane pore and/or surfaces. For neutral and alkaline pH conditions, little flux decline was observed with increasing PAC concentrations except the highest ${Al(OH)_4}^{-1}$ concentration, with which rapid flux decline was shown. Removal of ionic matters was also varied with pH conditions in this study. Especially, conductivity removal was substantially low and $Ca^{2+}$ concentration in the permeate was quite high at neutral pH condition.

• 상하수도학회지
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• 제37권6호
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• pp.311-324
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• 2023

As an advanced study on the method of calculating the target revenue water ratio of local waterworks through the leakage component analysis method proposed by Kim et al. (2022), this study developed a model to calculate the achievable revenue water ratio within the specified project cost, the required project cost to achieve the specified target revenue water ratio, and the economically appropriate target revenue water ratio level by considering the leakage reduction cost and leakage reduction benefit for each revenue water ratio improvement strategy, and conducted an applicability evaluation of the developed model using actual field data. The procedure for calculating the target revenue water ratio of local waterworks considering economics proposed in this study consists of three stages: physical data linkage model construction, leakage component analysis, and economic analysis, and the applicability was evaluated for Zone H with branch type and the Zone M network type. As a result of the application, it was calculated that approximately 32.5 billion won would be required to achieve the target revenue water ratio of 70% in the Zone H, and approximately KRW 10.5 billion would be required to achieve the target revenue water ratio of 75% in the Zone M. If the business scale of Zones H and M was corrected to 10,000 m³/day of water usage, the required project cost for a 1% improvement in the revenue water ratio of Zone H was calculated to be 0.7642 billion won and 0.4715 billion won for Zone M.

• 벤처창업연구
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• 제9권5호
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• pp.221-234
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• 2014

2013년 중국의 쇠고기 수입금액이 13.3억 달러(전년대비 4.8배)로 치솟는 등 최근 중국의 쇠고기 소비시장이 급변하고 있다. 글로벌 쇠고기 시장은 이와 같은 중국 시장변화에 주목하며 시장접근 전략마련에 고심하고 있으나, 우리는 한우고기의 낮은 가격경쟁력에만 초점을 맞추다보니 중국을 수출상대국으로서 분석하는 작업이 미흡하였다. 한 중 FTA 등 시장개방이 본격화 될 경우 한우고기 사육농가의 피해방지를 위한 시장 방어적 차원에서의 논의만이 이루어져 오고 있었다. 중국 쇠고기 시장은 가격경쟁이 치열한 저급육 시장이 지배적이지만 품질과 안전을 추구하는 고급육시장이 형성되고 있다. 이에 본 연구팀은 한우고기 수출을 위한 첫걸음으로 중국 1선급 도시인 베이징, 상하이의 쇠고기 가격 및 품질 등에 대한 시장조사를 수행하고, 한우고기의 대중국 쇠고기 시장에서의 가격경쟁력을 분석하였다. 분석결과 한우고기는 우둔, 갈비, 등심 부위가 베이징, 상하이에서 판매되고 있는 중국산, 수입산 쇠고기 고가그룹에서 가격경쟁력 우위를 확보하고 있는 것으로 나타났다. 특히, 베이징에서는 한우고기 우둔과 등심부위가, 상하이에서는 한우고기 갈비와 등심부위가 가격경쟁력이 확보된 것으로 나타났다.

• 자원ㆍ환경경제연구
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• 제11권3호
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• pp.415-446
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• 2002

Due to its cost effectiveness, tradeable emission permits (TEP) system has been effectively used in the USA and many other advanced countries. But, academic many researchers have been argued that TEP system would not work as an efficient regulatory tools when there are imperfect competition in permits and/or products markets. Sartzetakis (1997), however, show that TEP system can serve as an effective environmental regulation under the certain demand/cost conditions even though duopolistic production market is not competitive. In this paper we extend Sartzetakis's analysis into the differentiated products markets under the same cost conditions, and examine the relative efficiency of TEP system by comparing it with the command and control system. We then show that the main results of Sartzetakis can hold if two differentiated products markets have the symmetric demands. In particular, it is revealed that social welfare will be increased under TEP system even though consumer surplus may be decreased.

• 도서관문화
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• 제38권3호통권304호
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• pp.46-58
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• 1997

1997년 1월 22일을 전후하여 전국의 주요 언론매체들은 정부의 ‘경쟁력 10% 이상 높이기’추진 방안을 일제히 보도하였다. 그에 의하면 정부 기능의 민간위탁 가능분야로 상하수도, 청사건물 경비.관리, 공공차량 운영 등과 함께 도서관경연을 예시하였다. 우리 도서관에서는 이같은 정부의 느닷없는 발표를 보고 놀라움과 함께 비상한 관심을 갖게 되었다. 그러나 정부가 구상하고 있는 이른바 ‘도서관의 민간위탁’에 관하여 정부 구상의 내용은 아직 아무것도 밝혀진 것이 없고, 따라서 도서관을 민간에 위탁한다는 것은 도대체 무엇을 어떻게 한다는 뜻인지, 궁금증과 의구심맞 증폭되고 있는 형편이다. 다만, 일본의 도서관계가 이와 유사한 것을 경험한 것으로 보이는 자료들이 여럿 있다. 이에 '도서관문화‘는 그자료 가운데 하나인 ‘국립도서관의 자료와해설’(도서관문제연구회 위탁문제연구회 편집, 도서관문제연구회 발행 1996)중에서 우선 두 건의 기사를 번역하여 지난 호(제38권 제2호)본란에 게재하였고, 이어서 이 번 호에는 ‘공립도서관의 위탁에 대하여’(일본도서관협력회도서관경영관에 관한 기분문제검토위원회)를 싣는다. (이 기사의 번역 게재는 발행자의 동의를 얻었으며, 번역 작업에는 이번에도 국립중앙도서관 조재순 사서의 협력이 있었다.)

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.385-386
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• 2006

온라인 가상강의는 전형적인 오프라인 강좌에 비해 많은 장점을 가지고 있는 반면에 교수자의 학습감독권과 교수자가 학습자의 상태를 파악하여 능동적으로 강의내용을 변경할 수 있는 기능을 갖지 못하기 때문에 학습자의 결연한 학습의지가 전제되지 않으면 기대하는 학습효율을 얻을 수 없다는 문제점들이 교육공학적인 측면에서 거론되고 있다. 따라서, 본 연구에서는 온라인 가상강좌에서 해결되지 않은 학습감독원을 부여하기 위해서 눈꺼플 움직임과 머리의 상하움직임만으로 학습자의 학습태도를 평가하고, 이에 따라 능동적으로 강좌가 진행될 수 있는 교수-학습모델을 제안한다.