• 자원환경지질
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• 제35권6호
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• pp.581-588
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• 2002

• 한국환경과학회지
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• 제25권7호
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• pp.927-935
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• 2016

Dissolved oxygen is necessary for many biological processes as well as many industrial practices. Dissolved oxygen released from water in dissolved air flotation (DAF) systems can be have many different applications. However, DAF systems are very costly to operate. To develop more efficient DAF systems, a deeper understanding of the process of oxygen being released from water is required. In this study, molecular dynamics (MD) simulations were used to simulate 100 oxygen molecules surrounded by 31002 water molecules at temperatures ranging from $0^{\circ}C$ to $100^{\circ}C$. Simulations were carried out for 10 ns, during which, in most cases, all the oxygen molecules were released from the water droplet. With MD simulations, visualization of the molecules escaping the water droplet was possible, which aided the understanding of the interactions between molecules at the nano-scale. The results showed that as the oxygen molecules moved near the edge of the water droplet that the oxygen molecules hesitated before escaping the water droplet or returned to the interior of the water droplet. This was because of the attractive forces between the water and oxygen molecules. Moreover, after most of the oxygen molecules were released from the droplet, some were found to return to the droplet's edge or even the interior of the droplet. It was also confirmed that oxygen molecules were released at a faster rate at higher temperatures.

• 한국철도학회논문집
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• 제10권6호
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• pp.751-757
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• 2007

이 논문은 엔터프라이즈 아키텍처 접근을 기반으로 시스템 수준의 철도안전정보지원시스템의 안전 요소에 대한 요구사항 개발에 관한 내용이다. 모델링은 다음과 같은 절차를 따른다. 첫째로, 요구사항은 EIA-632프로세스를 따른다. 또한 관련 전문가의 도움을 받아 사고기반 시나리오를 개발한다. 개발된 시나리오는 DoDAF모델을 지원하는 CASE 도구의 지원을 받아 구현한다. 이 결과는 시스템관련 종사자의 이해를 돕는다.

• 상하수도학회지
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• 제27권2호
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• pp.261-272
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• 2013

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

• 상하수도학회지
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• 제34권6호
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• pp.393-402
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• 2020

In the membrane process, it is important to improve water treatment efficiency to ensure water quality and minimize membrane fouling. In this study, a pilot study of membrane process using reservoir water was conducted for a long time to secure high flux operation technology capable of responding to influent turbidity changes. The raw water and DAF(Dissolved Air Flotation) treated water were used for influent water of membrane to analyze the effect of water quality on the TMP (Trans Membrane Pressure) and to optimize the membrane operation. When the membrane flux were operated at 70 LMH and 80 LMH under stable water quality conditions with an inlet turbidity of 10 NTU or less, the TMP increase rates were 0.28 and 0.24 kPa/d, respectively, with minor difference. When the membrane with high flux of 80 LMH was operated for a long time under inlet turbidity of 10 NTU or more, the TMP increase rate showed the maximum of 43.5 kPa/d. However, when the CEB(Chemically Enhanced Backwash) cycle was changed from 7 to 1 day, it was confirmed that the TMP increase rate was stable to 0.23 kPa/d. As a result of applying pre-treatment process(DAF) on unstability water quality conditions, it was confirmed that the TMP rise rates differed by 0.17 and 0.64 kPa/d according to the optimization of the coagulant injection. When combined with coagulation pretreatment, it was thought that the balance with the membrane process was more important than the emphasis on efficiency of the pretreatment process. It was considered that stable TMP can be maintained by optimizing the cleaning conditions when the stable or unstable water quality even in the high flux operation on membrane process.

• 생명과학회지
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• 제8권3호
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• pp.305-311
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• 1998

These studies were undertaken to investigate changes of neutral lipid content and fatty acid composition were determined. Also accumulation process of monoglyceride, diglyceride and triglyceride content, and fatty acid composition were investigated during the development. The results were summarized as follows ; Changes of lipid during development sesame seeds, glycolipid contents which showed the highest in the early ripening stage and after that rapidly decreased, and phospholipid contents showed a similar pattern as glycolipid occurred. In contrast, the content of neutral lipid was rapidly increased by 29.21% 10 days after flowering(DAF), and showed the highest value by 91.84% at 40th day after flower. The neutral lipid, triglyceride content was rapidly increased as the seeds developed, and consisted of over 60% of the neutral lipid since 30 DAF. In the changes of neutral lipid, phospholipid and glycolipid, stearic acid and palmitic acid decreased during the seed ripening. However, oleic acid and linoleic acid increased during the same periods. Linolenic acid, which showed relatively higher value in the early ripening stage, but rapidly decreased as much as 1% at the later ripening stage.

• 한국물환경학회지
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• 제20권6호
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• pp.676-684
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• 2004

Many researchers have been carrying on study to figure out the exact collision efficiency between bubble and floc. Collision efficiency can has generally been quantified by using trajectory analysis which uses the hydrodynamic, the electrostatic and van der waals forces. Two types of method are considered to induce the hydrodynamic force in the trajectory analysis. One is to use stream function and the other is to use mobility function. There was some difference between stream and mobility function depending upon modelling factors and conditions in trajectory analysis.

• 대한안전경영과학회지
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• 제9권6호
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• pp.9-17
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• 2007

This article addresses the question of how the operational architecture for a railway safety information system should be developed. A successful railway safety information system can be developed by fully reflecting the business process and needs at the enterprise level. To date, there has been minimal research effort towards the development of the operational architecture for a railway safety information system. To this end, a variety of enterprise architectures have been studied so far. In this paper, as an important guideline, DoDAF (Architecture Framework) is selected to be used in developing a railway safety information system. In particular, we propose a method to implement the operational architecture based on DoDAF.

• 한국철도학회논문집
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• 제11권1호
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• pp.101-106
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• 2008

최근 아키텍처 프레임워크가 정보관리 시스템 개발에 사용되고 있다. 본 논문은 미국방 아키텍처 프레임워크를 사용하여 철도 안전성 평가에 대한 운용 아키텍처 개발 방법론에 대해 기술한다. 철도 시스템과 같이 안전에 민감한 시스템의 경우는 안전성 평가 업무를 효과적이고, 효율적으로 수행하기 위해 정보관리 시스템의 필요성이 증대되고 있다. 운용 아키텍처를 기반으로 안전성 평가에 대한 정보관리 시스템의 요구사항을 생성하는 것은 필수적이다. 철도시스템에 적용 가능한 안전성 평가 운용 아키텍처를 개발하기 위해 ARP4761이 참고 되었다. 우선, 상용 시스템엔지니어링 도구인 CORE를 활용한 운용 아키텍처 개발 프로세스를 수행하기 위해 스키마 및 템플릿 개발하였다. 운용 아키텍처는 유연한 정보 관리 시스템 구축을 가능하게 할 뿐만 아니라 업무 프로세스의 문제도 해결하는데 도움을 준다.

• 대한기계학회논문집B
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• 제39권7호
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• pp.617-624
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• 2015

용존공기부상법이란 오염물에 미세기포를 부착하여 수표면으로 부상시킴으로써 이를 제거하는 수처리 방법이다. 본 연구에서는 난류모델에 따른 용존공기부상조 내부 유동해석의 변화를 고찰하기 위해 물과 기포의 혼합물에 대한 2상 유동을 모사하였다. 이때, 주어진 용존공기부상조 형상 및 조건에 대하여 다양한 난류모델에 따른 용존공기부상법 내부의 미세기포 분포량, 계산시간 및 수렴성 등을 비교하였으며, 그 결과 기존에 주로 사용되었던 표준 ${\kappa}-{\varepsilon}$ 모델이 타 난류모델과는 다른 거동을 예측하는 것으로 확인되었다.