• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.639-645
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• 2008

The objectives of this research are to (1) observe changes in particle size distribution due to formation of microflocs during coagulation process (2) identify the membrane fouling potential on cross flow system (3) investigate the mechanism of membrane fouling. The rate of flux decline for the hydrophobic membrane was significantly greater than for the hydrophilic membrane, regardless of pretreatment conditions. The pretreatment of the raw water significantly reduced the fouling of the UF membrane. Also, the rate of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying coagulation process before membrane filtration showed not only reducing membrane fouling, but also improving the removal of dissolved organic materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle size distribution occurred under rapid and slow mixing condition due to the simultaneous formation of microflocs and NOM precipitates. Therefore, combined pretreatment using coagulation not only improved dissolved organics removal efficiency but also flux recovery efficiency.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.467-469
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• 2016

기존의 소프트웨어 개발자는 객체지향 내에서 나쁜 코드 습관으로 코드 자체의 결합도와 응집도를 고려하지 못 한다. 또한 SW 비가시성으로 인해, SW 내 복잡도 및 품질관리 등이 어렵다. 본 논문에서는 SW 복잡도 및 재사용 향상을 위해, 기존 절차식 모듈 관점 보다는 객체지향 메카니즘으로 응집도의 개념과 이를 통한 내부 코드 응집도 비교 및 가시화 구현하였다. 이는 내부 객체 코드의 응집도를 통해, 객체 내부 및 객체간의 복잡도 인식으로 재사용성과 코드 문제점 확보에 활용하고자 한다.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.67-73
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• 2017

For the bio-fuel conversion of algae, several processes are needed including cultivating, agglomeration, extracting and conversion to the bio-fuel. The production cost for each process makes the total production cost of algae bio-fuel conversion. The production cost of algae bio-fuel has still higher than that of the other commercial bio-fuel. The reduction of production cost for each process enables the competitive price as a bio-fuel. It is difficult to separate the algae from water because of the similar magnitude of density each other. The agglomeration and extracting of algae using ultrasonic wave is rare effect of environmental hazard and also it is appropriate technology for the next generation energy resources. The present research is investigated for the elucidation of algae behavior in the water with the ultrasonics wave. For this purpose, the unsteady computational fluid dynamic analysis has been conducted in the ultrasonic pressure field. The velocity, pressure and algae concentration changes with time have been analysed to clarify the mechanism of algae separation by ultrasonic wave.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.23-28
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• 2016

In spite of various merit of algae as biofuel, the production cost of algae is a considerable obstacle for commercialization. The concurrent development of essential technologies is needed for the cultivating, harvesting, extracting and energy transformation. The production cost of algae biofuel has still higher than that of the other commercial biofuel. The major research activity has been focused on the cultivating and the research of other processes has been done with relatively lower activity. It is difficult to separate the algae from water because of the similar magnitude of density each other. The agglomeration and extracting of algae with the hybrid technology using ultrasonic wave is rare effect of environmental hazard and also it is appropriate technology for the next generation energy resources. The present research is investigated for the effective separation of algae from water with the ultrasonics wave. The aim of the present research is focused on the establishment of optimal design of algae agglomeration system. For this purpose, the computational fluid dynamic analysis has been conducted in the flow field with ultrasonic wave and algae flow to clarify the mechanism of algae separation by ultrasonic wave.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.128-136
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• 2004

The overall objective of this research was to find out the role of rapid mixing conditions in the species of hydrolyzed Al(III) formed by different Al(III) coagulants. When an Al(III) salt is added to water, monomers, polymers, or solid precipitates may form. Different Al(III) coagulants (alum and PACl) show to have different Al species distribution over a rapid mixing condition. During the rapid mixing period, for alum, formation of dissolved Al(III) (monomer and polymer) increases, but for PACl, precipitates of $Al(OH)_{3(s)}$. increases rapidly. Also, for alum, higher mixing speed favoured Al(III) polymers formation over precipitates of $Al(OH)_{3(s)}$ but for PACl, higher mixing speed formed more precipitates of $Al(OH)_{3(s)}$. At A/D and sweep condition, both $Al(OH)_{3(s)}$ and dissolved Al(III) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

• Journal of the Korean Vacuum Society
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• v.2 no.1
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• pp.41-49
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• 1993

두 층으로 이루어진 박막에서 이온선 혼합에 의해 형성되는 결정상 및 비정질상을 예측할 수 있는 새로운 모델을 제시하였다. 기존의 예측 모델과는 달리, 이온선 혼합 공정에서의 확산메카니즘에 영향을 미치는 변수로서 각 원소의 응집에너지와 침입형자리 크기 그리고, 이온반경을 이용하였다. 비정질상 형상 여부를 결정하는 인자로서 ADF(amorphization determinating factor)를 새로 정의하여 다음과 같이 모델식을 세웠다. 즉, ADF=C1(RB-rA)＋C2(Ecoh, max/Ecoh, min)＋$\alpha$이다. ADF가 양의 갓을 갖는 계는 이온선 혼합에 의해 비정질상이 형성되며 ADF가 음의 값을 갖는 계는 비정질상이 형성되지 않는다. 70여 가지의 금속/금속 및 금속/실리콘계에 대한 실험결과로부터 본 모델을 검증하였으며 아직까지 실험결과가 부족한 몇 가지 금속/실리콘계에 대해서 본 모델을 이용하여 비정질상 형성 여부를 예측하였다.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1997.10a
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• pp.65-66
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• 1997

우리나라의 대부분 하천과 인공댐의 경우 조류발생에 기여하는 영양염은 질소, 인 그리고 규소 등인데 특히 인이 생산제한 인자로 작용하고 있다. 따라서 인을 적절히 제거할 경우에는 조류 발생에 의한 수질의 악화와 수이용의 저해요인을 배제할 수 있어 이에 대한 연구가 많이 진행되어 왔다. 지금까지와 연구는 인의 화학적 응집 침전법, 생물학적 처리법에 대하여 수행되어 왔으나 설비자금, 운영비, 운전기술, 슬러지 생성 그리고 제거효율 등에서 만족스런 결과가 도출되지 못하여 현장 적용을 하지 못하고 있는 실정이다. 이러한 현실을 감안하여 우리의 자연 환경에서 쉽게 자할 수 있는 황토를 모재로하여 Al3-과 Fe3-, Ca2-을 적절히 배합하여, 주로 인을 선택적으로 제거하 고자 개발된 황토의 흡착능력 그리고 흡착 메카니즘에 대한 기본적인 연구를 하고자 (1) 등온흡착실험을 통하여 흡착용량을 평가하고 (2) 흡착제거속도를 평 가하였고 (3)파과시간 및 흡착특성을 파악하기 위해 column 흡착실험을 하였다 또한 (4) 황토내의 Al3-, Fe3-과 Ca2- 등이 인의 화학적 흡착에 기여하는 정도를 파악하여 흡착메카니즘을 규명하고자 하였다. 먼저 흡착용량실험을 위하여 PO3-4-P 농도 3ppm의 용액 200mf에 황토 0.2g, 0.5g, 1.0g, 2.0g을 각각 투여한 후 충분한 흡착평형이 일어나게 24시간 동 안 130rpm으로 $25^{\circ}C$ 등온반웅조에서 저어주어 흡착평형에 도달하면 상등액을 GF/C Filter로 여과한 후, 여액에 대해 PO3-4-P의 농도를 Ascrobic he건법으로 측정한 결파, Freundlich 등온흡착식에 의하면 K값은 17.34와 16.28이었으며 1/n 값은 1.32와 1.42로 인흡착 성능이 뛰어난 것으로 평가되었다. 둘째, 흡착속도 실험은 PO3-4-P 농도 1.5ppm의 용액 2f에 259의 황토를 투여하고 충분한 혼합이 일어날 수 있도록 170rpm으로 교반하면서 시간별 용액 의 농도 변화를 측정한 결과, 0.45mg/g/m교의 속도로 15분만에 94.3%의 인 제거 효율을 보였다. 셋째, 직경 12mm의 glass column에 황토를 209 채우고 1.5ppm의 PO34P 용액을 2.Sne11in의 유량으로 통수 시킨 후, 시간에 따른 농도 변화를 측정한 결과, 원수 농도의 50%에 해당하는 파과점까지 약 70시간 만에 도달하였다. 넷째, Al3-, Fe3-과 Ca2- 등이 화학적 흡착에 기여하는 정도를 파악하기 위 하여 황토 2g에 대하여 Hieltijes and Lijklema 방법에 의해 Adsorbed-p, Nonapatite inorganic-P(NAI-P), Apatite-p, Organic-P로 구분하여 분석하고, 총인(Total Phosphorus)을 Standard Methods에 따라 Persulfate digestion후 0.45 m membrane 여지 여과하여 여액에 대해 PO3-4-P의 농도를 Ascorbic Acid 법으로 측정한 결과, NAI-P가 가장 큰 비율을 차지하였고, 부원료로 첨가된 금속 양이온 중 Fe3-이온이 흡착에 기여하는 정도가 가장 큰 것으로 평가되었다.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.194-199
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• 2005

The principle of vortex cyclone was applied to enhance the treatment efficiency of waste air streams containing particulate matters, phenol, and others. Adsorption, condensation, and/or coagulation could be induced at low temperature zone formed by Joule-Thomson expansion as the pressurized air and pulverized activated carbon were introduced at the tangential direction into the cyclone system applied with the coaxial funnel tube of vortex cyclone. Easily condensible vapors were adsorbed and/or condensed forcibly on coagulated or condensed materials which were formed as cores for coagulation or condensation by themselves or on pulverized activated carbons. These types of coagulation or condensation rates were rapidly promoted by increase in their diameter. The maximum removal efficiency obtained from this experiment for the removal of carbon dioxide and phenol was about 87.3 and 93.8 percent, respectively. Phenol removal efficiency was increased with the relative humidities and enhanced by pulverized activated carbon added. The Joule-Thomson coefficients were increased with the pressure of air injected in the range of the relative humidities between 10% and 50%. It is believed that the moisture, particulate matters, and the pressure of the process air introduced could control the removal efficiency of VOCs.

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.535-541
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• 1996

In preparation of fine alumina powders with use of vesicle, the effect of variation of pH in extravesicular dispersion system to mechanism of precipitation and shape and size distribution of precipitate was investigated. The results of observation by TEM and turbidimeter were obtained as follows. Reaction between aluminum ion and hydroxyl ion to produce precipitate within vesicle was initiated at pH 11.4 and spherical fine precipitates, about 50 nm size, were formed at pH 12.0. About pH 12.3, size of precipitates in vesicle grew twice as great as those formed below pH 12.0 because of the agglomeration and coalescence of vesicleswith time.

• KIISE Transactions on Computing Practices
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• v.23 no.9
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• pp.535-541
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• 2017

Today, the scale of the computer software market has increased, and massive sized software has been developed to satisfy diverse requirements. In this context, software complexity is increasing and the quality of software is becoming more difficult to manage. In particular, software reuse is important for the improvement of the environments of legacy systems and new system development. In this paper, we propose a method to reuse modules that are certified by quality. Reusable levels are divided into code area (method, class, and component), project domain, and business levels. Based on the coupling and cohesion of software complexity, we propose a reusable module extraction mechanism with reusability metrics, which constructs a visualization of the "reusable module's chunk" based on the method and class levels. By applying reverse engineering to legacy projects, it is possible to identify reusable modules/objects/chunks. If these modules/objects/chunks are to be reused to develop an extension system or similar new system, we need to ensure software reliability in order to reduce the time and cost of software development.