• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.119-124
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• 2004

Experimental study was conducted to characterize the flow effect of particle migration in a microchannel which can be used to deliver small amount of liquids, drugs, biological agents and particles in microfluidic devices. Fluorescent particles of $1\{mu}m$ diameter were used to obtain velocity profiles of the fluid in which large particles of $10\{mu}m$ diameter were suspended at different volume fraction of 0.6 and $0.8\%$. Measurements were obtained by using micro-PIV system which contains a Nd:YAG laser with a light of 532-nm wavelength, an inverted epi-fluorescent microscope and a cooled CCD camera to record particle images. The volume fraction of $\phi$ and the particle Reynolds number $Re_p$Rep were used as a parameter to assess the influence of the velocity profile of the suspensions. To expect the slip velocity between the particle and fluids, experiments were carried out at low volume fraction. It was shown that the velocity profile was not influenced by Rep but influenced by the volume fraction, which is in similar trend with the previous study.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2001년도 Proceedings of the 3rd Annual Meeting of Yellow Sea Environment
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• pp.1.1-5
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• 2001

High SPM concentrations(199.8~249.4${\mu}{\textrm}{m}$/㎥) were detected in the west Korea during the Yellow Sand Periods, 2000. Majority of the total SPM were composed of about 5${\mu}{\textrm}{m}$ sized coarse particles over the periods. However, fine particles sized about 1 ${\mu}{\textrm}{m}$ and coarse particles sized about 5-6${\mu}{\textrm}{m}$ showed peaks at the graph of SPM size distribution in the Non Yellow Sand Period. Airborne fungal spores at the SPM samples were cultured and identified. Full-grown colonies during the Yellow Sand Periods, Fusarium, Aspergillus, Penicillium and Basipetospora are hyphomycetes in the division Fungi imperfecti(Deuteromycota). And morphologically more diversified mycelia of hyphomycetes were grown on the sample captured from 1.1~2.1${\mu}{\textrm}{m}$ sized SPM than on other sized samples during the Yellow Sand Period. But no mold was observed on the sample of 1.1~2.1${\mu}{\textrm}{m}$ sized SPM in the Non Yellow Sand Period. It was thought that several sorts of fine sized fungal spores were suspended in the atmospheric environment of the west Korea during the Asian dust episodes.

• 한국해양환경ㆍ에너지학회지
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• 제6권4호
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• pp.67-82
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• 2003

해양, 하천, 호수 등에서 퇴적물 수송과정을 모의할 수 있는 2차원 모형을 수립하였으며, 홍수시 대청호로 유입되는 입자성 오염물질의 이동경로를 파악하기 위하여 부유퇴적물 이동-확산 모델링을 시도하였다. 또한, 복잡한 지형을 가진 대청호의 흐름특성을 파악하고, 퇴적물 수송모형의 입력자조로 이용하기 위하여 2차원 흐름모델링을 수행하였다 홍수시 모의된 수위변화는 관측결과와 일치하는 양호한 계산결과를 보였다. 평상시는 유속이 5 cm/sec이하였으나, 최대유량이 3,852 CMS에 달하는 홍수시 대청호 유입수로에서 최강유속은 최대 약120 cm/sec까지 증가하였다 대청호로 유입되는 세립질 부유사는 홍수시는 대청댐까지 강한 유속에 의해 도달하나 유속이 약한 평상시에는 대청댐까지 도달하지 못하고 대부분 유입수로에 침전하였다 모의결과는 대청호 수질관리대책을 수립하는데 기초자료로 활용될 수 있을 것이다.

• 대한환경공학회지
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• 제36권2호
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• pp.84-95
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• 2014

최근 미국과 일본을 중심으로 높은 공극과 압축성이라는 장점을 지닌 압축성 섬유여재 여과에 대한 다양한 기술이 개발되면서 이를 이용한 집약적 하 폐수 처리에 대한 관심이 높아지고 있다. 이에 따라 본 연구에서는 다양한 유입수질의 하수에 대하여 압축성 섬유여재 여과의 적용성을 검토하고자 하며, 해당 유입수에 대한 최적의 운전조건을 도출하고자 한다. 이를 위하여 예비 실험으로서 추적자 시험을 진행하였으며, 이를 통하여 다양한 압축률 및 여과율에서의 여과 양상을 검토하였다. 그 결과 높은 압축률에서 높이에 따라 다른 공극률이 적용되어 이론적인 결과값과의 뚜렷한 차이를 관찰할 수 있었다. 하수처리장의 침사지 유출수를 대상으로 다양한 압축률 조건에서 압축성 섬유여재 여과의 TSS 제거 및 제거 입자크기분포를 살펴본 결과, 압축률 30%가 최적의 운전조건으로서 제거효율 70% 이상을 나타냈으며, 작은 크기의 입자 제거율 증대를 위해 최소 15% 이상의 압축률이 요구되었다. 또한 여과 유출수 농도의 주요 영향인자인 $10{\mu}m$ 이하 입자의 제거 효율을 증대시키기 위해서는 응집과 같은 추가 공정이 필요하다고 판단되었다. 모델링 결과를 통하여 압축률이 증가할수록 여과 초기에 입자 크기에 따른 TSS 제거효율이 두드러지게 나타남을 관찰하였고, 유입수의 입자크기분포에서 가장 큰 비율을 차지하는 $10{\mu}m$ 크기 입자를 대상으로 높이에 따른 모델링 결과 높이 150-300 mm 여재층이 해당 입자 크기에 대하여 가장 활발한 여과 작용을 나타내었다.

• 대한기계학회논문집
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• 제15권1호
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• pp.252-261
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• 1991

본 연구에서는 2상 횡분류의 평균 유동특성을 비교적 정확히 예측할 수 있는 방법을 제시하는데 있다. 이를 위하여 2상 기체 분류속에 유입되는 자유흐름의 질량 유입을 Keffer와 Baines의 유입함수를 이용하기로 하며, 입자와 기체분류사이의 궤적 이탈을 고려하기로 한다. 이런 모델을 이용하여 2상 횡분류의 분출초기의 입자와 기 체분류의 속도비(particle to gas velocity ratio at the jet exit)가 유동에 미치는 영향을 알아보고자 한다.

• 대한기계학회논문집B
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• 제39권10호
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• pp.805-815
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• 2015

본 연구에서는 외부에서 균일한 직류전기장이 벽과 평행하게 인가될 때 점성유체 안에 자유롭게 잠겨있는 한 쌍의 입자들이 근처의 비전도성 평면 벽과의 상호작용 때문에 유발되는 2차원 유전영동 운동에 대하여 수치연구를 수행하였다. 해석 결과 운동 특성은 입자들이 가지는 전기전도도 부호 조합과 입자들과 벽 사이 간격에 따라 크게 달라졌다. 두 입자가 서로 같은 전도도 부호를 가지면 입자들은 공전을 하다가 최종적으로 전기장과 평행하게 정렬한다. 반면에 서로 다른 부호를 가지면 입자들은 반대방향으로 공전하다 결국 전기장과 수직하게 정렬한다. 동시에 입자들은 전도도 조합과 무관하게 반발력을 받아 벽으로부터 멀어지는 쪽으로 이동한다. 입자들이 벽으로부터 멀리 떨어져 있을수록 입자들과 벽 사이 유전영동 상호작용 효과는 서서히 사라지며 대신 입자와 입자 사이 효과가 점점 두드러진다.

• 자원환경지질
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• 제32권3호
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• pp.307-315
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• 1999

Four organic polymers were mixed with mothmorillonite. Two cationic polymers a hi로 molecular weight polyacrylamide (494C) and a low molecular weight polymer (587C).Two anionic polymers include a high molecular weight polymer (aerotil). Each clay supension series were allowed to stand for 24 hours and were centrifuged, and the clay plugs were washed and dried. The dried samples investigated by XRD, IR and CEC measurement. The suspended clay containing anionic polymers was not flocculated at any concentratuons of polymer. But the suspendions containing two cationic polymers were rapidly flocculated at almost all concentrations. the d(001) spacings of Na-montmorillonite after being with cationic polymer 587C show about 15$\AA$ suggesting the polymers may have entered the interlayer spaces. The polymer 494C-treated sample produced double peaks of about 12 and 15$\AA$ in XRD. It indicates that the high molecular weight polymer. And cationic polymer 494C may be adsorbed mainy on the outside surface of clay, and some polymers may peretrate into olny interlayers in the margin of montmorillonite particles because of its high molecular weught. CEC of polumer 587-treated sample was reduecd mmarkedly suggesting polymer blocks CEC sites. The d(001) spacings of Ca-montmorillonite after being treated with cationic polymers show about 15$\AA$ suggesting that the interlayer spaces have not been expanded. In the experiment using a dilute Ca-bearing solution, the suspended caly containinf anionic polymers was flocculated. The results indicate that the flocculation behavior of montmorillonite-polymer supension depends on not only polymer properties such as concentration, electric charge and molecular weight but also compositions of solvent.

• Environmental Engineering Research
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• 제21권4호
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• pp.427-435
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• 2016

In this study, change in water-dissolved oxygen (DO) was analyzed under various synthetic water qualities and nanobubbles (NBs) application conditions, such as gas type, initial DO as well as water dissolved, suspended and organic matters contents. When oxygen, rather than air, was introduced into nitrogen-desorbed ultra-pure water, the stagnation time was significantly increased. It took ten days for DO concentration to drop back to saturation. The higher the initial DO concentration, the longer particles were observed above saturation due to particle stability improvement. The oxygen mass transfer rate of 0.0482 mg/L/min was found to reach a maximum at an electrolytic concentration of 0.75 g/L, beyond which the transfer rate decreased due to adsorption of negative ions of the electrolyte at the interface. High levels of turbidity caused by suspended solids have become a barrier to dissolution of NBs oxygen into the water solution, and thus affected the transfer performance. On the other hand, by applying NBs for just an hour, up to 7.2% degradation of glucose as representative organic matter was achieved. Thus, NBs technology would maintain a high DO extent for an extended duration, and thus can improve water quality provided that water chemistry is closely monitored during its application.

• 한국환경보건학회지
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• 제34권2호
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• pp.148-152
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• 2008

Coated filters were developed to replace the glass impinger methods that use reagent solutions. The purpose of this study was to simultaneously measure nitrogen dioxide ($NO_2$) and respirable suspended particles (RSP) by a filtration method with a cyclone connected to a pump. A first pre-filter for RSP and second filter for $NO_2$, which was soaked in a TEA (Triethanolamine) solution, were loaded into a filter cassette with a pump flow rate of 1.7 l/m. After sampling, the TEA soaked filter was removed from the cassette, placed in a large test tube (10 ml), mixed, and allowed time to develop. The absorbance (abs) of the diazo compound of the $NO_2$ and N-(1-Napthylethylenediamine dihydrochloride) in the color reagent was measured at 545 nm on a spectrophotometer. The collection efficiency(%) of $NO_2$ by each 3 filter soaked in TEA solution and used in the cyclone with a pump flow rate 1.7 l/m was $89{\pm}3%$ and the correlation coefficient between the true $NO_2$ concentration and that determined by the TEA soaked filters was 0.993(p<0.001).

• 한국농공학회지
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• 제44권4호
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• pp.62-74
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• 2002

The purpose of this study is to find the variation of sedimentation patterns before Saemangeum reclamation. Residual flow before Saemangeum reclamation was calculated diagnostically from the observed water temperature and salinity data in May 1992 by the Marine Development Institute of Kunsan National University and wind data which were obtained from spring 1969 through winter 1977 by the Gunsan Meteorological Observatory. Three dimensional movements of injected particles due to currents, turbulence and sinking velocity are tracked by the Euler-Lagrange method. Calculated sedimentation patterns of riverine materials are highly similar to the observed ones. When suspended sediments with the size of soil grain of 60 ${\mu}m$ are injected from the Mangyeong River, their dispersion range of sediment is about 25km for 24 hours after the injection, while about 35km for 72 hours after the injection. When suspended sediments with the size of soil grain of 200 ${\mu}m$ are injected, their dispersion range of sediment is about 18km for 24 hours after the injection, while about 21km for 72 hours after the injection.