• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.681-685
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• 2013

A pilot-scale sand-box experiment was performed in order to investigate the effect of cross-flow velocity on the clogging of the filter sand in a model filtration pond. The clogging phenomenon was observed during the operation with the cross-flow varied in stages in a range of 0~40 cm/sec, and the experimental result was analyzed using a numerical code. Results showed that the cross-flow velocity in this range had no influence on the development of clogging and that clogging occurred mostly on the filter-surface. It was found that while the production rate decreased from $5m^3/m^2-day$ to $3m^3/m^2-day$ the clogging coefficient of the top 50 cm layer increased up to about 30,000 sec, which corresponded to 87% of the clogging coefficient of the total 2.4 m layer. Of the clogging coefficient of the top 50 cm layer, surface clogging constituted 90% while the other 10% was intermediate clogging. It was also found that the surface clogging increased while the intermediate clogging remained constant as the operation continued, and that filtrate turbidity along the filtration depth remained constant in spite of the increase in clogging.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.5-13
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• 2007

Many construction projects adopt grouting technology to prevent the leakage of groundwater or to improve the shear strength of the ground. Recognition as a feasible field procedure dates back to 1925. Since then, developments and field use have increased rapidly. According to improvement of grout materials, theoretical study on grout penetration characteristics is demanded. Fluid of grout always tends to flow from higher hydraulic potential to lower one and the motion of grout is also a function of formation permeability. Viscosity of pout is changed by chemical action while grout moves through pores. Due to the increment of viscosity, permeability is decreased. Permeability is also reduced by grout particle deposits to the soil aggregates. In this paper, characteristics of new cement grout material that has been developed recently are studied: injectable volume of new grout material is tested in two different grain sizes of sands; and the method to calculate injectable volume of grout Is suggested with consideration of change in viscosity and clogging phenomena. The calculated values are compared with injection test results. Viscosity of new grout material is found to increase as an exponential function of time. And lumped parameter $\delta$ of new grout material to be used for assessing deposition characteristics is estimated by comparing deposit theory with injection test results considering different soil types and different injection pressures. Injection test results show that grout penetration rate is decreased by the increase of grout viscosity and clogging phenomena.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.5
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• pp.88-95
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• 1999

스테레오 정합에서 가장 중요하고도 어려운 문제는 대응점 추출 문제와 폐색 영역에 대한 처리이다. 특히 폐색 영역의 점들은 대응점이 존재하지 않기 때문에 변이 정보 획득에 많은 어려움이 있다. 이러한 문제에 대한 효과적인 접근을 위해 본 논문에서는 쌍방향 정합 알고리즘을 기반으로 폐색 영역의 정합 정도를 향상 시키는 방법을 제안한다. 즉 좌,우 영상 각각의 기준에 대해 독립적인 변이 정보를 구하고, 이를 바탕으로 정합의 타당성 여부를 검토하여 그 결과를 다음 처리에서 반영하는 상호 보완적인 반복 처리 기법을 적용하였다. 이 과정에서 구해진 폐색 영역에 대한 변이 정보는 스테레오 영상 모델의 기하학적 구조를 적용하여 좌, 우측 기준 정합에 대해 그 좌, 우측 점들의 변이 정보들로 대체함으로써 불연속점들의 무뎌짐(blurring)현상을 개선하였다. 한편, 실험 결과를 보다 객관적으로 비교하기 위해 정합율과 에러율이라는 파라메터를 정의하여 개선된 결과를 보였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.547-553
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• 2018

An integrated iron and steel mill uses a large amount of water and produces wastewater which contains various contaminants such as iron, manganese, etc. Especially, in some regions of Southeast Asia, the concentration of silica in iron and steel mill wastewater is higher than in other countries. Silica is known to be one of the main causes for fouling in the membrane processes for water reuse. In cases of high concentrations of silica in iron and steel mill wastewater, the ferrous silicate tends to be formed. This could lead to higher fouling tendency depositing on the membrane surface. Therefore we conducted a pilot test to investigate the effect of silica and iron on the fouling tendency of reverse osmosis (RO) membrane for treating two types of wastewater from an integrated iron and steel mill. In this case of treated wastewater from iron and steel mill, RO pilot plant was operated with the fluxes 15.9LMH and 18.8LMH for 112 days to investigate the fouling characteristics. The results found that the fluctuation of flux was much wider than the average flux and the minimum permeability was low at 78%. In the case of treated runoff from an integrated iron and steel mill, the average concentration of iron was lower than in wastewater. RO pilot test was conducted with the flux 18.8LMH for 46 days. The results found that runoff had a lower fouling tendency and pre-treatment using microfiltration (MF) could minimize the fouling problem of RO.

• Proceedings of the KIEE Conference
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• summer
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• pp.1100-1102
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• 2004

열팽창 방식의 가스차단기는 아크 에너지 자체를 이용하여 압력상승을 얻고, 상승된 압력을 이용하여 전류 영점 부근에서 아크 방향으로의 유동을 형성하여 아크를 소호한다. 대전류 구간에서 노즐 폐색현상이 일어나면 노즐 용삭이 크게 일어나며 용삭된 노즐 물질은 팽창실의 압력과 온도를 상승시키게 된다. 따라서 차단 특성해석을 위해서는 노즐 용삭에 의한 압력 상승해석이 필요하다. 본 논문에서는 아크에너지에 따른 노즐 용삭비를 이용하여 용삭되는 노즐량을 계산하고, 이로 인한 back flow현상을 고려한 해석 방법을 제안한다. 개발된 프로그램을 제작한 차단부 모델에 적용한 결과, 열팽창실의 압력상승치는 시험결과와 잘 일치함을 확인하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.417-422
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• 2008

With standard orthorectification algorithms, one can produce unacceptable structure duplication in the orthophoto due to the double projection. Because of the abrupt height differences, such structure duplication is a frequently occurred phenomenon in the dense urban area which includes multi-history buildings. Therefore, occlusion area detection especially for the urban area is a critical issue in generation of true orthophoto. This paper deals with occlusion area detection with visible height based approach from aerial imagery and LiDAR. In order to accomplish this, a grid format DSM is produced from the point clouds of LiDAR. Next, visible height based algorithm is proposed to detect the occlusion area for each camera exposure station with DSM. Finally, generation of true orthophoto is presented with DSM and previously produced occlusion maps. The proposed algorithms are applied in the Purdue campus, Indiana, USA.

• Smart Media Journal
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• v.5 no.1
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• pp.88-94
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• 2016

In this paper, we proposed a new object tracking algorithm based on sparse representation to handle the drifting problem. In APG-L1(accelerated proximal gradient) tracking, the sparse representation is applied to model the appearance of object using linear combination of target templates and trivial templates with proper coefficients. Also, the particle filter based on affine transformation matrix is applied to find the location of object and APG method is used to minimize the l1-norm of sparse representation. In this paper, we make use of the trivial template coefficients actively to block the drifting problem. We experiment the various videos with diverse challenges and the result shows better performance than others.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.2
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• pp.120-131
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• 2011

A pilot-scale experiment of floodplain filtration with a filtration depth of 3.6m was performed employing flood/rest type raw-water supply system in an effort to find ways to improve river water quality by additional treatments of discharged effluent from sewage treatment plant. Soil samples were taken from 3 sites including Gumi, Daegu and Gimhae along the Nakdong river. Reductions of infiltration rates following increases in operating time was investigated in each soil sample, along with the analysis of removal efficiencies of various pollutants according to different depths and infiltration rates. The results show incremental development of clogging on the soil surface with increases in operation time, and illustrate exponential decrease in the infiltration rate. The time required for the removal of the clog from the soil surface was longer than 2 weeks for all soil samples analyzed. The stable infiltration rates for soils were 5 m/day for Gumi and for Daegu and Gimhae was 1 m/day. In unsaturated soils dissolved oxygen levels increased following the increase of filtration depth, suggesting that alternating application of flood and rest for raw-water supply effectively keeps the soil environment aerobic. For all soils, the nature of pollutant removal depending on the depth of filtration remained the same regardless of the infiltration rate. Most of the BOD and turbidity were removed within 1.2 m, about 30% of COD was removed within 3.6m and was expected to be removed further with increases in filtration depth. Nitrification occurred near the surface of all soils; however there was no significant removal of nitrogen in the filtration depths tested in this study. Although removal rate of phosphorus was low for Gumi's soil, it was high enough for other soils, suggesting that the method developed in this study could significantly improve river water quality.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.557-559
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• 2015

움직임 보상 기반 프레임율 변환(Frame rate up-conversion based on motion compensation )에서 발생하는 블로킹 현상(Blocking artifact)을 줄여 영상의 화질을 높이기 위한 디블로킹 필터(De-blocking filter) 방법을 제안한다. 이 방법은 블록 단위로 동작하는 움직임 보상 과정에서 주변 블록과의 움직임이 급격히 달라지는 폐색영역에서 발생하는 블로킹 현상을 크게 줄일 수 있다. 제안하는 방법은 기존의 필터링을 하지 않는 방법보다 화질이 약 0.01db 향상하였다.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.107-116
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• 2000

In this study, the permeability reduction in the soil-filter systems due to clogging phenomenon was evaluated. An extensive research program was performed using two typical weathered residual soils which were sampled at Shinnae-dong and Poi-dong area in Seoul. Two separate simulation tests with weathered residual soil were performed: one was the filtration test(cross-plane flow test); and the other was the drainage material in the field. The compatibility of the sol-filter system was investigated with emphasis on the clogging phenomenon. The hydraulic behaviour of the soil-filter system was evaluated by changing several testing conditions. Also, experimental results of the permeability reduction are compared with the results obtained from the theoretical model which can monitor the spatial variation of the permeability with time.