• Journal of Industrial Technology
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• v.21 no.B
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• pp.11-20
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• 2001

This laboratory study examined the impact of free chlorine residual and pipe material on the formation of biofilm in drinking water distribution pipe surfaces. Result of heterotrophic plate counts(HPC) of the biofilm in the tap water-supplied reactor averaged $2.17{\times}10^5CFU/cm^2$ on PVC and $2.43{\times}10^5CFU/cm^2$ on STS 316, respectively. HPCs on the surface exposed to the tap water containing 0.2mg/L of free chlorinne residual averaged $4.24{\times}10^4CFU/cm^2$ on PVC and $6.54{\times}10^4CFU/cm^2$ on STS 316, respectively. Average of HPC/Total direct counts in the tap water-supplied reactor ranged from 1.08%(PVC) to 1.26%(STS 316) and from 0.38%(PVC) to 0.65%(STS 316) in the reactor supplemented with disinfectant, respectively. No correlation was observed between disinfectant addition and biofilm density. With regard to the biofilm formation, little difference existed between PVC and STS 316. Yellow and red pigmented bacteria were the dominant expressions in bulk fluid, whereas non-pigmented bacteria were found dominant in the biofilm. Pink/red pigmented bacteria were found to be facultative anaerobic, while yellow pigmented bacteria and non-pigmented bacteria were found to be obligate aerobic.

• Journal of Life Science
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• v.14 no.6 s.67
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• pp.891-894
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• 2004

The effect of pipe materials on biofilm communities were investigated by CLPP (community level physiology profile) using Biolog GN plates. Heterotrophic bacterial concentrations were $10^4\;-\;10^6\;CFU/cm^2$ and there was no differences between galvanized iron and carbon steel. Average optical density of Biolog plate was similar between two pipe materials. However, CLPP was different according to the type of pipe materials and exposed times to tap water, and CLPP was independent of bacterial concentration. This represents the differences of bacterial communities with pipes and water contact times.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.54-58
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• 2002

This study investigates a relationship between fracture mechanics parameters (Stress Intensity Factor Range: ΔK, Maximum Stress Intensity Factor; Kmax) and X-ray parameters (residual stress:$\sigma$r half-value breadth: B) for SG365 steel at elevated temperature up to 30$0^{\circ}C$. The fatigue crack propagation test were carried out and X-ray diffraction technique according to the direction of crack length was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase at low ΔK region, to reach a maximum value at a certain value of Kmax or ΔK and then to decrease. Residual stress was independent of stress ratio by arrangement of ΔK and half value breadth were independent of the arrangement of Kmax. The equation of $\sigma$r-ΔK was established by the experimental data. therefore, fracture mechanics parameters could be estimated by the measurement of X-ray parameters.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.194-194
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• 2021

최근 지구온난화 및 이상기후 현상으로 인하여 집중호우의 빈도와 강도가 급증하고 있다. 그리고 급격한 도시화로 불투수 면적이 증가하여 도시지역에 침수피해가 빈번하게 발생하고 있는 실정이다. 이러한 침수피해를 방지하기 위하여 침수위험지구, 재해위험지구를 선정하여 집중호우에 대하여 집중관리를 하고 있지만 위험지구이외의 곳에서 침수가 발생할 경우 신속하게 대처하지 못하는 문제가 발생하고 있다. 또한, 하천이 범람하여 발생하는 외수침수의 경우 수위를 실시간으로 확인할 수 있어 미리 대응이 가능하지만, 내수침수의 경우 지하에 매설되어 있는 관로의 상태를 확인할 수 없기 때문에 순간적으로 발생하는 침수에 대하여 신속하게 대처를 해야 한다. 현재 침수 피해를 신속하게 대처하기 위하여 CCTV를 활용해 침수의 발생여부를 모니터링 하고 있지만 CCTV설치 지역에 비하여 적은 인력으로 모든 CCTV를 확인하지 못하여 침수피해를 신속하게 대처하지 못하고 있는 실정이다. 본 연구에서는 침수사진 자료를 CNN(Convolutional Neural Network)기법을 이용하여 학습시켜 침수의 발생여부를 판단하는 모델을 제안하였다. 딥러닝 기법의 CNN은 이미지의 특징을 추출하여 학습하는 과정을 가지게 되는데 학습이 완료된 모델은 침수사진의 특징을 파악하여 침수가 발생하였는지에 대한 여부를 자동적으로 판단하게 된다. 본 연구결과를 CCTV관재센터 혹은 지자체와의 연계를 통하여 침수의 발생여부를 자동적으로 판단해주는 시스템이 개발된다면 신속한 침수피해 대처가 이루어 질 수 있을 것이라 판단된다.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.51-57
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• 2011

The calcium hydroxide($Ca(OH)_{2}$) which is flowed into the deteriorated tunnel by groundwater is reacted with carbon dioxide($CO_{2}$) and the vehicle's exhaust gas ($SO_{3}$). So its by-products are precipitated at the drainage pipe and these cause the drainage clogging. Most by-products are composed of $CaCO_{3}$ with calcite from a chemical experiment. The purpose of this study is mainly focused on comparison of attachment on each material of drainage pipe (teflon-coated steel pipe, silicon-Oil coated pipe, acrylic pipe and PVC pipe). The test was progressed to disembogue the CaO aqueous solution and tunnel outflow into each of the pipes. The experimental results show that the most produced scale pipe is PVC material and the followings are Acrylic pipe, Silicon-Oil coating pipe and Teflon coating pipe. But the long-term test results showed that teflon-coated steel pipe had a problem with durability because soil which was contained in the tunnel outflow occurred detachment of coating and corrosion of the steel pipe.

• Korean Journal of Microbiology
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• v.49 no.4
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• pp.313-320
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• 2013

Biofilm formed on stainless and copper in water treatment plant was investigated for sixteen weeks. Biofilm reactor was specially designed for this study. It was similar to that of a real distribution pipe. Raw water, coagulated, settled, filtered and treated water were used in this study. The average number of heterotrophic bacteria counts was $1.6{\times}10^4CFU/ml$, $5.8{\times}10^3CFU/ml$, $1.8{\times}10^3CFU/ml$, $1.3{\times}10^2CFU/ml$, 1 CFU/ml, respectively. Density of biofilm bacteria formed on stainless and copper pipes in raw, coagulated and settled water increased above $2.9{\times}10^3CFU/cm^2$ within second weeks while more biofilm bacteria counts were found on the stainless pipe than on the copper pipe. In case of filtered water (free residue chlorine 0.44 mg/L), there was no significant difference in the number of biofilm bacteria on both pipes and biofilm bacteria below $18CFU/cm^2$ were detected on both pipe materials after fifth weeks. Biofilm bacteria were not detected on both pipe materials in treated water (free residue chlorine 0.88 mg/L). According to the results of DGGE analysis, Sphingomonadacae was a dominant species of biofilm bacteria formed on the stainless pipe while the copper pipe had Bradyrhizobiaceae and Sphingomonadaceae as dominant bands. In case of filtered water, a few bands (similar to Propionibacterium sp., Sphingomonas sp., Escherichia sp., and etc.) that have 16S rRNA sequences were detected in biofilm bacteria formed on both pipes after fifth weeks. Stainless pipe had higher species richness and diversity than the copper pipe.