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Simulation of non-steady state oxygen transfer caused by microbubble supply
Jaiyeop Lee,Ilho Kim 대한상하수도학회 2018 상하수도학회지 Vol.32 No.5
Microbubbles oxygen transfer to water was simulated based on experimental results obtained from the bubbles generation operated under varying liquid supply velocity to the multi-step orifices of the generator. It had been known that liquid supply velocity and bubble size are inversely related. In the oxygen transfer, a non-steady state was assumed and the pseudo stagnation caused the slow movement of bubbles from the bottom to the water surface. Two parameters were considered for the simulation: They represent a factor to correct the pseudo stagnation state and a scale which represented the amount of bubbles in supply versus time. The sum of absolute error determined by fitting regression to the experimental results was comparable to that of the American Society of Civil Engineers (ASCE) model, which is based on concentration differential as the driving force. Hence, considering the bubbles formation factors, the simulation process has the potential to be easily used for applications by introducing two parameters in the assumptions. Compared with the ASCE model, the simulation method reproduced the experimental results well by detailed conditions.
Reduction Effects of Shaped Noise Barrier by Composition with Adsorbed Filter Panel
Jaiyeop Lee,Hyundong Lee,Ilho Kim 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.12
The functional soundproof wall is composed of a sound absorption panel with a filter function and flat panel for the top, a zigzag-shaped soundproof panel whose effects were verified through simulation, and a flat panel for the bottom. The functional soundproof wall is 2 m wide and 2 m high, and it will be installed upright up to 1.5 m, forming the bottom, and will then be tilted by 30º from 1.5 m, forming the top. Noise will be generated at the distance of 2 m, 3 m and 4 m from the functional soundproof wall, and the measured noise will be classified into reflected sound and diffracted sound. The reflected sound will be measured for each height from 1 m, 2 m, 3 m and 4 m at the distance of 6 m, while noise measured in front of the soundproof wall will also be collected. The experiment result showed that there was a noise reduction effect by approximately 4 dB according to the composition. In terms of composition, the soundproof wall composing of the sound absorption panel and the shaped soundproof panel showed excellent reflected sound reduction effects, while the soundproof wall consisting of the filter showed overall excellent noise reduction effects. On the other hand, reflected noise and diffracted sound reduction effects of the shaped soundproof wall were shown clearer as the distance from the noise source was longer, especially at the distance of 4 m. The composed soundproof wall was effective for reducing reflected noise and diffracted sound. More importantly, the composition of the sound absorption panel and the shaped soundproof panel showed excellent reflected noise reduction effects, while in the case of composing with only the shaped soundproof panel, the reflected noise reduction effects began to be shown from 4 m from the noise source. Therefore, it is expected that the relevant soundproof measures can be used in the field effectively.
Analysis of highway reflection noise reduction using transparent noise barrier types
Jaiyeop Lee,Ilho Kim,Seoil Chang 대한환경공학회 2015 Environmental Engineering Research Vol.20 No.4
Transparent type noise barrier is a desirable facility since it provides a secure view to drivers and passengers. However, reflection from this type of barrier could annoy dwellers on the sides of the road. To reduce reflection noise by transparent type barrier, modification can be made to the shapes on the front side and hence get effects by distortion of sound transmission. To achieve this, we have conducted simulation by which the effects of patterned screens of noise barrier on high-ways were investigated. The reduction effects of reflected sounds were evaluated for swelling, swelling with curved, rectangular and V-shaped screen type barriers, compared to the planar panel. The emitting noise was generated by 6-lane road and the patterned noise barriers had shown the reduction effects, especially in swelling and swelling with curved type for middle height dwellers, and the V-shaped screen type for higher elevation dweller. The swelling-type showed a decrease of 0.7~1.2 dB, performing the best diminution effect among the tested noise barriers.
정체수역 수질개선 및 합성곱 신경망 모델을 이용한 모니터링에 관한 연구
이재엽 ( Jaiyeop Lee ),김일호 ( Ilho Kim ) 한국수처리학회(구 한국수처리기술연구회) 2020 한국수처리학회지 Vol.28 No.5
In this study, the concentration of dissolved oxygen (DO) at different water depths in a small river connected to the Nakdong River was monitored with parallel jet streamer device to improve water quality. DO probes were installed in correspondence of the upper, middle, and lower sections of the river at the different depths and operated for 2 months. To determine the stagnation of water in the river, we produced DO graphs for different depth intervals. Overall, we prepared 343 graphs, identifying 7 intervals with characteristic dissolved oxygen concentrations, including a stagnant zone. We separately applied an artificial neural network (ANN) and a convolution neural network as learning models: in the first case, a correct answer rate of only 29.2% was obtained from the derived weight and bias, while in the second case it corresponded to 94.5%. The learning graphs were randomly selected from 40 to 300. The correct answer ratios were 94.8%, 91.3%, and 88.6% for 250, 200, and 50 graphs, respectively. By applying the control logic to the actual monitoring results, we decided to label as a “stagnant region” the depth interval characterized by correct answer ratios comprised between 84.9% and 83.5% (i.e., depths between 30 m and 60 m).
이재엽(Jaiyeop Lee),김일호(Ilho Kim) 한국도로학회 2015 한국도로학회논문집 Vol.17 No.5
PURPOSES : The noise, which is typically generated by fast moving vehicles, can be intercepted by installing a noise barrier with a soundproof panel. However, reflections from the panels cause secondary noise, and hence lower the effectiveness of the panels. In this study, the reduction of reflection noise by considering the shape, especially zigzag one, of the soundproof panel have been evaluated. METHODS : The simulation model used in this study was Nord2000, which simulates real-road situations effectively. Based on the simulation results, the joining angle of 133。with the pattern width (a) equal to 2 m and the projection height (b) equal to 0.5 m was adapted in the zigzag shape as the best profit designing factors. RESULTS: The measuring results at middle height, 15 m showed reduction at all points except the point with average -1.6 ㏈. At a greater height of 30 m, 2 points showed reduction. A real-sized facility was constructed to investigate the reflected sound from a zigzag shaped panel up to the height of 5 m. CONCLUSIONS: The reduction effects were detected in all the receive points in the range of 2-6 m distances and 1-5 m heights comparing the plane panel. Compared to plane panel, the noises are reduced at an average of 2.4 ㏈A.