• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.673-675
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• 2011

본 연구에서는 매립 구간의 길이가 유도초음파 신호 강도에 미치는 영향을 분석하였다. 유도초음파 모드 해석을 통해 가진 모드와 주파수를 결정하였으며, 유도초음파의 가진 및 수진은 경사각 입사 방식의 Pitch-Catch 법을 이용하였다. 또한, 비 매립된 배관에서 유도초음파 신호를 획득하여, 이를 기준으로 매립된 배관에서 획득한 유도초음파 신호를 분석하였다. 실험 결과 매립 구간의 길이가 유도초음파의 신호 강도에 매우 큰 영향을 미칠 뿐만 아니라, 매립 구간의 길이와 신호 강도의 변화가 선형 비례적인 관계를 보이지 않는다는 것을 확인할 수 있었다.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.95.2-95.2
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• 2010

조도계수는 자연하천의 흐름해석에 사용되는 매우 중요한 변수로서, 하천의 단면, 하상입자들의 크기 및 형상, 식생, 수로단면의 변화, 수로의 만곡, 수위와 유량 등 매우 복합적인 요소의 영향을 받는 경험적 매개변수이다. 일반 자연하천에서는 유량이 적어질 경우 하천구간 내 여울이나 보의 영향으로 수면 불연속 흐름이 발생할 가능성이 커지기 때문에 수리학적 모형을 이용하여 조도계수를 산정할 경우 계산 구간 내 수면 불연속 구간에서 부정확한 조도계수가 산정되는 한계가 있다. 따라서 본 연구에서는 여울이나 장애물이 존재하지 않는 대표하천을 선정하여 대표적인 특성을 갖는 하천에 대하여 평 갈수기 조도계수를 산정하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1946-1950
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• 2010

감조하천은 조석파의 영향으로 자연하천과 달리 매우 복잡하고 다양한 흐름특성을 보인다. 흐름이 하류에서 상류 방향으로 흐르기도 하며, 유속분포는 왜곡되어 수면 근처보다는 하상 근처의 유속이 큰 형태를 보이기도 한다. 또한 만조시 수면경사는 바다의 조위가 하천의 수위보다 높은 역경사를 보이고, 수위변화량은 조위의 변화에 따라 변동하게 되는 복잡한 흐름특성을 보인다. 이와 같은 흐름특성은 감조구간의 하상변동, 생태환경, 수질 등에 큰 영향을 미치게 되기 때문에 조사, 분석이 필요하다. 따라서 본 연구에서는 감조하천 구간에서 3차원 유속측정장비인 ADCP(Acoustic Doppler Current Profiler)로 측정된 자료 및 수위관측소의 수위자료를 활용하여 시간변화에 따른 수위변화량 및 유속분포 특성을 분석하고, 수면경사, 수위변화량 등과 유량과의 관계를 분석함으로서 향후 다양한 연구에 활용할 수 있는 자료를 제공하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1203-1213
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• 2014

The hydraulic characteristics and the patterns of riverbed change had been analysed by HEC-RAS simulation in a reach of Cheong-mi river with and without weir. The corresponding physical disturbance had been evaluated with the method suggested by K-water (2008). The occurrences of low physical disturbance score coincide with the corresponding high bed changes by weir installation. The effects of physical disturbance coincide with the patterns of riverbed change along river reach which shows riverbed change is the important factor to physical disturbance. In case of installation of additional weirs at up and down stream sections of no disturbance effect by the existing weir, no physical disturbances occur in certain sections with confirming the appearance of the similar disturbance scores between the simulation results of with and without additional weir installations. In case of installation of additional weirs at up and down stream sections of disturbance effect margins by the existing weir, physical disturbances occur at every section. In case of installation of additional weirs at up and down stream sections within disturbance effect by the existing weir, low physical disturbance scores are given at every section because of superposition of disturbance along river reach. The physical disturbance would be minimized such that the additional weir is installed with sufficient distances of no disturbance and bed change effects along river reach.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.36-42
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• 2020

In order to investigate the effect of the oxidation process on thermal properties of the pitch, the oxidized pitch was prepared by changing the oxidation temperature. Thermal properties of the pitch were analyzed using thermogravimetric analysis (TGA), and it divided into three sections as A (25~100 ℃), B (250~550 ℃) and C (550~800 ℃) by derivative thermogravimetry (DTG) graph behavior. In the A section, the was reduced because the moisture contained in the pitch was removed. In the B section, as the oxidation temperature increased, the thermal stability of the pitch is improved. Because the degree of aromaticity and molecular weight of the pitch increased with increasing oxidation temperature. In contrast, the results of the C section were shown opposite of B section. Because the introduced C-OH, C-O-C, and C=O bonds were decomposed, and the resulting oxygen compounds induced the combustion reaction of the pitch.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.4 s.23
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• pp.57-65
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• 2006

In this study, hydraulic model same as natural channel with junction area and curved reach is constructed, and after that the variation of difference of the water surface elevation at cross section in junction area is analyzed using constructed hydraulic model. In junction area, the variation of maximum water level based on downstream section is more affected in discharge ratio at upstream than downstream. The maximum water level increased as closed to junction and the peak level appeared at just downstream of junction. The slope of water elevation at cross section is affected in section shape and decreased as discharge ratio is reduce. The expressed formulas developed in the channel consist of constant curvature and section shape showed difference of 60% with measured value, but the suggested formula in this study to compute difference of water surface elevation showed difference of 10% with measured value.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.547-552
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• 2022

In this study, shape-based track management by analyzing track irregularity was studied in terms of force-based track irregularity analysis by numerical analysis of wheel-rail interaction force using by the measured vertical irregularity. The effect of the vertical irregularity of the track due to the difference in track types on the wheel-rail interaction force and the track acceleration in the connecting section of the sleeper floating track and the direct fixation track on concrete bed were analyzed. As the results of this study, the measured vertical irregularity was directly affect the vertical wheel load (the wheel-rail interaction force) and the rail acceleration, and it has been demonstrated to change consistently. In this study, the adequacy and necessity of the force-based track irregularity analysis method was verified based on the wheel-rail interaction analysis using the the measured vertical irregularity.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.203-212
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• 2011

The objective of this paper is to identify the present-day surficial sediment distribution patterns of the tidal river, Gongneungcheon, through the grain size and statistical analysis. Four major findings of this study are as follows; First, the composition of sediments over the study area are mainly silt in texture. Second, the surficial sediment distribution reveals that grain size becomes coarser as they approach seawards not only in summer but also in winter. It can be concluded that tidal flows play a significant role, especially in winter, in the distribution of surficial sediments in Gongneungcheon. However, samples obtained in summer were relatively small in mean size and showed better sorting compared to those obtained in winter. Third, the mean sizes of the samples on the transects decrease as the distance from the channel increases. Finally, the artificial structure such as a floodgate affects the distribution of the sediments.

• Tunnel and Underground Space
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• v.34 no.4
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• pp.283-300
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• 2024

Due to the revitalization of urban development, the number of cases of excavating tunnels adjacent to existing subways is increasing. This may affect the structure and track of the existing subway, resulting in reduced stability and usability. In this study, we verified the adequacy of the proximity evaluation range to ensure the stability of new tunnels and existing subways when excavating adjacent to tunnels, and proposed a quantitative correction rate considering various conditions. Conditions for applying the correction rate considered rock grade, geologically weak section, structurally weak section, and structural deterioration section. It is hoped that a more accurate proximity evaluation will be performed by applying a quantitative correction rate that considers rock and geological conditions, structure status, etc. to the proximity evaluation standard.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1924-1928
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• 2009

다중패커시스템은 격리된 어느 특정 구간의 지하수를 채수할 수 있으며 그 구간의 온도, 압력 등의 자료를 연속적으로 관측할 수 있어 이를 통해 각 구간별 수리전도도를 구할 수 있다. 심도별 수직적 지하수두는 지상에서 연결 롯드를 통해 압력 측정 센서를 해당 심도까지 내려 롯드에서 설치된 압력 측정용 장비에서 관측할 수 있으며, 다중패커시스템을 이용한 수리시험으로는 양수시험, 순간충격시험, 간섭시험 등이 있는데, 본 논문에서는 순간충격시험을 이용한 결과를 제시하였다. 도출된 구간별 수리전도도를 다중패커시스템을 설치하기 전 나공에서 이중 패커를 이용한 정압주입시험의 결과와 비교하여 보았다. 다중패커시스템을 통해 획득된 심도별 지하수두는 정수두 (hydro-static)상태의 일정한 경향성이 없이, 각 심도에 존재하는 투수성 구조에 영향을 보이고 있음을 알 수 있었으며, 이는 다수의 관측공을 통해 수평 방향의 수리경사를 산출함에 있어 관측공의 심도에 대한 충분한 고려가 있어야 한다고 판단된다. 또한, 다중패커시스템을 이용한 수리시험 결과를 나공 상태에서 이중 패커를 이용한 정압주입시험 결과에 대해 심도별 도출되는 수리전도도가 국지적으로 분포하는 투수성 구조에 영향으로 인해 투수량계수 (transmissivity)로 환산한 유효 투수계수로 비교하여 결정질 암반의 수리 특성으로 제안하는 것이 타당한 것으로 분석되었다.