• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.115-121
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• 2009

It is to use effectively for stream channel and watershed management as the prediction and the analysis of bed changes characteristics in the Seomjin river downstream. The necessary data (section, bed composition material, pivot point water elevation, coefficient of roughness) with regard to analysis of the bed changes characteristics were based upon the survey data and analysis results in the Seomjin river maintenance basic plan. The prediction of bed changes was also completed with HEC-6 model. The study results were summarized as follows: The main factor of bed changes in the Seomjin river downstream can be decided by extreme extraction of bed aggregate rather than the change of hydrological data. According to the analysis of bed stability based on the relation between friction velocity and representative grain size, and the relation between dimensionless tractive force and representative grain size, the Seomjin river downstream appears to be increased overall. The bed composition material in the stream channel of the Seomjin river of 2003 year shows higher composition rate of gravel and lower composition rate of sand as compared to those of 1989 year. According to result that the prediction of bed changes, it is estimated that the bed will be risen approximately 1.5 m to the place up to 9 km from the estuary, have been repetitively risen and fallen up to 1 m to the place between $9{\sim}21\;km$ section, and fallen about 0.5m to the place between $22{\sim}25\;km$ section. As a result, the bed of the Seomjin river downstream can be decided to be risen gradually. However, since the prediction of this study is based on the assumption that there will be no forced aggregate picking, the bed changes can be much greater than expected when there is a massive aggregate picking as it had happened before.

• Current Research on Agriculture and Life Sciences
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• v.4
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• pp.70-76
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• 1986

The purpose of this study is to offer the basic data of the tidal river development program by grasping the diffusion between the high density-sea water and the low density-fresh water in the tidal river. The tidal range of Hyungsan river which flows at Youngil bay in Pohang was selected to analysis the phenomenon of density current. The results obtained are as follows ; The tide of Youngil bay was one time a day, 0.104m in high tide difference and 0.085m in mean tidy difference. The change of sea level by tide was negligible. The volume of reserved water by sea water was $2,700,000m^3$ and available water of irrigation was $1,200,000m^3$ that salt density is below $750{\mu}{\mho}/cm$ out of total volume. Salt intrusion phenomenon by density current was a little water level change, however, it become a salt wedge type by the much salt invasion during the spring tide and it makes a well-mixed type by the retreating salt wedge during the neap tide. As long as there were some density differences between sea water and fresh water, net upstream flow was existed along the bottom of water way from the estuary to the upstream channel.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.6
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• pp.722-728
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• 2012

Urban sewer systems has a limitation of capacity of rainwater storage and problem of occurrence of untreated sewage, so adopting a storage facility for sewer flooding prevention and urban non-point pollution reduction has a big attention. The Korea Ministry of Environment has recently introduced a new concept of "multi-functional storage facility", which is crucial not only in preventive stormwater management but also in dealing with combined sewer overflow and sanitary sewer discharge, and also has been promoting its adoption. However, reserving a space for a single large-scale storage facility might be difficult especially in urban areas. Thus, decentralized construction of small- and midium-sized storage facilities and its operation have been introduced as an alternative way. In this paper, we propose a model predictive control scheme for an optimized operation of distributed storage facilities and sewer networks. To this aim, we first describe the mathematical model of each component of networks system which enables us to analyze its detailed dynamic behavior. Second, overflow locations and volumes will be predicted based on the developed network model with data on the external inflow occurred at specific locations of the network. MPC scheme based on the introduced particle swarm optimization technique then produces the optimized the gate setting for sewer network flow control, which minimizes sewer flooding and maximizes the potential storage capacity. Finally, the operational efficacy of the proposed control scheme is demonstrated by simulation study with virtual rainstorm event.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.73-82
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• 2017

Recently, offshore bucket cut-off walls were developed to solve several problems in conventional offshore cut-off walls. In this study, a numerical analysis was carried out to investigate the seepage stability of offshore bucket cut-off walls. The ground was assumed as uniform homogeneous sand and steady state flow conditions were applied. The flow condition was compared among 2-dimensional flow (2-D), 2-dimensional concentrated flow (2-DC), and axisymmetric flow. The analysis results showed that the seepage velocities in axisymmetric flow were about 1.5 and 2 times larger than those of 2-DC and 2-D flow conditions, respectively. Thereafter, the axisymmetric flow condition was applied because the seepage flow was concentrated toward the center of the circular-shaped wall. A parametric study was performed varying bucket radius, penetration depth, total head difference between in and outside of the wall. The exit gradient, which used for the calculation of piping stability, decreased with increase of the penetration depth and bucket radius. Design charts were proposed to estimate the factor of safety and the exit gradient at various analysis conditions. Finally, the design equation was proposed to calculate the exit gradient for the preliminary design of the bucket cut-off wall.

• Journal of the Korean GEO-environmental Society
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• v.17 no.5
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• pp.37-46
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• 2016

In order to determine the variability of environmental characteristics of lightweight air-foamed soil using marine clay according to freezing-thawing and soaking conditions, unconfined compressive strength of the lightweight air-foamed soil samples made by changing the amount of cement under curing conditions of outdoor low temperature, underground or indoor wetting were observed. Compressive strength was not increased under freezing-thawing (temperature range of $-9.1^{\circ}C{\sim}17.2^{\circ}C$) regardless of the amount of cement but the more cement using, it was increased rapidly by underground curing conditions within 30 cm beneath ground level. Therefore, it is necessary to install insulation layer cutting off exterior cold air after construction of lightweight air-foamed soil in condition of freezing-thawing. Bulk density was increased too small under the long-time soaking condition, it tended to decrease rapidly when samples were dried up and had below 6% of water contents. But variability of compressive strength and bulk density was very small for preventing drying and keeping its wet state. The lightweight air-foamed soil that installed beneath ground water level or covered by soil can be evaluated as a long-term reliable construction material.

• Journal of the Korean Association of Geographic Information Studies
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• v.5 no.1
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• pp.38-47
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• 2002

This paper demonstrates a regional analysis of landslide occurrence potential by applying geographic information system to the Kumi City selected as a pilot study area. The estimate criteria related to natural and humane environmental factors which affect landslides were first established. A slope map and a aspect map were extracted from DEM, which was generated from the contour layers of digital topographic maps, and a NDVI vegetation map and a land cover map were obtained through satellite image processing. After the spatial database was constructed, indexes of landslide occurrence potential were computed and then a few landslide-potential areas were extracted by an overlay method. It was ascertained that there are high landslide-potential at areas of about 30% incline, aspects including either south or east at least, adjacent to water areas or pointed end of the water system, in or near fault zones, covered with medium vegetable. For more synthetic and accurate analysis, soil data, forest data, underground water level data, meteorological data and so on should be added to the spatial database.

• 한국과학기술학회:학술대회논문집
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• 2008.06a
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• pp.1-34
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• 2008

본 인식 조사에서 나타난 결과와 개선 방안의 도출과 관련한 시사점을 요약하면 다음과 같다. 첫째, 국내 연구부정행위 실태는 우려할만한 수준으로 나타났다. 위조, 변조, 표절, 부당한 저자 배분, 업적 부풀림 등 연구부정행위에 대해 연구비 유용이나 횡령보다 훨씬 더 만연한 것으로 응답하였다. 연구부정행위가 발각되는 정도에 대해서는 의견이 분분하였으나 처벌의 수위는 엄격하지 않다고 생각하는 것으로 나타났다. 본인의 연구윤리 의식이 타인에 비해 높은 것으로 자부하고 있으나 부정행위 인지시의 행동에 대해서는 바람직하다고 생각하는 행동과 자신의 예상 행동 사이에 괴리를 보였고, 바람직하다고 생각하는 행동도 매우 소극적인 것으로 나타났다. 부정행위 실태 조사에서 나타난 중요한 사실은 주로 기초 연구를 수행하는 과기부/교육부 사업 수행자가 응용이나 개발 연구를 수행하는 산자부/정통부 사업 수행자에 비해 자신의 연구 분야에서 연구부정행위가 훨씬 더 만연해 있는 것으로 응답한 것이다. 둘째, 가장 심각한 연구윤리 저해 요인에 대해서는 단기간 성과의 강조, 연구 수주의 경쟁 심화, 정량적 성과 주의 등을 꼽았으며, 전체적으로 개인적/문화적 요인보다는 구조적/조직적 요인, 특히 구조적 요인이 더 중요한 것으로 인식하고 있었다. 신뢰도 분석 결과 제3장에서의 분석을 바탕으로 본 연구에서 제시한 구조적, 조직적, 개인적, 문화적 요인의 구분은 유효한 구분으로 나타났다. 대학에 비해 정출연 소속 연구자들이 구조적 요인이 연구부정행위와 더 관련이 많다고 인식하고 있었으며, 기업 소속 연구자들은 구조적 요인이나 조직적 요인과의 관련성이 더 적은 것으로 인식하고 있어 본 연구에서 제시한 여러 저해 요인들이 대학이나 정출연에 더욱 밀접한 것으로 나타났다. 개인적 요인에 대해서는 여성이나 고연령층에서 부정행위와의 관련성을 더 크게 느끼고 있었다. 셋째, 개선 방안에 대해서는 과도한 연구비의 집중 방지, 소규모 개인과제 확대, 평가의 전문성과 공정성 확보를 가장 효과적인 방안으로 인식하고 있었다. 부정행위에 대한 처벌의 강화와 양적 평가의 개선에 대해서도 효과를 높이 기대하고 있었다. 연구윤리 교육이나 상대 평가의 강화, 진실성 검증 시스템의 보완 등에 대해서는 큰 효과를 기대하지 않고 있었으나 이는 국내에서 그동안 연구윤리에 대한 체계적 교육이나 진실성 검증 시스템이 존재하지 않은 탓에 연구자들이 그 효과를 잘 인식하지 못하고 있다는 점이 고려되어야 할 것이다. 개선 방안을 크게 평가, 선정, 수행, 연구윤리의 인프라로 구분하였을 때에는 선정과 평가와 관련된 개선이 시급한 것으로 인식하고 있었다. 사업별로는 과기부/교육부 사업 수행자가 선정과 관련된 개선의 효과를 더욱 크게 느끼고 있었고 소속기관으로는 대학 연구자들이 더욱 크게 느끼고 있어, 소규모 과제의 확대와 연구비 집중 문제 해결, 경쟁 완화 등이 대학과 기초연구분야에 더욱 절실하다는 것을 나타내었다. 전체적으로 제시된 세부 항목에 대해 과기부/교육부 사업 수행자가 산자부/정통부 사업 수행자보다 효과성을 높게 보고 있는 것은 연구부정행위 실태에 대해서도 더 심각하게 인식하는 것과 맥락을 같이한다고 볼 수 있다. 따라서 본 연구에서 제안하는 여러 개선 방안들을 단계적으로 적용한다고 할 때 우선 기초연구나 개인 단위 과제 중심으로 적용하는 것이 효과성이나 필요성의 측면에서 모두 바람직한 것으로 판단된다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.3
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• pp.261-275
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• 2020

When excavating a small cross-section tunnel in a fault fracture zone using the shield TBM method, there is a high possibility of excessive convergence and collapse. Appropriate ground reinforcement is required to minimize construction cost loss and trouble due to a fault fracture zone. In this study, the optimal reinforcement area was suggested and the surrounding ground behavior was investigated through numerical analysis using MIDAS GTS NX (Ver. 280). For the parameters, the width of the fault fracture zone, the existence of fault gouge, and the groundwater level and depth of cover were applied. As a result, when there is not fault gouge, the convergence and ground settlement are satisfied the standard when applying ground reinforcement by up to 0.5D. And, due to the high permeability coefficient, it is judged that it is necessary to apply 0.5D reinforcement. There is a fault gouge, it was possible to secure stability when applying ground reinforcement between the entire fault fracture zone from the top of the tunnel to 0.5D. And, because the groundwater discharge occurred within the standard value due to the fault gouge, reinforcement was unnecessary.

• Journal of agriculture & life science
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• v.45 no.5
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• pp.97-103
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• 2011

The purpose of this study was to analyze the pollutant reduction effect for non-irrigated crop land by nonpoint source pollution control. For a field scale monitoring, 6 plots (5m width and 22m length) and 3 sediment traps were installed. At the outlet of each plot, the stage gauges were installed for runoff monitoring. For a rainfall monitoring, tipping bucket rain gage was installed within the experiment site. Through the artificial irrigation, runoff from the plots were monitored. The SS, TOC, T-N, T-P, COD, NTU of sampled water were analyzed by standard methods. The SS, TOC, T-N, T-P, COD, NTU concentration of initial runoff were 15.00, 1.54, 5.27, 0.07, 4.72, 0.45mg/L, respectively. Four hours later than the initial runoff, the concentration was changed to 1.00, 0.94, 4.06, 0.01, 0.60, 0.33 mg/L, respectively. As a result of artificial irrigation, three out of four sediment traps were filled with runoff water from the experimental plots. One sediment trap was not filled with runoff water because the artificial irrigation was not supplied for two experimental plots. The stage of sediment traps were gradually lowered. However, the water quality didn't showed a decrease trend as the stage went down because the suspended solid was not equally collected during the water sampling.

• Journal of The Geomorphological Association of Korea
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• v.19 no.1
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• pp.17-27
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• 2012

Coastal dunes help stabilize the coastal landscape and protect the hinterland through dynamic interaction with sand beaches. Sometimes dune erosion occurs during the tropical cyclones, while dune recovery may naturally follow after the event. As the typhoon Kompasu passed through the Korean Peninsula early-September in 2010, it caused a rise in water in association with the storm, wave run-ups, and heavy rains in coastal areas. As the result, coastal dunes along the west coast of Korea were severely damaged during the storm. However, the degree and extent of erosion and recovery of dunes were found to be related with the condition of beach-dune systems including gradients of foreshore and front slope of the dune, sediment supply, vegetation, wind activity, and human interferences. Some dunes retreated landward more and more after the erosional event, while others recovered its original profile by aeolian transport processes mainly during the winter season. Vegetated dunes with pine trees were less recovered after the erosion than grass-covered dunes. In addition, dunes with artificial defense were more eroded and less recovered than those without hard constructions. According to the observation after the severe storm, it is likely that the sand transport process is critical to the dune recovery. Therefore, the interactions between beach and dune must be properly evaluated from a geomorphological perspective for the effective management of coastal dunes, including natural recovery after the erosion by storm events.