• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.8-16
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• 2009

The holistic inversion approach for frequency domain airborne electromagnetic data has previously been employed to simultaneously calibrate, process and invert raw frequency-domain data where prior information was available. Analternative formulation has been developed, which is suitable in the case where explicit prior information is not available. It incorporates: a multi-layer vertically-smooth conductivity model; a simplified bias parameterisation; horizontal smoothing with respect to elevation; and cluster computer parallelisation. Without using any prior data, an inversion of 8.0 million data for 3.4 million parameters yields results that are consistent with independently derived calibration parameters, downhole logs and groundwater elevation data. We conclude that the success of the holistic inversion method is not dependent on a sophisticated conceptual model or the direct inclusion of survey-area specific prior information. In addition, acquisition costs could potentially be reduced by employing the holistic approach which largely eliminates the need for high altitude zero-level measurements.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.375-384
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• 2002

This study is to suggest a method to estimate the design low-flow based on the runoff hydrology. The recession time model to transform a return period into the recession time is derived under the similarity between dry spell and low-flow runoffs event. The proposed recession model can be applied to the gaging station and the ungaged outlet. This recession time model contains the parameters: for climate conditions, watershed characteristics, and runoff characteristics etc. And the recession model is composed of the parameters which are initial discharge and recession constant. This model is applied to the Yongdam gaging station and the other temporary gaging station. Consequently, it is proved that this model can be used for an alternative practice to estimate the design low-flow at the gaging station with short-term runoff data or the ungaged outlet.

• Journal of Korea Water Resources Association
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• v.47 no.1
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• pp.49-62
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• 2014

As the Urban area grows and more land is developed both within the city and in surrounding areas, hydrologic functions of the natural water cycle are altered. Urbanization creates impervious areas that negatively impact stormwater runoff characteristics. these changes to the natural hydrologic cycle result in the increased flooding, decreased groundwater recharge, increased urban heat island effects. Finally, the land use and other activities result in accumulation and washoff of pollutants from surface, resulting in water quality degradation. Therefore, in this study, evaluating and quantitative analysis of the percolation effect through infiltration experiment of permeable pavement, which is one of the ways that can reduce the problem of the dry stream. Also the SWMM model is used to study the effect of the hydrologic cycle for permeable pavement block contribution.

• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.27-35
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• 2010

The structures built under the groundwater level are affected by the buoyancy force, which is hydrostatic pressure in the up direction. Recently, buoyancy-resistant anchor method has been applied in many cases of the construction of the important structure of large size, which is built under the groundwater level so that it takes high uplift pressure. Even if the construction cost of the method is very high, it surely increases the safety rate. However, the diagnosis of the performance of the buoyancy-resistant permanent anchor and the investigation of resistance mechanism are still insufficient. Especially, the long-term behavior of the anchor has not been studied well due to the difficulty in observation procedure. The contribution of this paper is the establishment of reasonable design methodology. We have measured anchor axial forces for 10 years after the construction, by using an automated measurement and a manual measurement by establishing a load cell in anchor head. Through the data collected from the measurements, we analyze the construction-step behavior of the anchor according to the self-weight variation of the building and the long-term behavior (i.e. movement within 10 years after the construction) of the anchor according to the passage of time.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.845-852
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• 2007

An OWC-type Wave Energy Conversion passes through 3 steps energy conversion process. This paper deal with the impulse turbine with staggered blade to improved performance by numerical analysis using commercial CFD code, FLUENT Maximum value of axial airflow velocity during exhalation is higher than that during inhalation This paper deal with special-type of Impulse Turbine so-called "Staggered Blade" for more efficiency to making air flow direct to on pressure side. Also, this paper has proposed special-type turbine with self-pitched blade more efficient.

• Journal of Soil and Groundwater Environment
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• v.6 no.3
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• pp.93-106
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• 2001

The processes and rates of groundwater recharge were studied by long-term monitoring of groundwater level and isotopic compositions of precipitation, surface water and groundwater in the Yeosu area. The isotopic compositions of surface water and groundwater were directly related to the precipitation event. It is also shown that the minimum amount of precipitation for infiltration to groundwater is about 20mm. The isotopic variations of groundwater shows that the Isotopic composition of groundwater changed by each precipitation event between June and Sep. 2000 is gradually changed without input of precipitation again. It indicates that the groundwater recharged from the upper part is mixed with the groundwater in reservoir. The infiltration rate of first precipitation event after a dry season is estimated to be 16.5% using isotopic mixing equations. It is expected that the groundwater recharge rate could be estimated more quantitavely, if the isotopic method is combined with the conservative methods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1043-1050
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• 2014

An air-core vortex is generated during draining after stirring a rotating cylindrical tank or after filling it with water. The formation of the air-core vortex and the time of its formation are dependent on drain conditions such as the dimensions of the tank, the initial rotation or stirring speed, and the shape of the drain port. In this study, a draining process using a two-stage drain port was numerically investigated. The length and radius of the first drain stage located in the lower part of the drain port were kept constant, whereas the radius of the second drain stage was varied for simulating the draining process. The simulation was conducted by considering an axisymmetric swirling flow for all cases. The declining water level was monitored by an interface capturing method. Further, the effects of the radius of the second drain stage on the time of formation of the air-core vortex and the internal flow structure were investigated.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.23-23
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• 2016

우리나라의 댐저수지는 홍수기에 상류로부터 다량의 부유물이 폐기물 등과 함께 일시에 유입되어 미관을 해치거나 상수원 수질을 악화시키는 등의 문제점을 가지고 있다. 이에 부유물의 하류확산을 방지하고 수거와 처리를 효율적으로 하기 위한 부유물 차단망이 설치되어 운영 중이다. 부유물 차단망의 설치위치는 저수지내의 흐름을 고려하여 부유물을 가장 효과적으로 차단할 수 있는 지점을 선정하여야 하나, 저수지 흐름을 고려하지 않고 설치될 경우 차단망이 빈번하게 훼손되거나 부유물이 적절하게 포집되지 못한 채 상류에 흩어지는 결과를 초래하기도 한다. 본 연구에서는 대형저수지인 소양댐과 신규 중소규모 댐인 영주댐의 부유물 차단망 최적 설치위치를 선정하기 위하여 3차원 모형을 이용하여 다양한 조건에서의 저수지내 흐름분포와 수리적 특성을 검토하였다. 적용모형은 3차원 수리동력학 모형인 ELCOM 모형을 적용하였으며, 홍수기 표면 유속장 분포, 수직수온분포 및 밀도류 발생지점 등을 종합적으로 분석하여 최적 설치지점을 검토하였다. 시뮬레이션 조건은 200년 빈도 홍수 유입에 대해 초기 수위에 따른 영향을 고려하기 위하여 갈수위, 풍수위 등으로 구분하여 분석하였다. 분석결과, 소양댐의 경우 기존 설치위치에서는 plunging point가 설치지점보다 하류에 위치하여 부유물 포집 기능에는 이상이 없으나 최대유속이 2 m/s를 초과하는 것으로 나타나 안정적 운영을 위하여 이전 설치하는 것이 적합할 것으로 판단되었다. 또한 신규댐인 영주댐에서는 다양한 시나리오에 대하여 분석한 결과 2개 지점이 적합한 것으로 분석되어 적치장 위치 등을 종합적으로 고려하여 최적위치를 선정하도록 하였다. 이와 같은 연구 결과는 부유물 차단망 설치설계기준 등에 반영되어 과학적인 댐 운영관리에 활용될 것으로 판단되며, 향후 보다 안정적인 시설물 관리에 기여할 수 있을 것으로 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.67-67
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• 2016

최근 기후온난화로 인한 이상기후와 지진의 발생가능성으로 인해 직렬 혹은 병렬로 위치한 2개 이상의 댐(저수지)들의 연속 붕괴 가능성도 점점 커지고 있어 연속 댐 붕괴에 대한 비상대처계획도 수립에 대한 관심도 증대되고 있다. 국내에서는 댐(저수지) 붕괴로 인한 극한홍수해석이나 비상대처계획 수립시 국내에서는 DAMBRK, FLDWAV, HEC-RAS와 같은 1차원 수리동역학 모형이 주로 사용되어지고 있다. 하지만 1차원 모형은 흐름을 하나의 방향으로만 한정하여 해석하고, 각각의 적용 횡단면에서 동일 수위를 가지다는 가정으로 홍수범람해석을 수행하므로 정확성뿐만 아니라 실제 적용성에서도 한계를 가질 수밖에 없다. 댐(저수지) 붕괴로 인한 홍수범람해석에서 2차원 이상의 고차원 모형은 앞서 언급한 1차원 모형에 적용된 비현실적인 가정을 포함하지 않으므로 더욱 정교하고 신뢰성 있는 결과를 얻을 수 있다. 하지만, 홍수범람해석을 위한 상용 프로그램들은 단일 댐(저수지) 붕괴의 적용에는 큰 어려움이 없으나, 지형단면을 초기에 한번만 고려하는 문제로 인하여 연속 댐(저수지) 붕괴의 고려에는 한계를 가진다. 따라서 본 연구에서는 댐(저수지)의 연속 붕괴를 해석할 수 있는 2차원 수리동역학 모형을 개발하고자 한다. 각 댐(저수지)의 붕괴 전과 후의 지형 단면을 여러 번 반영할 수 있는 모형을 개발함으로써 시간차를 두고 붕괴되는 댐(저수지)의 연속 붕괴를 해석할 수 있도록 하였다. 개발모형은 2002년 태풍 루사로 인해 실제로 붕괴된 저수지에 적용되었으며, 이 저수지들은 붕괴시 시간차이를 두고 붕괴가 이루어져 개발모형의 적용 유역으로 선택하였다. 저수지의 연속붕괴 모델링을 위해 지형자료로는 저수지 단면, 댐 제체 및 여수로 붕괴 단면, 하천 단면 그리고 홍수터 지형 반영을 위한 수치지도, 경계조건으로는 저수지로의 유입유량과 하류단 조위조건이 고려되었다. 그리고 태풍 루사 당시의 기록적인 강우를 반영하기 위해 연구유역 인근에 관측된 강우를 모형에서 하천 및 홍수터에서 고려할 수 있도록 하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.3
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• pp.341-346
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• 2022

Due to global warming and abnormal climate, the frequency and damage of floods are increasing, and the number of people exposed to flood-prone areas has increased by 25% compared to 2000. Floods cause huge financial and human losses, and in order to reduce the losses caused by floods, it is necessary to predict the flood in advance and decide to evacuate quickly. This paper proposes a flood risk determination model using a CNN-based classification model so that timely evacuation decisions can be made using rainfall and water level data, which are key data for flood prediction. By comparing the results of the CNN-based classification model proposed in this paper and the DNN-based classification model, it was confirmed that it showed better performance. Through this, it is considered that it can be used as an initial study to determine the risk of flooding, determine whether to evacuate, and make an evacuation decision at the optimal time.