• Journal of Biomedical Engineering Research
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• v.23 no.5
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• pp.375-383
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• 2002

Aneurysm embolisation method using coils have been widely used. Micro coils are introduced via a small catheter, and are packed inside of aneurysm sac, which induces intraaneurysmal flow stagnation and thrombus formation. When partial blocking of an aneurysm is inevitable, the location of coils is important since it changes the flow patterns inside the aneurysm, which affect the embolisation process. We measured the flow field inside the partially blocked lateral aneurysm models in vitro, and tried to suggest the effective locations of coils for aneurysm embolisation. Velocity fields are measured using a particle image velocitimeter for different coil locations- proximal neck, distal neck, proximal dome and distal dome. Flow into the aneurysm sac was significantly reduced in the distally blocked models, and coils at distal neck blocked inflow more effectively comparing to those at distal dome. This study suggests that distal neck should be the most effective location for aneurysm embolisation.

• Journal of the Korean Geographical Society
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• v.41 no.6 s.117
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• pp.670-681
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• 2006

The purpose of this study is to clarify the behavior of subsurface water flow during rainfall on the hillslope in the Dongguneung experimental basin. As a result of the study, the following conclusions were obtained. Under the total rainfall of 20mm, there were no groundwater level changes. However, it was found that total rainfall amount and rainfall intensity were important factors to change groundwater level in hilly slope. Also the rainfall duration and preexisted rainfall amount were important factors to change it on the head hollow. To analyze the modification of 'U-shaped Gol' landform, the pattern of return flow and through flow have to check during storm events. The microgeomorphic change of head hollow is based on the pattern of subsurface water flow.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.200-200
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• 2011

실제 유역에서 지류유입량(tributary inflow)의 형태로든 사면류의 형태로든 측방유입은 반드시 존재한다. 측방유입이 하도의 지배적인 흐름이 되는 경우 이는 유출수문곡선의 종거값과 형태를 변화시키는데 중요한 역할을 하게 된다. 따라서 측방유입의 형태를 저류상수 및 집중시간과 같은 수문학적 특성으로 적절하게 표현할 수 있다면, 전체 유역 내에서 측방유입의 지체효과 및 저류효과를 파악하는데 크게 기여하게 된다. 측방유입과 관련된 선행연구들을 살펴보면, Saint-Venant 방정식을 근간으로 하는 연구가 주를 이루고, Muskingum 하도추적모형 또는 Muskingum-Cunge 하도추적 모형을 확장한 연구가 나머지 부분을 차지한다(Hayami, 1951; Dooge et al. 1982). 지금까지 수행된 대다수의 연구들은 수치해석적으로 측방유입의 유출량을 모의하거나 혹인 관측값이 존재하는 경우 역으로 측방유입의 특성을 유추한 것들로 다소 복잡하고, 관측값이 존재하지 않는 경우에는 적용이 어려운 문제점을 가지고 있다. 그러나 유역의 물리적인 특성과 주하도의 특성만을 이용하여 측방유입의 특성을 대략적으로 유추하는 것이 가능하다면, 전체유역과 각 소유역의 관계는 전체유역의 물리적인 특성과 주하도의 수문학적 특성만으로 충분히 파악할 수 있게 된다. 다시 말해 유역분할 시 각 소유역 사이의 관계를 고려하여 전체유역의 유출량을 파악하는 것이 가능해진다. 이에 본 연구에서는 Muskingum 하도추적모형을 재해석한 순간단위도를 이용하여 측방유입의 수문학적 해석을 시도하였다. 대상유역으로는 격자형태의 사각형과 삼각형 유역을 임의로 가정하였으며, 각각의 유역에서의 순간단위도를 선형하천모형과 선형저수지모형의 합으로 유도하였다. 이때 저류상수는 하도길이와 비례한다는 가정을 바탕으로 사각형과 삼각형 유역에서의 저류상수 및 집중시간을 유도하였다. 특히 유역 출구에서 최원점에 위치한 격자에서 유출이 발생시간을 집중시간으로 가정하였으며, 이 시점에서의 종거값과 기울기를 이용하여 저류상수를 유도하였다. 그 결과, 선형하천과 선형저수지모형 각각은 집중시간과 저류상수로 특징지어짐을 알 수 있었으며, 결정된 측방유입의 저류상수 및 집중시간이 적절한 것을 확인하였다. 이러한 결과는 향후 대유역에서 유역분할의 효과뿐만 아니라 홍수량 할당문제를 입증하는데 크게 기여할 것으로 기대된다.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.787-796
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• 2002

Hydraulic flood routing was performed for unsteady flow in a natural river using Preissmann scheme. A Log-Pearson Type-Ⅲ hydrograph is chosen arbitrarily as the upstream boundary condition and lateral inflow hydrographs for sensitivity analysis. For the application with an actual river system, upstream and lateral inflow hydrographs were estimated by the linear reservoir model and the Manning's equation was used as the downstream boundary condition. The unsteady flow model using the linear reservoir model as the inflow hydrographs was applied to Bochung stream basin and gives good results, and is approved to be used for the runoff prediction. As results of the sensitivity analysis, the proposed model may help to estimate the roughness coefficients when using the unsteady flow model with lateral inflow combined with the linear reservoir model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.95-106
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• 2021

Side-jets enable the immediate maneuver of a missile compared to control surfaces; however, they may cause adverse effects on aerodynamic coefficients, for they interfere with freestream. To find out the impact of side-jets on aerodynamic coefficients, we simulate side-jets as air gas and utilize multi-fidelity models to evaluate differences between aerodynamic coefficients obtained with and without side-jets. We computed differences in aerodynamic coefficients to investigate side-jet effects for the changes of a Mach number, a bank angle, and an angle of attack. As a result, asymmetrically developed side-jets affect the longitudinal force and moment coefficients, and the lateral force and moment coefficients drastically change in-between -30 and 30 degrees of bank angles. In contrast, side-jets hardly influence the axial force coefficients. As for the axial moment coefficient, we could not determine the side-jet effect due to a lack of aerodynamic coefficient samples in the Mach number. All in all, we confirm that side-jets lead to the change of a missile attitude as they considerably vary the longitudinal and lateral aerodynamic coefficients.

• Journal of Korea Water Resources Association
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• v.50 no.12
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• pp.827-836
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• 2017

The most important parameters of the Muskingum method, widely used in hydrologic river routing, are the storage coefficient and the weighting factor. The Muskingum method does not consider the lateral inflow from the upstream to the downstream, but the lateral inflow actually occurs due to the rainfall on the watershed. As a result, it is very difficult to estimate the storage coefficient and the weighting factor by using the actual data of upstream and downstream. In this study, the flow without the lateral inflow was calculated from the river flow through the hydraulic flood routing by using the HEC-RAS one-dimensional unsteady flow model, and the method of the storage coefficient and the weighting factor calculation is presented. Considering that the storage coefficient relates to the travel time, the empirical travel time formulas used in the establishment of the domestic river basin plan were applied as the storage coefficient, and the simulation results were compared and analyzed. Finally, we have developed a formula for calculating the travel time considering the flow rate, and proposed a method to perform flood routing by updating the travel time according to the inflow change. The rise and fall process of the flow rate, the peak flow rate, and the peak time are well simulated when the travel time in consideration of the flow rate is applied as the storage coefficient.

• Economic and Environmental Geology
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• v.40 no.3 s.184
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• pp.319-330
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• 2007

The Muposan Tuff is a stratigraphic unit which is distinguished as a cooling unit in the volcanic rocks of the northeastern Kyeongsang Basin. The Muposan Tuff commonly belongs to tuff field according to the granulometric classification and to vitric tuffs according to the constituent classification. The tuffs are mostly densely to partially welded to include very flattened and sometimes stretched pumices and shards, and involve several flow indicator and lateral gradings in maximum diameter and content of their constituents. Movement pattern from flow lineation, lithic and pumice imbrications, asymmetric flow folds, and lateral gradings in maximum diameter and content of their constituents indicate that the Muposan Tuff had a source from the southeastern part.

• Proceedings of the Korea Contents Association Conference
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• 2011.05a
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• pp.187-188
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• 2011

저 에너지 방사선검사 시 부득이하게 방사선 노출을 받게 되는 방사선 작업종사자나 환자의 보호자가 위치와 거리에 따른 방사선 피폭 선량의 감소 방안을 알아보고자 한다. Ion chamber mode 2026c, Reader기 20X6-1800을 사용하여 구강내 검사와 구강외 검사의 각각 검사실과 조정실에서의 관전압의 변화, 관전류와 조사시간의 변화, 조사방향의 변화에 따라 선량을 측정하였다. 그 결과 검사실 안에서는 최고선량이 평균 $702.8{\mu}R$으로 측정 되었으며, 조정실 안에서 측정하였을 경우 $20{\mu}R$이하의 낮은 선량을 보였으며, 후방검사보다 측방검사가 낮은 선량으로 나타났다. 방사선검사 시 위치와 거리에 따른 조사선량을 비교 분석하여, 적절한 거리 확보와 조사되는 중심방사선을 기준으로 측방($90{\sim}135^{\circ}$)에 위치함으로써 방사선 방어에 도움을 줄 것이며, 차폐문을 이용하여 방사선 피폭으로부터 감소 효과를 볼 수 있을 것이다.

• The Journal of the Petrological Society of Korea
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• v.26 no.2
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• pp.153-163
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• 2017

The Naeyeonsan Tuff is a stratigraphic unit which is distinguished as a cooling unit in the volcanic rocks of the northern Pohang. The Naeyeonsan Tuff, which is composed of crystals of plagioclase, quartz and hornblende, glasses of pumice and shard, and lithics of dacite, rhyolite, sandstone and shale, belongs to a lapilli tuff field according to the granulometric classification and to a vitric tuff field according to the constituent classification. The tuffs mostly develop welding foliations by dense welding and flatterning pumices and shards, and show several flow indicators by pyroclastic flowing. We can know a movement pattern from flow lineations and imbrications by pumices and lithics, and lateral gradings in isopleth map by average largest lithics and pumices in the Naeyeonsan Tuff, which indicate that the Naeyeonsan Tuff had a possible source area from the southeastern part.

• Magazine of the Korea Concrete Institute
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• v.13 no.2
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• pp.38-43
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• 2001

교량 하부구조 특히 교각 및 기초의 경우는 지반 또는 수중에 묻혀 있기 때문에 손상을 발견하기도 어렵고 또한 손상의 보수 및 보강이 곤란한 경우가 많다. 하부구조의 손상은 지반의 마모, 침하, 측방유동토압, 하상세굴, 홍수류, 선박 및 유하물에 의한 충격, 지진 등의 여러 원인에 의하여 발생된다. 이러한 손상은 지표수 및 지하수 배제공, 성토공, 지반개량공, 단면보수공, 세굴방지공, 내진보강공 등에 의하여 보수 및 보강이 행하여 진다. 본 고에서는 이러한 하부구조의 보수.보강공법 중 수중부에 실시되는 방법에 대하여 소개하고자 한다.