• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.169-176
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• 2001

The sediment at the majority of fishery harbors located on the east coast of Korea are affccted by the waves and wave-induced currents as the main external force. And the surroundings of the harbors are composed of sandy beaches. Because many harbors are small and their entrances are located in the wave¬breaking zone, they suffer severe siltation and topographical changes. In order to solve the problems, we have to understand the mechanism through estimations and accurate reproduction of the harbor siltation phenomenon. We suggest economically substantial countermeasures for harbor siltation in the small fishery harbors and investigate the preventive effects using a numerical simulation technique.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.176-176
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• 2015

최근 대하천사업을 통하여 낙동강에 총 8개의 다기능보가 설치되었으며, 이러한 하천 내 수공 구조물은 하천에 서식하는 어류의 이동과 군집의 변화, 유전적 단절, 서식처 변화와 같은 다양한 문제점을 유발할 수 있으며, 특히 어류의 산란기에는 하천의 유로를 따라 상류로 이동하거나 하류로 이동하는 회유성 어류들에게는 심각한 문제를 야기한다. 이러한 다기능보의 상 하류의 단절로 인한 문제를 해결하기 위해 낙동강 8개의 다기능보에 자연형 및 인공형 어도가 설치되었으며, 이를 평가하기 위한 어도의 유인효율에 대한 연구가 중요하다. 어류는 최대 유속이 발생하는 지점인 유심선에서 소상하려는 특성을 보이는데, 어도의 입구부의 유속이 중요하게 작용한다. 어도 입구부의 유속분포 및 수심에 따라 유인효율은 다르게 나타날 수 있으며, 2차원 수리해석을 통해 WUA를 산정함으로써 어도의 유인효율을 평가할 수 있다. 본 연구에서는 2차원 흐름해석 모형인 River2D를 이용하여 어류의 소상이 중요한 산란기를 기준으로 강정고령보의 가동보 운영실적을 이용하여 수리해석을 실시하였으며, 연구결과를 바탕으로 자연형어도의 유인효율을 평가하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.64-64
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• 2017

본 연구에서는 낙동강에 위치한 강정고령보에 설치된 자연형 어도의 유인효율 증대를 위한 어도의 위치 수정 제시를 하였다. 평면 2차원 물리서식처 모형인 River2D 모형을 통해 강정고령보의 자연형어도 입구부의 유속장과 WUA(Weighted Usable Area)를 이용하여 유인효율을 분석 실시하였다. 유인효율 분석 결과 자료와 2013년도 어류모니터링 자료를 통해 WUA는 어류 유인효율 평가하는 지수로 사용 될 수 있는 것을 간접적으로 검증하였다. 어류의 소상에는 유속이 중요한 인자로 작용한다. 모의를 통한 강정고령보의 유속장을 확인해보면 자연형어도가 설치된 좌안과는 반대로 우안쪽으로 형성되는 것을 확인하였다. 어도의 모양 및 위치를 수정한 지형자료를 이용하여 River2D 모형모의를 통한 어도의 유인효율을 증대 시킬 수 있는 방법을 제시하였다. 유속장이 주로 발생하는 보 우안쪽에 설치하는 것이 유인효율을 최대로 끌어낼 수 있었지만 비용적인 부분과 유인효율을 같이 생각한다면 현재 설치된 좌안 자연형어도의 입구부를 상류쪽으로 위치하여 재설치하는 것이 어류의 유인효율을 증대시켜주는 효과적인 제시방안이 되리라 사료 된다.

• Journal of the Korean Society for Railway
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• v.15 no.5
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• pp.436-441
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• 2012

Pressure waves are generated and propagate in tunnel when train enters a tunnel with high speed. Compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as expansion wave. While expansion wave due to the entry of train tail propagates along the tunnel and is reflected at tunnel exit as compression wave. These pressure waves are repeatedly propagated and reflected at tunnel entrance and exit. Severe pressure change per second causes ear-discomfort for passengers in cabin and micro pressure wave around tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnel qualitatively and quantitatively, because pressure change rate is considered as one of major design parameters for an optimal tunnel cross sectional area and the repeated fatigue force on car body. In this study, we developed the characteristics method analysis based on fixed mesh system and compared with the results of real train test. The results of simulation agreed with that of experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.361-369
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• 2011

The effect of an increase in the temperature of inlet air on the performance of a membrane humidifier for a PEMFC (Polymer Electrolyte Membrane Fuel Cell) vehicle was investigated both experimentally and numerically. A shell-and-tube type gas-to-gas humidifier with Nafion membrane was tested. The experimental result showed that water transfer varies nonlinearly with the temperature elevation. Numerical analysis based on detailed modeling was also conducted in simplified geometry of a single tube to explain this nonlinear behavior. The simulation revealed that the local water flux varies nonlinearly and dramatically along the tube. The analysis was based on the inverse relationship between the increase in temperature and decrease in relative humidity, both of which seriously affect the water conductivity of the membrane.

• The KSFM Journal of Fluid Machinery
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• v.5 no.3 s.16
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• pp.54-59
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• 2002

A commercial CFD code is used to compute the 3-D viscous flow field within the inlet flow concentrator of the newly developed AHU (Air Handling Unit). To improve the performance of the AHU, the inlet air needs to be gradually accelerated to the fan's annular velocity without causing turbulence or flow separation. Three major geometric parameters were selected to specify the inlet shape of the AHU. The performance of the AHU could be measured by the inlet and outlet flow uniformity and the total pressure loss through the inlet flow concentrator. Several numerical calculations were carried out to determine the influence of the geometric parameters on the performance of the AHU. The best geometric values were decided to have efficient inlet shape with analyzing CFD calculation results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.232-236
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• 2006

하이브리드 로켓에서 그레인 전체 부분에서 고른 연소율 향상을 이룰 수 있는 방법으로 스월 유동과 나사산 그레인을 동시에 적용하여 실험을 실시하였다. 그 결과 입구부분과 연료 후반부에 집중된 연소현상을 확인하였다. 스월 유동은 스월 유동의 종류에 상관없이 일정한 감소율을 나타낸다. 그리고 연소율 향상은 연료 벽면에서의 회전 유동 강도에 비례한다고 가정 할 수 있다. 따라서 입구부분의 집중된 연소현상을 해소하고 일정한 연소율 향상을 이룰 수 있는 스월 유동 조건에 대해 연구하였다.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.448-453
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• 2001

A commercial CFD code is used to compute the 3-D viscous flow field within the inlet flow concentrator of the newly developed AHU(Air Handling Unit). To improve the performance of the AHU, the inlet air needs to be gradually accelerated to the fan's annular velocity without causing turbulence or flow separation. Three major geometric parameters were selected to specify the inlet shape of the AHU. Several numerical calculations are carried out to determine the influence of the geometric parameters on the performance of the AHU. The performance of the AHU could be measured by the inlet and outlet flow uniformity and the total pressure loss through the inlet flow concentrator. The optimized nondimensionalized velocity profile through the inlet flow concentrator were used for the design of the AHU with the various volume flow rates.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.44-49
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• 2007

In this paper, effects of inlet shape on the performance of a submerged cargo pump were numerically studied using a commercial CFD code CFX. The inlet shape, especially the gap between pump and suction well, is an important parameter in a point of view of performances of submerged cargo pump due to its effects on the residual and also hydraulic performance of the pump, respectively. To know the optimized gap, the overall performance degradations were calculated with the gap. In addition to that, the flow field through the gap was investigated to explain the effect of velocity non-uniformity on the performance of the pump impeller.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.365-368
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• 2021

In this study, a plastic bottle recycling bin system that utilizes an infrared sensor was implemented. The proposed system consists of a recognition unit, a control unit, an alarm unit, and a driving unit. The recognition unit detects the plastic bottle, measures the distance between the plastic bottle and the infrared sensor, extracts the value of the bottle, compares the extracted value with a standard range, and then transmits the control value to the control unit if the extracted value of the bottle is outside the standard range. In this case, the result of the presence or absence of a brand label or bottle cap is transmitted to the controller. The control unit opens the entrance of the recycling bin or alerts the alarm unit according to the result value transmitted from the sensor unit. In order to implement the proposed system, the recognition unit was implemented with an infrared sensor, and the control unit was made with an Arduino IDE controller, based on the C programming language. Additionally, the recognition unit and the control unit are able to communicate using analog signals. The proposed system accurately judges the presence or absence of a brand label and bottle cap of plastic bottles according to a predetermined algorithm. It then blocks the entrance of the recycling bin when a brand label or bottle cap is still attached. As the amount of waste discharged per person is relatively high and the majority of such waste is incinerated rather than recycled, the system proposed in this study is expected to increase the recycling rate of plastic bottles.