• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.221-231
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• 2021

In the present study, numerical simulation was performed to investigate aerodynamic characteristics of a ducted fan-upper/lower vanes system in hover. Sensitivity analysis of aerodynamic forces for a system component was conducted with the deflection angle of upper vanes varying but at the constant rotational speed and the collective pitch angle of fan blades. Then, vane control performance and duct airload distributions were analyzed in detail to physically understand operating mechanisms of individual vane and interference effect between duct and vanes. Finally, new control concept of operating upper vanes has been proposed to improve the control performance of the full configuration. It is found that the side force and rolling moment of upper vanes increase linearly with the variation of those deflection angle; however, the total side force is significantly small due to the reaction force acted on the duct. It is also found that upper vanes close to the duct contraction side have a key role in changing vane control forces. It is revealed that the duct suction pressure is induced by the interaction with the suction side of upper vanes, while duct pressure recovery by the interaction with the pressure side, leading to increase in duct asymmetric force. When four upper vanes are kept in situ at 0° deflection angle or removed, the total control performance was improved with duct asymmetric force reduced and the total magnitude of roll remarkably increasing up to 80%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5572-5577
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• 2012

Results of in-situ test, laboratory test and strength prediction method for the soft soil underlain by failed road embankment were compared each other. Comparing cone penetration test results with the field vane test results it can be seen that cone factor is 12. Undrained shear strengths determined from the cone factor which was predicted by prediction equation were smaller than those obtained from field vane tests. Among the prediction methods Jamiolkowsky's method gave close strengths to the measured undrained shear strengths by field vane tests and strength ratio were 0.88~1.23.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.426-430
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• 2012

본 연구에서는 3차원 수치 해석 기법으로 SDR 반응기 내 유동 특성을 모사하여 유동 분포 및 체류 시간등을 확인하고 혼합 특성 개선을 위한 방법에 대해 연구하였다. 본 연구 대상 SDR 반응기는 입구 덕트와 반응기 본체의 접속 구간에 가이드 베인(Guide vane)이 설치되어 있고 그 바로 하부 지점에 흡수제를 분무하는 노즐이 설치되어 있다. 이는 처리가스가 반응기로 유입될 때 가이드 베인에 의해 선회류를 형성하여 분무된 흡수제와의 혼합을 촉진시키기 위한 목적으로 설치하였다. 시간당 1,971$m^3/min$ at $260^{\circ}C$의 처리가스가 반응기 상부로 유입되어 가이드 베인을 거쳐 선회류를 형성한 후흡수제와 혼합되어 하부로 배출되는 구조이다. 유동 특성을 분석한 결과, 처리가스가 반응기 중앙으로 강하게 편중되고 있었으며 반응기 양 측면으로 부상 기류가 형성되고 있음을 확인할 수 있다. 또한 강한 편류에 의해 체류시간도 매우 짧은 것으로 판단되는 바, 가이드 베인의 기류 안내 각도가 적합하지 못함을 확인할 수 있었다. 이는 곧 혼합 특성 저하에 따른 미반응 액적의 다량 발생과 함께 고착에 의한 스케일 형성 가능성이 매우 클 것으로 예상되므로 혼합 특성을 개선할 수 있는 설계 변경이 필요할 것으로 판단되었다. 따라서 편류를 해소하고 노즐 근처에서의 체공시간을 확보할 수 있도록 가이드 베인의 안내 각도를 더 크게 변경한 결과, 기존 설계상에서 본체 중앙에 형성되는 편류가 해소되고 선회류의 전개 각도가 커지면서 체류시간 역시 약 5초 이상으로 유지되고 있음을 확인할 수 있었다. 따라서 가이드 베인의 각도만 변경하더라도 본체 형상의 추가적인 변경없이 유동의 혼합 특성을 개선시킬 수 있을 것으로 판단되었다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.549-557
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• 2017

Numerical studies have been carried out on scrubbers, which are after-treatment devices to satisfy strengthened emission regulations for sulfur dioxide and particulate matter. We investigated the problems with existing scrubbers through numerical analysis and designed and analyzed a new swirl-type scrubber that could solve these problems. As a result, with the swirl-type scrubber, exhaust gas formed a vortex in the lower part of the device, and some of this gas was released along the guide vane through the bottom surface. In this case, the pressure gradient in the vertical direction was not large, but a pressure difference between the inside and outside of the baffle was generated. The shape of the exhaust gas stream was investigated, and when water was not sprayed, the exhaust gas flowed constantly to the outlet along the guide vane, in contrast to when water was sprayed. It was confirmed that the shape of the flow was influenced by the guide vane, nozzle arrangement and water pressure. In the case of the swirl-type scrubber, impact on engine back-pressure was minimal, because differential pressure at the inlet and outlet was less than half of that with a conventional scrubber.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4D
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• pp.523-531
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• 2008

This study tried to find differences between housing lotting prices and sale prices owing to new multi-family housing price regulation. As the results of this study, they are as follows; First, this study shows housing market in Busan has a preferences of new housing which has a new housing form differing from the existing housing form. For example, the mixed-use apartment with higher stories shows steeper incline than the apartments with the existing forms. Second, the new housing prices are affected by the information that affect the price of the old existing housing. They are rates of green area of an apartment complex, the number of household, accessibility to downtown Busan and etc.. They are also confirmed factors that affect a rise of used-housing price in other studies. Third, brand value of apartments affects new housing prices. For example, if the major construction companies build the new apartment, it shows a rising trend than any other housing. Therefore, the local construction companies are expected to be put on a disadvantage places than major construction companies. Fourth, the lotting prices are the most important cause that lead to rise the new housing prices. Accordingly, the present lotting prices are expected that upward tendency the purchasing prices of the new housing will not continue, because the lotting prices have risen since the government removed lotting price regulations and exceeded the level of used-housing prices. And it denote that importance of housing sub-market which indicates rates of old existing housing market rising, frist preference Gu, second preference Gu, rate of multi-family housing.