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선체-부가물 영향을 고려한 비공동 수중추진기의 소음예측 연구
최지훈,설한신,박일룡,이수갑,Choi, Jihun,Seol, Hanshin,Park, Ilryong,Lee, Soogab 한국음향학회 2019 韓國音響學會誌 Vol.38 No.3
본 연구에서는 대형화, 고속화되어가는 잠수함 추진기의 소음을 보다 정확하게 예측하기 위하여 선체-부가물-추진기의 상호작용이 묘사되는 유동 수치해석을 토대로 비공동 추진기 소음을 예측하였다. 추진기 방사 소음을 예측하기 위해 선체-부가물-추진기 전체영역에 대한 유동 정보를 전산유체역학 해석으로 얻은 뒤, FW-H(Ffowcs Williams-Hawkings) 음향상사법을 적용하여 두께소음, 하중소음에 대한 소음을 수치적으로 예측하였다. 수치적 소음예측 결과는 모형시험을 통해 검증하였으며, 전체 소음 수준과 저주파 대역 소음예측에 있어 계측결과와 좋은 일치를 보였다. In this study, to predict the noise of a submarine propeller which is going to become bigger and faster, the non - cavitating propeller noise was predicted based on the numerical analysis which considering the interaction of the hull - appendages - propeller. In order to predict the radiated noise of the propeller, the flow field for the entire region of hull-appendages-propeller was computed by CFD (Computational Fluid Dynamics). And the noise for the thickness noise and the load noise was numerically predicted using FW-H (Ffwocs Williams-Hawkings) acoustic analogy. Numerical noise prediction results were verified by model tests and showed good agreement with the measurement results in predicting total noise level and low frequency noise.
공간적인 알리아싱을 포함한 탄성파 트레이스의 내삽을 위한요소파 기반의 Matching Pursuit 기법
최지훈 ( Jihun Choi ),변중무 ( Joong Moo Byun ),설순지 ( Soon Jee Seol ) 한국지구물리·물리탐사학회 2014 지구물리와 물리탐사 Vol.17 No.2
Due to mechanical failure or geographical accessibility, the seismic data can be partially missed. In addition, it can be coarsely sampled such as crossline of the marine streamer data. This seismic data that irregular sampled andspatial aliased may cause problems during seismic data processing. Accurate and efficient interpolation method can solvethis problem. Futher more, interpolation can save the acquisition cost and time by reducing the number of shots and receivers. Among various interpolation methods, the Matching Pursuit method can be applied to any sampling type which is regular or irregular. However, in case of using sinusoidal basis function, this method has a limitation in spatial aliasing. Therefore, in this study, we have developed wavelet based Matching Pursuit method that uses wavelet instead of sinusoidal function for the improvement of dealiasing performance. In addition, we have improved interpolation speed by using inner product instead of L-2 norm.
160도 Contra angle을 갖는 소형 핸드피스용 1:2증속기어의 치형 해석
최지훈(Jihun Choi),안수경(Sukyeong Ahn),박상신(Sangshin Park) 한국트라이볼로지학회 2014 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.30 No.2
This paper presents a design procedure for a face gear and pinion used in a handpiece with a 160°y contra angle and 1:2 gear ratio. Based on the geometric theory of gearing, the tooth profile of the face gear and pinion is developed. To analyze the contact pressure, the gear profile should be determined before calculating the stress between the two gears. The concept of calculating the face gear profile is that it can be generated by the coordinate transformation of the shaper profiles, which have involute curves, using a simulation method from the gear manufacturing process.
160도 Contra angle을 갖는 소형 핸드피스용 1:2 증속기어의 치형 해석
최지훈(Jihun Choi),안수경(Sukyung Ahn),박상신(Sangshin Park) 한국트라이볼로지학회 2014 한국트라이볼로지학회 학술대회 Vol.2014 No.4
This paper presents a design procedure of face gear and pinion which are used in a handpiece with 160 degree contra angle and 1:2 gear ration. Based on the geometric theory of gearing, the tooth profile of the face gear and pinion were developed. In order to analyze contact pressure, the gear profile should be determined before the calculation of the stress between the two gears. The basic idea for calculating the gear profile is that face gear profile can be generated by the coordinate transformation of shaper profiles which has involute curves using a simulation method of the gear manufacturing process.
전기자동차 보급에 따른 기존 아파트의 변압기용량 한계시점에 대한 연구
최지훈(Jihun Choi),김성열(Sung-Yul Kim),이주(Ju Lee) 대한전기학회 2016 전기학회논문지 Vol.65 No.12
Rapid Expansion of EVs(Electric Vehicles) is inevitable trends, to comply with eco-friendly energy paradigm according to Paris Agreement and to solve the environment problems such as global warming. In this paper, we analyze the limit point of transformer acceptable capacity as the increase of power demand considering EVs supply in the near future. Through the analysis of transformer utilization, we suggest methods to analyze the spare capacity of transformer for the case of optimal efficiency operation and emergency operation respectively. We have the results of 18.4~29% spare capacity for the charging infrastructure to the rated capacity of transformer by analyzing the existing sample apartments. It is analyzed that the acceptable number of EVs is 0.09~0.14 for optimal efficiency operation and 0.06~0.13 for emergency operation. Therefore, it is analyzed the power demand of EV will exceed the existing transformer spare capacity in 7~8 years as the annual growth rate of EVs is prospected 112.5% considering current annual growth rate of EVs and the government EV supply policy.
전기자동차 보급에 따른 공공임대아파트의 변압기 안정성 평가에 관한 연구
최지훈(Jihun Choi),김성열(Sung-Yul Kim),이주(Ju Lee) 대한전기학회 2017 전기학회논문지 Vol.66 No.7
This paper aims to analyze the safety evaluation of the existing transformer for the 0.85 millions of public rental apartments as EVs(Electric Vehicles) increase in order to overcome the environment pollution issue and maintain sustainable development. It is analyzed that the 56.4% capacity of power transformer could secure as EV charging infrastructure, based on the analysis of respective utilization patterns of the housing and power transformer. The acceptable number of EVs is 0.04~0.06 per household from the spare capacity of the power transformer. It is analyzed that EV stock is prospected less than 0.03 per household in 2030, considering the condition of the public rental apartments residents and the growth rate of EVs according to practical scenario. The power demand for EVs is within the allowable capacity range of the power transformer, so the research shows that there is no problem in the stability of the existing transformer until 2030
최지훈 ( Jihun Choi ),임현창 ( Hyunchang Im ),정재천 ( Jaecheon Jung ),공기석 ( Ki-sok Kong ) 한국정보처리학회 2017 한국정보처리학회 학술대회논문집 Vol.24 No.2
교통사고를 예방하고자 정부에서는 지속적인 정책을 펼치고 있으나 발생률이 크게 줄지 않는 실정이다. 본 논문에서는 이러한 한계점을 보완하고자 영상처리를 이용하여 교통사고를 줄일 방법을 제안하고자 한다. 우선 어린이 보호 구역 내에 설치된 카메라를 이용하여 교통사고 발생 위험을 판단하고, 보행자 및 차량 운전자에게 알려 줌으로써 교통사고 발생을 감소하고자 하는 시스템을 설계하였다. 또한 실시간 영상처리를 위해 관심 영역 지정, 멀티 스레드 등 다양한 방법을 적용해 보았으며, 위험 상황 탐지 시 탐지 결과를 주변 운전자에게 전송하려는 방법을 제시하고 실제 구현하여 확인해 보았다.