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강명환,Kang, Myung-Hwan 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.4
During navigation of warships, sonar domes have been damaged by collision with floating objects like logs. In order to analyze the damage of a sonar dome from collisions with a log, The analytical method and the numerical analysis using ABAQUS are performed. Throughout the analytical method, the mechanism of collision between a sonar dome and log is analyzed. To design a sonar dome, the numerical analysis for A type sonar dome and the B type sonar dome have done considering fluid loading effect around the sonar domes with normal and maximum speeds of the ship, respectively. The numerical analysis results of the A type sonar dome and the B type sonar dome are compared and analyzed.
다중가진을 받는 수중 원통구조물의 방사효율에 대한 수치해석
강명환(Myunghwan Kang),이종주(Jongju Yi),한승진(Seungjin Han),배수룡(Sooryong Bae),정우진(Woojin Jung) 한국소음진동공학회 2014 한국소음진동공학회 학술대회논문집 Vol.2014 No.10
This study is on acoustic radiation efficiency of a tiffened cylindrical model in watermulti-excitation with phase difference using commercial numerical program ABAQUS and SYSNOISE. When the stiffened cylindrical model is under multi-excitation with phase difference, the surface vibration field is variated with phase difference of excitation. By this different surface vibration field, the acoustic radiation efficiency is also variated with phase difference of excitation.
위상차를 갖는 다중 가진 시 구조물의 방사효율 특성 해석
강명환(Myunghwan Kang),이종주(Jongju Yi),한승진(Seungjin Han),배수룡(Sooryong Bae),정우진(Woojin Jung) 한국소음진동공학회 2014 한국소음진동공학회 논문집 Vol.24 No.12
Acoustic radiation efficiency is one of the important factors in the prediction of underwater radiated noise of ships. A ship has much equipment to operate successful mission in a ship. Most of equipment is running simultaneously as multi-excitation and becomes the source of underwater radiated noise. In many cases of multi-excitation, phase difference between multi-excitation is not considered. Because vibration response under multi-excitation is the vector sum of each single excitation, acoustic radiation efficiency based on surface velocity field can be affected by phase of excitation. In this study, acoustic radiation efficiency of a plate on air and a stiffened cylindrical model in water under multi-excitation with phase difference is investigated.
강명환(Myengwhan Kang),서영수(Youngsoo Seo),신구균(Ku-kyun Shin),전재진(Jaejin Jeon) 한국소음진동공학회 2011 한국소음진동공학회 학술대회논문집 Vol.2011 No.4
For developing acoustic window, transmission loss in accordance with incident angle was calculated and compared with measurement results. In design stage, the material choice of acoustic window is very important because the material is parameter of transmission loss and structural strength. In order to analyze the effect of material properties on transmission loss, the parametric studies were carried out and the results were discussed in this paper.
파워최소법을 이용한 원통형 구조물의 진동감소 성능 분석
강명환(Myunghwan Kang),배수룡(Soo-Ryung Bae),정우진(Woo-jin Jung) 한국소음진동공학회 2017 한국소음진동공학회 논문집 Vol.27 No.5
Underwater radiation noise(URN) is one of the primary source to detect underwater weapon systems like submarine and warship. At a low frequency range, tonal noise is originated from structure borne noise of the equipment. In order to reduce this tonal noise, the active isolation of the transmission of structure-borne noise is necessary. In this study, active vibration reduction method using total power minimization is applied for reduction of total vibration of a raft structure in ship. An numerical analysis shows the effectiveness of vibration reduction at both resonant and off-resonant frequencies and importance of control excitation position. An experimental performance analysis is carried out for the feasibility of active vibration reduction method using total power minimization.
폴리스티렌/다중벽 탄소나노튜브, 나노복합재료의 물리적 분산 방법에 따른 물성
강명환(Myung Hwan Kang),염효열(Hyo Yeol Yeom),나효열(Hyo Yeol Na),이성재(Seong Jae Lee) 한국고분자학회 2013 폴리머 Vol.37 No.4
라텍스 기법으로 제조한 폴리스티렌(PS)/탄소나노튜브(CNT) 나노복합재료의 CNT 분산 방법에 따른 유변물성과 전기 전도도를 비교하였다. PS/ CNT 나노복합재룐느 PS 입자와 CNT를 분산시킨 후 동결건조하여 제조하였다. 본 연구에서는 화학적 개질시 나타나는 CNT의 고유 물성 저하를 방지하기 위하여 sodium dodecylsulfate(SDS)를 첨가하는 방법과 polyvinyl pyrrolidone(PVP)으로 CNT를 감싸는 방법의 물리적 분산법을 적용하였다. 라텍스 기범에 적용한 물리적 분산 방법은 CNT의 분산에 매우 효과적이었다. SDS를 첨가한 경우는 PVP로 감산 CNT를 사용하여 제조한 경우에 비해 나노복합재료의 유변물성의 증가폭이 낮은데 이는 저분자량인 SDS를 첨가로 인해 매트릭스의 물성이 감소하기 때문이다. CNT를 SDS로 분산시킨 나노복함재료와 PVP로 감싼 CNT를 사용한 나노복합재료의 전기적 임계점은 각각 0.23과 0.90wt%로 나타났다. PVP로 CNT를 감싼 경우가 전기 전도도 향상 효과가 낮은데 이는 감싸고 있는 절연성의 PVP가 CNT간의 전기적 연결을 억제하기 때문이다. The effect of CNT dispersion method on rheological and electrical properties of polystyrene/carbon nanotube(PS/CNT) nanocomposites via latex technology was compared. The nanocomposites were prepared through freeze-drying the dispersed suspension comprised of CNTs and PS particles. In this study, physical dispersion method, either sodium dodecylsulfate (SDS) addition or polyvinyl pyrrolidone (PVP) wrapping, was employed to prevent the deterioration of intrinsic properties of CNT caused by chemical modification. The physical method applied to latex technology was very effective in CNT dispersion. With SDS addition, the enhancement of rheological properties was low compared to PVP wrapping because the properties of matrix were deteriorated due to the incorporation of low molecular weight SDS. The electrical percolation threshold of PS/SDS-stabilized CNT and PS/PVP-wrapped CNT nanocomposites was 0.23 and 0.90 wt%, respectively. The enhancement of electrical conductivity was low in the case of PVP wrapping because the non-conducting PVPs wrapped around CNT restricted the electrical connection between CNTs.