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한국형 저비용 저고도 공중보급 체계용 낙하산 전개 특성 풍동시험
김승필,정인식,권기범,최윤석,정형석,Kim, Seung Pil,Jung, Insik,Kwon, Kybeom,Choi, Younseok,Chung, Hyoungseog 한국군사과학기술학회 2017 한국군사과학기술학회지 Vol.20 No.3
A wind tunnel test for the scaled parachute models was performed to verify aerodynamic characteristics for practical usage of Korean low cost low altitude aerial delivery system. The cruciform shaped cargo parachute models for heavy and light weight were ejected into wind tunnel test section; and the drag forces acting on the models in steady condition were measured in accordance with velocity. Also, the maximum opening forces during inflation were obtained and captured by a high speed camera to analyze the inflation characteristics and evaluate the design of the low cost aerial delivery system. The results showed a reliable stability and met the design requirement of delivery operation system for R.O.K Air Force.
저합금강의 인코넬 625 육성용접 후 열처리에 따른 미세조직 및 기계적 특성
김승필 ( Seung Pil Kim ),장재호 ( Jae Ho Jang ),김정수 ( Jung Soo Kim ),김병준 ( Byung Jun Kim ),손근용 ( Keun Yong Sohn ),남대근 ( Dae-geun Nam ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.8
Overlay welding technique is one of methods used to improve metal mechanical properties such as strength, toughness and corrosion resistance. Generally, Inconel 625 alloy is used for overlay welding layer on low carbon steels for economic consideration. However, the method produces some problems in the microstructure of the cast structure and some defects, caused by the elevated temperatures of the overlay welding process. To resolve these problems, heat treatments are required. In this study, Inconel 625 alloy was welded on a low carbon steel by the overlay welding process to investigate the resulting microstructure and mechanical properties. A double heat treatment was performed to improve the mechanical properties of the welding and substrate layers. It was found that Inconel 625 alloy had an austenite microstructure after the first heat treatment, but the low carbon steel had a ferrite-pearlite microstructure after the second heat treatment. After the double heat treatment, the sample showed the optimum hardness because of grain refinement and homogenization of the microstructure. (Received October 23, 2015; Accepted February 29, 2016)
저추력 궤도전이 최적제어 문제에서 Legendre Pseudo-spectral 기법의 적용
김승필(조교수) ( Seung Pil Kim(assistant Professor) ),조동현(조교수) ( Dong Hyurn Cho(assistant Professor) ),권기범(부교수) ( Ky Beom Kwon(associate Professor) ) 공군사관학교 2015 空士論文集 Vol.66 No.1
저추력을 이용하는 인공위성 궤도전이 문제에 Legendre pseudo-spectral 기법을 적용하여 최적해를 구하였다. 해는 2차원 극좌표계의 상태변수와 제어변수로 구성된다. 상태변수는 초기시간부터 최종시간까지 거리와 법선방향 및 접선방향 속도이다. 제어변수는 인공위성 속도벡터의 접선 성분과추력 방향의 사잇각 이다. 본 연구에서 적용한 궤도전이 최적제어 문제는 제한시간에 최대에너지를 목적함수로 하는 문제로, 간접법을 통해서는 수렴해를 찾기 매우 어려운 민감한 문제이다. 그러나 직접법인 Legendre pseudo-spectral 기법을 적용함으로써 쉽게 수렴해를 구할 수 있었으며, 적은노드수를 적용하여도 좋은 수렴성능을 가짐을 확인하였다. 구한 수렴해를 이용한 초기값 가정을 통해, 개루프(open-loop)해를 구할 수 있었으며, 각각의 수렴한 궤적들이 서로 일치함을 확인함으로써 수렴해가 최적해임을 확인하였다 The optimal solution is obtained for the low-thrust spacecraft orbit transfer problem using a Legendre pseudo-spectral method. The results are states and control variables in 2-D polar coordinates. The state variables represent the distance from the origin of the attracting body and velocity in radial and tangential direction. The control variable is the angle between radial velocity and thrust vector. The objective function for this optimal control problem is maximizing the energy at a fixed final time. The solution from Legendre pseudo-spectral method is calculated more easier than indirect method. The results show a good performance in convergence when the fewer nodes are applied; and the implementation of the open-loop solution using the results of Legendre pseudo-spectral method shows the same results.
공익광고 메시지 프레이밍과 주제유형이 초등학생에게 미치는 광고 효과에 대한 연구
김승필 ( Seung Phil Kim ),김희정 ( Hee Jung Kim ) 한국PR학회 2013 PR연구 Vol.17 No.2
This study conducted research on the effects of the Public Campaign Advertising from a survey of elementary school students who have correct attitudes easily towards social phenomena within the context of media literacy which has recently become the conversation theme. It also investigated the difference in the effects of Public Campaign Advertising classified by grades, especially for the lower grades and the upper grades, and examined which framing, as message variable, would be more efficient between positive framing and negative framing. In addition, in regard of theme types, both the individual theme and the collective theme were on the examination to find out which theme would be suitable for elementary school students. Similarly, framing × theme type was examined to analyze an interaction between framing and theme types. On the basis of the survey, the following 4 results were found. Firstly, there was a difference in the effect of Public Campaign Advertising. In other words, students in the upper grades displayed better understanding of the advertising than students in the lower grades did, however, younger students had the right attitudes towards the advertising, whereas older students did not. Secondly, as for framing efficiency, the negative framing was the method that was fundamental to elementary school students` comprehensions of what the advertising meant and conveying the meaning of message by the threatening way (the negative framing) was appropriate rather than by friendly way (the positive framing). Thirdly, between the collective theme and the individual theme, the former was suitable for elementary school students, which was different from the expectation that the latter had been efficient due to high participation. Therefore, choosing the collective theme is recommended when the advertising is produced for elementary school students. Finally, “the negative framing - the individual theme” would be the most efficient to determine students` attitudes towards the Public Campaign Advertising in case of concurrent choice among framings and themes. Consequently, the Public Campaign Advertising for elementary school students will act as an effective advertisement as long as it is produced with taking students` grades, theme types and the advertising effects that vary according to the type of framing into consideration. Therefore, from now on, it is expected that various studies relevant to the advertising effects for elementary school students will be attempted.
김승필 ( Kim Seungpil ),신명수 ( Shin Myoungsu ),손동성 ( Sohn Dong-seong ),권혁주 ( Kwon Hyukjoo ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.1
This study examined the safety of nuclear spent-fuel (NSF) transport casks against accidental puncture events. Finite element analyses were conducted according to the accident conditions in NUREG-1536 and RG 7.8, which specify 1-m parallel and vertical drops on a rigid rod that has 15-cm diameter and 20-cm height. We focused on the safety evaluation of the cask body, baskets, and canister based on ASME BPVC Section III, and evaluated whether these elements would undergo excessive fracture or puncture.