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미사일 모델의 피치 동안정미계수 측정을 위한 강제진동기법의 적용
김승필,조환기,백승욱 한국군사과학기술학회 2000 한국군사과학기술학회지 Vol.3 No.2
This paper presents an application of forced oscillation technique to measure pitch dynamic stability derivatives of a missile model in the low speed wind tunnel. The missile model is oscillated by D.C. electric servomotor with constant amplitudes and frequencies. Phase shift is determined as the difference of peak values between input and output signals from the dynamic stability balance installed at the center of gravity of the model. Stability derivatives were calculated by using phase shifts, amplitudes, forcing moments and input frequencies. Test results show the proper usage of the force oscillation technique with good damping effects.
Pseudo-spectral Method를 이용한 저추력 궤도전이 최적제어
김승필,조동현,권기범 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4
저추력을 이용하는 우주선의 궤도전이 문제에 Pseudo-Spectral 기법을 적용하여 최적해를 구하였다. 해는 2차원 극좌표계의 상태변수와 제어변수 구성된다. 상태변수는 초기시간부터 최종시간까지 거리와 법선방향 및 접선방향 속도이다. 제어변수는 우주선 속도벡터의 접선 성분과 추력 방향의 사잇각이다. 본 연구에서 적용한 궤도전이 최적제어 문제는 제한시간에 최대에너지를 갖는 것을 목적함수로 설정하였다. 이 방법은 경계치 문제로 풀어야 하는 최적제어 기법보다 쉽게 해를 구할 수 있었다. 적은 노드 수를 이용하여도 좋은 수렴성능을 보여주었고. 외재적 수치적분으로 얻은 궤적도 동일한 결과를 얻을 수 있었다. The optimal solution is obtained for the low-thrust spacecraft orbit transfer problem using 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 applied solution is calculated more easier than two-point boundary problem. The results show a good performance in convergence when the fewer nodes are applied; and the implementation of the explicit numerical shows the same results.
흰쥐에 초산납투여가 신장조직중 Free Radical 대사효소 활성과 초미형태학적 변화에 미치는 영향
김승필,윤종국,박관규 한국독성학회 1995 Toxicological Research Vol.11 No.1
To investigate the ultrastructural changes of kidney and clarify to a cause of its changes in lead intoxicated rats, the 0.5% lead acetate administed orally to the rats and those were sacrifled at 2 day, 1, 2, 4, 6 and 8 week after the treatment of lead acetate. Each extirpated kidney was histopathologically examined under the electron microscopy and histochemical examination was also carried out. Concomitantly, the activity of free radical metabolizing enzyme was determined. The blood levels of lead concentration showed a gradual increase from the first group reaching the plateau at the one or two week group with the slightly decreasing value throughout the whole course of the experiment. And the urinary ALA concentration showed a gradual increase from the first group to the 8 week group. In the kidney tissue of rat sacrified at 6 week, the proximal tubular cells showed dilatation of endoplasmic reticulum, mitochondrial swelling, increased numbers of secondary lysosomes and myelin figure-like residual bodies on electron microscope and oxygen free radicals are identified by histochemistry on light microscope whereas there were no differences in the activity of catalase and glutathione peroxidase between the lead acetate treated group and control group. But the activity of xanthine oxidase was more increased in lead acetate treated rats than control group. Furthermore, the superoxide dismutase activity was significantly increased in the experimental group than the control group. In conclusion, it is assumed the kidney damage in lead intoxicated rat may be induced by free radicals.
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.