• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.40.3-41
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• 2009

인류가 위성을 발사하기 시작하면서 수많은 우주파편이 발생하게 되었고 이로 인하여 우주파편 환경은 날이 갈수록 심각해지고 있다. 우주공간을 비행하는 우주물체는 분쇄된 파편, 임무 관련 파편, rocket body 그리고 운용위성으로 구분된다. U.S. Space Surveillance Network에 따르면 10cm 이상 크기를 갖는 물체는 현재 13,000개가 넘는다고 알려지고 있고 질량만 해도 6,000톤이 넘는다. 이런 우주파편 환경으로 인하여 우주파편 간의 충돌, 우주파편과 운용위성 간의 충돌 또는 운용위성 간의 충돌에 대한 우려가 꾸준히 제기되어왔고, 불행하게도 2009년 2월 10일 Iridium 33과 Cosmos 2251 위성이 고도 790km 부근에서 충돌하여 1,300여개의 우주파편이 발생했다. 또한 2007년에 중국이 고도 860km 부근에서 750kg에 해당하는 자국의 위성(FY-1C)을 미사일로 격추시킴에 따라 2500여개의 우주파편이 발생하여 저궤도의 우주파편 환경을 더욱 심각하게 만들고 있다. 운용위성과 우주파편과의 충돌 가능성을 분석하기 위해서는 우주파편 및 위성의 궤도정보를 알아야 한다. 이를 위해서 NORAD(North American Aerospace Defense Command)에서 제공하는 TLE(Two Line Element)가 주로 이용된다. 하지만 관측 및 궤도 결정 특성상 수 km의 오차를 포함하므로 궤도정보의 공분산이 크다는 단점이 있으므로 충돌 분석을 수행하는데 있어 한계가 있다. 이 논문은 충돌분석 수행에 있어 TLE 정보만을 이용한 경우뿐만 아니라 정밀궤도와 TLE를 동시에 이용한 경우를 비교함으로써 충돌 불확실성의 해소방안을 제시할 계획이다.

• Journal of Digital Convergence
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• v.12 no.5
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• pp.479-490
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• 2014

The purpose of this study is to develop a tea culture therapy program development for the improvement of self-efficacy of juvenile probationers, which is a key factor of social adaptability of juvenile probationers. After developing a tea culture therapy program, this study examines the effect of the program empirically, by applying to juvenile probationers. For this purpose, this study employs an integrative approach of qualitative and quantitative methods. It is shown from the qualitative analysis that juvenile probationers' positive attitude and active participation are considerably progressed. The results from quantitative analysis indicate that the sub-dimensions of self-efficacy such as general self-efficacy and social self-efficacy are significantly improved.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.37-46
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• 2006

The outside environment is very severe while aircraft is cruising. Especially small particle of icing in cold air condition can have negative influence on aircraft performance. If ice particle is attached to leading edge of wing, it can change wing configuration and decrease flight quality. If icing particle is attached to inlet of engine, it can damage compressor blade and have negative influence to aircraft safety. We make icing simulation device with liquid air system for analyzing about variation of engine performance due to incoming of icing to engine.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.3
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• pp.345-352
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• 2011

This paper focuses on the properties analysis of 9mm bullet dual structure core to substitute current lead core by environment-friendly combination of W-Cu-Ni system high density composite materials. So the four combination samples were made of dual core with the different center of gravity location backward or forward compare to that of lead type bullet, and we experimented about the performance of 9mm bullet dual structure core. In the experimental results, the outer shape of core of four environment friendly samples on the target maintain marginally, while the current lead core bullets are completely crushed after hitting the target. The penetration depth of environment friendly samples excel seven times to lead type bullet and the three out of four samples with forward adjusted center of gravity penetrate deep as twice as ones backward. The impact tolerance of all four samples satisfies military specification, however, more firing tests are required to improve reliability of scattering distribution.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.6
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• pp.556-561
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• 2015

The actual aircraft flight training can be done, throw this platform. this paper focuses on identifying the functions with respect to software components in the development of a aerodynamics system, which is based on the functions necessary to develop the real environment aircraft system. It also design activity diagram, concept as well as class diagram. This paper presents the main features and direction of aircraft to be equipped in the future gaming platforms. By designing a pilot platform updates that allow for new aircraft models students can understand exactly what they want and aircraft. this study presents a use case based on the aerodynamic simulation CSU concept to execution.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.77-86
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• 2003

Dynamic response of baffled fuel-storage tank in turnaround motion is simulated using the ALE finite element method. Fuel-storage tank undergoes abrupt impact load caused by inertia force of internal fuel in turnaround motion. Also, large dynamic force and moment caused by this load influence structural stability and control system. In this paper, ring-type baffles are adopted to suppress the dynamic influence. Through the parametric analysis with respect to the baffle number and location, the effects of baffle on the dynamic response of baffled fuel-storage tank is analyzed. The ALE finite element method is adopted for the accurate and effective simulation of the hydrodynamic interaction between fluid and structure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.349-352
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• 2010

This is conceptual study of vitiated air heater(VAH), the necessary ground test facility, for characteristics studies of scramjet combustion and development of scramjet engines. The VAH is one of various types which provided hot air to an intake or a combustion chamber of scramjet and it must use suitable fuel to get hot combustion gas and more similar mixture gas(vitiated air) to real air. In the study, foreign VAHs being capable of providing very high temperature were researched, and injectors for VAH using LNG(CH4) or hydrogen were designed conceptually to develop scramjet vehicle.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.84-90
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• 2004

A performance evaluation is made in terms of thrust, impulse bit. and specific impulses for a set of mono-propellant hydrazine thrusters producing 0.95 lbf of nominal thrust at an inlet pressure of 350 psia. With a brief description on the hot-firing test configuration and procedures. a typical data obtained from steady-state firing mode is given directly showing the variational behavior of propellant supply pressure, mass flow rate, vacuum condition, and thrust. The performance features are successfully compared to the reference criteria of 1-lbf standard mono-propellant rocket engine. Additionally. a statistical inter-thruster treatment is concisely depicted for the justification of selected thrusters as a grouped member of flight model for spacecraft propulsion system.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.185.2-185.2
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• 2012

저궤도 위성 비행모델 기능시험은 위성체 내부 전장품들 간의 접속 확인과 조립 및 연결상태를 확인하는 시험을 우선적으로 수행한다. 위성체의 전원선 확인 시험은 전기 전자적 조립 시험에서 가장 처음으로 수행하는 시험이다. 전력조절분배장치로부터 전장품 각각의 하드웨어로 공급되는 50볼트 주전원 또는 28볼트 부전원이 정상적으로 공급하게 되는지를 검증한다. 위성체 하니스가 설치된 후, 각각의 하드웨어에 공급되는 전원의 극성 및 연속성 시험을 수행한다. 전력조절분배장치는 태양전지판으로부터 얻어진 전력이 레귤레이터에 의해 정류된 전압을 받아 릴레이나 FET를 통하여 모든 전장품에 전원을 공급하는 주요 장비이다. 전력조절분배장치 내부나 외부 하니스 오류로부터 생길 수 있는 잘못 리드된 전원으로부터 전장품을 보호하기 위하여 하니스를 하드웨어에 연결하기 전에 우선적으로 전원선 확인 시험을 수행한다. 위성체 전원선 확인 시험은 위성체와 기능시험장비를 연결하여 시리얼 명령어를 통해 전력조절분배장치 내부의 FET 동작을 조절하며, FET 동작 상태 및 전장품에 접속되는 입력 단에서의 전압 및 전원 특성 등을 점검한다. 위성체의 주전원 50볼트 라인의 연결도 확인과 부전원 28볼트 라인의 연결도 확인 및 전력제어 유닛 내부 FET의 기능 확인을 수행하며 또한, 전력제어부 외부에 공급하는 28볼트 펄스와 15볼트 펄스를 측정 검증하는 시험을 수행한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.53-63
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• 2002

The steady-state and transient performance simulation program for a turboprop engine(PT6A-62) was developed. Specially this program included some algorithms, such as flat-rated behaviors in performance and limit control algorithms to prevent the compressor surge and the compressor-turbine inlet limit temperature overshoot. In order to minimize analysis errors, on interpolation method in component characteristics using matching errors and specific heat and specific heat ratio, which are functions of temperatures were used. The developed steady state performance analysis program can handle various conditions such as altitude, bleed extraction, inlet temperature and pressure and part throttle, and the transient performance analysis program incorporated a general mode for transient simulation and a control mode for prevention of the compressor surge and the turbine inlet limit temperature overshoot.