• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.32-32
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• 2011

파묻힌 성단 NGC1333은 광학영역에서는 성운이 별을 가리고 있어서 관측 연구가 힘든 천체이다. 이 연구에서는 광학영역이 아닌 근적외선영역의 관측 자료를 이용하여 NGC1333 내 전주계열(pre-main sequence) 변광성을 찾아내었다. 관측 자료는 2005년11월부터 2007년 10월까지 미국 버지니아대학 Fan mountain 관측소의 31인치 반사망원경에 부착된 근적외선 카메라 Fancam에서 얻어졌다. Stetson 변광 지수(Stetson, 1996)를 이용해 변광 여부를 정하였다. 별 탄생 지역에서의 등연령곡선 모형을 적용한 색-등급도를 그리고 등연령곡선과 소광 현상 보정을 이용해 각 별들의 질량을 추정하였다.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.641-646
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• 2002

A new damage detection technique using static displacement data was developed, in order to assess the structural integrity of bridge structures. In conventional damage assessment techniques using dynamic response, the variation of natural frequencies is intrinsically insensitive to the damage of the bridge: thus, it is usually difficult to obtain them from the measured data. The proposed detection method enables the estimation of the stiffness reduction of bridges using the static displacement data that are measured periodically, without requiring a specific loading test. Devices such as a laser displacement sensor can be used to measure static displacement data due to the dead load of the bridge structure. In this study, structural damage was represented by the reduction in the elastic modulus of the element. The damage factor of the element was introduced to estimate the stiffness reduction of the bridge under consideration. Likewise, the proposed algorithm was verified using various numerical simulations and compared with other damage detection methods. The effects of noise and number of damaged elements on damage detection were also investigated. Results showed that the proposed algorithm efficiently detects damage on the bridge.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.775-784
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• 2000

Nitrate dry deposition fluxes were directly measured using knife-leading-edge surrogate surface (KSS) covered with greased strips and a water surface sampler (WSS). The average gaseous flux ($8.3mg/m^2/day$) was much higher than the average particulate one ($3.0mg/m^2/day$). The best fit gas phase mass transfer coefficient (MTC) of $HNO_3$ was obtained by linear regression analysis between measured gaseous flux containing nitrogen compounds and measured ambient $HNO_3$ concentration. The result showed that the MTCs of $HNO_3$ were approximately two times higher than those of $SO_2$. Especially, during the ozone action day, measured gaseous fluxes containing nitrogen compounds were much higher than those ones calculated as the product of measured ambient $HNO_3$ concentration and gas phase MTC of $HNO_3$, which is calculated from MTC of $SO_2$ using Graham's diffusion law. This result indicated that other nitrogen compounds except $HNO_3$ contributed to gaseous flux containing nitrogen compounds into the water surface sampler. The theoretical calculations suggest the contributions of nitrous acid ($HNO_2$) and PAN to the gaseous dry deposition flux of nitrogen containing compounds to the WSS.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.1-6
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• 2012

The accurate information of mass properties is required for the precise control of the spacecraft. The mass properties, mass and inertia, are changeable by some reasons such as consumption of propellant, deployment of solar panel, sloshing, environmental effect, etc. The gyro-based attitude data including noise and bias reduces the control accuracy so it needs to be compensated for improvement. This paper introduces a real-time inertia estimation method for the attitude determination of STSAT-3, Korea Science Technology Satellite. In this method we first filter the gyro noise with the Extended Kalman Filter(EKF), and then estimate the moment of inertia by using the filtered data from the EKF based on the Recursive Least Square(RLS).

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.146.1-146.1
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• 2011

최근의 관측에 의하면 우리 은하의 헤일로내 field에 위치한 subdwarf B 항성이 헬륨이 증가된 구상성단의 푸른 수평계열성 ( Extreme Blue Horizontal Branch ) 과 동일한 기원을 가질 것으로 예측된다. 초기 우주 환경과 비슷한 헬륨 함량을 보이는 환경에서는 Building Block 내부 이외에는 헬륨이 충분히 증가된 가스를 공급할 수 없기 때문에 이러한 기원을 가지는 sdB 항성의 개수를 예측함으로써 우리 은하의 초기 Building Block으로 부터 얼마나 많은 수의 항성이 헤일로에 뿌려졌는지 예측할 수 있다. 우리는 우리 은하내 나이가 많은 항성들로 이루어진 헤일로와 Bulge 내에 이러한 기원을 가지는 sdB 항성의 개수를 예측한 결과, 초기 Building Block으로 부터 유입된 sdB 항성이 최소 8만 여개 이상일 것으로 추정하였다. 이 개수는 우리 은하 구상 성단 중 은하 Building Block의 잔재로 생각되는 성단에 존재하는 헬륨이 증가된 수평계열성의 총 합의 10배 이상의 규모에 해당한다. 이는 이들 성단이 은하 생성 초기에는 현재의 질량 규모보다 최소 10배 이상 무거웠을 것이라는 가정과 일치하는 결과이다.

• Bulletin of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.52-57
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• 1994

본 개발에서는 주로 진동응답의 추정법에 대하여 검토하고 큰 성과를 얻었다. 이를 실제 설계에 활용해 나가는 것이 앞으로의 기본적인 과제이다. 또 이를 앞으로도 계속 개발해 나가기 위해서 는 다음과 같은 개발과제들을 들 수 있다. 1) 진동응답추정 .계산model 본 계발에는 Oil tanker와 산적화물선의 in-put generator(I/G)을 개발하였다. 이 이외의 선종 에 대하여도 본 개발에 의한 방법을 적용하게 되면 보다 정도 높은 계산 model로 새로이 refine해 나갈 수가 있다. .실선mode 해석전용 본 개발에 의하여 얻은 실선 mode해석 방법에 의하면 실선 계측으로부터 정확한 진동질량(m) 과 감쇄계수(d)를 얻게 된다. 이와 같은 m값과 d값의 자료를 더 축적하게 되면 진동응답 계 산정도를 한층 더 높일 수 있다. 2) 진동 제어 .종래의 설계방법과 본 개발에 의한 계산방법을 종합 적용하게 되면, 최적의 구조설계의 실용화 와 진동의 제어가 가능하게 될 것이다. .Enging, propeller 자체의 기진력을 경감시키는 연구는 본 개발에 들지 않고 앞으로의 과제로 남는다. .본 신형 주기방진stay의 개발은 본 진동제어의 idea에 도입하게 되면 또 다른 새로운 개발이 가능하다. .종래의 재료와 새로운 고성능 재료를 조합하게 되면 진동재어재료로서의 실용화가 가능하다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.05a
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• pp.227-230
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• 2002

The Loose Part Monitoring System(LPMS) has been designed to detect, locate and evaluate detached or loosened parts and foreign objects in the reactor coolant system. In this paper, at first, we presents an application of the back propagation neural network. At the preprocessing step, the moving window average filter is adopted to reject the low frequency background noise components. And then, extracting the acoustic signature such as Starting point of impact signal, Rising time, Half period, and Global time, they are used as the inputs to neural network. Secondly, we applied the neural network algorithm to LPMS in order to estimate the mass of loose parts. We trained the impact test data of YGN3 using the backpropagation method. The input parameter for training is Rising Time, Half Period, Maximum amplitude. The result showed that the neural network would be applied to LPMS. Also, applying the neural network to the Practical false alarm data during startup and impact test signal at nuclear power Plant, the false alarms are reduced effectively. 1.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.923-930
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• 2009

In this paper, we introduce a satellite conceptual design software which can be used for outlining a new satellite as well as for educational purpose. This software consists of three commercial tools: MATLAB, STK(Satellite Tool Kit), and Excel. The management of the design software is done by MATLAB which provides basic calculations, GUI(Graphical User Interface), Excel data base management, and STK control. STK, an orbital simulation software developed by AGI, takes a part of obtaining accurate orbital information of a satellite. Excel, a product of Microsoft, is used for the data base of previous satellites and for the saving place of temporary and final results of the software. The conceptual design of a satellite is to roughly estimate power system and mass. In the power system design, the sizes of solar array and battery are determined. Based on the database of existing satellites, we can estimate the subsystems's mass fraction of a target satellite. Design examples for Kompsat 1 and 2 are suggested for verification of the developed software.

• Nuclear Engineering and Technology
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• v.13 no.3
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• pp.121-129
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• 1981

Three most outstanding maximum flow rate formulas are identified from many existing models. Outlines of the three limiting mass flow rate models are given along with computational procedures to estimate approximate amount of fission products released from a containment to environment for a given characteristic hole size for containment-isolation failure and containment pressure and temperature under a loss of coolant accident. Sample calculations are performed using the critical ideal gas flow rate model and the Moody's graphs for the maximum two-phase flow rates, and the results are compared with the values obtained from the mass leakage rate formula of CONTEMPT-LT code for converging nozzle and sonic flow. It is shown that the critical ideal gas flow rate formula gives almost comparable results as one can obtain from the Moody's model. It is also found that a more conservative approach to estimate leakage rate from a containment under a LOCA is to use the maximum ideal gas flow rate equation rather than tile mass leakage rate formula of CONTEMPT-LT.

• Geotechnical Engineering
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• v.2 no.2
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• pp.29-36
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• 1986

In this study, a random vibration technique to anaiyze the vertical vibration of rigid circular footings on sand whose material properties are not previously determind is proposed. Total of 11 circular model footings varing mass ratio and radius are constructed for the vibration experim eat and the elastic half space is represented by compacted sand layer From the random vibration experiments, it is found that the technique suggested in this study gives more accurate prediction of circular footing behavior under vertical vibration than the simplified analog which assumes the subsoils as elastic half space. The predicted resonant frequene iris agree very well with the measured values from the slnusoidal vibration experiments. The ratio of the predicted resonant amplitudes to the measured values vary between 0.5 and 1,35 for the site used for the vibration experiments in this study.