• 한국군사과학기술학회지
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• 제1권1호
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• pp.128-144
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• 1998

일반적인 선형 탄성해석 경계 요소법이 초 고속 회전과 정상 열전도에 의한 열 탄성 효과가 고려된 문제에 적용되었다. 축대칭 경계 요소법 구성이 요약되었고, 등가 경계 적분 방정식의 물체력 핵 함수의 체적 적분 전환방법에 일반화된 내적과 벡터 연산법 개념이 도입되었다. 고차 경계 요소 적용을 위한 이산화 수치 해석법이 요약되었고, 소형 젯트 엔진(ADD 500)의 터어빈 로우터 디스크의 해석 결과가 유한 요소해와 비교되었다.

• 대한기계학회논문집A
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• 제20권5호
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• pp.1508-1515
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• 1996

The method of utilizing sensitivity linkages for the analysis of mechanical errors are proposed. As sources of the mechanical error, tolerances in the link length and clearances in thejoints are considered. It is demonstrated that the problem of calculating mechanical errors of a 4-bar mechanism can be transformed into a problem of conventeional velocity analysis of a sensitivity linkage. As a result of the present study, it is found and proved that the mechanical error of the output angle in the 4-Bar mechaism is represented as a simple harmonic function with respect to the relative position of the pin on the clearance circle. Also the vector representing the mechanical error of a coupler point makes, in general, an ellipse as the relative angle varies on the clearance circle. With these results we can better identify the characteristic of the mechanical errors in linkages.

• 대한기계학회논문집B
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• 제24권3호
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• pp.443-449
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• 2000

The performance of 2-frame PTV(particle tracking velocimetry) system was improved using an adaptive hybrid scheme. The original 2-frame PTV method based on the match probability concept employs global match parameters for the entire flow field. Since this does not reflect fully the detailed local velocity change, it sometimes reduces the recovery rate of velocity vectors and increases the number of erroneous vectors in the region where an extraordinary flow structure exists. In this study, the preliminary FFT-based PIV results are used as an input parameter to determine the local match parameters needed for the 2-frame particle tracking algorithm. A computer simulation using synthetic particle images was carried out to study the performance of the adaptive 2-frame PTV technique. The adaptive hybrid method shows the better performance with increasing the velocity vector recovery rate and decreasing the computation time, compared to the original 2-frame PTV method.

• 한국추진공학회지
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• 제14권5호
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• pp.1-7
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• 2010

최근 이중목 노즐(Dual Throat Nozzle, DTN)을 사용하여 추진체의 추력을 제어하는 방 이 많은 주목을 받고 있다. 이중목 노즐은 공동을 사이에 두고 두 개의 노즐 목을 가지도록 설계된다. 본 연구에서는 DTN의 기초 유동특성을 조사하기 위하여, 수치해석적인 방법을 적용하였으며, 노즐압력비와 노즐목 면적비를 변화시켰다. 수치해석에서는 축대칭, 압축성 Navier-Stokes방정식을 풀기 위하여, 유한체적법을 적용하였다. 그 결과 본 수치해석은 실험결과를 잘 예측하였으며, DTN의 성능을 추력계수와 유출계수의 항으로 상세하게 설명하였다.

• 대한기계학회논문집B
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• 제26권12호
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• pp.1699-1706
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• 2002

In this paper, the investigation about the elevation control and the formation of the free surface of magnetic fluids is carried out theoretically and experimentally on the basis of magnetic fluids is carried out theoretically and experimentally on the basis of Rosensweig' Ferrohydrodynamic Bernoulli Equation. Governing equations of magnetic fields are solved using the concept of vector potential. While applied magnetic fields are induced by 4$\times$4 electromagnet located under the magnetic fluid, the fee surface of the magnetic fluid is formed the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body force. The results of numerical simulation and experiment show the formation of the free surface of the magnetic fluid. Using PID control, an experiment for the elevation control of the free surface of magnetic fluids is performed.

• 자원환경지질
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• 제17권2호
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• pp.141-147
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• 1984

For the discussion of palaeogeomagnetic field direction and the movement and rotation of geotectonic blocks it is prerequisite to eliminate the secondary remanent magnetization component out of the NRM vector of given rock samples. Among various techniques alternating field and thermal demagnetization methods are most easily applicable and most widely used ones. Physical principle underlying these methods is the concept of relaxation time: Either with an action of external magnetic field or with an elevated temperature relaxation time of magnetic minerals can be drastically shortened. It has been furthermore shown experimentally that the secondary remanent magnetization can be more easily demagnetized than the primary remanent magnetization. Through careful stepwise demagnetization it should also be possible to discriminate the kind of various remanent magnetizations. In addition to the introduction to the underlying physical principles and experimental results of the alternating field and thermal demagnetization this paper gives various practical tips in earring out the demagnetization experiments. Each alternating field and thermal demagnetization instrumentation which is easily adaptable to domestic palaeomagnetic laboratories is also introduced. This paper provides a compact and practical introduction to the methods in palaeomagnetism and would be of interest to present workers and to those who want to embark on research in this field.

• 한국자동차공학회논문집
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• 제18권4호
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• pp.92-98
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• 2010

Virtual ground modeling is one of key topic for real-time vehicle dynamic simulation. This paper discusses about the virtual 3D road modeling process using parametric surface concept. General road data is a type of lumped position vector so interpolation process is required to compute contact of internal surface. The parametric surface has continuity and linearity within boundaries and functions are very simple to find out contact point. In this paper, the parametric surface formula is adopted to road modeling to calculate road hight. Position indexing method is proposed to reduce memory size and resource possession, and a simple mathematical method for contact patch searching is also proposed. The developed road process program is tested in dynamic driving simulation on off-road. Conclusively, the new virtual road program shows high performance of road hight computation in vast field of off-road simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.898-901
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• 1988

Up to now, using adaptive control method, Identification deals with system whose entire state variables and prameters are accessible for measurement. In practical situations, all the state variables cannot be measured and it is impossible to directly apply since the parameters of the system are unknown. Therefore, in this paper, using only input-output data, such a model of the system is not available since the parameters of the system are unknown. this leads to the concept of an adptive observer in which both the parameters and the state variable of the system are identified simultaniously. Lyapunov's direct method and Kalman-Yakubovich (K-Y) lemma are employed to ensure the stability of this schemes. The feature is that the signal and adaptive gain which is generated from filter is imposed upon feedback vector and then state variables and the unknown parameters can be identified. To show the usefulness of the proposed schemes, computer simulation result of unknown second-order system shows the effectiveness of the proposed schems.

• International Journal of Aeronautical and Space Sciences
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• 제3권1호
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• pp.74-85
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• 2002

The numerical experiment has been conducted to investigate the unsteady shock wave reflecting phenomena. The cell-vertex finite-volume, Roe's upwind flux difference splitting method with unstructured grid is implemented to solve unsteady Euler equations. The $4^{th}$-order Runge-Kutta method is applied for time integration. A linear reconstruction of the flux vector using the least-square method is applied to obtain the $2^{nd}$-order accuracy for the spatial derivatives. For a better resolution of the shock wave and slipline, the dynamic grid adaptation technique is adopted. The new concept of grid adaptation technique, which is much simpler than that of conventional techniques, is introduced for the current study. Three error indicators (divergence and curl of velocity, and gradient of density) are used for the grid adaptation procedure. Considering the quality of the solution and the numerical efficiency, the grid adaptation procedure was updated up to $2^{nd}$ level at every 20 time steps. For the convenience of comparison with other experimental and analytical results, the case of interaction between the straight incoming shock wave and a sharp wedge is simulated for various flow conditions. The numerical results show good agreement with other experimental and analytical results, in the shock wave reflecting structure, slipline, and the trajectory of the triple points. Some critical cases show disagreement with the analytical results, but these cases also have been proven to show hysteresis phenomena.

• 전기학회논문지
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• 제63권1호
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• pp.145-149
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• 2014

In this study, using X-ray cargo container scanning device and to differentiate the concept of three-dimensional information extraction applied for X-ray scanning device as an ingredient in the rotation of the X-Ray Linear Pushbroom Stereo System by introducing the geometric How to model was introduced. Three-dimensional information obtained through the matching of a single voxel space filled with a random vector operations for each voxel in the three dimensional shape reconstruction algorithm using the definition, and in time, the time required for each step were analyzed. Using OpenCV in each step by applying parallelization techniques approximately 1.8 times improvement in the processing time of the check, but do not meet the target within one minute levels. The other hand, X-ray images by the primary process to convert the point View the results of real-time stereo through a three-dimensional could feel the comfort level.