• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.3
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• pp.283-291
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• 2011

In case of metric cameras, not only fiducial marks but also various parameters related to camera lens are provided to users for the interior orientation process. The parameters have been acquired through precise camera calibration in laboratory by camera maker. But, in case of non-metric cameras, the interior orientation parameters should be determined in person by users through camera calibration with great number of control points. The interior orientation parameters of metric cameras are practically used for long time. But in case of non-metric cameras, the long-term stability of the interior orientation parameters have not been established. Generally, the interior orientation parameters of non-metric cameras are determined in every photogrammetric work. It's been an obstacle to use the non-metric camera in photogrammetric project because so many control points are required to get the interior orientation parameters. In this study, camera calibrations and photogrammetric observations using a non-metric camera have been implemented 25 times periodically for 6 months and the results have been analyzed. As a result, long-them stability of the interior orientation parameters of a non-metric camera is analyzed.

• The Journal of the Acoustical Society of Korea
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• v.31 no.3
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• pp.142-150
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• 2012

The waveguide finite element (WFE) method is a useful numerical technique to investigate wave propagation along waveguide structures which have uniform cross-sections along the length direction ('x' direction). In the present paper, the vibration and radiated noise of the submerged pipe with fluid is investigated numerically by coupling waveguide finite elements and wavenumber boundary elements. The pipe and internal fluid are modelled with waveguide finite elements and the external fluid with wavenumber boundary elements which are fully coupled. In order to examine this model, the point mobility, dispersion curves and radiated power are calculated and compared for several different coupling conditions between the pipe and internal/external fluids.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.295-299
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• 1994

두꺼운 원통형 쉘은 공학적인 문제에서 많이 사용된다. 쉘 내부에 임피던스가 큰 유체와 구조물이 있을 때 쉘을 포함한 진동해석은 이론적인 해석이 매우 어렵다. 쉘 내부에 있는 유체의 임피던스가 공기에 비하여 매우 클 경우 쉘과 유체, 내부의 구조물과 유체사이의 구조물-유체 상호작용(structure-fluid interaction)이 고려되어야 한다. 얇은 원통형 쉘에 대해서는 상용 유한요소 코드를 이용하여 구조물-유체 상호작용을 고려한 진동해석이 많이 수행되었으나 축대칭 두꺼운 원통형 쉘에 대해서는 연구가 수행되지 않고 있다. 본 연구에서는 NASTRAN, ANSYS 같은 상용 유한요소 코드에서 지원되지 않는 축대칭 두꺼운 원통형 쉘 내부에 유체와 강체요소가 있을 경우 이에 대한 유한요소 코드를 개발하고, 구조물-유체 상호작용을 고려하여 진동해석을 하였다.

• Korean Journal of Remote Sensing
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• v.33 no.5_3
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• pp.787-798
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• 2017

In the present study, the interior orientation parameters were computed by using various kinds of methods. Five DSMs (Digital Surface Models) in total were produced by applying interior orientation parameters to the image processing, and the accuracy was evaluated. In order to use interior orientation parameters as independent variables of DSM accuracy, flight parameters and exterior orientation parameters that can affect the accuracy of DSM were set to be the only fixed variables. From the results of the present study, the RMSE of campaign 3-2 was found to be 0.0305 m, which was the most favorable result. Thus, it is advisable to produce DSM by adjusted interior parameters after figuring out the interior orientation parameters using a camera calibration program at laboratory environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.181-184
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• 2012

기존에 제시된 Lin 과 Liu (1999)의 VOF 기법을 이용한 내부 조파 방법을 레블셋 기법에 적용하였다. 기하학적으로 유리한 유한요소법을 이용하여, Navier-Stokes 방정식의 공간차분에는 Characteristic Galerkin 기법을, 시간차분에는 Fractional Four-Step 기법을 적용하였다. 그림에 보인 바와 같이 중심(x=0)에서 전파하는 경우, 외부조파에 의한 영역내 재반사 문제가 해결되어 선형파를 의도한 바대로 잘 조파할 수 있었다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.387-393
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• 2006

In this paper, a spectral element model is developed for the uniform straight pipelines conveying internal unsteady fluid flow. The spectral element matrix is formulated by using the exact frequency-domain solutions of the pipe-dynamics equations. The spectral element dynamic analysis is then conducted to evaluate the accuracy of the present spectral element model and to investigate the vibration characteristics and internal fluid characteristics of an example pipeline system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.437-448
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• 2000

In this study, a numerical analysis method for soil-pile interaction in frequency domain problem is presented. The total soil-pile interaction system is divided into two parts so called near field and far field. In the near field, beam elements are used lot a pile and plain strain finite elements for soil. In the far field, dynamic fundamental solution for multi-layered half planes based on boundary element formulation is adopted lot soil. These two fields are coupled using FE-BE coupling technique. In order to verify the proposed soil-pile interaction analysis, the dynamic responses of pile on multi-layered half planes are simulated and the results are compared with the experimental results. Also, various numerical analyses of piles considering different conditions of soil-pile interaction system are performed to examine the dynamic behavior of the system. It has been found that the developed method which satisfies the radiation conditions of multi-layered half planes can be applied to various structure systems effectively in frequency domain.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.3
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• pp.123-132
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• 2021

To determine 3D(three-dimensional) positions using a stereo-camera in close-range photogrammetry, camera calibration to determine not only the interior orientation parameters of each camera but also the relative orientation parameters between the cameras must be preceded. As time passes after performing camera calibration, in the case of non-metric cameras, the interior and relative orientation parameters may change due to internal instability or external factors. In this study, to evaluate the stability of the stereo-camera, not only the stability of two single cameras and a stereo-camera were analyzed, but also the three-dimensional position accuracy was evaluated using checkpoints. As a result of evaluating the stability of two single cameras through three camera calibration experiments over four months, the root mean square error was ±0.001mm, and the root mean square error of the stereo-camera was ±0.012mm ~ ±0.025mm, respectively. In addition, as the results of distance accuracy using the checkpoint were ±1mm, the interior and relative orientation parameters of the stereo-camera were considered stable over that period.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.287-290
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• 2000

본 연구에서는 압전세라믹스와 금속판으로 구성된 음향트랜스듀서를 모델로 설정하고, 원형평판으로부터 방사되는 내부음장과 트랜스듀서의 외부로 방사되는 음향특성을 수치 해석하였다. 음향트랜스듀서의 내부 유니트를 요소 분할하며 경계조건을 적용시키고, 유한요소법을 이용하여 내부의 음장 분포와 음압 변화량을 가시화하였다. 그리고 트랜스듀서 외부로 방사되는 음압은 가상경계면 외부를 요소분할한 후 다양한 주파수에서 음압 기울기와 등압선을 수치해석하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.4
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• pp.237-247
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• 1997

A geometrical inverse heat conduction problem is solved for the infrared scanning cavity detection by the boundary element method using minimal energy technique. By minimizing the kinetic energy of temperature field, boundary element equations are converted to the quadratic programming problem. A hypothetical inner boundary is defined such that the actual cavity is located interior to the domain. Temperatures at hypothetical inner boundary are determined to meet the constraints of mea- surement error of surface temperature obtained by infrared scanning, and then boundary element analysis is peformed for the position of an unknown boundary (cavity). Cavity detection algorithm is provided, and the effects of minimal energy technique on the inverse solution method are investigated by means of numerical analysis.