• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.777-780
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• 1998

물체의 3차원적인 정보를 복원하는 일은 그 정보의 일련된 이용에 있어서 중요한 문제이다. 이를 위해 여러가지 방법들이 연구되고 있으며, 그 중 shape from focus(SFF) 방법은 영상의 초점이 맞는 렌즈의 위치를 찾아내어 렌즈 공식에 의해 초점이 맞는 부분의 거리 정보를 구할 수 있다. 기존의 이 방법은 초점이 맞았는지의 정도를 계산하기 위한 focus measure 값들을 카메라의 광학축에 수직인 단순한 평면으로 가정하여 그 합이 최대가 되는 위치를 찾아내었다. 이를 개선하기 위해서 focused image surface(FIS) 개념이 연구되었고 그로 인해 더욱 나아진 결과를 얻었다. 물체의 FIS는 카메라 렌즈에 의해 초점이 맞게된 물체의 점들의 집합으로 이루어진 공간상의 면이다. 기하광학에 의해 물체의 모양과 FIS 상이에는 일대일 대응 관계가 있고 FIS의 형태를 구하는것이 결국은 물체의 모양을 복원하는것이다. FIS 개념을 처음 적용할 때는 물체의 모양이 부분적으로 영상 탐지기(image detector)와 같은 평면으로 가정하여 3차원 공간상에서 가능한 모든 방향의 평면에 대한 focus measure를 구하여 그 값이 최대가 되는 렌즈의 위치를 구하였다. 그러나 이러한 방법은 focus measure의 합이 정사각형의 윈도우에서 계산되기 때문에 곡면으로 이루어진 실제 물체에서는 오차르 ㄹ가지게 된다. 본 논문에서는 이와는 달이 평면이 아닌 곡면에 대한 focus measure의 합이 최대가 되는 렌즈의 위치를 구하여 이전의 방법들 보다 정확한 복원이 가능함을 보인다.

• Journal of Korea Game Society
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• v.18 no.5
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• pp.5-14
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• 2018

A lot of research has been done on image recognition technique for planar images and the performance has also been improved. However, it is difficult to recognize objects in spherical panoramic images or images in special form which are given in various environments because of the spherical distortion given in different form from the planar case. In this paper, we show that the neural network recognition approach can be used for object recognition in spherical image and suggest a method of using cubemap transform in order to increase recognition accuracy in spherical image.

• Journal of Korea Water Resources Association
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• v.42 no.9
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• pp.691-702
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• 2009

This study makes a systematic approach to Hack's law considering self-affinity and self-similarity of natural basins as well as the elongation of corresponding catchment-plan forms. Catchment-plan forms extracted from DEM appear to be the population come from the interactions of 2 hypotheses on Hack's law. It is judged that the elongation measures based on inertia moments are more intuitive than the ones based on main channel lengths. The exponent of Hack's law, h, seems to be similar to the result of Gray's study (1961). However Hurst exponent, H, being 0.96 imply that catchment-plan forms considered in this study have isotropic increasing properties with scale. From this point of view it is inferred that the shapes of the basins in this study would be more affected from self-similarity of main channel lengths than self-affinity of catchment-plan forms.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.470-478
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• 2015

A heuristic method treating a layered ocean bottom in a ray modeling is to use the plane wave reflection coefficient for multiple-layered structure, named an one-layer assumption in this paper. We examine the validity of one-layer assumption in the case of two-layered ocean bottom, and obtain a simple inequality condition depending on the sound speed ratio, the ratio of layer thickness to source-receiver range, and the grazing angle of first reflected ray. From this inequality condition, it is shown that an one-layer assumption can be applicable to ray propagation problems at mid frequencies. Finally, numerical experiments are performed in the ocean environment similar to the East Sea in Korea. Incoherent transmission loss is calculated by the geometrical beam model with the plane wave reflection coefficient for multiple-layered ocean bottom and compared with the result of SNUPE 2.0, which is a parabolic equation package developed in Seoul National University.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1A
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• pp.9-18
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• 2011

Generally the connection of structural members is assumed as hinge, rigid and semi-rigid connections. The exact tangent stiffness matrix of a semi-rigid frame element is newly derived using the stability functions considering shear deformations. Also, linearized elastic- and geometric-stiffness matrices of shear deformable semi-rigid frame are newly proposed. For the exact stiffness matrix, an accurate displacement field is introduced by equilibrium equation for beam-column under the bending and the axial forces. Also, stability functions considering sway deformation and force-displacement relations with elastic rotational spring on ends are defined. In order to illustrate the accuracy of this study, various numerical examples are presented and compared with other researcher's results. Lastly, shear deformation and semi-rigid effects on buckling behaviors of structure are parametrically investigated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.13-24
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• 1988

A geometrically nonlinear analysis procedure for plane frame structures in order to study the static and dynamic post-buckling behavior of these structures subjected to circulatory forces is presented. The elastic and geometric stiffness matrices, the mass matrix and load correction stiffness matrix are derived from the extended virtual work principle, where the tangent stiffness matrix becomes non-symmetric due to the effects of non-conservative circulatory forces. The dynamic analysis of plane frame structures subjected to circulatory forces in pre- and post-buckling ranges is carried out by integrating the equations of motion directly by the numerically stable Newmark method. Numerical results are presented in order to demonstrate the vality and accuracy of the proposed procedure.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.81-92
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• 2008

Generally the connection of members is defined as hinge or rigid. But, real joints on structure have to be considered semi-rigid connections because this permits relative rotation for members on joints. The purpose of this study is to derive a generalized tangential stiffness matrix of frames with semi-rigid connections and to develop a buckling analysis program. For the exact stiffness matrix, an accurate displacement field is introduced using an equilibrium equation for beam-columns under the bending and axial forces. Also, stability functions that consider sway deformation and force-displacement relations with rotational spring on ends were defined. In order to illustrate the accuracy of this study and the characteristics of semi-rigid for system buckling load, samples of angle-, portal- and 3-story frames with semi-rigid connections are presented, where the proposed approach is found to be in excellent agreement with other research results. Meanwhile, the application of codes such as Eurocode 3 and LRFD led to significant inaccuracies.

• Journal of radiological science and technology
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• v.30 no.1
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• pp.33-38
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• 2007

The propose of this study is a verification of the correct calculation of the dose around source and the prescription dose of Ir-192 source in the plato treatment planning system. The source and orthogonal coordinates for lateral direction and those for the anterior posterior direction were drawn on a A4 paper and then input into the system. The prescription dose was prescribed to two points with radius 1 cm in the direction of polar angle $90^{\circ} and $270^{\circ} from the center of the source. The doses of prescription point and dose points acquired from the treatment planning system were compared with those from manual calculation using the geometry function formalism derived by Paul King et al. In this analysis, the doses of prescription point were exactly consistent with each other and those of dose points were obtained within the error point of 1.85%. And the system of accuracy was evaluated within 2% of tolerance error. Therefore, this manual dose calculation used for the geometry function formalism is considered to be useful in clinics due to its convenience and high quality assurance.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.3
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• pp.185-193
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• 2003

The conventional parallelogram prediction uses only three previously traversed vertices in a single adjacent triangle; thus, the predicted vertex can be located at a biased position. Moreover, vortices on curved surfaces may not be predicted effectively since each parallelogram is assumed to lie on the same plane. In order to improve the prediction performance, we use all the neighboring vertices that precede the current vertex. After we order vortices using a vertex layer traversal algorithm, we estimate the current vertex position based on observations of the previously coded vertex positions in the layer traversal order. The difference between the original and the predicted vertex coordinate values is encoded by a uniform quantizer and an entropy coder. The proposed scheme demonstrates improved coding efficiency for various VRML test data.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.2
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• pp.173-180
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• 1994

One can see more and more photograrmmetric applications dealing with the extraction of information from images obtained with CCD (Charge Coupled Device) camera scanners. In order for this information to be useful, the scanning errors of scanners must be known through a calibration. Investigation of this study is given to the detailed procedure of the correction for scanning errors created during the scanning of photographs with CCD camera scanner using the three kinds of high resolution reseal plates prepared. The geometric corrected digital images for scanning errors were generated and the accuracy of the resulting new images for each types of plates were checked comparing its image coordinates with there corresponding ground coordinates for the check points.