• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.585-592
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• 2005

In this paper, we present the principle of virtual work, from which the exact non-linear equations of motion of a rotating ring can be derived, by using the theory of finite deformation For a thin ring of which the effect of variation in curvature across the cross-section is neglected, the radial displacement and the extensional stress are determined from the principle of virtual work at the steady state where the ring is rotating with a constant angular velocity. And also we formulate systematically the governing equations concerned to the in-plane vibrations and the out-of-plane vibrations at the disturbed state by using the principle of virtual work which is expressed with the disturbed displacements about the steady state. The formulated governing equations are classified by four models along the cases of considering or neglecting all or partly the secondary effects of flexural shear, rotary inertia, circumferential extension, and twist inertia. The natural vibrations of thin rings are analyzed, and its results are compared and discussed.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.463-467
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• 2006

Several segmentation algorithms have been proposed for DTM generation or building modeling from airborne LiDAR data. Three components are important for accurate segmentation: (i) the adjacent relationship of n-nearest points or mesh, etc. (ii) the effective decision parameters of height, slope, curvature, and plane condition, (iii) grouping methods. In this paper, we created the topology of point cloud data using the contour tree and implemented the region-growing Terrain and non-terrain points were classified correctly in the segmented data, which can be used also for feature classification.

• Bulletin of the Korean Mathematical Society
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• v.52 no.1
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• pp.301-312
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• 2015

In this paper, we study a class of spacelike rotational surfaces in the Minkowski 4-space $\mathbb{E}^4_1$ with meridian curves lying in 2-dimensional spacelike planes and having pointwise 1-type Gauss map. We obtain all such surfaces with pointwise 1-type Gauss map of the first kind. Then we prove that the spacelike rotational surface with flat normal bundle and pointwise 1-type Gauss map of the second kind is an open part of a spacelike 2-plane in $\mathbb{E}^4_1$.

• Bulletin of the Korean Mathematical Society
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• v.50 no.6
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• pp.2103-2114
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• 2013

Archimedes knew that the area between a parabola and any chord AB on the parabola is four thirds of the area of triangle ${\Delta}ABP$ where P is the point on the parabola at which the tangent is parallel to AB. We consider whether this property (and similar ones) characterizes parabolas. We present five conditions which are necessary and sufficient for a strictly convex curve in the plane to be a parabola.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.57.3-58
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• 2017

We report the detailed design of an unprecedented wideband(band7+8) corrugated feed horn in ASTE focal plane array aiming for future ALMA receiver. We have found that such design constraints as return loss, cross-polarization level, beam width and phase curvature can be controlled by optimizing critical corrugation parameters at the throat and flare region of the horn. The success of optimization manifest itself through simulated aperture effciency over 80 % at the entire frequency range. Physical implications of the resulting corrugation parameters are discussed.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.200-201
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• 2000

보상광학(Adaptive Optics)은 막 흐르는 대기 또는 매개체에 의한 왜곡을 제거 또는 보상하는 시스템이다$^{(1)}$ . 그 시스템의 구성요소 중 파동앞엣선 측정장치(Wavefront Sensor)는 그러한 왜곡을 측정하는 센서로, Shearing interferometer, Shack-Hartman, Curvature wavefront sensor등이 널리 사용되어 왔으며, Pugh$^{(2)}$ 와 Ragazzoni$^{(3)}$ 가 프라미드형의 프리즘을 이용한 동공면 파면 측정을 새로이 제시했다. 본 연구에서는 동공면 파면 측정을 전산모사하여, 제니케 다항식에 대한 센서의 결과를 얻고, 분석하였다. (중략)

• Bulletin of the Korean Mathematical Society
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• v.33 no.4
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• pp.537-544
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• 1996

Crofton's formula on Euclidean plane $E^2$ states: Let $\Gamma$ be a rectifiable curve of length L and let G be a straight line. Then $$ \int_{G \cap \Gamma \neq \phi} n dG = 2L $$ where n is the number of the intersection points of G with the curve $\Gamma$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.11a
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• pp.11-14
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• 2001

3-D compressible flow analysis was conducted by using mixing plane method for turbine system which is consisted of partial admission nozzle and rotor. Computational results are shown oblique shock wave in blade leading and trailing edge and also shown flow separation along suction surface of blade due to abrupt blade curvature. But computational results are well agree with 1-D calculation results and experimental data.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2001.11a
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• pp.111-117
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• 2001

The problem of the vibration of arches has become a subject of interest for many investigators due to Its importance in many practical applications. The early investigators into the in-plane vibration of rings were Hoppe $^{1)}$ and Love $^{2)}$ . Love $^{2)}$ improved on Hoppe's theory by allowing for stretching of the ring. Lamb $^{3)}$ investigated the statics of incomplete ring with various boundary conditions and the dynamics of an incomplete free-free ring of small curvature.(omitted)

• Honam Mathematical Journal
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• v.40 no.4
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• pp.701-718
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• 2018

In this paper, we will study the constant mean curvature (CMC) surfaces foliated by ellipses in three dimensional Euclidean space $E^3$. We prove that: (1): Surfaces foliated by ellipses are CMC surfaces if and only if it is a part of generalized cylinder. (2): All surfaces foliated by ellipses are not minimal surfaces. (3): CMC surfaces foliated by ellipses are developable surfaces. (4): CMC surfaces foliated by ellipses are translation surfaces generated by a straight line and plane curve.