• Transactions of Materials Processing
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• v.26 no.1
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• pp.11-17
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• 2017

In this study, process analysis of elbow-shaped tubes using a mandrel has been performed. To reach the final shape within the dimensional tolerance, the process analysis has been performed at various processing parameters such as tube dimensions, the curved cutting surface and the radius of curvature. The area outside the boundary of the target shape was expressed as a quantitative index to analyze the formability. The validation experiments have also been performed in order to increase the reliability of the process analysis. For the processing of elbow-shaped tubes, it is preferable to make the angle of the portion where the punch touches the tube smaller than the opposite angle. And the convex cutting surface is advantageous due to the increased contacts between the punch and the tube ends during the bending process. Elbow tube having larger radius of curvature shows higher dimensional accuracy due to the relatively uniform strain distribution.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.38-43
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• 2002

Die-less forming is a cold forming process which is to bend thick flat plates into compound curved plates using two asymmetric rollers. This forming method has several advantages compared with line heating which is widely used to fabricate compound curved pieces in shipyards. The die-less forming, however, has scarcely been studied. Even the deformation mechanism in this forming process has not been understood clearly. So, in this paper, the deformation characteristics of die-less forming is investigated analytically and numerically. for the analytic investigation, slab method based on equilibrium equation is applied. And the mechanism of curvature generation is derived for the asymmetry in roller applied. And three dimensional numerical analyses are performed with realistic modeling of interactions between the rollers and work-piece using finite element program, ABAQUS. It is shown that curvature generation is mainly due to the difference of normal positive strain distribution between the top and bottom surface of the work-piece. And a convex-type curved plate is formed if the center region of the work-piece is rolled with asymmetric rollers of which the lower is larger than the upper in diameter.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.6
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• pp.675-687
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• 2009

In general, the forming process of the curved hull plates consists of sub tasks, such as roll bending, line heating, and triangle heating. In order to complement the automated curved hull forming system, it is necessary to develop an algorithm to classify the curved hull plates of a ship into standard shapes with respect to the techniques of forming task, such as the roll bending, the line heating, and the triangle heating. In this paper, the curved hull plates are classified by four standard shapes and the combination of them, or saddle, convex, flat, cylindrical shape, and the combination of them, that are related to the forming tasks necessary to form the shapes. In preprocessing, the Gaussian curvature and the mean curvature at the mid-point of a mesh of modeling surface by Coon's patch are calculated. Then the nearest neighbor method to classify the input plate type is applied. Tests to verify the developed algorithm with sample plates of a real ship data have been performed.

• Journal of Oriental Medical Thermology
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• v.9 no.1
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• pp.51-56
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• 2011

Purpose : The purpose of this study is to report the comparison of X-ray and Digital Infrared Thermographic Imaging (DITI) of a patient with idiopathic scoliosis. Method: The patient in this case was a 25-year-old female. Her chief complaint was a pain in lumbar, scapular and shoulder regions. We examined her with DITI and X-ray. And then We compared DITI and X-ray. Results: Cobb's angle of thoracic spine was $24.78^{\circ}$ as a primary curve. Cobb's angle of thoracolumbar spine was $17.63^{\circ}$. Temperature on convex side of the thoracic spine was $0.3^{\circ}C$ higher than the other side. Temperature on convex side of cervical spine was $1.4^{\circ}C$ higher than the other side. There was no correlation curvature degree with temperature difference. Conclusion : There was a tendency that the temperature on convex side of the spine is higher than the other side of the spine. DITI is a useful assessment tool when it is used with X-ray as a diagnostic tool of idiopathic scoliosis. Further studies are needed.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.5
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• pp.809-815
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• 2020

A number of investigations and studies have been conducted in various fields regarding the sediment disasters of Mt. Woomyeon that occurred in July 2011. We collected and compared the topographic information of the general points where debris flows did not occur and the collapse points where the debris flow occurred in order to find out the characteristics of the collapse points in Woomyeon mountain. The collected topographic information is altitude, curvature, slope, aspect and TPI(topographic position index). As a result of comparison, there were relatively many collapse points at an altitude of 210m to 250m, and at a slope of 30° to 40°. In addition, the risk of collapse was low in a cell where the curvature was close to 0, and the risk was higher in concave terrain than in convex terrain. In the case of TPI, there was no statistical difference between the general points and the collapse points when the analysis radius was larger than 200m, and there was a correlation with the curvature when the analysis radius was smaller than 50m. In the case of debris flows that are affected by artificial structures or facilities, there is a possibility of disturbing the topographic analysis results. Therefore, if a research on debris flow is conducted on a mountain area that is heavily exposed to human activities, such as Woomyeon mountain, diversified factors must be considered to account for this impact.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.296-299
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• 2011

임상 진단에서 환자의 의료 영상을 시각적으로 보고 해석하거나 또는 수작업으로 영상을 해석하여 진단에 이용한다. 이러한 수작업의 불편함을 해소하기 위하여 의료 영상처리 알고리즘들이 많이 연구되어오고 있다. 그 중 영상처리의 정확도 부분이 많은 문제가 되고 있는데, 특히 세포영상에서는 인접한 영역의 분할이 가장 중요시되고 있다. 본 논문은 이러한 인접영역의 분할을 위해 객체의 기하 정보인 곡률(Curvature) 정보와 컨벡스 헐(Convex Hull)을 통한 분할 방법을 제안하고자 한다. 실험 결과 87.5%의 정확도가 검출되었으며 향후 인접 객체의 내부정보까지 고려한 효과적인 분할 방법을 연구하고자 한다.

• Journal of the Korean Society of Visualization
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• v.1 no.1
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• pp.82-91
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• 2003

The study of swirl flow has been of technical and scientific interest because it has an internal recirculation field and its tangential velocity is related to the curvature of the streamline. The fluid flow for ducts or elbows of an internal engine has been much studied through numerical methods and experiments, but studies about swirl flow has been insufficient. Using the PIV (Particle Image Velocimetry) method, this study found the time-mean velocity distribution, time-mean turbulent intensity, with swirl and without swirl flow for Re=10,000, 15,000, 20,000, and 25,000 along longitudinal sections and the results appear to be physically reasonable. In addition, axial velocity distribution is compared with that of Jeong's, Kodadadi's and Murakami's. It was found that the highest velocity of swirl and non-swirl flow occurs in the opposite position at the center of a round tube, $\phi$=45$^{\circ}$

• Bulletin of the Korean Mathematical Society
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• v.53 no.6
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• pp.1651-1670
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• 2016

In this paper, we investigate exponentially biharmonic maps u : (M, g) ${\rightarrow}$ (N, h) from a Riemannian manifold into a Riemannian manifold with non-positive sectional curvature. We obtain that if $\int_{M}e^{\frac{p{\mid}r(u){\mid}^2}{2}{\mid}{\tau}(u){\mid}^pdv_g$ < ${\infty}$ ($p{\geq}2$), $\int_{M}{\mid}{\tau}(u){\mid}^2dv_g$ < ${\infty}$ and $\int_{M}{\mid}d(u){\mid}^2dv_g$ < ${\infty}$, then u is harmonic. When u is an isometric immersion, we get that if $\int_{M}e^{\frac{pm^2{\mid}H{\mid}^2}{2}}{\mid}H{\mid}^qdv_g$ < ${\infty}$ for 2 ${\leq}$ p < ${\infty}$ and 0 < q ${\leq}$ p < ${\infty}$, then u is minimal. We also obtain that any weakly convex exponentially biharmonic hypersurface in space form N(c) with $c{\leq}0$ is minimal. These results give affirmative partial answer to conjecture 3 (generalized Chen's conjecture for exponentially biharmonic submanifolds).

• Bulletin of the Korean Mathematical Society
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• v.52 no.3
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• pp.925-933
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• 2015

It is well-known that the area of parabolic region between a parabola and any chord $P_1P_2$ on the parabola is four thirds of the area of triangle ${\Delta}P_1P_2P$. Here we denote by P the point on the parabola where the tangent is parallel to the chord $P_1P_2$. In the previous works, the first and third authors of the present paper proved that this property is a characteristic one of parabolas. In this paper, with respect to triangles ${\Delta}P_1P_2PQ$ where Q is the intersection point of two tangents to X at $P_1$ and $P_2$ we establish some characterization theorems for parabolas.

• Journal of the Korean Mathematical Society
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• v.52 no.5
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• pp.1097-1108
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• 2015

In this paper, we investigate p-biharmonic maps u : (M, g) $\rightarrow$ (N, h) from a Riemannian manifold into a Riemannian manifold with non-positive sectional curvature. We obtain that if ${\int}_M|{\tau}(u)|^{{\alpha}+p}dv_g$ < ${\infty}$ and ${\int}_M|d(u)|^2dv_g$ < ${\infty}$, then u is harmonic, where ${\alpha}{\geq}0$ is a nonnegative constant and $p{\geq}2$. We also obtain that any weakly convex p-biharmonic hypersurfaces in space formN(c) with $c{\leq}0$ is minimal. These results give affirmative partial answer to Conjecture 2 (generalized Chen's conjecture for p-biharmonic submanifolds).