• 한국정보전자통신기술학회논문지
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• 제10권1호
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• pp.95-101
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• 2017

자연 영상에는 일반적으로 지역성이 존재하기 때문에 인접한 픽셀 값들은 매우 유사한 값을 갖는다. 유사한 픽셀 값을 갖는 인접 픽셀들을 사용하여 실제 영상의 곡면 특성을 추정할 수 있다. 본 논문에서는 인접 픽셀 값들을 사용하여 실제 영상에 존재하는 곡면 특성을 정밀하게 추정하고, 곡면 특성을 반영하여 보간 값을 구하는 효과적인 기법을 제안하였다. 제안된 기법을 사용하여 보간 값을 구하고자 하는 부분의 곡면 특성을 추정한 후, 추정된 곡면 특성을 충실하게 반영하는 보간 값을 구하여 확대 영상을 생성하는 효과적인 영상 확대 기법은 확대 영상의 화질을 향상시킨다. 실험을 통하여 제안된 기법의 성능이 기존의 기법에 비하여 우수함을 확인하였다.

• 한국CDE학회논문집
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• 제7권3호
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• pp.190-201
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• 2002

Surfaces of many engineering structures, specially, those of ships and airplanes are commonly fabricated as doubly curved shapes as well as singly curved surfaces to fulfill functional requirements. Given a three dimensional design surface, the first step in the fabrication process is unfolding or planar development of this surfaces into a planar shape so that the manufacturer can determine the initial shape of the flat plate. Also a good planar development enables the manufacturer to estimate the strain distribution required to form the design shape. In this paper, an algorithm for optimal approximated development of a general curved surface, including both singly and doubly curved surface is developed in the sense that the strain energy from its planar development to the design surface is minimized, subjected to some constraints. The development process is formulated into a constrained nonlinear programming problem, which is on basis of deformation theory and finite element. Constraints are subjected to characteristics of the fabrication method. Some examples on typical surfaces and the practical ship surfaces show the effectiveness of this algorithm.

• 한국CDE학회논문집
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• 제11권3호
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• pp.157-163
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• 2006

Surfaces of many engineering structures, especially, those of ships are commonly made out of either single- or double-curved surfaces to meet functional requirements. The first step in the fabrication process of a three-dimensional design surface is unfolding or flattening the surface, otherwise known as planar development, so that manufacturers can determine the initial flat plate which is required to form the design shape. In this paper, an algorithm for optimal approximated development of a general curved surface, including both single- and double-curved surfaces, is established by minimizing the strain energy of deformation from its planar development to the design surface. The unfolding process is formulated into a constrained nonlinear programming problem, based on the deformation theory and finite element. Constraints are subjected to the characteristics of the fabrication method. And the design surface, or the curved shell plate is subdivided by automatic mesh generation.

• 한국컴퓨터정보학회논문지
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• 제20권1호
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• pp.63-73
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• 2015

본 논문에서는 원본 영상에 존재하는 가로축 방향과 세로축 방향의 단순 볼록 곡면 혹은 단순 오목 곡면 특성을 정밀하게 조사한 후, 다양한 곡면의 특성을 효과적으로 활용하여 실제 영상의 픽셀 값에 더욱 근접한 보간 값을 구하고 이를 사용하여 확대 영상을 생성하는 확대 영상의 화질 개선 기법을 제안한다. 제안 기법의 절차에 따라 구해진 보간 값은 실제 영상에 존재하는 단순 볼록 곡면, 단순 오목 곡면, 복합 곡면상의 값을 갖게 되기 때문에 실제 영상에 더욱 근접한 확대 영상을 생성할 수 있어 확대 영상의 화질이 향상된다. 제안 기법을 적용하여 확대한 영상의 PSNR 값이 기존의 기법들을 적용하여 확대한 영상의 PSNR 값보다 큰 것을 확인하였다.

• 한국의류산업학회지
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• 제19권5호
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• pp.635-645
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• 2017

The industry of character toys is increasing and new characters are constantly being developed. However, the development of 2D cover patterns for toys is time-consuming due to frequent pattern modifications made through trial and error. Studies are now underway to obtain 2D clothing patterns from 3D body data, however, little research has been done on 2D pattern of character toys. This study suggests efficient guidelines to develop 2D cover patterns with a reasonable accuracy and processing time. Two 3D models of a dog and rabbit were used to develop 2D cover patterns. Independent variables of this study are set as 3 levels of triangle area (small, medium, and large) that influence the efficacy of 3D and 2D pattern development. The determination of the appropriate triangular area was based on the area and shape change of the 2D pattern. A medium or large triangle area was shown to be suitable for a character dog with a smooth curved surface. However, the appropriate triangle area was small if the characteristics of the curved surface are complicated as in the case of rabbit. The head of a dog (a double-curved surface) and the curved forepaw of a rabbit (a triangular area) should be small when the characteristics of the curved surface (such as the hind leg of a rabbit having a large convex surface and a small surface area) are complicated. Grouping by 3D surface characteristics could be a suitable guideline for the triangle area selection.

• International Journal of Railway
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• 제7권2호
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• pp.57-63
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• 2014

This paper presents the optimization of suspension characteristics under the condition of curved track railway vehicles. Reducing lateral acceleration on curved track is an issue for high-speed railway vehicles. In terms of curved track running environments, reducing the lateral vibration of railway vehicles is critical to safety and curving performance. The properties of lateral damping and stiffness of both primary and secondary suspension show effect on wheel-set, bogie and car-body. Analysis for reducing the lateral vibration of rail vehicles with respect to the characteristics of both primary and secondary suspension has been developed using ADAMS/Rail. Response Surface Method has been chosen for the purpose of verifying correlation effects among design parameters. Also, this paper suggests the method for designing optimal suspension of railway vehicles on curved track. The optimization result indicates decrement of lateral acceleration on wheel-set by 3% and bogie by 1% on curved track. Finally, this paper comes to the conclusion that suspension system of railway vehicle (KTX I) is properly designed when regarding lateral vibration of railway vehicle on diverse curved track condition.

• 물과 미래
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• 제25권3호
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• pp.87-96
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• 1992

측류취소로와 만곡부가 있는 원형수로를 1:20으로 축척한 모형수로에 대해 수리모형실험을 수행하여 만곡부에서의 유속, 수위와 유황과 같은 수리학적 특성을 살펴보고, 측류취소로가 만곡부에 미치는 영향을 살펴보고자 한다. 또한 모형수로에 대해 ADI방법으로 천수방정식을 수치해석하여 얻은 만곡부에서의 수리학적 특성을 실험에 의한 것과 비교하여 사용된 수치기법을 검증하였다. 대상이 된 전영역에 대하여 수리모형실험에서 얻어진 유속, 수위와 유황은 수치해석한 결과와 잘 일치한다. 그러나 직각좌표계를 사용함으로서 상대적으로 만곡부에서 단면축소 효과가 발생하므로 수치해석으로 얻어진 유속은 만곡부에서 실험치보다 약간 크게 나타나는데, 이것은 격자간격을 줄이면 개선되리라 판단된다. 수리모형실험과 수치해석 모두 만곡부 외측의 수위가 상승하고 내측의 유속이 빨라지는 만곡부의 특성을 잘 모사하고 있다. 만곡부 직전에 측류취수로가 있을 경우 측류취수로의 영향이 만곡수로내까지 미침을 알 수 있었다.

• 한국전산유체공학회지
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• 제17권4호
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• pp.75-80
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• 2012

Due to the effect of surface tension, liquid film around a curved edge of solid surface moves from the corner to the flat surface. During this behavior of liquid film, film sagging phenomenon is easily occurred at the solid surface. Behavior of liquid film is determined with the effects of the properties of liquid film and the geometric factors of solid surface. In the present study, 2-D transient CFD simulations were conducted on the behavior of liquid film around a curved edge. The two-phase interfacial flow of liquid film was numerically investigated by using a VOF method in order to predict the film sagging around a curved edge. In the steady state of behavior of liquid film, the liquid film thickness of numerical result showed a good agreement with experimental data. After verifying the numerical results, the characteristics of behavior of liquid film were numerically analyzed with various properties of liquid film such as surface tension coefficient and viscosity. The effects of geometric factors on film sagging were also investigated to reduce the film sagging around a curved edge.

• 한국가스학회지
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• 제12권4호
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• pp.63-68
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• 2008

본 논문은 적외선 센서의 광 강도 및 효율을 증가시키기 위해 새로운 오목한 반사 벽면(curved mirror surface)과 기존의 수직 반사 벽면(vertical mirror surface)구조와의 모의해석 및 실험 결과에 대해 기술하였다. 모의해석 결과 수직 반사 벽면을 사용했을 때 적외선 센서 필터 표면에 도달하는 광의 분포는 타원 형상으로 적외선 센서 표면에 도달함을 볼 수 있고, 오목한 반사 벽면을 사용하는 경우에는 광이 원형상으로 집광되는 것을 볼 수 있었다. 따라서 초기 평행광의 면적보다 작은 면적으로 집광됨으로 인해 단위면적당 광 강도는 향상되고, 이에 따라 광학적 센서의 출력전압은 향상될 것이라 예측되었다. 이 모의해석을 근간으로 하여 $25^{\circ}C$, 45%R.H.에서 이산화탄소를 0 ppm에서 2500 ppm까지 250 ppm 간격으로 주입시켰을 때, 오목한 반사 벽면의 광 공동이 수직 반사 벽면의 광 공동보다 출력전압이 약 200 mV 증가하였다.

• Advances in nano research
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• 제5권1호
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• pp.35-47
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• 2017

This paper deals with free vibration analysis of nanosize rings and arches with consideration of surface effects. The Gurtin-Murdach model is employed for incorporating the surface effect parameters including surface density, while the small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. An analytical Navier solution is presented to solve the governing equations of motions. Comparison between results of the present work and those available in the literature shows the accuracy of this method. It is explicitly shown that the vibration characteristics of the curved nanosize beams are significantly influenced by the surface density effects. Moreover, it is shown that by increasing the nonlocal parameter, the influence of surface density reduce to zero, and the natural frequency reaches its classical value. Numerical results are presented to serve as benchmarks for future analyses of nanosize rings and arches.