• Proceedings of the Korean Society of Computer Information Conference
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• 2022.01a
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• pp.353-355
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• 2022

본 논문에서는 외력에 의해 헤어가 움직일 때, 전체가 아닌 변형률이 큰 부분에 입자 제어점을 추가하여 베지에 곡선을 그리는 적응형 헤어 시뮬레이션 기법을 제안한다. 일반적인 정규화 샘플링을 통한 물리 시뮬레이션은 헤어의 움직임에 대한 정확도가 높은 반면, 계산량이 증가하고 메모리를 많이 차지하기 때문에 비효율적이다. 이 문제는 굽힘이 일어나는 특정 부분만 활용한 적응형 샘플링을 통해 해결할 수 있으며, 메모리뿐만 아니라 속도 측면에서도 모두 우수한 성능을 보인다. 본 논문에서 제안하는 방법을 이용한 굽힘 샘플링 기법은 헤어의 굽힘 패턴에 따라 실시간으로 표현되며 자연스럽고 부드러운 실제 헤어와 유사한 결과를 보여준다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.28 no.1
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• pp.22-32
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• 2024

In this paper we present a method of conic section approximation by hexic Bézier curves. The hexic Bézier approximants are G³ Hermite interpolations of conic sections. We show that there exists at least one hexic Bézier approximant for each weight of the conic section The hexic Bézier approximant depends one parameter and it can be obtained by solving a quartic polynomial, which is solvable algebraically. We present the explicit upper bound of the Hausdorff distance between the conic section and the hexic Bézier approximant. We also prove that our approximation method has the maximal order of approximation. The numerical examples for conic section approximation by hexic Bézier curves are given and illustrate our assertions.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.137-145
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• 2016

A novel tracking method is proposed to find coronary artery using high-order curve model in coronary CTA(Computed Tomography Angiography). The proposed method quickly generates numerous artificial trajectories represented by high-order curves, and each trajectory has its own cost. The only high-ranked trajectories, located in the target structure, are selected depending on their costs, and then an optimal curve as the centerline will be found. After tracking, each optimal curve segment is connected, where optimal curve segments share the same point, to a single curve and it is a piecewise smooth curve. We demonstrated the high-order curve is a proper model for classification of coronary artery. The experimental results on public data set sho that the proposed method is comparable at both accuracy and running time to the state-of-the-art methods.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.1
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• pp.75-82
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• 1991

The present paper describes a preliminary design method by using the computer graphics for creation of the fore and after body profiles of fishing vessel. It is well known that the Form Parameter design method has some merits at an early stage of design, and the B-spline curve generation technique has some prior properties in representing hull form with the computer graphic. The B-spline curve generation technique combined with the form parameter design method is employed to generate the profiles of fishing vessel. For fore body the stem profiles with bulbous bulb or without one are considered. And for after body the stern profiles of cruiser type and the transom type are generated with stern bulb or with shoe piece. Several examples will shown.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.859-864
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• 2006

Mean shift 는 데이터의 특징을 잘 살려내는 None-parametric 방법으로, 특히 영상처리분야에서 많은 각광을 받아왔다. 하지만 좋은 결과를 보장하는 뛰어난 성능에도 불구하고, 높은 메모리소요와 긴 처리시간에 기인하여, 비디오처리 등의 분야에 적용하기엔 현실적인 제약점이 있다. 상기한 제약점을 극복하기 위해, 본 시스템은 비디오를 분석하여 전경과 후경으로 나눈다. 본 논문은 전경으로 분류된 부분에 대해 각 분리된 개체를구분하고, 좌표변환(coordinate shift)을 실행하여 연산을 할 비디오의 연산의 규모를 줄이는 방법론을 제시한다. 이러한 처리로 매우 많은 처리시간이 단축됨을 실험을 통해 알 수 있었다. 다음으로, 나뉘어진 전경에 3D mean shift를 적용하여 생성된 결과물에 대하여 3D cluster data structure 를 생성하고, 이를 이동하여 인터랙티브 에디팅이 가능하도록 하였다. 후경으로 나뉜 데이터는 이미지 한 장으로 축약이 되며, 2D mean shift 기반의 interactive cartooning system 을 통하여 만화화가 된다. 본 논문은 만화 특유의 단순한 톤을 표현하기 위해, 세밀한 분할이 필요한 부분과 그렇지 않은 부분을 따로 구분하여 처리하는 레이어처리방법을 제안한다. 위의 과정을 여러 실사이미지에 적용, 실험해본 결과 기존의 연구결과에 비해 매우 짧은 시간 내에 대상의 특징이 잘 나타낸 양질의 결과물이 생성되었다. 이러한 결과물은 출판, 영상편집분야 등 여러 분야에서 요긴하고 간편하게 사용될 수 있을 것으로 생각된다.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.3
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• pp.23-31
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• 2018

This paper describes the effect of advice information for arriving aircraft landing order on the air traffic controller's work efficiency. The air traffic control simulator used in the experiment was modeled on the basis of the aircraft parameters from BADA, gamma-command model and the 4-dimensional trajectory using the Bezier curve. The simulation results show that advice information was helpful for the performance of the work for users who did not have the air traffic control training. On the other hand, in case of users who have experience in air traffic control training, the work efficiency was lowered when the advisory information that does not reflect the user's intention is provided. Therefore, it can be seen that the effect of improving the work efficiency through advice information can be limited depending on the skill level of the air traffic controllers and the complexity of the air traffic situation.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.155-164
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• 1999

In this paper, the prototype of SIS(Simulated Implantation System) for human femoral head is introduced. SIS is a software which carries on a virtual femoral head replacement surgery including 3d visualization as well as various numeric analyses between a patient's femur and artificial femur through certain stages of the image processing and of the computer graphics. Also, processes required after acquiring consecutive CT-images and projected image of an artificial femur are discussed, and the corresponding results including prototype of SIS are given.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1418-1425
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• 2003

In CAD systems, a surface to be machined is expressed by a series of curves, such as B-spline, Bezier and NURBS curves, which compose the surface and then in CAM systems the curves are divided into a large number of line or arc segments. These divided movement commands, however, cause many problems including their excessive size of NC data that makes almost impossible local adjustment or modification of the surface. To cope with those problems, the necessity of real-time curve or surface interpolators was embossed. This paper presents an efficient real-time tool-path generation method fur interpolation of NURBS surfaces in CNC machining. The proposed tool-path generation method is based on an improved iso-scallop strategy and can provide better precision than the existing methods. The proposed method is designed such that tool-path planning is easily managed in real-time. It proposed a new algorithm for regulation of a scallop height, which can efficiently generate tool-paths and can save machining time compared with the existing method. Through computer simulations, the performance of the proposed method is analyzed and compared with the existing method in terms of federate, total machining time and a degree of constraint on the scallop height.

• 유체기계공업학회:학술대회논문집
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• 1998.02a
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• pp.128-135
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• 1998

Procedures and results of aerodynamic design of a centrifugal compressor are presented for development of a 40kW class turbogenerator gas turbine. Specification of higher level of total pressure ratio of 4 and total efficiency of $80\%$ requires advanced methods of design and analysis. In the meanline design/analysis, a method with conventional loss modeling and a method with the two-zone model are alternately used for more reliable prediction. In the impeller blade generation, a series of Bezier curve are combined to produce meridional contours and distributions of blade camber angle and blade thickness. Intermediate profiles of blades are repeatedly produced and changed to be finally fixed through quasi-three dimensional Euler flow analysis. Three dimensional compressible turbulent flow analysis is then performed for the impeller to be confirmed in the final step of design. Satisfactory results in the aerodynamic performance are obtained, which assures that there is no need of aerodynamic re-design.

• Transactions of Materials Processing
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• v.8 no.5
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• pp.471-481
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• 1999

The properties of deformed products are generally dependent upon the distribution of microstureture. It is, therefore, necessary to make the distribution of microstureture uniform in order to achieve the best balance of properties in the final product. This is often a demanding task, even for conventional materials. It is become essential to achieving mechanical integrity and a desired combination of microstructure and properties. The objective mechanical integrity and a desired combination of microsttucture and properties. The objective of this study is to design the optimal die profile which can yield more uniform microstructure in hot extruded product. The microstructure evolution, such as dynamic and static recrystallization as well as grain growth, is investigated using the program com-bined with yada and Senuma's empirical equations and rigid-thermoviscoplastic finite element method. The die profile of hot extrusion is represented by Bezier-curve to define all available profile. In order to obtain the optimal die profile which yields uniform microstructure in the product the FPS(Flexible Polyhedron Search) method is applied to the present study. To validate the result of present study the experimental hot extrusion is performed and the result is compared with that of simulation.