• 한국생산제조학회지
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• 제19권4호
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• pp.562-569
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• 2010

This paper analyzes the problems that occurred in the magnification process for a fine input image and investigates a method to improve the blurring of magnified image. This paper applies a curve interpolation algorithm in CAD/CAM for the same test images with the existing image algorithm in order to improve the blurring of magnified image. As a result, the nearest neighbor interpolation, which is the most frequently applied algorithm for the existing image interpolation algorithm, shows that the identification of a magnified image is not possible. Therefore, this study examines an interpolation of gray-level data by applying a low-pass spatial filter and verifies that a bilinear interpolation presents a lack of property that accentuates the boundary of the image where the image is largely changed. The periodic B-spline interpolation algorithm used for curve interpolation in CAD/CAM can remove the blurring but shows a problem of obscuration, and the Ferguson' curve interpolation algorithm shows a more sharpened image than that of the periodic B-spline algorithm. For the future study, hereafter, this study will develop an interpolation algorithm that has an excellent improvement for the boundary of the image and continuous and flexible property by using the NURBS, Ferguson' complex surface, and Bezier surface used in CAD/CAM engineering based on the results of this study.

• 대한조선학회논문집
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• 제35권2호
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• pp.51-62
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• 1998

본 연구에서는 공동수조(Cavitation Tunnel) 실험용 모형프로펠러의 5축 가공을 위해 Windows NT와 PC 환경하에서 작동하는 CAD/CAM 시스템을 개발하였다. 본 시스템은 그 성격에 따라 크게 4가지의 모듈로 구성되어 있다. 먼저, 프로펠러 설계를 위해 기존에 사용하고 있던 텍스트 위주의 S/W(Text based S/W)를 그래픽화 하여 통합함으로써 설계의 효율을 향상시켰다. 설계의 결과로 출력되는 점 데이터는 NURBS(Non-Uniform Rational B-Spline) 방법을 이용하여 복합곡면 (Composite Surface)으로 모델링하였고 가공은 황삭, 중삭, 정삭 및 잔삭으로 수행하였다. 각각의 경우에 있어서 공구와 공작물의 충돌 및 간섭을 체크하여 공구경로를 산출하였으며 그것을 역기 구학 해석하여 NC 데이터로 변환하였다. 또한, 가공의 상태를 화면상에서 검증하기위해 공구 및 공작물을 그래픽화하여 NC 데이터를 검증할 수 있도록 하였다. 끝으로 5축 가공의 가공 효율을 최대화하기 본 연구에서는 공동수조 실험용 모형프로펠러의 5축 가공을 위해 Windows NT와 PC 환경하위해 실험을 통하여 최적의 절삭조건을 선정하고 이를 시스템내에 데이터베이스화 함으로써 설계부터 가공까지를 자동으로 수행할 수 있는 시스템으로 구축하였다.

• 대한조선학회논문집
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• 제43권5호
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• pp.550-559
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• 2006

A design procedure for a ship with minimum total resistance was developed using a numerical optimization method called SQP(Sequential Quadratic Programming) and a CFD technique based on the Rankine source panel method with the nonlinear free surface boundary conditions. During the whole optimization process the geometry of the hull shape was represented based on the NURBS(Non-uniform rational B-spline) technique and the modification of the hull shape was controlled using the Bell-shaped distribution function to keep the fairness of the hull shape before and after the hull modification. The numerical analysis was carried out using 4000TEU container ship in the towing tank facility installed in the Pusan national university to know the validity of the developed algorithm for this study. As the results of the numerical analysis it proved that the resistance of the optimized hull is conspicuously reduced in comparison with the original hull in a wave-making resistance point of view.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권3호
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• pp.292-304
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• 2017

High-speed vessels are prone to the surf-riding in adverse quartering seas. The possibility of mitigating the surf-riding of the ITTC A2 fishing vessel in the design stage is investigated using the 6-DOF weakly non-linear model developed for surf-riding simulations in quartering seas. The longitudinal position of the ship's center of buoyancy (LCB) is chosen as the design parameter. The adjusting of LCB is achieved by changing frame area curves, and hull surfaces are reconstructed accordingly using the Radial Basis Function (RBF). Surf-riding motions in regular following seas for cases with different LCBs and Froude numbers are simulated using the numerical model. Results show that the surf-riding cannot be prevented by the adjusting of LCB. However, it occurs with a higher threshold speed when ship's center of buoyancy (COB) is moved towards stem compared to moving towards stern, which is mainly due to the differences on wave resistance caused by the adjusting of LCB.

• 한국해양공학회지
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• 제20권4호
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• pp.24-30
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• 2006

Different methods exist for the estimation of thermaldeformation of plates in the line heating process. These are based on the assumption of residual strains in the heat-affected zone, known as the method of inherent strains, or simulated relations between heating conditions and residual deformations. The purpose of this paper is to develop a simulator of thermal deformation in the line heating, using the artificial neural network. Curvature deformations for the plate-forming are investigated, which can be used as a prime deformation parameter in the process. The curvature of plates are calculated using the approximation of plate surface by NURBS. Line heating experiments for 11 specimens of different thickness and heating conditions were performed. Two neural networks predicting the maximum temperature and curvature deformations at the heating line are studied. It was concluded that the thermal deformations predicted by the neural network can be used in a line heating simulator, which is considered an attractive and practical alternative to the existing methods.

• 한국실내디자인학회논문집
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• 제17권3호
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• pp.148-155
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• 2008

The following research focuses on the formation method of digital space by organistic line extension among various digital formation methods. The paper reflects on the meaning and concept of today's digitalism which enables the application of complex organistic system on space through advanced technology. It also explores the concept of a line in topology which differs in assumptive meaning from traditional Euclidian geometry. The findings of the research are that first, digital space is not optimized, but is a tentative formation in process. A digital space encompasses characteristics such as infinity, possibility, potential, asymmetry, and the force of virtuality such characteristics are expressed through a moving surface constantly changing with direction. Second, a digital space formed by line extension is inseparable and durable since no measurement or dimension is predetermined. Furthermore, its sense of direction and flexibility gives it a feeling of a living organism. Third, a Euclidian methodology called 'NURBS' is being developed to express such a dynamic digital space; this is reflected through three elements, control point, weights, and knots to effectively reflect the characteristics of virtuality. The opportunities of digital space are infinite, and the possibilities of formation methods likewise vast.

• Advances in Computational Design
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• 제6권1호
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• pp.15-30
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• 2021

With improvement in innovative manufacturing technologies, it became possible to fabricate any complex shaped structural design for practical applications. This allows for the fabrication of curvilinearly stiffened pressure vessels and pipes. Compared to straight stiffeners, curvilinear stiffeners have shown to have better structural performance and weight savings under certain loading conditions. In this paper, an optimization framework for designing curvilinearly stiffened composite pressure vessels and pipes is presented. NURBS are utilized to define curvilinear stiffeners over the surface of the pipe. An integrated tool using Python, Rhinoceros 3D, MSC.PATRAN and MSC.NASTRAN is implemented for performing the optimization. Rhinoceros 3D is used for creating the geometry, which later is exported to MSC.PATRAN for finite element model generation. Finally, MSC.NASTRAN is used for structural analysis. A Bi-Level Programming (BLP) optimization technique, consisting of Particle Swarm Optimization (PSO) and Gradient-Based Optimization (GBO), is used to find optimal locations of stiffeners, geometric dimensions for stiffener cross-sections and layer thickness for the composite skin. A cylindrical pipe stiffened by orthogonal and curvilinear stiffeners under torsional and bending load cases is studied. It is seen that curvilinear stiffeners can lead to a potential 10.8% weight saving in the structure as compared to the case of using straight stiffeners.

• 한국항공우주학회지
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• 제36권9호
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• pp.825-834
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• 2008

고 받음각에서의 방향 안정성 향상을 위한 chine 형상 최적화를 수행하였다. Super ellipse equation을 통하여 다양한 형태의 chine 형상을 생성하고, 3차원 Navier-Stokes 방정식을 이용하여 방향안정성 및 고받음각에서의 공력 특성을 분석하였으며, 가장 높은 방향 안정성을 갖는 형상을 기본형상으로 선정하였다. 파리미터를 이용한 기본형상의 곡면 변형을 통하여 높은 방향 안정성 및 양항비를 동시에 만족하는 최적형상 도출을 위하여, 반응면을 구성하고 가중치를 도입하고 양항비를 구속조건으로 하는 방향안정성 최적화 문제를 수행하였다. 본 연구를 통하여 고받음각에서 chine형상의 공력특성을 파악하여 강한 와류를 발생시키는 chine 형상이 방향안정성에 도움이 된다는 것을 확인할 수 있었으며 최적화를 통해 기본형상보다 방향안정성이 약 29% 향상되는 결과를 얻었다. 또한 파라미터 기반 형상 생성기법과 근사최적화 기법의 연동을 이용한 형상최적설계 과정을 초음속, 고받음각 유동의 chine 형상설계에 적용하여 그 효율성을 확인하였다.

• 한국콘텐츠학회논문지
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• 제5권4호
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• pp.133-140
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• 2005

문화기순(CT)은 좁은 의미로 문화콘텐츠를 만들어내는 데 기본이 되는 기술로 각 국은 세계적 문화 공감대를 형성할 수 있는 콘텐츠를 창출하기 위한 노력을 기울이고 있다. 우리 고유의 문화유산을 응용하는 다양한 콘텐츠가 생성될 때 창의적이고 세계적인 경쟁력을 갖추게 되며, 이를 위해 문화원형 복원기술은 필수적인 핵심 기술이다. 본 논문에서는 찬란한 문화유산을 가진 백제시대 유물인 금동용봉환두대도를 3차원 형상정보 처리기술과 고고학적, 과학적 분석 자료를 토대로 디지털의 원형복원한다. 먼저, 3차원 스캐닝 작업을 통해 취득된 데이터는 샘플링과 특징추출 및 정합과정 후 홀 채움 및 스무딩을 이용하여 보정하고, NURBS와 B-Spline 방법을 이용하여 곡면으로 모델링한다. 그런 다음, 환두대도 구성요소의 색상과 재질을 추정하여 텍스쳐를 편집한 후 맵핑한다. 제작되어진 원형 모델은 전문가의 검증을 거쳐 수정 보완되었다. 디지털 복원된 환두대도는 IT기술과 결합하여 디지털 박물관 구축 및 시대별 지역별, 유형별 환두대도의 정형화 된 데이터베이스를 구축하여 손실 유물의 원형 추정에 활용할 수 있다. 또한 고고학이나 보존과학의 교육 컨텐츠 및 영화, 방송, 게임, 애니메이션 등의 문화 콘텐츠로 활용할 수 있다.