• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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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.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.3
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• pp.265-275
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• 2015

This paper describes extraction methods of five different types of geometrical features (line, arc, corner, polynomial curve, NURBS curve) from the obtained raw data by using a two-dimensional laser range finder (LRF). Natural features with their covariance matrices play a key role in the realization of feature-based simultaneous localization and mapping (SLAM), which can be used to represent the environment and correct the pose of mobile robot. The covariance matrices of these geometrical features are derived in detail based on the raw sensor data and the uncertainty of LRF. Several comparison are made and discussed to highlight the advantages and drawbacks of each type of geometrical feature. Finally, the extracted features from raw sensor data obtained by using a LRF in an indoor environment are used to validate the proposed extraction methods.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.77-85
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• 2012

The membrane structure maintains stable form by giving initial tension to ductile membrane and increasing the stiffness of exterior that is much adopted in the large span spatial structure by making its thickness thin. This kind of membrane structure has characteristic that can express free-form curve, so the selection of structural form is very important. So, this paper proposes the expression of free-form surface based on NURBS basis function and the finite element method considering geometrical nonlinearity for the deduction of large deformation result. Also, for minimizing the approximation of the surface that is derived from the form-finding result, the interface method that change finite element mesh to NURBS is proposed. So, the optimum surface of free-form membrane is derived.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.474-479
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• 2006

컴퓨터 기술이 발전함에 따라 3 차원 입력시스템을 통한 모델링이 가능하게 되었다. 2 차원 시스템은 평면 입력을 공간상의 데이터로 바꾸기 위한 많은 기능과 메뉴들이 존재하지만 3 차원 시스템에서는 그러한 복잡한 기능 없이 입력 데이터가 곧바로 모델링에 적용될 수 있다. 하지만 아직까지 3 차원 입력시스템에서 모델링을 수행하는 디자이너에게 익숙한 스케치 방법을 고려하지 못하고 있는 실정이다. 디자이너에게 가장 익숙한 모델링 방법은 스케치북에 선으로 그림을 그리는 것이기 때문에, 모델을 변형하는 방법은 이를 벗어나지 않도록 해야 한다. 평면 스케치에서 디자이너가 그리는 선은 모델의 윤곽을 잡아주고 모델의 특징이 되는 부분을 표현하게 된다. 이러한 선의 입력을 통한 스케치를 3 차원 모델링에서 그대로 사용하기 위해서는 공간에서의 점이나 면이 아닌 선의 입력을 모델링에 적용할 수 있어야 한다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.5
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• pp.55-61
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• 2005

In this paper, we propose the visual simulation system for virtual reality motion rider system. The visual simulation system can apply verity virtual reality system. This paper deals with programs on 3D automatic creation of terrain, road design, and a realtime rendering program for the virtual reality system. For the 3D automatic creation of terrain, DEM data and rectangular grid method are applied. We can make two different road object with the road design program. One of them includes road definition, and the other is obtained by using 'NURBS curve.' Visual simulation is consisted by additional modeling and real-time rendering. We can apply the programs made in this way to visual system of driving simulator.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.10
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• pp.148-155
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• 1998

For products of various shapes, compound surfaces are used. Blending surfaces are essential to the products of the compound surfaces. In this paper a method of making shape of blending surface flexible with parameter control is discussed. The parameter has quantitative control of shape of the blend. The blending surface is applied to NURBS and simple primitives in solid model. Intersection curves of surfaces is used to provide the blend with generality. Rail curve are found with the intersection curves. The blend is generated by rail curves and parameter control. Also, In strict constraint condition, blending surface with flexible shapes is discussed, keeping ;${GC}^1$ and ;${GC}^2$ continuity between free-formed surfaces and solids. Joining blending ,bridge blending and blending surface at corner are generated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.213-217
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• 2008

This paper describes an application of centrifugal compressor optimization system, in which the blade profile of impeller is represented with NURBS(Non-Uniform Rational B-Spline) curve. A commercial CFD(Computational Fluid Dynamics) program named NUMECA fine/turbo was used to evaluate the performance of the whole centrifugal compressor flow passage including impeller and diffuser. The whole optimization design system was integrated based on iSIGHT, a commercial integration and optimization software, which provides a direct application of some optimization algorithms. To insure the practicability of optimization, the performance of centrifugal compressor under all condition was concerned during the optimizing process. That means a compositive object function considering the aerodynamic efficiency, pressure ratio and mass flow rate under different work condition was applied by using different weight number for different conditions. Using the optimization method described in this paper, an optimized design of the impeller blade of centrifugal compressor was obtained. Comparing to the original design, optimized design has a better performance not only under the design work condition, but also the off-design work condition including near stall and near choke condition.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.116-128
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• 2020

In the shipbuilding industry, three-dimensional (3D) templates play a key role in the completeness evaluation of shell plates with a large curvature in the shell-plate fabrication process. Currently, the information of 3D templates from a ship computer-aided design system is limited; thus, manufacturers depend on their experience to produce the templates manually. This results in the inaccuracy of templates in addition to increased production time. Therefore, if the pieces of the 3D templates can be produced automatically with accurate information, the lead time of the fabrication process can be reduced. In this study, we define a new type of template piece and develop methods for extending a boundary template and converting manufacturing information into numerical control machine input. In addition, based on the results of the study, we propose a production automation system for 3D template pieces. This system is expected to reduce the lead time of the fabrication process.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.5
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• pp.387-392
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• 2017

There is a constant demand for hull variation related to ship design. Various input variables are generally given to achieve the objective functions assigned by each variation process. When dealing with geometric shapes accompanied by nonlinear operations during the variation process, vague relationships or uncertainties among input variables are commonly observed. Therefore, it is strongly recommended to identify those uncertainty factors in advance. A method to modify the shape of a closed hull form with a new area and a centroid had been introduced as a new process of hull variation. Since uncertainty between input variables still existed in the method, however, it was not easy for the user to enter the area and the corresponding centroid. To overcome this problem, a method is presented in this paper to provide the feasible region of centroids for a given area. By utilizing the concept and techniques used in the statistics such as the number of samples, probability, margin error, and level of confidence, this method generates the distribution of possible centroids along the regression curve. The result shows that the method helps the user to choose an appropriate input value following his or her design intention.

• Journal of the Korean Society of Costume
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• v.54 no.4
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• pp.63-74
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• 2004

This study shows that clothes to be just the same as the real thing can be Produced through the third dimension computer graphics, and then presents that not only the area of fashion design can be expanded in the virtual reality field by doing the simulation of the fashion show, but also the information can be made the real time public ownership and the communication can be fulfilled smoothly. In this study, analyzing the third dimension computer graphic programs to be used much at present, Alias Wavefront Company's Maya software which was the most effective in the clothes simulation and the clothes CAD SGS OptiTex 8.7 which went well substitutive for it were used of them. The conclusions of this study that got through the work manufacture are as follows： The first, if the file manufacturing in the clothes CAD by using the computer was stored, the pattern used 3D simulation was available because it could be summoned in 3D software. The second, if the data of DXF form in Maya program was summoned, they could not be applied by Maya Cloth supported in Nurbs only because they were recognized as the DXF＿layer. So the curve along the outer lines of the pattern was drawn and Maya Cloth was applied to be possible to get the natural silhouette of clothes. The third, when the clothes were manufactured by 3D, if the draping character was applied according to the textile special quality, not only the control of textile's thickness, weight, quality feeling, and silhouette was available, but also the clothes were available to graft the special textile materials. The fourth, the natural motion of model was produced by capturing the actual model's walking action In order to produce the fashion show motion and also the dynamic fashion show was available by the angle of camera, the establishment of lighting, and etc. in the final rendering. The clothes manufactured by 3D are available to change the design by changing the materials, or by adding the details, or by utilizing the special materials on clothes. Therefore, the trial and error following at the clothes manufacture can be reduced. But the elevation of the rendering speed, the price down, the strengthening of personal security, and etc. are required.