• Journal of computational fluids engineering
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• v.1 no.1
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• pp.88-97
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• 1996

This paper treats an adaptive finite-element method for the viscous compressible flow governed by Navier-Stokes equations in two dimensions. The numerical algorithm is the two-step Taylor-Galerkin mettled using unstructured triangular grids. To increase accuracy and stability, combined moving node method and grid refinement method have been used for grid adaption. Validation of the present algorithm has been made by comparing the present computational results with the existing experimental data and other numerical solutions. Four benchmark problems are solved for demonstration of the present numerical approach. They include a subsonic flow over a flat plate, the Carter flat plate problem, a laminar shock-boundary layer interaction. and finally a laminar flow around NACA0012 airfoil at zero angle of attack and free stream Mach number of 0.85. The results indicates that the present adaptive triangular grid method is accurate and useful for laminar viscous flow calculations.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.81-93
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• 1993

The three dimensional(3D) shape reconstruction from two dimensional(2D) cross-sections can be completed through three main phases : the input compilation, the triangular grid formation, and the smooth surface construction. In the input compilation phase, the cross-sections are analyzed to exctract the input data required for the shape reconstruction. This data includes the number of polygonized contours per cross-section and the vertices defining each polygonized contour. In the triangular grid formation phase, a triangular grid, leading to a polyhedral approximations, is constructed by extracting all the information concerning contour links between two adjacent cross- sections and then performing the appropriate triangulation procedure for each contour link. In the smooth surface construction phase, a smooth composite surface interpolating all vertices on the triangular grid is constructed. Both the smooth surface and the polyhedral approximation can be used as reconstructed models of the object. This paper proposes a new method for reconstructing the geometric model of a 3D objdect from a sequence of planar contours representing 2D cross-sections of the objdect. The method includes the triangular grid formation algorithms for contour closing, one-to-one branching, and one-to-many braanching, and many-to-many branching. The shape reconstruction method has been implemented on a SUN workstation in C.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.103-107
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• 2007

Computational Fluid Dynamics (CFD in short) approach is now playing an important role in the engineering process recently. Generating proper grid system for the region of interest in time is prerequisite for the efficient numerical calculation of flow physics using CFD approach. Grid generation is, however, usually considered as a major obstacle for a routine and successful application of numerical approaches in the engineering process. CFD approach based on the unstructured grid system is gaining popularity due to its simplicity and efficiency for generating grid system compared to the structured grid approaches. In this paper an automated triangular surface grid generation using CAD surface data is proposed According to the present method, the CAD surface data imported in the STL format is processed to identify feature edges defining the topology and geometry of the surface shape first. When the feature edges are identified, node points along the edges are distributed. The initial fronts which connect those feature edge nodes are constructed and then they are advanced along the CAD surface data inward until the surface is fully covered by triangular surface grid cells using Advancing Front Method. It is found that this approach can be implemented in an automated way successfully saving man-hours and reducing human-errors in generating triangular surface grid system.

• Korean Journal of Computational Design and Engineering
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• v.9 no.1
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• pp.1-10
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• 2004

In the process of finite element analysis, mesh generation is tedious job which consumes tremendous time. Therefore, the automation of well shaped mesh generation from the minimal boundary input data is desirable to improve reliability and accuracy of the analysis and also to reduce the process time of the entire design process. The automation of triangular mesh generation has been relatively well treated due to its robustness and ease of handling when compared to rectangular element mesh generation. In this study, the offset method developed previously for generating plane rectangular element mesh has been corrected and modified to generate triangular element mesh on the B-spline surface having arbitrary holes. The result shows that the generated triangular mesh has the average aspect ratio over 0.9. The designed arbitrary surface shape has been interactively constructed by non-uniform B-spline theory for triangular mesh generation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.9
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• pp.538-545
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• 2000

In this paper we proposed a new map construction and path planning method for mobile robot. In our proposed method first we introduced triangular representation map that mobile robot can navigate through shorter path and flexible motion instead of grid representation map for mobile robot navigation. method in which robot can navigate complete space through as short path as possible in unknown environment is proposed. Finally we proposed new path planning method in a quadtree representation map. To evaluate the performance of our proposed new path planning method in a quadtree representation map. To evaluate the performance of our proposed triangular representation map it was compared with the existing distance transform path planning method. And we considered complete coverage navigation and new path planning method through several examples.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1783-1788
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• 1994

A comparison of the temperature distributions along the wall and center of the fin and the heat loss from the fin, computed assuming the fin tip is insulated and assuming it is not insulated in a triangular fin, is performed by the two-dimensional forced analytic method. When the fin tip is not insulated, a comparison between forced analytic method and analytic method is made in the heat loss and temperature along the fin wall. The value of Biot number varies from 0.01 to 1.0. The root temperature and surrounding convection coefficients of the fin are assumed as a constant. The results are (1) the analysis on the triangular fin assuming the fin tip is insulated does not produce a good value as compared to that of not-insulated case as the non-dimensional fin length decreases and as the value of Biot number increases and (2) the errors between forced analytic method and analytic method are very small, but the former method is better for computer running time and accuracy.

• Archives of Plastic Surgery
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• v.37 no.5
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• pp.639-643
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• 2010

Purpose: Cryptotia is a congenital deformity in which the upper third of the auricle is buried under the temporal skin. It is rare in Caucasians, yet it is more common in Asians. Although a variety of methods to treat cryptotia have been introduced, there is still no acceptable single procedure that can successfully manage this deformity in its entity. We present a triangular V-Y advancement flap and rhomboid flap for correcting cryptotia that can overcome the diverse shortcomings of the conventional methods. Methods: This operative method was used to correct 18 auricles in patients ranging in age from 4 to 33 years. A triangular flap was prepared over the auricle by making a skin incision according to Ohmori's method. Then a rhomboid flap with a side length of about 8 to 10 mm that sets the lower portion as a pedicle in the anterior region was prepared to supplement the contracted portion of the helix. The cartilage deformity was corrected by the banner flap or the radiating cartilage incisions with cartilage graft or high density polyethylene graft. Results: We have treated 16 patients with severe cryptotia using this method and have obtained good aesthetic results. All cases showed widened scaphoid fossa and smooth triangular fossa of antihelix. There were no major postoperative complications, such as necrosis or infection of the flaps. Conclusion: Correction of cryptotia using the triangular V-Y advancement flap and rhomboid flap is useful a method for certain conditions, when a severe contraction of the helix is present.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.133-140
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• 2009

Presented in this paper is a method to generate round-endmill toolpaths for sculptured surfaces represented as a triangular mesh model. The proposed method is applicable in toolpath generation for ball-endmills and flat-endmills because the round-endmill is a generalized tool in three-axis NC (numerical control) milling. The method uses a wireframe model as the offset model that represents a cutter location surface. Since wireframe models are relatively simple and fast to calculate, the proposed method can process large models and keep high precision. Intersection points with the wireframe offset model and a tool guide plane are calculated, and intersection curves are constructed by tracing the intersection points. The final step of the method is extracting regular curves from the intersection curves including degenerate and self-intersected segments. The proposed method is implemented and tested, and a practical example is presented.

• Journal of Biosystems Engineering
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• v.13 no.4
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• pp.9-19
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• 1988

The threshing of head-feed combine may be accomplished mainly by the action of impact between threshing teeth and rice. In this study, it was attempted to assess threshing performance characteristics of head-feed threshing teeth. And the characteristics of threshing teeth will be applied to the method which could analyze the time and order of impact between teeth and the rice, which was used as a basis for predicting the threshing performance and determining the optimum design parameters. The results of the study are summarized as follows: 1. About 50% of threshed material were threshed by the beginning 7 impacts on the rice bundle. Threshing torque decreased until 25 impacts and did not change thereafter. 2. There was significant difference in the threshability according to the shape of threshing teeth. The triangular-shaped tooth was the most efficient in threshability ratio and the semicircle-shaped tooth was the lowest. There was no significant difference in specific energy requirement for the varied teeth design. Torn-head ratio being generated by the semicircle-shaped and the triangular-shaped teeth in series was less than that by a single tooth with the triangular-shaped and the double setting of the triangular-shaped. Chaff generation ratio by the triangular-shaped and the semicircle-shaped teeth was less than the others tried. 3. The triangular-shaped teeth in series, which was newly designed for this study, showed an intermediate characteristics between the double setting of the triangular-shaped and the semicircle- shaped teeth. Threshability ratio of the triangular-shaped teeth in series was higher than that of the semicircle and lower than the double setting of the triangular-shaped tooth. Torn-head generation ratio for it was about same as that of the semicircle. Chaff being generated by the triangular-shaped teeth in series was about same as the double setting of the triangular-shaped teeth. 4. About 40% of threshed grains which passed through concave were concentrated under the threshing tooth and the rest of grains displayed a skew distribution toward the inlet of threshing chamber.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.46-55
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• 1996

As industrial standard data, the STL format which approximates three dimensional CAD model to triangular facets, is used for RP(Rapid Prototyping) system in recent days. Because most RP system take the only form of two dimensional line segments as an input stream inspite of its imperfectness while converting into STL format, a CAD model is converted into a standard industrial format which is composed of many triangular facets. The error verifying process is composed of four main steps, and these are 1) Remove facets with two or more vertices equal to each other. 2) Fix overlapping error such as more than three facets adjacent to anedge. 3) Fill holes in the mesh by using Delaunay triangulation method. 4) Correct the wrong direction and normal vectors. This paper is concerned with serching the mentioned errors in advance and modifying them.