• Korean Journal of Computational Design and Engineering
• /
• v.4 no.3
• /
• pp.190-199
• /
• 1999

Presented in this paper is an algorithm for finding all intersections among polygonal chains with an O((n+k)·log m) worst-case time complexity, where n is the number of lien segments in the polygonal chains, k is the number of intersections, and m is the number of monotone chains. The proposed algorithm is based on the sweep line algorithm. Unlike the previous polygonal-chain intersection algorithms that are designed to handle special only cases, such as convex polygons or C-oriented polygons, the proposed algorithm can handle arbitrarily shaped polygonal chains having self-intersections and singularities (tangential contact, multiple intersections). The algorithms has been implemented and applied to 1) testing simplicity of a polygon, 2) finding intersections among polygons and 3) offsetting planar point-sequence curves.

• 제어로봇시스템학회:학술대회논문집
• /
• 1991.10b
• /
• pp.1601-1606
• /
• 1991

We present an algorithm to approximate the Voronoi diagrams of 2D objects bounded by algebraic curves. Since the bisector curve for two algebraic curves of degree d can have a very high algebraic degree of 2 * d$^{4}$, it is very difficult to compute the exact algebraic curve equation of Voronoi edge. Thus, we suggest a simple polygonal approximation method. We first approximate each object by a simple polygon and compute a simplified polygonal Voronoi diagram for the approximating polygons. Finally, we approximate each monotone polygonal chain of Voronoi edges with Bezier cubic curve segments using least-square curve fitting.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.25 no.1
• /
• pp.56-62
• /
• 1988

For shape description, a fast sequential method for polygonal approximation of chaincoded plane curves which are object boundaries is proposed. The proposed method performs polygonal approximation by use of the distance error from one point to a line, and its performance is enhanced by the smoothed slopes of lines. Furthermore, accumulated distance error and variable distance error threshold are proposed in order to consider and implement the visual characteristics of the human being.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 1996.06b
• /
• pp.61-66
• /
• 1996

In this paper, an efficient contour coding algorithm incorporating polygonal approximation and discrete sine transform is introduced. Contour information is inevitable in content based coding, and polygonal approximation method is widely used to compress the contour information. However polygonal approximation method is not suitable when fine contour is needed. We show that the error signal of polygonal approximation can be efficiently represented using DST, that is, the contour information can be represented accurately with polygons and DST coefficients. With this contour coding scheme, the required bits to represent a contour can be reduced by about 40-50% with virtually no degradation compared to the existing chain coding method.

• International Journal of CAD/CAM
• /
• v.2 no.1
• /
• pp.23-28
• /
• 2002

This paper presents an efficient line-offset algorithm for general polygonal shapes with islands. A developed sweep-line algorithm (SL) is introduced to find all self-intersection points accurately and quickly. The previous work is limited to handle polygons that having no line-segments in parallel to sweep-line directions. The proposed algorithm has been implemented in Visual C++ and applied to offset point sequence curves, which contain several islands.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.25 no.2
• /
• pp.133-139
• /
• 2017

The timing chain system, which is a typical power transmission technology applied to a vehicle, has been widely used by the automotive industry because it is normally designed to last a car's lifetime. However, the timing chain system may cause some problems due to the shape of the chains and the polygonal behavior on contact between the chain and the sprocket. In addition, noise and vibration caused by transmission error are the most typical problems encountered by major automotive manufacturers and they are considered as the main source of customer complaint. The initial tension of the chain-sprocket system is thought to be the main cause of transmission error, and it is regarded as the source of engine vibration and noise. The initial tension of the chain system should be controlled carefully since a low initial tension can cause twisting, which may lead to a system malfunction, while a high initial tension can reduce the service life due to a worn down contact surface. In this paper, the kinematic analysis model is generated with various initial tensions, which are controlled by changing the shape of the fixed guide with the largest contact surface with chain. The results showed that the transmission error was minimized on a particular range of initial tension, and the tendency showed that the error changed with a higher sensitivity at a lower initial tension.

• International Journal of Precision Engineering and Manufacturing
• /
• v.3 no.4
• /
• pp.15-23
• /
• 2002

With the development of a laser scanner of high precision and increased speed, reverse engineering becomes a key approach to reduce the time for the development of new products. But the modeling process is not so automated enough until now. Modeling in real workshops is usually performed by the experienced operators and it requires a skillful technique to get the resultant surface of high quality and precision. In this paper, a systematic solution is proposed to automate the free-form surface generation from the measured point data. Compatibility is imposed to the measured point data during input curve generation. And the compatibility of cross-sectional curve is also considered for the loft surface generation. The data in each step is produced in IGES file format to make an easy interface to other CAD/CAM software without any further data manipulation.

• Journal of Veterinary Clinics
• /
• v.24 no.4
• /
• pp.644-646
• /
• 2007

This report deals with a 9-year-old neutered male Yorkshire terrier that had been suffered from vomiting, bloody diarrhea, anorexia. On exploratory laparotomy, pale-pink $10{\times}6cm$ duodenal mass was found and submitted to the Department of Veterinary Pathology, College of Veterinary Medicine, Seoul National University. Histologically, the duodenal mass consisted of compact sheet of poorly demarcated, highly infiltrative neoplasm. The neoplastic cells were round to polygonal and contained scant to moderate amounts of granular basophilic cytoplasm and eccentrically located irregularly round nuclei with stippled chromatins. The neoplastic cells were positive to lamda light chain immunohistochemically but were uniformly negative for toluidine blue stain and giemsa stains. Based on these results, this case was diagnosed as primary extramedullary plasma cell tumor of duodenum.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.10
• /
• pp.168-177
• /
• 2001

Reverse engineering has been widely used for the shape reconstruction of an object without CAD data and the measurement of clay or wood models fur the development of new products. To generate a surface from measured points by a laser scanner, typical steps include the scanning of a clay or wood model, the generation of compatible input curves, the generation of a surface and manufacturing data like G code or STL file. A laser scanner has a great potential to get geometrical data of a model for its frost measuring speed and higher precision. The data from a laser scanner are composed of many line stripes of points including small spikes and noise. A new approach using automated surface generating algorithm is introduced to deal with problems during reverse engineering process. And the input data and the generated surface are represented in IGES format, thus can be supplied to other CAD/CAM software without any data manipulation.

• Archives of Plastic Surgery
• /
• v.39 no.6
• /
• pp.593-599
• /
• 2012

Background This study aimed to investigate the possibility of isolating mesenchymal stem cells (MSCs) from human thigh adipose tissue and the ability of human thigh adipose stem cells (HTASCs) to differentiate into hepatocytes. Methods The adipose-derived stem cells (ADSCs) were isolated from thigh adipose tissue. Growth factors, cytokines, and hormones were added to the collagen coated dishes to induce the undifferentiated HTASCs to differentiate into hepatocyte-like cells. To confirm the experimental results, the expression of hepatocyte-specific markers on undifferentiated and differentiated HTASCs was analyzed using reverse transcription polymerase chain reaction and immunocytochemical staining. Differentiation efficiency was evaluated using functional tests such as periodic acid schiff (PAS) staining and detection of the albumin secretion level using enzyme-linked immunosorbent assay (ELISA). Results The majority of the undifferentiated HTASCs were changed into a more polygonal shape showing tight interactions between the cells. The differentiated HTASCs up-regulated mRNA of hepatocyte markers. Immunocytochemical analysis showed that they were intensely stained with anti-albumin antibody compared with undifferentiated HTASCs. PAS staining showed that HTASCs submitted to the hepatocyte differentiation protocol were able to more specifically store glycogen than undifferentiated HTASCs, displaying a purple color in the cytoplasm of the differentiated HTASCs. ELISA analyses showed that differentiated HTASCs could secrete albumin, which is one of the hepatocyte markers. Conclusions MSCs were islolated from human thigh adipose tissue differentiate to heapatocytes. The source of ADSCs is not only abundant abdominal adipose tissue, but also thigh adipose tissue for cell therapy in liver regeneration and tissue regeneration.