• Journal of the Korean Society for Precision Engineering
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• v.3 no.4
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• pp.53-63
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• 1986

In this study, the stress distribution of rectangular bar under torsion, when warping of both ends is free or constrained, is investigated. Method of separation of variable and Fourier Series are used for the theoretical analysis, and 3dimensional photoelastic stress-freezing method for experimental analysis. The main results are as follows; 1) In the case of warping-constrained rectangular bar, the normal stresses are negligible because they are less then 0.5% of the shear stresses. The maximum normal stress is placed on the point of y=0.61 b when b/a=1 and it gradually moves to the corner y=b when the value of b/a is increased. 2) According to increase of the value of b/a, on the crossection, the maximum shear stress is placed on the middle point of the long side (x=${\pm}a$, y=0) when warping of both ends is free but the middle of the short side (x=0, y=${\pm} b$) when warping is constrained. The stress distribution is straight line when warping is constrained, namely, the stress distribution is proportional to the distance from the axis of centroid, but parabolic when warping is free. 3) The values of the combined stress of warping-constrained bar, if the influence of the loaded point is neglected, are generally smaller than those of warping-free.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.116-123
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• 2009

Feature point matching, which is finding the corresponding points from two images with different viewpoint, has been used in various vision-based applications and the demand for the real-time operation of the matching is increasing these days. This paper presents a real-time feature point matching method by using a local descriptor derived by Zernike moments. From an input image, we find a set of feature points by using an existing fast corner detection algorithm and compute a local descriptor derived by Zernike moments at each feature point. The local descriptor based on Zernike moments represents the properties of the image patch around the feature points efficiently and is robust to rotation and illumination changes. In order to speed up the computation of Zernike moments, we compute the Zernike basis functions with fixed size in advance and store them in lookup tables. The initial matching results are acquired by an Approximate Nearest Neighbor (ANN) method and false matchings are eliminated by a RANSAC algorithm. In the experiments we confirmed that the proposed method matches the feature points in images with various transformations in real-time and outperforms existing methods.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.7-14
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• 2017

The effect of high temperature-moisture on corrosion and mechanical properties for Sn-0.7Cu, Sn-3.0Ag-0.5Cu (SAC305) solders on flexible substrate was studied using Highly Accelerated Temperature/Humidity Stress Test (HAST) followed by three-point bending test. Both Sn-0.7Cu and SAC305 solders produced the internal $SnO_2$ oxides. Corrosion occurred between the solder and water film near flexible circuit board/copper component. For the SAC305 solder with Ag content, furthermore, octahedral corrosion products were formed near Ag3Sn. For the SAC305 and Sn-0.7Cu solders, the amount of internal oxide increased with the HAST time and the amount of internal oxides was mostly constant regardless of Ag content. The size of the internal oxide was larger for the Sn-0.7Cu solder. Despite of different size of the internal oxide, the fracture time during three-point bending test was not significantly changed. It was because the bending crack was always initiated from the three-point corner of the chip. However, the crack propagation depended on the oxides between the flexible circuit board and the Cu chip. The fracture time of the three-point bending test was dependent more on the crack initiation than on the crack propagation.

• Journal of the Korean Society of Costume
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• v.64 no.3
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• pp.77-92
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• 2014

The purpose of this research is to examine the expression methods of Haute Couture designers' high value-added jacket designs, In order to achieve this, the positions and sizes of the design component items of tailored jackets designed by Haute Couture designers from the 1940s to the 1970s were analyzed. The results of the analysis are as follows. First, the silhouette changed while leading the contemporaneous fashions, and such changes could be confirmed by the width and length of the jacket's shoulder, chest, waist, and hem that determine the silhouette. Particularly, the length of the chest changed which signifies that the depth of the armhole was playing an important role in the production of high value-added jackets in relation to the sleeves and the fit of jackets. Second, the position and the size of the dart are the components that can express the fit of a jacket and the designer's creativity, The starting point position of the dart and the position passing by waist, and the position of the end of the dart were placed in the position beyond B.P. depending on the designer's creativity and techniques, deriving the changes of the silhouette and creating high value-added jackets. Third, the tailored collar, which was a three-dimensional component made up of the upper collar, gorge line, lapel, and break line, was an important component that could express high value-added jackets. Changes in the width and the height of the break line position of the sides of the neck were represented as changes in the neck size of the collar, and changes in the vertex locations of the upper collar corner-point, the gorge line (the corner-point of the lapel and V zone) were also represented as diverse tailored collar designs. And the differences in the width and the length of each component of the collar were related to each other and represented as changes in the slope and angle of the collar outline. Fourth, the changes in sleeve designs of the jacket were in such items as the width of the sleeve opening, the width of the sleeve hem, and the length of the sleeve, and were represented as diverse sleeve designs such as widened sleeve opening types, and straight line types.

• IEMEK Journal of Embedded Systems and Applications
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• v.9 no.5
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• pp.269-276
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• 2014

In recent, autonomous navigation techniques to avoid obstacles have been studied by using unmanned aircraft vehicles(UAVs) since the increment of UAV's interest and utilization. Particularly, autonomous navigation based UAVs are utilized in several areas such as military, police, media, and so on. However, there are still some problems to avoid obstacle when UVAs perform autonomous navigation. For instance, the UAV can not forward in the corner of corridors even though it utilizes the improved vanish point algorithm that makes an autonomous navigation system. Therefore, in this paper, we propose an obstacle avoidance technique based on immune algorithm for autonomous navigation of Quadrotor. The proposed algorithm is consisted of two steps such as 1) single color discrimination and 2) multiple color discrimination. According to the result of experiments, we can solve the previous problem of the improved vanish point algorithm and improve the performance of autonomous navigation of Quadrotor.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11
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• pp.3140-3149
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• 1999

Skew correction for document images can be using a rotational transformation of pixel coordinates. In this paper we propose a method which corrects the document skew, by an amount of $\theta$ degrees, using block information, where the block is defined as a rectangular area containing adjacent black pixels. Processing speed of the proposed method is faster than that of the method using pixel transformation, since the number of floating-point operations can be reduced significantly. In the proposed method, we rotate only the four corner points of each block, and then identify the pixels inside the block. Two methods for inside pixel identification are proposed; the first method finds two points intersecting the boundary of the rotated block in each row, and determines the pixels between the two intersection points as the inside pixel. The second method finds boundary points based on Bresenham's line drawing algorithm, using fixed-point operation, and fills the region surrounded by these boundaries as black pixels. We have measured the performance of the proposed method by experimenting it with 2,016 images of various English and Korean documents. We have also proven the superiority of our algorithm through performance comparison with respect to existing methods based on pixel transformation.

• Journal of IKEEE
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• v.22 no.2
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• pp.350-355
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• 2018

In this paper, a system that can classify the objects in the image according to their sizes using the reference points is proposed. The object is studied with samples. The proposed system recognizes and classifies objects by the size in images acquired using a mobile phone camera. Conventional object recognition systems classify objects using only object size. As the size of the object varies depending on the distance, such systems have the disadvantage that an error may occurs if the image is not acquired with a certain distance. In order to overcome the limitation of the conventional object recognition system, the object recognition system proposed in this paper can classify the object regardless of the distance with comparing the size of the reference point by placing it at the upper left corner of the image.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.547-552
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• 2003

In mold machining, there are many concave machining regions where chatter and tool deflection occur since MRR (material removal rate) increases as curvature increases even though cutting speed and depth of cut are constant. Boolean operation between stock and tool model is widely used to compute MRR in NC milling simulation. In finish cutting, the side step is reduced to about 0.3mm and tool path length is sometimes over 300m. so Boolean operation takes long computation time and includes much error if the resolution of stock and tool model is larger than the side step. In this paper, curvature of CL(cutter location) surface and side step of tool path is used to compute the feedrate for constant MRR machining. The data structure of CL surface is Z-map generated from NC tool path. The algorithm to get local curvature from discrete data was developed and applied to compute local curvature of CL surface. The side step of tool path was computed by point density map which includes cutter location point density at each grid element. The feedrate computed from curvature and side step is inserted to new tool path to regulate MRR. The resultants wire applied to feedrate optimization system which generates new tool path with feedrate from NC codes for finish cutting. The system was applied to speaker mold machining. The finishing time was reduced to 12.6%. tool wear was reduced from 2mm to 1.1mm and chatter marks and over cut on corner were removed.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.442-449
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• 2000

Before the complete construction of new high-speed line between Seoul and Pusan, KTX is going to operate on both new high-speed line between Seoul and Daegu and electrified conventional lines between Daegu and Pusan. Then, the wheels of KTX are going to operate on various rails such as KS50N and KS60 of conventional line as well as UIC60 of high-speed line. Also, conventional line will have a mixed traffic mode with various types of trains operating on it, such as Saemaul and Mugunghwa. Hence, this study reviews the wear phenomena of wheels and rails in geometrical point of view by comparing their profiles. The analyses of the results show that because UIC60 rail is designed for KTX, KS50N rail whose profile is similar to that of UIC60 will not have any impact on the shape of wheel wear. On the other hand, KS60 rail is expected to have partial wear on both the flange of KTX wheel and the gauge corner of the rail in the initial stages. However, the operation of the trains whose wheels have 1/20 conicity will cause partial sidewear on the inside of the rail and the movement of the contact point between KTX wheel and the rail toward the inside of the track. As a result, the flange wear of KTX wheel will be reduced and the formation of wear-equilibrium profile will be faster.

• The Transactions of the Korea Information Processing Society
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• v.7 no.3
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• pp.935-942
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• 2000

In this paper we introduce a fast simplification algorithm for terrain height fields to produce a triangulated irregular network, based on the greedy insertion algorithm in [1,4,5]. Our algorithm partitions a terrain height data into rectangular blocks with the same size ad simplifies blocks one by one with the greedy insertion algorithm. Our algorithm references only to the points and the triangles withing each current block for adding a point into the triangulation. Therefore, the algorithm runs faster than the greedy insertion algorithm, which references all input points and triangles in the terrain. Our experiment shows that partitioning method runs from 4 to more than 20 times faster, and it approximates test height fields as accurately as the greedy insertion algorithms. Most greedy insertion algorithms suffer from elongated triangles that usually appear near the boundaries. However, we insert the four corner points into each block to produce the base triangulation of the block before the point addition step begins so that elongated triangles could not appear in th simplified terrain.