• 한국정밀공학회지
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• 제22권2호
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• pp.133-138
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• 2005

The deformation of sheet metal due to the residual stress during blanking or piercing process, is numerically simulated by means of a commercial finite element code. Two dimensional plain strain problem is solved and then its result is applied to the deformation analysis of the lead frame. The plain strain element is applied to the 2D problem to observe the Von Mises equivalent stress concentration at the both shearing edges. As the punch penetrates into the sheet material, the stress concentration generated on both edges is getting increased to be the shearing surface. The limits of the punching depth applied to the simulation is 16% and 24% of the sheet thickness for the plain strain element and the hexahedral element, respectively. The hexahedral element and the limit of punching depth were applied to the deformation analysis of the lead frame for the blanking process. The FEM results for the lead deformation were very good agreement with the experimental ones. This paper shows that the coarse mesh has enabled to analyze the lead deformation generated due to the blanking mechanism. This simple approach to save the calculation time will be very effective to the design of the blanking tools in industries.

• 한국진공학회지
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• 제2권2호
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• pp.161-165
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• 1993

Si(100)와 Si(111) 표면에 에피 성장시킨 Ge의 기하학적, 전기적 구조가 scanning tunneling microscope로 연구되었다. Ge 원자는 scanning tunneling spectroscopy와 bias 전압을 달리한 STM 상에서 Si 원자와 구별되었다. 이것을 이용하여 Ge의 성장 형태를 연구하였다. (2${\times}$1) 재배열 구조를 가진 (100) 표면에서 Ge 성장층은 720K에서 B형의 step edge로부터 주로 성장하였다. (111) 표면에서도 주로 step edge에서 성장하였으며, Ge의 양과 annealing 온도에 따라 (5${\times}$5)와 (7${\times}$7)구조가 보였다.

• 한국정밀공학회지
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• 제18권2호
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• pp.199-205
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• 2001

Burr makes troubles on manufacturing process due to deburring cost, quality of products and productivity. This paper described the results of experimental study on the influence of the cutting parameters on the formation of exit burrs in face milling. Using the results of experimental study, burr types are classified and data bases are developed to predict burr formation result. From the CAD file for work geometry and the NC data for tool path, the exit angles are calculated at every edges. This program predicts the burr geometry at exit edges using the prediction algorithm and data bases which are developed experimentally. Simulation results on deformation strain and temperature are also available in specific 2-dimensional cutting conditions. Also algorithm which can determine the exit angle is proposed.

• Tribology and Lubricants
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• 제31권4호
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• pp.163-169
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• 2015

This paper describes a design method for the corner radius of a contacting body using the theoretical approach of contact mechanics. A complete contact, as in the case of a sharp-cornered punch, produces singular contact traction: whereas, in an incomplete contact, the singular contact traction disappears because of the rounded corners, and the contact edges are within the rounded regions. The design method aims to determine the conditions of the contact force as well as the material properties in an incomplete contact. The incomplete contact changes into the complete contact again when the contact edges exceed the rounded regions owing to either an increased contact force or the compliance of the materials. The contact length of a rounded punch is used as a parameter to derive the required conditions. As a result, a design formula is obtained, which provides a minimum allowable radius when the materials, normal contact force, and the length of a flat region of the punch are predetermined. This work consists of two parts: Part I includes a theoretical background, design method, and formula, and Part II describes the actual process with the investigation of design parameters.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제11권2호
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• pp.9-14
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• 2007

A signed 3-partite graph is a 3-partite graph in which each edge is assigned a positive or a negative sign. Let G(U, V, W) be a signed 3-partite graph with $U\;=\;\{u_1,\;u_2,\;{\cdots},\;u_p\},\;V\;=\;\{v_1,\;v_2,\;{\cdots},\;v_q\}\;and\;W\;=\;\{w_1,\;w_2,\;{\cdots},\;w_r\}$. Then, signed degree of $u_i(v_j\;and\;w_k)$ is $sdeg(u_i)\;=\;d_i\;=\;d^+_i\;-\;d^-_i,\;1\;{\leq}\;i\;{\leq}\;p\;(sdeg(v_j)\;=\;e_j\;=\;e^+_j\;-\;e^-_j,\;1\;{\leq}\;j\;{\leq}q$ and $sdeg(w_k)\;=\;f_k\;=\;f^+_k\;-\;f^-_k,\;1\;{\leq}\;k\;{\leq}\;r)$ where $d^+_i(e^+_j\;and\;f^+_k)$ is the number of positive edges incident with $u_i(v_j\;and\;w_k)$ and $d^-_i(e^-_j\;and\;f^-_k)$ is the number of negative edges incident with $u_i(v_j\;and\;w_k)$. The sequences ${\alpha}\;=\;[d_1,\;d_2,\;{\cdots},\;d_p],\;{\beta}\;=\;[e_1,\;e_2,\;{\cdots},\;e_q]$ and ${\gamma}\;=\;[f_1,\;f_2,\;{\cdots},\;f_r]$ are called the signed degree sequences of G(U, V, W). In this paper, we characterize the signed degree sequences of signed 3-partite graphs.

• International Journal of Automotive Technology
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• 제7권2호
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• pp.227-235
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• 2006

In this paper a robust image processing method with modified Otsu algorithm to recognize the road lane for a real-time controlled autonomous vehicle is presented. The main objective of a proposed method is to drive an autonomous vehicle safely irrespective of road image qualities. For the steering of real-time controlled autonomous vehicle, a detection area is predefined by lane segment, with previously obtained frame data, and the edges are detected on the basis of a lane width. For stable as well as psudo-robust autonomous driving with "good", "shady" or even "bad" road profiles, the variable threshold with modified Otsu algorithm in the image histogram, is utilized to obtain a binary image from each frame. Also Hough transform is utilized to extract the lane segment. Whether the image is "good", "shady" or "bad", always robust and reliable edges are obtained from the algorithms applied in this paper in a real-time basis. For verifying the adaptability of the proposed algorithm, a miniature vehicle with a camera is constructed and tested with various road conditions. Also, various highway road images are analyzed with proposed algorithm to prove its usefulness.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2124-2143
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• 2016

In Long Term Evolution-Advanced (LTE-A) systems, Inter-cell Interference (ICI) is a prominent limiting factor that affects the performance of the systems, especially at the cell edges. Based on the literature, Fractional Frequency Reuse (FFR) methods are known as efficient interference management techniques. In this report, the proposed Dynamic Fractional Frequency Reuse (DFFR) technique improved the capacity and cell edge coverage performance by 70% compared to the Fractional Frequency Reuse (FFR) technique. In this study, an improved power allocation method was adopted into the DFFR technique to reach the goal of not only reducing the ICI mitigation at the cell edges, but also improving the overall capacity of the LTE-A systems. Hence, an improved water-filling algorithm was proposed, and its performance was compared with that of other methods that were considered. Through the simulation results and comparisons with other frequency reuse techniques, it was shown that the proposed method significantly improved the performance of the cell edge throughput by 42%, the capacity by 75%, and the coverage by 80%. Based on the analysis and numerical expressions, it was concluded that the proposed DFFR method provides significant performance improvements, especially for cell edge users.

• 융합신호처리학회논문지
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• 제11권2호
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• pp.92-96
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• 2010

디인터레이싱 방식은 일반적으로 화면 간 디인터레이싱과 화면 내 디인터레이싱으로 나뉜다. 화면 내 디인터레이싱에서 가장 보편적인 방식은 라인카피와 라인별 평균값을 취하는 선형적인 방식이다. 또한 ELA(Edge Based Line Average), ELA를 변형시킨 방식 등이 에지를 이용한 디인터레이싱 방식들이다. 하지만 선형적 보간법은 에지 블러링이나 계단현상을 발생시키고, ELA나 변형된 ELA를 이용한 방식은 특정방향에지 정보가 부족해서 다양한 형태의 에지 부분에서의 디인터레이싱이 좋지 못하다. 본 논문은 7방향의 에지 방향 보간법과 수평방향의 에지라인을 고려한 화면 내 디인터레이싱 방식을 소개한다. 기존 방식에서 나타나던 오브젝트의 계단현상을 최대한 줄여줌으로써 보다 낳은 화질을 보인다.

• 한국측량학회지
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• 제20권4호
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• pp.405-413
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• 2002

연속지적도를 제작하기 위해서는 합리적으로 도면의 신축보정, 도곽접합, 행정구역 접합, 축척 간 접합 등을 처리할 수 있는 기준의 설정이 무엇보다 중요한 선결 과제라 할 수 있다. 본 연구는 지번부여지역단위 임의 도곽으로 작성된 임야도의 행정구역간 경계의 필지접합 및 지적임야도 접합에 2차원 비선형좌표변환방법인 사영투영과 부등각사상변환방법 및 다항식변환방법을 도입하여 행정구역 경계선상 또는 임야사정선상 굴곡점을 기준점으로 하여 2차원 좌표변환계수를 추출하고 연속지적도 작성을 위한 도면접합에 좌표변환방법의 활용을 시도하였다.

• 한국통신학회논문지
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• 제21권2호
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• pp.375-382
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• 1996

본 논문에서는 네트워크를 분할하여 국간신뢰도를 계산하는 효과적인 방법이 기술된다. 네트워크를 그래프로 모델화하고 그 그래프를 2개의 부분그래프로 부분그래프로 분할한다. 한 부분 그래프의 논리적항을 계산하고 논리 적항을 갖는 사상에 따라서 다른 부분그래프의 그래프를 만들고 논리적항을 계산한다. 부분그래프의 논리적항을 서로 곱해서 국간신뢰도를 계산하는 방법을 제안한다. 한 부분그래프의 모든 논리적항은 2의 그 부분그래프가 갖는 가지 수 제곱으로 계산되고 다른 부분그래프의 그래프가 갖는 논리적항은 그래프가 갖는 가지 수와 논리적항 수의 곱으로 계산할 수 있다. 이 방법은 분할하지 않고 국간 신뢰도를 계산하는 방법에 비해서 적은 계산시간을 갖는다.