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유한요소격자에 기초한 일반적인 금형면 묘사와 3차원 박판성형공정에의 응용
윤정환,김종봉,양동열,김석관,유동진,이재진,Yun, Jeong-Hwan,Kim, Jong-Bong,Yang, Dong-Yeol,Kim, Seok-Gwan,Yu, Dong-Jin,Lee, Jae-Jin 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.3
One of the most important factor to be considered for the analysis of sheet metal forming processes is the tool surface description for arbitrarily- shaped sheet metal parts. In the present study , finite element approach is used to describe the arbitrarily shaped tool surface. In finite element mesh approach, tool surfaces ar, described by finite elements. The finite elements mesh description of the tool surface, which is originally described by CAD data, needs much time and time-consuming graphic operation. The method, however, has been widely used to describe a complex tool surface. In the present study, the contact searching algorithm for the finite element mesh approach is developed based on cell strategy method and sheet surface normal scheme. For the verification purpose, a clover cup drawing, Baden-Baden oilpan problem and a trunk floor drawing were investigated. The computational results based on the finite element approach were compared with the results of available parametric patch approach and experiments.
TLC와 컬러화상처리를 이용한 Hele-Shaw Cell 내부 대류 온도장 측정
윤정환,도덕희,이상준,Yun, Jeong-Hwan,Do, Deok-Hui,Lee, Sang-Jun 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.3
Variation of temperature field in a Hele-Shaw convection cell was measured by using a HSI true color image processing system and TLC(Thermochromic Liquid Crystal) solution. The relationship between the hue value of TLC color image and real temperature was obtained and this calibration result was used to measure the true temperature. The temperature field in the Hele-Shaw convection cell shows periodic characteristics of 45 sec at Ra = 9.3 * 10$\^$6/. The temperature field measurement technique developed in this study was proved to be a useful and powerful tool for analyzing the unsteady thermal fluid flows.
Stereoscopic PIV 기법의 개발과 이를 이용한 축류 홴 후류의 유동해석
윤정환,이상준,Yun, Jeong-Hwan,Lee, Sang-Jun 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.2
A stereoscopic PIV (SPIV) measurement system based on the translation configuration was developed and applied to the flow behind a forward-swept axial-fan. Measurement of three orthogonal velocity components is essential for flow analysis of three-dimensional flows such as flow around a fan or propeller. In this study, the translation configuration was adopted to calculate the out-of-plane velocity component from 2-D PIV data obtained from two CCD cameras. The error caused by the out-of-plane motion was estimated by direct comparison of the 2-D PIV and 3-D SPIV results that measured from the particle images captured simultaneously. The comparison shows that the error ratio is relatively high in the region of higher out-of-plane motion near the axial fan blade. The turbulence intensity measured by the 2-D PIV method is bigger by about 5.8% in maximum compared with that of the 3-D SPIV method. The phase-averaged velocity field results show that the wake behind an axial fan has a periodic flow structure with respect to the blade phase and the characteristic flow structure is shifted downstream in the next phase.
시ㆍ공간 중복성을 고려한 다이내믹 프로그래밍 기반의 고속 변이 추정 기법
윤정환(Jung-hwan Yun),배병규(Byung-kyu Bae),박세환(Se-hwan Park),송혁(Hyok Song),김동욱(Dong-wook Kim),유지상(Ji-sang Yoo) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.10C
본 논문에서는 스테레오 정합에 사용되는 다이내믹 프로그래밍을 기반으로 영상의 시ㆍ공간적 중복성을 고려한 고속 변이 추정 기법을 제안한다. 영상 내 인접한 화소 간에 존재하는 높은 상관성을 이용하여 격행으로 다이내믹 프로그래밍 기반의 변이 추정을 수행하고 변이가 할당되지 않은 라인은 동일영역 내에서의 변이가 유사하다는 성질을 이용하여 주변의 변이벡터로 할당하였다. 또한 동영상의 변이 추정 시에는 프레임 간의 시간적 중복성을 고려한 알고리즘으로 수행시간을 크게 단축시킬 수 있었다. 모의 실험을 통하여 변이 정보를 이용한 중간시점 영상 생성 결과 블록매칭 알고리즘에 비하여 0.8~2.4㏈의 PSNR(peak signal to noise ratio)이 증가하는 것을 확인하였다. 또한 일반적인 다이내믹 프로그래밍 기반의 변이 추정 방식과의 비교에서도 0.1㏈가량의 PSNR이 증가하였으며 약 48~68%의 계산량이 감소하는 것을 확인 할 수 있었다. In this paper, we propose a fast disparity estimation method considering temporal and spatial redundancy based on a dynamic programming for stereo matching. For the first step, the dynamic programming is performed to estimate disparity vectors with correlation between neighboring pixels in an image. Next, we efficiently compensate regions, which disparity vectors are not allocated, with neighboring disparity vectors assuming that disparity vectors in same object are quite similar. Moreover, in case of video sequence, we can decrease a complexity with temporal redundancy between neighboring frames. For performance comparison, we generate an intermediate-view image using the estimated disparity vector. Test results show that the proposed algorithm gives 0.8~2.4㏈-increased PSNR(peak signal to noise ratio) compared to a conventional block matching algorithm, and the proposed algorithm also gives approximately 0.1㏈-increased PSNR and 48~68%-lower complexity compared to the disparity estimation method based on general dynamic programming.
윤정환 ( Yun Jeong Hwan ) 미래군사학회 2019 한국군사학논총 Vol.8 No.1
The purpose of this paper is to identify the problems of regional defense operations units and to suggest a method of regional defense operations considering the posterior regional operations environment. In summary, First, the units for regional defense operations are divided into active units and reserve forces. Eventually, active forces are also organized as reserve forces, which is expected to limit the use of combat power. Therefore, it should be improved to maintain a high level of combat power by improving the percentage of full army units. The mission should clearly distinguish between active and reserve forces. Second, it is necessary to change the concept of regional defense operations, which is to carry out civilian, military, and military combat operations in units of battalions. The civil defense, military, and military combat operations should be planned by the local defense division, To this end, it is necessary to coordinate the formation of the solidarity and to organize the entire battalion and one city, county, and district. Third, the Unified Defense Support Headquarters operated by Eup, Myeon, and Dong should be integrated into city, county, and county. Fourth, in order to overcome the difficulties of the commander of the regional defense operation unit, it is necessary to remove the basis of the budget for the upbringing support of the local governments specified in the reserve army establishment law and reflect the budget for the reserve army in the defense budget.