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부직포 균제도 해석을 위한 공분산-시장 함수의 유도(I) -1차원 영상 신호의 경우-
김주용,Kim Jooyong 한국섬유공학회 2004 한국섬유공학회지 Vol.41 No.6
A method is introduced for deriving the 'covariance length curve (Cov-L)' from the existing variance length curve. Some critical information hidden in existing variance length curve will be revealed through the Cov-L derived. It includes the correlation between any arbitrary measurement lengths, which is not readily available from the variance length curve but that is critical. Correlation functions of arbitrary measurement lengths are derived directly from the variance length curve given without requiring any further information. Use of the correlation functions has more advantages over the traditional V-L curves. First, they represent a yarn diameter (or mass) profile both in scale (resolution) and frequency (periodicity) rather than in scale only which is the case for V-L curves. Second, periodicities hidden in seemingly irregular signals are easily detected and revealed by the correlation functions. It is also beneficiary that the functions are readily available from a V-L curve without further efforts for measurement and analysis.
기하학적 영상 처리를 이용한 나노 섬유 웹의 기공 분포 측정
김주용,이정해,임대영,변성원,Kim Jooyong,Lee Jung Hae,Lim Dae Young,Byun Sung Won 한국섬유공학회 2004 한국섬유공학회지 Vol.41 No.6
An image processing algorithm has been developed in order to anlyze the nanofiber web images from a high magnification microscope. It has been known that precise pore detection of thick webs is extremely difficult mainly due to lack of light uniformity, difficulty of fine focusing and translucency of nanofiber web. The serial morphological image processing techniques of edge detection, dilation, opening, skeletonization and dilation have been applied to images for accurate pore detection followed by connect-component labeling for computing mean pore size and standard deviation of pore sizes. The pore detection algorithm developed has been found to show excellent performance in characterizing the porous structure, thus being a promising tool for the on-line quality control of eletrospun fiber manufacturing.
한계상태 설계법을 이용한 지역난방 열배관의 국부좌굴 연구
김주용(Jooyong Kim),이상연(Sang-youn Lee),고현일(Hyun Il Ko),조종두(Chongdu Cho) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.12
지역난방은 열병합 발전소에서 생산된 열을 온수의 형태로 열배관 네트워크를 통해 넓은 지역에 일괄적으로 공급하는 난방시스템이다. 일반적으로 지역난방 열배관은 지중에 매설되며 내부를 흐르는 온수의 압력과 온도변화, 매설 토사와의 마찰 및 반력에 의한 하중을 받게 되므로 열공급 효율과 함께 기계적인 안전성에 대한 검토가 반드시 필요하다. 본 논문에서는 강관의 한계상태 설계법을 이용하여 한계판폭두께비와 한계변형률, 두 가지 관점에서 열배관의 국부좌굴 발생여부를 평가하였으며 그 결과 현재 국내에서 사용되고 있는 모든 열배관은 국부좌굴이 발생하지 않음을 확인하였다. 마지막으로 국부 좌굴을 피하기 위한 최소 예열온도를 산출함으로써 예열온도에 대한 시공 기준을 제시하였다. The district heating system distributes the heat generated from a cogeneration plant to wider locations. In this process, the district heating pipe (DHP) is subjected to internal and external loadings. The internal loadings are generally caused by the operating conditions such as water temperature and internal pressure. Frictional interactions between the pipes and the soil contribute to the external loadings. Thus, investigation of the mechanisms of failure of DHPs will help to guarantee both mechanical stability and heating efficiency. In this study, we investigate the local buckling of DHPs using limit state design (LSD). Two methods are considered: the use of the limit state for the width-thickness ratio and the use of the limit state for the strain. The results are used to confirm that the DHP is stable under local buckling. Finally, we suggest a minimum preheating temperature for avoiding local buckling.