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A study on the prediction of bead geometry in the robotic welding system
J. S. Son,김일수,H. H. Kim,I. J. Kim,B. Y. Kang,김희진 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.10
The gas metal arc (GMA) welding is one of the most widely-used processes in metal joining process that involves the melting and solidification of the joined materials. To solve this problem, we have carried out the sequential experiment based on a Taguchi method and identified the various problems that result from the robotic GMA welding process to characterize the GMA welding process and establish guidelines for the most effective joint design. Also using multiple regression analysis with the help of a standard statistical package program, SPSS, on an IBM-compatible PC, three empirical models (linear, interaction, quadratic model) have been developed for off-line control which studies the influence of welding parameters on bead width and compares their influences on the bead width to check which process parameter is most affecting. These models developed have been employed for the prediction of optimal welding parameters and assisted in the generation of process control algorithms.
티타늄 산화물과 유화물의 전지 전압을 결정하는 요소에 대한 제일원리계산
김희진(H. J. Kim),문원진(W. J. Moon),김영민(Y. M. Kim),배경서(K. S. Bae),윤재식(J. S. Yoon),이영미(Y. M. Lee),국진선(J. S. Gook),김양수(Y. S. Kim) 한국표면공학회 2009 한국표면공학회지 Vol.42 No.1
Electronic structures and chemical bonding of Li-intercalated LiTiS2 and LiTiO₂ were investigated by using discrete variational Xα method as a first-principles molecular-orbital method. α-NaFeO₂ structure is the equilibrium structure for LiCoO₂, which is widely used as a commercial cathode material for lithium secondary battery. The study especially focused on the charge state of Li ions and the magnitude of covalency around Li ions. The average voltage of lithium intercalation was calculated using pseudopotential method and the average intercalation voltage of LiTiO₂ was higher than that of LiTiS2. It can be explained by the differences in Mulliken charge of lithium and the bond overlap population between the intercalated Li ions and anions in LiTiO₂ as well as LiTiS₂. The Mulliken charge, which means the ionicity of Li atom, was approximately 0.12 in LiTiS₂ and the bond overlap population (BOP) indicating the covalency between Ti and S was about 0.339. One the other hands, the Mulliken charge of lithium was about 0.79, which means that Li is fully ionized. The BOP, the covalency between Ti and O, was 0.181 in LiTiO₂. Because of high ionicity of Li and the weak covalency between Ti and the nearest anion, LiTiO₂ has a higher intercalation voltage than that of LiTiS₂.