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DED Additive Manufacturing Using Auto-Surface Tracking Technology
하태호(Taeho Ha),허세곤(Segon Heo),이창우(Changwoo Lee),정민교(Min-Kyo Jung),최장욱(Jang-Wook Choi) Korean Society for Precision Engineering 2023 한국정밀공학회지 Vol.40 No.3
Directed energy deposition (DED) additive manufacturing technology enhances the functionality of existing or damaged parts by adding metallic materials to the surfaces. Blown-powder DED technology utilizes a focused, high-energy source to fuse the part’s surface with the supplied metal powder. Maintaining a constant stand-off distance (SOD), the distance between the deposition head and the workpiece, is a key factor in ensuring deposition quality, as variations in SOD will change the powder focus position and the laser spot size on the surface. Therefore, traditional additive manufacturing systems require CAD or pre-scanned surface data. In this study, we proposed auto-surface tracking technology. No workpiece CAD data or pre-scanned surface data are required, and in-situ measurement and feedback control can automatically consider the deposition height differences that cause a change in SOD when depositing the next layer. The accuracy of the SOD measurements and feedback control error was verified using a step height sample. The mean SOD measurement error was 4.7 ㎛ with a standard deviation of 42 ㎛ (reference SOD, 14 ㎜). The feasibility of the autosurface tracking technology was confirmed through the additive manufacturing processes of the gear and an actual blanking mold applied in the defense and industrial fields.
하태호 ( Tae Ho Ha ),김성운 ( Sung Woon Kim ),김진구 ( Jin Gu Kim ),박상범 ( Sang Bum Park ) 경북대학교 중등교육연구소 2012 중등교육연구 Vol.60 No.1
이 연구의 목적은 활동관찰이 개방기술인 축구드리블 과제 학습에 미치는 영향을 분석함으로써 운동기능학습의 촉진을 위한 활동관찰 프로그램의 적용 가능성을 알아보는데 있다. 실험에 참여한 피험자는 만14세의 남자 중학교 2학년 40명으로 축구드리블 수행에 아무런 장애가 없는 신체적, 정신적으로 건강한 오른발잡이들로만 참여하였다. 축구드리블 동작수행 시간에 따른 집단(4)×측정시점(4)에 대한 반복측정 이원분산분석을 실시하였고, Tukey`s HSD를 사용하여 사후검증을 실시하였다. 종속변수는 축구드리블 동작수행 시간이다. 연구결과 활동관찰은 환경이 변화하고 예측하기 어려운 특성을 지니고 있는 개방기술인 축구드리블 기술학습을 촉진시킬 수 있음을 보여주었다. 또한 활동관찰은 신체연습과 병행 되었을 때 가장 큰 효과를 지닐 수 있으며, 활동관찰과 신체연습의 병행은 어느 한 가지 연습방법을 통해 얻을 수 있는 것 이상의 학습경험을 제공할 수 있음을 보여주었다. 그러므로 이 연구 결과를 종합해 보면 운동기능 학습에서 활동관찰은 운동기능의 학습을 촉진 시킬 수 있는 인지적 중재방법으로써 그 가능성이 높다고 사료된다. The purpose of this study was to examine the effectiveness of action observation on the performance and learning of a soccer dribbles task. Forty middle school students whose ages ranged from 14 to 15 years (M=14. 00) participated in this experiment. The participants were randomly assigned to one of four experimental conditions: (1) action observation group(n=10), (2) physical practice group(n=10), (3) simultaneous group which practiced AO and PP alternatively(n=10), (4) control group (n=10). Data was analyzed using two-way ANOVAs with repeated measures of group(4) and time(4). Dependent variables were soccer dribbles time. The results of this study indicated that the AO, PP, and simultaneous group were also superior to the control group, and in particular the simultaneous group was faster than the AO, PP group in response time for soccer dribbles. These results suggests that action observation can facilitate the performance of a soccer dribbles and its effect can be maximized when performed simultaneously with the physical practice.