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양정직(Yang, Jeong-Jik),이동주(Lee, Dong-Ju) 한국소음진동공학회 2010 한국소음진동공학회 논문집 Vol.20 No.11
The relation between the vibration induced from machinery and the radiated sound is complicated. Acoustic intensity method is widely used to obtain the accuracy of noise measurement and noise identification. In this study, as groundwork, the complex acoustic intensity method is performed to identify noise source and transmission path on different free space point source fields. As an industrial application, the complex acoustic intensity method is applied to HVAC to identify sound radiation characteristics in the near field. Experimental complex acoustic intensity method was applied to HVAC, it is possible to identify noise sources in complicated sound field characteristics which noise sources are related with each other, and certificate the validity of complex acoustic intensity. Especially, it can be seen that complex acoustic intensity method using both of active and reactive intensity is vital in devising a strategy for identification of noise. Also, the vector flow of acoustic intensity was investigated to identify sound intensity distributions and energy flow in the near field of HVAC.
Reverse Engineering을 이용한 석션 하우징의 음장해석
양정직(Jeong-Jik Yang),이동주(Dong-Ju Lee) 한국생산제조학회 2011 한국생산제조학회지 Vol.20 No.4
We tried to analyze sound field of the interior of housing installed with an impeller using the Boundary Element Method (BEM) with the Kirchhoff-Helmholtz integral equation. In order to increase the accuracy of our analysis, reverse engineering technology, which has been developed in recent years. We measured and treated geometrical data with 3D scanning of the practical research object. After modeling by the reverse engineering, we analyzed variation of the BPF as adding vibration frequency and variation of the sound field of the interior of housing by changing the number of impeller blades. We also tried an analysis of free degree variation. Then, we proposed the analysis accuracy and noise reducing method by analysis result.
Mask R-CNN과 겹침 처리 알고리즘을 활용한 상단의 원형 객체 검출 및 자세 추정
윤석현,양정직,김청준,황면중 제어·로봇·시스템학회 2023 제어·로봇·시스템학회 논문지 Vol.29 No.12
This paper proposes an algorithm for detecting and estimating the pose of top objects in a complex environment where thin metal circular plates are randomly stacked. In complex environments where multiple instances of the same object are randomly stacked, the robot needs to detect and compare objects to identify the top ones for grasping. Our approach involves a combination of deep learning-based instance segmentation and an overlap handling algorithm for precise top object detection. Subsequently, leveraging three-dimensional geometric data, we estimate the object's pose by determining its plane. To validate the proposed algorithm, we constructed two environments consisting of objects with different sizes and thicknesses. The first experiment quantitatively validated the object detection and overlap handling algorithm. The second experiment quantitatively compared different plane estimation algorithms. The third experiment quantitatively compared the pose of objects using the G-ICP (Generalized Iterative Closest Point) algorithm and the proposed algorithm against the ground truth pose. Additionally, we performed a qualitative comparison by visualizing the poses estimated by each algorithm in the images. In the experimental results, the overlap handling algorithm had an average success rate of 84.21%. Additionally, pose estimation using G-ICP before plane estimation frequently resulted in issues like drift in the center point and frequent misalignment with areas other than the object. On the other hand, pose estimation using G-ICP after plane estimation and the proposed algorithm yielded similar performance with average ADD-S values of 6mm or less. However, the pose estimated using the proposed algorithm resulted in a minimum 0.25x reduction in execution time compared to the G-ICP algorithm.
3D프린팅 주형의 표면품질 향상을 위한 도형제 적용기술 연구
이환종,양정직,현효진 한국생산제조학회 2018 한국생산제조학회지 Vol.27 No.6
Three-dimensional (3D) printing technology is a new and widely use technology in the manufacturing industry. However, the domestic manufacturing industry is underutilized due to various manufacturing flaws and surface quality problems. This study intended to derive ways to improve the surface quality of products by improving the surface roughness of the sand mold manufactured by 3D printing. The test results confirmed improved viscosity control of the mold wash coated on the surface of the sand mold. In conclusion, it was possible to derive that the mold wash had a direct effect on the sand mold surface and to improve surface quality through coating methods on the mold and core.
사형 주조 3D 프린팅용 소재의 기계적 특성 및 신뢰성
손현진,장성완,이환종,양정직,정영근,배창준,Son, Hyeon Jin,Jang, Seongwan,Lee, Hwan Jong,Yang, Jeong Jik,Jeong, Yeong Geun,Bae, Chang-Jun 한국재료학회 2020 한국재료학회지 Vol.30 No.1
Sand casting 3D printing uses a binder jetting method to produce a mold having complicated shape by spraying a binder on sand coated with activator. Appropriate heat treatment process in sand mold fabrication can increase the degree of polymerization to improve flexural strength. However, long heat treatment of over 24 hours decreases flexural strength and reliability due to chemical bond decomposition through thermal degradation. The main role of the activator is to control the reaction rate between the polymer chains. As a result, when the activator composition is increased from 0.15 wt% to 0.25 wt%, the flexural strength is increased by 218 N/㎠. However, excess activator (0.40 wt%) has been shown to decrease reliability without increasing flexural strength. The main role of the binder is to control the flexural strength of the specimen. As the binder composition is increased from 2.00 wt% to 4.00 wt%, the flexural strength increases to about 255 N/㎠, indicating the maximum flexural strength increase. Finally, the reliability of the flexural strength of the fabricated specimens is evaluated by a Weibull plot. Weibull modulus calculations are used to evaluate the flexural strength reliability of the specimens, and maximum reliability value of 11.7 is obtained at 0.20 wt% activator composition. Therefore, it is confirmed that this composition has maximum flexural strength reliability.