• Journal of Drive and Control
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• v.16 no.3
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• pp.33-41
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• 2019

This study presents the development of a lifetime test bench for the strain wave reducer which is a precision gear reducer of the robot to realize fault diagnosis and failure prognostics. To this end, the lifetime test bench was designed to detect the vertical forward/reverse direction rotation load. Through the lifetime test bench, it is possible to apply the same load spectrum from robot working scenarios. We developed a data integration gateway for fault data collection. Through the development of dedicated software for fault diagnosis and failure prognostics, these data from vibration, noise and temperature sensors were collected and analyzed along with the operation of the lifetime evaluation.

• Journal of the Korean institute of surface engineering
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• v.52 no.3
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• pp.171-179
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• 2019

We have developed a numerical model to analyze flow dynamics and heat transfer characteristics of the cooling water in a circular rotating magnetron cathode by a moving boundary grid method realized in a commercial multiphysics package, CFD-ACE+. The numerical model is composed of a target, dual mass rotating cathode and cooling water connections. When the inlet and outlet of the cooling water are offset by the same distance from the rotation axis, the temperature at the center is higher by $50^{\circ}C$ at maximum. At 5 mm away from the target surface, the temperature profile showed typical center high characteristic. At heat input of 30 kW, the maximum temperature change of the cooling water hits $6^{\circ}C$ within 0.5 sec under 60 rpm. With a cooling water configuration of center in/edge out, the temperature of the center region of the target gets lowered. Within 100 seconds of plasma operation time, the cooling water temperature keeps getting higher.

• Steel and Composite Structures
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• v.32 no.6
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• pp.769-778
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• 2019

The specially prefabricated steel moment connections with pyramid head is one of the significant innovations in the steel structures forms to improve the installation time and simplify the construction procedure. The beams in this structure form are supported by two top and bottom angles and web double angles. Such a configuration despite its advantages increases the welding operation and filed installation time and costs. In this paper, the effect of using beams with channel and I section in three classes of seismically compact, seismically non-compact, and slender section according to width-to-thickness ratio on the behavior of the connection was investigated under monotonic and cyclic loading. Modeling was performed by ABAQUS and verified by the results of an experimental specimen. The findings indicated that using I and channel section instead of angle section reduces the amount of welding materials as well as easing the installation procedure. However, it has no significant effect on the ultimate strength and ductility of the connection. Furthermore, if the beam section is seismically compact, this form is considered as a special moment frame that has a rotation capacity up to 0.04 radians without any reduction in connection moment resistance.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.85-92
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• 2018

This study aimed to reduce of traps incident of metro train door by suggesting preventive actions throughout analyzing why railway drivers and passengers commit unsafe behaviors which are human factors making occurrence of the incidents. The incident cases were analyzed and Incident Tree was structured by brainstorming with safety experts. In addition, the questionnaire survey was conducted for comparison with the analysis results. As the result, this study suggested driver's factors, passenger's factors, and public relation plan for safe use of metro in order to reduce the frequency of the incidents. For driver's factors, implementing job-rotation systems between railway and non-railway drivers, installing Object Detection Sensors between the metro doors and PSD, and flexible operation of dwell time were suggested. For passenger's factors, placing a platform safety person, installing a safety fence in front of the stairs and the elevators, and country wide public relations through mass media were suggested.

• Journal of the Korean Burn Society
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• v.24 no.2
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• pp.64-67
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• 2021

Free flap surgery is commonly used for extensive facial burn. However, free flap surgery requires long operation time and difficult technique. Also, it requires further procedure to prepare the recipient vessels. Hence, applying pedicle flap surgery instead of free flap surgery is effective for patients with facial burn. Among a wide range of pedicle flaps, we performed lower trapezius myocutaneous pedicle flap to patients with third degree facial burn and got satisfactory results without complications. Lower trapezius myocutaneous pedicle flap has a wide arc of rotation so that it can cover middle and lower part of the face. Furthermore, it is thinner than other myocutaneous pedicle flap that can be used for facial reconstruction. Due to these advantages, lower trapezius myocutaneous pedicle can be an attractive option for the reconstruction of facial burn.

• The Journal of Korea Robotics Society
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• v.18 no.3
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• pp.337-345
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• 2023

In this paper, we propose a 3D LiDAR sensor-based costmap generation and path planning algorithm using it for reliable autonomous flight in complex indoor environments. 3D path planning is essential for reliable operation of UAVs. However, existing grid search-based or random sampling-based path planning algorithms in 3D space require a large amount of computation, and UAVs with weight constraints require reliable path planning results in real time. To solve this problem, we propose a method that divides a 3D space into several 2D spaces and a path planning algorithm that considers the distance to obstacles within each space. Among the paths generated in each space, the final path (Best path) that the UAV will follow is determined through the proposed objective function, and for this purpose, we consider the rotation angle of the 2D space, the path length, and the previous best path information. The proposed methods have been verified through autonomous flight of UAVs in real environments, and shows reliable obstacle avoidance performance in various complex environments.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.4
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• pp.67-77
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• 1995

In modern industry the requirement of automation of manufacturing process increases so that unmanned system has been popular as an ultimate goal of modern manufacturing process. In unmanned manufacturing process the tool fracture is a very serious problem because it results in the damage of workpieces and can stop the operation of whole manufa- turing system. In this study, image processing technique is used to detect the fracture of insert tip of face milling using multi-point-tool. In order to acquire the image information of fracture shape of rotation insert tip. We set up the optical system using a light beam chopper. In this system we can reduce the image degradation generated from stopped image of rotating insert tip using image restoration technique. We calculated the mean square error to diagnose the condition of tool fracture, and determind the criteria of tool fracture using experimental and staticstical method. From the results of this study we've developed non- contact detection technique of tool fracture using image processing method and proposed the fracture direction of automation and unmanned system considering the optimal time of tool change milling.

• Korean Journal of Agricultural Science
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• v.50 no.4
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• pp.817-828
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• 2023

Deteriorating soil physical properties and increasing soil pathogens due to the continuous cultivation of field crops are the leading causes of productivity deterioration. Crop rotation, soil heat treatment, and chemical control are used as pest control methods; however, each has limitations in wide application to domestic agriculture. In particular, chemical control requires improvement due to direct exposure to sterilizing solution, odor, and high-intensity work. To improve the overall domestic agricultural environment, the problems of time and cost, such as field maintenance and cultivation scale, must be addressed; therefore, mechanization technology for chemical control must be secured to derive improvement effects in a short period. Most related studies are focused on the control effect of the DMDS (dimethyl disulfide) sterilizer, and research on the performance of the sterilization spray device has been conducted after its introduction in Korea, but research on the corrosion suitability of the material is lacking. This study conducted a corrosion test to secure the corrosion resistance of a soil sterilizer injection pump, and a mechanical failure mode by corrosion by the material was established. The corrosion test comprised operation and neglect tests in which the sterilizing solution was circulated in the pump and remained in the pump, respectively. As a result of the corrosion test, damage occurred due to the weakening of the mechanical strength of the graphite material, and corrosion resistance to aluminum, stainless steel, fluororubber, and PPS (polyphenylene sulfide) materials was confirmed.

• Tribology and Lubricants
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• v.40 no.1
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• pp.1-7
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• 2024

Ball bearings are a major component of mechanical parts for transmitting rotation. Compared to tapered roller bearings, ball bearings offer less rolling resistance, which leads to reduced heat generation during operation. Because of these characteristics, ball bearings are widely used in electric vehicles and machine tools. The design of ball bearing cages has recently emerged as a major issue in ball bearing design. Cage design requires pre-verification of performance using theoretical or experimental formula or computational fluid dynamics (CFD). However, CFD analysis is time-consuming, making it difficult to apply in case studies for design decisions and is mainly used in performance prediction following design confirmation. To use CFD in the early stages of design, main-taining analytical accuracy while reducing the time required for analysis are necessary. Accordingly, this study proposes a laminar steady-state segment CFD technique to solve the problem of long CFD analytical times and to enable the use of CFD analysis in the early stages of design. To verify the reliability of the CFD analysis, a bearing drag torque test is performed, and the results are compared with the analytical results. The proposed laminar steady-state segment CFD technique is expected to be useful for case studies in bearing design, including cage design.

• The Journal of the Korean bone and joint tumor society
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• v.14 no.1
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• pp.33-43
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• 2008

Purpose: To evaluate the clinical usability of reconstructive methods, and how to select flap after wide excision of malignant soft tissue tumor in ankle and foot. Materials and Methods: The 15 cases shown in the 14 patients (In case of a male patient, reconstruction was performed two times due to local recurrence.) with malignant soft tissue tumor in ankle and foot, who underwent reconstruction after wide excision from March 2000 until March 2007. Oncologic, surgical and functional results were evaluated. Results: The method of reconstruction used were anterolateral thigh perforator flap (5cases), Reversed superficial sural artery flap (4 cases), dorsalis pedis flap (3 cases), local flap (3cases). The defect, mean size was $5.5{\times}5.7\;cm$, was reconstructed with rotation flap or free flap, mean size was $5.9{\times}6.0\;cm$, skin graft for remnant. The mean operation time was 310 minutes (120~540 minutes); it took 256 minutes to reconstruct by rotation flap, and 420 minutes by free flap. As oncologic results, 7 patients were no evidence of disease, 6 patients were alive with disease and 1 patient was expired by pulmonary metastasis at the time of the last follow-up. 4 patients had local recurrence and 4 pateints had distant metastases. As functional results, 14 patients were evaluated with average score of 68.8% using the system of the Musculoskeletal Tumor Society. Conclusion: The dorsalis pedis and reverse superficial sural artery rotation flap which is easy procedure, has less complication and takes short operation time, can be primarily considered to reconstruct a small defect. And the anterolateral thigh perforator flap is suitable for coverage of a large defects after wide excision of malignant soft tissue tumor in ankle and foot.