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최원식,프라타마 판두 산디,수페노 데스티아니,변재영,이은숙,우지희,양지웅,키프 디마스 하리스 신,크리스타 마이난다 브리기타,오케추쿠 나에메카 니콜라스,이강삼,Choi, Wonsik,Pratama, Pandu Sandi,Supeno, Destiani,Byun, Jaeyoung,Lee, Ensuk,Woo, Jihee,Yang, Jiung,Keefe, Dimas The Korean Society of Industry Convergence 2018 한국산업융합학회 논문집 Vol.21 No.5
In this research, the effect of normal load, sliding velocity, and texture density on thefriction coefficient of surfaces micro-textured on AISI 4140 under paraffin oil lubrication were investigated. The predicted tribological behavior by numerical calculation can be serves as guidance for the designer during the machine development stage. Therefore, in this research friction coefficient prediction model based on response surface methodology (RSM), support vector machine (SVM), and artificial neural network (ANN) were developed. The experimental result shows that the variation of load, speed and texture density were influence the friction coefficient. The RSM, ANN and SVM model was successfully developed based on the experimental data. The ANN model can effectively predict the tribological characteristics of micro-textured AISI 4140 in paraffin oil lubrication condition compare to RSM and SVM.
Wonsik Choi(최원식),Pandu Sandi Pratama(프라타마 판두 산디),Destiani Supeno(수페노 데스티아니),Jaeyoung Byun(변재영),Ensuk Lee(이은숙),Jiung Yang(양지웅),Dimas Harris Sean Keefe(키프 디마스 하리스 신),Yeonho Jeon(전연호),Sungwon Chung(정성원) 한국산업융합학회 2018 한국산업융합학회 논문집 Vol.21 No.5
In this research, tricycle vehicle simulation based on multi-body environment has been introduced. Mathematical model of tricycle vehicle was developed. In this research the left and right wheel speed are calculated based on the rear steering angle and velocity. The kinematic model for the three - wheel drive system was completed and the results were analyzed using the actual vehicle drawings. Through simulink vehicle performance on linear and rotation movement were simulated. Using the mathematical model the control system can be applied directly to the tricycle vehicle. The simulation result shows that the proposed vehicle model is successfully represent the movement characteristics of the real vehicle. This model assists the vehicle developer to create the controller and understand the vehicle during the development process.
최원식(Wonsik Choi),김유창(Yuchang Kim) 대한인간공학회 2020 大韓人間工學會誌 Vol.39 No.4
Objective: The purpose of this study is to evaluate the workload in the posture of raising the arm above the shoulder, which is the cause of musculoskeletal disorders. Background: The modern industrial structure is becoming automation due to the development of science and technology. However, many works in the manufacturing sector such as the shipbuilding industry, heavy industry, and automobile assembly are still working in the posture of raising the arm above the shoulder for a long time. Muscle fatigue from these works can be lead to severe symptoms such as musculoskeletal disorders over time. Method: Seven healthy males without musculoskeletal disorders participated in the experiment. We measured the muscle activity of the deltoid muscle, trapezius muscle, and biceps according to changes in the angle of arm and weight in the posture of raising the arm above the shoulder. In addition, fatigue measures included subjective discomfort ratings through the Borg"s CR-10 scale. ANOVA was used to analyze the influence of the angle of arm and weight. Results: ANOVA showed that the weight factors of the deltoid muscle, trapezius muscle, and biceps were statistically significant on EMG and subjective discomfort. In addition, only the arm angle factors of the deltoid muscle, except the trapezius muscle and biceps, were statistically significant on EMG and subjective discomfort. When we measured the EMG and subjective discomfort according to each muscle part in the posture of raising the arm above the shoulder, it was found that the deltoid muscle had the highest workload. Conclusion: In this study, muscle activity and subjective discomfort were measured according to changes in the angle of arm and weight in the posture of raising the arm above the shoulder. It was found that the average value of %MVC and Borg"s scale were the highest on the deltoid muscle. This result means that a deltoid muscle could be easily exposed to musculoskeletal disorders than trapezius muscle and biceps. Further research should be conducted considering the characteristics such as working time, gender, and age. Application: These results can contribute to preventing musculoskeletal disorders and improving work efficiency at industrial sites, and can be used as basic data for research on the upper extremity.
최원식(Wonsik Choi),김원구(Wongu Kim),권주리(Jury Kwon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Our teeth was one of the most important internal organ, Whenever we chewing the food and drink something our teeth undergo various influences on the wearing. In this study we tested the gold alloy dental prosthesis in several lubricant- cola, soju, coffee, toothpaste and milk of the various speed and load conditions. In case of the toothpaste the friction coefficient was very lower and the coffee was the worst in the wearing.
Wonsik Choi(최원식),Pandu Sandi Pratama(프라타마 판두 산디),Destiani Supeno(수페노 데스티아니),Jaeyoung Byun(변재영),Ensuk Lee(이은숙),Jihee Woo(우지희),Jiung Yang(양지웅),Dimas Harris Sean Keefe(키프 디마스 하리스 신),Maynanda Brigita Chry 한국산업융합학회 2018 한국산업융합학회 논문집 Vol.21 No.5
In this research, the effect of normal load, sliding velocity, and texture density on thefriction coefficient of surfaces micro-textured on AISI 4140 under paraffin oil lubrication were investigated. The predicted tribological behavior by numerical calculation can be serves as guidance for the designer during the machine development stage. Therefore, in this research friction coefficient prediction model based on response surface methodology (RSM), support vector machine (SVM), and artificial neural network (ANN) were developed. The experimental result shows that the variation of load, speed and texture density were influence the friction coefficient. The RSM, ANN and SVM model was successfully developed based on the experimental data. The ANN model can effectively predict the tribological characteristics of micro-textured AISI 4140 in paraffin oil lubrication condition compare to RSM and SVM.
Friction Characteristics of CNx Coated Dimple Pattern with Hexagonal Array
wonsik Choi(최원식),Noritsugu Umehara 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.5
In this study, we examined the friction characteristics of a dimple pattern on a carbon nitride coating. The study was conducted with a hexagonal array 40 ㎛ dimple pattern on a steel bearing containing a CNx coating. The area density of the dimple patterns were varied between 5% and 25%, the speed was varied from 0.06-0.26 ㎧, and the load was varied between 20-100N. In general, we found that as the velocity increased, the friction coefficient increased. Furthermore, the friction coefficient was lowest at a load of 40N. The friction coefficient of the non-coated specimen was 0.025-0.15; on the other hand, the friction coefficient of the coated specimen was 0.002-0.02. Thus, we determined that the coated materials could reduce the friction coefficient by a factor of 7.5.
쿨링용 슬레트 핀 M/C Form Roll의 Roll Stand부 마찰 특성
최원식(Wonsik Choi),이성용(Sungyong Lee),권주리(Jury Kwon),진은영(Eunyoung Jin),문희준(Heejoon Mun),이인(In Lee) 한국트라이볼로지학회 2010 한국윤활학회지(윤활학회지) Vol.26 No.1
This study investigates the friction of the roll stands in the high performance multi- holes slate fin machine which pin is using in heat transfer of radiator, oil cooler, inter cooler, condenser and evaporator. The roll stand part is very important to maintain the high performance fin machine. This multi-holes form roll type is the first time in our country so it will be helpful to increases the export and product of heat transfer. It was include the technical of form rolling system which was self development. Then it will be improve the electric home appliances, future motor vehicle device and industrial machine.
도시숲과 가로수가 대기 흐름과 기온에 미치는 영향에 관한 수치 연구
강건,최원식,김재진,Kang, Geon,Choi, Wonsik,Kim, Jae-Jin 대한원격탐사학회 2022 大韓遠隔探査學會誌 Vol.38 No.6
This study investigated the effects of the urban forest and street trees on flow and temperature distribution in the Daegu National Debt Redemption Movement Memorial Park. For this, we implemented tree-drag and tree-cooling parameterization schemes in a computational fluid dynamics (CFD) model and validated the simulated wind speeds, wind directions, and air temperatures against the measured ones. We used the wind speeds, wind directions, air temperatures predicted by the local data assimilation and prediction system (LDAPS) as the inflow boundary conditions. To investigate the flow and thermal characteristics in the presence of trees in the target area, we conducted numerical experiments in the absence and presence of trees. In the absence of trees, strong winds and monotonous flows were formed inside the park, because there were no obstacles inducing friction. The temperature was inversely proportional to the wind speed. In the presence of trees, the wind speeds(temperatures) were reduced by more than 40 (5)% inside the park with a high planting density due to the tree drag (cooling) effect, and those also affected the wind speeds and temperatures outside the park. Even near the roadside, the wind speeds and temperatures were generally reduced by the trees, but the wind speeds and air temperatures increased partly due to the change in the flow pattern caused by tree drag.