• 한국소음진동공학회논문집
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• 제20권2호
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• pp.185-190
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• 2010

Condition monitoring(CM) is a method based on non-destructive test(NDT). So, recently many kind of NDT were applied for CM. Acoustic emission(AE) is widely used for the early detection of faults in rotating machinery in these days because of high sensitivity than common accelerometers and detectable low energy vibration signals. And crack is considered one of severe fault in the rotating machine. Therefore, in this paper, study on early detection using AE has been accomplished for the crack of the low-speed shaft. There is a seeded initial crack on the shaft then the AE signal had been measured with low-speed rotation as the applied load condition. The signal detected from crack in rotating machine was detected by the AE transducer then the trend of crack growth had found out by using some of feature values such as peak value, skewness, kurtosis, crest factor, frequency center value(FC), variance frequency value(VF) and so on.

• 설비공학논문집
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• 제23권12호
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• pp.815-820
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• 2011

A scroll expander was designed for an energy converter from waste heat of IC engine coolant to useful shaft work. The scroll expander is to run in a Rankine cycle which receives heat energy transferred from engine coolant circulation cycle. The working fluid was Ethanol. For axial compliance, a back pressure chamber was provided on the rear side of the orbiting scroll. Lubrication oil was delivered by a positive displacement type oil pump driven by the shaft rotation. Performance analysis on the scroll expander showed that the expander efficiency was 63.4%. It extracts shaft power of 0.6 kW out of engine coolant waste heat of 17.5 kW, resulting in the Rankine cycle efficiency of 3.43%.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.421-426
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• 2003

Recently, mixers are being widely used in the water purification plant in order to increase the filtration efficiency. The mixer normally consists of impeller, shaft, hub, reduction gear, and the driving motor. It is one of the key design issues to confirm that the vibration caused by the rotation of the shaft should not coincide with the natural vibration frequency of the shaft itself. The vibration characteristics of the hydrofoil type mixer, which is the most widely used in real plants are evaluated through the finite element modeling and verified by experiment using the mock-up facility. The fundamental natural frequency of the mixer's shaft is found to be around 1.8 Hz which showed in good agreement with the experiment. The higher natural frequencies to the 2nd, 3rd, and 4th modes are also verified by the experiment. Thus the developed model is to be utilized for the structural design of the real mixer system.

• 한국기계가공학회지
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• 제20권5호
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• pp.8-16
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• 2021

This study develops a shaft analysis model for the optimization of the power transmission system. The finite element method was used for the shaft analysis model. The shaft and gear were assumed Timoshenko beams. Strength was evaluated according to DIN 743, and gear misalignment was calculated through ISO 6336 and the coordinate system rotation. The analysis software for a power transmission system was developed using Visual Studio 2019. The analysis results of the developed program were compared with those of commercial software (MASTA, KISSsoft, and Romax). We confirmed that the force, deformation, and safety factors at each node were the same as those of the commercial software. The absolute value of the gear misalignment of the developed program and commercial software was different. However, the gear misalignment tended to increase with increasing the displacement in the tooth width direction.

• Clinics in Shoulder and Elbow
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• 제16권1호
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• pp.27-32
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• 2013

목적: 상완골 간부 단순 골절의 수술적 치료에서 잠김 압박 금속판을 이용한 최소 침습적 금속판 골유합술의 임상적 및 방사선학적 결과를 분석하였다. 대상 및 방법: 2010년 8월부터 2011년 5월까지 상완골 간부 단순 골절 골절에 대해 최소 침습적 금속판 골 유합술을 통해 수술을 시행하고 전향적으로 12개월 이상 추시한 6례의 환자를 대상으로 하였으며, 임상적 및 방사선학적 골유합 기간 및 술 후 관절 운동 범위와 기능을 확인하였다. 결과: 임상적 및 방사선학적 평균 골유합 기간은 각각 7.2주, 8주였다. 술 후 골 정렬에서 전후상 평균 2.8도, 측면상 내반 2도의 변형을 보였다. 술 후 12개월째 견관절 운동 범위는 전방거상 167도, 외회전 50도, 내회전 수위는 흉추 11번이었고, 평균 VAS는 1.2점, KSS는 91.3점, ASES는 26.5점, UCLA 점수는 31.5점이었다. 결론: 상완골 간부 단순 골절의 수술적 치료에서 최소 침습적 금속판 골유합술은 방사선학적 및 기능적으로 우수한 결과를 보였으며 상완골 간부 단순 골절에서 고려해 볼 수 있는 유용한 치료 방법 중 하나라고 생각된다.

• 제어로봇시스템학회논문지
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• 제17권11호
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• pp.1179-1182
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• 2011

RC servos are electro-mechanical devices that respond to a control signal, which instructs them to move their output shaft to a certain position. A servo is normally plugged into a radio receiver with a three pin connector. The three wires are a power (usually 4.8V to 6.0V), a ground, and a signal wire. The signal wire carries a PWM (Pulse-Width Modulation) signal consisting of a 1-2msec pulse repeated 50 times a second. A 1.5msec pulse will tell the servo to move to its output shaft to the center position, 0 degrees. For a servo with a 180 degree of motion, a 1msec pulse will move the servo to -90 degrees, and a 2msec pulse will move the servo to +90 degrees. In order to development a humanoid robot, mechanical design, fixtures design, analysis of kinematics, implementation moving program, selection of RC servo motor and controller are required. This study was performed to experimentally compare the rotation range of RC servo motors according to change of a periods.

• 한국기계가공학회지
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• 제13권1호
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• pp.107-114
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• 2014

A friction hinge system which moves without power was designed and developed using the principle of friction force, which is caused by interference between the inner diameter of a silicon cap and the outer diameter of a cylindrical roller bearing with one-way rotation in a counterclockwise direction. The system was applied to the lid of buffet ware, which moved up by external force and moved down by gravitational force. However, design conditions which included a rotation angle of the hinge of more than 80 degrees and a closing time of more than 20 seconds were required when the lid of the buffet ware closed due to gravitational force. The design safety of the friction hinge body connected to the lid of the buffet ware from the hinge system was checked on the basis of structural, fatigue and thermal analyses. The material of the shaft, cap and flange among the hinge elements was changed to polyethylene from steel to reduce the weight of the friction hinge system. An injection molding simulation was performed and injection molds of the shaft, cap and flange were created. The weight of the hinge system was decreased from 805g to 219g.

• Structural Engineering and Mechanics
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• 제54권1호
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• pp.135-148
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• 2015

The present investigation is concerned with a study effect of magnetic field and non-homogenous on the elastic stresses in rotating orthotropic infinite circular cylinder. A certain boundary conditions closed form stress fields solutions are obtained for rotating orthotropic cylinder under initial magnetic field with constant thickness for three cases: (1) Solid cylinder, (2) Cylinder with a circular hole at the center, (3) Cylinder mounted on a circular rigid shaft. Analytical expressions for the components of the displacement and stress fields in different cases are obtained. The effect of rotation and magnetic field and non-homogeneity on the displacement and stress fields are studied. Numerical results are illustrated graphically for each case. The effects of rotating and magnetic field and non-homogeneity are discussed.

• Clinics in Shoulder and Elbow
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• 제20권2호
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• pp.95-99
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• 2017

Background: The purpose of this study was to investigate the clinical and radiological outcomes of locking plate fixation with fibular strut allograft to manage unstable osteoporotic proximal humerus fractures. Methods: We retrospectively reviewed 15 patients who underwent open reduction and locking plate fixation with fibular strut allograft for osteoporotic proximal humerus fracture between July 2011 and June 2015. For functional evaluation, we evaluated visual analogue scale (VAS) pain score, American Shoulder and Elbow Surgeons (ASES) score, University of California Los Angeles (UCLA) shoulder score, and active range of motion. For radiological evaluation, shoulder true anteroposterior (AP) and AP in $20^{\circ}$ external rotation, as well as the axillary view were taken at two weeks, six weeks, three months, six months, and one year. And the neck-shaft angle was measured on the AP view in $20^{\circ}$ external rotation view. Results: At the one-year follow-up, mean VAS pain score and all shoulder scores, including ASES score and UCLA shoulder score, exhibited satisfactory clinical outcomes. All patients obtained bone union between three and six months post-procedure. Moreover, the mean immediate postoperative neck-shaft angle was $138^{\circ}{\pm}4^{\circ}$, and at one-year follow-up, the neck shaft angle was $137^{\circ}{\pm}5^{\circ}$. There was no significant difference between the preoperative and postoperative values (p=0.105). Conclusions: For the unstable two-part and three-part osteoporotic proximal humerus fractures with medial calcar comminution, the use of fibular strut allograft with locking plate fixation was effective in maintaining the initial status of reduction and exhibiting the satisfactory functional and radiological outcomes.

• 전기학회논문지P
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• 제59권1호
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• pp.77-82
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• 2010

This study evaluated the characteristics and reliability of an auger crane with a built-in hydraulic extender. The field test of the hydraulic extender was performed with the hydraulic lines filled with hydraulic fluid and free of air. The pressure generated during the test was measured with a digital pressure gauge. The crane was considered to have undergone one cycle of the excavation process after it had performed excavation under three conditions at the same location. This process was performed three times in total. From the results of the excavation using the hydraulic extender, it was found that the maximum pressure and torque measured were 19.9 [MPa] and 895.4 [$kgf{\cdot}m$], respectively. The rotation force of the auger crane generated at this time signifies a horizontal force. If the excavation diameter of the auger crane is increased, the rotation speed is reduced causing the circumferential speed to also be reduced. The torsional shear stress of the extendable auger crane was calculated to be approximately 23.5 [MPa]. However, the rotation shaft material used for this system was carbon steel for machine structural use (SM45C). Since the minimum torsional yield stress is greater than 150 [MPa] according to KS D 3752, it means the equipment has secured a safety factor greater than 6. Therefore, it was found that when performing work using the extendable auger crane, it exhibited no problems with the safety and reliability of its shaft.