• International Journal of Precision Engineering and Manufacturing
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• v.6 no.2
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• pp.26-33
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• 2005

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effect of process variables such as gap height, relative gap width and die comer radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.12
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• pp.168-175
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• 2003

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effects of process variables such as gap height, relative gap width and die corner radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.59-63
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• 2005

Nowadays, various approaches are performed to increase the storage capacity of optical storage device. One of the promising candidates is using the high NA lens. By using high NA lens, the beam spot size can be reduced which will lead to increase the storage density. This paper proposes a double cantilever beam type bimorph PZT actuator for fine motion that can control the gap between the flexible media and optical pickup which uses high NA lens. Mathematical model is derived by using Hamilton's principle and the model is verified by finite element analysis and experiment. Position controller is designed and its performance is evaluated by experiment.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.827-828
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• 2006

This paper proposes a new method for detecting broken rotor bars in a squirrel-cage induction motor. The air-gap flux variation analysis was done using search coils inserted in stator slots when broken rotor bar occurs. An accurate modeling and analysis of air-gap flux variation in the induction motor are developed using finite-element(FE) software packages, and measurement of the flux are made using search coils. The simulation was done for the induction motor with 380 [V]. 7.5 [kW], 4 Poles, 1,760 [rpm] ratings using the commercial FE analysis tool. The simulation and experiment results can be useful for detecting the broken rotor bar of an induction motor.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.575-585
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• 2015

Magnetic field in magnetic bearings is the physical medium to realize magnetic levitation, the distribution of the magnetic field determines the operating performance of magnetic bearings. In this paper, a thin-slice Fiber Bragg Grating-Giant Magnetostrictive Material magnetic sensor used for the air gap of magnetic bearings was proposed and tested in the condition of dynamic magnetic field. The static property of the sensor was calibrated and a polynomial curve was fitted to describe the performance of the sensor. Measurement of dynamic magnetic field with different frequencies in magnetic bearings was implemented. Comparing with the finite element simulations, the results showed the DC component of the magnetic field was detected by the sensor and error was less than 5.87%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.683-688
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• 2003

Vibration characteristics of a fuel rod to be used in KALIMER(Korean Advanced LIquid MEtal Reactor) have been estimated through 3-dimensional finite element analysis and verified by experiment. The fundamental natural frequencies are found to be 6㎐ in air and 2.5㎐ in water. respectively. It has been found that in-water natural frequencies of the fuel rod are lower than in-air ones due to the added mass effect of the fluid filled inside the outer cylinder and they further decreases as the gap between the fuel rod and the outer cylinder increases, namely the added mass effect increases as the gap increases(maximum 54%). It has been also shown that the mass of the wire wrap axially coiled around the fuel rod do not affect the natural frequencies.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.214-216
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• 1999

This paper discussed an optimal designs of 2 pole fan motors in refrigerator using a Niching Algorithm. We applied a Niching method to multi-objective optimal design of air gap construct. This Niching genetic algorithm is called "Restricted Competition Selection"(RCS) that is suitable for real world problem such as shape or structural optimization of electromagnetic device. The finite element method being used for nonlinear numerical characteristic analysis is provided exact solution in the system. Through this process is reduced the cogging torque ripple in air gap.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.52-54
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• 2005

In this paper, a new approach monitoring rotor vibrations in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when rotor vibration conditions occur. An accurate modelling and analysis of air-gap flux variation in the induction motor are developed using finite-element(FE) software packages, and measuring the flux are made using search coils. In the FE analysis, the three-phase squirrel-gage induction motor with 380 (V), 5 (HP), 4 Poles, 1,742 [rpm] ratings is used. The results of FE analysis can be useful for on-line vibration monitoring of the induction motors.

• Proceedings of the KIEE Conference
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• summer
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• pp.1058-1060
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• 2004

This paper presents a characteristic analysis method for an air gap flux density of axial-flux type brushless dc (BLDC) motor. The magnetic flux density for the torque, and vertical force characteristics is calculated by using analytical method, based on the concept of magnetic charge. The calculated results by the presented method is compared with those by 3 dimensional finite element method (3D FEM). Using the presented method, the characteristics of single and double sided axial-flux type BLDC motors are investigated through distributions of air gap flux density.

• Proceedings of the KIEE Conference
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• summer
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• pp.992-994
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• 2004

In this paper, hybrid electromagnets using NdFeB permenant magnet are designed by 3-dimensional finite element analysis. Four hybrid magnets levitate the carrier of which total weight including control circuits and battery is 14[kg]. The nominal air gap length of the hybrid magnet is 3[mm]. The control circuit consists of DSP, 4-quadrant chopper, and gap sensor as feedback sensors. As a result, some experimental results for the magnetic levitation control by PI feedback control theory are shown.