• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.272-277
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• 1997

The axial bearing using two ring type permanent magnets to support the weight of a flywheel is proposed to reduce the bearing loss in a flywheel energy storage , system. Two permanent magnet makes stable force in axial direction but unstable force in lateral direction. The lateral unstable stiffness is identified quantitatively using flux analysis, and then through the rotor dynamic analysis on a rigid flywheel system the unstable effects on the system by the stiffness is investigated.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1996.09a
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• pp.117-124
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• 1996

When navigating in or near an area of restricted visibility it is necessary to be heard the whistle bell and/or the siren of lighthouses or ships at times. Even though we can get the brief informations about the property of sound the direction and range of a sound radiator it is not easy to get the accurate informations for decision making. generally the audio frequency is known as 16-20,000Hz but the earshot is shorten and discrimination of sound is more difficult when there is some noise. The sound pressure is 60dB at the moment when human speaks 1 meter away. Usually the noise pressure in a silent room is 40dB and 60dB on the quiet street. In this study we suggest the basic algorithm to trace the direction and range of the source radiator using the signal received through not a physical sense but the microphone sensors and a series of signal of signal processing.

• Journal of the Korean Institute of Navigation
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• v.20 no.4
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• pp.71-79
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• 1996

When navigating in or near an area of restricted visibility, it is necessary to be heard the whistle, bell and/or the siren of lighthouses or ships at times. Even though we can get the brief informations about the property of sound, the direction and range of a sound radiator, it is not enough to get the accurate informations for decision making. Generally the audio frequency is known as 16~20, 000Hz, but the earshot is shorten and discrimination of sound is more difficult when there is some noise. The sound pressure is 60dB at the moment when human speaks 1 meter away. Usually the noise pressures are 40dB in a silent room and 60dB on the quiet street, respectively. It this study, the basic algorithm and a method of signal processing are suggested to trace the direction and range of the source radiator using the signals received through not a physical sense but the microphone sensors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.780-785
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• 2001

A moving-magnet type pickup actuator is proposed, which has the back-yoke to improve th sensitivity. Through the magnetic path analysis, we can find that the flux density is increased i the air gap by the pole assignment of magnet and the adding of back-yoke can reduce the flu leakage and induce 40％ up of flux density. Experimental results show that the sensitivity i improved in the tracking direction, however, the improvement doesn't occur in the focusing direction. Finally, the compensation performance is tested in HD-DVD system. And it is verifie that the actuator can compensate the disc tilt of ${\pm}$0.7$^{\circ}$.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.79-84
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• 2017

This paper outlines the Taguchi optimization methodology, which is applied to optimize cutting parameters in end milling when machining STS304 with TiAlN coated SKH59 tool under up and down end milling conditions. The end milling parameters evaluated are depth of cut, spindle speed and feed rate. An orthogonal array, signal-to-noise (S/N) ratio and analysis of variance (ANOVA) are employed to analyze the effect of these end milling parameters. The Taguchi design is an efficient and effective experimental method in which a response variable can be optimized, given various control and noise factors, using fewer resources than a factorial design. An orthogonal array of $L_9(33)$ was used. The most important input parameter for cutting force, however, is the feed rate, and depending on the cutter rotation direction. Finally, confirmation tests verified that the Taguchi design was successful in optimizing end milling parameters for cutting force.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.320.2-320
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• 2002

In high-capacity disk drives with ever-growing track density, the allowable level of position error signal (PES) is becoming smaller and smaller. A substantial portion of the PES is caused by disk vibration. This can be reduced by using a head gimbal assemblies (HGAs) that do not confine the slider movement to the vertical direction to disks, but allow movement to the radial direction of disks with respect to disk vibration. Several types of HGAs are proposed for such radial motion of the slider. (omitted)

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1185-1191
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• 2011

The kinematic characteristics of cutting device significantly affects cutting performance in 2-dimensional elliptical vibration cutting(EVC) where the cutting tool cuts workpiece, traversing a micro-scale elliptical trajectory in a trochoidal motion. In this study, kinematical characteristics of EVC device constructed with two parallel stacked piezoelectric actuators were analytically modeled and compared with the experimental results. The EVC device was subjected to step and low-frequency(0.1 Hz) sinusoidal inputs to reveal only its kinematical displacement characteristics. Hysteresis in the motion of the device was observed in the thrust direction and distinctive skew of the major axis of the elliptical trajectory of the cutting tool was also noticed. Discrepancy in the voltage-to-displacement characteristics of the piezoelectric actuators was found to largely contribute to the skew of the major axis of the elliptical trajectory of the cutting tool. Analytical kinematical model predicted the cutting direction displacement within 10 % error in magnitude with no phase error, but in estimating the thrust direction displacement, it showed a $27^{\circ}$ of phase-lag compared with the measured displacement with no magnitude error.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.465-470
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• 2007

In this paper, a two-way tuned liquid mass damper(TLMD) using a tuned liquid column damper(TLCD) and a rubber-bearing-type tuned mass damper(TMD) was manufactured for controlling two-way direction acceleration responses of a high-rise building structure. The proposed controlling device behaves as a tuned liquid column damper in one direction and as a tuned mass damper in the other direction. In this study, Performance evaluation of the downscaled model is conducted. The results show that the two-way controllability is behaved independently each other and realscale TLMD applicable to the high-rise building can be designed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.107-112
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• 2014

In this paper, we analysed a performance signal to noise ratio about pulse, integration coherent, and integration non coherent system in radar system. It compared existing with proposal method in order to estimation two target direction of arrival. Generally, radar system radiate pulse wave in order to decreasing distortion of return wave and transmission wave. We analysed the performance integration coherent and integration non coherent. Integration coherent is processing system before doing envelop detection, and integration non coherent is processing system after doing envelop detection. Through simulation, we analysed a performance signal to noise ratio to estimation two target range detection and estimated target direction of arrival. We showed that integration coherent system is the most good performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.508-513
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• 2000

Micro wave seeker detects micro wave signal reflecting from a object and modifies the angle of a antenna in the direction of a reflecting signal. Gimbal structure makes a motion in the direction of an elevation axis and an azimuth axis and change the direction of a missile toward a object. As before, Micro wave seeker is a important part of a missile. Especially, gimbal structure is designed to resist a external force generated by a strong propelling power. For that reason, it is essential to analyze a vibration feature of gimbal structure. In this paper, we analyze dynamic characteristics of a gimbal structure of a micro wave seeker. And we measure frequency response functions of a gimbal structure in order to investigate the effect of a pre-load on bearing.