• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.65-70
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• 2010

This paper presents experimental performance evaluation of a magnetorheological (MR) damper for integrated isolation mount for ultra-precision manufacturing system. The vibration sources of the ultra-precision manufacturing system can be classified as follows: the one is the environmental vibration from the floor and the other is the transient vibration occurred from stage moving. The transient vibration occurred from the stage moving has serious adverse effect to the process because the vibration scale is quite larger than other vibrations. Therefore in this research, a semi-active MR damper, which can control the transient vibration, is adopted. Also the stage needs to be isolated from tiny vibrations from the floor. For this purpose, a dry-frictionless MR damper is required. In order to achieve this goal, a novel type of MR damper is originally designed and manufactured in this work. Subsequently, the damping force characteristics of MR damper are evaluated by simulation and experiment. In addition, the vibration control performance of the MR damper associated with the stage mass is evaluated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1161-1167
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• 2010

This paper presents experimental performance evaluation of a magnetorheological(MR) damper for integrated isolation mount for ultra-precision manufacturing system. The vibration sources of the ultra-precision manufacturing system can be classified as follows: the one is the environmental vibration from the floor and the other is the transient vibration occurred from stage moving. The transient vibration occurred from the stage moving has serious adverse effect to the process because the vibration scale is quite larger than other vibrations. Therefore in this research, a semi-active MR damper, which can control the transient vibration, is adopted. Also the stage needs to be isolated from tiny vibrations from the floor. For this purpose, a dry-frictionless MR damper is required. In order to achieve this goal, a novel type of MR damper is originally designed and manufactured in this work. Subsequently, the damping force characteristics of MR damper are evaluated by simulation and experiment. In addition, the vibration control performance of the MR damper associated with the stage mass is evaluated.

• Journal of KSNVE
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• v.9 no.1
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• pp.49-59
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• 1999

The mechanism of Stewart platform has many advantages for kinematic analysis and control. Thus there have been many research about employing this mechanism in the new type of machine tool. Since the vibration caused during the manufacturing process has a severely adverse effect on the machining precision. it is very important to enhance the vibrational characteristics. However. it is not easy to use finite element model for the vibration analysis. That is because the vibration behaviors of the structure vary in a complicated manner according as the length of links varies. In this paper, a Stewart platform type of machine tool is modeled in finite element method and then updated by using the experimental modal data. Finally. the static and dynamic characteristics of the finite element model are predicted and then discussed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.10
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• pp.530-536
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• 1999

This paper investigates effects of segmented poles on exciting forces such as cogging torque, BEMF, phase current, torque ripple and local forces. Cogging torque, BEMF and local force are determined by FEM analysis and phase current is calculated using voltage equations after determining BEMF and phase inductance. Effective dead zones at pole separations result in wider than the physical dead zones due to leakage field during magnetization. Due to the existence of dead zones, there exist additional exciting harmonics of the cogging torque which play adverse effect on vibration and noise performance. The magnitude of BEMF is decreased and the waveforms are also distorted depending on dead zone positions. Segmented poles inevitably cause uneven magnetic field distribution at pole separations which introduces additional harmonics of exciting forces which are detrimental to structural to structural resonances. They also decrease motor efficiency by reducing effective phase BEMF.

• Journal of Preventive Medicine and Public Health
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• v.41 no.5
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• pp.307-314
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• 2008

Objectives : We conducted an epidemiologic survey to evaluate the effect of the aircraft noise exposure on the health of the residents near the military airbases in Pyeongtaek City. Methods : The evaluation of environmental noise level, questionnaire survey, and health examination were performed for 917 residents. The study population consisted of four groups: subjects who lived in the village close to the fighter airbase (high exposure), subjects who lived along the course of fighters (intermediate exposure), and subjects near a helicopter airbase, and the control group. Results : The prevalence of the aircraft noise related accident and irritable bowel syndrome in the exposure groups were higher than that of the control group. The risks of noise induced hearing loss, hypertension and diabetes mellitus were higher in the exposed groups than in the control group. The prevalence of anxiety disorder and primary insomnia were higher in the exposed groups than in the control group. Prevalence odd ratios of the risk for primary insomnia after adjusting age, sex, agricultural noise, and occupation were 4.03 [95% confidence interval (95% Cl) 1.56-10.47] for the subject near the helicopter airbase, 1.23 (95% Cl 0.40-3.76) for those intermediately exposed to fighter noise, and 4.99 (95% Cl 2.14-11.64) for those highly exposed to fighter noise. Conclusions : The results of the present study suggest that the aircraft noise may have adverse effects on hearing function, cardiovascular health and mental health. Therefore, it seems to be needed to take proper measures including the control of the aircraft noise and the management of the exposed people's health.

• Structural Engineering and Mechanics
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• v.23 no.4
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• pp.409-430
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• 2006

The aim of this study is to investigate the reliability of strong motion records processed by causal and acausal Butterworth filters in comparison to the results obtained from a synthetic accelerogram. For this purpose, the fault parallel component of the Bolu record of the Duzce earthquake is modeled with a sum of exponentially damped sinusoidal components. Noise-free velocities and displacements are then obtained by analytically integrating the synthetic acceleration model. The analytical velocity and displacement signals are used as a standard with which to judge the validity of the signals obtained by filtering with causal and acausal filters and numerically integrating the acceleration model. The results show that the acausal filters are clearly preferable to the causal filters due to the fact that the response spectra obtained from the acausal filters match the spectra obtained from the simulated accelerogram better than that obtained by causal filters. The response spectra are independent from the order of the filters and from the method of integration (whether analytical integration after a spline fit to the synthetic accelerogram or the trapezoidal rule). The response spectra are sensitive to the chosen corner frequency of both the causal and the acausal filters and also to the inclusion of the pads. Accurate prediction of the static residual displacement (SRD) is very important for structures traversing faults in the near-fault regions. The greatest adverse effect of the high pass filters is their removal of the SRD. However, the noise-free displacements obtained by double integrating the synthetic accelerogram analytically preserve the SRD. It is thus apparent that conventional high pass filters should not be used for processing near-fault strong-motion records although they can be reliably used for far-fault records if applied acausally. The ground motion parameters such as ARIAS intensity, HUSID plots, Housner spectral intensity and the duration of strong-motion are found to be insensitive to the causality of filters.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.2 s.302
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• pp.121-130
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• 2005

In this paper, we propose a feature extraction method for iris recognition using wavelet transforms. The wavelet transform is fast and has a good localization characteristic. In particular, the low frequency band can be used as an effective feature vector. In iris recognition, the noise caused by eyelid the eyebrow, glint, etc may be included in iris. The iris pattern is distorted by noises by itself, and a feature extraction algorithm based on filter such as Wavelets, Gabor transform spreads noises into whole iris region. Namely, such noises degrade the performance of iris recognition systems a major problem. This kind of noise has adverse effect on performance. In order to solve these problems, we propose to divide the iris image into a number of sub-region and apply the wavelet transform to each sub-region. Experimental results show that the performance of proposed method is comparable to existing methods using Gabor transform and region division noticeably improves recognition performance. However, it is noted that the processing time of the wavelet transform is much faster than that of the existing methods.

• Journal of KSNVE
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• v.7 no.4
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• pp.655-661
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• 1997

Base-isolation of a primary structure generally decrete the seismic response of its own and the secondary structure. It may cause an adverse effect on the seismic response of secondary system when the system is submerged and subject to a considerable hydrodynamic effect. In this paper, it is shown how, and how much, the base isolation of the primary structure can affect the secondary system response in extreme cases through dynamic analysis of a simplified coupled model for a submerged secondary system and a base-isolated primary structure. As an aseismatic design approach to reduce the response of the submerged system, optimization of the fluid gap, which controls the hydrodynamic mass effect, is performed. As an alternative approach in case where the control of fluid gap is unrealistic, application of base isolation to the submerged system is suggested. Effectiveness of various combinations of the primary base and secondary base isolations are compared.

• The Transactions of the Korea Information Processing Society
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• v.7 no.7
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• pp.2179-2187
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• 2000

This paper provides a heuristic analysis technique which determines an optimal number of V\ulcorner/V\ulcorner pads meeting allowable Simultaneous Switching Noise(SN) budget, early in the design phase. Until now, in determining the number of V\ulcorner/V\ulcorner pads, designers had to simulate packaging models case by case in the design phase or roughly allocate the power/ground pins in an inaccurate way according to typical design rules. However, due to the high density and frequency trends of IC technologies, the V\ulcorner/V\ulcorner pads allocation method can affect an adverse effect on IC operations, which requires more accurate and efficient methods be devised. Thus, this paper proposes an analytic V\ulcorner/V\ulcorner pads calculation method that gives a practical help for packaging designs early in the design phase. The proposed method is applied to a design example of a 1/8x208 pin plastic quad flat package (PQFP) and the results are verified through simulation using HSPICE.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.7
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• pp.15-23
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• 1999

With a remarkable expansion of communication industry, a pager or a cellular phone becomes a necessary communication device in modern society. However, a paging signal by a buzzer is often acted as an unpleasant noise in some places, thus necessitating a paging signal by a vibration motor. In this paper, a simpler type of a vibration motor, a coreless permanent magnet(PM) DC motor, is considered to substitute for the conventional vibration motors. Using an analytical method, electromagnetic field and operating torque were calculated for the given inner and outer PM type motors, and the results were confirmed by FEM analysis. As design parameters, number of PM poles, PM radial thickness, coil arc angle and number of winding stacks were chosen for sensitivity analysis. It shows that coil arc angle is the most important design parameter to increase the motor performance, without giving an adverse effect on motor weight, size and manufacturing cost. Based on the analysis of the outer PM type motor, an outer square PM type motor is proposed as the final design. Compared to the outer PM type, outer square type provides more flexibility to attach to the small size cellular phones. With the optimum design of square outer PM DC motor, it can successfully substitute the conventional types with less expensive manufacturing cost. better performance and smaller necessary space.