• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.29-35
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• 1997

This research presented a frequency analysis method to analyze NRRO in a computer hard disk drive. RRO was proved to be the harmonics of rotational frequency. The frequency components of NRRO is the subtraction of the harmonics from TIR in frequency domain, so that NRRO in time domain can be obtained by Fourier inverse transformation of NRRO in frequency domain. This method can make the experiments simple without the index signal indispensable to time domain analysis. This research also shows that NRRO is caused by the defect frequencies of ball bearing. Even though the excitation force of ball bearing is independent of the rotational speed, the amplitude of NRRO is magnified near the resonance frequencies of the spindle motor. NRRO in axial direction is almost twice bigger than that in radial direction, because the spindle motor has smaller stiffness in axial direction.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1246-1250
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• 2015

The purpose of this paper is to investigate the autonomic nervous system activity in various ambient temperature situation. To evaluate autonomic function, we use the time domain analysis of heart rate variability. Electrocardiogram was recorded to derive heart rate variability in 3 different temperature room which temperature is controlled in 18℃(low), 25℃ (mid) and 38℃(high), respectively. Totally 22 subjects were participated in the experiment. The result shows that the time-domain variables such as AVNN, SDNN, SDSD, RMSSD, NN50, pNN50, NN20 and pNN20 show the significant difference between low and high temperature (p<0.01). However, these variables has no significance (p>0.05) between mid and high except on AVNN, RMSSD and pNN20. AVNN, RMSSD shows the highest significance (p<0.001) according to the various temperature environment.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.4
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• pp.299-307
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• 2011

The offshore plants such as FPSO are subjected to combination loading of environmental conditions (swell, wave, wind and current). Therefore the fatigue damage is occurred in the operation time because the units encounter the environmental phenomena and the structural configurations are complicated. This paper is a research for frequency domain fatigue analysis of wide-band random loading focused on accuracy of fatigue damage estimation regarding the proposed methods. We selected ideal bi-modal spectrum. And comparison between time-domain fatigue analysis and frequency-domain fatigue analyses are conducted through the fatigue damage ratio. Fatigue damage ratios according to Vanmarcke's bandwidth parameter are founded for wide-band. Considering safety, we recommend that Jiao-Moan and Tovo-Benasciutti methods are optimal way at the fatigue design for wide-band response. But, it is important that these methods based on frequency-domain unstably change the accuracy according to the material parameter of S-N curve. This study will be background and guidance for the new frequency-domain fatigue analysis development in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4239-4249
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• 2011

In the country with frequent earthquakes like Japan, resistance to earthquake is assessed on the basis that Dam body's Face slab is destroyed by concentrated stress. In our country this kind of modeling and analysis is not yet definitely established. This paper performed pseudo static analysis and dynamic analysis for CFRD and evaluated reliability with the results of Shaking Table Test. The Seismic coefficient method, modified seismic coefficient method, Newmark method of Pseudo-static analysis and frequency domain response analysis, time domain history analysis of dinamic analysis were used. The analysis results were differ between analysis method, but the trends of acceleration and displacement were good agreement with the results of shaking table test.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.4
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• pp.320-327
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• 1996

This paper presents that the lossy or amplification property of the Finite Difference-Time Domain(FD-TD) method based on the leap-frog scheme is theoretically verified by using a plane wave analysis. The basic algorithm of the FD-TD method is introduced in order to help understanding the analysis procedure. Since our analysis is formulated by the Von Neumann's approach, the stability inequality is also produced as an another outcome.

• Journal of the Ergonomics Society of Korea
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• v.16 no.1
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• pp.119-126
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• 1997

Most of human factors experiments in nuclear industry domain produe lots of experimental data, thus much time is reauired to analyze the data. DAEXESS was developed to reduce resource demands necessary for the analysis work through systematic data analysis requirements and automated data processing based on computer technology. Physilolgical data, human behavior recording data, system log data and verbal protocl can be collected, synthesized and easily analyzed with with respect to time domain in DAEXESS so that analyser is able to look into inte- grated information on operating context. DAEXESS assists analyser to carry out qualitative and quantitative data analysis easily.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.25-35
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• 2023

Considering the non-linear behavior of structure and soil when evaluating a nuclear power plant's seismic safety under a beyond-design basis earthquake is essential. In order to obtain the nonlinear response of a nuclear power plant structure, a time-domain SSI analysis method that considers the nonlinearity of soil and structure and the nonlinear Soil-Structure Interaction (SSI) effect is necessary. The Boundary Reaction Method (BRM) is a time-domain SSI analysis method. The BRM can be applied effectively with a Perfectly Matched Layer (PML), which is an effective energy absorbing boundary condition. The BRM has a characteristic that the magnitude of the response in far-field soil increases as the boundary interface of the effective seismic load moves outward. In addition, the PML has poor absorption performance of low-frequency waves. For this reason, the accuracy of the low-frequency response may be degraded when analyzing the combination of the BRM and the PML. In this study, the accuracy of the analysis response was improved by adjusting the PML input parameters to improve this problem. The accuracy of the response was evaluated by using the analysis response using KIESSI-3D, a frequency domain SSI analysis program, as a reference solution. As a result of the analysis applying the optimal PML parameter, the average error rate of the acceleration response spectrum for 9 degrees of freedom of the structure was 3.40%, which was highly similar to the reference result. In addition, time-domain nonlinear SSI analysis was performed with the soil's nonlinearity to show this study's applicability. As a result of nonlinear SSI analysis, plastic deformation was concentrated in the soil around the foundation. The analysis results found that the analysis method combining BRM and PML can be effectively applied to the seismic response analysis of nuclear power plant structures.

• Journal of the Korean Institute of Gas
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• v.14 no.6
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• pp.44-50
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• 2010

Vibration responses of a centrifugal pump required dynamic analysis for seismic qualification, were calculated by using spectrum analysis, which is known to be very simple compared with time domain analysis. Modal analysis was performed and the results were utilized in the spectrum analysis. The vibration responses calculated from the spectrum analysis were more conservative than those from the time domain analysis, that is, the former can be used as safer in design process. The pump was qualified for the specified seismic service conditions as specified in IEEE 344-1987. The maximum stresses were less than allowable stress limits. Based on the analysis results, it is concluded that the pump meets all the dynamic requirements of the applicable codes, standards, and technical specification.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.2 s.25
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• pp.118-126
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• 2006

As weapon systems are becoming advanced and intelligent, they are designed to have such events like ejecting sub-munitions. So it is continually requested to measure the event time and position exactly. We can measure the event time and position by analyzing the complex signal of the instrumentation radar in the time domain and can also obtain the spin rate of the target by analyzing the complex signal in the frequency domain.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.454-460
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• 2013

We present qualitative and quantitative component analyses on compound explosives via Terahertz time-domain spectroscopy (THz-TDS) based on a combination of wavelet thresholding and wavelength selection. Despite its importance, the field of signal processing of THz signals of compound plastic explosives is relatively unexplored. In this paper, experiment results from explosives Composition B-3 and Pentolite are newly presented, suggesting a novel signal processing procedure for in situ compound explosives detection. The proposed signal processing method demonstrates effective component analysis even in noisy and humid environments, showing significant decrease in component concentration percentage error of approximately 22.7% for Composition B-3 and 48.8% for Pentolite.