• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1055-1063
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• 2013

CTL cell that is one of the standard electromagnetic generation equipment can measure the characteristic of the electromagnetic susceptibility and the electromagnetic interference. In case of being input the same magnitude signal with the phase difference of 0o or the phase difference of 180o at two input ports of CTL cell to be the fundamental resonant frequency(TE011) of 2.20GHz, the characteristics of the electric field and the magnetic field at the uniform area were measured. And, it measured the electric field characteristic due to the variation of the input power, the test position and the input frequency under the dominant E-field and the dominant H-field of CTL cell. Using these mesuremed data, it examined the operation characteristic and the available frequency band of CTL cell.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3
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• pp.48-55
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• 2001

A novel method to reduce additive non-stationary noise is proposed. The method requires neither the information about noise nor the estimate of the noise statistics from any pause regions. The enhancement is performed on a band-by-band basis for each time frame. Based on both the decision on whether a particular band in a frame is speech or noise dominant and the masking property of the human auditory system, an appropriate amount of noise is reduced using spectral subtraction. The proposed method was tested on various noisy conditions (car noise, Fl6 noise, white Gaussian noise, pink noise, tank noise and babble noise) and on the basis of comparing segmental SNR with spectral subtraction method and visually inspecting the enhanced spectrograms and listening to the enhanced speech, the method was able to effectively reduce various noise while minimizing distortion to speech.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1997.11a
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• pp.90-93
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• 1997

외부환경의 변화에 의한 감성의 상태를 특정 자극을 인식한 후 나타나는 생리신호의 정량적인 분석기법을 개발함으로써 감성과 생리신호간의 상관관계를 찾고자 하는 연구가 절실히 요구되고 있다. 본 연구에서의 자극은 모터를 이용하는 자극기를 제작하여 부드러운 천과 거친사포를 피검자의 왼손바닥에 제시하였다. 그리고, 피검자에게 피부자극을 제시할 때 피검자가 자극의 특성을 인식하는 과정에서 발생되는 뇌파를 검출, 분석하고자 하였다. 분석방법으로서는 nonstationary한 신호분석에 유용한 특성을 가지고 있는 wavelet변환을 이용한 시간-주파수 EEG 신호의 특정범위에서의 시간-주파수 에너지성분의 변화를 관찰하였다. 그 결과 무자극시의 뇌파와 자극시으 뇌파를 비교하였을 때 부드러운 자극을 제시한 경우에는 낮은 주파수 대역에서 에너지가 우세함을 보였으며, 거친 자극에 대해서는 20-30Hz대역에서의 우세한 에너지 분포가 관찰되었다.

• Explosives and Blasting
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• v.18 no.2
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• pp.14-22
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• 2000

The estimation of proper prediction method and the alteration of transformation method of environmental regulation standard were carried out by measuring blasting noise in construction field. The correlation of scaled distance with sound pressure level were better than with sound level, but it was proved to be difficult to control blasting noise because the correlation factor was too 1ow. three methods to transform sound pressure levee to sound level were examined. The method is the transformation by correlation equation of sound pressure level and sound level which are measured at the same time, and simplified transformation of A-weighting network corresponding to dominant frequency, and the transformation of sound pressure level by FFT. There were many errors to transform. The best effective method is the transformation using correlation equation of sound pressure level and sound level which are measured at the same time.

• The Journal of Engineering Geology
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• v.8 no.3
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• pp.207-213
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• 1998

A study was conducted to determine the characteristics of acoustic emission(AE) events generated by the expansive cement induced rock fracturing. The dominant frequency and the maximum amplitude of the AE events are changed in relation to the rate of expansive pressure development in the hole. The dominant frequencies are in the range of 150∼230kHz for the small hole tests and 400∼500kHz for the large hole test. The maximum amplitudes are in the range of 0.015∼0.050cm/sec and 0.025∼0.064cm/sec, respectively. The fact that AE events of higher amplitude with higher frequency on the large hole test and lower amplitude with lower frequency on the small hole tests were detected, may strongly imply that the amount of energy consumed for a macro-crack in both tests may be similar. The expansive cement induced crack propagates stably without any distinguished event having higher amplitude and this implies that a macro-crack is a result of stable growth of micro cracks.

• Geophysics and Geophysical Exploration
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• v.16 no.4
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• pp.203-210
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• 2013

To look into site characteristics of the Hwacheon borehole seismic station, we analyzed property of earthquake and microtremor recorded on surface and borehole seismometers. Acoording to analysis result of microtremor, the surface-to-borehole energy ratio was approximately 15 times greater during the daytime than during the nighttime, and the surface-to-borehole ratios of spectral amplitudes as frequency increases. For earthquake data, amplitude spectra and dominant frequency were computed using surface and borehole data. As a result, small earthquakes with short distance recorded on surface seismometer peaked at 8 Hz, 46 Hz. This result corresponds to resonance frequencies (7.4 Hz, 46 Hz) calculated by H/V spectral ratio. We confirmed amplification effect by site characteristics of overburden. Background noise level was approximately 20,000 times smaller at borehole seismic station than surface seismic station. These results provide strong evidence for the superior recording of earthquakes using borehole seismometers instead of surface seismometers.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.347-347
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• 2011

고주파수평행평판플라즈마소스에서 전기장분포를 맥스웰방정식을 적용하여 해석하였다. 크게 두가지 요인이 전기장분포를 결정하였는데, 변위전류가 우세한 경우는 중심에 전기장이 큰 모양의 분포가 되었고, 전도전류가 주된 경우는 바깥쪽에 전기장이 센 모양을 가졌다. 본 계산에 의하면 전기장분포를 결정하는 또 다른 하나의 요인은 충돌주파수였는데, 충돌주파수에 의해서 전기장분포가 변화되는 것을 확인하였고, 전기장분포를 변화시킬 수 있는 충돌주파수조 건도 본 논문에서 제시할 예정이다.

• Tunnel and Underground Space
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• v.16 no.6 s.65
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• pp.486-494
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• 2006

The horizontal to vertical (H/V) ratio technique in spectral domain is a common useful technique to estimate empirical site transfer function. The technique, originally proposed by Nakamura, is proposed to analyse the surface waves in the micrortremor records. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that most of the stations have fairly good amplification characteristics in low frequency band. However, some of the seismic stations show one (resonant frequency specific to the site) or several local peaks of amplification factors with narrow high frequency band. Even though the site amplification characteristics are important information, we should be careful to analyse the observed ground motions from the seismic stations which have several very high amplification peaks for the deconvolution of seismic source and attenuation parameters.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.326-333
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• 2006

In this study, the vibration waveform of the single hole which is not interfered from the different blasting holes is separated, the each dominant frequency which is determinated through the Fast Fourier Transform(FFT) is measured. Also the separation waveform executed a superposition modeling which changes to delay time from 1ms to 80 ms in 1ms interval and controls the number of blasting holes from 2 holes to 15 holes in order to investigate the effect of PPV according to the duration time of the vibration and the number of blasting holes. As a result of analysis, the longer the duration time of the vibration, the longer the delay time which is not interfered from the different blasting holes and the effect regarding the number of blasting holes from inside identical delay time did not appear a lot.

• Geophysics and Geophysical Exploration
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• v.13 no.2
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• pp.144-152
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• 2010

To study the thickness variation of volcanic rocks of Jeju Island, microtremor data were recorded at eight and four sites using short-period and broadband seismometers, respectively, for 30 ~ 60 minutes with a 100 Hz sampling rate. During the daytime, these records show increased cultural noise at frequencies above 1.8 Hz. Natural noise occurs in the frequency range of 0.4 to 0.8 Hz in both daytime and nighttime data. Predominant frequencies determined by the H/V spectral-ratio method are in the range of 0.2 ~ 0.7 Hz. These frequencies decrease gradually as the central part of the Mt. Halla is approached. This may indicate that the basement is warped downward beneath the center of the island, which is consistent with previous gravimetric and magnetic models. Assuming an average shear-wave velocity of 1,800 m/s for the overburden basalts, the depths to basement are estimated to be between 640 and 2,140 m.