• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2002년도 춘계학술대회 논문집
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• pp.44-50
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• 2002

The fast Fourier transform (FFT) is a good method to estimate spectral density, but the frequency resolution is limited to the sampling window, and thus the precise characteristics of the spectral density for short signals are not clear. To solve the limitation, a multiple band-pass filter was introduced to estimate the precise time course of the spectral density for flash visual evoked potentials (VEPs). Signals were recorded during -200 and 600 ms using balanced noncephalic electrodes, and sampled at 1 K Hz in 12 bits. With 1 Hz and 10 ms resolutions, spectral density was estimated between 10 and 100 Hz. Background powers at the alpha-and beta-bands were high over the posterior scalp, and powers around 200ms were evoked at the same bands over the same region, corresponding to P110 and N165 of VEPs. normalized's spectral density showed evoked powers around 200 ms and suppressed powers following the evoked powers over the posterior scalp. The evoked powers above the 20Hz band were not statistically significant. However, the gamma band was significantly evoked intra-individually; details in the gamma bands were varied among the subjects. Details of spectral density were complicated even for a simple task such as watching flashes; both synchronization and desynchronization occurred with different distributions and different time courses.

• 한국임상수의학회지
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• 제18권3호
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• pp.226-231
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• 2001

We investigated the effects of interactions of medetomidine and atipamezole on electroencephalography (EEG) in seven dogs. The dogs were sedated with medetomidine at dose of 30$\mu\textrm{g}$/kg, IM. Atipamezole was injected 15 min later at dose of 30$\mu\textrm{g}$/kg, IV. Recording electrode was positioned at Cz, which was applied to International 10-20 system. Heart rates, arterial blood pressures and behavioral changes were also measured. EEG was recorded in 6 stages(S1: before medetomidine injection, S2: prior to head-down movement after medetomidine injection, S3: 5 minutes after medetomidine injection, S4: 10 minutes after medetomidine injection, S5: 15 minutes after medetomidine injection, S6: prior to head-up movement after atipamezole injection), and heart rates and arterial pressures were recorded at S1, S5 and S6. All results were compared with those of control(S1). After medetomidine injection, the power spectra of EEG were gradually decreased and those of the frequency over 13 Hz were significantly decreased(p<0.05), which were still in the significantly decreased state after atipamezole injection. In the band powers (Band1; 1-2.5 Hz, Band2; 2.5-4.5 Hz, Band3; 4-8Hz, Band4; 8-13 Hz, Band5; 13-20 Hz, Band6; 20-30 Hz, Band7; 30-50 Hz, Band8; 1-50 Hz), band 1, 2, 3, 4, 8 were not significantly changed in any stages. Band 5, 6, 7 were significantly decreased in S 3, 4, 5, 6. That is, medetomidine affects the frequency band over 13 Hz on EEG, and atipamezole does not restored the decreased band powers until dogs showed head-up movement.

• 한국임상수의학회지
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• 제17권2호
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• pp.359-367
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• 2000

The aim of this study was to evaluate the effects of propofol on cortical electroencephalogram (EEG) in seven dogs. Propofol infusion was accomplished from low concentration to high concentration in series, and each concentration was infused for 20 minutes (M0: 0, M0.5: 0.5, M1.0:1.0, and M1.5: 1.5 mg/kg/min of infusion rate). EEG was recorded via needle electrode placed at Cz, which was applied to International 10-20 system. Arterial blood pressure. blood gas analysis and ECG were also measured. Hoemodynamics, Pa$CO_2$, PaO$_2$, heart rate and respiratory rate were variable, but were net significant(p>0.05). The power spectra of EEG in every concentration was compared wish those of control (MO). The powers at a1l frequencies at M1.0 and Ml.5 were decreased. Especially, the powers of the frequencies over 20 Hz were significantly decreased (p<0.O5). Powers at frequencies between 8 and 15Hz at MO.S were significantly increased (p<0.05) in response to the painful stimuli. It was inferred that they may reflect activity of the brain which is consciously processing the external Stimuli. Like the Power spectra, al1 the band powers of He EEG ($\delta$ 1-4, $\theta$4-8, $\alpha$ 8-13, $\beta$L13-21. $\beta$H 21-30, \ulcorner 30-50, and total 1-5OHz) were decreased in proportion to the increase of infusion rate at M1 .0 and M1.5. Especially, decrease of $\beta$H and ${\gamma}$ were significant(p<0.01). At M0.5, $\alpha$ band was significantly increased(p<0.05) among all the bands. Seizure activities which were concide with occurrence of spike wave were shown in all dogs at Ml .0 and M1.5.

• 대한원격탐사학회지
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• 제33권1호
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• pp.47-60
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• 2017

The permafrost active layer plays an important role in permafrost dynamics. Ecological patterns, processes, and water and ice contents in the active layer are spatially and temporally complex depending on landscape heterogeneity and local-scale variations in hydrological processes. Although there has been emerging interest in the application of optical remote sensing techniques to permafrost environments, optical sensors are significantly limited in accessing information on near surface geo-cryological conditions. The primary objective of this study was to investigate capability of L-band SAR data for monitoring spatio-temporal variability of permafrost ecosystems and underlying soil conditions. This study exploits information from different polarimetric SAR observables in relation to permafrost environmental conditions. Experimental results show that each polarimetric radar observable conveys different information on permafrost environments. In the case of the dual-pol mode, the radar observables consist of two backscattering powers and one correlation coefficient between polarimetric channels. Among them, the dual-pol scattering powers are highly sensitive to freeze/thaw transition and can discriminate grasslands or ponds in thermokarst area from other permafrost ecosystems. However, it is difficult to identify the ground conditions with dual-pol observables. Additional backscattering powers and correlation coefficients obtained from quad-pol mode help understanding seasonal variations ofradar scattering and assessing geo-cryological information on soil layers. In particular, co-pol coherences atHV-basis and circular-basis were found to be very usefultools for mapping and monitoring near surface soil properties.

• International Journal of Contents
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• 제12권3호
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• pp.12-16
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• 2016

Brain computer interfaces (BCI) usually have focused on classifying the explicitly-expressed intentions of humans. In contrast, implicit intentions should be considered to develop more intelligent systems. However, classifying implicit intention is more difficult than explicit intentions, and the difficulty severely increases for subject independent classification. In this paper, we address the subject independent classification of implicit intention based on electroencephalography (EEG) signals. Among many machine learning models, we use the support vector machine (SVM) with radial basis kernel functions to classify the EEG signals. The Fisher scores are evaluated after extracting the gamma, beta, alpha and theta band powers of the EEG signals from thirty electrodes. Since a more discriminant feature has a larger Fisher score value, the band powers of the EEG signals are presented to SVM based on the Fisher score. By training the SVM with 1-out of-9 validation, the best classification accuracy is approximately 65% with gamma and theta components.

• 한국안전학회지
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• 제28권3호
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• pp.107-113
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• 2013

Problem solving and/or decision making process usually encountered in human living consists of a sequence of human behaviors based upon his/her knowledge. Thus, Rasmussen introduced Skill-Rule-Knowledge paradigm to countermeasure human errors that can occur in Nuclear Power Plants. Unfortunately however, it was not so easy as expected since objective evidence have not been obtainable with conventional research techniques. With the help of EEG band pawer ratio techniques, this study tried to get psycho-physiological symptoms of human errors, if any, while human beings perform knowledge-based behaviors such as simple arithmetic computations with different difficulty level. A set of simulated works was carried out with a computer station. Four kinds of arithmetic computation tasks were given to 10 health male under-graduate students on different day individually, and during the experiment, EEG and ECG was measured continuously for objective psycho-physiological analysis. According to the results, ${\alpha}$/(${\alpha}+{\beta}$) as well as ${\alpha}/{\beta}$ band power ratio were sensitive to task difficulty level which consistently decreased both. However, any one of them failed to reveal the influence of tasks with different difficulty level in the aspect of task duration time. On the contrary, Heart Rate Variability was more suggestive than expected. To make a conclusion, it can be said that band power of EEG waves will be helpful in not only assessment of work difficulty level but also assessment of workers' skill development if supported by cardiac function such as HRV.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.177-180
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• 1999

A two-stage monolithic microwave integrated circuits (MMIC) broad-band power amplifier with AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) has been developed for the up-link and down-link applications for local multipoint distribution systems (LMDS) in the frequency range of 24~28㎓. The amplifier has a small signal gain of 18.6㏈ at 24.5㎓ and 16.7㏈ at 27.1㎓. It achieved output powers of 19.8㏈m with PAE of 19.8% at 24.5㎓ and 18.8㏈m at 27.1㎓.

• 한국광학회지
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• 제14권1호
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• pp.12-16
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• 2003

$0^{\circ}C$에서 5$0^{\circ}C$까지 온도를 변화시켜 가며 100 GHz의 채널 간격으로 L-band 40채널을 운용했을 때, 온도에 따른 L-band EDFA의 출력 스펙트럼 변화와 이득 변동폭을 측정하였다. 이득 포화 영역에서의 이득의 변화로 인한 출력 스펙트럼의 변화는 온도에 따른 출력 스펙트럼의 변화와 상반되는 점을 이용하여 1단과 2단 사이에 삽입한 가변 감쇄기를 조절하여 온도에 따른 이득 변동을 보상하였다. 그 결과, $0^{\circ}C$에서 최대 3 dB까지 차이를 보이던 이득 변동 폭은 가변 감쇄기를 이용한 온도 보상으로 1 dB 이내로 줄어듦을 볼 수 있었다.

• 한국통신학회논문지
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• 제34권5A호
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• pp.401-407
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• 2009

멀티 밴드 초 광대역 통신 시스템은 3.1-10.6 GHz 사이의 주파수 스펙트럼을 16개의 부 밴드로 나누어 사용하므로, 초 광대역 주파수 밴드의 특성상 각 부 밴드마다 중심 주파수의 차이가 많게는 2.65 배까지 발생할 수 있다. 송신측에서 전송한 신호의 경로에 따른 감쇄 정도는 주파수의 제곱에 비례하므로 멀티 밴드 초 광대역 통신시스템의 경우는 각 부 밴드 당 경로 감쇄 정도가 크게는 7배까지 차이가 날 수 있는 것이다. 그러므로 본 논문에서는 주파수 도약 방식의 멀티 밴드 초 광대역 통신 시스템에서 각 부 밴드의 중심 주파수의 차이로 해서 일어나는 수신 신호의 경로 감쇄 정도의 차이를 수신기의 상관 시간으로 보상하여 전체 시스템의 평균 비트 오류율을 향상시킬 수 있는 수신 방식을 제안하고, 그 성능을 나카가미 페이딩 채널 환경 하에서 분석하였다. 분석 결과 페이딩 index n이 증가할수록 제안된 수신 방식이 기존의 방식에 비해 더 큰 성능 이득을 얻음을 관찰할 수 있었다.

• ETRI Journal
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• 제29권6호
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• pp.779-784
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• 2007

In this paper, we report the experimental results of a hybrid wideband fiber amplifier. The amplifying medium is a concatenated hybrid fiber consisting of Er-doped fiber (EDF) and dispersion compensating fiber (DCF). The gain mechanisms are based on stimulated emission in the EDF and stimulated Raman scattering (SRS) in the DCF. Since we simultaneously use optical amplification by the two processes, the gain bandwidth is easily expanded over 105 nm by a two-tone pumping scheme. Using an experimental setup constructed with a hybrid structure of EDF-DCF-EDF, we analyzed the spectral behavior of amplified spontaneous emission for pumping powers. We achieved an optical gain of over 20 dB in the wavelength range from 1,500 to 1,600 nm under optimized pumping conditions to make the spectral gain shape flat.