• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2002.05a
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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.

• Journal of Veterinary Clinics
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• v.18 no.3
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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.

• Journal of Veterinary Clinics
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• v.17 no.2
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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.

• Korean Journal of Remote Sensing
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• v.33 no.1
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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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• v.12 no.3
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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.

• Journal of the Korean Society of Safety
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• v.28 no.3
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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.

• Proceedings of the IEEK Conference
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• 1999.11a
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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㎓.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.12-16
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• 2003

This paper presents a compensation method for a temperature-dependent gain tilt in L-band erbium-doped fiber amplifier using a voltage-controlled attenuator. The gain tilts in the L-band of 1570-1605 nm due to a temperature change have negative slopes, whereas they have positive slopes for the increasing optical input powers in a saturation region. The proposed method utilizes these opposite gain variations to compensate for the gain tilt over a wide range of temperature. While applying forty channels with a channel spacing of 100 GHz in the L-band and changing the ambient temperature from 0 to $50^{\circ}C$, the compensation method maintained the gain deviation within 1 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.401-407
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• 2009

The multi-band (MB) ultra-wideband (UWB) communication system divides its available frequency spectrum in 3.1 to 10.6GHz into 16 sub-bands, which leads to inherent disparities between carrier frequencies of each sub-band. For instance, the highest carrier frequency is 2.65 times higher than the lowest one. Since the propagation loss is proportional to the square of the transmission frequency, the propagation loss on the sub-band having the highest carrier frequency is approximately 7 times larger than that on the sub-band having the lowest carrier frequency, which results in disparities between received signal powers on each sub-band. In this paper, we propose a novel correlation scheme for frequency hopping (FH) MB UWB communications, where the correlation time is adaptively adjusted relative to the sub-band, which reduces the disparity between the received signal energies on each sub-band. Such compensation for lower received powers on sub-bands having higher carrier frequency leads to an improvement on the total average bit error rate (BER) of the entire FH MB UWB communication system. We analyze the performance of the proposed correlation scheme in Nakagami fading channels, and it is shown that the performance gain provided by the proposed correlator is more significant as the Nakagami fading index n increases (i.e., better channel conditions).

• ETRI Journal
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• v.29 no.6
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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.