• The Journal of Korean Physical Therapy
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• 제28권6호
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• pp.398-407
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• 2016

Purpose: The purpose of this study was to examine the changes in electroencephalogram (EEG) coherence and brain wave activity for first-person perspective action observation (1AO) and third-person perspective action observation (3AO) of healthy subjects. Methods: Thirty healthy subjects participated in this study. EEG was simultaneously recorded during the Relax period, the 1AO, and the 3AO, with event-related desynchronization (ERD) and coherence connectivity process calculations for brain wave (alpha, beta and mu) rhythms in relation to the baseline. Results: Participants showed increased coherence in beta wave activity in the frontal and central areas (p<0.05), during the 1AO using right-hand activity. Conversely, the coherence of the alpha wave decreased statistically significantly decreased in the frontocentral and parieto-occipital networks during the observation of the 1AO and the 3AO. The ERD values were larger than 40% for both central regions but were slightly higher for the C4 central region. The high relative power of the alpha wave during 1AO and 3AO was statistically significantly decreased in the frontal, central, parietal, and occipital regions. However, the relative power of the beta wave during 1AO and 3AO was statistically significantly increased in the parietal and occipital regions. Especially during 1AO, the relative power of the beta wave in the C3 area was statistically significantly increased (p<0.05). Conclusion: These findings suggest that 1AO and 3AO action observations are relevant to modifications of specific brain wave coherence and ERD values. EEG cortical activity during action observation may contribute to neural reorganization and to adaptive neuroplasticity in clinical intervention.

• 상하수도학회지
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• 제35권1호
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• pp.15-25
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• 2021

In this study, a method of leakage detection was proposed to locate leak position for a reservoir pipeline valve system using wavelet coherence analysis for an injected pressure wave. An unsteady flow analyzer handled nonlinear valve maneuver and corresponding experimental result were compared. Time series of pressure head were analyzed through wavelet coherence analysis both for no leak and leak conditions. The leak information can be obtained through either time domain reflectometry or the difference in wavelet coherence level, which provide predictions in terms of leak location. The reconstructed pressure signal facilitates the identification of leak presence comparing with existing wavelet coherence analysis.

• 한국광학회지
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• 제18권4호
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• pp.274-279
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• 2007

광간섭 단층촬영(OCT)용으로 원통형 압전소자(PZT)와 단일모드 광섬유를 이용한 광경로 지연기를 제작하여 정현파로 구동하고 특성을 분석하였다. 제작한 OCT 시스템은 검침단과 기준단을 대칭 구동하는 이중 광경로 지연방식을 사용하였다. 정현파 구동을 통한 PZT 광경로 지연 방식은 삼각파 구동과 비교하여 입력파형의 첨두 부분에서의 비선형현상을 제거하여 높은 반복성을 나타냄을 보였고, 삼각파 구동으로는 불가능했던 부분을 영상화 할 수 있었다.

• Journal of the Optical Society of Korea
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• 제14권1호
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• pp.49-54
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• 2010

In this study, the use of a continuous-wave (CW) supercontinuum (SC) seeded by an erbium-doped fiber's amplified spontaneous emission (ASE) for optical-coherence tomography imaging is experimentally demonstrated. It was shown, by taking an in-depth image of a human tooth sample, that due to the smooth, flat spectrum and long-term stability of the proposed CW SC, it can be readily applied to the spectral-domain optical-coherence tomography system. The relative-intensity noise level and spectral bandwidth of the CW SC are also experimentally analyzed as a function of the ASE beam power.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.18-26
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• 1996

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated by pulsating gas flow due to working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave propagation in exhaust system because of nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function, back pressure, and gradient of temperature in exhaust system.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.72-78
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• 1996

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated gyulsating gas flow due the working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function. back pressure, and gradient of temperature in exhaust system.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.77-84
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• 1998

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated by pulsating gas flow due to working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave propagation in exhaust system because of nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function, back pressure, and gradient of temperature in exhaust system.

• 한국전문물리치료학회지
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• 제15권4호
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• pp.70-79
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• 2008

The purpose of this study was to find out the effects of electroencephalograph (EEG) power and coherence on cognitive function in normal elderly, non-demented elderly with mild cognitive impairment, and demented elderly during working cognition tasks. Forty elderly women (19 demented elderly, 10 non-demented elderly with mild cognitive impairment, 11 norma1 elderly) participated in this study, All subjects performed working cognition tasks with Raven's CPM while EEG signal was recorded, EEGs were measured continuously at rest and during the working cognition task. EEG power and coherence was computed over 21 channels: right and left frontal, central, parietal, temporal and occipital region. We found that there were more correct answers among normal elderly women than in other groups Owing the working cognition task, ${\Theta}$ wave at Fp1, Fp2 and F8, a wave at Fp2, ${\beta}$ wave at Fp1, Fp2. F4 and F8 of the frontal region was increased significantly in the demented elderly group. On the other hand. ${\Theta}$ wave at Fp1, Fp2 and F7, ${\beta}$ wave at Fp1, Fp2, F3 and F7 of the frontal region was increased significantly in the group of non-demented elderly with mild cognitive impairment. In contrast. in the normal elderly group, all of the ${\Theta}$ wave and ${\beta}$ wave at Fp1, Fp2, F3, F4, F7 and F8 of the frontal region (except ${\beta}$ wave at F3) was increased significantly, These results suggest that the nerves in prefrontal and right hemisphere regions were most active in the demented elderly group during problem solving, and the nerves in the prefrontal and left hemisphere lobe were most active in the group of non-demented elderly with mild cognitive impairment. In contrast, me majority of nerves in the frontal region were active in the normal elderly group.

• 한국통신학회논문지
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• 제28권3A호
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• pp.151-156
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• 2003

Millimeter waves are potentially useful for high resolution ranging and imaging in low optical visibility conditions such as fog and smoke. Also, They can be used for wide band communications since the currently used spectrum bands are already crowded. However, it is necessary to develop a theoretical and experimental understanding of millimeter wave propagation to assess the performance of millimeter wave systems. The intensity fluctuations and mutual coherence function (MCF) describe atmospheric effects on the millimeter wave propagation. Using the quasi-optical method (QOM), a practical and efficient method is suggested to obtain MCF from the flux measurement in the antenna focal plane.

• 한국광학회지
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• 제21권5호
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• pp.206-213
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• 2010

광 간섭 단층촬영 시스템(OCT)을 위한 소형의 광섬유 도관형 주사장치인 엔도스코프(endoscope catheter)를 제작하였다. 깊이방향 주사장치인 원통형 압전소자(PZT)를 이용한 광경로 지연기는 정현파 1 kHz로 구동하여 시간영역에서 엔도스코프 OCT 영상을 구현하였다. 정현파로 구동한 광경로 지연기의 속도는 6 m/s 이고, 깊이방향 스캐닝의 데이터 획득은 3 mm 기준에서 초당 2000 라인이다. 제작한 엔도스코프로 사람의 손가락 및 귀에 대한 초당 10프레임의 OCT 영상을 성공적으로 획득하였다.