• Journal of the Korea Institute of Information and Communication Engineering
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• 제6권4호
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• pp.567-573
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• 2002

In this paper, we propose a new symbol time synchronization scheme suitable for the OFDM system with an interpolator. The proposed scheme performs the following three steps. In the first step, the coarse symbol time synchronization is achieved by continuously measuring the average power of the received envelope signal. Based on this average power, the detection possibility for the symbol time synchronization is determined. It the signal is sufficient for synchronization, we next perform a relatively accurate symbol time synchronization by measuring the correlation between a short training signal and the received envelope signal. Finally, an additional frequency synchronization is performed with a long training signal to correct symbol synchronization errors caused by the phase rotation. From the simulation results, one can see that the proposed synchronization scheme provides a good synchronization performance over frequency selective channels.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국해양정보통신학회 2011년도 춘계학술대회
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• pp.718-721
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• 2011

In this paper, cross ambiguity function map is proposed to estimate the location of a unknown interferer which emits the harmful radio in the satellite communication network. To estimate the interferer, a time difference between received radio signals at earth stations and a frequency difference caused by the movement of interferers or receiving earth stations are calculated. Therefore, cross ambiguity function is used to calculate that values. The calculating process of the time and the frequency differences using cross ambiguity function is operated at every designated time then the correlation values between the time and frequency are calculated. After calcuation, the final location of the harmful interferer is estimated. From the simulation results, about 800 m distance error is occurred at 10~4 dB of $E_b/N_0$ and about 13 km distance errer is occurred at -20 dB of $E_b/N_0$.

• Journal of Korean Traditional Oncology
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• 제16권1호
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• pp.15-31
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• 2011

Objective : The study aims to investigate the effect of moxibustion treatments on autonomic nervous system function of cancer patients through the evaluation of heart rate variability (HRV) biofeedback testing. Materials and Methods : Six cancer patients from inpatient care unit of Dunsan Oriental Hospital, Daejeon University were given three moxibustion treatment sessions every other day over one week period on five Oriental Medicine meridian points CV4, CV6, CV12, KD1, and PC8. HRV biofeedback was conducted before and after each treatment sessions. Three areas of analyses were done from the test conducted; Time Domain Analysis, Frequency Domain Analysis and Autonomic Nervous System (ANS) balance analysis. Results : Time Domain Analysis has shown increased Standard Deviation of all Normal R-R Intervals (SDNN), and decreased Mean Heart Rate and Physical Stress Index (PSI) levels, with statistical significance (P<0.05). In Frequency Domain Analysis, series of moxa treatments have increased Total Power (TP), Very Low Frequency Oscillation Power (VLF), High Frequency Oscillation Power (HF), normalized HF values while decreasing Low Frequency Oscillation Power (LF), normalized LF and LF/HF ratio with statistical significance (P<0.05). The values of ANS activity, ANS balance, Stress resistance, Stress index, have also shown significant changes. For cardiac stability stroke volume power (SP) and Blood Vessel Tension (BVT) were followed, which were both increased after treatment. All changes were statistically significant (P<0.05). Conclusion : The results have shown a positive correlation between the moxibustion treatments and autonomic nervous system responses on cancer patients through the HRV biofeedback testing. This study suggests possible application of moxibustion treatments for managing ANS functions of cancer patients, although additional studies with larger population are necessary to confirm the data.

• The Journal of the Acoustical Society of Korea
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• 제38권2호
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• pp.154-159
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• 2019

When measuring the radiating noise of an underwater moving source, the range information between the acoustic source and the receiver is an important evaluation factor, and the measurement standards such as a receiver position, a moving source depth and a speed are set. Although there is a method of using the cross correlation as a method of finding the range of the underwater moving source, this method requires a time synchronization process. In this paper, we proposed the method to estimate the range by comparing the Doppler frequency difference of the theoretically calculated multipath signal with the Doppler frequency difference of the multipath signal estimated from the received signal. The proposed method does not require a separate time synchronization process. Simulations were performed to verify the performance, and the ranging error of the proposed method reduced by about 95 % than that of the conventional method.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2745-2748
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• 2003

In this paper, we implement the photoplethysmo-graphy system that have three channel pulse wave detects and one channel ECG amplifier. In order to detect the artery state, we measured the pulse waves at different positions, simultaneously. In general, arterial vascular system suffers the decrease of compliance, increase of resistance, and decrease of distensibility through aging. Therefore, we compared and analyzed variation of tile Pulse waves parameter both in time and frequency domains that is concerned with the changes of arterial characteries. And then evaluated the correlation coefficients between the parameters variation and the age group. As the result of experiment, we found that the Parameters have a significant correlation about aging.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제27권8호
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• pp.21-29
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• 2013

The functional behaviors of human standing postural control were investigated when they were exposed to long-term horizontal vibration in the sagittal plane. For complexity of human postural control, a useful alternative method that has been based on a black-box approach was taken; that is, where the feedback mechanism was lumped into a single element. A motor-driven support platform was designed as a source of vibration. The AC Servo-controlled motors produced continuous anterior/posterior (AP) motion. The data were analyzed both in the time and frequency domain. The cross-correlation and coherency functions were estimated. Subjects behaved as a non-rigid pendulum with a mass and a spring throughout the whole period of the platform motion, as consistent with the plan chosen for this study.

• The Transactions of the Korean Institute of Electrical Engineers B
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• 제52권3호
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• pp.124-132
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• 2003

The goal of this paper is to propose a virtual instrumentation system based on three dimensional current coordinates for monitoring power quality A developed system with various experimental graphic screens and numerical results is made up 586-PC and DSP(digital signal processor) board, power quality analyzing and evaluating software for windows. Power parameters are analyzed using correlation signal processing techniques based on the correlation between voltage and current waveforms. Analysis. results are visualized by 3-D current coordinates, and it Is compared and evaluated with conventional time / frequency domain. To verify the validity of the proposed system, power and harmonic parameters of single phase induction motor drives is analyzed and verified.

• Journal of Institute of Control, Robotics and Systems
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• 제19권9호
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• pp.853-859
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• 2013

The purpose of this study was to identify the correlation between electroencephalography (EEG) and strength, using grip strength. 64-channel EEG data were recorded from five healthy subjects in tasks requiring handgrip contractions of nine levels of MVC (Maximal Voluntary Contraction). We found the ERS (Event-Related Synchronization)/ERD (Event-Related Desynchronization) at the measured EEG data using STFT (Short-Time Furier Transform) and spectral power in the EEG of each frequency range displayed in the graph. In this paper, we identified that the stronger we contracted, the greater the spectral power was increased in the ${\beta}$, ${\gamma}$ wave.

• Proceedings of the KSPS conference
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• 대한음성학회 2005년도 춘계 학술대회 발표논문집
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• pp.25-28
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• 2005

The purpose of this paper is to represent values of acoustic cues for Korean oral stops in the multi-dimensional space, and to attempt to find possible relationships among acoustic cues through correlation coefficient analyses. The acoustic cues used for differentiation of 3 types of Korean stops are closure duration, voice onset time and fundamental frequency of a vowel after a stop. The values of these cues are plotted in the two and three dimensional space and see what the critical cues are for complete separation of different types of stops. Correlation coefficient analyses show that there are statistically significant relationships among acoustic cues but they are not strong enough to make a conjecture that there is a possible articulatory relationship among the mechanisms employed by the acoustic cues.

• Proceedings of the KIEE Conference
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• 대한전기학회 2002년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.190-197
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• 2002

The goal of this paper is to propose a virtual instrumentation system based on three dimensional current coordinates for monitoring power quality. A developed system with various experimental graphic screens and numerical results is made up 586-PC and DSP(digital signal processor) board, power quality analyzing and evaluating software for windows. Power parameters are analyzed using correlation signal processing techniques based on the correlation between voltage and current waveforms. Analysis results are visualized by 3-D current coordinates, and it is compared and evaluated with conventional time/frequency domain. To verify the validity of the proposed system, power and harmonic parameters of single phase induction motor drive system is analyzed and verified.