• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1079-1088
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• 2003

In this paper, we propose a high-resolution time-frequency domain reflectometry technique as a methodology of detection and estimation of faults on a wire. This method adopts the time-frequency cross correlation characteristics of the observed signal in both time and frequency domains simultaneously. The accuracy of the proposed method is verified with experiments using a RG type coaxial cable and comparing it with traditional time domain as well as frequency domain reflectometry methods. It is clearly shown here that the proposed algorithm produces excellent results compared to the conventional methods for single as well as multiple fault cables.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3391-3396
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• 2012

Two-dimensional infrared (2D-IR) spectroscopy can probe the fast structural evolution of molecules under thermal equilibrium. Vibrational frequency fluctuation caused by structural evolution produced the time-dependent line shape change in 2D-IR spectrum. A variety of methods has been used to connect the evolution of 2D-IR spectrum with Frequency-Frequency Correlation Function (FFCF), which connects the experimental observables to a molecular level description. Here, a new method to extract FFCF from 2D-IR spectra is described. The experimental observable is the time-dependent frequency shift of maximum peak position in the slice spectrum of 2D-IR, which is taken along the excitation frequency axis. The direct relation between the 2D-IR peak shift and FFCF is proved analytically. Observing the 2D-IR peak shift does not need the full 2D-IR spectrum which covers 0-1 and 1-2 bands. Thus data collection time to determine FFCF can be reduced significantly, which helps the detection of transient species.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.268-275
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• 2008

In this paper, we introduce a new method for detecting and estimating faults on a power line using the time-frequency domain reflectometry system. The system rests upon time-frequency signal analysis and uses a chirp signal which is multiplied by Gaussian envelope. The chirp signal is used as a reference signal, and we can get the reflected signal from a fault on a wire. To detect and estimate faults, we analyze the reflected signal by Wigner time-frequency distribution function and normalized time-frequency cross correlation function. In this paper we design an optimal reference signal for power line and implement a system for estimating fault distance on a power line with the TFDR implemented by PXI equipments. This approach is verified by some experiments with HIV 2.25mm power lines.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.498-504
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• 2015

This paper proposed an Spread Spectrum Time Domain Reflectometry (SSTDR) using time-frequency correlation analysis in order to have more accurate fault determination and location detection than classical SSTDR despite increased signal attenuation due to the long distance to cable fault location. The proposed method was validated through comparison with classical SSTDR methods in open- and short-circuit fault detection experiments of low-voltage power cables. The experimental results showed that the proposed method can detect correlation coefficients at fault locations accurately despite reflected signal attenuation so that cable faults can be detected more accurately and clearly in comparison to existing methods.

• Journal of Oriental Neuropsychiatry
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• v.19 no.3
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• pp.143-169
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• 2008

Objective: This study was to investigate the relation of what insomnia patients' symptoms with Heart Rate Variability(HRV), Pittsburgh Sleep Quality Index (PSQI) and Insomnia Questionaire(IQ). Methods: For this study, we carried out HRV, PSQI and IQ of 43 patients with insomnia who have come to Donguei oriental hospital of Donguei university from September 2007 to May 2008. We studied the relationship HRV with PSQI and IQ. For every symptom, this study classified the patients as none-symptom, symptom groups and analyzed each group's HRV, PSQI and IQ. Result : 1. The rate of xerostomia in female group is significantly higher than male group. 2. P1 (hypnagogic time), P3(awakening time), LF has negative correlation with age. The score of PI (hypnagogic time), P3(awakening time), P4(time of recoverable sleep) in the group whose age is more than 50 are higher than the group whose age is lesser than 50. 3. The frequency of using hypnotics(P6) in the group whose duration of onset are over 1 year was significantly higher than the score in the group whose duration of onset were below 1 year. 4. The accompanied symptoms in the group who started sleep disorder after stressor are higher than the number in the group whose duration of onset were poor-defined. 5. The drinking group have lower rate of anorexia, higher score of P1 (hypnagogic time) and TP than non-drinking group. 6. The score of P-total(general quality of sleep) have negative correlation with NNSO, HF, TP and positive correlation with LF/HF. 7. The score of P1(hypnagogic time) have negative correlation with LF. 8. The score of P5a(frequency of delayed hypnagogue) have positive correlation with LF/HF. 9. The score of P5e(frequency of cough or snoring) have negative correlation with RMSSD. 10. The score of I1a(degree of onset insomnia), I1b(degree of maintenance insomnia) have negative correlation with NN50, pNN50, HF. 11. The score of I1c(degree of termination insomnia) have negative correlation with RMSSD, NN50, pNN50, HF, TP and positive correlation with MHR, LF/HF. 12.. The score of P5i(frequency of night pain), LF/HF in the group with headache are higher than the group without headache. 13. The score of P5a(frequency of delayed hypnagogue), P5c(frequency of awakening for urine of stool) in the group with xerostomia are higher than the group without xerostomia. 14. The score of P9(degree of unrecoverable sleep) and I5a(degree of onset insomnia) in the group with chest discomfort are lower than the group without chest discomfort. 15. The score of P7(frequency of drowsiness for daytime) in the group with palpitation are lower than the group without palpitation. 16. The score of P5c(frequency of awakening for urine of stool), P5f(frequency of burning sensation), P5h(frequency of nightmare), I1c(degree of termination insomnia) in the group with burning sensation of upper trunk are higher than the group without burning sensation. 17. The score of NN50, pNN50, LF, TP in the group with anorexia are lower than the group without anorexia. 18. The score of P-total(general quality of sleep), P2(duration for sleep start) in the group with constipation are higher than the group without constipation. 19. The score of P4(recoverable sleep time) in the group with depression are higher than the group without depression. 20. In the group with anxiety, the score of P1(time of hypnagogue), P5a(frequency of onset insomnia) are lower and the score of I1b(degree of maintenance insomnia), I4(objective degree of impairment by insomnia) are higher than the group without anxiety. 21. The score of NN50, pNN50, HF, TP in the group with inertia are lower than the group without inertia. 22. The accompanied symptoms haver posirive correlation with P5f(frequency of burning sensation), P5h(frequency of nightmare), P5i(frequency of night pain) and LF/HF. Conclusion: This study provides insights into the complicated relations of the pattern of sleep disorder with many symptoms such as headache, chest discomfort, depression and any others. And this study showed that autonomic nervous system have important function in the regulation of sleep.

• Korean Journal of Community Nutrition
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• v.11 no.2
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• pp.161-171
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• 2006

This study was carried out to investigate the dietary attitudes and nutritional status of preschool children in different income levels in Busan. The survey was conducted from November 1 to November 30, 2004 by questionnaires mid data analyzed by the SPSS program. The results are summarized as follows: The Kaup index of the upper income class group was higher than that of the other income classes. In the middle income class group, nutrition knowledge scores were higher than in any other income class. Sixty-four point nine percent of the upper income class children, 25.7% of the middle income class children and 15.7% of the low income class children had nutrition education experiences. Intake of protein was higher than that of the Korean recommended dietary allowances (RDAs) for children. In the upper income class group, intake of calcium was higher than in any other income class. Intakes of calcium and iron were lower than those of the RDAs in all children. Dietary attitude had positive correlation with frequency of breakfast, time for outdoor activity, and height and weight, and had negative correlation with frequency of fast food and time for watching television. Frequency of snack had positive correlation with frequency of fast food and time for watching television, but frequency of breakfast had negative correlation with those. These results indicate that nutrition education programs linking parents to children should be carried out to improve their nutritional status.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1583-1589
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• 2016

This paper proposes an improved spread spectrum time domain reflectometry (ISSTDR) using time-frequency correlation and reference signal elimination method in order to have more accurate fault determination and location detection than conventional (SSTDR) despite increased signal attenuation due to the long distance to cable fault location. The proposed method has a two-step process: the first step is to detect a peak location of the reference signal using time-frequency correlation analysis, and the second step is to detect a peak location of the correlation coefficient of the reflected signal by removing the reference signal. The proposed method was validated through comparison with existing SSTDR methods in open-and short-circuit fault detection experiments of low voltage power cables. The experimental results showed that the proposed method can detect correlation coefficients at fault locations accurately despite reflected signal attenuation so that cable faults can be detected more accurately and clearly in comparison to existing methods.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.91-94
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• 2003

In this paper, we achieve implementation of a Time-Frequency Domain Reflectometry(TFDR) system through comparatively low performance(100MS/s) PCI extensions for Instrumentation(PXI). The TFDR is the general methodology of Time Domain Reflectometry(TDR) and Frequency Domain Reflectometry(FDR). This methodology is robust in Gaussian noises, because the fixed frequency bandwidth is used. Moreover, the methodology can get more information of the fault by using the normalized time-frequency cross correlation function. The Arbitrary Waveform Generator(AWG) module generates the input signal, and the digital oscilloscope module acquires the input and reflected signals, while PXI controller module performs the control of the total PXI modules and execution of the main algorithm. The maximum range of measurement and the blind spot are calculated according ta variations of time duration and frequency bandwidth. On the basis of above calculations, the algorithm and the design of input signals used in the TFDR system are verified by real experiments. The correlation function is added to the TDR methodology for reduction of the blind spot in the TFDR system.

• ETRI Journal
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• v.35 no.5
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• pp.739-747
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• 2013

This paper investigates the multifarious nature of the long-term evolution (LTE) scheme and that of the modified LTE scheme for symbol timing synchronization (STS). This investigation allows us to propose a new replica correlation-based STS scheme to overcome the inherent weaknesses of the other two schemes. The proposed STS signal combines a gold sequence and a half sine wave in the time domain, whereas conventional STS signals specify either binary sequences or complex sequences in the time domain or in the frequency domain. In the proposed scheme, a sufficient correlation property is realized by the gold sequence, and robustness against the frequency offset (FO) is achieved through the sine wave. Compared to the existing LTE-related schemes, the proposed scheme can better achieve immunity to FO and reduction in detector complexity, as well as a low peak-to-average power ratio and a low detection error rate. Performance evaluations through analysis and simulation are provided in the paper to demonstrate these attributes.

• East Asian Economic Review
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• v.19 no.2
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• pp.189-220
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• 2015

Multi-scale representations are effective in characterising the time-frequency characteristics of financial return series. They have the capability to reveal the properties not evident with typical time domain analysis. Given the aforesaid, this study derives crucial insights from multi scale analysis to investigate the co-movements between Indian and emerging Asian equity markets using wavelet correlation and wavelet coherence measures. It is reported that the Indian equity market is strongly integrated with Asian equity markets at lower frequency scales and relatively less blended at higher frequencies. On the other hand the results from cross correlations suggest that the lead-lag relationship becomes substantial as we turn to lower frequency scales and finally, wavelet coherence demonstrates that this correlation eventually grows strong in the interim of the crises period at lower frequency scales. Overall the findings are relevant and have strong policy and practical implications.