• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.9
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• pp.36-42
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• 1997

Optical filters with graded index profiles are designed by applying the fourier transform to a riccati equation which governs the reflection and transmission characteristics of inhomogeneous refractive index distributions. The inhomogeneous refractive index profile of an optical filter with specified target spectrum is obtained through iterations. The spectra response of the inhomogeneous refractive index layers are analyzed by using runge-dutta numerical method to solve the differential euations of the amplitude and the phase of reflection coefficient derived from the riccati equation and the results are in good agreement with the resutls obtained by using matrix method.

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.4
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• pp.87-96
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• 1993

Spectrum analysis of surface electromyogram (FMG) signals is an effective approach to the study of localized muscular fatigue during isometric contraction. Many investigators have con firmed the frequency of the EMG signals being lowered during sustained contaction. In this study, the cyclic loading tasks were performed, and a comparison was made for the median power frequency shift pattern of the EMG signals with the sustained contraction of the same load. The median power frequency shift of the EMG signals for the cyclic loading task was found to be a part of that for the sustained contraction. Based on this result, a new muscle fatigue index was computed by normalizing the duration of the sustained contraction. A fatigue index was obtained as a function of exertion level and the work/rest schedule. With the proposed fatigue index, it is possible to evaluate or predict the degree of muscular fatigue for a physically demanding task.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.5
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• pp.22-31
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• 1997

We have measured the optical properties, thickness, and energy band gap of the P $b_{1-x}$/100/L $a_{x}$100/ $Ti_{1-}$0.25x/100/ $O_{3}$ (PLT(x)) thin film prepared by the sol-gel method with varying the La concentration, x, fyom 15 nto 33 mol%. We have obtained the values from the tranmission spectrum and employed the envelope method in anayzing the spectrum. We have also performed the simulation of the transmission spectrum on the PC (personal computer) to verify the accuracy of the values 15 to 33mol%, the refractive index (at .lambda.=632.8nm) increases from 2.39 to 2.44. The extinction coefficient does not depend on the la concentration but mainly on te wavelength, and has the values between 0.2 and 0.5 at the wavelength shorter than 330nm and between 0.001 and 0.008 at the wavelength longer than 700nm. The energy band gap of the PLT (x) thin film has been obtained on the assumption of the direct band-to-band transition. It decreases from 3.28 to 3.17eV as the La concentration increases from 15 to 33 mol%. The thickness of the PLT(x) thin film has been also obtained in high accuracy by the envelope method..

• Journal of the Ergonomics Society of Korea
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• v.20 no.3
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• pp.1-9
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• 2001

In the present study, the correlation between subjective assessment and EEG for essential odors were investigated quantitatively. EEG signals were measured from 19 electrodes according to the International 10-20 system (Fp1, Fp2, F3/4, F7/8, Fz, C3/4, Cz, P3/4, Pz, T3/4, T5/6, O1/2) from 8 healthy males subjects for four odor(Rose oil bulgarian, Lemon oil misitano, jasmin abs, Laverder oil france (KIMEX co. Ltd) conditions. The result of the subjective assessment shows the most pleasant odor for each subject. and the power spectrum of ${\alpha}/({\alpha}+{\beta})$ of EEG signals from the most pleasant odor was compared with those from the control condition, which has no odor at all. Power spectrum of ${\alpha}/({\alpha}+{\beta})$ of EEG from the most pleasant odor was increased significantly at T4, T6 compared to the control condition. This result implies that the parameter, power spectrum of ${\alpha}/({\alpha}+{\beta})$, could be an important index for signifying the levels of pleasantness for odors.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.18-24
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• 1994

We have investigated a method to measure the refractive index, coherence length, and the third order nonlinear optical susceptibility ($x^{(3)}$) of the conducting polymer film. ($x^{(3)}$) of polymer film was obtained, by comparing Maker fringe of polymer film with that of fused quartz, and by calculating the correction factor due to the linear refractive index. The linear refractive index of polymer film was determined from the envelopes of the maxima and minima in the transmission spectrum. Poly ((1,4-phenylenevinylene$)_{0.34}$-co-(2-methoxy-1,4-phen ylene vinylene$)_{0.66}$) [PP$V_{0.34}$-PMP$V_{0.66}$] thin film was prepared by spin coating method. From transmission spectrum and Maker fringe data, we found that the refractive index, coherence length, and the third order nonlinear optical susceptibility ($x^{(3)}$) of the [PP$V_{0.34}$-PMP$V_{0.66}$] are 1.786, 17.86 ${\mu}m$ and 5.8${\times}10^{-12}$esu, respectively.

• Journal of the Korean earth science society
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• v.30 no.6
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• pp.734-743
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• 2009

In order to examine how climatological condition can influence on urban scale particulate air pollutants, single and cross spectrum analysis have been performed to daily mean concentrations of particulate matters ($PM_{10}$) in Busan together with the climatological variables over the Asian dust source regions. Single power spectrum analysis of $PM_{10}$ concentrations in Busan shows that, aside from the typical and well-known periodicities, 3-4 year of peak periodicity of power spectrum density was identified. In cross spectrum analysis, this 3-4 year periodicity is found to have a strong positive correlation with the wind speed and pressure, and negative with the temperature and relative humidity, which is rather consistent with both characteristics of air mass during the Asian dust event whose periodicities have been recorded inter-annually over the Korean urban cities. Over the Asian dust source regions, $PM_{10}$ vs. precipitation shows no significant periodicity from the time series of precipitation data, but the periodicity of EDI (Effective Drought Index) shows some interannual variabilities ranging from 2 to 4 years over the various source regions, suggesting that, rather than precipitation itself, the EDI could be more closely associated with the occurrence frequency of Asian dust and interannual variability of urban particle concentrations in Korean cities.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.11
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• pp.36-42
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• 2000

We calculate the facet reflectivity as a function of the waveguide width of buried channel waveguides using the angular spectrum method and the field profiles obtained by the effective index method, the variational method and the modified variational method, respectively and discuss the results. As the waveguide width increases, the facet reflectivity of buried channel waveguides approaches to that of slab waveguides. As the waveguide width decreases, the facet reflectivity of quasi-TE mode decreases from that of slab waveguides, while that of quasi-TE mode increases from that of slab waveguides. The variation of the facet reflectivity of quasi-TE mode as a function of waveguide width is much larger than that of quasi-TM mode. When the aspect ratio is one, the difference between the facet reflectivity of quasi-TE mode and that of quasi-TM mode using the variational method and the modified variational method is negligible, while the difference between the facet reflectivity of quasi-TE mode and that of quasi-TM mode using the effective index method is large. In the case of quasi-TE mode, the facet reflectivity using the angular spectrum method and the field profiles obtained by the modified variational method could be more accurate than that obtained by the effective method. In the case of quasi-TM mode, the facet reflectivities obtained by the various methods are almost the same.

• Earthquakes and Structures
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• v.18 no.4
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• pp.507-517
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• 2020

This study aims to present new frequency-related seismic intensity parameters (SIPs) based on the Hilbert-Huang Transform (HHT) analysis. The proposed procedure is utilized for the processing of several seismic accelerograms. Thus, the entire evaluated Hilbert Spectrum (HS) of each considered seismic velocity time-history is investigated first, and then, a delimited area of the same HS around a specific frequency is explored, for the proposition of new SIPs. A first application of the suggested new parameters is to reveal the interrelation between them and the structural damage of a reinforced concrete frame structure. The index of Park and Ang describes the structural damage. The fundamental frequency of the structure is considered as the mentioned specific frequency. Two statistical methods, namely correlation analysis and multiple linear regression analysis, are used to identify the relationship between the considered SIPs and the corresponding structural damage. The results confirm that the new proposed HHT-based parameters are effective descriptors of the seismic damage potential and helpful tools for forecasting the seismic damages on buildings.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.245-256
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• 1995

Rugate filters of inhomogeneous refractive index were designed using the Fourier transform and the effect of reflectance, stop bandwidth, optical thickness, and Q function on the rugate filter was investigated. An iterative correction process using a merit function was employed to fit an initial design to the target spectrum. Three Q functions derived by Sossi, Bovard, and Fabricius, respectively, were compared in terms of the number of iteration, merit function, and optimum optical thickness. The result shows that after a number of iterations the Q functions by Bovard and Fabricius produce high rejection rugate filters closer to the target spectrum than the Sossi's Q function and the optimal optical thickness is determined by the stop-band width of the rugate filter. ilter.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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• pp.51-54
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• 1993

The purpose of this research is to investigate the relationship between the blood flow and autonomic nervous system which regulates the circulation system. After the oral glucose tolerance test(GTT) the velocity changes of the blood flow were measured from the normal, hyperglycemia and diabetic neuropathy using the laser doppler. The FFT analyses showed that the spectrums were concentrated around the particular bands(0.02-0.166Hz, 0.8-1.1Hz) for the normal, while almost uniform distribution of the spectrums was observed for the abnormal. The blood glucose affects the compliance of the blood vessels and viscosity and finally causes the resistance problem in the blood vessels. An index PG was introduced, which was determined by the ratio of the change or the integral power spectrum in the range between 0.02 and 0.166Hz to change of the blood glucose before and after GTT. The index shows 1.0. 0.3 and 0.1 for the normal, hyperglycemia and diabetic neuropathy, respectively. As a conclusion, this spectrum analysis shows the potential of checking the progress or the diabetic, also car be used to evaluate the vasomotion which are regulated by the autonomic nervous system.