• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1838-1840
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• 2005

Dielectric and conductive spect frequency spectra in a $1Hz{\sim}13MHz$ range have been measured for the composite consisting of PZT inclusions dispersed in a $LiClO_4$ doped polyethylene oxide(Li_PEO) matrix with various volume fractions. The dielectric and conductive spectra of the composites revealed the relaxations related with electrode polarization and interfacial polarization The observed spectra were reproduced using the empirical function and we could obtain vairous parameters related to electrode polarization and interfacial polarization.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.500-504
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• 1995

A neural network based upon the back propagation algorithm was designed and applied to acoustic power spectra of electrohydraulic total artificial hearts in order to diagnose mechanical failure of devices. The trained network distinguished spectra of the mechanically damaged device from those of the undamaged device with overall success rate of 63%. Moreover, the network correctly classified more than 70% of spectra in the frequency bands of 0-100 Hz and 700-950 Hz. Consequently, the neural network analysis was useful for the diagnosis of mechanical failure of a total artificial heart.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.5
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• pp.363-371
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• 2020

The parameters of the modified BM and JONSWAP spectra are estimated using spectral data set off Namhangjin, located in the east coast of Korea, collected during high wave events. The parameters of the modified BM spectrum were estimated to be 1.04 and 0.27, which were similar to the conventional values of 1.098 and 0.30, but showed significant differences in statistical terms. On the other hand, the peak enhancement factor of JONSWAP spectrum was estimated to be 1.4, which was substantially small compared to the conventional value of 3.3. The RMSE differences from the fitted results of the two spectra were small, approximately 0.2. In the frequency range greater than the peak frequency, however, the spectral energy density showed relatively mild decrease with increase of the frequency, compared to the standard forms of the modified BM and JONSWAP spectra.

• Proceedings of the Technology Innovation Conference
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• 2003.02a
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• pp.63-77
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• 2003

In this paper, we investigate the co-movements of the real GDP cycle and the telecommunications service expenditure cycle over 1980 through 2000 in Korea. We used several appropriate statistical tools to characterize and to compare the co-movements between the two aforementioned variables. The statistics presented in this paper are common, easy to Interpret and capture important visual, descriptive information and the dynamics of data that would be lost if one focused only on the unconditional correlation coefficients of de-trended data. This paper examines four possible characteristics for the co-movements of real GDP and telecommunications service expenditure in Korea. The first is that in low frequency, the cyclical movements in telecommunications service expenditure are very similar to the cyclical movements in real GDP, The second is that in the high frequency, the estimated stationary cyclical telecommunications service expenditure is not closely related to the estimated stationary cyclical real GDP. Third, according to co-spectra analysis, the strong relationships between the variables are found in the mid-term frequency and as such this empirical finding has important implications for telecommunications policy and telecommunications service implementation strategies. Finally, in the short-term period, our empirical results support telecommunications network theories such as path dependence properties, lock-in, positive feedback externality, and network externality.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.105-108
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• 1994

A comparative study was made of the valvular sounds produced by normal prosthetic valves with thrombosed prosthetic valves. Comparisons of the closing sound were made for the power frequency spectra associated with individual valves. We used periodogram approach to obtain the spectral characteristics of the valve. Spectral analysis system was tested in mock circulatory system by comparing normal valves with those produced by the same valves but having simulated thrombosis at the hinge of the valve. The heart sounds was recorded from two patients having normal mechanical valve and thrombosed mechanical valve. The estimated spectrum of the thrombosed mechanical valve displayed lower apparent peak frequency than that of the normal valve. The results showed that frequency spectra gave information pertinent to the valve malfunction. Sound spectral analysis is simple and alternative diagnostic tool for early detection of prosthetic valve mal function.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1865-1867
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• 2002

In this paper, frequency spectra of AE signals detected from respective the insulation deterioration were analysed to under ac high-voltage application using epoxy resin sample and insulation oil. Also, frequency spectra of AE signals generated from the load currents in the actual operating transformer of 500[kVA] under distribution system of 22.9[kVJ] were also analysed to distinguish the AE signals due to void discharges from the magnetic circuit noises in transformer. As the experimental results, we could distinguish the AE signals whether those signals were caused due to the void discharges or due to the magnetic circuit noises by analyzing the frequency spectrum of AE signals.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.32.1-32.1
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• 2021

We present the magnetic field strengths of CTA 102 using multi-frequency data at 2.6-343.5 GHz in order to study the physical origins of radio flares. The observations at 22 and 43 GHz were conducted using the single-dish radio telescopes of the Korean VLBI Network (KVN) from December 2012 until May 2018 (MJD 56200-58400). We used multi-frequency data obtained from the Effelsberg 100-m, OVRO 40-m, Metsähovi 14-m, IRAM 30-m, SMA, ALMA, and VLBA telescopes. During the period of the observations, two major flares (R1 and R2) are seen clearly at 15 and 37 GHz during MJD 57500-57800 and MJD 58000-58300, respectively. The source shows typical variability with time-scales ranging from 20-161 days at 15 GHz. The variability Doppler factor is in the range of 11.51-31.23. The quasi-simultaneous radio data are used to investigate the synchrotron spectrum of the source, finding that the synchrotron radiation is self-absorbed. The turnover frequency and the peak flux density of the synchrotron self-absorption (SSA) spectra are in ranges of 38.06-167.86 GHz and 1.49-10.38 Jy, respectively. From the SSA spectra, magnetic field strengths are estimated to be < 10 mG. The equipartition magnetic field strengths are larger than the SSA magnetic field strengths by a factor of > 100. This indicates that the radio flares may be related to a particle energy-dominated emission region.

• 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.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.35-42
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• 2002

Frequency responses for most of the local seismic sensors in Korea have been roughly checked by mutual comparison of Fourier spectra of seismic records from accelerometer and seismometer, both of which are installed at the same location. Especially, because the frequency content of the seismic energy is usually above 1 Hz for local earthquakes, the reliability of low frequency response could have not been evaluated. Fortunately a recent large earthquake, Ms=7.2 on 02/06/29 containing dominant low frequency energy makes it possible to check the low frequency response of the seismic sensors, especially EpiSensor and JC-V100. Considering two types of sensor pairs, (STS-2 and EpiSensor, JC-V100 and EpiSensor), the low frequency response of EpiSensor is confirmed first by comparison with STS-2 which has proved low frequency response. Second, reliable low frequency limit of instrumentally corrected seismic data from JC-V100 data is estimated to be about 0.03 Hz by comparison with EpiSensor data.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.227-234
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• 2010

The vertical response spectra using the observed ground motions from the recent more than 30 macro earthquakes were analysed and then were compared both to the seismic design response spectra (Reg Guide 1.60), applied to the domestic nuclear power plants, and to the Korean Standard Design Response Spectrum for general structures and buildings (1997). 176 vertical ground motions, without considering soil types, were used for normalization with respect to the peak acceleration value of each ground motion. The results showed that response spectrum had strong dependency on epicentral distance. The results also showed that the vertical response spectra revealed much higher values for frequency bands above 5~7 Hz than Reg. Guide (1.60). The results were also compared to the Korean Standard Response Spectrum for the 3 different soil types and showed that the vertical response spectra revealed much higher values for the frequency bands below 0.2 second (5 Hz) than the Korean Standard Response Spectrum (SD soil condition). These frequency-dependent spectral values could be related to the characteristics of the domestic crustal attenuation and the effect of each site amplification. However, through the qualitative improvements and quantitative enhancement of the observed ground motions, the conservation of vertical seismic design response spectrum should be considered more significantly for the frequency bands above 5 Hz.