• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.108-119
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• 2001

The Spectral Analysis of surface Waves(SASW) Method has a great has a great potential for rapid determination of shear wave velocity profile of ground. However, it has an inherent limitation in the interpretation of test results due to the assumption that the ground is layered horizontally. The reason of the assumption is that difficulties exist in obtaining analytical solutions of wave equation when a soil system is composed of inclined soil layer. In this study, a finite-element method has been employed to assess the effects of dip angle and stiffness contrast of inclined soil layers and the testing direction on the dispersion curve. The propagation of wave front in the inclined soil layer was also investigated. The results indicated that the influence of dip angle on the dispersion curve is getting obvious as the dip angle increases and the propagation of wave front in the inclined layer also entirely different compared with the case of the horizontal layer.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.573-575
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• 2003

In satellite spectra, Though the magnitude varies with intensity of sunstroke, dip angle of land so on, the shape is less deformed with these effects. from this point of view, we have developed a spectral shape-dependent analysis utilizing a normalization procedure by the spectral integral and applied it to Landsat/TM spectra. Inevitable topographic and atmospheric effects can be suppressed. The correction algorithm is very simple and timesaving and the suppression of topographic effects is especially effective. Normalized band 4 is almost linear to NDVI values, and is available to the vegetation index.

• Journal of Astronomy and Space Sciences
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• v.30 no.2
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• pp.79-82
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• 2013

We present the Hilbert-Huang transform (HHT) analysis on the quasi-periodic modulation of SMC X-1. SMC X-1, consisting of a neutron star and a massive companion, exhibits superorbital modulation with a period varying between ~40 d and ~65 d. We applied the HHT on the light curve observed by the All-Sky Monitor onboard Rossi X-ray Timing Explorer (RXTE) to obtain the instantaneous frequency of the superorbital modulation of SMC X-1. The resultant Hilbert spectrum is consistent with the dynamic power spectrum while it shows more detailed information in both the time and frequency domains. According to the instantaneous frequency, we found a correlation between the superorbital period and the modulation amplitude. Combining the spectral observation made by the Proportional Counter Array onboard RXTE and the superorbital phase derived in the HHT, we performed a superorbital phase-resolved spectral analysis of SMC X-1. An analysis of the spectral parameters versus the orbital phase for different superorbital states revealed that the diversity of $n_H$ has an orbital dependence. Furthermore, we obtained the variation in the eclipse profiles by folding the All Sky Monitor light curve with orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip of Her X-1, can be observed only in the superorbital ascending and descending states, while the width is anti-correlated with the X-ray flux.

• Proceedings of the KSEEG Conference
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• 2002.04a
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• pp.156-158
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• 2002

Reverse-time migration has no dip limitations and one of the most promising methods to preserve true amplitudes. We applied 3-D prestack reverse time migration based on a pseudo-spectral implementation of the acoustic wave equation to the SEG/EAGE salt dome synthetic data set. We were able to illuminate sub salt reflectors of the SEG/EAGE salt model that were barely observable in the Kirchhoff migration images. Using the pseudo-spectral modeling technique, we could implement reverse-time migration within the core memory, which could be equipped to a personal computer.

• Proceedings of the KOSOMBE Conference
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• v.1990 no.05
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• pp.47-50
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• 1990

In this study, the degree of spectral transfer to lower frequency caused by accumulation of Latic acid inside the muscle is estimated the convintional dip analysis, zero-crossing method and FFT method have intrinsic errors and estimation problems in case of severe noise. The new spectral analysis method using "$2^{nd}$ order Maximum Entropy Method" was applied to estimate mean frequency and we confirmed that this new method yields fast and reliable estimation over the FFT method.

• Bulletin of the Korean Chemical Society
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• v.25 no.3
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• pp.373-376
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• 2004

A novel Er(III) complex with oxydiacetate and 1,10-phenanthroline was synthesized and its structure and luminescence properties were characterized. The complex of $[Er(ODA){\cdot}(phen){\cdot}4H_2O]^+$ crystallizes in the monoclinic space group $P2_1$/n with a = 12.216(4) ${\AA}$, b = 16.680(2) ${\AA}$, c = 12.627(3) ${\AA}$, ${\beta}=108.30(2)^{\circ}$, V = 2442.7(11) ${\AA}^3$, Z = 4 and ${\rho}=1.841 g/cm^3$. When the complex is excited at the He-Cd 325-nm line, it produces two broad bands spanning the regions 350-650 nm and 1200-1650 nm. The emission band of the complex is characterized by a series of spectral dips in the visible emission profile. The complex exhibits sensitized near- IR emission via two kinds of energy transfers from phen to Er(III): nonradiative and radiative energy transfers.

• Kyungpook Mathematical Journal
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• v.61 no.4
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• pp.831-843
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• 2021

In this paper we look at the three dimensional stagnation point flow problem over a rough rotating disk. We study the theoretical behaviour of the stagnation point flow, or forced flow, in the presence of a slip factor in which convective instability stationary modes appear. We make a numerical investigation of the effects of slip on the behaviour of the flow components of the stagnation point flow where the disk is rough. We provide, for the first time in the literature, a complete convective instability analysis and an energy analysis. Suitable similarity transformations are used to reduce the Navier-Stokes equations and the continuity equation into a system of highly non-linear coupled ordinary differential equations, and these are solved numerically subject to suitable boundary conditions using the bvp4c function of MATLAB. The convective instability analysis and the energy analysis are performed using the Chebyshev spectral method in order to obtain the neutral curves and the energy bars. We observe that the roughness of the disk has a destabilising effect on both Type-I and Type-II instability modes. The results obtained will be prominently treated as benchmarks for our future studies on stagnation flow.

• Journal of the Korean Ceramic Society
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• v.29 no.1
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• pp.48-52
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• 1992

Indium tin oxide (ITO) layers are of considerable interest on account of the combination of properties they provide high electrical conductivity, high infrared reflection with high solar energy transmission, high transmission in the visible range. We are concerned about the variation of the spectral transmittances and sheet resistances as the thickness of SiO2-ZrO2 barrier layer and ITO layers and heat treating conditions are changed. Transmittances and reflectivities were studied by measuring UV-VIS-NIR-, FT-IR spectroscopy. ITO films are crack free, homogeneous and of polycrystalline cubic structure. The microstructure of good ITO films shows a narrow grain size distribution and mean value of 100 nm. The selectivity of absorbing properties is improved by increasing the thickness of ITO films. The increase of sheet resistance of ITO films are due to the increase in the reaction between films and glass substrate.

• Journal of Astronomy and Space Sciences
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• v.38 no.2
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• pp.135-143
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• 2021

We report, for the first time, the afternoon (i.e., from noon to sunset time) observations of the northern mid-latitude E-region field-aligned irregularities (FAIs) made by the very high frequency (VHF) coherent backscatter radar operated continuously since 29 December 2009 at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude) in South Korea. We present the statistical characteristics of the mid-latitude afternoon E-region FAIs based on the continuous radar observations. Echo signal-to-noise ratio (SNR) of the afternoon E-region FAIs is found to be as high as 35 dB, mostly occurring around 100-135 km altitudes. Most spectral widths of the afternoon echoes are close to zero, indicating that the irregularities during the afternoon time are not related to turbulent plasma motions. The occurrence of afternoon E-regional FAI is observed with significant seasonal variation, with a maximum in summer and a minimum in winter. Furthermore, to investigate the afternoon E-region FAIs-Sporadic E (E_s) relationship, the FAIs have also been compared with E_s parameters based on observations made from an ionosonde located at Icheon (37.14°N, 127.54°E, 27.7°N dip latitude), which is 100 km north of Daejeon. The virtual height of E_s (h'E_s) is mainly in the height range of 105 km to 110 km, which is 5 km to 10 km greater than the bottom of the FAI. There is no relationship between the FAI SNR and the highest frequencies (f_tE_s) (or blanket frequencies (f_bE_s)). SNR of FAIs, however, is found to be related well with (f_tE_s-f_bE_s).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.418-424
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• 2014

We propose and experimentally demonstrate a photonic microwave notch filter with a negative coefficient. The negative coefficient is obtained by using cross gain modulation (XGM) in a reflective semiconductor optical amplifier (RSOA). When the RSOA is operated in saturated region, the signal carried on the pump wavelength is inversely copied to the probe wavelength by the XGM effect, showing a negative coefficient. Time delay between pump signal and probe signal is provided by single mode fiber (SMF) with wavelength dependent time delay. The proposed microwave notch filter shows notch dips of more than 35.1 dB and free spectral range (FSR) of about 380.6 MHz.