• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.3 s.59
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• pp.3-16
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• 2006

• Journal of the Korean Chemical Society
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• v.62 no.5
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• pp.344-351
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• 2018

The IR spectra of gaseous phenanthrene, phenathrenols, phenanthrenyl radicals, and hydroxylphenanthrene radicals have been obtained using the BLYP/6-311++G(d,p) method. A comparison of these spectra shows that the measurements of IR spectra can be valuable to identify the reaction pathway(s) of the phenanthrene decomposition reaction by ${\cdot}OH$. We have found that the H atom abstraction reaction process can be easily identifiable from the $650-850cm^{-1}$ (CH out-of-plane bending) region and the ${\cdot}OH$ addition reaction process from the CH stretching and bending modes region of IR spectra. In addition, the calculated IR spectra of all five phenanthren-n-ols (n = 1, 2, 3, 4, 9) have also given in this work.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.241-251
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• 2007

The observed spectra from Odaesan earthquake were fitted to a point-source spectral model to evaluate the source spectrum and spatial features of the modelling error. The source spectrum was calculated by removing from the observed spectra the path and site dependent responses (Yun, 2007) that were previously revealed through an inversion process applied to a large accumulated spectral dataset. The stress drop parameter of one-corner Brune's ${\omega}^2$ source model fitted to the estimated source spectrum was well predicted by the scaling relation between magnitude and stress drop developed by Yun et al. (2006). In particular, the estimated spectrum was quite comparable to the two-corner source model that was empirically developed for recent moderate earthquakes occurring around the Korean Peninsula, which indicates that Odaesan earthquake is one of typical moderate earthquakes representative of Korean Peninsula. Other features of the observed spectra from Odaesan earthquake were also evaluated based on the commonly treated random error between the observed data and the estimated point-source spectral model. Radiation pattern of the error according to azimuth angle was found to be similar to the theoretical estimate. It was also observed that the spatial distribution of the errors was correlated with the geological map and the $Q_0$ map which are indicatives of seismic boundaries.

• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.137-147
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• 2008

Fault rupture directivity of the Odaesan earthquake, which was inferred to be the main cause of the high PGAvalue (> 0.1 g) unusually observed at the near-source region, was analyzed by using the data from the nearby (R < 100 km) dense seismic stations. The Boatwright's method (2007) was adopted for this purpose in which the azimuth and takeoff angle of the unilateral rupture directivity function could be estimated based on the relative peak ground-motions of seismic stations resulting from the nature of the rupture directivity. In this study, the approximate values of the relative peak ground-motions was derived from the difference between the log residuals of the point-source spectral model (Boore, 2003) for the main and secondary events based on the Random Vibration Theory. In this derivation, the spectral difference for a frequency range between the source corner frequencies of main and secondary events was considered to reflect only the effect of the fault directivity. The inversion result of the model parameters for the fault directivity function showed that the fault-plane of NWW-SEE direction dipping steeply to the North with high rupture velocity near upward in SE direction is responsible for the observed high level of ground-motion at the near-source region.

• The Journal of the Acoustical Society of Korea
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• v.16 no.4
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• pp.71-75
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• 1997

In this paper, some problems that occur from faulty elements in a direction finding system composed of the linear array are studied and the method which improves the performance is proposed. The fault element means the sensor that has no output or highly reduced gain than other normal sensors. In the case of the presence of faulty elements, the performance of the conventional the spatial spectrum subject to a constraint. The corrected spatial spectrum is obtained by this vector. The computer simulations have been performed to study the performance of the proposed method. We have compared the proposed method with the subaperture processing method of one of the previous works.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.71-74
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• 2006

파랑은 선박의 안전운항에 있어서 중요한 요소이다. 지금까지의 파랑관측은 부이와 같은 현장관측에 주로 의존하고 있으나, 근년 위성에 의한 리모트센싱의 기술이 발달함에 따라, 파랑계측에 분야에도 시도되고 있다. 하지만 국내에서는 SAR(합성개구레이더)의 처리 경험 자체가 부족하여 본격적인 연구개발이 시작되지 않고 있다. 본 연구에서는 SAR를 이용한 파랑계측을 하기 위한 초기단계로, 1) SAR화상에서 파랑의 영상화 메커니즘, 2) 파랑 스펙트럼 추정 기법의 소개를 하고자 한다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.198-199
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• 2003

광섬유 브래그 격자(Fiber Bragg Grating, FBG)는 좁은 선폭과 적은 삽입손실 등의 뛰어난 스펙트럼 특성을 가지고 있어, 고밀도 파장분할 다중화 방식을 이용한 광통신 시스템과 여러 종류의 광섬유센서에 응용되고 있다. 브래그 격자의 광학적 스펙트럼을 능동적으로 조절하기 위하여, 광섬유에 열이나 스트레인을 인가하거나, 음파와 빛의 결합을 이용한 방법이 제안되었으며, 특히 음향 광학 브래그 격자 변조기(Acousto-Optic Superlattice Modulator)는 종 방향 음파(Longitudinal Acoustic Wave)를 이용하여 파장과 크기의 조절이 가능한 사이드 밴드(Side Band)를 생성해 내었다. (중략)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.586-595
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• 2007

The analytic solution of wave scattering of monochromatic waves on a pile breakwater by an eigenfunction expansion method is extended to the case of directional irregular waves. The scattering wave spectrum and the force spectrum can be expressed from the reflection coefficient, transmission coefficient and the wave forces obtained from changing frequencies and incident angles in monochromatic waves. By numerical integration of 2-dimensional spectrum which is function of frequencies and incident angles, the representative values for the scattered waves and wave forces are obtained and the dependence of the transmission coefficients and wave forces on the directional distribution function, the principal wave direction, the submergence depth, and porosity is analyzed.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.49-59
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• 1993

A new signal processing technique is applied to four-cylinder spark and compression ignition engines for the diagnosis of power faults inside the cylinders. This technique utilizes two-sided directional power spectra(예S) of complex vibration signals measured from engine blocks as the patterns for engine cylinder power faults. The dPSs feature that they give not only the frequency contents but also the directivity of the engine block motion. For the automatic detection/diagnosis of cylinder power faults, pattern recognition method using multi-layer neural networks is employed. Experimental results show that the sucess rate for diagnosis of cylinder power faults using dPSs is higher than that using the conventional one-sided power spectra. The proposed technique is also tested to check the robustness to the sensor position and the engine rotational speed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.119-127
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• 1990

Wave directional spectrum estimation methods for irregular waves were considered in this study. Until now, the Longuet-Higgins Method (LHM) initiated by Longuet-Higgins et al. (1963) has been widely used, but resolutions of the estimation were found to be low. Kobune's Maximum Entropy Method (MEM) for the estimation of wave directional spectrum, bas-ed on the entropy Principle showed higher resolutions comparing with the LHM . If the wave directional spectrum is of Delta functions, the MEM is exact in its estimation. It was also found that for a unimodal spectrum, if the Mitsuyasu's spreading coefficient is above 5, the estimation resolutions were high. In bimodal spectrum, as the angle difference between the two peaks increased, the resolution improved. The energy seems to transfer to the smoother peak in the smoothing of peak's peakedness. LHM has a tendency to estimate bimodal spectrum as a unimodal spectrum ； thus, except for its computational speed, the resolution of LHM falls far below that of MEM.