• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.1-12
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• 2007

A method to quickly estimate broadband moment magnitudes (Mwp) to warn regional and teleseismic tsunamigenic earthquakes is tested for application of the method to the different seismic observation environment. In this study, the Mwp is calculated by integrating far-field P-wave or pP-wave of vertical component of displacement seismograms in time domain from earthquakes, having magnitude greater than 5.0 and occurred in and around the Korean peninsula from 2000 to 2006. We carefully set up the size of the time window for the computations to exclude S wave phases and other phases following after the P wave phase. The P wave velocities and the densities from the averaged Korean crustal model are used in the computations. Instrumental correction was performed to remove dependency on the seismograph. The Mwp after the instrumental correction is about 0.1 greater than the Mwp before the correction. The comparison of our results to the those of foreign agencies such as JMA and Havard CMT catalogues shows a higher degree of similarity. Thus our results provide an effective tool to estimate the earthquake size, as well as to issue the necessary information to a tsunami warning system when the effective earthquake occurs around the peninsula.

• Geophysics and Geophysical Exploration
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• v.13 no.2
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• pp.137-143
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• 2010

An earthquake with local magnitude $(M_L)$ 3.7 on December 9, 2000 occurred offshore Yeongdeok area, South Korea. In case of applying Chang and Baag (2006) crustal velocity model, the epicenter is $36.4462^{\circ}N\;and\;129.9789^{\circ}E$, which belongs to the inside of the Korean Peninsula Continental Shelf. Although we use the modified model reducing crustal thickness of Chang and Baag (2006) model by 5 km considering the transition from continental crust to oceanic crust in the East Sea, the epicenter was little changed. We carried out the waveform inversion analysis to estimate focal depth and focal mechanism of this event. The focal depth is estimated to be 11 ~ 12 km. The seismic moment is estimated to be $1.0{\times}10^{15}N{\cdot}m$, and this value corresponds to the moment magnitude $(M_W)$ 3.9. The offshore Yeongdeok event including May 29, 2004 offshore Uljin one show typical thrust faulting, and the direction of P-axis is ESE-WNW. The moment magnitude estimated by the spectral analysis is 4.0, which is similar to that by the waveform inversion analysis. Average stress drop is estimated to be 3.4 MPa.

• Environmental Engineering Research
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• v.23 no.1
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• pp.76-83
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• 2018

Spatial moment analysis has been performed on the concentration of the first species in a multispecies solute transport in porous media. Finite difference numerical technique was used in obtaining the solute concentration. A constant continuous source of contaminant was injected at the inlet of the domain. Results suggest that the decaying of solute mass increases as the magnitude of mean fluid velocity increases. The dispersion coefficient is highly time dependent under decaying of solutes with a complex behavior of mixing of solutes. The solute mobility and mixing varies non-linearly with time during its initial period, while the same ceases with higher decay rates of the first species much faster.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.11a
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• pp.305-309
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• 2000

In this paper, we presents a new methodology for face recognition after analysing conventional ICA(Independent Component Analysis) based approach. In the literature we found that ICA based methods have followed the same procedure without any exception, first PCA(Principal Component Analysis) has been used for feature extraction, next ICA learning method has been applied for feature enhancement in the reduced dimension. However, it is contradiction that features are extracted using higher order moments depend on variance, the second order statistics. It is not considered that a necessary component can be located in the discarded feature space. In the new methodology, features are extracted using the magnitude of kurtosis(4-th order central moment or cumulant). This corresponds to the PCA based feature extraction using eigenvalue(2nd order central moment or variance). The synergy effect of PCA and ICA can be achieved if PCA is used for noise reduction filter. ICA methodology is analysed using SVD(Singular Value Decomposition). PCA does whitening and noise reduction. ICA performs the feature extraction. Simulation results show the effectiveness of the methodology compared to the conventional ICA approach.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.535-540
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• 2000

When the stud connection is considered as pin joint in the practical design, it is required to have high deformability. The rotational capacity as well as moment of the connection are evaluated through experimental works. Considered in the test are the reinforcement ratios of concrete member, the magnitude of axial force and connection details. It is shown that the stud connection has some quantity of moment capacity buy on the other hand it has low deformability. The strength and deformability of the connection depend on the axial force and reinforcements around the studs. The strength and ductility of the connection ate increased by using closed C-type.

• ETRI Journal
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• v.34 no.4
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• pp.572-582
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• 2012

The discrete Gaussian-Hermite moment (DGHM) is a global feature representation method that can be applied to square images. We propose a modified DGHM (MDGHM) method and an MDGHM-based scale-invariant feature transform (MDGHM-SIFT) descriptor. In the MDGHM, we devise a movable mask to represent the local features of a non-square image. The complete set of non-square image features are then represented by the summation of all MDGHMs. We also propose to apply an accumulated MDGHM using multi-order derivatives to obtain distinguishable feature information in the third stage of the SIFT. Finally, we calculate an MDGHM-based magnitude and an MDGHM-based orientation using the accumulated MDGHM. We carry out experiments using the proposed method with six kinds of deformations. The results show that the proposed method can be applied to non-square images without any image truncation and that it significantly outperforms the matching accuracy of other SIFT algorithms.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.2 s.95
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• pp.123-128
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• 2005

Forced vibration of a thin circular ring with a concentrated harmonic force is analyzed when the ring is free and has only the in-plane motion. Using the unit doublet function for external force, the governing equation is obtained and is solved by the use of Laplace transform. The exact solutions of displacement components and bending moment are obtained. In order to verify the solutions of analysis, finite element analysis is performed and the results shows good agreement. Then, frequency response curves for displacement and bending moment are obtained. In deriving the governing equations and the solutions, nondimensional parameter of the exciting frequency and the magnitude of exciting force are extracted. As the displacement components are obtained, the remaining bending strain, slope, curvature, shear force, etc. can also be derived. With the results of this work, the responses of a free ring excited on multiple points with different frequencies can also be obtained easily by superposition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.93-103
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• 1997

This study presents a way of improving the stability of fixed scroll in scroll compressors. For the scroll compressor whose fixed scroll is designed to move in the axial direction for the axial compliance, the fixed scroll is under the influence of the overturning moment produced by internal gas forces. Unless the overturning moment is properly compensated by the moments of reaction forces at the suspension of the fixed scroll to the compressor frame, the fixed scroll would exhibit wobbling motion, increasing gas leakage through the gap induced by the wobbling of the fixed scroll between the two scroll members. The conditions on which the wobbling motion can be suppressed have been found analytically; The axial position of the fixed scroll suspension should be made within a certain range. The upper limit of this range is the axial location for the o-rings which are inserted between the fixed scroll and the back pressure chamber to promote sealing for the gas in the back pressure chamber. And the lower limit is mainly determined by the magnitude of the axial sealing force. As long as the axial sealing force is not negative over all crank angles, the lower limit is not above the mid-height of the scroll wrap. Larger axial sealing force lower the lower limit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.81-88
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• 2001

This study proposed an analytical method to evaluate a local allowable wall thickness (LAWT) for locally thinned pipe subjected to internal pressure and bending moment. In this method, the stresses in the thinned region were calculated by finite element analysis and plastic collapse was applied as a failure criterion of thinned pipe. Using this method, LAWT for a simplified thinned pipe was evaluated with variation in axial extent of thinned area, and it was compared with allowable wall thickness provided by previous pipe wall thickness criteria. The results showed that the LAWT was lower, about 50%, than that calculated by construction code or ASME Code N-597, and it was higher, about 2 times, than that estimated by evaluation model based on pipe experiments. In addition, LAWT was decreased with increasing axial extent of thinned area and saturated with further increase in axial extent. And, the variation in LAWT with axial extent of thinned area depended on type of load, especially a magnitude of bending moment, considering in the evaluation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.925-934
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• 2005

The dynamic response due to the unbalance and crack and the quasi-static response due to gravity are analytically derived based on the complex transfer matrix. The additional slope is expressed as function of the bending moment at crack position based on the fracture mechanics concept, and inversely the bending moment is expressed as function of the additional slope at the crack position. At each angle step during the shaft revolution, the additional slope and bending moment are calculated by an iterative method. The transient behavior is considered by introducing Fourier series expansion concept for the additional slope. Simulation is carried out for a simple rotor similar to those available in the literature and comparison of the basic crack behavior is shown. Using the additional slope, the cracked rotor behavior is explained with the crack depth increased: the magnitude of the additional slope increases and the closed crack duration during a revolution decreases as the crack depth increases. The direction of unbalance is also shown as a factor to affect the crack breathing. Whirl orbits are shown near the sub-critical speed ranges of the rotor.