• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.25-32
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• 2017

We present a 3D SH-wave velocity model of the crust and uppermost mantle and seismic radial anisotropy beneath East Asia. The SH-wave velocity structure model was built using Love-wave group-velocity dispersion data from earthquake data recorded at broadband seismic networks of Korea, Japan, and China. Love-wave group-velocity dispersion curves were obtained by using the multiple filtering technique in the period range of 3 to 150 s for 3,369 event-station pairs. The inverted model using these data sets provides a crust and upper mantle SH-wave velocity structure down to 100 km depth. At 10 ~ 40 km depths SH-wave velocity beneath the East Sea is higher than beneath the Japanese island region. We estimated the Moho beneath the East Sea to be between 10 ~ 20 km depth, while Moho beneath the Korean Peninsula at around 35 km based on the depth where high-velocity anomalies are detected. We estimated the lithosphere-asthenosphere boundary beneath the East Sea to be at around 50 km based on the depth where strong low-velocity anomalies are observed. Widespread low-velocity anomalies are found between 50 ~ 100 km depth in the study region. Positive radial anisotropy ($V_{SV}$ > $V _{SH}$) is observed down to 35 km depth, while negative radial anisotropy ($V_{SV}$ > $V _{SH}$) is observed for deeper depth.

• Journal of the Korean earth science society
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• v.22 no.4
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• pp.292-300
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• 2001

By using two methods we obtained plane solutions for 5 groups of earthquakes including 13 events, which occurred in the central region of South Korea after December 1997. The first method is the composite fault plane solution by P wave polarity, and the second the solution by amplitude ratio (SV/P, SH/P, SV/SH) and P and S wave polarities. The two method results show similar results. The strike of fault is in the direction of NNE-SSW and WNW-ESE with the movement of strike-slip or strike-slip including thrust component. The compressional axis of the stress field dominantly trends ENE-WSW or NE-SW. The results are almost consistent with the other main events occurred in and around the Korean Peninsula.

• Geophysics and Geophysical Exploration
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• v.21 no.1
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• pp.33-40
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• 2018

We investigate the crustal and uppermost mantle SV- and SH-wave velocity structure and radial anisotropy beneath East Asia including Korea, China and Japan. Rayleigh waves and Love waves were extracted from the seismic data recorded at broadband seismic stations in East Asia. Using the MFT (Multiple Filter Technique), we obtained group velocity dispersion curves of Rayleigh and Love waves with a period range of 3 to 200 s. We obtained 62466 Rayleigh-waves dispersion-curve measurements in vertical components and 54141 Love-waves dispersion-curve measurements in transverse components, respectively. The inverted models using these data sets provide SV- and SH-wave velocity structure of crust and uppermost mantle down to 100 km depth. In both cases of the S-wave velocity structures, strong high-velocity anomalies are observed down to 30 km depth beneath the East Sea, and deeper than 30 km depth, strong low-velocity anomalies are found beneath the Tibetan plateau. In the case of the SH-wave velocity structure, strong low-velocity anomalies are observed beneath the East Sea deeper than 30 km depth, leading to negative anisotropy. On the other hand, positive anisotropy is usually observed beneath the Tibetan plateau.

• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.165-172
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• 2023

This paper presents a novel method for modeling elastic wave propagation in long beams. The proposed method derives a solution for the transient transverse displacement of the beam's neutral axis without assuming the separation of variables (SV). By mapping the governing equation from the space domain to the frequency domain using Fourier transformation (FT), the transverse displacement function is determined as a convolution integral of external loading functions and a combination of trigonometric and Fresnel functions. This method determines the beam's response to general loading conditions as a linear combination of the analytical response of a beam subjected to an abrupt localized loading. The proposed solution method is verified through finite element analysis (FEA) and wave propagation patterns are derived for tone burst loading with specific frequency contents. The results demonstrate that the proposed solution method accurately models wave dispersion, reduces computational cost, and yields accurate results even for high-frequency loading.

• 한국지구물리탐사학회:학술대회논문집
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• 2010.10a
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• pp.27-27
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• 2010

There have been several studies about empirical relation between seismic source parameters(e.g., focal mechanisms, depths, magnitudes, etc.) and T-wave observation. In order to delineate the relation, numerical and theoretical approaches to figure out T-wave excitation mechanism are required. In an attempt to investigate source radiation and wave scattering effects in the oceanic crust on T-wave envelopes, we perform three-dimensional numerical modeling to synthesize T-wave envelopes. We first calculate seismic P- and SV-wave energy on the seafloor using the Direct Simulation Monte Carlo based on the Radiative Transfer Theory, which enables us to take into account both realistic seismic source parameters and wave scattering in heterogeneous media, and then estimate excited T-wave energy by normal mode computation. The numerical simulation has been carried out considering the following different conditions: source types (strike and normal faults), source depths (shallow and deep), and wave propagation through homogeneous and heterogeneous Earth media. From the results of numerical modeling, we confirmed that T-wave envelopes vary according to spatial seismic energy distributions on the seafloor for the various input parameters. Furthermore, the synthesized T-wave envelopes show directional patterns due to anisotropic source radiation, and the slope change of T-wave envelopes caused by focal depth. Seismic wave scattering in the oceanic crust is likely to control the shape of envelopes.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.128-135
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• 1997

The indirect boundary integral equation is formulated to analyze the behavior of a cavity in a multilayered half-plane subjected to earthquake waves. This formulation uses the fundamental solutions that are numerically calculated by the generalized transmission and reflection coefficient method. The free surface of the cavity without external excitation influences the behavior of the half-plane. Consequently this analysis adds the consideration of scattering-field into the analysis and the total motion field of the cavity is decomposed into the free-field and scattering-field motions. The free-field motion is obtained from the modification of the transmission and reflection coefficient method. The scattering-field motion is calculated is calculated by the indirect boundary value problem which has the ficticious boundaries and sources. In this study, P wave, SV wave, SH wave, and Rayleigh wave are analyzed respectively.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1563-1576
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• 2017

This paper presents a novel switching pattern current control (SP-CC) scheme, which is applied in three-phase voltage-source converters (VSCs). This scheme can select the optimal output switching pattern (SP) by referring the basic principle of space vector modulation (SVM). Moreover, SP-CC is a method without a carrier wave. Thus, the implementation process is concise and easy. When compared with the conventional hysteresis current control (C-HCC) and the space vector-based hysteresis current control (SV-HCC), the SP-CC has the performances of faster dynamic response of C-HCC and less switching number (SN) of SV-HCC. In addition, it has less harmonic contents in the three-phase current, along with a lower switching loss and a higher efficiency. Moreover, the hysteresis bandwidth and Clarke conversion are not required in the SP-CC. The effectiveness of the presented SP-CC is verified by simulation and experimental test results. In addition, the advantages of the SP-CC, when compared with the C-HCC and SV-HCC, are verified as well.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2328-2339
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• 1992

The propagation of coherent time-harmonic elastic L-and SV-waves is studied in a medium with random distribution of cylindrical inclusions. The purpose of the research is to characterize the dynamic elastic moduli and the attenuation properties of fiber-reinforced composite materials. The cylindes representing the fibers are assumed to be distributed in parallel with each other and the direction of incident waves are normal to the cylinder axes. A multiple scattering formula using the single scattering coefficients in conjunction with the Lax's quasicrystalline approximation is derived from which the dispersion relation for such medium is obtained. In order to formulate the multiple scattering interaction between cylinders, the pair correlation functions are generated by the Monte Carlo simulation technique. From the numerically evaluated complex wavenumbers, the propagation speed of the average wave, the coherent attenuation and the effective elastic moduli are presented as functions of frequency and fiber volume fraction.

• Journal of Korean Medicine for Obesity Research
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• v.23 no.1
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• pp.28-41
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• 2023

Objectives: This study was aimed to evaluate the hemodynamic feasibility using pulse parameters as a way to establish safe dose guidelines for herbal prescription containing Ephedra herb (Ephedra intermedia Schrenk & C.A.Mey) on weight loss, and to provide a foundation for developing evidence-based guidelines for clinical use. Methods: Forty-two volunteers were recruited to participate in a study examining the changes in pulse wave characteristics following the ingestion of Gambi-hwan, a herbal prescription containing ephedra, over a period of 4 weeks, and pulse wave measurements were taken before and after the administration. Pulse wave parameters were measured in this study using a 3-dimensional radial pulse tonometry device (DMP-Lifeplus). In addition, questionnaire, blood pressure, temperature, and body composition were also measured as secondary measures. Results: Fifteen minutes after administration of Gambi-hwan, the non-adverse event group (non-AE) exhibited a statistically significant increase in several power and pressure-related parameters, including h1, h5, systolic area, pulse area, and pulse width, while the AE group showed a trend of decreasing stroke volume and increasing Radial Augmentation Index (RAI), w, and w/t. After 4 weeks of administration, both groups exhibited significant changes in pulse rate, w/t, RAI, t3/t, stroke volume (SV), and stroke volume Index (SVI). Notably, there are significant differences between AE group and non-AE group in w/t, SV, and SVI. Conclusions: These findings suggest that pulse parameters may be a useful way to establish safe dosing guidelines for weight loss herbal prescription containing ephedra. Further research is needed to confirm these results and to develop evidence-based guidelines for clinical use.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.463-470
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• 1998

The boundary/finite element analysis for the seismic wave amplifications due to nonhomogeneous alluvial deposits was performed in this study. For numerical analysis, the homogeneous linear elastic soil half-space was modeled by using the 3-node isoparametric boundary elements and the inhomogeneous alluvial deposit was modeled by using the 8-node isoparametric finite elements. The two elements at interface were coupled together by the equilibrium condition of the tractions and the compatibility condition of the displacements. As a prarmetric variable, the incident angle and the dimensionsless frequency of the SH, P and SV-waves and the shear wave velocity ratio and the mass density ratio between the half-space and the alluvial deposit were selected.