• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.357-364
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• 1999

In recently site investigations, the need for the determination of dynamic soil properties such as dynamic modules of rigidity, elasticity, dynamic poison's ratio and damping ratio etc. is increasing for the astigmatic designs of the civil structures. To obtain some of the dynamic properties, measurement of elastic waves velocity, both P and S wave, is required. Among various methods to measure elastic wave velocity such and Down Hole, Cross Hole and Refraction etc., Suspension P.S. Logging has an advantage to use for the off-shore investigation where generation of the shock wave and traveling of the wave is difficult. In suspension P.S. logging, specially designed prove equipped with source of shock wave, two 3-channel receivers, departing 1m distance, and other auxiliary facilities is inserted down in a bore hole bottom and raised in predetermined interval, usually 1m or 2m, and measurement is conducted. P.S. logging have been conducted in a off-shore construction project near InChon in the west coast for the first in the country, and form the result, potential of the liquefaction of the subsoil was evaluated and compared with the conventional method.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.588-591
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• 2009

We had experimental studies of microwave output generator. We experimented with a corrugate-shped K-band slow wave guide in the backward wave oscillator. It generated output 표 interaction between electron beam's generation and magnetic field. We estimated oscillation frequency at 24GHz by changing propagation velocity and group velocity. We identified movement by second harmonic of Cherencov interaction and slow cyclotron mode. In our study we achieved oscillation stabilization, generation of long pulse, improvement of oscillation efficiency and output.

• The Journal of Engineering Geology
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• v.13 no.3
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• pp.293-308
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• 2003

New results about the crustal structure down to a depth of 60 km beneath North Korea were obtained using the seismic tomography method. About 1013 P- and S-wave travel times from local earthquakes recorded by the Korean stations and the vicinity were used in the research. All earthquakes were relocated on the basis of an algorithm proposed in this study. Parameterization of the velocity structure is realized with a set of nodes distributed in the study volume according to the ray density. 120 nodes located at four depth levels were used to obtain the resulting P- and S-wave velocity structures. As a result, it is found that P- and S-wave velocity anomalies of the Rangnim Massif at depth of 8 km are high and low, respectively, whereas those of the Pyongnam Basin are low up to 24 km. It indicates that the Rangnim Massif contains Archean-early Lower Proterozoic Massif foldings with many faults and fractures which may be saturated with underground water and/or hot springs. On the other hand, the Pyongyang-Sariwon in the Pyongnam Basin is an intraplatform depression which was filled with sediments for the motion of the Upper Proterozoic, Silurian and Upper Paleozoic, and Lower Mesozoic origin. In particular, the high P- and S-wave velocity anomalies are observed at depth of 8, 16, and 24 km beneath Mt. Backdu, indicating that they may be the shallow conduits of the solidified magma bodies, while the low P-and S-wave velocity anomalies at depth of 38 km must be related with the magma chamber of low velocity bodies with partial melting. We also found the Moho discontinuities beneath the Origin Basin including Sari won to be about 55 km deep, whereas those of Mt. Backdu is found to be about 38 km. The high ratio of P-wave velocity/S-wave velocity at Moho suggests that there must be a partial melting body near the boundary of the crust and mantle. Consequently we may well consider Mt. Backdu as a dormant volcano which is holding the intermediate magma chamber near the Moho discontinuity. This study also brought interesting and important findings that there exist some materials with very high P- and S-wave velocity annomoalies at depth of about 40 km near Mt. Myohyang area at the edge of the Rangnim Massif shield.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.352-359
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• 2005

In this study, seismic refraction survey and MASW at dam crest and down-hole test and cross hole test in the boring holes located in dam crest through the core are performed to fin out dynamic material properties, are needed to evaluate dynamic safety of rockfill dam using dynamic analysis method. From the field test and geophysical exploration, applied such as above, p-wave and s-wave velocity profile of each layer of dam body. Dynamic material properties, such as elastic modulus, shear modulus, poissong's ration, are obtained from p-wave and s-wave velocity profile and density profile from formation density logging test.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.562-571
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• 2006

Mean shear wave velocity of the upper 30m $(V_s30)$ used as the current site classification criterion for determining seismic design ground motions in Korea was established based on the typical depth of site investigations in western US, in which the depth to bedrock is much deeper than that in Korea. In this study, to establish appropriate site classification system for site conditions of Korea, site investigations including in-situ seismic tests to determine shear wave velocity $(V_s)$ were carried out at total 72 sites in Korean peninsula. The mean $V_s's$ to the depths of 5m, 10m, 15m, 20m and 25m together with the $V_s30$ at the testing sites were determined, and the correlation between the mean $V_s$ to a depth shallower than 30m and the $V_s30$ was drawn and suggested for the efficient seismic site classification in Korea. The proposed correlation could be utilized for the seismic design in case of the $V_s$ profiles shallower than 30 m in depth. The correlation in this study, nevertheless, requires further modification by means of the accumulation of various site data in Korea.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.18-24
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• 2017

We performed seismic imaging based on relative S-wave travel times to examine S-wave velocity of upper mantle structure beneath East Asia. We used teleseismic events recorded at 129 broadband stations of the Korea Institute of Geoscience and Mineral Resources (KIGAM), Korea Meteorological Administration (KMA), and National Research Institute for Earth Science and Disaster Prevention (NIED). Relative travel time residuals were obtained by a multi-channel cross-correlation method designed to automatically determine accurate relative phase arrival times. The resulting images show high-velocity anomalies along plate boundaries around the Japanese islands region. These anomalies may indicate subducting Pacific and Philippine Sea plates. On the other hand, a low-velocity anomaly is revealed beneath east of the Korean peninsula down to around 300 km depth, which is thought to be related to the formation of the Ulleung basin and the Ulleung island. Low-velocity anomalies revealed beneath the Jeju island may imply that the formation and volcanism of the Jeju island have been caused by magmatic sources from the deep mantle.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.139-145
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• 2010

An integrity testing for stone columns was attempted using crosshole S-wave logging. The method is conceptionally quite similar to the crosshole sonic logging (CSL) for drilled piers. The critical difference in the logging is the use of S-wave rather than P-wave, which is used in CSL, because swave is the only wave sensing the stiffness of slower unbounded materials than water. An electro-mechanical source, which can generate reversed Swave signals, was utilized in the logging. The stone column was delineated using the S-wave travel times across the stone column, the S-wave velocity profile of the crushed stone($V_{cs}$-profile) and that of surrounding soil($V_s$-profile). In the calculation of $V_{cs}$-profile of the crushed stone, its friction angle and Ko (coefficient of lateral earth pressure at rest) are recommended to be used. The calculation of the column diameter is not much affected by the values of friction angle and Ko.

• Wind and Structures
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• v.35 no.6
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• pp.395-403
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• 2022

The present research is concerned with the study of Stoneley wave propagation at the interface of two dissimilar homogeneous orthotropic magneto-thermoelastic solids with fractional order theory of type GN-III with three phase-lags and combined effect of hall current and rotation. With the help of appropriate boundary conditions the secular equations of Stoneley waves are obtained in the form of determinant. The characteristics of wave such as phase velocity, attenuation coefficient and specific loss are computed numerically. The effect of rotation on the Stoneley wave's phase velocity, attenuation coefficient, specific loss, displacement components, stress components and temperature change has been depicted graphically. Some particular cases are also derived in this problem.

• Advances in aircraft and spacecraft science
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• v.7 no.3
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• pp.187-202
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• 2020

The exhaust nozzle serves back pressure of Pulse detonation combustor, so combustion chamber gets sufficient pressure for propulsion. In this context recent researches are focused on influence of nozzle effect on single cycle detonation wave propagation and propulsion performance of PDE. The effects of various nozzles like convergent-divergent nozzle, convergent nozzle, divergent nozzle and without nozzle at exit section of detonation tubes were computationally investigated to seek the desired propulsion performance. Further the effect of divergent nozzle length and half angle on detonation wave structure was analyzed. The simulations have been done using Ansys 14 Fluent platform. The LES turbulence model was used to simulate the combustion wave reacting flows in combustor with standard wall function. From these numerical simulations among four acquaint nozzles the highest thrust augmentation could be attained in divergent nozzle geometry and detonation wave propagation velocity eventually reaches to 1830 m/s, which is near about C-J velocity. Smaller the divergent nozzle half angle has a significant effect on faster detonation wave propagation.

• Geomechanics and Engineering
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• v.33 no.5
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• pp.427-437
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• 2023

The objective of this work is to study the wave propagation of an FGM plate via a new integral inverse shear model with temperature-dependent material properties. In this contribution, a new model based on a high-order theory field of displacement is included by introducing indeterminate integral variables and inverse co-tangential functions for the presentation of shear stress. The temperature-dependent properties of the FGM plate are assumed mixture of metal and ceramic, and its properties change by the power functions of the thickness of the plate. By applying Hamilton's principle, general formulas of wave propagation were obtained to plot the phase velocity curves and wave modes of the FGM plate with simply supported edges. The effects of the temperature and volume fraction by distributions on wave propagation of the FGM plate are investigated in detail. The results of the dispersion and the phase velocity curves of the propagation wave in the functionally graded plate are compared with previous research.