• Journal of the Korean Society for Railway
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• v.12 no.3
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• pp.357-363
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• 2009

In this paper, field measurements in the subway tunnel and adjacent building were performed to predict the pound vibration level induced by urban rapid transit (subway) in Seoul, Korea. From the results of the measurements, the measured ground vibration level induced by subway in Seoul is smaller than the empirical formula of New York, but it is bigger than the empirical formula of Tokyo which has been commonly used in Korea. We suggested the empirical formula for prediction of ground vibration level induced by subway in Seoul considering on the wave propagation path for soils or rocks, respectively.

• Proceedings of the International Union of Geodesy And Geophysics Korea Journal of Geophysical Research Conference
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• 2003.05a
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• pp.18-18
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• 2003

Three-dimensional finite-difference simulation of earthquake ground motion is performed using a locally variable time-step (LVTS) scheme matching with discontinuous grids. Discontinuous grids in three directions and extension of the discontinuous grids' boundary to the free-surface in the LVTS scheme minimize the cost of both the computational memory and the CPU time for models like the localized sedimentary basin. A simplified model of sedimentary basin is dealt to show the feasibility and efficiency of the LVTS scheme. The basin parameters are examined to understand the main characteristics on ground-motion response in the basin. The results show that the seismic energy is concentrated on a marginal area of the basin far from the source. This focusing effect is mainly due to the constructive interference of the direct S-wave with the basin-edge induced surface waves. The ground-motion amplification over the deepest part of the basin is relatively lower than that above the shallow basin edge. Therefore the ground-motion amplification may be more related to the source azimuth or the direction of the incident waves into the basin rather than the depth of it.

• ETRI Journal
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• v.35 no.5
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• pp.775-785
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• 2013

Because of their exclusive features, millimeter wave directive mesh networks can be considered for small cell backhaul support in urban environments. For this purpose, a network of closely spaced stations has been considered with very directive line-of-sight links operating in the 60-GHz band. An attempt is made to evaluate channel response and interference behavior in such a network, taking into account the effect of building blockage. A simple grid of building blocks is considered as the propagation environment, and wave propagation is simulated using 2.5-dimensional (2.5D) ray tracing (2D with ground effect) to calculate the received signal at different nodes in the network. The results are compared with free space predictions and used to evaluate interference at all nodes in the channel and describe certain characteristics of links, such as the delay profile and the correlation length.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1667-1669
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• 2001

The clack of Insulator, which results from internal or external surges such as electrical, mechanical, and thermal stress, might cause ground fault and a power failure without proper repairs. In order to minimize losses caused by a short-term or long-term power failure, it is necessary to detect the deteriorated insulator as early as possible. To do so, we will develop a new device, which can detect and trace an deteriorated insulator by monitoring its physical change the variation of frequency spectrum. This device will do so by finding a Periodic wave sharp (120 Hz), a peculiar wave generated by defused electricity.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.123-130
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• 2002

The ground-borne vibration from pile driving is causing many public discontents. However, because of the fact that the characteristics of wave propagation and attenuation are not well understood, systematic and effective vibration reduction measures can not be taken. This paper attempts to study the propagation of stress waves induced by the pile driving. To simulate the wave propagation in a semi-infinite domain, the so-called absorbing boundaries are incorporated in the finite element method and a series of numerical simulations is performed. Numerical results show that the surface displacement and velocity increase first and then decrease as the pile penetration depth becomes larges.

• Journal of Korean Society of Steel Construction
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• v.8 no.3 s.28
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• pp.97-105
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• 1996

A Stochastic line source model is developed to simulate the seismic wave field generated during the rupture propagation process along a fault plane of which length is much larger than its width. The fault plane is assumed to consist of randomly distributed slip zones and barriers and each slip zone is modeled as a point source. By combining the newly developed source model with wave propagation analysis method in a layered 3-D visco-elastic half space, synthetic seismograms are obtained. The calculated accelerograms due to vertical dip slip and strike slip line sources are presented.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.31-36
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• 1998

By using wind vectors observed by NSCAT and significant wave heights observed by TOPEX/POSEIDON and ERS-2 altimeters, one-dimensional fetch growth of wind waves Is investigated under conditions of strong wind and high waves of the East Asian winter monsoon. The evolution of fetch-limited wind waves can be observed by the altimeters along the ground tracks. The fetch is estimated by using vector wind field observed by NSCAT. The derived growth characteristics of wind waves are compared with empirical relationships between the non-dimensional fetch and significant wave height proposed by previous studies. Good agreement with the empirical fetch graph formula normalized by the friction velocity is discemible, while the formulas normalized by the wind speed at a height of 10 m tend to underestimate the wave height under such severe conditions of high wind and very long fetch.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.455-461
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• 2009

In a scanning electron microscopy, image distortion is a critical issue and it is needed to be eliminated by some kinds of schemes. In this work, scanning frequency and scanning wave form are adjusted to have an improved image. The relationship between scan coil and its driver is investigated and appropriate frequency and wave form are suggested. It is proved that the selected frequency and wave form showed an enhanced image with less distortion, which were done by experiments. In addition, a noise elimination is addressed, providing improved image with a GROUND signal integration with the amplifier and the scan driver.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.1
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• pp.52-56
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• 2006

This paper presents a cross-eye characteristics of multi-path wave scattering. Cross-eye method uses the phase differences of multi signals and is used fur electronic protection. When a signal is propagated from transmitter to receiver on the ground surface, direct wave and reflected wave signals are combined in front of the receiving antenna with different phases. To calculate and control the amplitude and phase of reflected signal, we have developed a cross eye electronic protection method for radar system and studied the variation of electric power density.

• Proceedings of the Korean Institute of Landscape Architecture Conference
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• 2020.10a
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• pp.57-57
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• 2020