• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1037-1047
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• 2013

A systematic laboratory compaction testing was performed with the laboratory seismic measurements of the compacted specimens sampled from various compaction fills and was supplemented with in-situ seismic testing to investigate the effects of compaction energy on the elastic wave velocities of the railway roadbed materials. The both variances of the compressive and shear wave velocities with moisture content curve ($V_p$-w and $V_s$-w curves) are similar to the general trend of the density-moisture content curve(${\gamma}_d$-w curve). At the wet side of optimal moisture content (OMC), either $V_p$ or $V_s$ does not significantly increase, which is well reflecting the no gaining in density with the increasing compaction energy exceeding modified-D compaction effort. $V_p$ increases linearly with ${\gamma}_d$ at the dry side of OMC, while it does exponentially at the wet side. The in-situ wave velocities were found to be influenced by the level of confinement and $V_s$ was more sensitive to compaction energy than $V_p$.

• Science of Emotion and Sensibility
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• v.17 no.2
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• pp.101-110
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• 2014

High-frequency is sound produced in non-audible area, which couldn't be heard in daily life. The frequency range above 22Khz is called 'high-frequency' and its components are called 'HFC(High-Frequency Components)'. It is known that ocean wave sound is rich in HFC, because it brings serenity and causes ${\alpha}$-waves in human mind. When this natural sound is combined with high-frequency, it seems to give a pleasurable feeling, indicated by an ${\alpha}$-wave increase and a ${\beta}$-wave decrease. We call this phenomena "the hypersonic effects". In this experiment, subjects listened to the ocean wave sound simultaneously with corresponding frequencies similar to ocean wave frequency components created artificially in a electric circuit. Brain waves were measured by an EEG system with 8 channels using 8 electrodes on Fp1, Fp2, F3, F4, T3, T4, O1, and O2. The results showed that ${\alpha}$-wave increase and ${\beta}$-wave decrease were statistically significant while subjects were listening to the ocean wave sound along with the high frequency components, reflecting the hypersonic effect.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.1
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• pp.39-52
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• 2000

The triad interactions have been known to be important only for shoaling waves or finite depth wind waves. In deep water, they are insignificant compared with the quadruplet interactions in respect to the evolution of wind waves due to energy transfer among the wave components. However, the triad interactions may be important even for deep water waves because they may closely be related to the wave steepness, which definitely affects wave breaking, drag of air flow over t.'Ie sea, or navigation of ships, especially during the early stage of the development of wind waves. This study reports a series of laboratory experiments, whose data are subjected to bispectral analyses to investigate the triad interactions of deep-water wind waves. It is found that the bicoherence at the spectral peak frequency and the wave steepness are almost directly proportional, indicating that the steep waves with peaked crests and flat troughs are resulted from the triad interactions. Both bicoherence and wave steepness increase with the wave age during the early stage of wave generation and then drop off as the waves grow old. It seems that the energy of the secondary spectral peak developed by the triad interactions during the early stage of wave generation is redistributed to the neighboring frequencies by the quadruplet interactions during the later stage.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.31-37
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• 2014

In situ investigations and laboratory tests using elastic wave have become popular in geotechnical and geoenvironmental engineering. Propagation velocity of elastic wave is the key index to evaluate the ground characteristics. To evaluate this, various methods were used in both time domain and frequency domain. In time domain, the travel time can be found from the two points that have the same phase such as peaks or first rises. Cross-correlation can also be used in time domain by evaluating the time shift amount that makes the product of signals of input and received waveforms maximum. In frequency domain, wave propagation velocity can be evaluated by computing the phase differences between the source and received waves. In this study, wave propagation velocity evaluated by the methods listed above were compared. Bender element tests were conducted on the specimens cut from the undisturbed hand-cut block samples obtained from Block 37 excavation site in Chicago, IL, US. The evaluation methods in time domain provides relatively wide range of wave propagation velocities due to the noise in signals and the sampling frequency of data logger. Frequency domain approach provides relatively accurate wave propagation velocities and is irrelevant to the sampling frequency of data logger.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.12
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• pp.1825-1832
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• 2013

Since domestic terrestrial DTV transition introduces the need for a multi-channel service as raised again to multi-channel service is being promoted. Current terrestrial broadcasters to realize multi-channel services are provided jointly countermeasures. Multi-channel services also active in policy-making of Korea Communications Commission. Therefore, in this article, terrestrial technical issues that arise in multi-channel services and services for the implementation of policy measures were proposed. Therefore, in this article terrestrial technical issues that arise in multi-channel services and services for the implementation of policy measures by looking at the future terrestrial multi-channel service to pursue the direction and policies of regulatory agencies aims to help.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.113-118
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• 2003

This paper characterizes typical nonlinear loads into two types of harmonic sources, i.e., harmonic voltage source and harmonic current source. A series resonant filter is very effective in harmonic reduction for harmonic voltage source type of nonlinear loads such as personal computer loads with smoothing dc capacitors. A parallel resonant filter is suited for current source type of nonlinear loads such as ac drives with smoothing dc reactors. General compensation characteristics and comparison of series and parallel resonant filters are given analytically and experimentally. Compliance with IEC Std 1000-3-2 has been evaluated for limiting harmonic distortion.

• Geophysics and Geophysical Exploration
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• v.5 no.3
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• pp.145-149
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• 2002

The static correction, which is classified into refraction based static correction and reflection based residual static correction, removes distortions caused by irregularities of thickness or velocity in near-surface. Generally, refraction statics is a time consuming process because of high dependence on the interpreter's analysis. Therefore, for huge 3D seismic data, automatic static correction which minimizes the interpreter's analysis is required. In this research, we introduce an efficient method of refraction static correction for land 3D seismic survey.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.905-911
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• 2005

We propose an efficient adaptive subcarrier selection scheme, in which the active subcarriers and their modulation and coding schemes (MCSs) are selected at the receiver, and subsequently conveyed to the transmitter using limited feedback We theoretically show that capacity maximization can be achieved by selecting subcarriers with highest signal-to-noise ratios (SNRs) and adapting the number of active subcarriers according to channel environments. Furthermore, an ordering based adaptive subcarrier selection algorithm is proposed to select the optimal active subcarriers with low complexity. Numerical results show that the proposed adaptive subcarrier selection scheme provides higher capacity than that obtained by water-filling approaches, even with limited feedback.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.84-89
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• 2006

Tripping of residual current protective devices(RCPDs) caused by harmonics has been continuously reported, but no literature is available on the behavior of RCPDs caused by harmonics. This paper, in order to find out the effects of harmonics on RCPDs, investigated the present condition on malfunction of RCPDs and measured harmonics at buildings where nuisance tripping of RCPDs was often occurred. Also, the operational characteristics of RCPDs were tested by the harmonics synthesizer that can generate distorted waveform. Results of experiment detected that there was minimum tripping current of RCPDs when third harmonic added to the fundamental frequency. And it was found that the leakage current to cause tripping of RCPDs increased with more higher order harmonics added to the fundamental frequency.

• Journal of Navigation and Port Research
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• v.27 no.1
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• pp.55-61
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• 2003

The maneuvering equations of motion are derived to express the motion of a ship. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The linear wave forces whose periods are equal to those of incident waves and the nonlinear wave forces that make long period drift forces are computed for the simulation. The consideration of irregular waves and nonlinear wave force effects on the slew motion are carried on the analyzing the motion of ship in the regular and irregular waves.