• Journal of Ocean Engineering and Technology
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• v.26 no.2
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• pp.8-13
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• 2012

This paper investigates the statistical properties of waves in the sea area of Uljin, which is located in the East Sea area of Korea. The wave data were measured using AWAC (Acoustic Wave and Current Meter), which was installed at a 16-m water depth from November 2010 to March 2011. The wave data acquisition rate, Hmax, monthly mean Hs, Tz, Tp, and wave direction are summarized. The distributions of Hs and Tz were analyzed using the Hs-Tz scatter diagrams. The measurement wave data were analyzed to investigate freak wave characteristics. By comparing the wave spectrum using the measurement wave data with the wave spectrum obtained by varying the JONSWAP wave spectrum, it was possible to approximate the wave spectrum shape at the Uljin Sea area.

• International Journal of Ocean System Engineering
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• v.2 no.4
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• pp.250-258
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• 2012

The distribution of wave heights is assumed to be a Rayleigh distribution, based on the assumption of a narrow band and Gaussian distribution of wave elevation. The present study was started with doubts about the narrow band assumption. We selected the wave spectra widely used to simulate irregular random waves. The wave spectra used in this study included the Pierson-Moskowitz spectrum, Bretschneider-Mitsuyasu spectrum, and JONSWAP spectrum. The directionality of the waves was considered. The cosine 2-l type directional spreading function and mixed form of the half-cosine 2-s type with Mitsuyasu type directional spreading are considered here to investigate the effects of a directional spreading function on random waves. The simulated wave height distribution is compared with a Rayleigh distribution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.76-83
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• 1993

In this study, an approximate method for calculating the directional spectrum of waves encountering a current in shallow water is developed. The wave trains in tile directional spectrum are assumed to be linear and Gaussian; development of the spectrum requires that the waves also be short crested. The Miche's breaking criterion is imposed to determine the upper limit of wave height and to establish an expression for the breaking wave elevation in terms of the ideal wave's elevation and the second time derivative of wave elevation. Two examples are given; one for a Wallops directional spectrum encountering a shear current and another with an upwelling current.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.146-149
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• 2008

Simulation and signal conditioning on the time domain surface elevation records are conducted to verify the proposed Welch's method in non-directional ocean wave spectrum analysis. These spectrum data are further conditioned to provide wave characteristic that better describe the sea states. Comparison of significant wave height and zero crossing period between the proposed method and a reference toolkit are presented.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.235-242
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• 1999

Wave which propagate from the offshore cause transformation of diffraction, refraction, and reflection etc. in coming in the coastal by depth change. Especially, Wave strongly show the charcateristics of rancom wave in the coastal zone. Developed wave model until a recent date analysed regular waves with height and period equal to those of the significant wave, In case of Monochromatic wave, it can be analysed fine in the offshore, but differ from in coastal zone. In this study, form of governing equation is parabolic mild slope equation. This model calculated random wave for using frequency spectrum and directional spectrum from input data condition of wave. This model is applied to Vincent shoal and compared with laboratory experimental data. The results agreed well with laboratory data.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.6
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• pp.1056-1063
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• 2015

Waves can be expressed in terms of a spectrum; that is, the energy density distribution of a representative wave can be determined using statistical analysis. The JONSWAP, PM and BM spectra have been widely used for the specific target wave data set during storms. In this case, the extracted wave data are usually discontinuous and independent and cover a very short period of the total data-recording period. Previous studies on the continuous wave spectrum have focused on wave deformation in shallow water conditions and cannot be generalized for deep water conditions. In this study, the Generalized Extreme Value (GEV) function is proposed as a more-optimal function for the fitting of the continuous wave spectral shape based on long-term monitored point wave data in deep waters. The GEV function was found to be able to accurately reproduce the wave spectral shape, except for discontinuous waves of greater than 4 m in height.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.1
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• pp.41-47
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• 1989

Using computer simulated irregular waves, variations of ocean wave statistics according to sea state are analyzed, and the reasonable conditions that transform the energy spectrum to individual wave statistics are discussed. Ocean wave statistics varying with sea state are found to respond linearly to the spectral peakedness parameter $Q_p$ and spectrum moments $m_n$ (n = 0, 1, 2${\cdots}{\cdots}\;\infty$ ). It is clarified that the 2nd-order spectrum moment is a reasonable parameter which represents the wave statistics including wave periods, and that the spectrum analysis should be carried out under the conditions of minimum data length of 10 times of peak period $T_p$ with time lag of $7T_p$ to satisfy the stable condition of wave statistics.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.879-880
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• 2006

The subject of this paper is to recognize the stable state of EEG using wavelet transform and power spectrum analysis. An alpha wave, showed in stable state, is dominant wave for a human EEG and a beta wave displayed excited state. We decomposed EEG signal into an alpha wave and a beta wave in the process of wavelet transform. And we calculated each power spectrum of EEG signal, an alpha wave and a beta wave using Fast Fourier Transform. We recognized the stable state by making a comparison between power spectrum ratios respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.586-595
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• 2007

The analytic solution of wave scattering of monochromatic waves on a pile breakwater by an eigenfunction expansion method is extended to the case of directional irregular waves. The scattering wave spectrum and the force spectrum can be expressed from the reflection coefficient, transmission coefficient and the wave forces obtained from changing frequencies and incident angles in monochromatic waves. By numerical integration of 2-dimensional spectrum which is function of frequencies and incident angles, the representative values for the scattered waves and wave forces are obtained and the dependence of the transmission coefficients and wave forces on the directional distribution function, the principal wave direction, the submergence depth, and porosity is analyzed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.583-588
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• 2008

Swell data observed in the East Sea in February, 2008 were analyzed using wavelet method. The wavelet analyzed results show detailed time series variation of wave group, peak frequency and spectrum. The comparison of time averaged wavelet spectrum with fourier spectrum turn out to be very similar in terms of spectrum shape and peak frequency evolution but the peak frequency wave energy and the significant wave height show discrepancies. Wavelet analysis can detect the change of spectrum in time as well as in frequency and very efficient to study transient and irregular phenomena such as freak waves and abnormal swells in the ocean. More analysis with more wave data are needed for future application.