• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.1
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• pp.24-34
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• 1997

To find the causes of the downtime problems in Pohang New Harbor, extensive field measurements of short- and long-period waves for 1.5 months and their analyses were made taking into account of wind and downtime records. Measured wave height ratios inside the harbor are appeared to be slightly larger than predicted ones using numerical methods in the previous studies. It is shown that the major causes of the downtime are the wind wave (or swell) higher than loading criteria and also swell with even smaller wave height but longer period(more than 10 sec). Waves of long-period components[0(min)] were recorded as 20 cm high in case of dominant seiche phenomena but they might not be related with the downtime problems.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2003.08a
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• pp.376-381
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• 2003

The reliability analysis of overtopping probability is proposed. In order to estimate the expected overtopping probability of the rubble mound breakwater, the experimental results of individual wave runup height is applied for the analysis of irregular wave system. The joint distribution of wave heights and periods is used for the input data of runup calculation because the runup height depends on the wave height and period. The runup heights during the one event that the design wave attacks the rubble mound breakwater extend to the one life cycle of 60 years. Utilizing the Monte-Carlo method, the one life cycle is tried more about 60 times for obtaining the expected value of overtopping probability. It is found that the inclusion of the variability of wave tidal and wave steepness has great influence on the computation of the expected overtopping probability of rubble mound breakwater. The previous design disregarding the tidal fluctuation largely overestimates or underestimates the expected overtopping probability depending on tidal range and wave steepness.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.63-69
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• 2014

Analysis frequency spectrum through observed wave data in northeastern shore, jeju island, during winter and fall, and review wave characteristics. In order to compute maximum wave height, we calculate the ratio of significant wave height to maximum wave height using the linear regression equation. In addition, for calculating JONSWAP spectrum, we assumed ${\gamma}$ value using significant wave height and peak frequency in the observation area. Consequently, the highest frequency is below 1 m in the case of significant wave height and during the first observation, the mean of height was estimated at 0.523 m and during the scend observation, it was 0.423 m. Furthermore, in peak frequency, the highest frequency was 0.12 Hz~0.15 Hz (period is nearly 6.67s~8.33s), the results of ${\gamma}$ from using significant wave height and peak frequency is 2.72 and the significant wave height calculated by straight linear regression equation was $1.635H_s$.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.38.1-38.1
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• 2011

This study investigates the effects of Pierson-Moskowitz, Jonswap spectrum that are typical irregular wave spectrums for wind turbine system with jacket support structure. Also various offshore environmental parameters based on korean local condition were used in our study. The loads acting on the system was considered by referring to the Design Load Case from IEC guide line. And improved von Karman model was used as a turbulence model. As a result, various significant wave height and peak spectral period cause noticeable difference of extreme and fatigue loads prediction.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.6
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• pp.1601-1610
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• 2007

The purpose of this study was to determine whether a pulse analyzer was useful 1) to characterize the variables of pulse wave of diabetes mellitus group, compared with those of healthy subjects, and 2) to determine Sasang Constitution in diabetes mellitus group and healthy subjects. 1. The sum of pulse pressure (energy) and the ratio of systolic period area (As%), called pulse pressure-related variables, were higher in diabetes mellitus group than healthy group, while the height of dicrotic wave (h5) and the ratio of height of dicrotic wave to height of percussion wave (h5/h1), correlated with arterial compliance, were lower in diabetes mellitus group than healthy group. 2. Taeumin of diabetes mellitus group showed higher pressure-related variables than that of healthy group. 3. Soumin of diabetes mellitus group had shorter the time to dicrotic wave (t5) than that of healthy group. 4. Soyangin of diabetes mellitus group showed higher heart rates and lower values in pulse wave time-related variables, including time to dicrotic wave(t5), time to incisura (t4), total time minus time to incisura (t-t4), total time (t), width of percussion wave (w), and the ratio of width of percussion wave to total time (w/t), than that of healthy group. 5. Contact pressure (CP), sum of pulse pressure (energy), height of pre-incisura (h2), height of incisura (h4), width of percussion wave (w), time to incisura (t4), time to percussion wave (t1), variance of total time (Vt), variance of height of percussion wave(Vp) and the ratio of height of incisura to height of percussion wave (h4/h1) were used to develop the rules of Sasang Constitution Classification with about seventy five percents accuracy. These suggested that the pulse analyzer was useful to evaluate the risk degree of diabetes mellitus and to determine Sasang Constitution among either diabetes mellitus group or healthy group.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.14-24
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• 2015

This study proposed an estimation method of allowable wave height for loading and unloading of the ship and evaluation of effective working days considering moored ship motion that is affected by sip sizes, mooring conditions, wave periods and directions. The method was examined validity by comparison with wave field data at pier $8^{th}$ in Pohang New Harbor. The wave field data obtained with wave height of 0.10~0.75 m and wave period of 7~13 s in ship sizes of 800~35,000 ton when a downtimes have occurred. On the other hand, the results of allowable wave height for loading and unloading of the ship in this method have obtained with wave heights of 0.19~0.50 m and wave periods of 8~12 s for ship sizes of 5,000, 10,000 and 30,000 ton. Thus this method well reproduced the field data respond to various a ship sizes and wave periods. And the results of this in Korea are didn't respond to various the ship sizes and wave periods, and we h method tended to decrease in 16~62 percent when have considered long wave, and it is decreased in 0~46 percent when didn't consider long wave than design standards in case of the ship sizes of 5,000~30,000 ton, wave period of 12 s and wave angle of $75^{\circ}$. The allowable wave heights for loading and unloading of the ship proposed by design standards in Korea have found that overestimated on smaller than 10,000 ton. On the other hand, the rate of effective working days considering ship motion at pier $8^{th}$ in Pohang New Harbor reduced in 6.5 percent when compare with the results without considering ship motion.

• Journal of Wind Energy
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• v.14 no.3
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• pp.25-33
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• 2023

In order to secure the safety of increasing offshore activities such as offshore wind farm maintenance and fishing, IMPACT, a mid-term marine weather forecasting system, was established by predicting marine weather up to 7 days in advance. Forecast data from the Korea Hydrographic and Oceanographic Agency (KHOA), which provides the most reliable marine meteorological service in Korea, was used, but wind speed and wave height forecast errors increased as the leading forecast period increased, so improvement of the accuracy of the model results was needed. The Model Output Statistics (MOS) method, a post-correction method using statistical machine learning, was applied to improve the prediction accuracy of wave height, which is an important factor in forecasting the risk of marine activities. Compared with the observed data, the wave height prediction results by the model before correction for 6 to 7 days ahead showed an RMSE of 0.692 m and R of 0.591, and there was a tendency to underestimate high waves. After correction with the MOS technique, RMSE was 0.554 m and R was 0.732, confirming that accuracy was significantly improved.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.4
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• pp.139-147
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• 2021

In this study, waves were defined using the water surface elevation data observed from the HeMOSU-1 and 2 marine meteorological observation towers installed on the west coast of Korea, and correlation analysis was performed between wave parameters. The wave height and wave period were determined using the wave-train analysis method and the wave spectrum analysis method, and the relationship between the wave parameters was calculated and compared with the previous study. In the relation between representative wave heights, most of the correlation coefficients between waves showed a difference of less than 0.1% in error rate compared to the previous study, and the maximum wave height showed a difference of up to 29%. In addition, as a result of the correlation analysis between the wave periods, the peak period was estimated to be abnormally large at rates of 2.5% and 1.3% in HeMOSU-1&2, respectively, due to the effect of the bimodal spectrum that occurs when the spectral energy density is small.

• Journal of Korea Water Resources Association
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• v.46 no.2
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• pp.205-218
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• 2013

The likelihood of rip current at Haeundae beach according to wave parameters, such as wave height, period, direction, and tidal elevation, was estimated by using numerical simulations with a Boussinesq model, FUNWAVE. To examine the estimation, the rip current occurred on 12th June, 2011 at Haeundae beach was simulated based on observations. For the estimation, the following procedure was carried out. First, extensive numerical simulations of nearshore circulations are performed under various random sea conditions according to the wave parameters. Second, from the numerical results, cross shore components of two-wave-period averaged velocities over the nearshore area were computed, and their seawardly maximum was defined as rip current velocity of the area. Third, using time series of the rip current velocity, we computed the ratio of the simulation time and the time period in which the rip current velocity exceed a threshold velocity for rip-current accidents, and thus the ratio was quantified as the likelihood of rip current at Haeundae beach for the input wave parameters. From the resultant estimations, it was found that the rip current likelihood increases as wave height and period increase, and tidal elevation decreases.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.399-408
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• 1999

Copeland’s(1985) hyperbolic mild-slope equation including diffraction refraction and reflection in the wave field is used as a governing equation in this study. The result of Maruyama & Kajima(1985) is used to calculate wave direction and that of Watanabe & Maruyama(1986) is used as a energy dissipation formula. Numerical solutions are obtained by the Leap-Frog scheme and compared with Watanabe & Maruyama’s (1984) hydraulic experimental results and numerical simulation results for the detached breakwater. This wave model is applied to a detached breakwater and compared with Watanabe and Maruyama’s (1984) hydraulic model results to check the characteristics of reflected wave field around a detached breakwater. The distribution of wave height and we phase in front of a detached breakwater is more accurate than the Watanabe and Maruyama’s numerical results. The results from our wave model show good agreements with the others and also show nonlinear effects around the detached breakwater. This model is applied to the Gamcheon harbor of pusan. the field observations were carried out at Pusan harbor wave station in 1986-1995 and the results were accepted as a design wave condition in this study. The wave height and wave period was measured by Dong-A university at one station in the Gamcheon harbor in 1996-1997 and used as a calibration criterion. The measured data were used as input data for the numerical simulation and also compared with simulated results. The numerical simulation shows a fairly good results which considering the effect of topographic characteristics and effect of narrow entrance due to two separated breakwaters in Gamcheon harbor. The wave distribution characteristics inside Gamcheon harbor is quite different with the offshore wave direction and wave period.