• Journal of the Society of Naval Architects of Korea
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• v.34 no.3
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• pp.1-8
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• 1997

Internal solitary waves between two-stratified fluid layers are examined. Hamilton's principle is used to derive a governing equation. The wave speed-wave height relation is obtained and this agrees well with the experiment. The wave profiles obtained also agree well with the experimental result. There exist minimum and maximum wave speeds depending on the depth ratio and the density ratio of two layers. The KdV equation overpredicts the wave speed for a given wave height and underpredict the wave height for a given wave speed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.143-151
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• 1990

The sediment transport in shallow water regions has been studied in various ways and, accordingly, many formulas have been proposed. However, when these formulas are applied practically in the field, they are not sufficient to fully estimate the sediment transport rate yet. The primary reason is how to take into account the effect of irregularities of field waves : wave heights, periods and directions. Therefore, it is necessary to investigate stochastic and kinematic characteristics of waves in three dimensional random seas in order to more accurately estimate it. In particular, the asymmetrical properties of directional spectrum become significant and play an important role in various phenomena in a shallow water region. In this study, their effects of incident waves the joint distribution of wave heights, periods and directions are investigated through field measurements.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.336-344
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• 2007

A method is developed to evaluate partial safety factors for armor units, by which uncertainties of random variables in reliability function as well as wave height distribution with service periods could take into account straightforwardly. It is found that partial safety factors for resistance and wave height are correctly increased with improving target levels on failure of coastal structures at the same return and service periods. Therefore, it nay be possible to determine design variables through the same processes as those of deterministic method by using the partial safety factors for resistance and wave height evaluated in this paper, since uncertainties of random variables and the effects of service periods and target probability failure are directly considered in the processes of evaluation of partial safety factors.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.145-152
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• 1996

In this study, the technique to evaluate the extreme design wave height of certain return period is developed from the given measured or hindcasted sea state data of concerned area for limited period. By using the order statistics and Monte Carlo Simulation method, the best fit probability distribution function with proper parameters describing the given wave height data is chosen, from which extreme design wave height can be predicted by extrapolation to the desired return period. The fitness and the confidence limit of the chosen probability function are also discussed. Application calculation is carried out for the wave height data given by applying the Wilson wave model theory to major 50 typhoon wind data affecting Korean South coast during the year from 1938 to 1987.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.4
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• pp.265-275
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• 2011

Estimation of wave height is the most important factor in the design of coastal structures such as breakwaters. In the present study, typhoon wind distribution was constructed by applying the parametric model of Holland (1980), and numerical simulations on the typhoon-generated waves were carried out using the WAM. The typhoons which affected the southern coast of the Korean Peninsula and several hypothetical typhoons were selected to construct the training sets. Design wave heights were estimated using the empirical simulation technique for various return periods and wave directions. The estimated design wave heights were compared with those by the peaks-over-threshold method and the results of KORDI(2005).

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.421-421
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• 2017

In order to secure the safety of coastal areas from the continuous storm surge in Korea, it is important to predict the wave movement and properties accurately during the storm event. To improve the accuracy of the storm simulation, and to quantify coastal risks from the storm event, the dependencies between wave height, wave period, and storm duration should be analyzed. In this study, therefore, copulas were used to develop multivariate statistical models of sea storms. A case study of the east coast of Korea was conducted, and the dependencies between wave height, wave period, water level, storm duration and storm interarrival time were investigated using Kendall's tau correlation coefficient. As a result of the study, only wave height, wave period, and storm duration appeared to be correlated.

• The Korean Journal of Physiology
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• v.18 no.1
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• pp.51-65
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• 1984

In an effort to elucidate the effect of physical training on the electrocardiographic amplitudes, QRS vector, axis and QRS vector amplitude, electrocardiograms were recorded before and 1, 5 and 10 minutes after 3 minute rebounder exercise in 23 healthy male students aged between 18 and 21 years in two groups of athletes and non-athletes. ECG amplitudes were measured from lead I, $V_1$ and $V_5$ and axis and amplitudes of QRS vectors were measured from lead I and III in frontal plane, from lead $V_2$ and lead $V_6$ in horizontal plane. The results obtained are summarized as follows. ECG amplitudes: The R wave amplitude was $23.38{\pm}1.14\;mm$ in athletes which was higher than $17.91{\pm}2.00\;mm$ in non-athletes. After exercise, the difference in two groups remained significant throughout the recovery period. The S wave amplitude was increased significantly, and the T wave amplitude was decreased in both groups after exercise. The P wave amplitude was increased in both groups after exercise, and it was lower in athletes than in non-athletes. The PQ segment amplitude was zero in athletes but negative in non-athletes than in the resting state. The J point amplitude was positive in resting state and was negative after exercise in both groups. J+0.08 sec point amplitude was also lowered after exercise, and it was higher in athletes than in non-athletes. Therefore the whole ST segment was proved to be decreased after exercise. The summated amplitude of R in $V_5$ plus S in $V_1$ was $38.74{\pm}2.71\;mm$ in athletes which was higher than $32.82{\pm}2.90\;mm$ in non-athletes. After exercise, it was also significantly higher in athletes than in non-athletes. Axis of QRS vector: In frontal plane, axis of QRS vector was $62.7{\pm}7.36^{\circ}$ in athletes, it showed no significant difference between the two groups. In horizontal plane, axis of QRS vector was $-23.5{\pm}7.2^{\circ}$ in athletes which was significantly higher than $-38.8{\pm}8.2^{\circ}$ in non-athletes. After exercise, it was significantly higher than the resting state in both groups. Amplitude of QRS vector : In frontal plane, amplitude of QRS vector was $13.86{\pm}1.44\;mm$ in athletes which was significantly higher than $9.62{\pm}0.97\;mm$ in non-athletes. After exercise, it was also significantly higher in athletes than in non-athletes. In horizontal plane, amplitude of QRS vector was $19.82{\pm}2.10\;mm$ in athletes which was significantly higher than $16.90{\pm}1.39\;mm$ in non-athletes. After exercise, it was also significantly higher in athletes than in non-athletes. From the above, these results indicate that R wave amplitude in athletes was significantly higher than in non-athletes before and after exercise, and that the summated amplitude of R in $V_5$ plus S in $V_1$ in athletes was also $38.74{\pm}2.71\;mm$ suggesting a left ventricular hypertrophy We should note that the PQ segment and ST segment amplitude were higher in athletes than in non-athletes, and they were decreased with exercise in both groups. In particular, the fact that amplitudes of QRS vector in frontal plane or in horizontal plane were significantly greater in athletes than in non-athletes may be an index in evaluating athletes.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.1
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• pp.36-41
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• 2013

In this paper time series wave data are simulated using wave spectrum with random phases of the wave signal. The simulated wave signals are used to study the effect of the sampling rate on the ocean wave characteristics. Effect of sampling rate on wave data which include extreme wave such as freak waves are examined and various wave characteristics including abnormality index (AI), kurtosis of wave profile and maximum wave height are examined. Various wave heights are decreased as the sampling rate decreases. The zero-th moment of the wave spectrum does not affect much on the sampling rate but the second moment are greately affected on the sampling rate. The error due to the sampling rate is decreases as the wave period increases. The error in significant wave height based on the wave spectrum $H_s$ is smaller than that on the time domain method $H_{1/3}$. AI index and kurtosis of wave profile do not deviate much from the exact date as long as the sampling rate is greater than 1 Hz. Ocean wave measurement with the sampling frequency higher than 1 Hz will result the error less than 5% in estimating the height of extreme waves.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.6
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• pp.397-404
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• 2014

In Korea, harbor tranquility is generally estimated by using both methods of investigating harbor calmness under abnormal wave condition and evaluating the harbor serviceability. The efficiency of the former method is questionable as the tranquility of a harbor is judged by a wave height criterion that is arbitrarily determined without rational basis. In case of the latter method, the utilization rate of a harbor is estimated by using the exceedance probability of wave height or the distribution of wave heights and periods that is obtained from longterm measured or hindcasted wave data. Use of long-term data is desirable in order to guarantee the accuracy of the exceedance probability. Meanwhile, the criterion for determining maximum allowable wave height for cargo handling works is too simple and has limitations for being used in an actual field condition. Problems of existing method for estimating harbor tranquility were verified by the wave observation data in Busan New Port. And the importance of the field observation data was emphasized. It is necessary to perform long-term wave monitoring inside and outside of major ports in Korea in order to establish more advanced standard for evaluating harbor tranquility based on such observed wave data.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.639-646
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• 2016

In order to establish an operational standard based on ship size, this study considered a specific safety management plan for Ulsan along with international standards, analyzed the results of mooring safety assessment at four vulnerable piers and suggests cargo stoppage and emergency unberthing standards as follows. In accordance with ship characteristics, ships of less than 10,000 tons are recommended to limit their activities for wind speeds of 18-21 m/s and wave heights of 1.0-1.5 m. Ships from 10,000-50,000 tons are recommended to observe wind speeds of 17-20 m/s and wave heights of 1.2-1.5 m, while, ships of 50,000-100,000 tons are recommended wind speeds of 15-19 m/s and wave heights of 1.5 m. Ships of more than 100,000 tons are recommended wind speeds of 14-18 m/s and wave heights of 1.5 m.