• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.4
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• pp.91-105
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• 2013

This study performed an assessment of wave power potential in the Kangwon and Dongnam regions encompassing the East Sea and part of South Sea. Annual electricity production and economic effects of 28 wave energy converters with 750kW capacity were analyzed using significant wave height and peak wave period data(created from the NOAA's NWW3 model) and InVEST software(developed by Stanford University and University of Minnesota). Annual electricity production was estimated to be up to 1,207MWh/year and at least 163MWh/year. The spatial pattern of annual electricity production showed that the sea far from land has higher wave power potential than the sea near coast. The net present value(NPV) of 28 wave energy converters was calculated by considering an operation period of 25 years. When assuming that the electricity produced from wave energy converters is transferred to onshore power plants through underwater cables, the NPV was estimated to be up to 5,883USD(6,600,000KRW) and at least -63,494USD(-71,000,000KRW). In contrast, the NPV increased up to 28,095 USD(31,600,000KRW) when assuming that the electricity is utilized in the Ulleungdo and Dokdo. In addition, it was found that the break-even line of NPV in the East Sea becomes closer towards the land according to the increment of electricity price. The NPV of wave energy converters near the Ulleungdo and Dokdo will be 88,158 USD(99,000,000KRW) if the increment of electricity price is 100KRW.

• 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 $1.635H_s$.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.367-373
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• 2023

Aircrews and passengers are exposed to radiation from cosmic rays and secondary scattered rays generated by reactions with air or aircraft. For aircrews, radiation safety management is based on the exposure dose calculated using a space-weather environment simulation. However, the exposure dose varies depending on solar activity, altitude, flight path, etc., so measuring by route is more suggestive than the calculation. In this study, we developed an instrument to measure the cosmic radiation dose using a general-purpose Si sensor and a multichannel analyzer. The dose calculation applied the algorithm of CRaTER (Cosmic Ray Telescope for the Effects of Radiation), a space radiation measuring device of NASA. Energy and dose calibration was performed with Cs-137 662 keV gamma rays at a standard calibration facility, and good dose rate dependence was confirmed in the experimental range. Using the instrument, the dose was directly measured on the international line between Dubai and Incheon in May 2023, and it was similar to the result calculated by KREAM (Korean Radiation Exposure Assessment Model for Aviation Route Dose) within 12%. It was confirmed that the dose increased as the altitude and latitude increased, consistent with the calculation results by KREAM. Some limitations require more verification experiments. However, we confirmed it has sufficient utilization potential as a cost-effective measuring instrument for monitoring exposure dose inside or on personal aircraft.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.372-382
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• 2006

Most of the conventional breakwaters impermeable breakwaters which block seawater exchange between the outside and inside of the harbors. The blocking of seawater exchange may cause pollution of water in harbors. To solve the water pollution problem, various kinds of seawater exchange breakwaters have been proposed. Their types can be classified into the current type which uses tidal current, and the overtopping type which uses the wave energy. The overtopping type breakwaters require a discharge coefficient to calculate the rate of overtopping into the harbor. The present study is to compute the rate of overtopping with introduction of a correct discharge coefficient and to evaluate the effect of the overtopping type breakwater on the water qualify inside a harbor. The rate of overtopping was computed by using Forchheimer formula with time dependent mild-slope equation for various wave conditions. The formula has been generally used to calculate the overflow discharge in steady state river flows. The discharge coefficient, which is the key parameter of the calculation, was determined by a series of hydraulic model tests. The present scheme was applied to the seawater exchange section of the western breakwater of Jeju New Harbor's and the efficiency of that section was examined. The calculated results showed that the rate of overtopping into the harbor reached about $27.5m^3/s$ in the wave condition (wave height 3.7 m, wave period 8.5s, and wave direction NNW).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.5
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• pp.223-233
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• 2018

The predictability of winter storm waves using KMA's operational wind forecasts has been studied to predict wind waves and swells in the East coast of Korea using SWAN. The nested model were employed along the East coast of Korea to simulate the wave transformation in the coastal area and wave dissipation term of whitecapping is optimized to improve swell prediction accuracy. In this study, KMA's operational meteorological models (RDAPS and LDAPS) are used as input wind fields. In order to evaluate model accuracy, we also simulate wind waves and swells using ECMWF reanalysis and KIOST WRF wind and they are compared with the KMA's operational wave model and the wave measurement data on the offshore and onshore stations. As a result, it has the lowest RMSE and the highest correlation coefficient in the onshore when the input wind fields are KMA's operational meteorological forecasts. In the offshore, all of the simulate results shows good agreements with similar error statistics. It means that it is very feasible to use SWAN model with the modified whitecapping factor and KMA's operational meteorological forecasts for predicting the wind waves and swells in the East coast of Korea.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.141-142
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• 2007

In recent years, the rate of mean sea level rise is increasing rapidly from the phenomena of global warming, together with the increasing trend of the storm scale. The issue of sea level rise is multifaceted and produces a range of environmental problems. Especially, high tides and the tidal currents become higher, and wave base increases, so the energy received at the coastal boundary may increase. This brings that many coastal environments go into disequilibrium, such as damages to the structures, erosion, and deposition Similarly it was known that the problems of nearshore processes and damage of berth and counter facilities during storm period had appeared at the small fishery port. Here we try to analyze the impact of the rearrangement of counter facilities and berth layout adopted for tranquility of its'inner harbor. Because this harbor is being connected to channel and open sea, the rearrangement of the structures might affect to the current speed and direction and wave height, so do to the sea bottom undulation. Therefore, we made model test for the several layouts of the berth and breakwater in this area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.3
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• pp.575-583
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• 2017

Various types of flow patterns around the stepped weir and spillway, such as the skimming flow over such structures and the wave-type flow with a standing undular hydraulic jump and roller downstream of the structures, are developed in open channels. Unsteady three-dimensional numerical simulations are carried out using a hybrid RANS-LES turbulence modeling approach and the volume of fluid method for resolving free surface fluctuations to represent the turbulent flow including the skimming flow and wave-type flow over a stepped weir installed in a rectangular channel. The comparison of numerical results with an existing experimental measurement reveals that the present numerical simulations reasonably well reproduce the turbulent flow passing the stepped weir, in terms of time-averaged velocity profiles at selected locations downstream of the weir, flow topology characterized by the wave-type and skimming flows, the maximum height and length of the standing wave and the length of reattachment of recirculating zone. The numerical result further elucidates the distinct flow behaviors of the wave-type and skimming flow by presenting instantaneous intense variations of free surface and velocity vectors, the distributions of Reynolds shear stress and turbulent kinetic energy and three-dimensional complex features of coherent structures and total pressure distribution.

• JOURNAL OF ELECTRICAL WORLD
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• s.349
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• pp.90-94
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• 2006

“해마다늘어만가는지구촌곳곳의기상이변, 특히세계유전지대의혹독한풍수해가지난해와마찬가지로일시에밀어닥친다면올해도국제유가의고공행진은하늘을찌를것이다.” 고유가가대세로점쳐지고있는가운데 2 0 0 6년새해를맞아유가의고공행진에대한극단적인우려감이높다. 지난해지구촌이 겪은미국발 허리케인의공포가채 가시지 않은 탓이다. 고유가의정착으로 인해고통을감내한 세계각국은올해초 국제유가의향방을대부분부정적으로내다보고있다. 고유가의원인으로는수요급증에따른수급불균형을우선꼽으면서도고공행진의유가를촉발할여러가지변수도다각도로진단하고있다. 지난해40% 가까이급등한국제유가는올한해에도고공비행을계속할것으로보고있는가운데일부언론은유가 6 0달러시대는이제기정사실화됐다고보도하기도했다. 만약부정적인상황이온다면“WTI 가격은최고 8 0달러, 두바이유가격은최고 6 7달러수준까지상승한다”는전망이나오는가하면“미국과이란의정치적충돌로페르시아만폐쇄사태라도터진다면유가가배럴당 1 0 0달러까지도치솟을수있다”는 경고도 나오고 있다. 우려는 하되 긍정적인 시각도 있다. 고유가가 올해 인플레에 미칠 영향에 대해 경제협력개발기구( O E C D ) 의코엔빈센트수석애널리스트가바로이경우다. 그는최근의고유가는지난 7 0년대와 8 0년대초의석유파동때와는성격이다르다고전제하면서다음과같이진단했다. “당시는공급쪽의충격이컸으나이제는수요급증으로발생하는것”이라고지적하며“선진권경제의석유의존도가크게떨어진점도고유가의파고가큰우려가되지않는다”고밝히고있다. 국내 전문가들도중동정세가 안정되고 미국 경기가 크게 둔화돼 석유수요가감소할경우에도 O P E C의 적극적 감산이예상돼유가가 4 0달러대밑으로내려가기는어려울것으로내다보고있다. 케임브리지에너지연구소( C E R A ) 의경우브렌트유기준으로 지난 연말 배럴당 5 5 . 4달러에서 올해는 5 3 . 5달러로되레떨어질것으로내다봤다. 2006년미국과중국의석유수요가대폭둔화될경우배럴당 4 1 . 3달러까지하락할수도있다는전망을내놨다. 그러나주요산유국의공급차질로인한비관 적인상황이도래할경우엔배럴당7 6달러까지도급등할것이라는경고도덧붙였다. 하여튼 2 0 0 6년유가의향방은고공추세에다주변변수가어떻게잘마무리되느냐, 나아가돌발풍수해에따라선‘껑충’거릴수밖에없다는진단이우세하다. 새해를맞아최근의국제유가동향과나아가유가의향방및변수를진단해봤다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5B
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• pp.321-329
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• 2012

Two regular progressive wave trains, the directions of which are slightly different from each other, develop a honeycomb pattern of wave crests due to their nonlinear interaction. In the honeycomb pattern of wave crest, the nodal line area, which has very low wave energy, is formed. When the honeycomb pattern is developed near the beach area, rip current evolves through the nodal line area formed in the cross shore direction. In this study, to confirm that the formation of honeycomb pattern of waves near the beach area is a dominant mechanism of rip current occurred at Haeundae beach, we performed a numerical simulation of nearshore circulation at Haeundae beach under an unidirectional and monochromatic wave condition by using a nonlinear Boussinesq equation model. As a result, wave refraction due to topographical characteristics (i.e., submerged shoal) of Haeundae gave rise to several wave trains propagating with slightly different directions toward the beach, and consequently rip currents well developed through the nodal line area of honeycomb patterns of wave crest. In addition, we found that a narrow-banded spectral wave condition (i.e., a swell spectrum) increases more likelihood of rip current than a broad-banded spectral wave condtion based on the simulations employing various wave spectra with an equivalent wave height and period.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.434-445
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• 2020

In this study, the minimization of harbor oscillation using permeable breakwater was applied to the actual harbor and investigated an effect of minimization by computer simulation in order to take into account the water quality problems and measures of harbor oscillation by infragravity waves at the same time. The study site is Mukho harbor located at East coast of Korea that harbor oscillation has been occurred frequently. The infragravity waves obtained by analyzing the observed field data for five years focused on the distribution between wave periods of 40 s and 70 s and wave heights in less than 0.1 m was 94% of analyzing data. The target wave periods was 68.0 s. The most effective method of minimization of harbor oscillation by infragravity waves was to install a detached permeable breakwater with transmission coefficient of 0.3 on the outside harbor and replace some area of the vertical wall in the harbor with wave energy dissipating structure to achieve a reflectivity of 0.9 or less. The amplitude reduction rate of this method shown in 27.4%. And the effect of the difference in transmission coefficient of permeable breakwater on the reduction rate of the amplitude was not significant.