• Korean Journal of Environment and Ecology
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• v.26 no.6
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• pp.868-875
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• 2012

This study was carried out to analyze the vegetation properties, soil characteristics and ordination of Hemerocallis hongdoensis population in South Korea. The Hemerocallis hongdoensis population was classified into Mallotus japonicus dominant population, Viburnum wrightii dominant population, Melampyrum setaceum dominant population. Hemerocallis hongdoensis were mainly distributed along the coast of south-western iland of the Korean penninsula and it's population was located at an elevation of 6m to 362m. In the study sites, soil organic matter, total nitrogen, exchangeable potassium, exchangeable calcium, exchangeable magnesium, cation exchange capacity and soil pH were 16.18~21.70%, 0.56~0.97%, 0.42~0.88mg/kg, $3.38{\sim}5.65cmol^+/kg$, $1.12{\sim}2.38cmol^+/kg$, $25.93{\sim}41.45cmol^+/kg$, and 4.45~4.86 respectively. Mallotus japonicus dominant population was found in the steep sloped area that has high percentage of cation exchange capacity and total nitrogen than other populations. Viburnum wrightii dominant population was found gentle sloped area that has low percentage of cation exchange capacity and total nitrogen. Melampyrum setaceum dominant population was found in the medium sloped area that has medium percentage of cation exchange capacity and total nitrogen. Current status of Hemerocallis hongdoensis habitats is very vulnerable with local development constantly threatening the species' survival. Thus, concrete conservation plans to protect natural habitats should be set up as soon as possible.

• 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).

• Geophysics and Geophysical Exploration
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• v.14 no.1
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• pp.18-24
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• 2011

A multi-channel seismic reflection (MCS) survey was conducted in 2009 to explore the deep crustal structure of the Pacific Plate south of Hokkaido. The survey line happened to traverse a 250-km-wide Warm Core Ring (WCR), a current eddy that had been generated by the Kuroshio Extension. We attempted to use these MCS data to delineate the WCR fine structure. The survey line consists of two profiles: one with a shot interval of 200m and the other with a shot interval of 50 m. Records from the denser shot point line show much higher background noise than the records from the sparser shot point line. We identified the origin of this noise as acoustic reverberations between the sea surface, seafloor and subsurface discontinuities, from previous shots. Results showed that a prestack migration technique could enhance the signal buried in this background noise efficiently, if the sound speed information acquired from concurrent temperature measurements is available. The WCR is acoustically an assemblage of concave reflectors dipping inward, with steeper slopes (${\sim}2^{\circ}$) on th ocean side and gentler slopes (${\sim}1^{\circ}$) on the coastal side. Within the WCR, we recognised a 30-km-wide lens-shaped structure with reflectors on the perimeter.

• Journal of Navigation and Port Research
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• v.30 no.6 s.112
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• pp.533-539
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• 2006

Today the harbor oscillation problems are the most significant factor to design harbors serving the very large ships. Large vessels moored in the elastic hawsers at the coastal harbors are often displaced due to the resonance between the long period waves and mooring system. The cargo handling may be interrupted and the hawsers may be broken, especially when the amplification becomes remarkable. The most significant harbor which is confronted with harbor oscillation problem in Korea is the Pohang New Port. Many cases of problems are being notified by the pilot association and local office of MOMAF. However, it is difficult to prevent the arrival of long waves musing oscillation within this harbor. Moreover, government already started new port plan at the mouth of Yeongil Bay without treating problems occurred in the Pohang New Port. This study deals with the variation of harbor oscillation due to the construction of 4.1km breakwater at the bay mouth and new port plan. Numerical method used are fairly standard form from the extended mild slope equation The obtained numerical results were compared with the field measurement from the previous study and this will bring a certain level of discussion and consideration of variation in the future port development.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.4
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• pp.278-289
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• 2009

In the present study, we evaluated the target reliability indices and partial safety factors for caisson sliding of a vertical breakwater. The average of the reliability indices of existing breakwaters was proposed as the target reliability index for the breakwater of normal safety level. The target reliability indices of high and low safety levels were also proposed based on the analysis of breakwaters in Korea and Japan. The partial safety factors were then proposed for each safety level by averaging the values calculated for 12 breakwater crosssections in Korea. The appropriateness of the proposed partial safety factors was partly verified by showing that the reliability index calculated by using the present partial safety factors is located between those of mild and steep bottom slopes of JPHA(2007). The proposed partial safety factors were inversely used to calculate the caisson width and reliability index of existing breakwaters. While the reliability indices of existing breakwaters designed by the deterministic method show a large variation, those designed by the partial safety factor method show a small variation. This indicates that the partial safety factor method allows a consistent design for given target probability of failure.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.199-206
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• 2006

Today the harbor oscillation problems are the most significant factor to design harbors serving the very large ships. Large vessels moored in the elastic hawsers at the coastal harbors are often displaced due to the resonance between the long period waves and mooring system. The cargo handling may be interrupted and the hawsers may be broken, especially when the amplification becomes remarkable. The most significant harbor which is confronted with harbor oscillation problem in Korea is the Pohang New Port. Many cases of problems are being notified by the pilot association and local office of MOMAF. However, it is difficult to prevent the arrival of long waves causing oscillation within this harbor. Moreover, Government already started new port plan at the mouth of YoungIl Bay without treating problems occurred in the Pohang New Port. This study deals with the variation of harbor oscillation due to the construction of 4.1km breakwater at the bay mouth and new port plan. Numerical method used are fairly standard form from the extended mild slope equation. The obtained numerical results were compared with the field measurement from the previous study and this will bring a certain level of discussion and consideration of variation in the future port development.

• Korean Journal of Environment and Ecology
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• v.21 no.6
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• pp.468-486
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• 2007

It was found that vascular plants distributed at Yeondo islet were composed of 107 families, 312 genera, 408 species, 2 subspecies, 51 varieties and 5 forms, totaling 466 taxa. 39 species including Myrica rubra among the 466 taxa were evergreen broad-leaved tree, and as for flora region science-based specially designated plants by the Ministry of Environment, it was surveyed that 85 taxa(46 families, 70 genera, 80 species and 5 varieties) were distributed by identifying 53 taxa in grade one, 1 taxa in grade two, 26 taxa in grade three, 3 taxa in grade four, and Milletia japonica and Arisaema negishii in grade five. In the naturalized plants, a total of 42 taxa(13 families, 37 genera, 40 species and 2 varieties) were surveyed to be distributed and the ratio of their naturalization and Urbanization Index was analyzed to be 9.01% and 14.63%, respectively. Life form spectra bore a type of H-Dl-R5-e. Vegetation of Yeondo islet are classified as Pinus thunbergii community and Castanopsis sieboldii community, and Miscanthus sinesis var. purpurascens community spread on an gently slanted mountain side.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.1
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• pp.34-44
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• 1992

A numerical model using Hybrid Element Method(HEM) is presented for the prediction of wave agitations in a harbor which are induced by the intrusion and transformation of incident short-period waves. A linear mild-slope equation including bottom friction is used as the governing equation and a partial absorbing boundary condition is used on solid boundaries. Functional derived in the present paper is based on the Chen and Mei(1974)'s concept which uses finite element net in the inner region and analytical solution of Helmholtz equation in the outer region. Final simultaneous equations are solved using the Gaussian Elimination Method. The model appears to be reasonably good from the comparison of numerical calculation with hydraulic experimental results of short-wave diffraction through a breakwater gap(Pos and Kilner, 1987). The problem of requring large computational memory could be overcome using 8-noded isoparametric elements.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.6
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• pp.381-387
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• 2014

Recently the large-height swell-like waves generated in the eastern coast of South Korea have been observed frequently. The characteristics of the runup and overtopping of the large-height swell-like waves formed in deep water and attack the coast, causing damages to both lives and facilities have been studied. The correlation between spectral shape parameters and significant wave height has been investigated by analyzing long term wave spectrum data. Numerical runup experiments using MIKE21 BW Module were performed with $Q_p$, additional shape parameter, and identified the variations and characteristics of runup heights with respect to the variations of spectral shape.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.178-189
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• 2004

For designing a reliable harbor, a methodology for estimating design waves of 97.5% operable harbor condition is suggested using long-term wave data. For a practical application of the methodology, a marine police harbor was selected as a site. Wave data used were collected from February 1993 to December 2003 at Jodo wave gage station in front of Pusan harbor. Joint distributions of significant wave height and significant wave period for specified wave directions were obtained and used to feed as input waves for parabolic mild-slope wave model. Results showed that input waves with significant wave height of 1.75 m, significant wave period off sec and wave direction E yield design waves height of 1.06 m at the site of interests, which is a 97.5% operable harbor condition. Wind waves generated inside harbor showed to be no effect on the design wave condition. Swells propagated from deep water into harbor are shown to be dominant effects on the design waves of operable harbor condition.