• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.4
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• pp.667-678
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• 1997

A primitive equation numerical model driven only by $M_2$ tide is used to examine role of tide in the temperature and velocity fields of Deukryang Bay. The numerical model reproduces several features of the observational temperature fields such that the isotherms tend to be parallel to the coast in the bay, and the colder water exists at the right hand side in the bay. The horizontal temperature and velocity fields in the model are dominantly influenced by bottom topography. The model also shows that the surface colder water in the bay is accompanied by strong-alongshore current during the flood tide. An investigation for baroclinicity in the bay by additional numerical experiment indicates that the baroclinirity in velocity field is very weak. The model, however, did not reproduce a stratification in the observation, implying that the model needs to add other semi-diurnal components such as $S_2,\;O_2\;or\;K_2$ tides to $M_2$ tide.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.3
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• pp.179-184
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• 2003

This study investigated the relationship of fuel weight and depth together with slope on the spread of forest fire. Fire spread was faster on the greater slope in forested land. Fire had a greater spread rate with lighter fuel weight. The thickness of the fuel bed and forest fire spread rate were not related. The fire spread rate was closely related to the slope and weight of the fuel bed (significant at 0.01, 0.05, respectively). The thickness of the fuel bed was not significant (0.05).

• The Korean Journal of Ecology
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• v.27 no.3
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• pp.173-177
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• 2004

The number and abundance of epiphytic algae growing on Sargassum thunbergii and their functional forms were examined. Thalli of S. thunbenii were collected on the nine islands of southern coast and at Gyeokpo on the western coast of Korea in summer 2001. A total of 25 species, 6 green (24%), 2 brown (8%), 17 red algae (68%) were identified in the present study. Caulacanthus okamurae, Ulva pertusa, Sphacelaria furcigera were found on the thalli of S. thunbegii that collected at the all regions. Caulacanthus okamurae, Champia bifida and Laurencia venusta grew on the lower parts of S. thunbergii thalli whereas, Polysiphonia spp. attached to the apical parts of the plants. Four functional forms, such as sheet-form (8%), filamentous-form (52%), coarsely branched-form (32%) and articulated-calcareous algal form (8%) were distinguished. The epiphytic algae on the thalli of S. thunbergii are mainly annual opportunistic algae, filamentous-form algae and smaller red algae. Also, most epiphytic seaweeds of S. thunbergii produce and release spores before pseudoperennial host plants are necrotic in late autumn.

• Journal of Environmental Science International
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• v.16 no.8
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• pp.921-928
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• 2007

The objective of this work is the air quality modeling according to the scenarios of emission on complex terrain. The prognostic meteorological fields and air quality field over complex areas of Seoul, Korea are generated by the PSU/NCAR mesoscale model (MM5) and the Third Generation Community Multi-scale Air Quality Modeling System (Models - 3/CMAQ), respectively. The emission source was driven from the Clean Air Policy Support System of the Korea National institute of Environmental Research (CAPSS), which is a 1 km x 1 km grid in South Korea during 2003. In comparison of air quality fields, the simulated averaged $PM_{10},\;NO_2,\;and\;O_3$ concentration on complex terrain in control case were decreased as compared with base case. Particularly $PM_{10}$ revealed most substantial localized differences by $(18{\sim}24{\mu}g/m^3)$. The reduction rate of $PM_{10},\;NO_2,\;and\;O_3$ is respectively 18.88, 13.34 and 4.17%.

• Journal of Environmental Science International
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• v.19 no.8
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• pp.971-981
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• 2010

The objectives of this study were to measure ambient total gaseous mercury (TGM) concentrations in Seoul, to analyze the characteristics of TGM concentration, and to identify of possible source areas for TGM using back-trajectory based hybrid receptor models like PSCF (Potential Source Contribution Function) and RTWC (Residence Time Weighted Concentration). Ambient TGM concentrations were measured at the roof of Graduate School of Public Health building in Seoul for a period of January to October 2004. Average TGM concentration was $3.43{\pm}1.17\;ng/m^3$. TGM had no notable pattern according to season and meteorological phenomena such as rainfall, Asian dust, relative humidity and so on. Hybrid receptor models incorporating backward trajectories including potential source contribution function (PSCF) and residence time weighted concentration (RTWC) were performed to identify source areas of TGM. Before hybrid receptor models were applied for TGM, we analysed sensitivities of starting height for HYSPLIT model and critical value for PSCF. According to result of sensitivity analysis, trajectories were calculated an arrival height of 1000 m was used at the receptor location and PSCF was applied using average concentration as criterion value for TGM. Using PSCF and RTWC, central and eastern Chinese industrial areas and the west coast of Korea were determined as important source areas. Statistical analysis between TGM and GEIA grided emission bolsters the evidence that these models could be effective tools to identify possible source area and source contribution.

• Journal of Environmental Science International
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• v.23 no.5
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• pp.963-972
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• 2014

In this study, ibuprofen(IBP) degradation by the photochemical ($UV/S_2O{_8}^{2-}$) and sonochemical ($US/S_2O{_8}^{2-}$) processes was examined under various parameters, such as UV ($10{\sim}40{\pm}5W/L$) and US ($50{\sim}90{\pm}5W/L$) power density, optimum dosage of persulfate ion ($S_2O{_8}^{2-}$), temperature ($20{\sim}60^{\circ}C$) and anions effect ($Cl^-$, $HCO_3{^-}$, $CO{_3}^{2-}$). The pseudo-first-order degradation rate constants were in the order of $10^{-1}$ to $10^{-5}min^{-1}$ depending on each processes. The synergistic effect of IBP degradation in $UV/S_2O{_8}^{2-}$ and $US/S_2O{_8}^{2-}$ processes could investigated, due to the generation of $SO_4{^-}$ radical. This result can confirm from the produced $H_2O_2$ and $SO{_4}^{2-}$ concentration in each processes. IBP degradation rate affected by the $S_2O{_8}^{2-}$ dosage, temperature, power and anion existence parameters. In particular, IBP degradation rate increased with the increase of the temperature ($60^{\circ}C$) and applied power density (UV:$40{\pm}5W/L$, US:$90{\pm}5W/L$). On the other hand, anions effect on the IBP degradation was negative, due to the anion play as a the scavenger of radical.

• Journal of the Korean Institute of Gas
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• v.16 no.5
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• pp.58-65
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• 2012

Various models are currently applied to predict the dispersion of leaked combustible gas and overpressure from a vapor cloud explosion(VCE). However, those models use simple approaches where topography and barriers of anti-leakage facilities and the effects of buildings were not sufficiently taken into considerations. For this reason, this study has proposed the dispersion process of leaked gas, distribution patterns, and flames and overpressure generated from gas explosions in 2D and 3D virtual spaces by reviewing more accurately analyzable computational fluid dynamics (CFD) model by considering various variables including combustion types of leaked substances, geometry of facility, warm currents, barriers, the influence of wind, and others. The CFD analysis results are anticipated to be usefully applied for the risk analysis of explosion and for the risk-based design.

• Journal of the Korean Institute of Gas
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• v.16 no.5
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• pp.1-6
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• 2012

It becomes a more and more common practice to build facilities bigger and more integrated in an effort to optimize the process within limited resources and spaces. As the capacity of facilities increases, so does the flow rate and pressure. This in turn leads to a high consequence of accident. Not only are these facilities vulnerable to leakage because of their high pressure, but also subsequent fire and explosion can be threatening. For these reasons, there is an urgent need to come up with solutions to assess and minimize the damage from an accident. The Quantitative Risk Assessment(QRA) is one of the most efficient ways to solve problems on pressurized pipelines. The QRA can be re-enforced by applying reduction factors. In this study various types of accidents in a pressurized pipeline were evaluated. The damage from accidents were computed, then. Finally the reduction factors were very effective to decrease consequences of high pressure pipeline accidents.

• Journal of KIISE:Software and Applications
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• v.36 no.11
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• pp.901-911
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• 2009

In this paper, we propose a construction technique of two-level composite gradient map to automatically track a face with large movement in successive frames. Our method is composed of three main steps. First, the gradient maps with two-level resolution are generated for fast convergence of active contour. Second, to recognize the variations of face between successive frames and remove the neighbor background, weighted composite gradient map is generated by combining the composite gradient map and difference mask of previous and current frames. Third, to prevent active contour from converging local minima, the energy slope is generated by using closing operation. In addition, the fast closing operation is proposed to accelerate the processing time of closing operation. For performance evaluation, we compare our method with previous active contour model-based face tracking methods using a visual inspection, robustness test and processing time. Experimental results show that our method can effectively track the face with large movement and robustly converge to the optimal position even in frames with complicated background.

• Journal of Navigation and Port Research
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• v.32 no.5
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• pp.341-347
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• 2008

Recently, it has been widely recognized that water-front and coastal vegetations may have great value in supporting fisheries, protecting from wave attack, stabilizing the sea bed and maintaining good scenery. Hydrodynamic factors playa major role in the functions of water quality and ecosystems. However, the studies on numerical and analytical process of wave propagation are few and far behind compared to those on the hydrodynamic roles of water-front vegetations. In this study, in order to express wave attenuation into water-front vegetation, a numerical model based on the unsteady mild slope equation is developed. This result is compared with an analytical model for describing the wave attenuation by assumed simple long wave condition. Based on both the analytical and numerical results, the physical properties of the wave attenuation are examined under various wave, geometric and vegetation conditions. Through comparisons between the analytical and numerical results, the effects of the vegetation properties, wave properties and model parameters such as the momentum exchange coefficient have been clarified.