• Atmosphere
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• v.22 no.1
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• pp.29-45
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• 2012

An unusual autumn storm developed rapidly in the western part of the East sea on the early morning of 23 October 2006. This storm produced a record-breaking heavy rain and strong wind in the northern and middle part of the Yeong-dong region; 24-h rainfall of 304 mm over Gangneung and wind speed exceeding 63.7 m $s^{-1}$ over Sokcho. In this study, MTSAT-1R (Multi-fuctional Transport Satellite) water vapor and infrared channel imagery are examined to find out some features which are dynamically associated with the development of the storm. These features may be the precursor signals of the rapidly developing storm and can be employed for very short range forecast and nowcasting of severe storm. The satellite features are summarized: 1) MTSAT-1R Water Vapor imagery exhibited that distinct dark region develops over the Yellow sea at about 12 hours before the occurrence of maximum rainfall about 1100 KST on 23 October 2006. After then, it changes gradually into dry intrusion. This dark region in the water vapor image is closely related with the positive anomaly in 500 hPa Potential Vorticity field. 2) In the Infrared imagery, low stratus (brightness temperature: $0{\sim}5^{\circ}C$) develops from near Bo-Hai bay and Shanfung peninsula and then dissipates partially on the western coast of Korean peninsula. These features are found at 10~12 hours before the maximum rainfall occurrence, which are associated with the cold and warm advection in the lower troposphere. 3) The IR imagery reveals that two convective cloud cells (brightness temperature below $-50^{\circ}C$) merge each other and after merging it grows up rapidly over the western part of East sea at about 5 hours before the maximum rainfall occurrence. These features remind that there must be the upward flow in the upper troposphere and the low-layer convergence over the same region of East sea. The time of maximum growth of the convective cloud agrees well with the time of the maximum rainfall.

• The Journal of the Acoustical Society of Korea
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• v.32 no.2
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• pp.95-103
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• 2013

An underwater acoustic (UWA) communication in shallow water is strongly affected by the water surface and the seabed acoustical properties. Every reflected signal to receiver experiences a time-variant scattering in sea surface roughness and a grazing-angle-dependent reflection loss in bottom. Consequently, the performance of UWA communication systems is degraded, and high-speed digital communication is disrupted. If there is a dominant signal path such as a direct path, the received signal is modeled statistically as Rice fading but if not, it is modeled as Rayleigh fading. However, it has been known to be very difficult to reproduce the statistical estimation by real experimental evaluation in the sea. To give an insight for this scattering and grazing-angle-dependent bottom reflection loss effect in UWA communication, authors conduct experiments to quantify these effects. The image is transmitted using binary frequency shift keying (BFSK) modulation. The quality of the received image is shown to be affected by water surface scattering and grazing-angle-dependent bottom reflection loss. The analysis is based on the transmitter to receiver range and the receiver depth dependent image quality and bit error rate (BER). The results show that the received image quality is highly dependent on the transmitter-receiver range and receiver depth which characterizes the channel coherence bandwidth.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.303-316
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• 2009

Benthic macroinvertebrate communities collected from eight different streams in South Korea were analyzed to compare community and biological indices across different levels of water pollution. The Self-Organizing Map (SOM) was utilized to provide overview on association of the proposed indices. The sample sites were accordingly clustered according to the gradient of pollution on the SOM. While the general trends of the indices were commonly observable according to different levels of pollution, the detailed differences among the indices were also illustrated on the SOM. The conventional diversity and evenness indices tended to be high even though the water quality state was poor representing relatively weak gradient at polluted sites, while the index presenting the saprobic degree such as family biotic index showed the stronger gradient at the polluted area and was robust to present the gradient. Our results also confirmed the general characterization of two indices: The Shannon index is more strengthened by the number of species occurring at the sample sites, while the Simpson index is more influenced by the degree of evenness among the species. The patterning based on the SOM was efficient in comparatively characterizing the proposed indices to present ecological states and water quality.

• Journal of Environmental Science International
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• v.15 no.10
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• pp.951-960
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• 2006

The eco-hydrodynamic model was used to estimate the environmental capacity in Gamak Bay. It is composed of the three-dimensional hydrodynamic model for the simulation of water flow and ecosystem model for the simulation of phytoplankton. As the results of three-dimensional hydrodynamic simulation, the computed tidal currents are toward the inner part of bay through Yeosu Harbor and the southern mouth of the bay during the flood tide, and being in the opposite direction during the ebb tide. The computed residual currents were dominated southward flow at Yeosu Harbor and sea flow at mouth of bay, The comparison between the simulated and observed tidal ellipses at three station showed fairly good agreement. The distributions of COD in the Gamak bay were simulated and reproduced by an ecosystem model. The simulated results of COD were fairly good coincided with the observed values within relative error of 1.93%, correlation coefficient(r) of 0.88. In order to estimate the environmental capacity in Gamak bay, the simulations were performed by controlling quantitatively the pollution loads with an ecosystem model. In case the pollution loads including streams become 10 times as high as the present loads, the results showed the concentration of COD to be $1.33{\sim}4.74mg/{\ell}(mean\;2.28mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality In case the pollution loads including streams become 30 times as high as the present loads, the results showed the concentration of COD to be $1.38{\sim}7.87mg/{\ell}(mean\;2.97mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality. In case the pollution loads including streams become 50 times as high as the present loads, the results showed the concentration of COD to be $1.44{\sim}9.80mg/{\ell}(mean\;3.56mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.2
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• pp.28-37
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• 2003

We investigated water quality, salinity, nutrients, SS, COD and Chlorophyll-a concentrations in the seawater of the Mokpo costal area, southwestern coast of Korea. Seawater samples at 25 stations were collected in July 20, 25 and September 3, 2002 after a strong rain event. The distributions nutrients in seawater were analyzed using an method of sea water analysis presented by the ministry of Maritime Affairs and Fisheries of Korea. The sampling sites were categorized into the inner and outer harbour based on salinity distribution and difference of nutrients distributions was evidence between these two zones. Nutrients and SS inflow and distributed in the inner harbour by the discharged freshwater from Youngsan river during strong rainfall whereas they were distributed in seawater of outer harbour by natural processes in general coastal area.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.329-332
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• 2003

Aquaculture have been important role to supply food resources for mankind. However, competitive power of domestic mariculture industry was declined due to increase of labor and feed expenditures, and quantity import of low-priced livefishes from the developing underdeveloped nations in North and South East Asia. Mass production and quality enhancement can be pointed out to overcome such an industrial environment in this decade. To meet these requirement, movable mariculture base remodeling feasible vessel of chemical tanker or crude oil carrier has been proposed for more advanced mariculture management system by using deep seawater from about 200m which is sustainablely clean, nutrient-rich and cold seawater. Deep seawater can be applied for control of seawater temperature for mariculture base and cultivation phytoplankton and seaweed as feed. Besides mariculture, strategic marketing can be implemented by raw water and ice of deep seawater. Feasibility of applying deep seawater was considered after evaluating general movable mariculture base and management system.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.2
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• pp.71-86
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• 2022

The water quality index (WQI) has been widely used to evaluate marine water quality. The WQI in Korea is categorized into five classes by marine environmental standards. But, the WQI calculation on huge datasets is a very complex and time-consuming process. In this regard, the current study proposed machine learning (ML) based models to predict WQI class by using water quality datasets. Sihwa Lake, one of specially-managed coastal zone, was selected as a modeling site. In this study, adaptive boosting (AdaBoost) and tree-based pipeline optimization (TPOT) algorithms were used to train models and each model performance was evaluated by metrics (accuracy, precision, F1, and Log loss) on classification. Before training, the feature importance and sensitivity analysis were conducted to find out the best input combination for each algorithm. The results proved that the bottom dissolved oxygen (DO_Bot) was the most important variable affecting model performance. Conversely, surface dissolved inorganic nitrogen (DIN_Sur) and dissolved inorganic phosphorus (DIP_Sur) had weaker effects on the prediction of WQI class. In addition, the performance varied over features including stations, seasons, and WQI classes by comparing spatio-temporal and class sensitivities of each best model. In conclusion, the modeling results showed that the TPOT algorithm has better performance rather than the AdaBoost algorithm without considering feature selection. Moreover, the WQI class for unknown water quality datasets could be surely predicted using the TPOT model trained with satisfactory training datasets.

• Korean Journal of Food Science and Technology
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• v.20 no.3
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• pp.363-370
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• 1988

An attempt was made in this study to investigate the possibility of processing oyster and sea mussel into an intermediate moisture food. To obtain a palatable and instant product, shucked samples were heated in soy sauce for 5 min., heated in seasoning solution for 10 min., and then dried by the method of hot-air blowing for 4-6 hours at $40^{\circ}C$. Optimum seasoning solutions consisted of 2% monosodium glutamate, 3.5% sodium chloride, 15% sorbitol, 2% propylene glycol, 5% glycine and 0.02% rosemary oleoresin in 72.48% water. Judging from water activity, thiobarbituric acid, viable cell count, volatile basic nitrogen, surface color and sensory evaluation, vacuum-packaging method in nylon/PE $(20{\mu}m/40{\mu}m)$ or polyester/viniliden chloride/polypropylene $(12{\mu}m/15{\mu}m/50{\mu}m)$ film bag did hardly damage to the quality of intermediate moisture products, but air-packaging method in polyethylene(0.06m/m) bag did considerable damage to the quality during storage for 60 days in an incubator with 49-51% relative humidity at $30^{\circ}C$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.29-37
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• 2008

This study examined principles and techniques of efficient water quality management as well as total coastal pollutant loads and the relevant examples in the advanced countries from the viewpoints of water quality improvement and pollution control in coastal areas. The problems and improvements in an estimation of the current total pollutant loads were also pointed out. In addition, discussion was made on the relationship between total pollutant loads and environmental capacity as well as particulars requiring extensive examination on access to and study on water quality model used as prediction tool for marine environment. Furthermore, this study proposed details of and improvement plans for water quality control to be reflected and absorbed into systems and policies related to coastal water quality. In coastal areas, which are subject to total coastal pollutant loads, it is necessary to calculate pollutant loads reduction and allocation, to propose them in detail in statement in relations to new pollution sources for the corresponding projects or plans in environmental impact assessment and prior environmental review system. Also, in relations to regional plans for coastal management, the local government concerned must focus more on environmental management plan to implement data on pollution sources and pollutant loads flown into sea areas under basic jurisdiction, therefore it is required to actively respond to expansion and introduction of total coastal pollutant loads system in the future. Total coastal pollutant loads system must be expanded and executed by considering characteristics of sea area and changes in the environment of land. For pollution sources in land, the competent authorities in charge of coastal environment will need to initiatively administer supervision, monitoring activities and achieve integration and operation of the related laws by preparing legal bases for management system or adjusting the related laws.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.1013-1020
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• 2008

To evaluate the pollutant removal efficiency and clarify the cause of low removal efficiency of the wetland, temporal and spacial distributions of water quality were investigated at 16 sites in the Sihwa constructed wetland. The removal efficiency showed a tendency to decrease since the construction of the wetland, except for TN. In addition, the efficiency was largely varied with season, especially BOD and TP. No removal efficiency of BOD was observed in April and July when algal bloom was occurred in lower part open water of the wetland. On the other hand, TP showed no removal efficiency from April to August showing -291% of removal efficiency in August. From the horizontal distribution in closed water regions, SS concentration for the central area was significantly higher than for left and right areas(p = 0.013, center > left > right areas). From the results of this study, we infer that anaerobic condition due to the excessive accumulation of organic matters and lack of uniformity of water flow distribution are major factors of the low removal efficiency of the wetland.