• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.52-61
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• 2016

To inject huge amount of $CO_2$ for CCS application, high pressure pipeline transport is accompanied. Rapid depressurization of $CO_2$ pipeline is required in case of transient processes such as accident and maintenance. In this study, numerical analysis on the depressurization of high pressure $CO_2$ pipeline was carried out. The prediction capability of the numerical model was evaluated by comparing the benchmark experiments. The numerical models well predicted the liquid-vapor two-phase depressurization. On the other hands, there were some limitations in predicting the temperature behavior during the supercritical, liquid phase and gaseous phase expansions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.524-531
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• 2017

Water quality improvement was predicted by using ecological modelling with reference to reduced load pollutants in the Busan coastal area. The results showed appreciable improvement in water quality at Suyeong Bay and Nakdong Estuary but little improvement in water quality from the central to eastern regions, except in Suyeong Bay by COD concentration. There were also similar results for T-N and T-P, because the Busan coastal area has a more open boundary than the other bays in the South Sea of Korea, resulting in a fast flow rate. The reducted COD load was less than that found in other coastal areas. Also, the reduction rate of the total load was less than that of other coastal areas in terms of water quality improvement. Applying the reduction load estimated in this study, it should be possible to improve the water quality of Suyeong Bay and Nakdong Estuary.

• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.2
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• pp.52-59
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• 1998

Many concerns are placed on preservation of coastal environment from the spilled oil contaminant in the coastal area. And the use of computer simulation model to combat with oil spill has come to play mote important role in forecasting the oil spill trajectory so as to protect coastal area and minimize the damage from oil contaminants. The main concerns of this study is how the movements of spilled oil are affected by currents including tidal, oceanic, and wind-driven currents. Especially, in the present paper, the oil spill trajectory can be predicted by a real-time system that allows prediction of circulation and wind field. The harmonic methods are adopted to simulate the tidal currents as well as it can be possible to achieve the wind-field data and oceanic current data from the established database. System performance is illustrated by the simulation of oil spill in the south-eastern coastal area of Korea. Simulation results are compared with the observed one.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.104-110
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• 1997

Increase of marine transpotation in coastal area frequently yields oil spill accidents due to collision or grounding of oil tankers, which affects great deal of damages on ocean environments. Exact prediction of oil pollution area in time domain, which is called oil map, is very important for effective and efficient oil recovery and minimization of environmental damage. The prediction is carried out by considering the two distinct processes which are initial diffusion on the still water surface and advection due to tide, wind wave induced surface currents. In the present paper, only the initial diffusion is dealt with. Somewhat new simulation model and its numerical scheme are proposed to predict it. Simple diffusion experiment is also carried out to check the validity of the present method. Furthermore, some example simulations are performed for virtual oil spill accident. Quite realistic oil map including oil thickness distributions can be obtained by the present model.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1088-1097
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• 2021

Vibration data of mechanical equipment inevitably have noise. This noise adversely af ects the maintenance of mechanical equipment. Accordingly, the performance of a learning model depends on how effectively the noise of the data is removed. In this study, the noise of the data was removed using the Denoising Auto Encoder (DAE) technique which does not include the characteristic extraction process in preprocessing time series data. In addition, the performance was compared with that of the Wavelet Transform, which is widely used for machine signal processing. The performance comparison was conducted by calculating the failure detection rate. For a more accurate comparison, a classification performance evaluation criterion, the F-1 Score, was calculated. Failure data were detected using the One-Class SVM technique. The performance comparison, revealed that the DAE technique performed better than the Wavelet Transform technique in terms of failure diagnosis and error rate.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.918-923
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• 2021

The Korean government is developing a 10-year master plan pertaining to the Public Waters Management and Reclamation Act. However, it was observed that implementation of the reclamation project through frequent changes would occupy a significant proportion. Thus, questions are being raised about the effectiveness of the master plan. In view of this, the need for a trend analysis on long-term reclamation demand is growing. Accordingly, in this study, a trend analysis of reclamation demand was carried out using the annual reclamation performance data. The results of the analysis indicate that the demand for reclamation of public waters continued to decline, and the trend has been particularly evident since the 1990s, when it was converted into a reclamation master plan. In addition, the total demand for reclamation during 2021-2030 was calculated to be at a maximum of 13.8 km² and minimum of 1.7 km².

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.4
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• pp.133-142
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• 2023

In this paper, we built a data-driven artificial intelligence model using RNN-LSTM (Recurrent Neural Networks-Long Short-Term Memory) to predict the Lorenz system, and examined the possibility of whether this model can replace chaotic dynamic models. We confirmed that the data-driven model reflects the chaotic nature of the Lorenz system, where a small error in the initial conditions produces fundamentally different results, and the system moves around two stable poles, repeating the transition process, the characteristic of "deterministic non-periodic flow", and simulates the bifurcation phenomenon. We also demonstrated the advantage of adjusting integration time intervals to reduce computational resources in data-driven models. Thus, we anticipate expanding the applicability of data-driven artificial intelligence models through future research on refining data-driven models and data assimilation techniques for data-driven models.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.1
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• pp.65-74
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• 2020

The purpose of this study was to investigate the physical characteristics of marine environment, and to predict the probability of the occurrence of hypoxia in the Dangdong bay. We predicted hypoxia using the logistic regression model analysis by observing the water temperature, salinity, and dissolved oxygen concentration. The analysis showed that the Brunt-Väisälä frequency which was shallow than the deep bay entrance, was higher inside the bay due to a lesser amount of fresh water inflow from the inner side of the bay, and density stratification was formed. The Richardson number, and Brunt-Väisälä frequency were very high occasionally from June to September; however, after September 2, the stratification had a tendency to decrease. Analysis of dissolved oxygen, water temperature, and salinity data observed in Dangdong bay showed that the dissolved oxygen concentration in the bottom layer was mostly affected by the temperature difference (dt) between the surface layer and bottom layer. Meanwhile, when the depth difference (dz) was set as a fixed variable, the probability of the occurrence of hypoxia varied with respect to the difference in water temperature. The depth difference (dz) was calculated to be 5 m, 10 m, 15 m, 20 m, and the difference in water temperature (dt) was found to be greater than 70 % at 8℃, 7℃, 5℃, and 3℃. This indicated that the larger the difference in depth in the bay, the smaller is the temperature difference required for the generation of hypoxia. In particular, the place in the bay, where the water depth dif erence was approximately 20 m, was found to generate hypoxia.

• Journal of Astronomy and Space Sciences
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• v.15 no.2
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• pp.459-473
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• 1998

As the satellite system becomes more complex, the probability of unpredictable failures may be increased due to design inadequacy, experience deficiency, lack of problem recognition. Poor quality control, improper testing, and workmanship fault. Consequently, these problems can lead to the reduction or end of the satellite mission lifetime. This article addresses general satellite failure modes and factors influencing satellite mission life. The mission life factors of LEO sun-synchronous KOMPSAT spacecraft are investigated, in which its mission life is predicted based on these factors. Since the end of mission due to random failures is not predictable, the predictable mission life factors such as power budget, propellant budget, battery charging/discharging cycle, radiation effects payload reliability, single point failure, and redundancy are primarily investigated.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.322-326
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• 2010

우리나라의 물관리는 기상, 수문, 수질 분야별로 다원화 되어 있고 부처별로도 국토해양부, 환경부, 농림수산식품부, 기상청 등에서 관련법규를 제정하여 물관리 업무를 수행하고 있어 효율적인 물관리가 어려운 실정이다. 현재 각 기관별로 효율적인 물관리를 위해 자체 정보관리시스템을 운영하고 있으나 기관별로 자료공유 및 연계활용이 어렵고 상위업무조정기관의 부재로 수문기상관련 사업의 중복투자가 발생할 가능성이 높다고 할 수 있다. 뿐만 아니라 기상청은 물관리의 핵심정보인 기상관측 및 예측정보를 생산 및 제공하는 기관임에도 불구하고 현재까지 자체적으로 생산되는 정보를 단순히 제공하는 역할만을 수행함으로써 우리나라는 수문기상연계활용 분야에서 많은 어려움을 겪고 있다. 한편, 최근 기후변화로 인해 물 순환 시스템이 변하면서 홍수 가뭄 등의 이상기후가 빈발함에 따라 국가차원의 대책 마련이 필요하며 재해대응 측면에서는 기상재해 극복의 패러다임이 복구위주에서 예방위주로 변하면서 고품질 수문기상예측정보에 대한 요구가 증가하고 있는 추세이다. 따라서 본 연구에서는 수문기상예측정보 생산 및 활용을 위한 운영조직 설립방안과 시스템 구축 방안을 제시하여 효율적인 국가수자원 관리에 도움이 되고자 한다.