• The Korean Journal of Malacology
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• v.30 no.1
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• pp.9-15
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• 2014

This study is aimed at figuring out the reasons of the mass mortality of abalone and the increase in its mortality rate in the sea cage. The study suggests that lack seawater circulation in an abalone aquaculture cage is an important culprit for it. We analyzed the current distribution around a 1/20 scaled-down abalone unit cage of 4 rows and 10 columns by fluid flow visualization technique (PIV : Particle Image Velocimetry). The speed of current in the model cage definitely slowed down in the first column of a unit cage. We also observed currents going down to the bottom of a water tank from the unit cages placed in the middle. The speed of wakes behind inside the row in the middle was slower than that outside the row. Water velocity inside and outside a real abalone cage at Nowha Island adjacent to Wan Island was measured to verify results from the tank test. The speed of current in front of the cage by 2 m was 0.11 m/sec while it was only 0.0009 m/sec inside the cage. It had similar findings with those of a tank test.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1061-1068
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• 2013

This study predicts distillate productions according to design variables by numerical analysis when the waste heat from a diesel generator is added to the solar-assisted still proposed in a previous study. Mathematical models were set up in reference to previous studies, and the amount of heat exchange from the waste heat recovery pipe was considered. To ensure the reliability of numerical analysis, the result was compared with that of a previous study and then, the distillate productions according to design variables were obtained by the analysis model. The results were found to generally be in agreement, and the increasing amount of distillate production of the still with the added waste heat was confirmed. In addition, the optimal value of the tilt angle of glass cover and the number of cells were determined by numerical analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.432-436
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• 2015

This study computationally explored the thermal performance of passively-cooled polymer heat sinks utilizing seawater. Polymer heat sinks are proposed as cooling modules of the cold sides of thermoelectric generators for waste heat recovery. 3-D Computational Fluid Dynamics (CFD) modelling was conducted for a detailed numerical study. Polyphenylene sulfide (PPS) and pyrolytic graphite (PG) were selected for the base materials of polymer heat sinks. The computational study evaluated the performance of the PPS and PG heat sinks at various fin numbers and fin thicknesses. Their performances were compared with those of aluminum (Al) and titanium (Ti) heat sinks. The study results showed that the thermal performance of the PG heat sink was 3~4 times better than that of the Ti heat sink. This might be due mainly to the better heat spreading of the PG heat sink than the Ti heat sink. The effect of the number of fins on the performance of the PG heat sink was dissimilar to the cases of the PPS and Ti heat sinks. This result can be explained by the interrelationships among heat spreading, surface area enhancement, and fluidic resistance incorporating with an increase in the number of fins.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.685-695
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• 2015

Mud, iron oxide, plaster, salt, minerals, and dissolved metals are sequentially deposited in accordance with the increasing concentration of seawater. In this paper, by using the physical characteristics of the seawater, we propose a new vacuum heat-transfer technology to subsequently obtain the proportion of the dissolved components in a cost-effective manner. Based on the vacuum heat-transfer characteristics of seawater, we comprehensively divide the seawater resource processes into the following four processes: (1) the salt concentration process to the saturation concentration, (2) crystallization process for salt formation, (3) mineral precipitation, and (4) remaining of dissolved metals.

• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.604-613
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• 2016

The sea level of the Earth is rising approximately 2.0mm per year (global average value) due to thermal expansion of sea water, melting of glaciers and other causes by global warming. However, when it comes to design a river, the standard of design water level is decided by analyzing four largeness tide value and harmonic constant with observed tidal water level. Therefore, it seems the external water level needs to consider an increasing speed of the seawater level which corresponds to a design frequency. In the present study, the hourly observed tidal water level targeting 47 tidal stations operated by Korea Hydrographic and Oceanographic Administration (KHOA) from beginning of observation to 2015 per hour has been collected. The variation of monthly and yearly and increasing ratio have been performed divided 4 seas such as the Southern, East, Western, and Jeju Sea. Also, the external water level existing design for rivers nearby a coast was been reviewed. The current study could be used to figure out the cause of local seawater rise and reflect the external water level as basic data.

• Korean Journal of Remote Sensing
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• v.34 no.6_2
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• pp.1203-1213
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• 2018

In Arctic and Antarctic ocean, remote sensing is the most effective observation for environmental changes due to the inaccessibility of the regions. Even though satellite, UAV (Unmanned Aerial Vehical) are well known remote sensing platforms, and research vessel also used for automatic measurement on the regions, varied environment of Polar regions require time series and wide coverage of data. Especially, in high latitude, apply an optical satellite remote sensing is not easy due to low sun altitude. In this paper, we introduce an operation of hyper-spectrometer (HyperSAS/Satlantic inc.) which is mounted on Ice Breaker Research Vessel ARAON of Korea Polar Research Institute since 2010, to acquire an above water reflectance atomatically through every research cruise on Arctic and Antarctic ocean and transit both regions. In addition to, auxiliary data for the remotely acquired data, in situ water sampling were also obtained. The above water reflectance and in situ water sampling data are continuously acquired since 2010 will contribute to improve an Ocean Color algorithm in the high latitude and help to understand ocean reflectances over from high latitude through low latitude. Preliminary result from above water reflectance showed characteristics of Arctic ocean and Antarctic Ocean and used to develop algorithms for estimating various ocean factors such as chlorophyll and suspended sediment.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.209-218
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• 2021

First principle-based modeling studies have been performed to improve the heat exchange efficiency of ORV and optimize operation, but the heat transfer coefficient of ORV is an irregular system according to time and location, and it undergoes a complex modeling process. In this study, FNN, LSTM, and AutoML-based modeling were performed to confirm the effectiveness of data-based modeling for complex systems. The prediction accuracy indicated high performance in the order of LSTM > AutoML > FNN in MSE. The performance of AutoML, an automatic design method for machine learning models, was superior to developed FNN, and the total time required for model development was 1/15 compared to LSTM, showing the possibility of using AutoML. The prediction of NG and seawater discharged temperatures using LSTM and AutoML showed an error of less than 0.5K. Using the predictive model, real-time optimization of the amount of LNG vaporized that can be processed using ORV in winter is performed, confirming that up to 23.5% of LNG can be additionally processed, and an ORV optimal operation guideline based on the developed dynamic prediction model was presented.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.587-596
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• 2022

Sea levels are rising as a result of climate change, and low-lying areas along the coast are at risk of flooding. Therefore, we tried to investigate the relationship between sea level change and climate indices using satellite altimeter data (Topex/Poseidon, Jason-1/2/3) and southern oscillation index (SOI) and the Pacific decadal oscillation (PDO) data. If time domain data were converted to frequency domain, the original data can be analyzed in terms of the periodic components. Fourier transform and Wavelet transform are representative periodic analysis methods. Fourier transform can provide only the periodic signals, whereas wavelet transform can obtain both the periodic signals and their corresponding time location. The cross-wavelet transformation and the wavelet coherence are ideal for analyzing the common periods, correlation and phase difference for two time domain datasets. Our cross-wavelet transform analysis shows that two climate indices (SOI, PDO) and sea level height was a significant in 1-year period. PDO and sea level height were anti-phase. Also, our wavelet coherence analysis reveals when sea level height and climate indices were correlated in short (less than one year) and long periods, which did not appear in the cross wavelet transform. The two wavelet analyses provide the frequency domains of two different time domain datasets but also characterize the periodic components and relative phase difference. Therefore, our research results demonstrates that the wavelet analyses are useful to analyze the periodic component of climatic data and monitor the various oceanic phenomena that are difficult to find in time series analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.308-308
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• 2019

지구상 해양, 대기 및 대륙 상호간의 연속적인 물의 거동을 나타내는 물의 순환의 주요 과정 중 하나인 유량 자료는 경년부터 수십년간의 다양한 기상학적 변동성을 내포하며 해당 지역의 수문기상학적 특성을 반영한다. 이러한 기상학적 변동성 중에서 비교적 긴 시간 주기를 나타내는 저주파 진동은 전지구적 기후변화의 장기적 영향을 나타내며 해수면 상승, 홍수 또는 가뭄과 같은 극한 수문사상을 나타내는 매우 주요한 지표로 활용되고 있지만 관측된 수문 시계열의 짧은 자료길이로 인하여 통계적 분석의 신뢰성에 한계를 보여왔다. 따라서 과거 수문 시계열의 확장으로 인하여 부재의 영역으로 남아있던 자료 기간의 한계가 보완되면 보다 정확하고 신뢰도 있는 분석이 가능할 것이다. 나무나이테를 활용한 고기후 복원 등의 연구가 증가하고 있지만 공학 분야에서 이를 실제로 활용한 연구는 아직 미비하다. 따라서 본 연구에서는 과거 기후의 정보를 바탕으로 복원된 수문 시계열을 활용하여 수문 시계열에 내재된 장기 기후 변동성을 통계적으로 분석하기 위한 문헌들을 조사하고, 장기적인 시간 흐름에 내재된 잠재적인 경향 및 변동성을 통계적 분석을 파악하고자 한다. 이를 위해 주어진 수문 시계열에 내재된 저주파 신호을 추출하기 위한 경험적 모드분해법을 활용하여 수문 자료에 내재된 장기 변동성을 추출하였으며, 산업화 이전부터 연장된 수문 시계열의 공학적 활용성을 분석하고자 한다.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.27-33
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• 2007

In this research, to develop the practical application system of fresh water generation system with plate-type fresh water generator using low pressure evaporation method is the main object, and to do that, this study used the evacuated solar collector with operating range of about $50-85^{\circ}C$ as thermal energy source and solar photovoltaic as electric energy source. To achieve that object, this study set up the demo-plant, then estimated and analyzed the usefulness, the safety, and the reliability through pre-tests during short time ahead of the long-time operation. This study showed that the pumps, which are including sea water supply, ejector, hot water supply, and fresh water pumps, were operated one after another. And, the fresh water yield was closely related with the solar irradiance and lower supply temperature of hot water was revealed more reasonable for the solar energy desalination system. That is due to the insufficient area than the solar collector area being required that was estimated through the performance tests of the fresh water generator.