• Korean Journal of Legislative Studies
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• v.25 no.3
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• pp.69-96
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• 2019

This paper is written to suggest several recommendations for South Korea to deter and defend North Korean nuclear threat, when North Korea does not seem to give up its nuclear weapons and the US's extended deterrence including the nuclear umbrella could remain uncertain. For this purpose, it explains key options regarding nuclear deterrence and defense by non-nuclear weapon state. It evaluates the current status of South Korean non-nuclear preparedness against North Korean nuclear threat and provides some recommendations to improve the preparedness. As a result, this paper concluded that South Korean non-nuclear preparedness against North Korean nuclear threat was not that reliable. The preparedness has weakened since the South Korean effort to denuclearize North Korea through negotiations in 2018. In this sense, South Korea could have serious problems in protecting its people from North Korean nuclear threat if the US promise of extended deterrence is not implemented. South Korea should focus on its decapitation operation to North Korean highest leaders in case of North Korean nuclear attack based on a minimal deterrence concept. It should be prepared to conduct preventive strikes instead of preemptive strikes due to North Korea's development of solid fuel ballistic missiles. It should integrate its Ballistic Missile Defense with that of the US forces in Korea. South Korea should make a sincere effort for nuclear civil defense including construction of nuclear shelters.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.121-122
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• 2023

As containerized maritime transport began in earnest, the size of container ships has steadily increased, and recently, the operation of 24,000 TEU-class vessels has become regular. However, concerns about the efficiency and productivity of such mega container ships from a port operational perspective have continued to be raised. The 10^th Busan International Port Conference requested an in-depth study on the trends of container ship enlargement by analyzing the order status of ultra-large container ships from major global liners. Generally, the factor that drives the upsizing of ships is the realization of economies of scale that lowers transportation costs per TEU, which leads to a higher level of cost reduction per unit transportation compared to the increase in fuel consumption due to transporting large amounts of cargo with a single ship. However, it is necessary to examine whether this trend of container vessel enlargement is feasible for port operations. To this end, this study compares and analyzes the productivity and efficeiency of different ship sizes to evaluate the effect of ship size on port operations.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.110-111
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• 2023

As carbon neutrality has recently emerged as a global issue, the carbon neutral roadmap of MOF has been established and various strategies have been proposed to achieve carbon neutrality in the entire marine industry. The port sector is also included in the target for greenhouse gas reduction, but emissions are not being measured due to limitations in data collection and no inventory construction. For building a carbon-neutral port, it is essential to calculate and forecast emissions and set reduction targets. Accordingly, in this study, CO₂ emitted from domestic port equipment was calculated according to the IPCC Guildeline's emission calculation method, and future emission was estimated. As a result of the analysis, about 420,000 tons of CO₂ was emitted based on the cargo volume in 2020, and emissions are expected to continue to increase in proportion to the increase and about 720,000 tons will be emitted by 2050. In order to achieve carbon neutrality of the port, it needs to promote emission reduction by converting the power source for oil-based equipment to eco-friendly fuel. Also container and miscellaneous ports which require complicated cargo handling need to effort to reduce CO₂.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.77-83
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• 2023

Energy consumption is increased by rapid industrialization. As a result, climate change is accelerating due to the increase in CO₂ concentration in the atmosphere. Therefore, a shift in the energy paradigm is required. Hydrogen is in the spotlight as a part of that. Currently 95% of hydrogen is fossil fuel-based reforming hydrogen which is accompanied by CO₂ emissions. This is called gray hydrogen, if the CO₂ is captured and emission of CO₂ is reduced, it can be converted into blue hydrogen. There are 3 technologies to capture CO₂: absorption, adsorption and membrane technology. In order to select CO₂ capture technology, the analysis of the exhaust gas should be carried out. The concentration of CO₂ in the flue gas from the hydrogen production process is higher than 20%if water is removed as well as the emission scale is classified as small and medium. So, the application of the membrane technology is more advantageous than the absorption. In addition, if LNG cold energy can be used for low temperature CO₂ capture system, the CO₂/N₂ selectivity of the membrane is higher than room temperature CO₂ capture and enabling an efficient CO₂ capture process. In this study, we will analyze the flue gas from hydrogen production process and discuss suitable CO₂ capture technology for it.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.1-8
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• 2023

Research, such as developing alternative energy in the transportation field, including aviation, is being actively conducted to solve the issue of current climate change. Interest in ammonia fuel as a carbon free energy (CFE) source is increasing due to the ease of liquefaction and transportation and similarity in energy density to that of methanol. However, explosiveness and toxicity of ammonia make it difficult to handle. Therefore, in this study, stable ammonia production was attempted using relatively easy-to-handle urea water solution (UWS). High temperature steam was used to promote the hydrolysis of ammonia. In order to determine the causes for ammonia production below the theoretical equivalent ratio, it was suggested that there were not enough collisions to promote the hydrolysis based on the kinetic theory of gases. The hydrolysis of unreacted isocyanic acid (HNCO) was tested according to the change in water supply. As a result, an increased amount of ammonia produced was confirmed. The increased amount of ammonia produced in a certain section was dependent on the steam temperature and the flow rate of water supplied.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.72-73
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• 2023

As containerized maritime transport began in earnest, the size of container ships has steadily increased, and recently, the operation of 24,000 TEU-class vessels has become regular. However, concerns about the efficiency and productivity of such mega container ships from a port operational perspective have continued to be raised. The 10th Busan International Port Conference requested an in-depth study on the trends of container ship enlargement by analyzing the order status of ultra-large container ships from major global liners. Generally, the factor that drives the upsizing of ships is the realization of economies of scale that lowers transportation costs per TEU, which leads to a higher level of cost reduction per unit transportation compared to the increase in fuel consumption due to transporting large amounts of cargo with a single ship. However, it is necessary to examine whether this trend of container vessel enlargement is feasible for port operations. To this end, this study compares and analyzes the productivity and efficeiency of different ship sizes to evaluate the effect of ship size on port operations.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.116-118
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• 2023

In recent years, the need for economical and sustainable ship routing has emerged due to the enforced regulations on environmental issues. Despite the development of weather forecasting technology, maritime accidents by rough waves have continued to occur due to incorrect weather forecasts. In this study, onboard measurements are conducted to observe the acutal situation on merchant ships in operation encountering rough waves. The types of measured data include information related to navigation (Ship's position, speed, bearing, rudder angle) and engine (engine revolutions, power, shaft thrust, fuel consumption), weather conditions (wind, waves), and ship motions (roll, pitch, and yaw). These ship experiments was conducted to 28,000 DWT bulk carrier, 63,000 DWT bulk carrier, 20,000 TEU container ship, and 12,000 TEU container ship. The actual ship experiment of each ship is intended to acquire various types of data and utilize them for multi-objective studies related to ship operation. Additionally, in order to confirm the sea conditions, the directional wave spectrum was reproduced using a wave simulation model. Through data collection from ship experiments and wave simulations, various studies could be proceeding such as the measurement for accurate wave information by marine radar and analysis for cargo collapse accidents. In addition, it is expected to be utilized in various themes from the perspective of safety and efficiency in ship operation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.672-680
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• 2023

Weight is a critical factor in the ship design process given that it has a substantial impact on the hydrodynamic performance of ships. Typically, ships are optimally designed for specific conditions with a fixed draft and displacement. However, in reality, weight and draft can vary within a certain range owing to operational activities, such as fuel consumption, ballast adjustments, and loading conditions . Therefore, we investigated how resistance changes under three different loading conditions, namely overload, design-load, and lightship, for small craft, using both model experiments and numerical simulations. Additionally, we examined the sensitivity of weight changes to resistance to enhance the performance of ships, ultimately reducing power requirements in support of the International Maritime Organization's (IMO) goal of reducing CO2 emissions by 50% by 2050. We found that weight changes have a more significant impact at low Froude Numbers. Operating under overload conditions, which correspond to a 5% increase in draft and an 11.1% increase in displacement, can lead to a relatively substantial increase in total resistance, up to 15.97% and 14.31% in towing tests and CFD simulations, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.681-687
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• 2023

The selection technique for optimal operation position selection technique is used to present the initial bow and stern draft with minimum resistance, for achievingthat is, the optimal fuel consumption efficiency at a given operating displacement and speed. The main purpose of this studypaper is to develop a program to select the optimal operating position with maximum energy efficiency under given operating conditions based on the effective power data of the target ship. This program was written as a Python-based GUI (Graphic User Interface) usingbased on artificial intelligence techniques sucho that ship owners could easily use the GUIit. In the process, tThe introduction of the target ship, the collection of effective power data through computational fluid dynamics (CFD), the learning method of the effective power model using deep learning, and the program for presenting the optimal operation position using the deep neural network (DNN) model were specifically explained. Ships are loaded and unloaded for each operation, which changes the cargo load and changes the displacement. The shipowners wants to know the optimal operating position with minimum resistance, that is, maximum energy efficiency, according to the given speed of each displacement. The developed GUI can be installed on the ship's tablet PC and application and used to determineselect the optimal operating position.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.123-133
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• 2023

Commercial hydrogen fuel cell vehicles are charged by compressing gaseous hydrogen to high pressure and storing it in a storage tank in the vehicle. This process causes the temperature of the gas to rise, to ensure the safety to storage tanks, the temperature is limited. Therefore, a heat transfer model is needed to explain this temperature rise. The heat transfer model includes the convective heat transfer phenomenon, and accurate estimation is required. In this study, the convective heat transfer coefficient in the hydrogen fueling process was calculated and compared using various correlation equations considering physical phenomena. The hydrogen fueling process was classified into the fueling line from the dispenser to the tank inlet and the storage tank in the vehicle, and the convective heat transfer coefficients were estimated according to process parameters such as mass flow rate, diameter, temperature and pressure. As a result, in the case of the inside of the filling line, the convective heat transfer coefficient was about 1000 times larger than that of the inside of the storage tank, and in the case of the outside of the filling line, the convective heat transfer coefficient was about 3 times larger than that of the outside of the storage tank. Finally, as a result of a comprehensive analysis of convective heat transfer coefficients in each process, it was found that outside the storage tank was lowest in the entire hydrogen fueling process, thus dominated the heat transfer phenomenon.