• Journal of the Society of Naval Architects of Korea
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• v.56 no.1
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• pp.58-65
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• 2019

The stability, reliability and efficiency of a smart ship are important issues as the interest in an autonomous ship has recently been high. An automatic collision avoidance system is an essential function of an autonomous ship. This system detects the possibility of collision and automatically takes avoidance actions in consideration of economy and safety. In order to construct an automatic collision avoidance system using reinforcement learning, in this work, the sequential decision problem of ship collision is mathematically formulated through a Markov Decision Process (MDP). A reinforcement learning environment is constructed based on the ship maneuvering equations, and then the three key components (state, action, and reward) of MDP are defined. The state uses parameters of the relationship between own-ship and target-ship, the action is the vertical distance away from the target course, and the reward is defined as a function considering safety and economics. In order to solve the sequential decision problem, the Deep Deterministic Policy Gradient (DDPG) algorithm which can express continuous action space and search an optimal action policy is utilized. The collision avoidance system is then tested assuming the $90^{\circ}$intersection encounter situation and yields a satisfactory result.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1023-1037
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• 2018

The interest in the use of shield TBM (Tunnel Boring Machine) on the tunnel excavation has been increased rapidly in Korea. The shield TBM tunnel is generally designed as non-drainage tunnel. Consequently, if water leakage through the segment joints happens, big problems on the usage and stability of tunnel can be occurred. In this study, the variation of waterproof capacity of hydrophilic rubber waterstop and gasket, respectively by the construction error and excessive displacement of segment was studied. The test results show that hydrophilic rubber waterstop has favorable on the offset, however unfavorable on the gap. On the other hand, gasket has unfavorable on the offset, however favorable on the gap.

• Journal of the Korean GEO-environmental Society
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• v.20 no.10
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• pp.5-14
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• 2019

Recently, earthquakes have occurred in our country and seismic stability of high-rise buildings in large cities is being a growing interest and thus the related studies have been increased. Also the grounds are considered indirectly in most of seismic designs and analyses and seismic researches based on 3D dynamic analysis are insufficient. In this study, therefore, 2D and 3D dynamic analyses were performed based on the SSI complete model including grounds and the behavior was compared and analyzed. For dynamic modeling, linear time history analyses were performed by using MIDAS GTS NX. For this purpose, a high-rise building was assumed to be constructed on top of the bedrock and surrounded by a surface layer. A sensitivity analysis was performed with the selected parameters. The dynamic behavior was compared and analyzed in terms of horizontal displacements, drift ratios, bending stresses, and weak parts. In most cases, 2D dynamic behavior was calculated to be larger than 3D's and thus it shows more conservative results with increasing number and size of weak parts.

• Journal of Industrial Convergence
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• v.13 no.4
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• pp.11-28
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• 2015

A company have to grow constantly. If a company does not grow and stagnant, it will be finally out of the market. The contemporary companies fully make use of M&A to search for new growth engines. The reason of companies using M&A as a important tool of a business strategy is the fastest way to achieve technology power, market power, competitiveness. The form of M&A was that leading companies take over smaller companies or merger and acquisition between small companies in the middle of 2000. But now, Mega mergers between industry leading companies often occur and especially domestic of course M&A of foreign companies occurs actively. These days the boom of stock market and the big companies are pouring on sale by restructuring, privatization and the basis of low interest will make the M&A market continuously. In this study, I suggest a solution of actual human resources management by analyzing proven M&A cases and search for various problems of a gap in the leadership and communication in connection with integration of organization culture after M&A. First of all, I arrange the theoretical concept of the subject and analyze the key factors of the success M&A cases, lastly I suggested a HR strategy after M&A. After M&A, HR strategy is ; First, a company have to build a organization culture which is that merger company accommodate a excellent organizational characteristic of predecessor company with consideration of culture difference. Second, M&A must proceed to remove of anxiety about the future and employment stability by excellent leaderships. Third, organization integration after M&A is influenced by the level of integration for that reason it was verified that M&A have to make progress by communication of each 2 organizations.

• CELLMED
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• v.11 no.1
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• pp.6.1-6.7
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• 2021

In situ gelling devices, as they enter the body, are dosage forms in the shape of the sol but turn into gel types under physiological circumstances. Transition from sol to gel is contingent on one or a mixture of diverse stimuli, such as transition of pH control of temperature, irradiation by UV, by the occurrence of certain ions or molecules. Such characteristic features may be commonly employed in drug delivery systems for the production of bioactive molecules for continuous delivery vehicles. The technique of in situ gelling has been shown to be impactful in enhancing the potency of local or systemic drugs supplied by non-parenteral pathways, increasing their period of residence at the absorption site. Formulation efficacy is further improved with the use of mucoadhesive agents or the use of polymers with both in situ gelling properties and the ability to bind with the mucosa/mucus. The most popular and common approach in recent years has provided by the use of polymers with different in situ gelation mechanisms for synergistic action between polymers in the same formulation. In situ gelling medicine systems in recent decades have received considerable interest. Until administration, it is in a sol-zone and is able to form gels in response to various endogenous factors, for e.g elevated temperature, pH changes and ions. Such systems can be used in various ways for local or systemic supply of drugs and successfully also as vehicles for drug-induced nano- and micro-particles. In this review we will discuss about various aspects about use of these in situ gels as novel drug delivery systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.5
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• pp.709-718
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• 2021

As regulations on environmental pollution of ships have been strengthened, interest in smart ships such as electric propulsion ships equipped with hybrid power systems is increasing. Since batteries used in electric propulsion ships have a larger capacity than batteries used in vehicles, the price is high and maintenance is considered important. The ship's battery is manufactured as an integral type and is managed by the battery management system, and the maintenance and repair of the battery is performed through the replacement of the battery. we design and implement a battery module and a control algorithm using pre-cell for easy battery management. In addition, a controller is designed to transmit the data necessary for the electric propulsion ship power system control to the power control system. When a battery to which the corresponding spare-cell is applied is used, the stability of the ship and the battery system is increased, and it can have an advantage in terms of maintenance and repair.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.21-27
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• 2022

For carbon neutrality, interest in R&D and infrastructure construction for hydrogen energy, an eco-friendly energy source, is growing worldwide. In particular, for hydrogen stations installed in downtown areas, underground hydrogen infrastructure are being considered to increase a safety distance from hydrogen tank explosions to adjacent structures. In order to design an appropriate location and depth of the underground hydrogen infrastructure, it is necessary to evaluate the impact of the explosion of the underground hydrogen infrastructure on adjacent structures. In this paper, a numerical model was developed to analyze the effect of the underground hydrogen infrastructure explosion on adjacent structures, and the over pressure of the hydrogen tank was evaluated using the equivalent TNT (Trinitrotoluene) model. In addition, parametric analysis was performed to estimate the stability of adjacent structures according to the construction conditions of the underground hydrogen infrastructure.

• Korean Journal of Materials Research
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• v.32 no.9
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• pp.369-378
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• 2022

The recycling of solid waste materials to fabricate carbon-based electrode materials is of great interest for low-cost green supercapacitors. In this study, porous carbon foam (PCF) was prepared from waste floral foam (WFF) as an electrode material for supercapacitors. WFF was directly carbonized at various temperatures of 600, 800, and 1,000 ℃ under an inert atmosphere. The WFF-derived PCF (C-WFF) was found to have a specific surface area of 458.99 m²/g with multi-modal pore structures. The supercapacitive behavior of the prepared C-WFF was evaluated using a three-electrode system in a 6 M KOH aqueous electrolyte. As a result, the prepared C-WFF as an active material showed a high specific capacitance of 206 F/g at 1 A/g, a rate capability of 36.4 % at 20 A/g, a specific power density of 2,500 W/kg at an energy density of 2.68 Wh/kg, and a cycle stability of 99.96 % at 20 A/g after 10,000 cycles. These results indicate that the C-WFF prepared from WFF could be a promising candidate as an electrode material for high-performance green supercapacitors.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.93-99
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• 2021

In order to decrease the weight of stretchable energy storage devices, interest in developing lightweight materials to replace metal current collectors is increasing. In this study, nanofibers prepared by electrospinning a conductive polymer, PEDOT:PSS, were used as current collectors for lithium ion batteries. The nanofiber showed improved electrical conductivity by using DMSO, a dopant, and indicated a stretch rate of 30% or more from the elasticity evaluation result. In addition, the use of the nanofiber current collector facilitates penetration of the liquid electrolyte and exhibits the effect of increasing the electronic conductivity through the nanofiber network. The lithium-ion battery using the DMSO-doped PEDOT:PSS@PAM nanofiber current collector indicated a high discharge capacity of 135mAh g^-1, and indicated a high capacity retention rate of 73.5% after 1000 cycles. Thus, the excellent electrochemical stability and mechanical properties of conductive nanofibers showed that they can be used as lightweight current collectors for stretchable energy storage devices.

• Current Photovoltaic Research
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• v.11 no.3
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• pp.79-86
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• 2023

As we strive to mitigate the environmental impact caused by the use of fossil fuels, the exploration of alternative energy sources has gained significant attention. Solar energy, in particular, has emerged as a promising solution due to its eco-friendly nature and virtually limitless availability. Among the various types of solar cells that harness this abundant energy source, organic solar cells have garnered considerable interest. Organic solar cells feature a photo-active layer composed of organic semiconductors, offering a range of appealing advantages such as cost-effectiveness, flexibility, translucency, and the ability to produce customizable colors. However, the commercialization of organic solar cells has been impeded by certain challenges, notably their relatively low efficiency and stability. To overcome these obstacles and pave the way for wider adoption, researchers have been exploring innovative approaches, including the implementation of ternary blend organic solar cells. This strategy involves introducing a third component into the photo-active layer alongside the organic semiconductors, with the aim of enhancing the overall performance of the solar cell. In this paper, we delve into the issues associated with organic solar cells and focus on one potential solution: ternary blend organic solar cells. Specifically, we examine the application of this approach to PM6:Y6, which stands as one of the most popular combinations of organic semiconductors. By investigating the potential of ternary blends, particularly utilizing PM6:Y6, we aim to accelerate the commercialization of organic solar cells.