• International journal of advanced smart convergence
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• v.8 no.1
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• pp.58-64
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• 2019

In recent years, small mobile devices called personal mobility or smart mobility have attracted attention. Personal mobility refers to electric-driven personal transportation that can travel at close range and medium distance, including small electric vehicles, electric bicycles, electric motorcycles and electric scooters. Most of the electric scooters used in Korea are mainly imported from China. This is due to the fact that the price competitiveness of major components of electric scooters is owned in China. At this point, the domestic research direction is preferable for the composition and design of the electric scooter body rather than cost reduction for the components. In this study, we propose a new model of portable folding structure that is easy to use for electric scooters, which are personal vehicles using electric energy. We also made a prototype for practical use.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.478-489
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• 2023

In this study, fault diagnosis and detection methods developed to ensure the reliability of polymer electrolyte membrane (PEM) hydrogen electrolysis systems have been proposed. The proposed method consists of model development and data generation of the PEM hydrogen electrolysis system, and data-driven fault diagnosis learning model development. The developed fault diagnosis learning model describes how to detect and classify faults in the sensors and components of the system.

• Journal of Korea Society of Digital Industry and Information Management
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• v.18 no.3
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• pp.33-41
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• 2022

Recently the use of personal mobility devices is rapidly increasing, and the businesses related to personal mobility devices are quickly growing as well. Although the use of personal mobility devices provides convenience for short distance movements, many problems occur due to the lack of safety devices and the absence of associated road traffic laws. The number of accidents caused by using personal mobility devices continues increasing every year, and the injuries or deaths are seriously happening with those accidents. When using personal mobility devices, there are basic safety precautions such as wearing a helmet, prohibiting boarding with more than two people, prohibiting boarding with more than 100kg, prohibiting using after drinking alcohol, and so on. However, it is exposed to traffic accidents because there is no way to check before using the system. Therefore, to ensure the user's safety in using the electric kickboard among personal mobility devices, this paper proposes a system that can check the user's safety state before using the electric kickboard. It is possible to safely use personal mobility devices and prevent accidents by proposing a system structure of the electric kickboard that can be used after checking for the use of more than two people, overweight, wearing a helmet, and drinking alcohol.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.253-256
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• 2016

In this paper, the power system with electric vehicles is analyzed considering the mobility and diffusion rate of electric vehicles in the smart grid environment. In the previous studies, load modeling and load composition rates have been researched and the results are applied to develop a new load model to explain the mobility of electric vehicles which could affect on the power system status such as power flow and stability. The results would be utilized to research and develop power system analysis methods considering movable charging characteristics of electric vehicles including movable discharging characteristics which could be affected by the diffusion progress of electric vehicles.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.51-58
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• 2020

With the emergence of the words Personal Mobility (P.M.) or Smart Mobility (S.M.), which are terms for personal transportation, the activities of related technologies are increasing with the research. Personal transportation is basically used as a short distance transportation method using electrical energy. As personal mobility became more popular, the resulting products and studies are spreading throughout the country. Most of the electric scooters, which are personal vehicles, are mostly imported from China. This is due to the fact that the price competitiveness of major components of electric scooters is owned in China. At this point, the domestic research direction is considered to be desirable in terms of composition and design of the electric scooter body. In this study, the models of portable electric scooters according to the number of wheels mounted on portable electric scooters were presented and the prototypes were produced accordingly. The number of wheels applied to the electric scooter was 2 and 3 and 4; the contents and advantages and disadvantages of the proposed portable electric scooter models were reviewed.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.4
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• pp.350-357
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• 2023

In this study, the experimental investigation and theoretical analysis were conducted to verify the cooling capacity of the cryocooler used for pre-cooling of hydrogen gas. The effect of the flow rate on a copper pipe attached to the bottom of the cryocooler, which has a coil shape in a hydrogen line, was investigated. Temperature sensors were strategically placed at various positions on the cryocooler to analyze the temperature variations with respect to the flow rate. In this study, the thermal properties of hydrogen for the pressure and temperature were utilized using REFPROP to analyze the cooling capacity of the cryocooler. Based on the experimental results derived from this study, the cooling capacity of the cryocooler for pre-cooling hydrogen gas was considered by calculating the cooling temperature according to the flow rate through theoretical analysis.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.4
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• pp.342-349
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• 2023

In this study, a numerical simulations were conducted to analyze the phase change behavior of a liquid hydrogen storage container. The effects of gravity direction and hydrogen filling rate on boil-off gas (BOG) in the storage container were investigated. The study employed the volume of fluid, which is the phase change analysis model provided by ANSYS Fluent (ANSYS, Canonsburg, PA, USA), to investigate the sloshing phenomenon inside the liquefied hydrogen fuel tank. Considering the transient analysis time, two-dimensional simulation were carried out to examine the characteristics of the flow and thermal fields. The results indicated that the thermal flow characteristics and BOG phenomena inside the two-dimensional liquefied hydrogen storage container were significantly influenced by changes in gravity direction and hydrogen filling rate.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.439-446
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• 2023

In this study, the computational fluid dynamics (CFD) simulations were conducted to verify the cooling capacity of the cryocooler used for pre-cooling of hydrogen gas. Based on the experimental results, the effect of the flow rate on a copper pipe attached to the bottom of the cryocooler was investigated. In this study, the temperature data was calculated through the change of boundary condition for heat flux in the copper pipe. In addition, the cooling capacity of the cryocooler for pre-cooling hydrogen gas was considered by calculating the cooling temperature according to the flow rate in the certified operating range. Consequently the pre-cooing system for hydrogen gas was validated with a reasonable accuracy through CFD simulations.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.456-464
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• 2023

In this study, a compact hydrogen liquefaction system was constructed with the aim of creating a data storage and monitoring program for liquid hydrogen production. This program was designed to receive and record signals from diverse control equipment through the LabVIEW software. A range of measurement instruments were devised to collect data, encompassing variables such as flow rate, pressure, temperature, and liquid level. As a result, it was possible to directly check the production of liquid hydrogen by obtaining various data of condensed liquid hydrogen. In addition, it was confirmed that long-term storage of liquid hydrogen is possible by developing automatic ON/OFF through the LabVIEW program.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.615-622
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• 2023

In this study, the theoretical analysis focused on the quantity of liquid hydrogen required for cooling down to 20 K, as well as the generation of boil-off gas (BOG) from the cooling process of the cryogenic components. The study involved calculating the amount of liquid hydrogen needed to achieve the desired temperature for the cryogenic components and subsequently determining the resulting BOG production at various reference temperatures. It was shown that it was important to efficiently lower the temperature of cryogenic parts through preliminary cooling. As a result, the reference temperature and pressure had an influence on the BOG generation on the cooling of cryogenic components using liquid hydrogen.