• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.1
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• pp.33-38
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• 1997

Generally, various semiconductor switching devices for power systems are used in battery chargers for electric vehicle. When these used, it takes the problems of transient-current or distortion of waveforms in power systems near by battery chargers because of harmonics and large peak-current, low power factor, etc., caused by the non-linearity of these devices. Recently, power factor control, line current peak-cut, harmonics reduction which was ignored in past is more and more important. In this paper, to solve those problems we will improve the characteristics of voltage rising and propose the high power factor converter circuit for battery chargers. Our proposed system convert commutated voltage to AC resonant wave in high frequency inverter and rectify the link voltages passed high-frequency transformer and transfer the DC voltages. Especially, the effect using these converter system can be improved very large by power factor control and we have to verify the possibilities of improvement through the experiment of Pb-Acid battery application.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.35-42
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• 1996

In this paper, a development of model based battery SOC indicator is described. The proposed method is independent upon initial SOC, is reliable on the sudden change of load, and could estimate the available driving distance. The mathematical model of battery which has relation of the current, voltage and SOC estimates the SOC by least square estimation to minimize the error between measured voltage and estimated voltage. For experiment, the charging and discharging system using computer was designed to acquire the current and voltage data for model. The feasibility in electric vehicle was confirmed by variable load testing using the developed SOC indicator by stand-alone type microcontroller.

• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.1-7
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• 2012

Systematic safety research by Korea Government has been made to enhance the safety of CNG (compressed natural gas) vehicles since the burst of compressed cylinder of an urban bus in August 9, 2010. This article summarizes some major activities to ensure the safety of CNG vehicles, which covers review of regulation, safety management system including standard of inspection and certification, and training program of inspectors and car mechanics. Specifically, the followings were reviewed; type of CNG cylinder, location of CNG cylinder, material and type of fuel line and vent line, modification of pipeline connection, installation of gas detector, installation of emergency shutdown valve, installation of protecting cover for cylinder, obligations for CNG vehicle filling station. improving periodical inspection, routine test on gas vehicles, training program for engaged in gas vehicles, and designation of safety manager for CNG bus company. This paper suggests how to improve safety of CNG vehicles as a result of review of above mentioned check items.

• Journal of IKEEE
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• v.25 no.3
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• pp.528-533
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• 2021

This paper presents the PCB heat dissipation characteristics of high density DC-DC converter for electric vehicles. This paper also analyzes the heat dissipation structure of the high density DC-DC converter and optimizes the PCB heat dissipation design of the high density power system through thermal analysis simulation. Based on heat transfer theory, the thermal path of general electronic devices is analyzed and the thermal resistance equivalent circuit is modeled in this paper. Additionally, the thermal resistance equivalent circuit of the 500W synchronous buck converter, which is addressed in this paper, is modeled to present a structural heat dissipation path for better thermal performance. The validity of the proposed scheme is verified through the thermal analysis simulation results and experiments applying multi-surface heat dissipation structure to a 500[W](12[V], 41.67[A]) synchronous buck converter prototype with an input voltage 72[V].

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.306-313
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• 2019

Owing to the present problems of air pollution and fossil fuel exhaustion, ongoing research has been actively focused on developing an electric actuator system that can utilize diverse energy sources without producing any exhaust gas. Since the motors of such electric vehicles generally rotate at a high speed, the initial acceleration capability required for an automobile is insufficient. In this study, the motor output was decelerated by the transmission; the initial acceleration of the vehicle was increased, and the motor size and weight were reduced. The driving motor and transmission, which each form isolated structures, were integrated to simplify the connector for input and output. By reducing the cooling system's capacity, a vehicle was designed and manufactured that represents a structural change in effective technology.

• Convergence Security Journal
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• v.19 no.2
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• pp.59-72
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• 2019

In this day and age physical and cyber boundaries have converged due to the development of new technologies, such as the Internet of Things (IoT) and the Cyber Physical System (CPS). As the relationship between physical system and cyber technology strengthens, more diverse and complex forms of risk emerge. As a result, it is becoming difficult for single organization or government to fully handle this situation alone and cooperation based on information sharing and the strengthening of active defense systems are needed. Shifting to a system in which information suitable for various entities can be shared and automatically responded to is also necessary. Therefore, this study tries to find improvements for the current system of threat information collecting and sharing that can actively and practically maintain cyber defense posture, focusing particularly on the structuring of information sharing platforms. To achieve our objective, we use a risk communication theory from the safety field and propose a new platform by combining an action-oriented security process model.

• Membrane Journal
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• v.32 no.5
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• pp.357-365
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• 2022

Recently, as the demand for secondary batteries for electric vehicles has rapidly increased, the efficient production of lithium compounds is attracting great attention. Bipolar membrane electrodialysis (BPED) is known as an eco-friendly, economical, and efficient electrochemical lithium compound production process. Since the efficiency of the BPED depends on the performance of the bipolar membrane (BPM), the selection of the BPM is very important. In this study, the characteristics of BPMs suitable for the BPED for electrochemical LiOH production were derived by comparative analyses of BP-1E (Astom) and FBM (Fumatech), which are the most widely used commercial BPMs in the world. Through systematical evaluation, it was confirmed that reducing membrane ion transfer resistance and co-ion leakage among the characteristics of BPM is the most important, and BP-1E has better performance than FBM in this respect.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.2
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• pp.43-51
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• 2023

In this paper, we introduce the development trends of power devices which is the key component for power conversion system in electric vehicles, and discuss the characteristics of the next-generation wide-bandgap (WBG) power devices. We provide an overview of the characteristics of the present mainstream Si insulated gate bipolar transistor (IGBT) devices and technology roadmap of Si IGBT by different manufacturers. Next, recent progress and advantages of SiC metal-oxide-semiconductor field-effect transistor (MOSFET) which are the most important unipolar devices, is described compared with conventional Si IGBT. Furthermore, due to the limitations of the current GaN power device technology, the issues encountered in applying the power conversion module for electric vehicles were described.

• Korean Journal of Materials Research
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• v.33 no.11
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• pp.497-501
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• 2023

ZnO/Cu/ZnO (ZCZ) thin films were deposited at room temperature on a glass substrate using direct current (DC) and radio frequency (RF, 13.56 MHz) magnetron sputtering and then the effect of post-deposition electron irradiation on the structural, optical, electrical and transparent heater properties of the films were considered. ZCZ films that were electron beam irradiated at 500 eV showed an increase in the grain sizes of their ZnO(102) and (201) planes to 15.17 nm and 11.51 nm, respectively, from grain sizes of 13.50 nm and 10.60 nm observed in the as deposited films. In addition, the film's optical and electrical properties also depended on the electron irradiation energies. The highest opto-electrical performance was observed in films electron irradiated at 500 eV. In a heat radiation test, when a bias voltage of 18 V was applied to the film that had been electron irradiated at 500 eV, its steady state temperature was about 90.5 ℃. In a repetition test, it reached the steady state temperature within 60 s at all bias voltages.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.271-277
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• 2013

Skin pass rolling is a very important process for applying a certain elongation to a strip in the cold rolling and annealing processes, which play an important role in preventing the stretching of the yield point when the material is processed. The exact prediction of the rolling force is essential for obtaining a given elongation with the steel grade and strip size. Unlike hot rolling and cold rolling, skin pass rolling is used to apply an elongation of within 2% to the strip. Under a small reduction, it is difficult to predict the rolling force because the elastic deformation behavior of the rolls is complicated and a model for predicting the rolling force has not yet been established. Nevertheless, the exact prediction of the rolling force in skin pass rolling has gained increasing importance in recent times with the rapid development of high-strength steels for use in automobiles. In this study, the possibility of predicting the rolling force in skin pass rolling for producing various steel grades was examined using foil rolling theory, which is known to have similar elastic deformation behavior of rolls in the roll bite. It was found that a noncircular arc model is more accurate than a circular model in predicting the roll force of high-strength steel below TS 980 MPa in skin pass rolling.