• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1729-1734
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• 2018

Recently, interest in environmentally friendly transportation systems has been increasing, and study on railway systems has been aggressively conducted. Therefore, lots of studies have been done in railway advanced countries to improve performance of PWM converter. The research on the PWM converter for railway vehicle was mainly carried out on the converter mounted on railway vehicle such as the high-speed railway and metropolitan railway. In also, a lot of study has been carried out to improve converter performance installed in the ground. The high-capacity transform used in this paper converted from AC 22.9kV to AC 590V. The converter changed from AC 590V to DC 950V. In general, in the case of rectifier, the DC power supply system has a negative impact on inverter control characteristics because it can not avoid the pulsating component. In this study, it was performed current control for high-capacity converter using Matlab Simulink. The PWM converter is normally performed through the voltage and current at starting mode, powering mode, and braking mode. In the light-load test and the on-line test, we have studied for the PWM converter characteristics. Using this research, we have founded that the converter has excellent performance.

• Journal of Distribution Science
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• v.22 no.1
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• pp.25-36
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• 2024

Purpose: The study attempts to explore the operational performance of the existing Malaysian logistics companies and the extent of their adoption of digitalization. The role of digitalization in enhancing the performance of companies in the logistics industry in Malaysia, for value creation, is the topic of study. Research design, data and methodology: A qualitative research method with a semi-structured interview approach was applied and judgmental sampling was used as the sampling technique to collect data. The research has chosen nine companies in the logistics industry in Peninsular Malaysia, with the interviews aimed at eleven members of top and middle-level management. Data analysis was performed using logical system techniques to examine and evaluate data, reorganizing feedback, comparing it with literature, and transforming it into structured, valuable information after interviews. Results: The study revealed mixed opinions on digitalization in logistics, despite its potential benefits such as improved operational efficiency, real-time information, and customer service. However, high costs may hinder financial performance and require revisions due to stakeholder involvement. Conclusions: The Malaysian logistics industry's adoption of digitalization is gaining traction, with most companies satisfied with their status. However, challenges like cost and inefficiency persist, prompting calls for government support to improve efficiency and reduce costs while ensuring sustainable transportation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1611-1617
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• 2013

Information about trafficability or the condition of road with regard to its being traveled over by vehicles is one of the most critical factors for roadway operation in winter. Specifically, when traveling on snowy or icy surfaces, the traction force varies per vehicle type including tire types, geometric characteristics of roads, and conditions of road surfaces. In general, front-wheel drive or four-wheel drive vehicles have better traction performance on snowy or icy surface than rear-wheel drive vehicles, and the latter type vehicle causes more serious traffic congestion when there is unexpected snowfall. Thus, traffic information regarding trafficability with respect to vehicle types, geometric characteristics of roadway sections, and roadway surface conditions can provide a foundation to make a decision whether to use the associated roadway sections for roadway operators as well as users. Based on the preceding premise, the objective of this study is to present a methodology for developing a trafficability index with respect to vehicle types, geometric characteristics of roadway sections, and roadway surface conditions.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.254-259
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• 2009

DC transit system has been adopted in the metropolitan area, Korea since 1974. Electric multiple (EMU) in this system always reiterates that acceleration and retardation. When EMU decelerates using electric breaking, regenerative power occurs. Regenerative power can be consumed in vicinity EMU on the same line or in resistor. If DC transit system has inverter for reusing regenerative power, Energy efficiency in DC transit system and the replacement cycle of brake shoe in EMU will be increased and dust due to mechanical braking decreased. This paper present the developed inverter for regenerative power and its test equipment. Test for developed inverter is performed at test equipment and is divided into three items, which are regeneration mode, active filter mode, and system link test.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.380-386
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• 2008

The development of a new railway vehicle is under progress through the Next Generation High-Speed Rail Development Project in Korea. Its aim is to develope fundamental technology of the vehicle that can run over 400km/h. The new distributed traction bogie system, 'HEMU'(High-speed Electric Multiple Unit), will be used and is different from that of previously developed high speed railway vehicles. Previous vehicles adopted push-pull type system, which means one traction-car drives rest all of the vehicle. Due to the difference, investigation on dynamic behavior and its safety evaluation are necessary, as a part of verification of the design specification. In the paper, current progresses of researches are presented. And the High-Speed Railway vehicle system is evaluated for a dynamic characteristic simulation. Proper dynamic models including air-suspension system, wheel-rail, bogie and car-body is developed according to the vehicle simulation scenario. The basic platform for the development of dynamic solver is prepared using nodal, modal coordinate system and wheel-rail contact module. Operating scenario is prepared using commercial dynamic analysis program and used for development of dynamic model, which contains many parts such as carbodies, bogies and suspension systems. Furthermore, international safety standard is applied for final verification of the system. Finally, the reliability of the dynamic model will be verified with test results in the further researches. This research will propose a better solution when test results shows a problem in the parts and elements. Finally, the vehicle that has excellent performance will be developed, promoting academic achievement and technical development.

• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.897-907
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• 2022

The purpose of this study is to develop a self-propelled underground crop harvester and its performance was evaluated by measuring the load during actual potato harvesting operations. This study was conducted at a constant working speed of 1 km·h^-1. A load measurement system was installed to measure the actual load and the required working power was analyzed. A hydraulic pressure sensor was also installed to measure the hydraulic pressure. The required hydraulic power was calculated using the hydraulic pressure and flow rate. The results showed that the engine speed, torque, and power during harvesting operation were in the range of 845 - 1,423 rpm, 95 - 228 Nm, and 9 - 31 kW, respectively. Traction power, excluding the hydraulic pump of the tractor and power take-off (PTO) output, was in the range of 9 - 28 kW, and it was confirmed that it occupies a ratio of 16.2 to 50% of the engine rated output. The engine can supply the minimum required traction power to move the vehicle. This means that the engine used in this study could be down-sized to be suitable for an underground crop harvester. In this study, the gear stages of the tractor were not considered. This research thus shows the possibility of developing a self-propelled underground crop harvester.

• Journal of Power Electronics
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• v.5 no.1
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• pp.45-54
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• 2005

This paper presents an application of SR drives for LSEV's(Low Speed Electric Vehicles) which are used for golf and leisure. Two types of 5[HP] SRM's and its drive system are designed and tested. In order to be energy saving and have effective braking during deceleration, a multi-level inverter is proposed. For the precise switching angle control, a new type of analog encoder is proposed. A current control is adopted for soft starting and an angle control is adopted at high speed to increase efficiency. Drive characteristics and performance are shown with test results.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.602-607
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• 2004

Accurate and quick positioning of the throttle valve in driving situation is required to implement the Traction Control System(TCS). Also, unlike a conventional throttle valve which is connected to the accelerator directly by a wire, an Electronic Throttle Valve(ETV) is driven by a DC motor and can move dependently upon the accurate position of the accelerator. In the research, the Electronic Throttle Body(ETB) and Controller for TCS application was developed. In order to drive the DC motor, the developed controller was built and interfaced to the ECU and ETB. The PID position control algorism and developed systems are designed to realize the robust tracking control of the ETV. Actual vehicle tests with these systems and PID position control algorithm. Finally, the performance of the proposed those are evaluated with the experimental studies.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.6
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• pp.141-148
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• 1998

A loader is construction & road or agricultural machinery for lifting, moving, and mixing. This study deals with the agricultural mini loader for stock raising farming. The performance of the machine is established by pulling power, working lifting capacity, and minimum circling radius, etc. Also, driving easiness and endurance are very important in manufacturing. Thus, this study has developed the loader with the 4-wheel driving equipment by gear transmission, the 4-wheel steering equipment by power handle steering type, and the equipment making four wheels touch simultaneously on the rugged ground. The developed loader having these functions was very fit in a small cattle shed or a rugged ground. This study is divided into two parts; (I) development of 4WS transmission and (II) construction of the loader by 4WS system and other equipments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.313-317
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• 2005

Precision motor dynamometer is requiring for nano positioning control performance recently. Particularly, linear motor is using rapidly and the dynamometer needs is increasing. In this study, a precision control dynamometer is designed using MR (Magnetic Rheological) damper. The ultra precision motor system including the driver and controller is tested using the MR damper dynamometer. This dynamometer is able to measure torque for rotary motor or traction force with linear positioning accuracy for linear motor system.