• Journal of the Korean Society of Safety
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• v.22 no.3 s.81
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• pp.88-97
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• 2007

A point based speed enforcement system(SES) has been widely used in roadways to reduce the operating speeds and potential traffic accidents. Recently, the needs for introudcing new SES using point-to-point speed measurement was presented, however, no practical guidelines or justification of the system was available. This study investigated the effectiveness of the current SES and introduction of the new SES through user interview survey method. Survey results showed that 33% of respondents were unsatisfactory to the current way of SES operation, which was 11% higher than satisfactory respondents, and about 70% of the respondents supported the introduction of point-to-point based SES operation. A majority of respondents preferred the straight roadway segment, bridge and tunnel, and curved roadway segment for a start application site with the segment length of 1-5 km long. Using these survey results, an introduction scheme was discussed in terms of legal bases, installation criteria, and operational guidelines.

• Journal of Power Electronics
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• v.16 no.3
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• pp.915-924
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• 2016

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.282-286
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• 2005

Contents of these treatise propose method to embody station addition and passivity point correction. That store in TCMS's memory being downloaded all train running path data that is consisted of name of station and station code, departure station, destination station, train number, running time through PCMCIA memory card. Search relevant running path data and current station, destination station, the next station start time present to TCMS's display. In case it is no received information of station, device that do function of passenger broadcasting and pilot light does not act. This time, if input information of current station, relevant device does point revision.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.301-302
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• 2014

This paper describes four switch three-phase Z-source rectifier with improved switching characteristics. This configuration has some advantages switching loss and optimal drive circuit. The rectifier has buck-boost function by shoot-through state. Also, the rectifier has the advantage of decreasing inrush current in start-up and transient states. In order to reduce harmonics PWM modulation technique with a variable index has been suggested. Four switch three-phase Z-source rectifier with improved switching characteristics can output stable DC voltage at the same time decreasing the system's harmonic current. And also the paper presents an application of DCC method in Z-source rectifier. Principles and dynamics of the system are discussed in detail. After having viewed the results we can confirm that the proposed method is eligible and efficient.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.4
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• pp.115-125
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• 2022

In today's era when the concept of a lifelong job has disappeared, starting a business is an essential consideration for university students not only as an alternative factor in finding employment, but also from the perspective of the entire life. Today, most universities in Korea are operating entrepreneurship education programs, such as entrepreneurship classes as a curriculum, and start-up clubs as a non-curricular program to foster entrepreneurship among university students. In previous studies, entrepreneurship is a factor influencing the entrepreneurship intention. The purpose of this study is to empirically examine the effects of university students' entrepreneurship and the entrepreneurship intention through a entrepreneurship education program (participation in a start-up club, taking an entrepreneurship course) on entrepreneurship behavior. There are some empirical studies on whether entrepreneurship education programs such as participation in startup contests affect the entrepreneurship intention of university students, but not much compared to their importance. It is difficult to find an empirical study examining the effects of entrepreneurship and start-up education programs on entrepreneurship intention and entrepreneurship behavior in domestic and foreign studies. Therefore, in this study, one domestic university that operates a start-up club and a entrepreneurship course was selected and the online questionnaire was distributed to all current students, and the collected 127 questionnaires were used for empirical analysis As a result of the study, first, it was confirmed that initiative and risk-taking, which are sub-factors of entrepreneurship of university students, had a significant positive effect on entrepreneurial intention, respectively, and that innovation did not have a significant positive effect. Second, it was confirmed that university students' participation in a start-up club, a sub-factor of the start-up education program, had a significant positive effect on their entrepreneurial intention, and that taking a start-up course did not have a significant positive effect. Third, it was confirmed that the entrepreneurial intention of university students had a significant positive effect on entrepreneurship behavior. Fourth, it was confirmed that the entrepreneurial intention had a mediating effect between each of the factors of risk-taking, and participation in a start-up club and entrepreneurial behavior. This study suggests that university students can increase their risk-taking, increase their entrepreneurial intention by participating in a startup club, and reach a entrepreneurial behavior through this as a medium.

• Journal of Software Assessment and Valuation
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• v.16 no.2
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• pp.109-115
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• 2020

In this paper, the problem that occurs when negative voltage is generated using an inexpensive buck device in an IT device that is supplied with a single power by an adapter or battery is analyzed. For the cause analysis, the principle of operation of the buck device and the principle of the inverter circuit were examined, and the circuit characteristics of the inverter circuit were analyzed using the buck device. As a result of the analysis, it was confirmed that the inverter circuit using the buck device initially needs a large starting current, and in particular, in the case of a current capacity that is less than the starting current in the circuit that supplies power, it was confirmed that it could fall into a state similar to the latch-up phenomenon. In order to confirm the analysis result, an experimental circuit was constructed and the input current was checked. If the supply current is sufficient, it is confirmed that over-current flows and starts. If the supply current is insufficient, the circuit cannot start and a latch-up phenomenon occurs.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.5
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• pp.378-385
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• 2007

AC PDP has disadvantages that power consumption and sustain voltage are high. An energy recovery circuit for AC PDPs with reduced sustain voltage was proposed to solve these disadvantages. However, the circuit has disadvantage that the switching elements are performed hard switching at the start point of discharge and sustaining region. The reason is that the panel voltage is lower than sustain voltage at that point. In this paper, we propose the improved driving method that switching devices are operated with ZVS by using CIM(Current Infection Method) also at that point. CIM region is designed by theoretical circuit analysis. Finally, the validity of the proposed driving method is verified by the simulations and experimentation.

• Journal of Magnetics
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• v.18 no.4
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• pp.487-493
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• 2013

The automotive industry is showing widespread interest in belt-driven electric motor-assisted (e-Assist) systems. A belt-driven assist system (BAS) starts and assists the combustion engine in place of the conventional generator. In this study, a water-cooled wound rotor synchronous motor (WRSM) for the e-Assist system was designed and analyzed. The performance of the WRSM was compared with that of an interior permanent magnet synchronous motor (IPMSM). The WRSM efficiency can be improved for the BAS by adjusting the field flux at high speeds. The field current map to obtain the maximum efficiency based on the speed and torque was developed. To control the field flux via field current control in the WRSM, a general H-bridge circuit was added to the WRSM inverter to get the rapid current response in the high-speed region; the characteristics were compared with the chopper circuit. A WRSM developed for the belt-driven e-Assist system and a prototype 115 V power electronic converter to drive the WRSM were tested with a 900 cc combustion engine. The test results showed that the WRSM-type e-Assist system had good characteristics and could successfully start and assist the 900 cc combustion engine.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.10
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• pp.587-594
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• 2002

A low frequency square wave electronic ballast for the high intensity discharge(HID) lamps using fuzzy logic controller is developed. This electronic ballast consists a buck converter, a low frequency square wave full bridge inverter, a high voltage pulse generator for the HID lamp ignition, an over current protection circuit and an 8-bit microcontroller. The ballast system is operated on the constant current mode during the HID lamp start-up process and the system is operated on the constant power mode during steady state. Experimental results show that the fuzzy logic control operation is carried out successfully by the 8-bit microcontroller PIC16F877 In this electronic ballast system, in spite of the limited control bandwidth caused by low operating speed of the microcontroller, the good performance in the constant lamp current characteristic is obtained. Acoustic resonance of the HID lamps can be effectively avoided because the instantaneous In lamp power is fully constant due to the low frequency square wave drive.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.2
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• pp.156-161
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• 2007

A set of experiments of counter-current flow limit (CCFL) was performed to improve the drawbacks of Wallis' correlation which neglected the effects of channel size, channel length, injection method and the boundary conditions at the inlet of liquid and gas phase. In this study, CCFL was observed by changing the shape of porous plate using air and water. The results show that as the size of porous increases, CCFL with a round shape of the porous plate start to disappear, In this study, the CCFL correlation was calculated and the corresponding CCFL map was developed based on the experimental results.