• Journal of the Korean Institute of Telematics and Electronics
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• v.16 no.6
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• pp.11-15
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• 1979

Electrical switching phenomenon was observed in the Fe2O3-Bi2O3 system for the sintering temperature range of 700$^{\circ}$~85$0^{\circ}C$ for DC conductivity measurements of these sinterd materials in the ambient temperature range of 30$^{\circ}$~20$0^{\circ}C$ have shown that the conductivity increases with increasing the sitering temperature and ambient temperature. The formation of the current channel and the experimental evidence of the dependence of switching threshold voltage on the ambient temperature, strongly indicates that the main electrical switching mechanism of sintered Fe2O3-Bi2O3 is thermal effect.

• Proceedings of the KIPE Conference
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• 1998.11a
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• pp.44-48
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• 1998

In the buck-boost DC-DC converter which is used at a certain situation such as in factories where loads often change a lot, the switches in the device make big energy loss in operating at Buck-Boost Mode due to hard switching and are affected by lots of stresses which decrease the efficiency rate of the converter. In order to improve this problem, to decrease the loss of snubber and switching, it has been investigated that zero voltage switching mode and zero current switching mode which make the operation of switches with soft switching. For the more sophisticated and advanced device, this paper is presented the Partial Resonant Soft Switching Mode Power Converter which is adapted the power converter having the partial resonant soft switching mode, that makes switches operate when the resonant current or voltage becomes zero by making the resonant circuit partially at turning on and off of the switches with suitable layout of the resonant elements and switch elements in the converter. Also, this paper includes the analysis and simulation of the Partial Resonant type Buck-Boost Chopper.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.268-275
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• 2015

This paper proposes a method of switching to improve power loss for the single-phase three-level NPC inverter. The conventional switching methods, which are called as the bipolar and unipolar switching methods, are used for single phase inverters using three-level topology. However, these switching method have disadvantage in the power loss. Because all of the switch are operated. To reduce the power loss of the three-level NPC inverter, clamp switching method is introduced in this paper. This way, one of the lag is fixed that switching loss is reduced. This paper analyzes and compares power losses of unipolar method and clamp method. The validity of the power loss analysis is verified through the simulation and experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.2
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• pp.30-39
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• 1989

Variable structure control (VSC) systems control the state vectors using sliding regime (SR) constructed switching logic, switching plane and control law. Saturation function switching logic is used to improve the drawback which occurs in traditional sign function switching logic. Switching plane with time-varying parameter is proposed to improve the drawback which occurs in switching plane with constant parameter and it is suggested the control law which has time-varying parameter. The stability of VSC system controlled by proposed time-varying SR is discussed, and the good control behavior was shown through computer simulation using proposed SR.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.214-220
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• 2008

Most of converter system could obtain almost unity power factor and make input current sinusoidal waveform, but they have many problems, such as electromagnetic interference and switching losses caused by switching noise in main switch. To solve these problems in hard switching PFC converter, soft switching converter using a resonant between capacitor and inductor is invented In this paper, advantages and disadvantages of conventional ZVT(Zero-Voltage-Transition) soft switching converter using a auxiliary resonant circuit is discussed. Then Improved ZVT soft switching converter proposed. This improved ZVT converter's operation principal, specific property, design scheme of main are described. From Simulation and experiment results of conventional ZVT soft switching and improved ZVT soft switching converter with active snubber, characteristics of the converter are confirmed.

• Fashion & Textile Research Journal
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• v.10 no.6
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• pp.900-906
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• 2008

This study investigated factors influencing consumers' switching behavior in apparel purchasing situation. As customer switching behavior is getting more and more important, a considerable amount of researches have focused on how service providers acquire and sustain customers. The field of customers' switching behavior has been relatively well researched over the years, at least from the perspective of the cultural value(Chemyen). The purpose of this study is to understand customer' switching behavior to relationship benefits and Chemyeon. The sample was consisted on 182 females over 20 years old living in Ulsan and Gyungnam province. The data was analyzed by frequency, reliability, factor analysis, and structural equation model analysis. Findings showed that Chemyeon was shown to reduce customer' switching behavior. Also, three factors of relationship benefits(economic benefit, social·psychological benefit, and special treatment benefit) had negative effects on customer' switching behavior.

• Korean Management Science Review
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• v.10 no.1
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• pp.107-125
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• 1993

Modern telecommunication switching systems are SPC(Stored Program Control) machines handling voice, data and other kinds of traffic, in an environment which tends to be fully digital switching and transmission. The throughput of such systems is determined by the real time capacity of its centralized or distributed control processors and by the traffic capacity of the switching network. Designers must verify the traffic and call processing capacity of the switching system and check its performance under traffic load before it is put into service. Verification of traffic and call processing capacity of switching systems is one of the problems treated by teletraffic studies ; teletraffic studies are based on stochastic process, queueing theory, simulations and other quantitative methods of decision making. This study suggests the general methodology to evaluate the throughput and performance of the ISDN switching system. TDX-10 ISDN switching system are employed to give illustrative examples of the methodologies discussed in this study.

• ETRI Journal
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• v.18 no.3
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• pp.107-125
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• 1996

In this paper, we define the general requirements of ATM switching systems such as scalability, distributed fashion, and modularity. Also we propose a practical implementation of a scalable ATM switching system whose capacity can be easily expanded. Firstly, the architecture of the system is discussed with an emphasis on system scalability, modularity of subsystems and the simple control network of the design requirements. Secondly, we suggest the three types of distributed call/connection control schemes that are suitable for our switching system. We also estimate their call processing capacity on the average and make a comparison of them under the various system architectures. Since our scalable switching system can be constructed to perform the call processing functions on the various levels of the system capacity, it has much adaptability at the various evolution phases or regions of the network environment.

• Journal of Korean Institute of Industrial Engineers
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• v.13 no.2
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• pp.17-34
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• 1987

Modern telecommunication switching systems are SPC (Stored Program Control) machines handling voice, data and other kinds of traffic, in an environment which tends to be fully digital switching and transmission. The throughput of such systems is determined by the real time capacity of its centralized or distributed control processors and by the traffic capacity of the switching network. Designers must verify the traffic and call processing capacity of the switching system and check its performance under traffic load before it is put into service. Verification of traffic and call processing capacity of switching systems is one of the problems treated by teletraffic studies; teletraffic studies are based on stochastic process, queueing theory, simulations and other quantitative methods of decision making. This paper reviews the general methodologies to evaluate the throughput and performance of the digital switching system. TDX-10, which is a fully digital switching system under development in ETRI, is employed to give illustrative examples of the methodologies discussed in this paper.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.12
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• pp.713-721
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• 2003

This paper analyzes the switching overvoltage occurred on 345kV underground power cable system as well as combined transmission system using EMTP. Cable length and closing time, preinsertion resistance have effect on switching overvoltage. Therefore, this paper analyzes the switching overvoltage occurred on conductor and sheath with change of those parameters. Specially, the cross bonding position becomes discontinuity point because of the difference between surge impedance of metal sheath and that of lead cable. Thus, the transmission and the reflection of traveling wave complexly occur at this connection point. According to these influences, voltage between sheath and earth as well as voltage between joint boxes rise. Time to crest point of switching overvoltage is longer than lightning overvoltage. Even though the voltage induced by switching surge is smaller than lightning surge, that voltage may have serious effect on the metal sheath. Therefore, this paper also analyses the reduction effect of switching overvoltage when the preinsertion resistance of circuit breaker is considered.