• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.145-153
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• 2016

Cable TV with largest subscription base in pay TV market has difficulty in managing the task of digital switch over. This study analyzed the factors in delay of cable TV switch over and examined the impact of pay TV market structure and competition. The delaying factors turned out to be the lack of incentives and resources of cable TV operators, insufficient policy measures and acceptance tolerance issues of subscribers. Since cable TV operators with monopolistic status in pay TV market had continuous profit from analog service, they were not responsive to digital switch over which requires additional investment. Policy measures including support for the low income household and mandatory cut-off point for stopping analog broadcasting. Subscriber's willingness to accept digital broadcasting in terms of price sensitivity and preference for convenient operation also played a role. Introduction of IPTV in pay TV market influenced the speed of digital switch over of cable TV operators. MSOs with economies of scale showed higher digital switch over rate than independent SO.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.100-109
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• 2017

This paper proposes performance improvement schemes for sensorless PMSM control drive using a four-switch three-phase inverter (so-called B4 inverter). In the proposed scheme, the back-EMF estimation-based sensorless control algorithm is used to control the brushless PMSM without position sensors. In order to have stable operation, this paper presents a gain adjustment scheme that compensates the reduction of stable sensorless operation range as long as the rotor speed increases. In B4 topology, the center point of dc-link capacitors is connected to 3-phase load, and it is prone to have the load current distortion. Hence, to mitigate this problem, a distortion compensation scheme by modifying voltage commands using measured dc-link potentials is proposed in this paper. The validity of the proposed method is evaluated by simulations and experiments.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.49-52
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• 2007

In this paper, we proposed a design photovoltaic generation systems with SEPIC-Flyback converter. The SEPIC-Flyback converter is operated to SEPIC converter the state turn-on of the switch and the state turn-off the switch is operated Flyback converter. Therefore application rate of the core increases and voltage stress of switch and transformer decreases with active clamp operation. Also we performed MPPT(Maximum Power Point Tracking) control for efficient working of Photovoltaic Dower generation system.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.248-250
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• 2005

This paper suggests a new type of 4-switch inverter for switched reluctance motor drives. 4-switch Inverter topology is studied to provide possibility for the realization of cost of 3-phase SRM drive system. We used Y-connection and two-phase exciting method. For effective utilization of the developed system, a direct current controlled PWM scheme is designed and implemented to produce the desired dynamic. We solve to balance the neutral point of Y-connection by the direct current controlled PWM and examine the performance of proposed system. With the algorithm and developed control scheme, is expected that the proposed system can be widely used in commercial applications with a reduced system cost.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.3
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• pp.535-541
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• 2009

In this paper, we present the improvement on the performance of driving part for single-phase MJ81 switch point machine which has been developed for localization. The single-phase motor's specification and reliability for speed and safety improvement of conventional line was investigated in "Development project for Speed-up on Conventional Line" We systemized the test procedure fur single-phase motor by investigating the feasibility for localization and the specification of function and performance. Also, we developed appropriate technology and proved the durability of the single-phase driving motor by executing synthesis test over 200,000 times.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.7
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• pp.74-80
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• 2006

This paper describes a solar energy conversion strategy is applied to grid-connected single phase inverter by the maximum power point of conversion strategy. The maximum power point of tracking is controlled output power of PV(photovoltaic)modules, based on generated circuit control MOSFET switch of two boost converter for a connected single phase inverter with four IGBT's switch in full bridge. The generation control circuit allows each photovoltaic module to operate independently at peak capacity, simply by detecting of the output power of PV module. Furthermore, the generation control circuit attenuates low-frequency ripple voltage. which is caused by the full-bridge inverter, across the photovoltaic modules. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.164-171
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• 2006

In this paper, the fault tolerant system for BLDC motor has been proposed to maintain control performance under an open switch fault of inverter. The fault identification is proposed to two methods, which are using the difference between reference and actual current, and adding voltage sensors across lower legs of inverter. The reconfiguration scheme is achieved by the four-switch topology connecting a faulty leg to the middle point of DC-link using bidirectional switches. The proposed fault tolerant system quickly recovers control performance by short fault detecting time and reconfiguration of system topology. Therefore, continuous free operation of the BLDC motor drive system after faults is available. The superior performance of the proposed fault tolerant system is proved by simulation.

• Journal of IKEEE
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• v.7 no.2 s.13
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• pp.181-187
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• 2003

In high speed packet switching network, packet service by priority scheme prefer to QoS. Efficient packet service according to the priority scheme in high speed packet switch is a key point. Therefore development of priority service algorithm in the packet switch is very important. In this paper, we proposed W-iSLIP algorithm that service time take queue length into consideration and compared the proposed W-iSLIP algorithm to other previous proposed algorithm through simulation. Simulation results show 2.6% performance elevation in average delay, and 34.6% performance elevation in priority service.

• The Journal of Information Systems
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• v.30 no.4
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• pp.43-69
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• 2021

Purpose Although companies occupied the network market take the advantageous position first and can be successful in securing users over a certain size, it is important to satisfy the customers' demand and prevent the outflow of users toward a new alternative SNS. What is more, there are frequent changes in the flow of users toward new SNSs. Despite these dynamic market circumstances, there is a lack of research to explain the switching behaviors of SNS users. Design/methodology/approach The objective of this study is to explain and verify a specified migration theory(Push-Pull-Mooring model) focused on SNS fatigue in the psychological point of view, as well as reviewing previous studies on functional and technical characteristics of SNSs themselves. Moreover, this study tried to highlight factors affecting users actual SNS switch rather than their switching intention. Findings According to the statistical analysis, the most influenced pull factor to switch SNS was the alternative attractiveness. On the other hand, undesired relationship burden, service innovation and important mooring factors to prevent users' SNS switch. This study has a significant contribution to the theory, which analyzed users' actual SNS switch, and examined SNS users' psychological factors(SNS fatigue), reviewing the characteristics of existing services. To secure more users and to keep them, companies providing social network service need to develop differentiated strategies by analyzing psychological characteristics of various users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2B
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• pp.120-130
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• 2011

Recently the multicast based contents transmission is rapidly increasing due to the various multimedia services and the importance of switching technology to handle it is increasing as a consequence. Though the CICQ architecture has advantages that reduction of HoL blocking probability and simple scheduling using cross point buffer, it has disadvantage that the processing rate of multicast traffic can be significantly degraded corresponds to the traffic load increment. Several schemes have been proposed to solve this problem however they still can't provide enough processing ratio for multicast traffic. Therefore this paper proposes the BA cell assignment scheme and the VT scheme, and the processing rate of multicast traffic can be guaranteed by reducing the HoL blocking probability of multicast traffic and reservation of cross point buffer. Also simulation results verify that using the proposed scheme, the QoS of multicast service can be improved.