• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.905-915
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• 2015

Two PWM techniques using space vector pulse-width modulation (SVPWM) are proposed for a two-phase permanent magnet synchronous motor (PMSM) driven by a two-phase eight-switch inverter. A two-phase motor with two symmetric stator windings is usually driven by a two-phase four-, six-, or eight-switch inverter. Compared with a four- and six-switch inverter, a two-phase eight-switch inverter can achieve larger power output. For two-phase motor drives, the SVPWM technique achieves more efficient DC bus voltage utilization and less harmonic distortion of the output voltage. For a two-phase PMSM fed by a two-phase eight-switch inverter under a normal SVPWM scheme, each of the eight PWM trigger signals for the inverter have to be changed twice in a cycle, causing a higher PWM frequency. Based on the normal SVPWM scheme, two effective SVPWM schemes are investigated in order to reduce the PWM frequency by rearranging four comparison values, while achieving the same function as the normal PWM scheme. A detailed explanation of the normal and two proposed SVPWM schemes is illustrated in the paper. The experimental results demonstrate that the proposed schemes achieve a better steady performance with lower switching losses compared with the normal scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3680-3693
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• 2022

The handover procedure of IEEE 802.11 wireless local area networks (WLANs) introduces significant delay, which can degrade the quality of service (QoS) especially for delay-sensitive applications. Although studies have been conducted to support handover in SDN-based WLAN, there is no research to reduce the channel scanning procedure that takes up the most delay time in the handover process. The channel scanning procedure is essential to determine the appropriate access point (AP). To mitigate this problem, this paper proposes a SWITCH: SDN-WLAN integrated handover scheme for QoS-Guaranteed mobile service. In SWITCH, each AP periodically broadcasts beacon frames through different channels in a predetermined order that includes the operating channel information of the AP. This allows mobile stations (MSs) to receive the beacon frames of nearby APs, and therefore they can determine the appropriate APs for handover without the channel scanning procedure. By reporting the information of the newly moved AP to the SDN controller, a flow rule is installed in advance to provide fast handover, and packet loss is reduced by buffering data destined for MS. In addition, the proposed scheme can adaptively operate SWITCH to consider the user location and QoS requirement of flow to save radio resource overhead. Performance evaluation results demonstrate that SWITCH can reduce the handover delays, flow table utilization ratio and radio resource overhead while improving the network throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1890-1906
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• 1997

A new ER feedback switch control algorithm, called EMRCA(Explicit Max-min Rate Control Algorithm), to control the ABR services traffic in the ATM networks, is proposed in this thesis. This scheme was interpreted the ACR variation residing on between a transient state and a stable state using the two thresholds that is the $TH_{high}$ and $TH_{low}$ in the queue to detect switch nodes congestion, and decreased the difference of minimum and maximum ACR all active connection to enhance the line bandwidth utilization. The proiposed scheme used a minimum and maximum rate of all active connections to select the connection whose the congestion rate inveoked, and uses a congestion detection mechanixm to prevent some potential cogestion by regulating selected contection.s The EMRCA scheme showed ACR variation more stable that the EPRCA scheme, also reduced buffer size of the switch, and achieved higher link utilization than the EPRCA scheme.

• ETRI Journal
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• v.25 no.1
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• pp.34-40
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• 2003

This paper considers a TMN-based management system for the management of public ATM switching networks using a four-level hierarchical structure consisting of one network management system, several element management systems, and several agent-ATM switch pairs. Using Jackson's queuing model, we analyze the effects of one TMN command on the performance of the component ATM switch in processing local calls. The TMN command considered is the permanent virtual call connection. We analyze four performance measures of ATM switches- utilization, mean queue length and mean waiting time for the processor directly interfacing with the subscriber lines and trunks, and the call setup delay of the ATM switch- and compare the results with those from Jackson's queuing model.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.73-74
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• 2016

This paper proposes a wide output range AC/DC converter for a rechargeable battery of electric vehicle. In the proposed wide output range AC/DC converter for rechargeable battery of electric vehicle, the main transformer in the DC/DC stage is divided by two. Therefore, if the switch is connected to the middle tap, then half of the maximum voltage is applied. Otherwise, it can be applied the full range of the high voltage by connecting the switch to the whole tab. And also, it is designed to have a wide output voltage range by applying Vin/2 made by changing the full-bridge to half-bridge by using the bridge change switch of the input stage. As it can be supplied the wide range output voltage with a single module, it has the advantage of space utilization and cost reduction effect.

• ETRI Journal
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• v.24 no.2
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• pp.117-130
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• 2002

Due to its salient features, the optical burst switch is becoming a key technology for the optical Internet. Within this technology, the survivability issue in the optical Internet has to be addressed because a simple failure causes severe damage to the huge amount of data carried in optical fiber. In this paper, we introduce a restoration procedure that can provide good survivability in the optical burst switch (OBS)-based optical Internet. OBS restoration can survive various types of network failure while maintaining good network performance. We propose novel restoration mechanisms, namely, "temporary Label Switched Path (LSP)" and "bossy LSP," to enhance restoration time and network utilization. The simulation results verify that the proposed OBS restoration achieves good network performance and provides good network connectivity as well.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.318-328
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• 2011

Stage-level reconfigurable chip multiprocessor (CMP) aims to achieve highly reliable and fault tolerant computing by using interwoven pipeline stages and on-chip interconnect for communicating with each other. The existing crossbar-switch based stage-level reconfigurable CMPs offer high reliability at the cost of significant area/power overheads. These overheads make realizing large CMPs prohibitive due to the area and power consumed by heavy interconnection networks. On other hand, area/power-efficient architectures offer less reliability and inefficient stage-level resource utilization. In this paper, I propose a hierarchical multiplexing interconnection structure in lieu of crossbar interconnect to design area/power-efficient stage-level reconfigurable CMP. The proposed approach is able to keep the reliability offered by the crossbar-switch while reducing the area and power overheads. Experimental results show that the proposed approach reduces area by up to 21% and power by up to 32% when compared with the crossbar-switch based interconnection network.

• 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.

• Health Policy and Management
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• v.23 no.2
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• pp.112-123
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• 2013

Background: Under the risk of financial sustainability of National Health Insurance, Korean government attempted a series of regulations over pharmaceutical prices. The first price-cut was implemented to the hyperlipidemial treatments, and the prices of statins were reduced on 15th, April in 2009. The purposes of this study are 1) to investigate the impact of this price-cut on pharmaceutical expenditure, and 2) to identify the factors associated with drug-switch among statins. Methods: Using the national patients sample data, this study conducted time series analysis on the expenditures, prices, and volumes of statin drugs. To understand the factors associated with drug-switch, the multinomial logit model was analyzed at the patients level. Results: The results of time series analysis demonstrated that the price-cut of hyperlipidemic medicines did not lead to the reduced expenditure, suggesting the increased volume was the major cause. The multinomial logit analysis identified the switch of healthcare provider as the significant factor that was highly associated with drug-switch, implying the physicians' preference was the major motivation of drug-switch. Conclusion: Without control of utilization, price regulation itself could not reduce pharmaceutical expenditure. This suggests that the pharmaceutical regulations should be implemented on the basis of understanding of provider behaviors. The findings of this study will form the first step for further empirical studies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.162-169
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• 2005

Network traffic measurements show that the data traffic on packet switched networks has the self-similar features which is different from the traditional traffic models such as Poisson distribution or Markovian process model. Most of the call admission control researches have been done on the performance analysis of a single network switch. It is necessary to consider the performance analysis of the proposed admission control scheme under interconnected switch environment because the data traffic transmits through switches in networks. From the simulation results, it is shown that the call admission control scheme may not operate properly on the interconnected switch even though the scheme works well on a single switch. In this parer, we analyze the cell loss probability, utilization and self-similarity of output ports of the interconnected networks switch by using shared buffer memory management schemes and propose the new call admission control scheme considering the interconnected network switches under self-similar traffic environments.