• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.40-64
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• 2005

Much biochemical information on peroxiredoxins (Prxs) has been reported but a genuine physiological function for these proteins has not been established. We show here that two cytosolic yeast Prxs, cPrxI and II, exist in a variety of forms that differ in their structure and molecular weight (MW) and that they can act both as a peroxidase and as a molecular chaperone. The peroxidase function predominates in the lower MW proteins, whereas the chaperone function is more significant in the higher MW complexes. Oxidative stress and heat shock exposure of yeasts causesthe protein structures of cPrxI and II to shift from low MW species to high MW complexes. This triggers a peroxidase-to-chaperone functional switch. These in vivo changes are primarily guided by the active peroxidase site residue, $Cys^{47}$, which serves as an efficient $'H_2O_2-sensor'$ in the cells. The chaperone function of the proteins enhances yeast resistance to heat shock.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.8
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• pp.743-748
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• 2007

Recently, various types of camera mouse are developed using the image processing. The camera mouse showed limited performance compared to the traditional optical mouse in terms of the response time and the usability. These problems are caused by the mismatch between the size of the monitor and that of the active pixel area of the CMOS Image Sensor. To overcome these limitations, we designed a new input device that uses the face recognition as well as the speech recognition simultaneously. In the proposed system, the area of the monitor is partitioned into 'n' zones. The face recognition is performed using the web-camera, so that the mouse pointer follows the movement of the face of the user in a particular zone. The user can switch the zone by speaking the name of the zone. The multimodal mouse is analyzed using the Keystroke Level Model and the initial experiments was performed to evaluate the feasibility and the performance of the proposed system.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.249-250
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• 2008

본 논문은 고창 전력품질 실증시험장에서 실 계통 연계를 위해 시험 중인 1.5M급 풍력발전 시뮬레이터의 선로정수를 PSCAD/EMTDC를 이용하여 모의하고 선로정수에 따른 풍력발전시스템이 계통에 미치는 영향을 분석하는데 중점을 두었다. 현재 고창에 설치되어있는 전력품질 실증시험장은 22.9kV 급전선에 SSTS(Synchronous Static Transfer Switch)의 한쪽 스위치로 직접 연결되어있으며 다른 한 쪽은 전력계통에서 발생되는 다양한 형태의 이벤트를 발생시키는 SSHG(Sag Swell Harmonics Generator)를 통하여 연결되어있다. 전력품질 향상기기중 하나인 DVR(Dynamic Voltage Restorer)는 SSTS의 부하쪽으로 직렬로 연결되어있으며 delta-wye 변압기를 통해 정류기 부하와 APF(Active Power Filter), 그리고 순저항부하와 유도성부하가 연결되어 있고 또한 SSHG를 통하여 연결된 배전선에는 DSTATCOM(Distribution Static Compensator)가 병렬로 연결되어있다. 본 논문에서는 고창에 있는 풍력발전 시뮬레이터와 동일하게 PSCAD/EMTDC로 구성하였으며 선로정수를 모델링 하기 위해 선로모델을 10Km, 20Km, 30Km, 40Km,로 설정하여 선로정수에 따른 계통영향을 분석하여 풍력발전 시뮬레이터에서 모의가능 한 선로정수 값을 제시한다.

• Journal of Power Electronics
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• v.8 no.4
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• pp.363-370
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• 2008

In this paper, three kinds of PWM strategies for a three-phase current-fed dc/dc converter are proposed and compared in terms of losses and voltage transfer ratio. Each PWM strategy is described graphically and their switching losses are analyzed. With the proposed PWM C strategy, one turn-off switching of each bridge switch is eliminated to reduce switching losses under the same switching frequency. In addition, RMS current through the bridge switches is lowered by using parallel connection between two bridge switches and thus, conduction losses of the switches are reduced. Further, copper losses of the transformer are decreased due to the reduced RMS current of each transformer's winding. Therefore, total losses are minimized and the efficiency of the converter is improved by using the proposed PWM C strategy. Digital signal processor (DSP: TI320LF2407) and a field-programmable gate array (FPGA: EPM7128) board are used to generate PWM patterns for three-phase bridge and clamp MOSFETs. A 500W prototype converter is built and its experimental results verify the validity of the proposed PWM strategies.

• Journal of Power Electronics
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• v.13 no.4
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• pp.636-646
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• 2013

A single-phase tapped-inductor boost converter has been proposed previously. However, detailed characterization and performance analysis were not conducted. This paper presents a detailed characterization, performance analysis, and design expressions of a single-phase tapped-coupled-inductor boost converter. Expressions are derived for average and RMS input current as well as for RMS input and output capacitor current ripple. A systematic approach for sizing the tapped-coupled inductor, active switch, and output diode is presented; such approach has not been reported in related literature. This study reveals that sizing of the inductor has to be based on current ripple requirement, turns ratio, and load. Conditions that produce discontinuous inductor current are also discussed. Analysis of a non-ideal converter operating in continuous conduction mode is also conducted. The expression for the voltage ratio considering the coupling coefficient is derived. The suitability of the converter for high-voltage step-up applications is evaluated. Factors that affect the voltage boost ratio are also identified. The effects of duty ratio and load variation on the performance of the converter are also investigated. The theoretically derived characteristics are validated through simulations. Experimental results obtained at a low power level are included to validate the analytical and simulation results. A good agreement is observed among the analytical, simulation, and experimental results.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.1-6
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• 2008

The performance of shock absorber is directly related to the car behavior and performance, both for handling and comfort. Most of compact car are assembled the passive shock absorber for cost effect but some of compact driver want better performance of shock absorber than standard parts. Therefore, they want the semi-active suspension control system instead of standard damper system. But they only can change the mechanical damping control shock absorber at A/S market. The mechanical damping control shack absorber can not vary the damping force in driving condition so they do not satisfy the mechanical damping control shock absorber system. In this study, electrically damping force controlled shock absorber system is developed based on the mechanical damping force control damper system. This system can vary damping force by switch on dashboard in driving condition. And, this system can satisfy the requirement of tuning market. Therefore, it is expected the system to show the engineering capability of korean damper company and to increase export market share to oversea damper market.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.1
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• pp.9-15
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• 2018

This study investigates a bidirectional quasi-Z-source inverter (Bq-ZSI) system with bidirectional power transfer capability and a modified space vector modulation scheme for reducing the ripple of the inductor current. By replacing the diode in the impedance network with an active switch, the power flow can be bidirectional. The average inductor current of the Bq-ZSI network is negative in the regenerative braking mode, thereby regenerating the power. In addition, modified space vector modulation scheme is applied to the Bq-ZSI to control shoot-through time effectively. A 5 kW prototype is built and tested to implement the proposed system. Experimental results show that the Bq-ZSI system is capable of regenerative braking of the induction motor and that the modified space vector modulation method is efficient.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.838-848
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• 2018

This paper proposes a single-phase buck-boost AC-AC converter. It consists of three legs with six switching units (each unit is composed of an active switch and a diode) and its input and output ports share a common ground. It can provide buck-boost voltage operation and immune from shoot-through problem. Since only two switching units are involved in the current paths, the conduction losses are low, which improves the system efficiency. The operation principle of the proposed circuit is firstly presented, and then, various operation conditions are introduced to achieve different output voltages with step-changed frequencies. Additionally, the parameters design and comparative analysis of the power losses are also given. Finally, experimental results verify the correctness of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.129-138
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• 2018

Previous single-phase transformerless inverters used active bypass switching circuits that need auxiliary power switches to minimize ground leakage current. However, switching and gate driving losses are increased due to the use of additional power switches. To cope with this drawback, this work proposes a transformerless inverter using a passive bypass filter without any auxiliary power switch. The operation and control of the proposed inverter are described. The ground leakage current characteristics are analyzed for the proposed inverter with the passive bypass filter. The experimental results of the proposed inverter for a 1.0kW prototype system are presented.

• Journal of the Korea Safety Management & Science
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• v.11 no.1
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• pp.43-49
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• 2009

This study set three kinds of situation and observed the various states such as carbonization by experimenting damages by fire of electric iron. The results of this study are as follows: The fire did not occurred when the unpowered iron over mattress and cotton shirts was com busted completely by external flame because the temperature of surface of soleplate and mattress did not reach the minimum ignition energy and when the powered electric iron over mattress and cotton shirts was left for an hour with its temperature dial set to high because the temperature of combustibles did not reach the minimum ignition energy. The fire occurred when the electric iron in which the outer box, bi-metal switch, and temperature fuse were removed over mattress and cotton shirts was powered by through heater terminal, and then the electric iron, mattress, and cotton shirts were combusted by the fallen combustibles because the temperature of combustibles reached to the minimum ignition energy with the help of active transfer of heat.