• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.826-834
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• 1994

The purpose of this study is to identify torque characteristics in capacitor type electric motors and to illustrate the effects of several design parameters on the fluctuating components of the motor torque. To do this, two revolving field theory and stationary reference frame theory were applied to derive governing equations for the torque generated by motor. For simulation studies, parameters of the motor components were measured under the conditions of no loading and locking. Based on these, effects of several design variables on the torque characteristics were analyzed and compared with the actual measurements, which were estimated indirectly by measuring the stator voltage and current. Then, some illustrative improvements in design are suggested by taking Taguchi method.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1068-1074
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• 2009

This paper describes a study for the buoy which should be operated by a stand-alone power system. The field of this study is related to a power system operated by two batteries which depends on the load power. The fluctuation of the voltages makes the life cycle of the battery shorten. The control algorithm has been proposed for reducing the voltage pulsation of the battery by operation strategy according to using purpose such as main or sub power supply system. The power system with battery is separated two parts and this has been proved through a simulation and a sea experiment. In order for the experiment to use a wireless monitoring system has been installed in buoy. This paper shows an excellent test result of wireless monitoring system for buoy.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.193-196
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• 2001

One of the major reasons for not integrating a VCO on one-chip in a PLL (phase locked loop) system is the large chip-to-chip variation of the VCO (voltage controlled oscillator) center frequency. In this thesis, a simple bias technique is proposed to compensate the process fluctuation. The proposed bias technique is applied to the VCO and it reduces the deviation of the VCO center frequency from 35% to 8 %. With the suggested bias technique, a 400 MHz frequency synthesizer is designed for general purpose. It utilizes a programmable divider for various division ratio. The design methodology provides the possibility of the one-chip solution for a PLL system.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.345-348
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• 2007

국내 업체인 유니슨에서는 750kW Gearless형 풍력발전기, U50을 개발하였다. 개발된 풍력발전기는 대관령 풍력실증연구단지에 설치되었다. 풍력시스템의 전력품질 측정 및 평가는 계통에 대한 영향을 조사하는데 있어서 중요한 요소이다. 이 논문에서는 전력품질에 대한 국제기준인 IEC61400-21을 적용하여 U50풍력발전기의 전력품질에 대한 데이터 수집 및 수집된 데이터를 통해 U50풍력발전기가 계통에 미치는 전력품질의 영향을 검토하였다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.257-261
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• 2001

This paper presents the implementation of wide-band RFIC amplifier operating from near 50MHz to 3GHz using Tachyonics SiGe HBT foundry. Voltage shunt feedback is used for the flat gain and the broad band impedance matching. Initial design parameters are calculated using the low frequency small signal analysis. Since the HBT model was not available at the design time, discrete tuning board was made for fine tuning in the low frequency range. Fabricated amplifier shows 12dB gain with 1dB fluctuation and PldB reaches 15dBm at 850MHz.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.251-252
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• 2008

Si-Hwa tidal power station is using difference of the ebb and flow. The active power is dependent on up and down sea water level but if it is drastically changed because of a typhoon or waves the generator terminal voltage and active power is changed that is a chief cause of power station unstability. Therefore this paper arrange a present state of power or frequency fluctuation and generator terminal phase difference in case of occurrence a drastic change of sea water level.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.121.1-121.1
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• 2014

Recently, much attention has been given to plasma production under liquid and its applications [1]. However, most of plasma production techniques reported so far utilize high voltage dc, ac, rf or microwave power [2], where damage to discharge electrodes and small discharge volume are remained issues. As an alternative of plasma production method under liquid, we have proposed pulsed microwave excited plasma using slot antenna, where damage to the slot electrode can be minimized and plasma volume can be increased. We have also reported improvement of treatment efficiency with use of reduced-pressure condition during the discharge [3]. To realize low pressure conditions in liquid, various alternative technique can be considered. One possible technique is simultaneous injection of microwave power and ultrasonic wave. Ultrasonic wave induces pressure fluctuation with the wave propagation and is so far used for cavitation production in the water. We propose utilization of reduced pressure induced by ultrasonic cavitation for improvement of the plasma production. Correlation between the plasma production and the ultrasonic power will be discussed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.19-22
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• 1999

N-doped and low-hydrogenated DLC thin films were coated on the Mo-tip FEAs in order to improve the field emission performance and their electrical properties were evaluated. The fabricated devices showed improved field emission performance in terms of turn-on voltage, emission current and current fluctuation. This result might be caused both by the shift of Fermi level toward conduction band by N-doping and by the inherent stability of DLC material. Furthermore, the transconductance of the DLC-coated Mo-tip FEA and electrical conductivity and optical band-gap of the deposited DLC films were investigated.

• Journal of Sensor Science and Technology
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• v.26 no.5
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• pp.324-330
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• 2017

In this paper, the automation of sweeping center setting for wavelength swept laser used in SS-OCT has implemented. For 3 regions where the initial FFP-TF pass wavelength can be located, each different DC voltage pattern is applied to FFP-TF. Through its performance test to the laser, fast and exact setting to sweeping central wavelength, flat sweeping with ${\pm}0.5dB$ fluctuation range, and 10 mW average optical power were obtained. This shows that the realized automatic setting process can replace an inconvenient manual setting operation used for current wavelength swept laser. Additionally it cuts costs for optical spectrum analyzer necessary to laser spectrum monitoring.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.131-132
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• 2000

We prepared Si emitters coated with a MOCVD $CoSi_2$ layer to improve the emission properties. The $CoSi_2$ layer was grown on Si field emitters in situ by reactive chemical-vapor deposition of cyclopentadienyl dicarbonyl cobalt at 600 ${\sim}$ $650^{\circ}C$. The $CoSi_2$ coated field emitters showed enhanced emission properties of current-voltage characteristics, which were due to the increase of emitting area from Fowler-Nordheim plot. And the emission current fluctuation decreased due to the chemically stable surface properties of $CoSi_2$.