• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.212-215
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• 1995

In this paper, The characteristic of Harmonic spectrum is studied for generally used three-phase diode rectifier. and filter design criteria is showen in the sense of THD, DPF, and PF. As the becoming of Automative and informative era, the demand of critical and stable control becomes more and more important. But much EMI emissions are generated for more critical and stable control in power electronic system these EMI emissions can be measured using LISN(Line Impedance Stabilization Network). So we are to investigate the behavior of Conducted EMI emission in Diode Rectifiers using LISN in frequency domain.

• Computational Structural Engineering
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• v.5 no.3
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• pp.105-112
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• 1992

The design of reactor internals requires the accurate vibration characteristics of each component for subsequent dynamic structural response analysis. For Korean standard nuclear power plant some modifications on the Control Element Assembly shroud from the reference design have been made. Since the shroud is complex in geometry having an array of vertical round tubes and webs in a square grid pattern, and being tied down by preloaded tie rods into position, it is planned to perform a vibration measurement program consisting of both experimental and analytical modal studies upon that component. To determine the proper test conditions, the pre-test analysis has been performed using the general purpose structural analysis program ANSYS. Also the effects of the number of master degrees of freedom, holes in the web and tie-rod preload on the natural frequencies are examined prior to the pre-test analysis. After decision of appropriate finite element model, frequency analysis and harmonic analysis are performed and ideas for the test conditions such as the number of measurement points, their locations, measurement frequency range and the excitation force level are determined.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.376-378
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• 1996

This paper presents a new PFC control method which replaces a fast line current measurement with a filtered load current measurement. Using the power balance relation between the input and the output of the boost converter. the input current can be described as the function of load current. Thus the PWM signal which effects the switching control of the boost converter is generated using the PFC input voltage, the PFC output voltage and the load current as input variables. By using a filter between the bridge rectifier and a dc-to-dc converter, the input voltage of the dc-to-dc converter is forced to always maintain above zero volt. Then the input current traces a sinewave in phase. The proposed scheme accomplishes a very high power factor and a low harmonic distortion of the line current. The validity of this scheme is demonstrated through simulation.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.130-135
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• 2015

Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational rpm range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering from operating rpm up to target rpm, however, the range is un-measurable generally. In order to resolve the measurement issue, this study shows the measuring method and the assessment method of relevant natural frequency of whiling vibration by using measured harmonic order component of whirling vibration.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.184-184
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• 2012

Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering the range of MCR, however, the range is un-measurable. To resolve the measurement issue, this study shows the measuring method and the estimating method of whiling vibration by using resonance frequency of sub harmonic.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.310-314
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• 2008

The exploitation of the wind energy resource is a rapidly growing area world-wide. The number of installed units is continuously increasing, and it is important to respect and to deal with the impact of wind turbine. This paper addresses the power quality characteristics of U57 Wind Turbine. 750kW gearless type wind turbine for low wind speed, named U57, is developed by UNISON. The power quality measurement system consists of measuring WTG output current, line-to line voltage and wind speed signal. With using measured data, power quality measurement is evaluated about maximum power, reactive power, voltage fluctuation, harmonics according to IEC 61400-21.

• Journal of the Optical Society of Korea
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• v.2 no.2
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• pp.54-57
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• 1998

A noncollinear-phase-matching cone of second harmonic generation(SHG) was observed in a LiNbO3 crystal doped with l mol% MgO. Birefringence refractive indices can be accurately evaluated by analysing the temperature phase matching characteristic for SHG combined with the measurement of the half cone angle. The electro-optic coefficient can also be determined form the observed change of the half cone angle when a DC electric field is applied along the optic axis.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.191-193
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• 2016

This paper proposes a voltage-controlled oscillator (VCO) that has broadband turning and low-level of phase noise characteristics. Due to the micro-strip line resonant circuit with a low Q value, which is applied to the broadband tuning range, the depreciated phase noise performance is compensated by restraining the harmonics of the oscillating frequency. The VCO was designed according to the proposed structure as well as the conventional structure, and the superiority of the proposed structure was verified through its simulation, fabrication, and measurement.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.110-112
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• 2003

Harmonics happened due to nonlinear systems such as UPS, SCR controlled motors, and fluorescent lighting in distribute power system is very important subject to optimal operate and control of power system. Harmonics sometimes takes place incorrect operation of protective relaying system under normal condition on power system. This paper presents the actual recording data of transformer located at substation of industrial installation for harmonic analysis in detail.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.9
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• pp.1453-1461
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• 1989

The modified ESPRIT(MESPRIT) method for harmonic retrieval is presented and analyzed. The estimation of frequencies of sinusoidal signals corrupted by white or colored measurement noise is considered for the MESPRIT method. Monte-carlo simulations are conducted for the comparison of MESPRIT method with TK method in terms of sampled mean, root mean square and relative bias.