• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.356-362
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• 2015

This paper presents a current control strategy in the synchronous reference frame for a single-phase PWM converter, which ensures sinusoidal input current control under the distorted source voltage and frequency condition. Given that the distorted source voltage distorts the phase angle for PWM converter control, the input current contains the same harmonics as the source voltage. Aside from the distorted voltage, the variation in source frequency reduces the performance of input current control. To achieve sinusoidal input current control under the distorted source voltage and frequency condition, this paper proposes a compensation strategy of current reference with the distortion component extracted from the phase angle and a detection strategy of frequency variation from the output of a synchronous reference frame phase-lock loop. The experimental results confirm the validity of the proposed method under the distorted source voltage and frequency condition.

• Journal of the Korean Ceramic Society
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• v.33 no.10
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• pp.1131-1137
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• 1996

The dielectric properties and phase stabilities of Pb(Zn0.6Mg0.4)1/3Nb2/3O3 [PZMN]system were investigated into substitution of A-site with Ba, Sr and Ca ions. The A-site substitutions led to the complexity of components of perovskite phase and then DPT coefficient increased. The A-site substitutions of Ba or Sr ion perovskite single phase could be easily formed by columbite process due to increase of perovskite phase stability. The variation of lattice parameters in specimen obeyed Vegard's law and curie temperature and dielectric constant of specimen decreased linearly. But Ca substitution led to perovskite phae instability. The lattice parameter dielectric constant and curie temperature of specimens drasticaly decreased with formation of pyrochlore phase.

• The Transactions of the Korean Institute of Power Electronics
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• v.28 no.1
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• pp.59-67
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• 2023

This paper explores the variation of DC-Link current ripple analysis in terms of duty cycle and phase angle of Multi-phase/Multi-stage boost converter. A 2-Stage/1-Stage boost converter DC-Link current is used to determine the difference between the 1st stage diode current and the 2nd stage inductor current. Each stage boost converter diode and inductor current is subordinate to the phase angle and duty cycle. The magnitude of the ripple current is variable according to phase angle and duty cycle. The analysis results are verified by variation of DC-Link current ripple using a 1kW typical 2-stage/1-stage boost converter.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.4
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• pp.452-459
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• 2009

A 6-bit MMIC digital attenuator applicable to X-band TR module has been developed by using $0.5{\mu}m$GaAs pHEMT processes. The Switched-T attenuator scheme and the switched-path attenuator scheme were adopted to obtain low insertion loss and small phase variation, respectively. Resistors and transmission lines are optimized to achieve the digital attenuator with high attenuation accuracy and small phase variation. The digital attenuator has RMS error of 0.4dB, resolution of 0.5dB and dynamic range of 31.5dB. The measurement results show that in-out VSWRs are less than 1.5, phase variation is from -7 to +2 degrees and IIP3 is 36.5dBm.

• The Journal of the Acoustical Society of Korea
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• v.29 no.3
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• pp.165-172
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• 2010

It is important to determine the communicational method that knows the characteristic of phase variation along transducers formed array within the water column in actual underwater environment and the correlation between transducers. This paper analyzes the characteristic of phase variation that vary on different locations by probe signals that transmitted from a probe source and received along transducers. This paper calculated the theoretical transmission capacities by the analyzation of the correlation between transducers through changing the distance between transducers and the distance between a probe source and transducers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.3
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• pp.239-246
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• 1982

The effect of the second phase morphology on the fracture ductility of dual phase steel was studied by means of tensile tests carried out room temperature. In this case the second phase morphology is characterized by two kinds; one is the MEF microstructure in which martensite encapsulated islands of ferrite, the other is the FEM microstructure in which ferrite encapsulated islands of martensite. The fracture ductility is improved by variation of the second phase morphology, but is essentially uneffected in the range of high strength ratio (4.7). Also the variation of ductility is well understood according to the difficulty of cleavage crack formation of the ferrite grain and to the brittleness of the martensitic structure.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1919-1921
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• 2002

In this paper, we were designed the ferroelectric phase shifter using 3-dB, $90^{\circ}$ branch-line hybrid coupler with two ports terminated in symmetric phase-controllable reflective networks. The design of phase shifter is based on reflection theory of terminating circuits. In order to find the optimum conditions of reflect phase, the effect of a change of capacitance and transmission line connected with two coupled ports of a coupler have been investigated. To obtain more accurate design parameters, finite element method is applied. We were showed large phase variation with small capacitance variation in the parallel connection of capacitor and transmission line by using EM-simulation and circuit-simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.1
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• pp.71-79
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• 1990

An analog phase shifter is designed at the operating frequency 10GHz that is coupled with a hybrid ring and the network connecting an inductor series with a varactor to extend a continuous chage in the phase of the reflected output wave to be produced from a variation in the terminated varactor reactance as a variation in the reverse bias voltage. It is manufactured in a microstripline in consideration of an effect of the dispersion characteristics and discontinuities. As a resuls of an experiment, a change in the phase is achieved over 180 degree from $52.34^{\circ}$ degrees to $235.01^{\circ}$degrees, the transmission loss is -3.6~-14.3dB, and the return loss is -16~-8dB(1.37

• Journal of the Korean Society for Heat Treatment
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• v.8 no.1
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• pp.65-74
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• 1995

This research was performed to investigate the effect of ageing on grain refinement of 82wt%Cu-13.5wt%Al-4.5wt%Ni-0.1wt% misch metal alloy with ageing temperature and time. The results obtained in this study are as follows; The variation of transformation temperature with ageing temperature had very influence on ageing time at $300^{\circ}C$. But it had not influence on ageing time at $100^{\circ}C$. The variation of transformation temperature after second reversed transformation cycle was not occured in martensitic phase ageing, but $M_s$ point was appeared equally with third reversed transformation cycle in parent phase ageing. The variation of $M_s$ point was not nearly with ageing time at $100^{\circ}C$ ageing temperature. But it was decreasing with ageing time at $300^{\circ}C$ ageing temperature and $A_s$ point was increasing with ageing time. Structure of parent phase ageing was being M18R martensitic and N2H martensitic phase. It was found that ${\alpha}$ and ${\gamma}_2$ phase were created by ageing of long time at $300^{\circ}C$ ageing temperature.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.124-133
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• 2004

Global climate variations are expected to affect local hydro-meteorological variables like precipitation and temperature. The Southern Oscillation (SO) is one of the major driving forces that give impact on regional and local climatic variation. The relationships between SO and local climate variation are, however, characterized by strong nonlinear variation patterns. In this paper, the nonlinear dynamic relationship between the Southern Oscillation Index (SOI), precipitation, and temperature in Fukuoka, Japan, is investigated using by a nonlinear multivariable approach. This approach is based on the joint variation of these variables in the phase space. The joint phase-space variation of SOI, precipitation, and temperature is studied with the primary objective to obtain a better understanding of the dynamical evolution of local hydro-meteorological variables affected by global atmospheric-oceanic phenomena.