• 전기기술인
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• 통권274호
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• pp.22-28
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• 2005

최근 일부 선진국을 중심으로 대용량 전력제어용 반도체 소자와 제어기술의 발달로 인해 전력전자 반도체 소자인 IGBT(Insulated Gate Bi-polar Transistors) 등을 사용한 승강압형 컨버터 방식으로 동기발전기 계자전류를 제어하는 특이한 모델이 발전기 출력전압을 보다 속응성 있게 제어함은 물론, 신뢰성 있고 안정적으로 제어 할 수 있는 방법으로 등장함에 따라 이에 대한 기술적 연구가 진행되고 있다. 이에따라 본 고에서는 발전기 제어시스템의 개요, 국내외 기술개발 동향과 개발시스템의 구성, 주요기능 그리고 발전소 현장 적용 전에 시스템의 신뢰도 확보를 위해 전동발전기(M-G Set)를 이용한 시스템의 모의시험 결과와 향후 발전기 제어시스템의 발전 전망 등을 9회에 걸쳐 기술한다.

• 전기기술인
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• 통권273호
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• pp.32-36
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• 2005

최근 일부 선진국을 중심으로 대용량 전력제어용 반도체 소자와 제어기술의 발달로 인해 전력전자 반도체 소자인 IGBT(Insulated Gate Bi-polar Transistors) 등을 사용한 승강압형 컨버터 방식으로 동기발전기 계자전류를 제어하는 특이한 모델이 발전기 출력전압을 보다 속응성있게 제어함은 물론, 신뢰성 있고 안정적으로 제어 할 수 있는 방법으로 등장함에 따라 이에 대한 기술적 연구가 진행되고 있다. 이에 따라 본 고에서는 발전기 제어시스템의 개요, 국내외 기술개발 동향과 개발시스템의 구성, 주요기능 그리고 발전소 현장 적용 전에 시스템의 신뢰도 확보를 위해 전동발전기(M-G Set)를 이용한 시스템의 모의시험 결과와 향후 발전기 제어시스템의 발전 전망 등을 그회에 걸쳐 기술한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
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• pp.135-138
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• 1993

The Modelling, design and analysis of the steady state and performance characteristic of the constant switching frequency P.W.M controlled LLC and LLCC-type P.R.C are presented continuous conduction mode of operation. A set of characteristic frequency are plotted which design parameters can be obtained.

• East Asian mathematical journal
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• 제23권1호
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• pp.83-101
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• 2007

In this paper the concept of somewhat pairwise fuzzy continuous functions and somewhat pairwise fuzzy open functions are introduced. Some interesting properties of these functions are investigated besides giving some characterizations of these functions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.820-823
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• 1987

교류전동기의 속도조절과 전력절감에 이용되는 인버터는 그 응용분야에 따라 요구되는 출력특성이 다르게 된다. 본 연구에서는 전동기-발전기 셋트와 반환용 인버터를 이용하여 인버터가 응용되는 환경을 임으로 구현할 수 있는 부하장치를 구성하고, 이때 소모되는 전력을 전원에 반환하여 전력소모를 줄었다.

• 대한수학회보
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• 제58권3호
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• pp.573-591
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• 2021

We study the equivariant Gromov-Witten theory of ℙ^r-1 for all r ≥ 2. We prove a polynomiality property in r of the Gromov-Witten classes of ℙ^r-1. Using this polynomiality property, we define a set of polynomial valued classes in $H^*({\bar{M}}_{g,n})$ which generalize the limit of Witten's s-spin classes studied by Pandharipande, Pixton and Zvonkine.

• Journal of Astronomy and Space Sciences
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• 제34권3호
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• pp.183-197
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• 2017

We present simulations of the optical-band images of high-redshift galaxies utilizing 845 near-ultraviolet (NUV) images of nearby galaxies obtained through the Galaxy Evolution Explorer (GALEX). We compute the concentration (C), asymmetry (A), Gini (G), and $M_{20}$ parameters of the GALEX NUV/Sloan Digital Sky Survey r-band images at z ~ 0 and their artificially redshifted optical images at z = 0.9 and 1.6 in order to quantify the morphology of galaxies at local and high redshifts. The morphological properties of nearby galaxies in the NUV are presented using a combination of morphological parameters, in which early-type galaxies are well separated from late-type galaxies in the $G-M_{20}$, $C-M_{20}$, A-C, and $A-M_{20}$ planes. Based on the distribution of galaxies in the A-C and $G-M_{20}$ planes, we examine the morphological K-correction (i.e., cosmological distance effect and bandshift effect). The cosmological distance effect on the quantitative morphological parameters is found to be significant for early-type galaxies, while late-type galaxies are more greatly affected by the bandshift effect. Knowledge of the morphological K-correction will set the foundation for forthcoming studies on understanding the quantitative assessment of galaxy evolution.

• 태양에너지
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• 제19권3호
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• pp.43-51
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• 1999

Axisymmetric circular water jet impinges against rectangular heated surface with uniform hear flux and wire-mesh screens are set up in the nozzle-to-heater space to augment heat transfer. In the free jet region to be used them, pressure drop and intensive turbulence flow was brought up. When water jet system is not used wire-mesh screens, maximum heat transfer appears in the stagnation point and the secondary maximum appears X/D=4 but it disappears when they are is used. In the low velocity(Vo<6.0m/s), coarse mesh-screen enhanced heat transfer but fine mesh-screens inpeded heat transfer. In the high velocity(Vo>6m/s), all of them enhanced heat transfer. Average Nusselt number of experimental system to be used wire-mesh screens was promoted $4{\sim}6$times than that of simple water jet system. The stagnation heat transfer of experimental system to be used wire-mesh screens was augmented 6times that of simple water jet system.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.158-161
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• 2008

In the line array roll set (LARS) process, the initial plate is progressed into the final shape in a stepwise or pathwise manner according to the basic principle of the incremental forming process. The deformation proceeds simultaneously in the longitudinal and transverse directions. It was found that the curvature level of the formed plates in the previous study was well over the curvature required in shipyards. This fact shows that the LARS method has considerable potential for shipbuilding applications. In this study, several experiments with the LARS system is carried out fur manufacturing of plates with large curvatures. The bulbs at a stem and stern among ship hull plates correspond to these plates. Furthermore, the qualities of formed plates are evaluated according to the types of roll arrangements through experimental and numerical analyses.

• 천문학회보
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• 제39권1호
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• pp.61.2-61.2
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• 2014

We present a set of fiducial sequences of horizontal-branch stars in bright Galactic globular clusters, which have previously been observed in the Sloan Digital Sky Survey (SDSS). We derive fiducial lines on color-magnitude diagrams in multiple color indices (g - r, g - i, g - z, and u - g), after rejecting foreground and background objects as well as RR Lyrae variables utilizing these color indices. We compare our fiducial sequences with model predictions from Yonsei-Yale evolutionary tracks and BaSel spectral libraries, and find a satisfactory agreement between them in terms of their color-magnitude relations, except in u - g. We also compare theoretical models to color-magnitude diagrams of two open clusters (M67 and NGC 6791). Based on our best available cluster distance and reddening, we find that the mass of red clump (RC) stars in NGC 6791 is about a factor of two smaller than an earlier estimate from the application of asteroseismic scaling relations for solar-like oscillations. The smaller RC mass implies an enhanced mass loss along the red giant branch, which is in accordance with other compelling evidences found in this metal-rich system. Our estimated luminosity of RC stars in NGC 6791 is about 0.2 mag fainter than in earlier investigations based on solar-metallicity calibrations, and results in ~10% reduction in the RC-based distance estimation, when applied to metal-rich systems such as in the Galactic bulge.