• 전자공학회논문지
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• 제54권8호
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• pp.107-114
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• 2017

본 논문에서는 3상 4선식 전력계통에서 새로운 전압제어 방식의 역률보상시스템을 제안한다. 제안하는 전압제어 방식의 역률보상시스템은 슬라이닥을 이용하여 가변되는 출력전압을 커패시터에 인가하는 것으로 보상에 필요한 무효전력을 생성한다. 기존의 커패시터 뱅크 방법을 이용하는 역률보상시스템은 선택 가능한 커패시터 용량이 한정되어 있어 부하 상황에 따라 역률보상 오차가 발생하지만, 제안 시스템은 변화하는 부하를 추종하여 오차 없이 역률을 100%까지 보상할 수 있다. 본 논문에서는 3상 4선식 전력계통에서 전압제어 방식의 역률보상시스템과 제어 알고리즘을 개발하였고 모의실험과 실험을 통해 성능을 확인한다. 제안 시스템을 수용가에 설치할 경우 역률 개선을 통한 전기료 감소, 선로손실 감소, 부하 용량 증대 효과가 기대된다. 특히 발전 사업가 측에서는 역률 보상 성능의 향상으로 송전 여유 용량 확보와 발전량 절감이 가능하다.

• 대한수학회지
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• 제32권1호
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• pp.7-15
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• 1995

Multigrid method has been used widely to solve elliptic problems because of its applicability to many class of problems and fast convergence ([1], [3], [9], [10], [11], [12]). The estimate of convergence rate of multigrid is one of the main objectives of the multigrid analysis ([1], [2], [5], [6], [7], [8]). In many problems, the convergence rate depends on the regularity of the solutions([5], [6], [8]). In this paper, we present an improved estimate of reduction factor of multigrid iteration based on the proof in [6].

• 전자공학회논문지B
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• 제33B권4호
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• pp.124-130
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• 1996

A compensation method of color error resulting from dynamic range transformation of color image is propsoed. The color error is measured using the CIE L a b uniform color space, and the color image is compensated to minimize it. The color error is significant in the dark region of image, which is caused by the lunimance scaling factor is relatively large in that case. In the proposed method, we weight the luminance scaling factor corresponding to luminnce to minimize the error. Because the weighting factor depends on luminace distribution of image, a decisio method of weighting factor using histogram is also proposed.

• Journal of the Korean Statistical Society
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• 제29권3호
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• pp.337-350
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• 2000

This paper suggests a new diagnostic measure and a stopping rule for detecting influential observations in multiple discriminant analysis (MDA). It is developed from a Bayesian point of view using a default Bayes factor obtained from the fractional Bayes factor methodology. The Bayes factor is taken as a discriminatory information in MDA. It is shown that the effect of an observation over the discriminatory information is fully explained by the diagnostic measure. Based on the measure, we suggest a stopping rule for detecting influential observations in a given training sample. As a tool for interpreting the measure a graphical method is sued. Performance of the method is used. Performance of the method is examined through two illustrative examples.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.846-847
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• 2011

This paper presents the study on analysis of single phase induction motor characteristics by equivalent circuit. For high efficiency of single phase induction motor, the motor parameters used for equivalent circuit analysis is important. The accuracy of equivalent circuit analysis of motor depends on the circuit parameters like saturation factor. Therefore this paper proposed the analysis method considering saturation factor. The saturation factor was calculated by iteration routine and numerical method. this proposed method was verified by FEM analysis results and dynamo test results of the prototype model.

• 대한기계학회논문집A
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• 제24권3호
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• pp.560-566
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• 2000

Many researchers have dealt with the problems of fracture mechanics. Generally, these researches are concerned with crack in isotropic material without other micro defects. Actual structure, however, may contain micro defects as well as crack in manufacture processing or operation. If it contains mi defects near a crack, some different characteristics will be appear in fracture behaviors of the crack. This study examines the effect of the micro defect on stress intensity factor of center slant crack rectangular plate subjected to uniform uniaxial tensile stress. In this study, boundary element method(BEM) is used for analysis in stress intensity factor(SIF).

• Communications for Statistical Applications and Methods
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• 제16권2호
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• pp.317-323
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• 2009

Recently not even government polices but small town decisions are based on the survey data/information, so the most of government agencies/organizations demand various sample surveys in each fields for more detail information. However in conducting the sample survey, nonresponse problem rises very often and it becomes a major issue on judging the accuracy of survey. For that matters, one solution ran be using the administration data. However unfortunately most of administration data are restricted to the common users. The other solution can be the imputation. Therefore several method, of imputation are studied in various fields. In this study, in stead of the simple regression imputation method which is commonly used, factor score regression method is applied specially to the incomplete data which have the unit and item misting values in survey data. Here for simulation study, Consumer Expenditure Surveys in Korea are used.

• Wind and Structures
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• 제31권5호
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• pp.419-430
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• 2020

Weibull distribution is a conspicuous distribution known for its accuracy and its usage for wind energy analysis. The two and three parameter Weibull distributions are adopted in this study to fit wind speed data. The daily mean wind speed data of Ennore, Tamil Nadu, India has been used to validate the procedure. The parameters are estimated using maximum likelihood method, least square method and moment method. Four statistical tests namely Root mean square error, R2 test, Kolmogorov-Smirnov test and Anderson-Darling test are employed to inspect the fitness of Weibull probability density functions. The value of shape factor, scale factor, wind speed and wind power are determined at a height of 100m using extrapolation of numerical equations. Also, the value of capacity factor is calculated mathematically. This study provides a way to evaluate feasible locations for wind energy assessment, which can be used at any windy site throughout the world.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.263-266
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• 2009

When video packets are transmitted over error-prone networks, the leaky prediction can be used to mitigate the effect of error propagation. The leaky factor provides trade-off between coding efficiency and error resilience in the leaky prediction. In this paper, we propose an improved leaky prediction method where the leaky factor is adaptively determined for each frame by minimizing the estimated end-to-end distortion at the encoder. Experimental results show that the proposed method with the adaptive leaky factor shows the better performance of the error robustness as compared with the conventional method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.209-211
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• 2002

This paper computes the regional, seasonal and hourly representative model of load power factor considering load characteristics of all 154/22.9 kV substations. An accurately computed representative model of load power factor is studied to present a precision improvement of power system analysis and the security of the system. The method to compute representative model of load utilizes the method of applicable moving average based on the method of flow average. The EMS data are used as the source to assess the load power factor.