• 한국통계학회:학술대회논문집
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• 한국통계학회 2004년도 학술발표논문집
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• pp.1-8
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• 2004

We address the problem of parameter estimation in multivariate distributions under ignorable non-monotone missing data. The factoring likelihood method for monotone missing data, termed by Robin (1974), is extended to a more general case of non-monotone missing data. The proposed method is algebraically equivalent to the Newton-Raphson method for the observed likelihood, but avoids the burden of computing the first and the second partial derivatives of the observed likelihood Instead, the maximum likelihood estimates and their information matrices for each partition of the data set are computed separately and combined naturally using the generalized least squares method. A numerical example is also presented to illustrate the method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.193-195
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• 2005

전력계통의 안정적인 운용을 위해서는 현재 운전 중인 계통의 운용데이터를 수집하여 분석하고 그에 따라 적절한 제어를 하는 것이 매우 중요한 일이다. EMS가 이러한 일을 처리하고 있으며, 여기서 상태추정기는 정확한 계통 운용 데이터베이스를 제공하는 역할을 한다. 지금까지 모든 데이터는 동시에 측정이 되었다는 가정 하에 상태추정 연산을 하였으나, 실제로 모든 데이터 측정의 동기성을 확보하는 것은 사실상 불가능하다. 최근 인공위성에 의해 동기화된 PMU(phasor measurement unit)가 전력계통 운용에 사용되고 있다. 본 논문에서는 PMU로부터 얻을 수 있는 전압 및 전류 데이터를 상태추정에 이용하는 방법을 개발하였다. 위성에 의해 동기화된 페이저 측정데이터는 데이터 측정의 동기성 확보뿐만 아니라, 데이터의 정밀도 및 위상각의 직접적인 측정이라는 둥의 여러 가지 면에서 매우 효용성이 높은 데이터이다. 본 연구를 통해 개발된 상태추정 프로그터은 IEEE 30모선 시험계통을 이용하여 그 타당성을 검증하였다.

• Communications for Statistical Applications and Methods
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• 제6권1호
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• pp.327-336
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• 1999

In a multinomial sampling scheme some categories may be observed as partially classified because of technical or economic reasons. In this paper the maximum likelihood estimators(M.L.E) of multinomial probabilities are obtained when some frequencies are merged. We obtained the M.L.E and a method to evaluate the information gained by including merged frequencies in M.L.E we obtained an estimator of the covariance matrix and it is used to examine the information gained by including the merged frequency counts in estimating the cell probabilities. When certain individual frequency counts are missing a method is proposed for estimating the cell probabilities using EM algorithms.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1275-1276
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• 2015

Full wave electromagnetic simulation or fabricated models of an antenna are used to predict its radiation characteristics. In this work estimation of radiated power of an antenna based on its electrical model is presented. The computed radiated power using the electrical model have good agreement with the radiated power results obtained through the full wave electromagnetic simulation of the antenna model. The presented approach offers the advantage of saving of computation time of the full wave EM simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.866-869
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• 1988

In the operation of a power system, the security of the system has acquired significant importance to supply electric power of better quality. The State Estimator, a part of security functions, provides a complete real time solution estimate of the steady-state conditions of the power system for use by the Real Time Network Analysis functions. This paper briefly introduces the Fast Decoupled Weighted Least Square State Estimator which is adopted in the KEPCO EMS with features of Man-Machine Interface.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권1호
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• pp.72-77
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• 2014

To help machine designers to make precise design of large permanent magnet (PM) machines, this paper presents a set of design considerations that are very often ignored by machine designers. These considerations are categorized into several aspects: electromagnetic (EM) performance, losses and efficiency, fault and stability, and some other issues. The effects of various practical factors are presented and some corresponding design methods are introduced.

• 콘크리트학회지
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• 제3권3호
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• pp.121-128
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• 1991

시험체의 공지모드를 분석하여 대형 기계용 기초 콘크리트의 두께를 측정하였다. 시험체에 강철구 자유낙하에 의한 기계적인 충격을 가하여 진동을 발생시키고, 이 진동신호를 광대역 원추형 압전 탑촉자로 수신하였다. 수신된 진동신호를 FFT를 사용하여 주파수로부터 시험체의 두께를 결정하였다. 여러 층으로 이루어진 콘크리트 블록의 경우, 이 방법으로 결정된 값은 실제의 두께와 잘 일치하였다. 또한 이 방법은 두께 측정 뿐만 아니라 경계면의 접합 상태 파악에 활용될 수 있다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.47-48
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• 2014

물체 내부구조 및 매질 정수의 분포를 측정하기 위한 비파괴 기술은 지하자원의 탐사, 지하 케이블 및 매설관의 식별, 의료 분야의 영상진단 등에서 폭넓게 적용될 수 있다. 본 연구에서는 문제의 단순화를 위해 2차원 전자파 산란문제를 대상으로 역산란에 대한 해를 구하기 위한 정식화 과정을 검토하고 이의 유효성을 검증하고자 한다.

• 한국의류산업학회지
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• 제14권4호
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• pp.648-659
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• 2012

This research categorizes fundamental data needed to develop eco-friendly fabrics treated with bamboo leaf & pine leaf extracts. The effect of mordant on those fabrics was analyzed through the measurement of mechanical properties and the estimation of primary hand values for cotton and silk fabrics dyed with bamboo leaf and pine leaf extracts that were later treated with various mordants. When cotton was dyed with bamboo leaves and pine leaves extracts, EM, WT, 2HB, 2HG, 2HG5, LC, T, and W increased however, RT, SMD, and RC decreased compared to raw cotton fabric. The B, G, and MIU increased after mordant treatment to the dyed cotton and resulted in a stiffer and rougher cotton's hand. EM, WT, RT, MIU, WC, T, and W increased (in terms of silk); however, LT, B, 2HB, G, 2HG, 2HG5, MMD, SMD, and LC decreased compared to raw silk fabric. Similar to the dyed cotton, mordant treatment increased the MIU and LC of dyed silk subsequently, the hand became stiffer and rougher. A greater tannin adsorption results in an increased mechanical property and the primary hand value. For both fabrics, mordant treatment made its smoothness drop. However, the scale of drop for cotton was significant, while the scale of the drop for silk was minor. In terms of type of mordant, femordant and natural-mordant treatment influenced the tensile, shear, surface properties of fabrics, and primary hand values more than Cu-mordant and synthetic-mordant in addition, this increased the stiffness, hardness, and roughness of fabrics.

• 한국산업보건학회지
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• 제19권3호
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• pp.270-279
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• 2009

In order to check a necessity of health control for the laborers who are in use of mixed organic solvents in the printing industries, this study evaluated the use status of mixed organic solvents, health subjective symptoms on the exposure of the solvents, health hazard for each kind of printings for the employees who work for the printing industries located in Seoul and Gyeonggi. The study analyzed 228 sites and 311 people responded of the total 250 sites surveyed from March to September 2007, and obtained the following results; 1) Estimating the exposure of the mixed organic solvents, the study found that estimation of mixture(EM) was different for each kind of printings at a level of significance, excessiveness of EM was 7.5%, the highest, for gravure printing, 5.6% for screen printing, 4.7% for master printing, 2.9% for offset printing. 2) As to the mean scores of health subjective symptoms for each kind of printings, workers in screen printing showed high scores in every subjective symptom, of which symptom of central nervous system was 3.75, the highest, and the difference was statistically at a level of significance(p<0.01). 3) Results of the hazard analysis for carcinogens and non-carcinogens contained in the mixed organic solvents exposed to the workers showed that cancer risk of offset printing workers was $7.8{\times}10^{-9}$ for benzene, the mean cancer risk was $2.02.{\times}10^{-8}$ from Monte-Carlo simulation, and both risks did not exceed the US EPA permissible standard of $1{\times}10^{-6}$. The total hazard indices of the non-carcinogens estimated was 3.523, the highest, for gravure printing, 2.381 for master printing, 1.125 for screen printing, respectively, and all exceeded 1.