• 한국융합학회논문지
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• 제2권3호
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• pp.15-23
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• 2011

본 논문에서는 태양광발전의 3상 인버터의 동작특성을 해석하기 위하여, d-q좌표변환을 통하여 상태방정식을 유도하고, 출력제어를 위한 PI제어기를 갖은 전류제어 알고리즘과 인버터 설계에 대한 Sinusoidal PWM방식의 이론적 알고리즘 제시하였다. 이를 바탕으로 배전계통의 상용소프트웨어인 PSCAD/EMTDC를 이용하여 태양광발전의 모델링을 수행하였다. 그리고 시뮬레이션 결과와 이론적인 수치해석과의 비교, 분석을 통하여 본 연구에서 제시한 모델링의 유효성을 확인하였다.

• Journal of the Korean Data and Information Science Society
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• 제26권6호
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• pp.1225-1238
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• 2015

본 연구에서는 직장암 환자들의 수술 후 재발까지의 시간 데이터에 대해 집단 간 생존함수 양상에 차이가 있는지 로그 순위 검정 결과 유의수준 10%에서 포도당 단일수송체 (GLUT1)의 수준, 수술 전 병기 (cstage), 수술 후 병기 (ypstage)에 따른 차이가 유의하며, Cox 비례위험률 모형을 이용하여 검정한 결과 가장 유의한 공변량은 포도당 단일수송체와 수술 후 병기였다. 지수분포를 따른다고 가정할 경우, 우도함수를 기반한 여러 가지 위험률 변화점을 추정하였다.

• Geomechanics and Engineering
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• 제24권5호
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• pp.419-430
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• 2021

Investigation on the compressibility and shear strength of compacted loess is of great importance for the design and operation of engineering infrastructures in filling area. In this study, the mechanical behaviors of Yan'an compacted loess are investigated at various dry densities and water contents by conducting one dimensional compression and direct shear tests. And the elastic compressibility, plastic compressibility, yield stress and strength are obtained from the experiments. Results show that when water content increases, plastic compressibility parameter increases, but yield stress decreases. However, the increase of dry density leads to a decrease in plastic compressibility parameter but an increase in yield stress. In addition, elastic compressibility parameter is found to be a constant which is irrelevant to water content and dry density. As for strength, cohesion and internal friction angle is directly proportional to dry density, but inversely proportional to water content. Moreover, the mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) tests were also performed to observe the pore size distribution and microstructure of the specimens. Finally, by using results of MIP and SEM tests, the compressibility and strength behaviours of Yan'an compacted loess are explained from the perspective of pore-size distribution and microstructure.

• 한국산업정보학회논문지
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• 제20권4호
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• pp.111-126
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• 2015

최근 많은 기업들이 협력을 통하여 투자비용과 위험은 분산시키고, 자원과 이익을 공유하여 경쟁력 강화를 시도하고 있다. 기업 간 공유경제는 기업 간 협력의 한 형태로 기업이 보유하고 있는 유휴자원을 공유하여 그 효용을 높이는 경제적 활동이다. 다양한 이해관계자가 참여하는 기업 간 공유경제에서는 이익의 명확한 배분 방안이 있어야 한다. 따라서 본 연구에서는 기업 간 공유경제를 위한 연합 구성시 발생하는 거래비용을 적용할 수 있는 MST(Minimal Spanning Tree) 방법, 각 참가자들이 주도하여 발생하는 거래비용의 평균, 참가자 간 발생하는 거래비용에 대하여 샤플리 밸류 적용의 3가지 방법을 제안하였다. 또한 협조적 게임이론에 근거한 이익 배분 방법인 이익 균등배분(Equal distribution of gain), 이익 비례배분(Proportional distribution of gain), 샤플리 밸류(Shapley Value)에 거래비용을 적용한 이익 배분 방안을 제시하였다.

• Journal of the Korean Data and Information Science Society
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• 제24권6호
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• pp.1465-1475
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• 2013

The chi-square type test statistic is the most commonly used test in terms of measuring testing goodness-of-fit for multinomial logistic regression model, which has its grouped data (binomial data) and ungrouped (binary) data classified by a covariate pattern. Chi-square type statistic is not a satisfactory gauge, however, because the ungrouped Pearson chi-square statistic does not adhere well to the chi-square statistic and the ungrouped Pearson chi-square statistic is also not a satisfactory form of measurement in itself. Currently, goodness-of-fit in the ordinal setting is often assessed using the Pearson chi-square statistic and deviance tests. These tests involve creating a contingency table in which rows consist of all possible cross-classifications of the model covariates, and columns consist of the levels of the ordinal response. I examined goodness-of-fit tests for a proportional odds logistic regression model-the most commonly used regression model for an ordinal response variable. Using a simulation study, I investigated the distribution and power properties of this test and compared these with those of three other goodness-of-fit tests. The new test had lower power than the existing tests; however, it was able to detect a greater number of the different types of lack of fit considered in this study. I illustrated the ability of the tests to detect lack of fit using a study of aftercare decisions for psychiatrically hospitalized adolescents.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 춘계 학술발표회 논문집
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• pp.17-23
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• 2005

In this paper we consider the well-known semiparametric proportional hazards models for survival analysis. These models are usually used with few covariates and many observations (subjects). But, for a typical setting of gene expression data from DNA microarray, we need to consider the case where the number of covariates p exceeds the number of samples n. For a given vector of response values which are times to event (death or censored times) and p gene expressions(covariates), we address the issue of how to reduce the dimension by selecting the significant genes. This approach enables us to estimate the survival curve when n ${\ll}$p. In our approach, rather than fixing the number of selected genes, we will assign a prior distribution to this number. The approach creates additional flexibility by allowing the imposition of constraints, such as bounding the dimension via a prior, which in effect works as a penalty To implement our methodology, we use a Markov Chain Monte Carlo (MCMC) method. We demonstrate the use of the methodology to diffuse large B-cell lymphoma (DLBCL) complementary DNA (cDNA) data and Breast Carcinomas data.

• Communications for Statistical Applications and Methods
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• 제12권3호
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• pp.729-742
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• 2005

In this paper, we discuss the propriety of the various noninformative priors for the Pareto distribution. The reference prior, Jeffreys prior and ad hoc noninformative prior which is used in several literatures will be introduced and showed that which prior gives the proper posterior distribution. The reference prior and Jeffreys prior give a proper posterior distribution, but ad hoc noninformative prior which is proportional to reciprocal of the parameters does not give a proper posterior. To compute survival function, we use the well-known approximation method proposed by Lindley (1980) and Tireney and Kadane (1986). And two methods are compared by simulation. A real data example is given to illustrate our methodology.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.73-76
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• 2001

We have simulated the effect of fracture characteristics on reduction of effective permeability of the fractured rocks due to in-situ bacteria growth. A nutrient is injected continuously for growth of in-situ bacteria. We used a power law for fracture length distribution and a fBm for fracture aperture spatial distribution. The results show that in-situ bacteria growth reduces the Permeability hyperbolically, but the porosity of backbone fracture does not change significantly. It shows that reduction of the permeability proceeds at faster speed for smaller value of length exponent(a) and for larger value of Hurst exponent(H). The fracture length distribution has stronger effect on speed of reduction than the aperture spatial distribution. The time needed to reduce permeability is inversely proportional to the hydraulic gradient.

• 한국염색가공학회지
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• 제15권5호
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• pp.327-332
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• 2003

In this study, the polyurethane microcapsules for non-aqueous dyeing containing iron oxide and disperse dyes were prepared by in-situ polymerization method using hexamethylene diisocyanate(HDI) with ethylene glycol(EG). And the size, shape, and particle size distribution of microcapsules prepared were investigated. The size and shape of microcapsule were observed by optical microscope and scanning elecron microscope. The particle size distribution was analyzed by particle size analyzer. The microcapsule size and its distribution were largely effected by the existance of surface active agent in the system. When a surfactant did not exist in the system, the size distribution of microcapsules prepared was much uneven. By adding a surfactant, this phenomenon was disappeared. And the size of microcapsule was also effeced by the hydrophobicity of core material(disperse dye). It was considered due to the difference of dispersity of core materials. And the size of microcapsule prepared was inversely proportional to the stirring speed.

• 한국산림과학회지
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• 제17권1호
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• pp.29-34
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• 1973

$C_{\small{OULOMB}}$과 $R_{\small{ANKINE}}$의 토압론(土壓論)에 기초(基礎)하여 중력식구조물(重力式構造物)이나 deflection 성구조물(性構造物)에 흔히 발생(發生)한 B형변위(型變位)에 대하여 연구고찰(硏究考察)함으로써 식(式) $$E=1/2\;H^2\frac{sin(u-{\varepsilon})cos({\alpha}+{\varepsilon})}{cos(u+{\alpha})}{\cdot}cot(u+{\rho})$$을 얻었는데 이식(式)은 토압재분배(土壓再分配)를 고찰(考察)한 식(式)이므로 실용도(實用度)가 높으리라 생각되며 본식(本式)에 의(依)하여 다음과 같은 결론(結論)을 얻었다. 1. 토압(土壓)은 벽고(壁高)의 자승(自乘)에 직비례(直比例)한다. 2. 토압(土壓)은 지표(地表)의 경사도(傾斜度)에 정비례(正比例)하며 벽체(壁體)의 변위(變位)에 반비례(反比例)한다. 3. 토압선도(土壓線圖)는 이차포물선(二次抛物線)으로 분포(分布)한다(그림 5의 b). 4. 토압강도(土壓强度)는 정수압적분포(靜水壓的分布)를 한다(그림 5의 c).