• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.2
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• pp.129-140
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• 1999

추계론적 해석은 구조계 내의 해석인수에 존재하는 공간적 또는 시간적 임의성이 구조계 반응에 미치는 영향에 대한 고찰을 목적으로 한다. 확률장은 구족계 내에서 특정한 확률분포를 가지는 것으로 가정된다. 구조계 반응에 대한 이들 확률장의 영향 평가를 위하여 통계학적 추계론적 해석과 비통계학적 추계론적 해석이 사용되고 있다. 본 연구에서는 비통계학적 추계론적 해석방법 중의 하나인 가중적분법을 제안하였다. 특히 구조계의 공간적 임의성이 큰 특성을 가지고 있는 반무한영역에 대한 적용 예를 제시하고자 한다. 반무한영역의 모델링에는 무한요소를 사용하였다. 제안된 방법에 의한 해석 결과는 통계학적 방법인 몬테카를로 방법에 의한 결과와 비교되었다. 제안된 가중적분법은 자기상관함수를 사용하여 확률장을 고려하므로 무한영역의 고려에 따른 해석의 모호성을 제거할 수 있다. 제안방법과 몬테카를로 방법에 의한 결과는 상호 잘 일치하였으며 공분산 및 표준편차는 무한요소의 적용에 의하여 매우 개선된 결과를 나타내었다.

• Journal of Animal Science and Technology
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• v.47 no.5
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• pp.703-710
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• 2005

Data from Hanwoo steers and bull calves were analyzed to see the phenotypic and genetic relationships between carcass traits from four different covariance models. Four models fit test station and test period as fixed effect of contemporary group and sire as random effect assuming paternal half-sib relationships among animals. Each model fits one of linear covariate (s) of different slaughter end points-age at slaughter in the first order, age at slaughter in the first and second order, slaughter weight or back fat thickness at 12-13th rib of cold carcass. Age at slaughter in its second order was not significant. Age at slaughter accounted for signifi- cant amount of genetic variances and covariances of carcass traits. Heritability estimates of back fat thickness, rib eye area, carcass weight, marbling score and dressing percentage were 0.34, 0.22, 0.24, 0.42 and 0.18, respectively at constant age basis. The genetic correlation between carcass weight and the other variables were all positive and low to high in magnitude. Genetic correlations between back fat thickness and rib eye area and between marbling score and dressing percentage were low but negative. Variance and covariance structure between these traits were shifted to a great extent when these variables were regressed on slaughter weight or on back fat thickness. These two covariates counteracted to each other but they adjusted each carcass variable or their interrelationship according to differential growth of body components, bone, muscle and fat. Slaughter weight tended to decrease genetic variances and covariances of carcass weight and between component traits and back fat thickness tended to increase those of rib eye area and between rib eye area and carcass weight.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.1
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• pp.17-27
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• 2014

As the importance of Cooperative Engagement Capability and network-centric warfare has been dramatically increasing, it is necessary to develop distributed tracking systems. Under the development of distributed tracking systems, it requires tracking filters and data fusion theory for nonlinear systems. Therefore, in this paper, the problem of nonlinear track fusion, which is suitable for distributed networks, is formulated, four algorithms to solve the problem of nonlinear track fusion are introduced, and performance of introduced algorithms are analyzed. It is a main problem of nonlinear track fusion that cross-covarinaces among multiple platforms are unknown. Thus, in order to solve the problem, two techniques are introduced; a simplification technique and a approximation technique. The simplification technique that help to ignore cross-covariances includes two algorithms, i.e. the sample mean algorithm and the Millman formula algorithm, and the approximation technique to obtain approximated cross-covariances utilizes two approaches, by using analytical linearization and statistical linearization based on the sigma point approach. In simulations, BCS fusion is the most efficient scheme because it reduces RMSE by approximating cross-covariances with low complexity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.208-217
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• 2018

This study was designed to examine the influence of academic stress, anxiety, interpersonal dependency, and hopelessness on female high school students and their level of depression. The study subjects were 684 students attending an all-female high school in C city. Data were collected by self-administered questionnaires between November 1st, 2016 and December 31st, 2016. The data were analyzed using the SPSSWIN(ver. 21.0) program. The mean values of the level of depression were analyzed by the t-test and ANOVA. The correlation coefficientswereobtained by Pearson correlation analysis and acovariance structure analysis was performed on the factors affecting the level of depression. It was found that the level of depression among all of the subjects was significantly higher within the group with a higher level of academic stress, anxiety, interpersonal dependency, and hopelessness. Thus, the level of depression was positively correlated with the levels of academic stress, anxiety, interpersonal dependency, and hopelessness. The factor that had the most influence on depression was the anxiety factor, followed by interpersonal dependency and academic stress. This result suggests that the level of depression in female high school students has a causal relationship with academic stress, anxiety, interpersonal behavioral characteristics, and hopelessness. Therefore, the most effective strategy to reduce the level of depression among female high school students would appear to be efforts to decrease their academic stress, anxiety, and interpersonal dependency.

• Proceedings of the Korean Association for Survey Research Conference
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• 2001.04a
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• pp.109.2-130
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• 2001

The purpose of this study is (1) to demonstrate that ignoring group differences may mislead to incorrect conclusion when analyzing correlation data (e.g., factor analysis), (2) to highlight the importance of the data analytic method considering group differences, and (3) to provide ways of incorporating group differences in data analysis. In study, 1, ignoring group difference in factor analysis may mislead to incorrect factor structure. To remedy this, z-transform method and group analysis tool in covariance structure models were suggested. In study 2, the group differences effect was illustrated by using real data (IQ test data).

• Survey Research
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• v.2 no.2
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• pp.109-130
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• 2001

The purpose of this study is (1) to demonstrate that ignoring group differences may mislead to incorrect conclusion when analyzing correlation data (e.g.. factor analysis). (2) to highlight the importance of the data analytic method considering group differences. and (3) to provide ways of incorporating group differences in data analysis. In study 1. ignoring group difference in factor analysis may mislead to incorrect factor structure. To remedy this. z-transform method and group analysis tool in covariance structure models were suggested. In study 2. the group differences effect was illustrated by using real data (IQ test data).

• The Korean Journal of Applied Statistics
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• v.21 no.2
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• pp.291-299
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• 2008

This paper discusses model building for repeated binary response data with different time-dependent covariates each occasion. Since repeated measurements data are having correlated structure, weighed least squares(WLS) methodology is applied. Repeated measures designs are usually having different sizes of experimental units like split-plot designs. However repeated measures designs differ from split-plot designs in that the levels of one or more factors cannot be randomly assigned to one or more of the sizes of experimental units in the experiment. In this case, the levels of time cannot be assigned at random to the time intervals. Because of this nonrandom assignment, the errors corresponding to the respective experimental units may have a covariance matrix. So, the estimates of effects included in a suggested logit model are obtained by using covariance structures.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.95-97
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• 2000

배열 안테나에서 안테나 소자의 개수의 증가는 안테나의 이득을 증가시킬 수 있으므로 열악한 채널 환경에서도 채널이 필요로 하는 링크 마진을 얻을 수 있다. 그러나, 기존 빔 형성기에서 사용되는 배열 안테나 기법은 많은 계산량과 소모 메모리량 때문에 배열 소자의 개수에 제한이 따르게 된다. 이러한 문제를 해결하기 위하여 본 논문에서는 배열 안테나의 구조에 따른 위상차이를 보상하여 적은 계산량과 메모리를 갖는 배열 위상 차이 보상을 이용한 평행 구조 빔 형성기를 제안한다 배열 위상 차이를 보상하는 기법으로 적은 계산량과 메모리로 개수가 많은 긴 배열 안테나에서 얻을 수 있는 분해능과 안테나 이득을 얻을 수 있다. 제안된 기법의 성능을 비교하기 위해 기존의 빔 형성기법으로delay-sum 빔 형성기와 공분산 행렬의 고유치 해석을 통한 고유벡터 기법의 빔 스펙트럼과 연산량을 비교하였다. 제안된 기법으로 빔 형성을 하면, 배열 안테나의 소자의 개수가 늘어나도 기존의 방법보다 최소 30%의 연산량으로 스펙트럼 상 비슷한 성능을 얻을 수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.4995-5004
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• 2011

This study was performed to determine the levels of depressive symptoms among community elderlies and to reveal its related factors, specifically aimed at revealing factors such as social support, family support and physical function. The interviews were performed, during the period from April 1st, to June 30th, 2010, to 995 elderlies in Daejeon city. As a results, social support, family support, ADL and IADL was found to be in a positive correlation with depressive symptoms. With the analysis of covariance structure, social support was more influential on the level of depressive symptom than family support and physical function. It was found to have the inter-relational effects that the greater the social support, family support and physical function, the lower the level of depressive symptoms.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.629-640
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• 2016

This study was conducted to investigate the influence of job stress, fatigue symptoms and job satisfaction on turnover intention among dental hygienists. Overall, 516 dental hygienists who work in dental clinics were surveyed using a standardized self-administered questionnaire from April 1 to June 30, 2015. Mean turnover intention was compared to each independent variable tested by t-tests and ANOVA, correlation among turnover intention, job stress, fatigue symptoms and job satisfaction was calculated by Pearson's correlation coefficient, and covariance structure analysis was used to evaluate whether turnover intention was associated with job stress, fatigue symptoms and job satisfaction. Turnover intention was significantly higher among subjects with higher job stress and fatigue, as well as those with lower job satisfaction. Additionally, turnover intention was significantly positively correlated with job stress and fatigue symptoms, while turnover intention was negatively correlated with job satisfaction. Covariance structure analysis revealed job stress had a greater impact on turnover intention than fatigue and job satisfaction, high job stress and fatigue, the lower the job satisfaction showed that the effect of increasing the turnover intention. Overall, these results indicate that turnover intention of dental hygienists are more heavily influenced by job satisfaction and job stress than fatigue. Therefore, efforts are needed to reduce job stress and fatigue, as well as to improve job satisfaction to reduce the degree of turnover intention among dental hygienists.