• Communications for Statistical Applications and Methods
• /
• 제19권2호
• /
• pp.219-224
• /
• 2012

This article considers the mean time to failure(MTTF) of a dependent parallel system. We study how the degree of dependency components influences the increase in the mean lifetime for this system. The results are illustrated by tables and figures.

• 한국수자원학회논문집
• /
• 제45권2호
• /
• pp.191-201
• /
• 2012

본 연구에서는 연최대치 독립 호우사상의 결정에 사용되는 Freund 이변량 지수분포의 매개변수 추정과정을 구체적으로 검토하였다. 먼저, 모멘트법을 이용하는 경우를 구체적으로 검토하고, 그 결과를 최우도법을 적용한 결과와 비교하였다. 두 방법을 1961~2010년 서울지점의 시강우 자료에 적용하여 연최대치 독립 호우사상을 선정하고, 그 결과를 비교 검토하였다. 이러한 과정을 통해 얻은 결과는 다음과 같다. 첫째, 매개변수 추정방법으로 모멘트법을 적용하는 경우에는 두변량의 평균과 분산뿐만 아니라 상관계수도 고려해 주어야 하는 것으로 나타났다. 둘째, 최우도법은 두변량의 평균에 대한 재현성이 우수하고, 모멘트법은 분산의 경년변동을 잘 나타내는 것으로 나타났다. 셋째, 모멘트법과 최우도법을 통해 선정한 연최대치 독립 호우사상들은 대체로 유사한 것으로 나타났다. 다르게 선정된 호우사상은 최우도법의 경우에는 총 강우량이 큰 것, 모멘트법의 경우에는 강우강도가 큰 것으로 나타났다.

• 대한수학회논문집
• /
• 제38권1호
• /
• pp.153-161
• /
• 2023

In this paper, we introduce a new concept for bivariate means and we study its properties. Application of this concept for mean-inequalities is also discussed. Open problems are derived as well.

• Animal Bioscience
• /
• 제37권4호
• /
• pp.622-630
• /
• 2024

Objective: Pig breeders cannot obtain phenotypic information at the time of selection for sow lifetime productivity (SLP). They would benefit from obtaining genetic information of candidate sows. Genomic data interpreted using deep learning (DL) techniques could contribute to the genetic improvement of SLP to maximize farm profitability because DL models capture nonlinear genetic effects such as dominance and epistasis more efficiently than conventional genomic prediction methods based on linear models. This study aimed to investigate the usefulness of DL for the genomic prediction of two SLP-related traits; lifetime number of litters (LNL) and lifetime pig production (LPP). Methods: Two bivariate DL models, convolutional neural network (CNN) and local convolutional neural network (LCNN), were compared with conventional bivariate linear models (i.e., genomic best linear unbiased prediction, Bayesian ridge regression, Bayes A, and Bayes B). Phenotype and pedigree data were collected from 40,011 sows that had husbandry records. Among these, 3,652 pigs were genotyped using the PorcineSNP60K BeadChip. Results: The best predictive correlation for LNL was obtained with CNN (0.28), followed by LCNN (0.26) and conventional linear models (approximately 0.21). For LPP, the best predictive correlation was also obtained with CNN (0.29), followed by LCNN (0.27) and conventional linear models (approximately 0.25). A similar trend was observed with the mean squared error of prediction for the SLP traits. Conclusion: This study provides an example of a CNN that can outperform against the linear model-based genomic prediction approaches when the nonlinear interaction components are important because LNL and LPP exhibited strong epistatic interaction components. Additionally, our results suggest that applying bivariate DL models could also contribute to the prediction accuracy by utilizing the genetic correlation between LNL and LPP.

• Kyungpook Mathematical Journal
• /
• 제62권2호
• /
• pp.389-405
• /
• 2022

We study the Fisher Information (FI) of m-generalized order statistics (m-GOSs) and their concomitants about the shape-parameter vector of the Iterated Farlie-Gumbel-Morgenstern (IFGM) bivariate distribution. We carry out a computational study and show how the FI matrix (FIM) helps in finding information contained in singly or multiply censored bivariate samples from the IFGM. We also run numerical computations about the FIM for the sub-models of order statistics (OSs) and sequential order statistics (SOSs). We evaluate FI about the mean and the shape-parameter of exponential and power distributions, respectively. Finally, we investigate the Kullback-Leibler distance in concomitants of m-GOSs.

• Journal of Acupuncture Research
• /
• 제25권2호
• /
• pp.189-197
• /
• 2008

Objectives : This study was performed in order to investigate the effectiveness of electromyography and the Heart Rate Variability(HRV) test as prognosis factors, and to clarify correlation between Electromyography and the Heart Rate Variability test. Methods : 44 Bell's palsy patients who were graded V on the House-Brackmann scale and underwent HRV and EMG testing were retrospectively reviewed based on medical records. Results from both tests were analyzed via simple linear regression, and bivariate correlation analysis was performed to investigate the correlation between results from the two tests. The severity of the facial palsy at onset and at 2 weeks after treatment were evaluated with the H-B grade and Yanagihara grading system, and was converted into improvement scores. Results : Mean axonal loss according to electromyography showed a statistically significant correlation in predicting peripheral facial palsy improvement(p<0.01). HR, SDNN, TP, LF, HF, VLF, and LF/HF ratio on the Heart Rate Variability test showed no significant correlation in predicting peripheral facial palsy improvement. Mean axonal loss determined by electromyography, and HR, SDNN, TP, LF, HF, VLF, and LF/HF ratio recorded with the Heart Rate Variability test was analyzed with the bivariate correlation analysis method. Mean axonal loss and SDNN showed a statistically significant correlation(p<0.01) Conclusions : The Heart Rate Variability test has no statistical significance in predicting peripheral facial palsy improvement. SDNN has a statistically significant correlation with mean axonal loss as determined by electromyography.

• 품질경영학회지
• /
• 제13권1호
• /
• pp.31-40
• /
• 1985

In this paper, statistical estimation of the parameters of the bivariate exponential distribution are studied. Bayes estimators of the parameters are obtained and compared with the maximum likelihood estimators which are introduced by Freund. We know that the method of moments estimators coincide with the maximum likelihood estimators and Bayes estimators are more efficient than the maximum likelihood estimators in moderate samples. The asymptotic distributions of the maximum likelihood estimators and the estimator of mean time to system failure are obtained.

• Structural Engineering and Mechanics
• /
• 제76권4호
• /
• pp.529-540
• /
• 2020

Concurrent topology optimization of macrostructure and microstructure has attracted significant interest due to its high structural performance. However, most of the existing works are carried out under deterministic conditions, the obtained design may be vulnerable or even cause catastrophic failure when the load position exists uncertainty. Therefore, it is necessary to take load position uncertainty into consideration in structural design. This paper presents a computational method for robust concurrent topology optimization with consideration of load position uncertainty. The weighted sum of the mean and standard deviation of the structural compliance is defined as the objective function with constraints are imposed to both macro- and micro-scale structure volume fractions. The Bivariate Dimension Reduction method and Gauss-type quadrature (BDRGQ) are used to quantify and propagate load uncertainty to calculate the objective function. The effective properties of microstructure are evaluated by the numerical homogenization method. To release the computation burden, the decoupled sensitivity analysis method is proposed for microscale design variables. The bi-directional evolutionary structural optimization (BESO) method is used to obtain the black-and-white designs. Several 2D and 3D examples are presented to validate the effectiveness of the proposed robust concurrent topology optimization method.

• 한국수학교육학회지시리즈A:수학교육
• /
• 제37권1호
• /
• pp.1-13
• /
• 1998

In this paper, we have represented the efficient way how to enumerate the optimal number-right scores to adjust the item difficulty and to improve item discrimination. To estimate the optimal number-right scores in two equivalent math-tests by linear score equating a measurement error model was applied to the true scores observed from a pair of equivalent math-tests assumed to measure same trait. The model specification for true scores which is represented by the bivariate model is a simple regression model to inference the optimal number-right scores and we assume again that the two simple regression lines of raw scores and true scores are independent each other in their error models. We enumerated the difference between mean value of $\chi$＊ and ${\mu}$$\_$$\chi$/ and the difference between the mean value of y＊and a＋b${\mu}$$\_$$\chi$/ by making an inference the estimates from 2 error variable regression model. Furthermore, so as to distinguish from the original score points, the estimated number-right scores y’$\^$*/ as the estimated regression values of true scores with the same coordinate were moved to center points that were composed of such difference values with result of such parallel score moving procedure as above mentioned. We got the asymptotically normal distribution in Figure 5 that was represented as the optimal distribution of the optimal number-right scores so that we could decide the optimal proportion of number-right score in each item. Also by assumption that equivalence of two tests is closely connected to unidimensionality of a student’s ability. we introduce new definition of trait score to evaluate such ability in each item. In this study there are much limitations in getting the real true scores and in analyzing data of the bivariate error model. However, even with these limitations we believe that this study indicates that the estimation of optimal number right scores by using this enumeration procedure could be easily achieved.

• 대한토목학회논문집
• /
• 제38권3호
• /
• pp.387-393
• /
• 2018

기후변화의 영향으로 극심한 가뭄에 의한 피해가 증가하고 있으며, 이러한 피해를 줄이기 위하여 극한 가뭄에 대한 정량적인 분석이 필요하다. 따라서 본 연구에서는 극한 가뭄의 위험도에 대한 정량적 분석을 위해 임계수준방법을 측우기 강우자료, 관측 강우자료, 미래 기후변화 시나리오 강우 자료에 적용하여 가뭄사상을 정의하고 가뭄의 지속기간과 심도를 도출하였다. 또한, 코플라 함수를 활용하여 가뭄 지속기간 및 심도를 동시에 고려하는 이변량 가뭄빈도해석을 실시하였다. 이변량 가뭄빈도곡선을 바탕으로 과거 현재 미래에 대한 위험도를 산정했으며, 과거 및 현재를 기준으로 미래의 극한 가뭄에 대한 위험도를 분석하였다. 그 결과 과거 및 현재에 비해 미래의 평균 가뭄 지속기간은 짧게 나타났으나 평균 가뭄 심도는 매우 크게 나타났다. 따라서 미래에는 짧은 기간의 심한 가뭄들이 발생할 것으로 예측된다. 또한, 최대가뭄의 위험도를 분석한 결과 미래의 최대 가뭄 위험도는 과거 및 현재에 비해 각각 1.39~1.94배, 1.33~1.81배 큰 것으로 확인되었다. 최종적으로 미래에서 과거 및 현재의 기왕최대 가뭄 이상의 극한 가뭄위험도는 0.989와 1.0 사이의 범위를 가지는 것으로 나타나, 미래에는 극한 가뭄의 발생확률이 높은 것으로 판단된다.