• 동력기계공학회지
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• 제4권2호
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• pp.40-45
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• 2000

Some engineering materials are often known to have considerable spatial variation in their resisting strength and other properties. The objective of this study is to investigate the averaging effect and the applicability of extremal statistic for the statistical size effect. In the present study, it is assumed that the material property is a stationary random process in space. The theoretical autocorrelation function of the material strength are discussed for several correlation lengths. And, in order to investigate the statistical size effect, the material properties was simulated by using the non-Gaussian random process method. The material properties were plotted on the Weibull probability papers. The main results are summarized as follows: The autocorrelation function of the material properties are almost independent of the averaging length. The variance decreases with increasing the averaging length. As correlation length is smaller, the slope is larger. And also, it was found that Weibull statistics based on the weakest-link model could not explain the spatial variation of material properties with respect to the size effect satisfactory.

• 한국구조물진단유지관리공학회 논문집
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• 제7권4호
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• pp.129-137
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• 2003

케이블 구조물에 사용되는 케이블은 길이가 길다는 특징을 갖고 있으므로 케이블의 피로 데이터 처리를 위해서는 일반적으로 구조물을 구성하는 강재 요소에 적용되는 통계모델과는 다른 모델을 적용하는 것이 합리적이라 할 수 있다. 즉 케이블과 같이 길이가 긴 요소에서 피로수명에 크게 영향을 미치는 시편의 길이를 포함할 수 있는 모델, 즉 대수정규분포모델과 기존의 극치분포모델을 길이효과를 고려할 수 있도록 유도하여 기존의 케이블 피로 실험 데이터에 적용해 봄으로써, 케이블이 사용되고 있는 실제 구조물에서 케이블의 피로거동을 예측 또는 평가하는 데에 적합한 모델을 제시한다.

• Korean Journal of Mathematics
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• 제23권1호
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• pp.29-36
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• 2015

A signed digraph S is the digraph D by assigning signs 1 or -1 to each arc of D. The base of S is the minimum number k such that there is a pair walks which have the same initial and terminal point with length k, but different signs. In this paper we show that for $n{\geq}5$ the upper bound of the base of a primitive non-powerful signed tournament Sn, which is the signed digraph by assigning 1 or -1 to each arc of a primitive tournament $T_n$, is max{2n + 2, n+11}. Moreover we show that it is extremal except when n = 5, 7.

• 보건행정학회지
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• 제23권1호
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• pp.35-43
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• 2013

Background: Diagnosis procedure combination (DPC) has recently been introduced in Korea as a demonstration project and it has aimed the improvement of accuracy in bundled payment instead of Diagnosis related group (DRG). The purpose of this study is to investigate that the model of end-stage liver disease (MELD) score as the severity classification of liver diseases is adequate for improving reimbursement of DPC. Methods: The subjects of this study were 329 patients of liver disease (Korean DRG ver. 3.2 H603) who had discharged from National Health Insurance Corporation Ilsan Hospital which is target hospital of DPC demonstration project, between January 1, 2007 and July 31, 2010. We tested the cost differences by severity classifications which were DRG severity classification and clinical severity classification-MELD score. We used a multiple regression model to find the impacts of severity on total medical cost controlling for demographic factor and characteristics of medical services. The within group homogeneity of cost were measured by calculating the coefficient of variation and extremal quotient. Results: This study investigates the relationship between medical costs and other variables especially severity classifications of liver disease. Length of stay has strong effect on medical costs and other characteristics of patients or episode also effect on medical costs. MELD score for severity classification explained the variation of costs more than DRG severity classification. Conclusion: The accuracy of DRG based payment might be improved by using various clinical data collected by clinical situations but it should have objectivity with considering availability. Adequate compensation for severity should be considered mainly in DRG based payment. Disease specific severity classification would be an alternative like MELD score for liver diseases.