• 한국군사과학기술학회지
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• 제15권4호
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• pp.435-441
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• 2012

This paper provides simulation-based results of effect analysis of sample size and sampling periods on accuracy of reliability estimation methods using multiple comparisons with analysis of variance. Sum of squared errors in estimated reliability measures were evaluated through applying seven estimation methods for one-shot systems to simulated quantal-response data. Analysis of variance was implemented to investigate change in these errors according to variations of sample size and sampling periods for each estimation method, and then the effect analysis on accuracy in reliability estimation was performed using multiple comparisons based on sample size and sampling periods. An efficient way to allocate both sample size and sampling periods for reliability estimation tests of one-shot systems is proposed in this paper from the effect analysis results.

• 콘크리트학회지
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• 제11권2호
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• pp.157-165
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• 1999

콘크리트 휨부재의 극한강도를 예측할 떼에는 부재의 크기효과는 고려하지 않는 것이 일반적이다. 그러나 콘크리트는 여러 형태의 하중에 대하여 부재의 크기가 증가함에 따라 강도가 감소하는 크기효과를 항상 나타낸다. 따라서 본 논문에서는 휨압축 부재에 대한 실험을 수행하여 크기효과를 검토하고자 한다. 이를 위하여 축 압축력과 휨모멘트를 동시에 받는 일련의 C형 공시체에 대한 실험을 수행하였다. 공시체의 크기는 3가지 였으며 콘크리트의 압축강도는 528 kg/$cm^2$로 하였다. 실험결과로부터 부재의 크기가 증가함에 따라 파괴시의 휨압축 강도가 감소하는 크기효과가 존재하며, 실린더 공시체의 축압축 강도보다 강도감소 현상이 더욱 분명함을 알 수 있었다. 최종적으로 실험자료에 대한 회귀분석을 수행하여 이를 예측할 수 있는 모델식을 제안하였다.

• 한국방재학회 논문집
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• 제3권2호
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• pp.139-145
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• 2003

본 연구에서는 다양한 크기의 원환에 따른 균등원통교각 주위의 세굴심을 분석하여 세굴심 감소효과 및 원환의 적정 크기를 제시하였다. 이를 위하여 수리모형실험을 실시하였으며, 교각에 원환을 설치한 경우 원환을 하상 위보다 하상 아래에 설치하는 것이 더욱 효과적이었으며, 원환의 크기가 클수록 세굴심 감소 효과가 뚜렷하였다. 교각 직경에 대한 원환 직경의 비(W/D)가 2인 경우 약 67% 세굴심이 감소하였으며, 퇴적고는 약 70%정도 증가하였다. 세굴심 감소 효과, 세굴공 및 퇴적고의 분석 결과를 토대로 W/D=2인 원환을 최적 크기로 제안하였다.

• KEPCO Journal on Electric Power and Energy
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• 제5권3호
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• pp.201-207
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• 2019

An anchorage system is essential for most reinforced concrete structures to connect building components. Therefore, the prediction of strength of the anchor is very important issue for safety of the structures themselves as well as structural components. The prediction models in existing design codes are, however, not applicable for large anchors because they are based on the small size anchors with diameters under 50 mm. In this paper, new prediction models for strength of a single anchor, especially the tensile strength of a single anchor, is developed from the experimental results with consideration of size effect. Size effect in the existing models such as ACI or CCD method is based on the linear fracture mechanics which is very conservative way to consider the size effect. Therefore, new models are developed based on the nonlinear fracture mechanics rather than the linear fracture mechanics for more reasonable prediction. New models are proposed by the regression analysis of the experimental results and it can predict the tensile strength of both small and large anchors.

• 산업경영시스템학회지
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• 제42권2호
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• pp.62-68
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• 2019

The growth and employment effects of R&D investment were analyzed according to business size, export value and manufacturing sectors so as to suggest improvement directions for effective industry policies. The effect of R&D investment was considered simultaneously from the two perspectives of growth and employment effect, and the causality analysis was carried out by using a path analysis. The result of the path analysis confirmed significant differences in the growth effect of R&D investment depending on business size. However, the effect of increasing employment was difficult to obtain statistically significant results for any various combinations of business size and export value. This is a mixture of directions for the effects of R&D investment on employment, which could be due to the failure to consider appropriate time lags between investment and effect. Efficiency analysis by industry sectors confirmed significant differences in efficiency depending on business size, but differences depending on export value were difficult to identify. In order to derive improvement policy by industry sector according to business size and export value, the direction of selective support policy and universal support policy was derived for six industry groups by combining the return to scale in the efficiency analysis and R&D concentration. Hirschman-Herfindahl index is used for calculating R&D concentration.

• 콘크리트학회논문집
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• 제14권6호
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• pp.934-941
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• 2002

철근콘크리트 보 단면의 극한강도를 예측할 때에는 부재의 크기를 고려하지 않는 것이 일반적이다. 그러나 부재 단면의 휨압 축강도는 부재의 크기가 증가함에 따라 항상 감소하게 된다. 본 연구에서는 철근콘크리트 보에 대한 실험적 고찰을 통해 휨압축강도의 크기효과를 살펴보고 이에 대한 적절한 모델식을 제시하고자 한다. 보의 유효깊이(d$\approx$15, 30, 60cm)를 주요 매개변수로 하였으며 전단스팬/유효깊이(a/d)는 3.0으로 하였고 시편의 폭은 20 cm로 일정하게 하여 휨하중을 가하며 실험을 수행하였다. 실험에서 구한 하중, 변형률, 및 보의 처짐 등을 이용하여 휨압축응력-변형률 관계를 3차의 비선형 다항식을 이용한 회귀분석을 수행하여 구하였다. 분석 결과 보의 유효깊이가 증가함에 따라 휨압축강도, 최대 휨압축응력에서의 변형률, 그리고 극한변형률이 감소하며 취성적인 파괴거동을 나타내었다. 그리고 설계기준에서 제시하고 있는 $\beta$l값과 보의 극한 변형률 값에 대해서도 크기효과가 있으므로 이에 대한 검토가 필요하다고 판단된다. 마지막으로 수정된 크기효과법칙을 사용하여 철근콘크리트 보의 휨압축강도에 대한 크기 효과모델식을 제시하였다.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.778-784
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• 2015

얕은기초의 지지력과 침하에 미치는 크기효과를 파악하기 위해 평판과 다양한 크기의 기초를 가정하여 유한요소해석을 수행하고 이론식에 의한 결과와 비교해 보았다. 해석에서 고려한 평판에 대하여 유한요소해석결과 얻은 극한지지력은 이론식에 의한 극한지지력에 비해 큰 차이를 보이지 않았다. 수치해석결과에 따르면 모래지반에 놓인 띠기초의 극한지지력은 이론식에 의한 극한지지력보다 크기효과의 영향을 크게 받았으며 점토지반에 놓인 띠기초의 경우 크기효과의 영향은 없었다. 정사각형기초에 대해서는 대체로 기초지반의 종류에 관계없이 크기효과의 영향이 없었다. 수치해석결과에 따르면 기초의 침하량은 기초지반 종류에 관계없이 이론식과는 달리 크기효과의 영향을 받아 대체로 그 크기가 기초폭에 비례하였다.

• 임상간호연구
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• 제25권3호
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• pp.221-236
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• 2019

Purpose: The purpose of this study was to systematically review and identify factors relevant to the positive psychological capital of clinical nurses. Methods: These was no limit on year of publication. Articles related to Korean clinical nurses were retrieved from computerized database using a manual search. A systematic review was conducted based on the PRISMA flow. The total correlational effect size (ESr) for each related factor was calculated from Fisher's Zr. Funnel plots, fail-safe numbers, and Egger regression tests were used to evaluate publication bias in meta-analysis studies. The correlational effect size of 25 studies was analyzed through meta-analysis using Comprehensive Meta-Analysis software 3.0 (CMA). Results: The review included 25 studies. In the systematic review, 14 demographic factors and 46 organizational factors were found to be influential. Eleven factors (6 demographic factors and 5 organizational factors) were appropriate for meta-analysis. The overall effect size was .26. The demographic total correlation effect size of related factors was .20 and the total effect size of organization was .46. Organizational commitment (ESr=.38) and job satisfaction (ESr=.54) were statistically positively related variables. Negative variables were burnout (ESr=-.61), turnover intention (ESr=-.41) and workplace bullying (ESr=-.33). The total effect size of the organizational factors was larger than the demographic total effect size. There was no publication bias except for demographic variables. Conclusion: Organizational factors and adjustable variables have a significant impact on positive psychological capital. The results of this study support the need for development of interventions focusing on organizational factors.

• 한국세라믹학회지
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• 제32권2호
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• pp.163-170
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• 1995

Sample size effect on ferromagnetic resonance (FMR) in polycrystalline MgFe2O4 has been investigated. The signal intensity (SI), resonance field (Hres) and line width (ΔH) were found to increase proportionally to r3 with the increase of sample radius. The r3-depencence of SI means the complete penetration of rf-field into the sample, and the broadening of ΔH due to the sample size appears to be closely related to the amount of scattering sources like pores. Meanwhile, the values of Hres (0) and ΔH (0) obtained by extrapolating the data of Hres (r) and ΔH (r) measured at several sizes to r=0, were in good agreement with those calculated using the Schlomann's equations for internal field and ΔH, respectively. This result indicates that the discrepancy between the measured FMR parameters and those calculated by Schlomann's equation could be ascribed to the effect of sample size. Thus it is suggested that the size effect on FMR should be removed for the analysis of the FMR parameters. Meanwhile, our result for the size dependance of ΔH was found to be contradictory to those reported by Dionne, where ΔH 1/r at a given surface roughness. This discrepancy appears to arise from the difference in the definition of reading the line width.

• Steel and Composite Structures
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• 제22권6호
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• pp.1301-1336
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• 2016

In this paper, the free vibrations of a short cylindrical nanotube made of piezoelectric material are studied based on the consistent couple stress theory and using the shear deformable cylindrical theory. This new model has only one length scale parameter and can consider the size effects of nanostructures in nanoscale. To model size effects in nanoscale, and considering the nanotube material which is piezoelectric, the consistent couple stress theory is used. First, using Hamilton's principle, the equations of motion and boundary condition of the piezoelectric cylindrical nanoshell are developed. Afterwards, using Navier approach and extended Kantorovich method (EKM), the governing equations of the system with simple-simple (S-S) and clamped-clamped (C-C) supports are solved. Afterwards, the effects of size parameter, geometric parameters (nanoshell length and thickness), and mechanical and electric properties (piezoelectric effect) on nanoshell vibrations are investigated. Results demonstrate that the natural frequency on nanoshell in nanoscale is extremely dependent on nanoshell size. Increase in size parameter, thickness and flexoelectric effect of the material leads to increase in frequency of vibrations. Moreover, increased nanoshell length and diameter leads to decreased vibration frequency.