• Steel and Composite Structures
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• v.42 no.2
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• pp.221-241
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• 2022

Perfobond rib connectors are widely used in composite structures to achieve the composite action between the steel and the concrete, and empirical expressions for their strength and secant stiffness have been obtained by numerical simulations or push-out tests. Since perfobond connections are generally in an elastic state in the service process and the structural analysis are always based on the elastic properties of the members, the secant stiffness is not applicable for the normal structural analysis. However, the tangent stiffness of perfobond connections has not been introduced in previous studies. Moreover, the perfobond connections are bearing tension and shear force simultaneously when the composite beams subjected to torque or local loads, but the current studies fail to arrive at the elastic stiffness considering the combined effects. To resolve these discrepancies, this paper investigates the initial elastic stiffness of perfobond connections under combined forces. The calculation method for the elastic stiffness of perfobond connections is analyzed, and the contributions of the perfobond rib, the perforating rebar and the concrete dowel are investigated. A finite element method was verified with a high value of correlation for the test results. Afterwards, parametric studies are carried out using the reliable finite element analysis to explore the trends of several factors. Empirical equations for predicting the initial elastic stiffness of perfobond connections are proposed by the numerical regression of the data extracted by parametric studies. The equations agree well with finite element analysis and test results, which indicates that the proposed empirical equations reflect a high accuracy for predicting the initial elastic stiffness of perfobond connections.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2005.09a
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• pp.395-398
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• 2005

Genetic association case-control studies using DNA pools are efficient ways of detecting association between a marker allele and disease status. DNA pooling is an efficient screening method for locating susceptibility genes associated with the disease. However, DNA pooling is efficient only when allele frequency estimation is done precisely and accurately. Through the evaluation of empirical type I errors and empirical powers by simulation, we will evaluate the methods that correct for preferential amplification of nucleotides when estimating the allele frequency of single-nucleotide polymorphisms.

• Journal of Korean Society for Quality Management
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• v.23 no.3
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• pp.45-56
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• 1995

The method of lot by lot quality protection for sampling inspection by variables is widely used in quality control. In case of sampling inspection being done repeatedly, one can use the information from the previous sampling inspection to improve current estimates. This article shows that empirical Bayes estimator is superior to the usual sample mean in repeated sampling inspection by variables.

• Communications for Statistical Applications and Methods
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• v.8 no.1
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• pp.219-227
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• 2001

Another approach (multi-parameter measurement method) of interlaboratory studies of test methods is presented. When the unrestricted normal likelihood for the fixed latent variable model is unbounded, we propose a me쇙 of restricting the parameter space by formulating realistic alternative hypothesis under which the likelihood is bounded. A simulation study verified the claim of conservatism of level of significance based on assumptions about central chi-square distributed test statistics and on Bonferroni approximations. We showed a randomization approach that furnished empirical significance levels would be better than a Bonferroni adjustment.

• IE interfaces
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• v.5 no.1
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• pp.61-74
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• 1992

Recognizing the lack of empirical studies on the returns to R & D investment in Korean firms, this paper analyzes the relationships between R & D investment and corporate performances measured by sales growth rate, profit rate and PER. The data used here are from 167 firms in 8 different industries covering the period from 1985 to 1989. The results show that the profit rate is strongly correlated with R & D investment. But unlike the results of most studies previously done in the U.S., R & D investment only weakly and insignificantly correlated with sales growth and PER.

• Journal of the Korean Statistical Society
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• v.30 no.3
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• pp.481-498
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• 2001

Empirical Bayes procedure of nonparametric estiamtion of cumulative hazard rates based on censored data is considered using the beta process priors of Hjort(1990). Beta process priors with unknown parameters are used for cumulative hazard rates. Empirical Bayes estimators are suggested and asymptotic optimality is proved. Our result generalizes that of Susarla and Van Ryzin(1978) in the sensor that (i) the cumulative hazard rate induced by a Dirichlet process is a beta process, (ii) our empirical Bayes estimator does not depend on the censoring distribution while that of Susarla and Van Ryzin(1978) does, (iii) a class of estimators of the hyperprameters is suggested in the prior distribution which is assumed known in advance in Susarla and Van Ryzin(1978). This extension makes the proposed empirical Bayes procedure more applicable to real dta sets.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1305-1316
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• 2021

In this study, a new empirical formula for 2D transverse dispersion coefficient was developed using the results of previous tracer test studies, and the performance of the formula was evaluated. Since many tracer test studies have been conducted under the conditions where the width-to-depth ratio is less than 50, the existing empirical formulas developed using these imbalanced tracer test results have limitations in applying to rivers with a width-to-depth ratio greater than 50. Therefore, in order to develop an empirical formula for transverse dispersion coefficient using the imbalanced tracer test data, the Synthetic Minority Oversampling TEchnique (SMOTE) was used to oversample new data representing the properties of the existing tracer test data. The hydraulic data and the transverse dispersion coefficients in conditions of width-to-depth ratio greater than 50 were oversampled using the SMOTE. The reliability of the oversampled data was evaluated using the ROC (Receiver Operating Characteristic) curve. The empirical formula of transverse dispersion coefficient was developed including the oversampled data, and the performance of the results were compared with the empirical formulas suggested in previous studies using R². From the comparison results, the value of R² was 0.81 for the range of W/H < 50 and 0.92 for 50 < W/H, which were improved accuracy compared to the previous studies.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.199-209
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• 2017

The measurement of business performance is important to secure the competitiveness of construction companies. Therefore, the purpose of this study is to analyze what is needed to increase the competitiveness of small & medium construction companies. In order to analyze efficiently, this study reconfirms the effectiveness of Key Performance Indicators(KPI) of construction companies selected from previous studies. The empirical analysis to find differences of KPI between small & medium construction companies and big construction companies is performed using the 4,286 construction company samples extracted by 'KIS-Value Data Base'. The results of the empirical analysis show that there are significant differences in characteristics of KPI between small & medium construction companies and big construction companies. Particularly, small & medium construction companies are relatively insufficient to invest for the purpose of preparation for future and long-term growth. Additionally, empirical tests reconfirm that most of the KPIs from previous survey studies are suitable as a performance indicators. The contribution of this study is to analyze empirically small & medium construction company's strong & weak points and the effectiveness of KPIs derived from previous studies.

• Journal of the Korean Home Economics Association
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• v.35 no.6
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• pp.275-288
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• 1997

This paper has two purposes. the one was to find empirical patterns of rural and urban elderly's leisure activities, and the other was to test the effects of elderly's leisure activities on life satisfaction. the data were collected for 319 respondents aged over 50s who resided in Jeonbuk rural and urban areas. Through exploratory factor analysis, we found ten patterns of leisure activities. In addition, we conducted multiple regression analysis to test net effects of those leisure activities on life satisfaction. the results indicate that even no one pattern of leisure activities significantly influences the elderly's life satisfaction, controlling for social correlates (consisted of social structural, family relationship, personality, and socio-economic demographic variables). Rather, the respondent's level of health, level of economic status, and positive relationship with adult children have significant net effects on respondent's life satisfaction. This result suggests that the positive relationship between leisure activities and life satisfaction in the existing empirical studies might be spurious. We recommend that the further studies should conduct survey and analyze the data for affluent elderly residing in more urbanized areas.

• The Journal of Information Systems
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• v.16 no.3
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• pp.69-90
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• 2007

Recently, Service Level Management(SLM) including SLA has been developing to manage the level of information systems service. Although previous SLA studies have provided the conceptual model and critical success factors, the studies have not tested the effectiveness of the SLA by way of the empirical study. In this study, we applied an innovation decision making theory to our model and tested an empirical study using of a firm survey data. We suggested a SLM model, which consists of SLA planning, application, management dimensions. We found that the SLM's management stage has an impact on performance, whereas SLM's planning and application has not. At each sub dimensional analysis, there are found that adequate SLA indicators in the application stage influences performance and change management and feedback & reporting in the management stage influence performance.