• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.6
• /
• pp.804-811
• /
• 2010

The fatigue crack propagation is stochastic in nature, because the variables affecting the fatigue behavior are random and have uncertainty. Therefore, the fatigue life prediction is critical for the design and the maintenance of many structural components. In this study, fatigue experiments are conducted on the specimens of magnesium alloy AZ31 under various conditions such as thickness of specimen, the load ratio and the loading condition. The probability distribution fit to the fatigue failure life are investigated through a probability plot paper by these conditions. The probabilities of failure at various conditions are also estimated. The fatigue design life is predicted by using the Weibull distribution.

• Journal of environmental and Sanitary engineering
• /
• v.23 no.4
• /
• pp.83-93
• /
• 2008

The non-linear least squares model(NLSM) has long been the standard technique used by hydrologists for constructing rating curves. The reasons for its adaptation are vague, and its appropriateness as a method of describing discharge measurement uncertainty has not been well investigated. It is shown in this paper that the classical method of NLSM can model only a very limited class of variance heterogeneity. Furthermore, this lack of flexibility often leads to unaccounted heteroscedasticity, resulting in dubious values for the rating curve parameters and estimated discharge. By introducing a heteroscedastic maximum likelihood model(HMLM), the variance heterogeneity is treated more generally. The maximum likelihood model stabilises the variance better than the NLSM approach, and thus is a more robust and appropriate way to fit a rating curve to a set of discharge measurements.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.18 no.4
• /
• pp.395-400
• /
• 2009

As the variables affecting the fatigue behavior have uncertainty, the fatigue crack propagation is stochastic in nature. Therefore, the fatigue life prediction is critical for the design and the maintenance of many structural components. In this study, fatigue experiments are conducted on the specimens of magnesium alloy under the different thicknesses of specimen. The effects of specimen thickness on the probability distribution of the fatigue crack propagation life and the crack size are estimated experimentally. The probability distribution of the crack size and the fatigue life for different specimen thicknesses are investigated by Anderson-Darling test and the best fit for those probability distributions are also presented.

• Korean Management Science Review
• /
• v.30 no.1
• /
• pp.149-165
• /
• 2013

This study empirically investigated the changes of performance evaluation systems under the environment of supply-chain e-commerce. The objectives of e-commerce include obtaining financial profit, internal innovation through processes integration, learning with information flow, and customer satisfaction through quick response. These objectives are generally consistent with the four evaluation measures of balanced scorecard(BSC). This study, first, demonstrated that perceived environmental uncertainty(PEU) has a significant effect on the adoptions of e-commerce and BSC, and severe competition positively influences the use of e-commerce. With cluster analysis and subgroup analysis, we also showed that under the high adoption levels of e-commerce, the high utilization of BSC can improve the supply-chain performance of a firm. In addition, it was found that the use of e-commerce indirectly and significantly affects supply-chain performance through inter-organizational information flow, and the supply-chain performance of a firm leads to the improvement of organizational performance.

• Journal of the Korean Data and Information Science Society
• /
• v.27 no.1
• /
• pp.245-254
• /
• 2016

Many surveys provide categorical data and there may be one or more missing categories. We describe a nonignorable nonresponse model for the analysis of two-way contingency tables from small areas. There are both item and unit nonresponse. One approach to analyze these data is to construct several tables corresponding to missing categories. We describe a hierarchical Bayesian model to analyze two-way categorical data from different areas. This allows a "borrowing of strength" of the data from larger areas to improve the reliability in the estimates of the model parameters corresponding to the small areas. Also we use a nonignorable nonresponse model with Bayesian uncertainty analysis by placing priors in nonidentifiable parameters instead of a sensitivity analysis for nonidentifiable parameters. We use the griddy Gibbs sampler to fit our models and compute DIC and BPP for model diagnostics. We illustrate our method using data from NHANES III data on thirteen states to obtain the finite population proportions.

• Journal of Korea Society of Industrial Information Systems
• /
• v.16 no.3
• /
• pp.101-119
• /
• 2011

A empirical study investigating firms' attitudes and behaviors regarding of RFID technology within supply chain is very limited. Thus, this study examines the determinants influencing firms' adoption and performance of RFID within the supply chain. Particularly, this study focus on the impacts of the companies' relationship characteristics, including strategic fit, interdependence, compatibility, and long-term orientation affection RFID adoption and performance within the supply chain. Furthermore, the study includes environment uncertainty as a moderating effect between relationship characteristics and RFID adoption. The proposed research model was tested using structural equation modeling from 227 employees. Results of this study support the proposed hypotheses. The implication of this study suggest a new theoretical framework explaining RFID adoption and performance with the supply chain.

• Ocean Systems Engineering
• /
• v.9 no.3
• /
• pp.287-328
• /
• 2019

Comprehensive understanding of the flood risk assessments via frequency analysis often demands multivariate designs under the different notations of return periods. Flood is a tri-variate random consequence, which often pointing the unreliability of univariate return period and demands for the joint dependency construction by accounting its multiple intercorrelated flood vectors i.e., flood peak, volume & durations. Selecting the most parsimonious probability functions for demonstrating univariate flood marginals distributions is often a mandatory pre-processing desire before the establishment of joint dependency. Especially under copulas methodology, which often allows the practitioner to model univariate marginals separately from their joint constructions. Parametric density approximations often hypothesized that the random samples must follow some specific or predefine probability density functions, which usually defines different estimates especially in the tail of distributions. Concentrations of the upper tail often seem interesting during flood modelling also, no evidence exhibited in favours of any fixed distributions, which often characterized through the trial and error procedure based on goodness-of-fit measures. On another side, model performance evaluations and selections of best-fitted distributions often demand precise investigations via comparing the relative sample reproducing capabilities otherwise, inconsistencies might reveal uncertainty. Also, the strength & weakness of different fitness statistics usually vary and having different extent during demonstrating gaps and dispensary among fitted distributions. In this literature, selections efforts of marginal distributions of flood variables are incorporated by employing an interactive set of parametric functions for event-based (or Block annual maxima) samples over the 50-years continuously-distributed streamflow characteristics for the Kelantan River basin at Gulliemard Bridge, Malaysia. Model fitness criteria are examined based on the degree of agreements between cumulative empirical and theoretical probabilities. Both the analytical as well as graphically visual inspections are undertaken to strengthen much decisive evidence in favour of best-fitted probability density.

• Korean Security Journal
• /
• no.31
• /
• pp.25-45
• /
• 2012

Based on the results of preceding researches that the uncertainty perceived by the private security guards about their roles exerts direct effects on the business performance of the security industry, it needs to preferentially examine the degree of authority that the private security guards have. The suitability of the psychological empowerment criteria for measuring this for private security guards, however, has not yet been established up to the present, so it can be said that the validity of the information has not yet been established. Accordingly, as the psychological empowerment criteria of private security guards, this research examined the suitability of items, reliability of items, the level of difficulty of items, and the item goodness of fit from the viewpoint of the appropriateness of category of responses, and it is summarized as follows. First, in the self-determinism factor of the psychological empowerment criteria, Item 11 was found to be an unsuitable item, so it is proper that Item 11 should be deleted when examining the psychological empowerment of private security guards from now on. Second, the item reliability of the psychological empowerment criteria was high, so the consistency of the results is shown even if the data are collected from the other private security guards. Third, they feel that it is hard to respond to Item 12 while they perceive that Item 1 is the easiest, and the level of items of the psychological empowerment criteria is evenly distributed. Fourth, it was established that the 5-point categories of the psychological empowerment criteria were suitable to the private security guards.

• Journal of Korean Academy of Nursing
• /
• v.38 no.1
• /
• pp.140-151
• /
• 2008

Purpose: The purpose of this study was to understand the meanings and nature of living in the world among cancer patients. The present study adopted a hermeneutic phenomenological method which was developed by van Manen. Method: The participants for this study were 5 men and 6 women, who were over the age of 20 with admission or a follow up visit in the medical or surgical department. Data were collected by using in-depth interviews and observations from February to September, 2007. The contents of the interviews were tape-recorded with the consent of the subject. Result: The essential themes that fit into the context of the 4 existential grounds of body, time, space and other people were: a body that cannot be restored, a body that endures and lives, waiting in uncertainty, a valued calculation for the living day, being in a world of invisible power, reestablishing relationships, and reflection on his or her life. Conclusion: These findings revealed that living in the world is affected to varying degrees by the cancer. It is important for nurses to identify and take care of disabilities and to support the reorientation in the disintegrated life situation. The result of this study can give nurses some insight into these experiences and help promote empathetic care.

• International Journal of Highway Engineering
• /
• v.20 no.2
• /
• pp.119-126
• /
• 2018

PURPOSES : The purpose of this study is to develop a crash prediction model at signalized intersections, which can capture the randomness and uncertainty of traffic accident forecasting in order to provide more precise results. METHODS : The authors propose a random parameter (RP) approach to overcome the limitation of the Count model that cannot consider the heterogeneity of the assigned locations or road sections. For the model's development, 55 intersections located in the Daejeon metropolitan area were selected as the scope of the study, and panel data such as the number of crashes, traffic volume, and intersection geometry at each intersection were collected for the analysis. RESULTS : Based on the results of the RP negative binomial crash prediction model developed in this study, it was found that the independent variables such as the log form of average annual traffic volume, presence or absence of left-turn lanes on major roads, presence or absence of right-turn lanes on minor roads, and the number of crosswalks were statistically significant random parameters, and this showed that the variables have a heterogeneous influence on individual intersections. CONCLUSIONS : It was found that the RP model had a better fit to the data than the fixed parameters (FP) model since the RP model reflects the heterogeneity of the individual observations and captures the inconsistent and biased effects.