• Safety and Health at Work
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• v.7 no.2
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• pp.124-129
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• 2016

Background: Work-related fatigue has a strong impact on performance and safety but so far, no agreed upon method exists to detect and quantify it. It has been suggested that work-related fatigue cannot be quantified with just one test alone, possibly because fatigue is not a uniform construct. The purpose of this study is therefore to measure work-related fatigue with multiple tests and then to determine the underlying factorial structure. Methods: Twenty-eight employees (mean: 36.11; standard deviation 13.17) participated in five common fatigue tests, namely, posturography, heart rate variability, distributed attention, simple reaction time, and subjective fatigue before and after work. To evaluate changes from morning to afternoon, t tests were conducted. For further data analysis, the differences between afternoon and morning scores for each outcome measure and participant (${\Delta}$ scores) were submitted to factor analysis with varimax rotation and each factor with the highest-loading outcome measure was selected. The ${\Delta}$ scores from tests with single and multiple outcome measures were submitted for a further factor analysis with varimax rotation. Results: The statistical analysis of the multiple tests determine a factorial structure with three factors: The first factor is best represented by center of pressure (COP) path length, COP confidence area, and simple reaction time. The second factor is associated with root mean square of successive difference and useful field of view (UFOV). The third factor is represented by the single ${\Delta}$ score of subjective fatigue. Conclusion: Work-related fatigue is a multidimensional phenomenon that should be assessed by multiple tests. Based on data structure and practicability, we recommend carrying out further studies to assess work-related fatigue with manual reaction time and UFOV Subtest 2.

• Safety and Health at Work
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• v.13 no.2
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• pp.170-179
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• 2022

Background: The vulnerability of international migrant workers is on the rise, affecting the frequency of occupational accidents at workplaces worldwide. If migrant workers are managed in the same way as native workers, the consequences on safety assurance and risk management will be significant. This study aimed to develop the vulnerability factor model for migrant workers in seafood processing industries because of significant risk-laden labor of Thailand, which could be a solution to control the risk effectively. Methods: A total of 569 migrant workers were surveyed (432 Burmese and 137 Cambodian), beginning with 40 initial vulnerability factors identified in the questionnaire established from experts. The data were analyzed through descriptive analysis; exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were used to ascertain the model. Results: The result of content validity >0.67 and the Cronbach's alpha of 0.957 specified the high reliability of 40 factors. The EFA indicated a total variance of 65.49%. The final CFA validated the model and had an empirical fitting; chi-square = 85.34, Adjust Goodness-of-Fit Index = 0.96, and root mean square error of approximation = 0.016. The structure concluded with three dimensions and 18 factors. Dimension 1 of the structure, "multicultural safety operation," contained 12 factors; Dimension 2, "wellbeing," contained four factors; and Dimension 3, "communication technology," contained two factors. Conclusion: The vulnerability factor structure developed in this study included three dimensions and 18 factors that were significantly empirical. The knowledge enhanced safety management in the context of vulnerability factor structure for migrant workers at the workplace.

• Geomechanics and Engineering
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• v.6 no.1
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• pp.1-15
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• 2014

In this study, artificial neural network (ANN) and multiple regression (MR) models were developed to predict the critical factor of safety ($F_s$) of the homogeneous finite slopes subjected to earthquake forces. To achieve this, the values of $F_s$ in 5184 nos. of homogeneous finite slopes having different slope, soil and earthquake parameters were calculated by using the Simplified Bishop method and the minimum (critical) $F_s$ for each of the case was determined and used in the development of the ANN and MR models. The results obtained from both the models were compared with those obtained from the calculations. It is found that the ANN model exhibits more reliable predictions than the MR model. Moreover, several performance indices such as the determination coefficient, variance account for, mean absolute error, root mean square error, and the scaled percent error were computed. Also, the receiver operating curves were drawn, and the areas under the curves (AUC) were calculated to assess the prediction capacity of the ANN and MR models developed. The performance level attained in the ANN model shows that the ANN model developed can be used for predicting the critical $F_s$ of the homogeneous finite slopes subjected to earthquake forces.

• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.107-114
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• 2009

Human walking is essential and important mean of transportation. Pedestrian safety is recently important because accidents often happen while walking. This research is showing that Walking-environmental factors have effect on safety while walking. At first, exact 15 factors and conduct survey in the preceding research. After that, exact 4 important factors through factor analysis. At result of Multiple regression analysis, null hypothesis has proved to be true by satisfying therms which is F-value 9.211 and P-value 0.000. and come to the conclusion that walking-environmental factors influence pedestrian safety. 4 important factors can be listed by below. Pedestrian-road characteristic, landscape characteristic, commercial characteristic, walking characteristics by following influence. Especially, landscape characteristic and pedestrian-road characteristic can be vital factors.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.322-327
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• 2003

It is important to know the accurate radionuclide inventory of radioactive waste for the reliable management. However, estimation of radionuclide concentrations in drummed radioactive waste is difficult and unreliable because of difficulties of direct detection, high cost, and radiation exposure of sampling personnel. In order to overcome these difficulties, scaling factors (SFs) have been used to assess the activities of radionuclides that could not be directly analyzed. A radionuclide assay system has been operated at KORI site since 1996 and consolidated scaling factor method has played a dominant role in determination of radionuclides concentrations. However, some problems are still remained such as uncertainty of estimated scaling factor values, inaccuracy of analyzed sample values, and disparity between the actual and ideal correlation pairs and the others. Therefore, it needs to improve the accuracy of scaling factor values. The scope of this paper is focused on the improvement of accuracy and representativeness of calculated scaling factor values based on statistical techniques. For the selection of reliable activity determination method, the accuracy of estimated SF values for each activity determination method is compared. From the comparison of each activity determination methods, it is recommended that SF determination method should be changed from the arithmetic mean to the geometrical mean for more reliable estimation of radionuclide activity. Arithmetic mean method and geometric mean method are compared based on the data set in KORI system.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.51-57
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• 1998

It is common to assume identical allowable safety factors in static strength defined by mean stress and in fatigue, defined by stress amplitude. Under the load with asymmetrical cycles the safety factor is not the same. In this paper, with the consideration of unequal allowable safety (actors a general method for estimating fatigue reliability of a machine element under a combined state of stress is derived based on the theory proposed by Prof. Kececioglu and a normal distribution. The calculation of fatigue reliability fur limited life is discussed with example.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.119-126
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• 2002

A reliability analysis is performed to investigate the influence of the uncertainty from few in-situ samples and inherent heterogeneity of the ground on the probability of failure for a rock cut slope. The results are compared with those of deterministic slope stability analysis. The random variables used are unit weight of the rock, the angle of potential slope of failure, and cohesion and internal friction angle of joints. It was found that the rock slope in which the factor of safety satisfied the minimum safety factor in the deterministic analysis has high probability of failure in the reliability analysis when the weak geological strata are involved in the cut slope. The probability of failure of rock slope is most sensitive to the mean and standard deviation of cohesion in rock joint among the random soil parameters included in the reliability analysis. Sensitivities of the mean values are larger than those of standard deviations, which means that accurate estimation of the mean for the in-situ geotechnical properties is important.

• Geomechanics and Engineering
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• v.6 no.2
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• pp.99-115
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• 2014

Uncertainties in design variables and design equations have a significant impact on the safety of geotechnical structures like retaining walls and slopes. This paper presents a possible framework for obtaining the partial safety factors based on reliability approach for different random variables affecting the stability of a reinforced concrete cantilever retaining wall and a slope under static loading conditions. Reliability analysis is carried out by Mean First Order Second Moment Method, Point Estimate Method, Monte Carlo Simulation and Response Surface Methodology. A target reliability index ${\beta}$ = 3 is set and partial safety factors for each random variable are calculated based on different coefficient of variations of the random variables. The study shows that although deterministic analysis reveals a safety factor greater than 1.5 which is considered to be safe in conventional approach, reliability analysis indicates quite high failure probability due to variation of soil properties. The results also reveal that a higher factor of safety is required for internal friction angle ${\varphi}$, while almost negligible values of safety factors are required for soil unit weight ${\gamma}$ in case of cantilever retaining wall and soil unit weight ${\gamma}$ and cohesion c in case of slope. Importance of partial safety factors is shown by analyzing two simple geotechnical structures. However, it can be applied for any complex system to achieve economization.

• Toxicological Research
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• v.33 no.3
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• pp.225-231
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• 2017

National reference standards (NRSs) for biologics are established through potency estimation by a multi-center joint study of standard materials used in the approval process for national lot release and quality control of vaccines, blood products, and other biologics. In this study, a stability evaluation was conducted to determine whether the potency of NRSs for six blood products was being maintained at a consistent level in Korea. The present study conducted real-time stability tests via in-vivo/in-vitro bioassay on NRSs for blood coagulation factor VIII concentrate (2nd standard), antithrombin concentrate, prekallikrein activator, anti-hepatitis B immunoglobulin, blood coagulation factor IX concentrate, and anti-tetanus human immunoglobulin, as well as a trend analysis using cumulative annual results. The real-time stability test results showed that the mean potency of six NRSs was all within the control limit. In the trend analysis, the potency of NRS for blood coagulation factor VIII concentrate (2nd standard) showed a decreasing trend, while the potency of all other products had been stably maintained. The present study confirmed that the mean potency of NRSs for six blood products had been stably maintained in Korea. The findings of the present study establish a foundation that can ensure the quality of NRSs for biologics in Korea, and it is expected to make a major contribution to the supply of high-quality biologics.

• Safety and Health at Work
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• v.7 no.4
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• pp.326-330
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• 2016

Background: The Nordic Safety Climate Questionnaire-50 (NOSACQ-50) was developed by a team of Nordic occupational safety researchers based on safety climate and psychological theories. The aim of this study was to develop and validate the Persian version of NOSACQ-50 and assess the score of safety climate on a group of workers in a steel company in Iran. Methods: The Persian version of NOSACQ-50 was distributed among 661 employees of a steel company in Qazvin Province (Iran). Exploratory factor analysis (EFA) and confirmatory factor analysis were used to determine the dimensions of the questionnaire. The reliability of the questionnaire was assessed using Cronbach ${\alpha}$ coefficient. Pearson correlation test was applied to investigate the correlation between different dimensions. Results: The results of EFA showed that the Persian version of NOSACQ-50 consisted of six dimensions. The Cronbach ${\alpha}$ coefficient of the questionnaire was 0.94. The mean score of safety climate in all dimensions was 2.89 (standard deviation 0.60). Conclusion: The Persian version of NOSACQ-50 had a satisfactory validity for measuring safety climate in the studied Iranian population.