• Geomechanics and Engineering
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• v.31 no.4
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• pp.339-352
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• 2022

Studying slope stability is an important branch of civil engineering. In this way, engineers have employed machine learning models, due to their high efficiency in complex calculations. This paper examines the robustness of various novel optimization schemes, namely equilibrium optimizer (EO), Harris hawks optimization (HHO), water cycle algorithm (WCA), biogeography-based optimization (BBO), dragonfly algorithm (DA), grey wolf optimization (GWO), and teaching learning-based optimization (TLBO) for enhancing the performance of adaptive neuro-fuzzy inference system (ANFIS) in slope stability prediction. The hybrid models estimate the factor of safety (F_S) of a cohesive soil-footing system. The role of these algorithms lies in finding the optimal parameters of the membership function in the fuzzy system. By examining the convergence proceeding of the proposed hybrids, the best population sizes are selected, and the corresponding results are compared to the typical ANFIS. Accuracy assessments via root mean square error, mean absolute error, mean absolute percentage error, and Pearson correlation coefficient showed that all models can reliably understand and reproduce the F_S behavior. Moreover, applying the WCA, EO, GWO, and TLBO resulted in reducing both learning and prediction error of the ANFIS. Also, an efficiency comparison demonstrated the WCA-ANFIS as the most accurate hybrid, while the GWO-ANFIS was the fastest promising model. Overall, the findings of this research professed the suitability of improved intelligent models for practical slope stability evaluations.

• Korean Journal of Human Ecology
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• v.16 no.4
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• pp.711-722
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• 2007

The purpose of this study was to analyzed child care teachers' health state and a relationship between health promoting lifestyle and job stress of child care teachers. The subjects were 101 child care teachers in Busan. They responded to 'health state open ended question', 'health promoting lifestyle scale', and 'job stress scale'. For the analysis of the data, M(SD), frequencies, t-test, Pearson's correlation were run by using SPSS WIN computer program. The major findings of this study were as follows; First, the most uncomfortable symptoms of child care teacher's physical health state was respiratory organs and the main cause was classroom ventilation and dust. The most uncomfortable symptoms of child care teacher's mental health state was tension and the main cause was children's safety. Second, the mean scores of the variables were as follows : the mean score of health promoting lifestyle was 2.54. The highest sub factor of health promoting lifestyle was 'positive self recognition' and the lowest one was 'exercising'. The mean score of job stress was 2.80 and the highest sub factor was 'administration services'. They desire for a healthy life, but in reality, they are unsatisfied with their current health state and they are not able to practice certain actions actively to promote their health. Third, health promoting lifestyle was negatively correlated with job stress. The result of this study can be used as the basic data for reducing day care teacher's job stress, development of a program to promote day care teacher's health and improving day care teachers working environment.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.379-389
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• 2010

It is very important to determine a target probability of failure in reliability based design such as an allowable factor of safety in working stress design because they are indices to judge the stability of structures. We have carried out reliability analyses of nationwide gravity type quay walls and found that sliding and foundation failures of quay walls were dominant failure modes for every case of loads. And a target probability of failure for bearing capacity of foundation of quay wall was also determined in this study. Of several approaches which have been suggested until now, a couple of reasonable approaches were used. Firstly, in order to consider the safety margin of structures which have been executed so far, the reliability levels of existing structures were assessed. And then a mean probability of failure for the quay walls was estimated. In addition, life cycle cost(LCC) analyses for representative structures were performed. Probabilities of failure for several quay walls were calculated with changing the width of each quay wall section. LCC of quay wall which is requiring case by case during the service life was evaluated, and also the optimum probability of failure of quay wall which minimizes LCC was found. Finally, reasonable target probabilities of failure were suggested by comparing with mean probability of failure of existing structures.

• Safety and Health at Work
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• v.14 no.3
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• pp.332-339
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• 2023

Background: The aim of the study was to test the validity and reliability of the Perceived Future Decent Work Securement Scale for Turkish nursing students. Methods: A cross-sectional, methodological study design was used. The study was carried out at three nursing undergraduate programs in Turkey during the academic year of 2020-2021 with 336 senior nursing students. Language validity and content validity analyses were performed for the scale adaptation, followed by confirmatory factor analysis (CFA) for construct validity. The reliability of the scale was determined using the test-retest and Cronbach's alpha internal consistency coefficient. Results: The scale-content validity index score was 0.988. In CFA, all goodness-of-fit indices verified the acceptable fit of the model; its root mean square error of approximation was 0.076; the normed fit index was 0.909; the standardized mean square residual was 0.097; the relative fit index was 0.881; the goodness-of-fit index was 0.915; the adjusted goodness-of-fit index was 0.872 and χ²/df = 2.932. The overall reliability was α = 0.86. The item-total correlations of the scale were above the acceptable level, and the test-retest analysis had a high correlation. The access to healthcare (14.68, SD 3.53) obtained the highest average score, and the adequate compensation (8.52, SD 3.76) was the lowest rated by the senior nursing students. Conclusion: The Perceived Future Decent Work Securement Scale is a valid and reliable scale to assess nursing students' future decent work securement.

• Safety and Health at Work
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• v.9 no.3
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• pp.319-325
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• 2018

Background: Prolonged neck flexion during smartphone use is known as a factor of neck pain and alteration of neck muscle activity. Studies on the effects of shoulder taping on neck discomfort and neck muscle responses while texting on a smartphone are still lacking. The aim of this study was to examine the effects of shoulder taping on neck discomfort using a numerical rating scale, and neck muscle activity and fatigue using a surface electromyography during a texting task on a touchscreen smartphone. Methods: Twenty-five healthy adolescents used the dominant hand to perform a 30-minute texting task using a touchscreen smartphone at two separate times under one of the following two conditions: taping across the upper trapezius muscle and no taping. Neck discomfort, normalized root mean square, and normalized median frequency slopes for upper trapezius, cervical erector spinae, and sternocleidomastoid muscles were recorded. Results: The results revealed that shoulder taping provided significantly lower neck discomfort than no taping (p < 0.001). However, shoulder taping did not significantly alter normalized root mean square and normalized median frequency slope values of all muscles when compared with no taping controls. Conclusion: Shoulder taping reduces neck discomfort but does not affect neck muscle activity and fatigue while texting on a touchscreen smartphone.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.3
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• pp.469-485
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• 2018

On September 26, 2017, South Korean government has established the Particulate Matter Comprehensive Plan to improve Korean air quality by 2022, which aims to reduce annual mean surface $PM_{2.5}$ concentration to $18{\mu}g/m^3$. This study demonstrates quantitative assessment of predicted $PM_{2.5}$ concentrations over 17 South Korean regions with the enforcement of the comprehensive plan. We utilize the Community Multi-scale Air Quality (CMAQ) modeling system with CAPSS 2013 and CREATE 2015 emissions inventories. Simulations are conducted for 2015 with the base emissions and the planned emissions, and impacts from model biases are minimized using the RRF (Relative Response Factor). With effective emission reduction scenario suggested by the comprehensive plan, the model demonstrates that the surface $PM_{2.5}$ concentration may decrease by $6{\mu}g/m^3$ ($23{\mu}g/m^3{\rightarrow}17{\mu}g/m^3$) and $7{\mu}g/m^3$ ($25{\mu}g/m^3{\rightarrow}18{\mu}g/m^3$) for Seoul and South Korea, respectively. The number of high $PM_{2.5}$ days(daily mean>$25{\mu}g/m^3$) also decreases from 21 days to 4 days.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.50-57
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• 2010

Various installation faults may lie in fasteners in the construction of a direct-fixation track by the top-down method. At an extreme, they may cause excessive interaction between the train and track, compromise the running safety of the train, and cause damage to the track components. Therefore, the faults need to be kept within the allowable level through an investigation of their effects on the interactions between the train and track. In this study, the vertical dynamic stiffness of fasteners in installation faults was measured based on the dynamic stiffness test by means of an experimental apparatus that was devised to feasibly reproduce gap faults. This study proposes an effective analytical model for a train-track interaction system in which most elements, except the nonlinear wheel-rail contact and some components that behave bi-linearly, exhibit linear behavior. To investigate the effect of the behavior of fasteners in gap faults in a direct-fixation track on the vehicle and track, vehicle-track interaction analyses were carried out, targeting key review parameters such as the wheel load reduction factor, vertical rail displacement, rail bending stress, and mean stress of the elastomer. From the results, it was noted that the gap faults in the concrete bearing surface of a direct-fixation track need to be limited for the sake of the long-term durability of the elastomer than for the running safety of the train or the structural safety of the track.

• The Korean Journal of Food And Nutrition
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• v.21 no.1
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• pp.97-105
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• 2008

An IPA model was used to evaluate customer service encounters at a large food court; also the gaps between importance and performance from were also evaluated from both perspectives. The findings of this study will be applied in order to improve service quality at various large food service operations. A total of 298 customers from a large shopping mall food court completed the study questionnaire, asking them to evaluate the important and performance attributes of service. Seven underlying dimensions were identified and labeled by factor analysis: factor 1 was "safety": factor 2 "time": factor 3 "atmosphere": factor 4 "quality of food": factor 5 "menu attributes": factor 6 "comfort": and the last and seventh factor was "comprehension". As a result of IPA analysis the overall mean scores between the importance attributes and performance attributes showed significant differences by independent t-tests(p<0.001). Quadrant I was classified with unnecessary items including interior design, proper lighting, suitable chairs, and proper room temperature. In quadrant II thirteen variables showed high scores for both importance and performance, such as various menu choices, hygienic food, dishes, chairs, food court, kitchen, and employees; proper ventilation, employee kindness, waiting time to order, and received food; automatic system for ordering-serving. Quadrant III included eight variables identified as low priority, including appearance of food, nutrient content of food, proper portions, new menu, proper music, proper location of cashier, services for children and efficiency of movement. In quadrant IV six variables were included as areas to focus management's efforts, such as food taste, proper food temperature, use of safe food materials, maintenance of food quality, existence of preferred foods, and proper food prices. These results suggest that food court customers have interests that are distinct from restaurant customers and may need to be treated differently. It is anticipated that this data will be useful to the foodservice industry in order to segment customer characteristics by different dinning behaviors.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.9-17
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• 2015

In order to elucidate the current state of marine pollution of heavy metals around major shipyards in Korea, seawater samples were collected at eleven sampling stations and four control stations around 4 major shipyards located in the southeastern coast of Korea in summer 2010, and 6 kinds of metals such as copper(Cu), zinc(Zn), iron(Fe), cadmium(Cd), lead(Pb) and mercury(Hg) in seawater samples were analyzed. The analyses of heavy metals in seawater showed that the mean Cu concentrations in seawater around 4 major shipyards were in the range of $0.817{\sim}1.638{\mu}g/L$ which were lower than Korean environmental standards of $20{\mu}g/L$ for the protection of human health(PHH) and of $3{\mu}g/L$ for short-term protection of marine ecosystem(SPME) but higher than Cu concentration at control station by a factor of up to 2.75. The mean Zn concentrations were in the range of $0.228{\sim}0.567{\mu}g/L$ which were lower than Korean environmental standards of $100{\mu}g/L$ for PHH and $34{\mu}g/L$ for SPME but higher than Zn concentration at control station by a factor of up to 5.91. The mean Fe concentrations were in the range of $3.332{\sim}7.410{\mu}g/L$ which were higher than Fe concentration at control station by a factor of up to 6.75. The mean Cd concentrations were in the range of $0.013{\sim}0.028{\mu}g/L$ which were lower than Korean environmental standards of $10{\mu}g/L$ for PHH and $19{\mu}g/L$ for SPME but higher than Cd concentration at control station by a factor of up to 2.33. The mean Pb concentrations were in the range of $0.007{\sim}0.126{\mu}g/L$ which were lower than Korean environmental standards of $50{\mu}g/L$ for PHH and $7.6{\mu}g/L$ for SPME. The mean Hg concentrations were in the range of $0.002{\sim}0.004{\mu}g/L$ which were lower than Korean environmental standards of $0.5{\mu}g/L$ for PHH and $1.8{\mu}g/L$ for SPME. Although the concentrations of metals such as Cu, Zn and Fe which were used in shipbuilding works were lower than Korean environmental standards for PHH and SPME, the fact that the concentrations of Cu, Zn and Fe at sampling stations around major shipyards were higher than those at control stations implies that the works in shipyards had some effects on marine water quality around shipyards. Therefore, marine environment management such as the prevention and control of the discharge of various pollutants from shipyards is required on national level.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.149-156
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• 2017

Nuclear fuel requires high reliability and safety and therefore contains debris filtering devices to prevent failure-inducing debris from entering it. The debris filtering performance of nuclear fuel is one of the most important factors for fuel integrity. Therefore, the performance must be evaluated and the measurement must be reasonable. In this study, a calculation method of the comprehensive filtering efficiency using the weighted mean was proposed to establish a standard filtering efficiency index. To confirm the suitability of the proposed method, representative debris specimens were selected and the filtering efficiency with the weighted mean was compared with the efficiency of the arithmetic mean. The weighting factor of the weighted mean was introduced to produce a fair evaluation. In addition, the analysis of the debris filtering mechanism was performed according to the size of debris specimens, and the main dimensions of the filtering feature for commercial nuclear fuel.