• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.108-108
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• 2022

In this study, multispectral images of wheat according to soil water state were collected, compared, and analyzed to measure the physiological response of crops to environmental stress at the individual level. CMS-V multi-spectral camera(Silios Technologies) was used for image acquisition. The camera lens consists of eight spectral bands between 550nm and 830nm. Light Reflective information collected in each band sensor and stored in digital values, and it is converted into a reflectance for calculating the vegetation index and used. According to the camera manual, the NDVI(Normalized Difference vegetation index) value was calculated using 628 nm and 752 nm bands. Image measurement was conducted under natural light conditions, and reflectance standards(Labsphere) were captured with plants for reflectance calculation. The wheat variety used Gosomil, and the wheat grown in the field was transplanted into a pot after heading date and measured. Three treatments were performed so that the soil volumetric water content of the pot was 13~17%, 20~23%, and 25%, and the growth response of wheat according to each treatment was compared using the NDVI value. In the first measurement after port transplantation, the difference in NDVI value according to treatment was not significant, but in the subsequent measurement, the NDVI value of the treatment with a water content of 13 to 17% was lowest and was the highest at 20 to 23%. The NDVI values decreased compared to the first measurement in all treatment, and the decrease was the largest at 13-17% water content and the smallest at 20-23%. Although the difference in NDVI values could be confirmed, it would be difficult to directly relate it to the water stress of plants, and further research on the response of crops to environmental stress and the analysis of multi-spectral image will be needed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.159-160
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• 2002

To investigate the humidity effect on tribological behaviors of Si-DLC/DLC multi-layers, the samples were prepared using a system consisted of an ion-gun for deposition DLC films and a balanced magnetron sputter for introducing silicon atoms to Si-DLC films. The Si-DLC/DLC multi-layers were composed of pure DLC films and Si-incorporated DLC films alternatively and had different bilayer numbers. Hardness and residual stress were drastically decreased through the formation of Si-DLC/DLC multi-layers compared to those of the pure and Si-incorporated DLC films. Wear results obtained under the various humidity conditions (<10%, $40{\sim}50%$, and >85%) showed that the pure DLC film was largely depended on the humidity while the Si-DLC and the Si-DLC/DLC multi-layers were little affected by the environmental humidity. Although friction coefficients of all samples were increased with the relative humidity, the multi-layer films showed relatively lower friction coefficients that those of the single films.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.337-343
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• 2015

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.13-24
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• 2006

The stresses in concrete pavement systems are larger when vehicle loads are applied at pavement edges, and these large stresses significantly affect the behavior and performance of pavements. Therefore, in this study, the stress distribution and the critical stresses in concrete pavements were investigated using a finite element model when dual-wheel single-, tandem-, and tridem-axle loads were applied at pavement edges. First, the stress distribution along the longitudinal and transverse directions was analyzed, and then the effects of slab thickness, concrete elastic modulus, and foundation stiffness on the stress distribution were investigated. The effect of the tire contact pressure related to the tire print area was also studied. The location of the critical stress occurrence in concrete pavements was finally investigated. From this study, it was found that the critical concrete stress due to edge loads became larger as the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The effect of the tire contact pressure on the critical stress was clear as the slab thickness became smaller. The critical stress location in the transverse direction was independent of the concrete elastic modulus and the foundation stiffness; however, it moved into the interior as the slab thickness increased. The critical stress location in the longitudinal direction was under the axle for single- and tandem-axle loads, but for tridem-axle loads, it tended to move under the middle axle from the outer axles as the concrete elastic modulus and/or slab thickness increased and the foundation stiffness decreased.

• Korean Journal of Childcare and Education
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• v.14 no.6
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• pp.53-67
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• 2018

Objective: This study aimed to investigate the effect of parent- teacher communication on childcare teacher's job stress and turnover intention. This study also examined if the level of active stress coping used functions as a moderator in relationships among parent-teacher communication, childcare teacher's job stress, and their turnover intention. Methods: To achieve this, this study used data from 223 surveys from childcare teachers and analyzed the data with SEM and multi-group SEM analysis methods. Results: First, parent-childcare teacher communication influenced the teacher's turover intention through job stress. Second, the effect of parent-childcare teacher communication on job stress was not found in the higher-level of the active stress coping group. This was different from the significant effect in the lower-level of the active stress coping group. Also, parent-childcare teacher communication influenced teacher's turnover intention through job stress in the lower-level of the active stress coping group. In contrast, the mediation effect was not shown in the higher group. Conclusion/Implications: The results of this study show the effect of parent-childcare teacher communication on teacher's job stress and their turnover intention. Also, this study shows that the level of active stress coping could moderate the relationship among parent-childcare teacher communication, teacher's job stress, and their turnover intention.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.345-346
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• 2007

• Journal of Welding and Joining
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• v.30 no.6
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• pp.74-79
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• 2012

It depends on the joint configuration, dimensions and constraints of the joint whether the residual stress at the root of single-sided butt weld is tensile or not. Therefore, recommendation is generally made that high R ratio should be used in the fatigue test of welded joint in order to prevent excessively long life caused by compressive residual stress. In this research, the residual stress profile in butt weld joint was obtained through compliance method, using successive extension of a slot and measurement of the variation of strain during the slot extension. The residual stress profile was firstly assumed to be the linear summation of Legendre polynomials up to 9th order excluding 0th and 1st order. Strain variation on the surface was measured while the slot was being extended by cutting to find out the 8 unknown coefficients of each polynomial term. The cut was made by the electric discharge machine. It was concluded that the residual stress near the surface is positive valued, however, it turned into the negative value as soon as it passed through 2 or 3 mm of the depth.

• Korean Journal of Occupational Health Nursing
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• v.25 no.3
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• pp.227-237
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• 2016

Purpose: The purpose of this study was to identify the effects of nursing work environment and job stress on health problems of hospital nurses. Methods: The subjects were 200 nurses working in S general hospital in Gyeongnam, and the data were collected using organized questionnaire from Jan 10 to 25, 2015. The Korean version of the practice environment scale of nursing work index, the instrument for job stress, and the Korean version of Todie Health Index for health problem were used for measurement. The collected data were analyzed using descriptive statistics, t-test, ANOVA, Pearson's correlation, and multiple regression. Results: The nursing work environment was found to be slightly negative, and the job stress was found to be high. There were significant correlation among nursing work environment, job stress, and health problems. In addition, it showed that the nursing work environment and job stress of nurses were factors affecting their health problems. Conclusion: The nursing work environment and job stress are influencing factors on the health problems of hospital nurses. Multi-faceted efforts to create a positive nursing work environment are required. Further researches related to association between the nursing work environment and health problem of nurses are needed.

• Korean Journal of Occupational Health Nursing
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• v.16 no.2
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• pp.177-187
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• 2007

Purpose: We were to identify the differences of "Job stress" and "Depression scores" in the divided groups by self-efficacy. And the factors affecting Depression scores were analyzed. Method: This study was conducted from July 2006 to September 2006. Collected 295 surveys were used in this study among 311 surveys since 16 surveys offered insufficient data. SPSS for Windows 10.0 was used to analyse the data. Result: We identified the factors of "Occupational climate", "Job control", "Job demand" as affecting the depression scores in the lower self-efficacy group by the multi-variables statistical analysis. And this statistical model had 12.5% explainable power. Also, the factors of "Occupational climate" were identified as affecting the depression scores in the higher self-efficacy group. And the statistical model had 9.0% explainable power. Conclusion: In the lower self-efficacy group, the scores of the job stress and depression were significantly higher. Therefore, in the lower self-efficacy group, the self-efficacy promotion programs should be needed for prevention of the related occupational diseases. The factors related job stress were identified as affecting the depression scores in both lower and higher self-efficacy groups. Therefore, job stress management program should be prepared for stress loading workers.

• Journal of Korean Society for Quality Management
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• v.49 no.2
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• pp.183-200
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• 2021

Purpose: This study is to investigate the effects of job instability and job stress on the turnover intention of sports facility workers in the COVID-19 situation, considering the moderating effects of perceived organizational support. Methods: This study surveyed service workers working at public sports facilities in Seoul, Gyeonggi Province and North Chungcheong Province, South Korea. The multi-regression and hierarchical regression analysis were employed to analyze the collected data. Results: The results indicate that all of the factors constituting job instability (organizational, job, and personal factors) had a significant influence on the factors constituting job stress (job characteristic, roll-related, and human relationship factors), except for only the relationship between organizational factor and rol-related factor. Job characteristic and roll-related factors constituting job stress significantly affected turnover intention of sports facility workers. Also, it was found that the perceived organizational support moderated the relationship between job characteristic factors of job stress and turnover intention. Conclusion: Although the COVID-19 created an environment with very high job instability, the negative impacts of job instability and job stress can be minimized through consideration and support for service workers of the organization, reducing turnover intention.