• Korean Journal of Occupational Health Nursing
• /
• v.30 no.4
• /
• pp.145-155
• /
• 2021

Purpose: The purpose of this study was to examine the effects of customer violence experiences, protection systems, and monitoring systems on the subjective health status of salespersons and electronic machine repairers. Methods: A total of 934 persons were sampled nationwide, including 582 salespersons and 352 electronic machine repairers, from March 2~30, 2020 and asked to fill out a self-reported questionnaire. Results: The findings show that electronic machine repairers were more exposed to customer violence and had a weaker protection system than salespersons. They also experienced severe control from management through a monitoring system. The regression analysis revealed that verbal violence had a negative impact on the subjective health status of electronic machine repairers (p=.021). A worker protection system had significant effects on the improved subjective health status of salespersons (p=.009). Depression and fatigue had negative impacts on the subjective health status of both salespersons (depression: p<.001, fatigue: p<.001) and electronic machine repairers (depression: p<.001, fatigue: p=.002). Conclusion: These findings put a greater emphasis on the need for worker protection systems to prevent workplace violence and a health promotion program to manage depression and fatigue in workplaces.

• Smart Structures and Systems
• /
• v.29 no.1
• /
• pp.207-220
• /
• 2022

Structural health monitoring (SHM) plays a vital role in the maintenance and operation of constructions. In recent years, autonomous inspection has received considerable attention because conventional monitoring methods are inefficient and expensive to some extent. To develop autonomous inspection, a potential approach of crack identification is needed to locate defects. Therefore, this study exploits two deep learning-based segmentation models, DeepLabv3+ and Mask R-CNN, for crack segmentation because these two segmentation models can outperform other similar models on public datasets. Additionally, impacts of label quality on model performance are explored to obtain an empirical guideline on the preparation of image datasets. The influence of image cropping and label refining are also investigated, and different strategies are applied to the dataset, resulting in six alternated datasets. By conducting experiments with these datasets, the highest mean Intersection-over-Union (mIoU), 75%, is achieved by Mask R-CNN. The rise in the percentage of annotations by image cropping improves model performance while the label refining has opposite effects on the two models. As the label refining results in fewer error annotations of cracks, this modification enhances the performance of DeepLabv3+. Instead, the performance of Mask R-CNN decreases because fragmented annotations may mistake an instance as multiple instances. To sum up, both DeepLabv3+ and Mask R-CNN are capable of crack identification, and an empirical guideline on the data preparation is presented to strengthen identification successfulness via image cropping and label refining.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.10a
• /
• pp.161-164
• /
• 2002

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Tensile test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. EFPI was less sensible to the damage signals compared with the optical fiber vibration sensor. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.370-375
• /
• 2003

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Tensile and indentation test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.04a
• /
• pp.42-45
• /
• 2003

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Indentation test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Journal of Yeungnam Medical Science
• /
• v.38 no.4
• /
• pp.275-281
• /
• 2021

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by abnormalities in social communication/interaction and restrictive, repetitive patterns of behavior. ASD is a relatively common psychiatric disorder, with a prevalence of approximately 1.7% in children. Although many children and adolescents with ASD visit the hospital for medical help for emotional and behavioral problems such as mood instability and self-harming behavior, there are also many visits for sleep disturbances such as insomnia and sleep resistance. Sleep disturbances are likely to increase fatigue and daytime sleepiness, impaired concentration, negatively impact on daytime functioning, and pose challenges in controlling anger and aggressive behavior. Sleep disturbance in children and adolescents with ASD negatively affects the quality of life, nothing to say the quality of life of their families and school members. In this review, sleep disturbances that are common in children and adolescents with ASD and adolescents are presented. The developmental and behavioral impacts of sleep disturbances in ASD were also considered. Finally, non-pharmacological and pharmacological treatments for sleep disturbances in children and adolescents with ASD and adolescents are reviewed.

• Journal of Aerospace System Engineering
• /
• v.11 no.1
• /
• pp.1-7
• /
• 2017

While a satellite is carried into orbit by a launch vehicle, it is exposed to the severe launch environment with random vibrations and shock. Accordingly, these vibration sources affect electronic equipment, particularly the printed circuit board (PCB) in the satellite. When the launch load impacts the PCB, it causes negative behavior. This causes perpendicular bending around the boundary of fixation points that finally leads to the failure of solder joints, lead wires, and PCB cracks. To overcome these issues, the electronic equipment design must meet reliability requirements. In this paper, Steinberg's method is used to derive allowable and maximum deflection to verify design from a life perspective concerning the control board of the Antenna Pointing Driver (APD) mounted on KOMPSAT-3.

• Journal of the Korean Society for Precision Engineering
• /
• v.34 no.2
• /
• pp.151-156
• /
• 2017

Shot peening is widely used to improve the fatigue life and strength of various mechanical parts and an accurate method is important for the prediction of the compressive residual stress caused by this process. A finite element (FE) model with an elliptical multi-shot is suggested for random-angled impacts. Solutions for compressive residual stress using this model and a normal random vertical-impact one with a spherical multi-shot are obtained and compared. The elliptical multi-shot experimental solution is closer to an X-ray diffraction (XRD) than the spherical one. The FE model's peening coverage also almost reaches the experimental one. The effectiveness of the model based on an elliptical shot ball is confirmed by these results and it can be used instead of previous FE models to evaluate the compressive residual stress produced on the surface of metal by shot peening in various industries.

• Journal of the Ergonomics Society of Korea
• /
• v.26 no.2
• /
• pp.21-33
• /
• 2007

The study investigates the effects of luminance contrast, which is the contrast between text color and background color, on readability in VDT environments. Our research goals are to prove that the relationship between luminance contrast and readability is not linear and to explore the best luminance contrast level for optimal readability. We conducted two pretests before the main experiment to determine the operational readability and luminance contrast levels. We also conducted a controlled main experiment, in which luminance contrast, reading amount and screen size were tested in terms of its relation with readability. The results of the main experiment indicate that the readability has a non-linear relation with luminance contrast, and the optimal readability is obtained when the contrast is equal to 0.951. Furthermore, the non-linear function and optional point stay constant regardless of screen size and reading amount. The paper ends with implications of the results that maximal contrast does not always mean the optimal readability.

• The Bulletin of The Korean Astronomical Society
• /
• v.45 no.1
• /
• pp.46.2-46.2
• /
• 2020

Dust ejection activities have been discovered from a few tens of asteroids since the first confirmation in 2006. Those objects are known as active asteroids. They provide good observational chances to study ongoing phenomena in the solar system such as sublimation of icy volatiles, mutual collisions among asteroids, rotational disintegrations, thermal fatigue, etc. Although dust ejection mechanisms of individual cases have been investigated through observations, the frequencies of the events and their connection to the overall evolutionary budget of the solar system have not yet been studied thoroughly, mainly because previous studies were based on serendipitous discoveries without any systematic surveys of these objects. In this work, we made wide-field monitoring observations of asteroids using Korea Microlensing Telescope Network (KMTNet) during the 2018/2019 winter season. Among 3,644 asteroids in the field-of-view, we detected nine candidates of brightness enhancements which we suspect as possible activities. It is still possible that some of those brightness increases have caused by long-term rotations. However, our observed frequency and brightness enhancements size-frequency distribution agrees with the expectations from impacts with decimeter sized objects, when the main belt objects size-frequency distribution observed down to decameter sized bodies are extrapolated to decimeter size.