• Korean Journal of Occupational Health Nursing
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• v.19 no.2
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• pp.223-235
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• 2010

Purpose: This study was done to investigate the prevalence of job stress and musculoskeletal symptoms, and to identify the factors that affect work-related musculoskeletal symptoms of the 119 Emergency medical technicians (EMT). Method: From August 26 to September 10, 2010, the data were obtained from 456 EMT working in Daejeon city or Choongnam province. For data analysis, descriptive statistics and multiple logistic regression were performed using SAS version 9.1. Results: Physical environment, job demand, interpersonal conflict, and occupational climate were stressful to 119 EMT. The prevalence of musculoskeletal symptoms of female EMT was higher than those of the male EMT's. After gender and age were adjusted, there ware significant relationships between musculoskeletal symptoms and some risk factors including occupational class, hours of intensive musculoskeletal use, previous injury or work-related injury, physical burden, and job stress. Overall, a higher degree of job stress increased musculoskeletal symptoms. Conclusion: Job stress is a major cause of musculoskeletal symptoms. To prevent and manage musculoskeletal disease of 119 EMT, there is a need to develop a management program for musculoskeletal symptoms to reduce occupational stress, considering gender differences.

• Journal of the Korean Society of Safety
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• v.26 no.3
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• pp.83-90
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• 2011

It is well known that urgency resulted from time stress can be a great cause to industrial accidents. Therefore, time stress has been studied in the aspect of macroscopic view, namely industrial safety management, but has not been studied in microscopic view such as psychophysiological approach. Among diverse psychophysiological indices, Electroencephalogram(EEG) would be on of the most objective psychophysiological research technique on human errors though few research has been taken yet. This study aimed to get characteristics of human error while committing a simple arithmetic addition task by utilizing the power spectrum technique of EEG data. Each experiment was composed of 2 tasks under different condition - with and without time stress. As subjects, 5 young undergraduate students in their early twenties participated in this study. The results advocated a well-known fact that time stress downgrades the performance of human workers. However, correct answer rate and response time were not significantly influenced by time stress factor which might be explained by the constructural factor adopted in the present study. As in the previous studies, among various EEG-related measures, relative band power ratios of ${\alpha}$ and ${\beta}$ waves to sum of ${\alpha}$,${\beta}$,${\theta}$ wave powers, namely $P_{{\alpha}/({\alpha}+{\beta}+{\theta})}$ and $P_{{\beta}/({\alpha}+{\beta}+{\theta})}$ seemed to be the most effective measures to grasp variation of brain activities in time-stressed situation so that discussions were expanded about their variations.

• Journal of Korean Society for Quality Management
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• v.23 no.1
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• pp.50-63
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• 1995

We study under what condition the probability of the failure state of each component is realized by the latent stress model which considers the cause of the failure as well as the state of the given system. As a result, when the number of the components is less than or equal to 3, the $MTP_2$ property is a necessary and sufficient condition for the realization of the probability of system state by the latent stress model. Moreover, if the probability of the system state involving 2 or 3 components satisfies the $MTP_2$ property, one could guess that each component is under the same stress.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.235-245
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• 2018

The purpose of this study was to determine the gender differences in affecting factors of perceived stress level. The present study analyzed 2011 data of the Korea Community Health Survey and a total of 229,226 participants was included. To investigate the affecting factors of perceived stress, multiple logistic regression analyses were conducted. There were gender differences in affecting factors of perceived stress by education level, number of family members, household income, and self-care. This suggests that gender differences may exists between perceived stress level and health related quality of life. Further studies are necessary to investigate whether the cause of the gender differences in stress perception.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.2
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• pp.97-101
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• 2017

Fruits are subjected to a variety of vibration stress during the transportation from a production area to markets. Vibration inputs are transmitted from the transporting vehicle through the packaged fruit. And the steady state vibration input may cause serious internal damage of fruit. Product quality of fruits declines by various factors while they are stored right after harvesting and among the substance in charge of post ripening action, ethylene ($C_2H_4$) biosynthesis increases fruits' respiration process after harvesting and decreases storage expectancy. Ethylene production of apples rapidly increases while storage duration becomes longer. This tendency is much clearer for the apples with vibration stress at input acceleration level. When there was no vibration stress, change in ethylene production level of apples are not very large during storage. Ethylene production rates inside the gas collecting container increased significantly ($p{\leq}0.05$) after 24 hours storage, particularly for apples with vibration stress ($0.7{\mu}l/kg{\cdot}hr$ (1st stack), $0.78{\mu}l/kg{\cdot}hr$ (2nd stack), $0.96{\mu}l/kg{\cdot}hr$ (3rd stack)); whereas less ethylene was produced in control apples ($0.18{\mu}l/kg{\cdot}hr$ during storage. Also ethylene production rates of apples according to the stack position were significantly different ($p{\leq}0.05$). The vibration stress clearly accelerated the degradation of apple quality during storage, resulting in increased ethylene production.

• Corrosion Science and Technology
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• v.13 no.3
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• pp.102-106
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• 2014

Nickel electrodeposition from sulfamate bath has several benefits such as low internal stress, high current density and good ductility. In nickel deposited layers, sulfur induces high temperature embrittlement, as Ni-S compound has a low melting temperature. To overcome high temperature embrittlement problem, adding manganese is one of the good methods. Manganese makes Mn-S compound having a high melting temperature above $1500^{\circ}C$. In this work, the mechanical properties of Ni-Mn deposited layers were investigated by using various process variables such as concentration of Mn$(NH_2SO_3)_2$, current density, and bath temperature. As the Mn content of electrodeposited layers was increased, internal stress and hardness were increased. By increasing current density, internal stress increased, but hardness decreased. With increasing the bath temperature from 55 to $70^{\circ}C$, internal stress of Ni deposit layers decreased, but hardness didn't change by bath temperature. It was likely that eutectoid manganese led to lattice deformation, and the lattice deformation increased hardness and internal stress in Ni-Mn layers. Increasing current density and decreasing bath temperature would increase a mount of $H_2$ absorption, which was a cause for the rise of internal stress.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.842-846
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• 2005

A brake disk and a pad are important parts that affect the braking stability of a railway vehicle. Especially, because a brake disk stops the vehicle using conversion of the kinetic energy to frictional energy, thermal fatigue cracks are generated by the cyclic thermal load, as frictional heat, on a frictional surface and these cracks cause the fracture of a brake disk. Therefore, many researches for the thermal stress must be performed to improve the efficiency of brake disk and ensure the braking stability. In this study, we performed the thermal stress analysis for a ventilated brake disk with 3-D analysis model. For that, we simplified the shape of a ventilated hole to minimize problems that could be occurred in analysis process. Thermal stress analysis was performed in case that pressure distributions on a frictional surface is constant and is not. To determine pressure distributions of irregular case, pressure distribution analysis for a frictional surface was carried out. Finally using the results that were obtained through pressure distribution analysis, we carried out thermal stress analysis of each case and investigated the results of thermal stress analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.651-652
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• 2006

The choice of suitable hip implant is one of important factors in total hip replacement (THR). In clinical view points, improper adaptation of hip implant might cause abnormal stress distribution to the bone, which can shorten the lifespan of replaced hip implant. Currently, interest in custom-designed hip implants has increased as studies reveals the importance of geometric shape of patient's femur in modeling and designing custom hip implants. In this study, we have developed the custom-designed hip implant models with various sizes in hip implant, and the stress distribution in the bone was analyzed using Finite Elements methods. It was found that minimizing the gap between implant stem and femoral cavity is crucial to minimize stress concentration in the bone.

• Geomechanics and Engineering
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• v.23 no.6
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• pp.587-600
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• 2020

Shear-induced instability of jointed rock mass has greatly threatened the safety of underground openings. To better understand the failure mechanism of surrounding rock mass under shear, the flawed specimens containing a circular opening and two open joints are prepared and used to conduct direct shear tests. Both experimental and numerical results show that joint inclination (β) has a significant effect on the shear strength, dilation, cracking behavior and stress distribution around flaws. The maximum shear strength, occurring at β=30°, usually corresponds to a unifrom stress state around joint and an intense energy release. However, a larger joint inclination, such as β=90°~150°, will cause a more uneven stress distribution and a stronger stress concentration, thus a lower shear strength. The stress distribution around opening changes little with joint inclination, while the magnitude varys much. Both compression and tension around opening will be greatly enhanced by the 30°-joints. In addition, a higher normal stress tends to enhance the compression and suppress the tension around flaws, resulting in an earlier generation and a larger proportion of shear cracks.

• CELLMED
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• v.2 no.1
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• pp.2.1-2.11
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• 2012

Tea polyphenols especially catechins have long been studied for their antioxidant and radical scavenging properties. Scientists throughout the world have investigated the usefulness of the regular green tea consumption in several disease conditions. In-vitro and in-vivo experiments on catechins especially epigallocatechingallate have revealed a significant role in many ways. Reactive oxygen species have been increasingly implicated in the pathogenesis of many diseases and important biological processes. Toxic effects of these oxidants, commonly referred to as oxidative stress, can cause cellular damage by oxidizing nucleic acids, proteins, and membrane lipids. Oxidative stress has been related to aging and age related disorders. It is found that in a wide variety of pathological processes, including cancer, atherosclerosis, neurological degeneration, Alzheimer's disease, ageing and autoimmune disorders, oxidative stress has its implications. Catechins have been reported to be useful in combating aging and age related disorders like cancer, cardiovascular disorders and neurodegenerative diseases. In this mini review we will discuss such studies done across the globe.