• Journal of Korean Biological Nursing Science
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• v.25 no.2
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• pp.123-130
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• 2023

Purpose: Sitting time, smoking, and perceived stress strongly influence physical health independent of physical activity. However, the associations among perceived stress, sedentary behavior, and smoking are poorly understood. Therefore, we examined the relationships between sitting time, smoking, and perceived stress in Korean adults aged < 65 years. Methods: We analyzed data from the seventh National Health and Nutrition Survey. In this cross-sectional study, data from 6,890 Korean adults aged < 65 years were analyzed. Complex-sample logistic regression was used to examine the relationships between sitting time, smoking, and perceived stress. Results: The group with a high sitting time (≥ 8 h/day) and those who smoked had significantly higher odds of experiencing stress than the low sitting time (< 8 h/ day) and non-smoking groups (odds ratio: 1.88, 95% confidence interval: 1.42-2.50). Conclusion: Perceived stress was positively correlated with current smoking status and increased sitting time. High sitting time (≥ 8 h/day) and current smoking were associated with a higher risk of perceived stress in Korean adults aged < 65 years.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.143-150
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• 2003

This study deals with the stress-strain-strain rate behaviour of overconsolidated clay. Consolidated-drained stress path tests were performed on the stress-time dependent condition. Stress history consists of rotation angle of stress path, overconsolidation ratio, and magnitude of length of recent stress path. Time history includes loading rate of recent and current stress path. Test results show that all influence factors have an increasing strain rate with time, and the strain rate varies with the change of the rotation angle of stress path. With the increase of overconsolidation ratio and loading rate of current stress path, the strain rate also increases. For the stress history, correlation between stress-strain and strain rate is indicated but the time history is not.

• International Journal of Reliability and Applications
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• v.15 no.2
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• pp.125-150
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• 2014

Accelerated life tests (ALTs) are extensively used to determine the reliability of a product in a short period of time. Test units are subject to elevated stresses which yield quick failures. ALT can be carried out using constant-stress, step-stress, progressive-stress, cyclic-stress or random-stress loading and their various combinations. An ALT with linearly increasing stress is ramp-stress test. Much of the previous work on planning ALTs has focused on constant-stress, step-stress, ramp-stress schemes and their various combinations where the stress is generally increased. This paper presents an optimal design of ramp soak-stress ALT model which is based on the principle of Thermal cycling. Thermal cycling involves applying high and low temperatures repeatedly over time. The optimal plan consists in finding out relevant experimental variables, namely, stress rates and stress rate change points, by minimizing variance of reliability function with pre-specified mission time under normal operating conditions. The Burr type XII life distribution and time-censored data have been used for the purpose. Burr type XII life distribution has been found appropriate for accelerated life testing experiments. The method developed has been explained using a numerical example and sensitivity analysis carried out.

• Journal of Families and Better Life
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• v.14 no.2
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• pp.127-138
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• 1996

The purpose of this study is to show farm women's stress under productive activity role multiple overload through family characteristic (pattern and number) and characteristic(type working time and involvement proportion) of productive activity. The outline of the study is as follow; 1. Stress by pattern and number of a family is highest in a four generation family and increases according as the number of the family increases. 2. The characteristic of productive activity : 1) Stress based on type of productive activity is highest in Type III of the most multiple overload roles. 2) in light of stress based working time area of household task activity is in inverse proportion to working time but area of farming and wage earning activity are approximately in direct proportion to it. The two-way ANOVA analysis show that stress in Type I of area of household task increases but in Type IV it decreases as working time increases 3) In stress based on involvement proportion to it. The wo-way ANOVA analysis show that stress in Type I of area of household task increases but in Type IV it decreases as working time increases. 3) In stress based on involvement proportion in three as working time increases 3). In stress based on involvement proportion in three activity areas the more the involvement proportion the less of the stress : an inverse ratio.

• Journal of the Korean Society of Food Culture
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• v.24 no.6
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• pp.728-738
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• 2009

The purpose of this study was to evaluate job stress factors of school food service nutritionists according to the number of years they have worked. The subjects of this survey included 125 nutritionists (69 from full-time employees and 56 from part-time nutritionists) from elementary school, middle school, and high school in the Gangwon area. The results showed that stress related to duty was the top job stress factor, followed by environment-related stress, personal stress, organization-related stress and stress caused by human relations. In terms of the degree of stress, part-time nutritionists have more stress compared to full-time nutritionists. This was especially true for nutritionists that had been employed for one year. In this case, the degree of stress was much higher than long time employed nutritionists. In terms of how to deal with job stress, school nutritionists eliminated stress directly (with direct countermeasures). In order to deal with stress, workers expected stable employment such as pay (wages), promotions, etc. In particular, part-time school nutritionists had stronger expectations. When correlation between job stress factors were examined, environment-related, duty-related, organization-related, human relations-related and personal stress were all shown to be mutually related.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.317-323
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• 2017

This work presents a new strategy to model stress dependent relaxation process in large deformation. The strategy is relied on the fact that in some particular soft materials undergoing large deformation, e.g., elastomers, rubbers and soft tissues, the relaxation time depends strongly on stress levels. To simplify the viscoelastic model, we consider that the relaxation time is the function of previous elastic deviatoric stress state experienced by materials during loading. Using the General Maxwell Model (GMM), we simulate numerically conditions with the constant and the stress dependent relaxation time for uniaxial tension and compression loading. Hence, it can be shown that the proposed model herein not only can represent different relaxation time for different stress level but also maintain the capability of the GMM to model hysteresis phenomena.

• Journal of Biosystems Engineering
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• v.14 no.1
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• pp.8-15
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• 1989

Agricultural materials do not react in a purely elastic manner, and their responses when subjected to stress and strain are appeared from a combination of elastic and viscous behavior. Various researchers have studied the mechanical and rheological properties of the many agricultural materials, but those properties are available mostly foreign varieties of agricultural products. Rheological properties of rice seedlings become important to formulate the principles governing their mechanical behavior. The objectives of this study were to experimentally determine the stress relaxation properties of rice seedlings such as three Japonica-type and one Indica ${\times}$ Japonica hybrid in the transplanting age. The results of this study are summarized as follows; 1. The stress relaxation behavior could be described by the generalized Maxwell model. 2. The phenomenon of stress relaxation happened abruptly just after loading and this phenomenon weakened with the loading time lapsed. 3. With increase of the initial stress, the stress relaxation intensity and residual stress increased, while the relaxation time was constant with increased, while the relaxation time was constant with increase of the level of initial stress. 4. With increase of loading rate, the stress relaxation intensity increased, while the relaxation time and residual stress decreased.

• 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 of Coastal and Ocean Engineers
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• v.14 no.4
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• pp.286-294
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• 2002

This study investigated the effects of stress and time history of overconsolidated clayey soils on pore pressure parameter, A. Laboratory tests were carried out under the conditions of both varying stress and time history. The stress history is classified into (i) rotation angle of stress path, (ii) overconsolidation ratio, and (iii) magnitude of length of recent stress path. The time history is divided into (i) loading rate of recent stress path and (ii) rest time. Pore pressure parameters are different both in the magnitude and trend with the rotation angle, depending on the magnitude of overconsolidation ratio but not in a trend. In addition, the pore pressure parameters have no effects on the magnitude of length of recent stress path except the level of initially small strain, while loading rates of recent stress path have effects on it. Finally, the pore pressure parameters of overconsolidated clays increase with the existence of the rest time, until either the deviator stress exceeds 70 kPa or the strain up to 0.1%.

• Journal of Family Resource Management and Policy Review
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• v.18 no.2
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• pp.103-119
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• 2014

This study focuses on the relationship between time management behavior and parenting stress of mothers with developmentally disabled children. The participants of this study were 162 mothers whose children have developmental disabilities and attend pre-school and social welfare centers for early education. This study investigates the time management behaviors of the participants, and whether these behaviors have an effect on their time management satisfaction and parenting stress. The findings were as follows: 1) The time management behaviors of the participants were lower than average, scoring 2.87 out of 5. The order of dimensional scores from highest to lowest were sequencing, planning, recording habits, evaluating, and setting goals. 2) Time management satisfaction and parenting stress for the participants exhibited a negative correlation. 3) Adaptation behaviors of the children and time management behaviors of the mothers were factors that had significant effects on the mothers' parenting stress. These results showed the importance of time management for mothers with developmentally disabled children.