• Transactions of Materials Processing
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• v.13 no.7
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• pp.600-607
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• 2004

This paper addresses a viscoplastic constitutive model that allows a consistent way of modeling positive and negative rate sensitivities of flow stress concerned with dynamic strain aging. Based on the concept of continuum mechanics, a phenomenological constitutive model includes the use of a yield surface within the framework of unified viscoplasticity theory. To model negative rate sensitivity, rate-dependent back stress is introduced and flow stress in fully developed inelastic deformation regime is thus decomposed into the plastic contribution of rate independency and the viscous one of rate dependency.

• Structural Engineering and Mechanics
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• v.50 no.1
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• pp.89-103
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• 2014

According to experimental studies made so far, design formula of shear characteristics suggested by ISO 22762 and JEAG 4614, representative design code for Lead Rubber Bearing(LRB) shows dependence caused by changes in compressive stress. Especially, in the case of atypical special structure, such as a nuclear power structure, placement of seismic isolation bearing is more limited compared to that of existing structures and design compressive stress is various in sizes. As a result, there is a difference between design factor and real behavior with regards to shear characteristics of base isolation device, depending on compressive stress. In this study, a full-scale low hardness device of LRB, representative base isolation device was manufactured, analyzed, and then evaluated through an experiment on shear characteristics related to various compressive stresses. With design compressive stress of the full-scale LRB (13MPa) being a basis, changes in shear characteristics were analyzed for compressive stress of 5 MPa, 10 MPa, 13 MPa, 15 MPa, and 20 MPa based on characteristics test specified by ISO 22762:2010 and based on the test result, a regression analysis was made to offer an empirical formula. With application of proposed design formula which reflected the existing design formula and empirical formula, trend of horizontal characteristics was analyzed.

• Journal of Korean Academy of Nursing
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• v.33 no.6
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• pp.713-721
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• 2003

Purpose: This study was to determine the mediator or moderator role of social support in the relationship between stress and depression among family caregivers of older adults with dementia. Method: Sixty nine family caregivers were randomly selected from health care centers in P city and a face-to-face interview was conducted using questionnaires from January to May of 2002. Data were analyzed with descriptive statistics, Pearson correlation, and hierarchical multiple regression using SPSS program. Result: Family caregivers of older adults with higher dependency in ADLs and higher problematic behaviors, provided care to the older adults for a longer period of time, and perceived less social support reported higher depression. Social support showed mediating effects between stress and depression, while did not show moderating effects. Elderly dependency on ADLs and caregiving duration decreased perceived social support and decreased social support increased depression. Conclusion: To increase family and social support to the caregivers of more functionally impaired elderly, family education to increase emotional support and physical assistance to the caregivers and broader and flexible application of social support such as increasing accessibility to the elderly daycare service with lower price may prove beneficial.

• Coupled systems mechanics
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• v.11 no.2
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• pp.93-106
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• 2022

The total embankment settlement consists of three stages: the initial settlement, the primary consolidation settlement, and the secondary consolidation settlement. The total embankment settlement is largely controlled by the primary consolidation settlement, which is usually computed with numerical models that implement Biot's theory of consolidation. The key parameter that affects the primary consolidation time is the coefficient of permeability. Due to the complex stress and strain states in the foundation soil under the embankment, to be able to predict the consolidation time more precisely, aside from porosity-dependency, the strain-dependency of the coefficient of permeability should be also taken into account in numerical analyses. In this paper, we propose a two-dimensional plane strain numerical model of embankment primary consolidation, which implements Biot's theory of consolidation with both porosity-dependent and strain-dependent coefficient of permeability. We perform several numerical simulations. First, we demonstrate the influence of the strain-dependent coefficient of permeability on the computed results. Next, we validate our numerical model by comparing computed results against in-situ measurements for two road embankments: one near the city of Saga, and the other near the city of Boston. Finally, we give our concluding remarks.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.383-391
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• 2013

A number of true triaxial tests on rock samples have been conducted since the late 1960 and their results strongly suggest that the intermediate principal stress has a considerable effect on rock strength. Based on these experimental evidence, various 3-D rock failure criteria accounting for the effect of the intermediate principal stress have been proposed. Most of the 3-D failure criteria, however, are focused on the phenomenological description of the rock strength from the true triaxial tests, so that the associated strength parameters have little physical meaning. In order to confirm the likelihood that the intermediate principal stress dependency of rock strength is related to the presence of weak planes and their distribution to the preferred orientation, true triaxial tests are simulated with the transversely isotropic rock model. The conventional Mohr-Coulomb criterion is extended to its anisotropic version by incorporating the concept of microstructure tensor. With the anisotropic Mohr-Coulomb criterion, the critical plane approach is applied to calculate the strength of the transversely isotropic rock model and the orientation of the fracture plane. This investigation hints that the spatial distribution of microstructural planes with respect to the principal stress triad is closely related to the intermediate principal stress dependency of rock strength.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.10a
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• pp.51-52
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• 2012

Safety at sea continues to be an important topic for research. The factors that contribute to safety issues are often complex and unclear. Lack of non-technical skills in such areas as communication, teamworking, situational awareness, decision making etc. are well documented as directly affecting safety in high risk work settings such as on board merchant vessels. Competence in non-technical skills can be affected by various habits and circumstances that influence a worker and result in either positive thinking and behaviour or negative thinking and behaviour. Negative thinking can cause stress, anger, frustration; loneliness etc. and this can possibly result in behaviour or actions that undermine the safety of crew and ship. Factors that may contribute to these negative thoughts and behaviours are many and varied and this paper will be looking at one aspect: mobile phone use. In the Republic of Korea, dependency on mobile phones is uniquely high. Maritime students are also susceptible to such dependency and this paper will demonstrate that the symptoms associated with mobile phone addiction and dependency, and in particular the symptoms of withdrawal, are important factors that need to be mitigated in order to improve safety at sea. Although the benefits of mobile phones are many it will be suggested that over-reliance, dependency or addiction can result in negative thinking or behaviour that may directly or indirectly contribute to the factors that cause incidents and accidents at sea. It will be suggested that the most appropriate method of dealing with this problem is twofold: firstly, through training at the educational level and secondly, by encouraging the shipping industry and government to invest more into providing seafarers with better access to the communication methods that they are used to on shore in order to improve work conditions.

• Journal of the Korean Home Economics Association
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• v.28 no.4
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• pp.119-133
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• 1990

This study attempts to expore factors which influence of stress. Date were obtained from structed interview conducted with 373 men and women who were 60 years over and living in Kyungnam. Data were analyzed through X2, ANOVA, T-TEST, FACTOR ANALYSIS, MULTIPLE REGRESSTION techniques. The results are summarized as follow: 1. Stress of old age were showed over middle level. The domains of stress showed that health problem is first, later life problem is second, trouble of communication is third, dependency problem is fourth, alienation is last(p<.001). 2. Of the variables health status, family type, economic status, self-esteem, mastery were significant with stress(p<.001). 3. Of the variables sex, religious, self-esteem, mastery were significant of used method in coping with stress. 4. The most of effective variables of stress were mastery, health status, self-esteem.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.219-230
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• 2018

This study was conducted to identify factors influencing depression symptoms among college students. To accomplish this, a self-administered questionnaire was distributed to 546 college students from October 1st to November 30th, 2015. Univariate analysis, logistic regression, and multivariate regression analysis between variables were then conducted using depression symptoms as the dependent variable and other relevant factors as independent variables. The level of depression among the subjects differed significantly according to personal attributes, family life and school life characteristics, as well as health related behavioral characteristics. The risk of depression was significantly higher in the lower group than the higher group of family and friends social support, the lower group than the higher group of self-esteem, the lower group than the higher group of locus of control, and in the high risk stress group than the normal stress group. Factors influencing depression symptoms included religion, social support from family, social support from friends, interpersonal dependency, locus of control, and stress were identified as significant variables, indicating that depression among college students is related to diverse elements including sociodemographic characteristics, social support from family/friends, interpersonal dependency, locus of control, and stress. Depression symptoms significantly increased when social support from family or friends, low psychological behavior characteristics are low, and when stress is high. Thus, it is necessary to understand factors related to depression and reduce them to decrease depression levels of college students.

• Journal of the Korean Home Economics Association
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• v.39 no.9
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• pp.63-78
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• 2001

The purpose of this study is to compare how different the belief, social support, stress, coping and motivation between the Korean and American children. The data was collected from 157 Korean and 114 American students (5·8th grade). The resets were as follows: 1. Korean children's other dependency and pessimism level was significantly higher than those of American children. Also Korean children perceived higher than American children in the control-pressure stress and elf-respect stress. 2. Pessimism was observed the highest effect factor on Korean children's stress. 3. Korean students tried various coping under the relationship stress. 4. Problem oriented coping was found as an effective coping in Korean children. But the pursuit of support was found as an effective coping in American children.

• International Journal of Reliability and Applications
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• v.17 no.1
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• pp.21-49
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• 2016

Many mechanical, electrical and electronic products have more than one performance characteristics (PCs). For example the performance degradation of rubidium discharge lamps can be characterized by the rubidium consumption or the decreasing intensity the lamp. The product may degrade due to all the PCs which may be independent or dependent. This paper deals with the design of optimal bivariate step-stress partially accelerated degradation test (PADT) with degradation paths modelled by gamma process. The dependency between PCs has been modelled through Frank copula function. In partial step-stress loading, the unit is tested at usual stress for some time, and then the stress is accelerated. This helps in preventing over-stressing of the test specimens. Failure occurs when the performance characteristic crosses the critical value the first time. Under the constraint of total experimental cost, the optimal test duration and the optimal number of inspections at each intermediate stress level are obtained using variance optimality criterion.