• Proceedings of the KSR Conference
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• 2005.05a
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• pp.385-390
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• 2005

A specimen with residual stress due to welding was analyzed by three-dimensional cohesive zone model. The residual stress distribution was calculated by simulating welding process, and cohesive elements were located along crack propagation planes. Crack growth is possible since two planes of the cohesive element are separated beyond a maximum load carrying capacity. Stress fields around a crack tip are compared for specimens with and without residual stresses. Load-displacement curves and crack growth behaviors are also examined.

• Journal of the KSME
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• v.16 no.2
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• pp.100-107
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• 1976

Stress analysis of tapered cylinder of reactor vessels is investigated by means of the intersection method. The tapered cylinder is approximated into three models-average cylinder, conical frustum, and ring. The results are compared with those of the finite element method program and an experiment. In this paper, the following results are obtained: (1) the best aproximation has been obtained by the ring model analysis: (2) the intersection analysis of the tapered cylinder by the ring model shows a sufficient accuracy for the stress analysis of reactor vessels.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2056-2061
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• 2001

Non-proportional loading tests of Nylon 66 at room temperature exhibit path dependent behavior and plasticity-relaxation interactions. The uniaxial formulation of the viscoplasticity theory based on overstress (VBO), which has been used to reproduce the nonlinear strain rate sensitivity, relaxation, significant recovery and cyclic softening behaviors of Nylon 66, is extended to three-dimensions to predict the response in strain-controlled, comer-path tests. VBO consists of a flow law that is easily written for either the stress or the strain as the independent variable. The flow law depends on the overstress, the difference between the stress and the equilibrium stress that is a state variable in VBO. The evolution law of the equilibrium stress in turn contains two additional state variables, the kinematic stress and the isotropic stress. The simulations show that the constitutive model is competent at modeling the deformation behavior of Nylon 66 and other solid polymers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.577-580
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• 2003

Stress state of chip formation zone is one of the main problems in metal cutting mechanics. In two-dimensional case this process is usually considered as consistent shears of work material along single of several shear surfaces. separating chip from workpiece. These shear planes are assumed to be trajectories of maximum shear stress forming corresponding slip-line field. This paper suggests new approach to the constriction of slip-line field, which Implies uniform compression in chip formation zone. On the base of given model it has been found that imaginary shear line in orthogonal cutting is close to the trajectory of maximum normal stress and the problem about its determination have been considered. It has been shown that there is a second central slip-line field inside chip, which corresponds well to experimental data about stress distribution on tool rake face and tool-chip contact length. The suggested model could be useful in solution of various problems of machining.

• Journal of Korean Academy of Nursing
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• v.37 no.6
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• pp.835-843
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• 2007

Purpose: This study examined the fitness of a path model on the relationship among stress, self-esteem, aggression, depression, suicidal ideation, and violent behavior for adolescents. Methods: The subjects consisted of 1,177 adolescents. Data was collected through self-report questionnaires. The data was analyzed by the SPSS and AMOS programs. Results: Stress, self-esteem, aggression, and depression showed a direct effect on suicidal ideation for adolescents, while stress, self-esteem, and aggression showed an indirect effect on suicidal ideation for adolescents. Stress, self-esteem, aggression, and suicidal ideation showed a direct effect on violent behavior for adolescents, while stress, self-esteem, aggression, and depression showed an indirect effect on violent behavior for adolescents. The modified path model of adolescent's suicidal ideation and violent behavior was proven correct. Conclusion: These results suggest that adolescent's suicidal ideation and violent behavior can be decreased by reducing stress, aggression, and depression and increasing self-esteem. Based on the outcomes of this study, it is necessary to design an intervention program that emphasizes reducing stress, aggression, and depression and increasing self-esteem in order to decrease adolescents' suicide ideation and violence.

• Journal of Korean Clinical Nursing Research
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• v.24 no.3
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• pp.347-355
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• 2018

Purpose: The purpose of this study was to understand morality identity, occupational stress and authentic leadership and identify factors contributing to turnover intention among intensive care unit (ICU) nurses. Methods: Data were collected from 230 nurses at the university hospitals in Daegu, Ulsan and Busan between February 15 and March 23, 2017. Instruments measuring turnover intention, moral identity, occupational stress, and authentic leadership were utilized. Statistical analysis included t-test, ANOVA, Pearson correlational analysis, and hierarchical regression analysis. Results: A total of 207 nurses in ICU participated in this study. The power of explanation with age and dependents on turnover intention was 4.1%. With inclusion of occupational stress, moral identity, and authentic leadership factors put into the model, further 20.4% was explained. The explanatory power of the turnover intention in the final model was 23.6% (F=11.63 p<.001), and occupational stress was the key factor explaining turnover intention (${\beta}=.28$, p<.001). Predictive factors contributing to turnover intention were age, occupational stress, moral identity, and authentic leadership in final model. Conclusion: These findings demonstrated occupational stress, moral identity and authentic leadership as critical factors contributing turnover intention of ICU nurses. It is necessary to promote nursing manager's authentic leadership, and to encourage moral identity in ICU nurses. In addition, providing intervention programs to reduce occupational stress for ICU nurses is necessary.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.66-71
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• 2003

The release of residual stress by mechanical loading and unloading is often performed in the fabrication of box structure fur steel bridge. The proper degree of loading and unloading is significant at release method of residual stress by mechanical loading because that degree is changed by material and geometric shape of welded structure. Therefore, the simulation model that could exactly analyze the release of residual stress by mechanical loading is to be necessary. In this study, the non-linear behavior of weldments under external loading and unloading, such as the decrease and increase of structure stiffness, was investigated by monitoring of nominal stress and strain. Tensile loading and unloading test and the proper degree of stress relaxation was measured by sectioning technique using strain gauge. Analysis model that is indispensable for the effective application of MSR method was established on the basis of test and measurement result.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.82-89
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• 1994

In this paper the effect of stress ratio on the fatigue crack growth rate of aluminum alloy A5083-O was examined. The fatigue tests were carried out using CCT (center cracked tension) specimens and CT(compact tension) specimens which were subjected to 0.5 and -1.0 stress ratio respectively. The obtained results are as follows; 1) The $\DeltaK_{th}$ as the function of stress ratio R was introduced in evaluating the fatigue crack growth rate of A5083-O. 2) A new model evaluating the effect of stress ratio on the fatigue crack growth rate was developed over the region of low and high propagation rate.

• Food Engineering Progress
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• v.13 no.1
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• pp.70-73
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• 2009

The yield stress of stirred yogurt was measured by the vane viscometer at different pre-shearing conditions, such as pre-shear speed, pre-shear time, and wait time, and temperature (12-38${^{\circ}C}$). The yield stress ranged from ~17.6 to 10 Pa and from 34.2 to 11.9 Pa, depending on the pre-shearing conditions and temperature, respectively. The preshear speed and the wait time significantly affected the yield stress. The temperature dependence of the yield stress was described by the Eyring's kinetic model. The linear function of the temperature on the yield stress was limited at the 22${^{\circ}C}$, and at the above 22${^{\circ}C}$, the yield stress was maintained to be a constant (~12.5 Pa).

• Laboraroty Animal Research
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• v.34 no.4
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• pp.203-210
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• 2018

Stress severely disturbs physiological and mental homeostasis which includes adult neurogenesis in hippocampus. Neurogenesis in hippocampus is a key feature to adapt to environmental changes and highly regulated by multiple cellular signaling pathways. The primary cilium is a cellular organelle, which acts as a signaling center during development and neurogenesis in adult mice. However, it is not clear how the primary cilia are involved in the process of restraint (RST) stress response. Using a mouse model, we examined the role of primary cilia in repeated and acute RST stress response. Interestingly, RST stress increased the number of ciliated cells in the adult hippocampal dentate gyrus (DG). In our RST model, cell proliferation in the DG also increased in a time-dependent manner. Moreover, the analysis of ciliated cells in the hippocampal DG with cell type markers indicated that cells that were ciliated in response to acute RST stress are neurons. Taken together, these findings suggest that RST stress response is closely associated with an increase in the number of ciliated neurons and leads to an increase in cell proliferation.