• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.69-79
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• 2011

Laboratory tests are generally used to determine the input parameters for the selected constitutive models controlling various stress and drainage conditions, but have disadvantages in that the tests are performed on the samples obtained from the bore hole which are prone to be disturbed by various factors such as the tube penetrations, sample preparations and storage. To overcome these disadvantages, it is necessary to understand the effect of disturbance on the stiffness of the sample, especially the normally consolidated clays which are generally considered as soft clays. Therefore, in this study triaxial tests are performed on the normally consolidated kaolinite to evaluate the sample disturbance effects on the stiffness and to determine the field representative input parameters. The stress path results show that the shear and coupling modulus degradation patterns with strain are affected seriously by the disturbance. However, the strengths of the normally consolidated kaolinite are little influenced by the disturbance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.479-489
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• 1989

The $J_{k}$ integral method for determining mixed mode stress intensity factors separately in the cracked anisotropic plate is developed. Stress intensity factors are indirectly determined from the values of $J_{1}$ and $J_{2}$. The $J_{2}$ integral can be evaluated efficiently from a finite element solution, neglecting the contribution from the portion of the integration contour along the crack faces, by selecting the integration contour in the vicinity of the crack tip. Using functions of a complex variable, the complete relations between $J_{1}$, $J_{2}$ and $K_{I}$ , $K_{II}$ for anisotropic materials are derived conveniently by selecting narrow rectangular contours shrinking to the crack tip. Compared to the existing path independent integral methods, the present method does not involve calculating the auxiliary solution and hence numerical procedures become quite simple. Numerical results to various problems are given and demonstrate the accuracy, stability and versatility of the method.

• Geomechanics and Engineering
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• v.17 no.1
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• pp.47-56
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• 2019

Crossing (X-type) flaws are commonly encountered in rock mass. However, the crack coalescence and failure mechanisms of rock mass with X-type flaws remain unclear. In this study, we investigate the compressive failure process of rock-like specimens containing two X-type flaws aligned in the loading direction. For comparison purposes, compressive failure behavior of specimens containing two aligned single flaws is also studied. By examining the crack coalescence behavior, two characteristics for the aligned X-type flaws under uniaxial compression are revealed. The flaws tend to coalesce by cracks emanating from flaw tips along a potential path that is parallel to the maximum compressive stress direction. The flaws are more likely to coalesce along the coalescence path linked by flaw tips with greater maximum circumferential stress if there are several potential coalescence paths almost parallel to the maximum compressive stress direction. In addition, we find that some of the specimens containing two aligned X-type flaws exhibit higher strengths than that of the specimens containing two single parallel flaws. The two underlying reasons that may influence the strengths of specimens containing two aligned X-type flaws are the values of flaw tips maximum circumferential stresses and maximum shear stresses, as well as the shear crack propagation tendencies of some secondary flaws. The research reported here provides increased understanding of the fundamental nature of rock/rock-like material failure in uniaxial compression.

• Journal of Adhesion and Interface
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• v.23 no.2
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• pp.39-43
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• 2022

In optoelectronic devices including displays and solar cells that convert electricity into light or light into electricity, it is important to control optical behavior of light to improve device efficiency. Specifically, the control of internal emitting light in the OLEDs can induce more light to go out, improving luminous efficiency. In addition, the control of optical behavior of incident light in solar cells can increase optical path in the light absorption layer, increasing power-conversion efficiency. In this study, we generated wrinkles as a physical structure to control optical behavior of light and independently controlled their wavelength and height by changing stress relaxation time. To explore the effect of wavelength and height on optical behavior, we conducted UV/Vis spectroscopy analysis of wrinkles with various heights at a constant wavelength or various wavelengths at a comparable height, figuring out a wrinkle with high aspect ratio has more dispersive light and less straight light. It indicates that high aspect ratio is required to change the optical behavior and increase the optical path.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.181-190
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• 2006

The behavior of artificially cemented sands were investigated by undrained triaxial test of isotropically consolidated sample. The cementation were induced by gypsum that is generally used for the aitificial cementation of sands. The gypsum of 5~20%(sand weight) were included in the sand and cured in the mold under the overburden pressure 55kPa. The yielding strength and stiffness of cemented sand were increased as the degree of cementation. And the dilation of sand was restricted by the cementation bonds, but after breakage of the bonds, it was increased more abrupt than the uncemented sands. The effective stress path showed that the aspects of effective pore water pressure were changed as the degree of cementation and the relative density. The effective stress ratio of cemented sand in the phase transformation line and the failure line were changed by the cementation. Generally the behavior of cemented sand more influenced by the degree of cementation than the relative density.

• Safety and Health at Work
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• v.11 no.3
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• pp.347-352
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• 2020

Background: Low self-esteem can be an issue among health-care workers due to the hierarchical medical system. Health-care workers are also in a high pressure environment that can lead to stress and burnout. This study was conducted to estimate the proportion of health-care workers with low self-esteem, high stress, and burnout and the factors associated with these in a private hospital in Bangalore city. Methods: This cross-sectional study included a random sample of health-care workers of various cadres - doctors, nurses, nursing aides, technicians, and workers in ancillary departments such as laundry, dietary, central sterile supply department, and pharmacy, with probability proportional to size. Rosenberg Scale for Self-esteem, Cohen's Perceived Stress Scale, and Shirom-Melamed Burnout Measure were used as study tools. Results: Among the 306 health-care workers, there were high levels of low self-esteem (48.4%), stress (38.6%), and burnout (48.7%), with the lowest levels being among doctors. Those aged younger than 30 years had significantly lower self-esteem and greater stress. Conclusions: Health-care workers with low self-esteem were nearly thrice more likely to suffer high stress, Odds Ratio (OR) = 2.84 (1.36-5.92), and those who were stressed had more than three times higher chance of experiencing burnout, OR = 3.6 (2.02-6.55). Path analysis showed that low self-esteem among health-care workers had a direct effect on burnout, as well as an indirect effect through stress (mediator variable). This study indicates the need for screening and counseling for low self-esteem, stress, and burnout as part of a periodic medical examination of all cadres of health workers.

• Korean journal of food and cookery science
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• v.25 no.5
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• pp.575-585
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• 2009

This study was conducted to identify the job stress factors of school foodservice employees and to examine the relationship between job stress and turnover intention through path analysis. Data was collected using a survey of 432 school foodservice employees in elementary and secondary schools in Masan, Kyungsangnam-do. All of the participants were female, and 165(52.9%) were over the age of 45' Additionally, 310(99.4%) of the respondents were married, while 287(92.0%) had less than a high school level of education. Furthermore, 271(86.9%) of the respondents were cooks. Overall, 107(34.3%) of the respondents had worked in the food industry for less than $5{\sim}10$ years. In addition, 208 (66.7%) respondents answered that they had 'never' changed jobs. Among job characteristics that causes job stress, job posture was the primary stress factor, followed by heavy work load and job condition. Job stress was found to be significantly correlated with turnover intention. Additionally, job position was the only moderating variable that was found to be correlated with job characteristics and job stress. Finally, the moderating variables influencing the effects of job stress on turnover intention were identified as performance confidence, job career, and job position. The results of this study will be useful for future studies conducted to evaluate the development of job environments and performance to minimize turnover and job inefficiency as a result of job stress.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.134-153
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• 1988

This paper was carried out to investigate the existence of a unique stress- strain behavior by obtaining some factors influencing the time dependent stress- strain behavior of clay. The results obtained from this study were summarized as follows ; 1. The relationship between stress ratro and strain in normally consolidated clay was in- dependent on pre-shear consolidation pressure. Therefore, shear strain could be expressed as a function with stress ratio. 2. The constitutive equation of shear strain on Modified Carn Clay Model coincided better with the observed value than Cam Clay Model. 3. The relationships between deviator stress and shear strain, between pore water pressure and shear strain were unified by the mean equivalent pressure. 4. The shear strain contour in norrnally consolidated clay was increased linearly through origin, but that in overconsolidated clay was not in accordance with the result of the former. 5. Because the effective stress path of normally consolidated clay was unified by the mean equivalent pressure, state boundary surface in (e,p,q) space was transformed into two dimensional surface. But it was considered to be suitable that the unified stress- strain in overconsolidated clay be expressed by a function with overconsolidation ratio. 6. The deviator for constant strain was increased linearly with increment of strain rate ($\varepsilon$) on semi-log scale, but pore water pressure was decreased. 7. The behavior of stress relaxation was transformed from linear to curvilinear with inc - rement of strain rate before stress relaxation test, and pore water pressure was increased in total range. 8. The strain of creep was increased linearly with increment of time on semi-log scale. The greater the strain rate before creep test became, the greater the increment of strain of creep became. And the pore water pressure during creep test was increased generally with increment of time on semi-log scale.

• Steel and Composite Structures
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• v.27 no.1
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• pp.13-25
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• 2018

The main objective of this study is to develop a dual approach for geometrically nonlinear finite element analysis of plane truss structures. The geometric nonlinearity is considered using the Total Lagrangian formulation. The nonlinear solution is obtained by introducing and minimizing an objective function subjected to displacement-type constraints. The proposed method can fully trace the whole equilibrium path of geometrically nonlinear plane truss structures not only before the limit point but also after it. No stiffness matrix is used in the main approach and the solution is acquired only based on the direct classical stress-strain formulations. As a result, produced errors caused by linearization and approximation of the main equilibrium equation will be eliminated. The suggested algorithm can predict both pre- and post-buckling behavior of the steel plane truss structures as well as any arbitrary point of equilibrium path. In addition, an equilibrium path with multiple limit points and snap-back phenomenon can be followed in this approach. To demonstrate the accuracy, efficiency and robustness of the proposed procedure, numerical results of the suggested approach are compared with theoretical solution, modified arc-length method, and those of reported in the literature.

• Journal of muscle and joint health
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• v.19 no.2
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• pp.142-151
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• 2012

Purpose: This study was to explore the relationships among emotional labor, social support, job satisfaction, organizational commitment, and turnover intention in healthcare providers. Methods: Participants were healthcare providers (54 male and 328 female) with a mean age of 30.28 years old. Data analysis were done with PASW 18.0 for descriptive statistics and AMOS 5.0 for path analysis. Results: The hypothetical path model showed a good fit to the empirical data (${\chi}^2$=4.178, df=2, p= .124, GFI= .997, NFI= .995, NNFI= .987, RMSEA= .053). Emotional labor, job satisfaction, and organizational commitment had significant direct effects on turnover intention. Social support had a significant direct effect on emotional labor, job satisfaction and organizational commitment, and indirect and total effect on turnover intention. Conclusion: These findings suggest that turnover prevention or education programs for healthcare providers should include maintaining good mood when interact with patients or visitors with various negative moods in healthcare setting. Further strategies may need to resolve emotional labor, enhance job satisfaction and organizational commitment, and provide social support.