• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.1013-1028
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• 2017

This paper presents key findings obtained from the numerical experiment investigating into the use of the cylindrical cavity for rock splitting operations. The stress and strain path analyses were carried out in order to provide a better insight into the crack formation. The principal stress analysis carried out along the crack line using the results obtained from these numerical analyses allowed the failure of the brittle material and the crack propagation to be investigated. This paper also suggested possible reasons for the change in crack direction observed during the rock splitting operations using the results obtained.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.28-38
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• 2008

This study was to investigate the influence of composite resins with different elastic modulus, cavity modification and occlusal loading condition on the stress distribution of restored notch-shaped noncarious cervical lesion using 3-dimensional (3D) finite element (FE) analysis. The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity and a modified cavity with a rounded apex were modeled. Unmodified and modified cavities were filled with hybrid or flowable resin. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress. The results were as follows: 1. In the unrestored cavity, the stresses were highly concentrated at mesial CEJ and lesion apex and the peak stress was observed at the mesial point angle under both loading conditions. 2. After restoration of the cavity, stresses were significantly reduced at the lesion apex, however cervical cavosurface margin, stresses were more increased than before restoration under both loading conditions. 3. When restoring the notch-shaped lesion, material with high elastic modulus worked well at the lesion apex and material with low elastic modulus worked well at the cervical cavosurface margin. 4. Cavity modification the rounding apex did not reduce compressive stress, but tensile stress was reduced.

• Journal of the East Asian Society of Dietary Life
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• v.19 no.2
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• pp.157-168
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• 2009

The principal objective of this study was to provide basic data regarding health care services for middle-aged men, via an analysis of the relationships among stress level, food habits and well-being-related attitudes with social-demographic characteristics and health-related factors. The main findings of this study were as follows. The average age of the participants was $48.7{\pm}5.2$. With regard to health status, 18.8% of the participants were diagnosed with digestive diseases within the past year. Stress levels were higher in the participants with lower levels of educational attainment. Furthermore, participants who had become divorced or lived separately from their families, participants who did not have their own houses, and participants who reported low marital satisfaction also had high levels of stress. Our food habits scores revealed meaningful differences among the study subjects, and were shown to vary with marital satisfaction, occupation, and residence type. In terms of both the importance and practice level of well-being-associated food habits, the most frequent response in this study was 'Consume home-made food rather than processed or ready-to-eat food' ($4.30{\pm}0.86$, $3.68{\pm}1.04$). In terms of importance level, the factors most relevant to well-being in terms of food habits were education level, marital satisfaction, residence type, self-assessed health status, smoking, drinking, regular exercises and leisure activities. With regard to practice levels, the degree to which subjects engaged in food habits targeted toward well-being differed meaningfully depending on marital status, marital satisfaction, residence type, family type, self-assessed health status, smoking, drinking, nutritional supplement intake, regular exercises and leisure activities. After analyzing the correlation among stress level, food habit score and the attitude towards well-being-related dietary habits (importance and practice level), we observed a meaningful relationship between the four factors at the level of p<0.001. According to the above result, continuous attention to health, including the appropriate control of smoking and drinking, as well as, stress management, via regular exercises and appropriate food habits is expected to exert a positive influence on the prevention of disease, and is also expected to improve quality of life. For all well-being-associated items, the importance level was shown to be higher than the practice level. Thus, in order to foster health-oriented food habits, we recommend that a new plan be designed, targeted toward ease of active practice for middle-aged men.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.462-470
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• 2012

Implementing the generalized Hoek-Brown failure criterion in the framework of the Mohr-Coulomb criterion requires the calculation of the equivalent friction angle and cohesion. In the conventional method based on the Balmer (1952)'s theory, the tangential instantaneous friction angle and cohesion are expressed in terms of the minimum principal stress ${\sigma}_3$, which does not provide the information about the dependency of the equivalent parameters on the hydrostatic pressure and the stress path. In this study, this defect of the conventional method has been overcome by representing the equivalent parameters in terms of stress invariants. Through the example implementation of the new method, the influence of the magnitude of the hydrostatic pressure and the Lode angle on the tangential instantaneous friction angle and cohesion is investigated. It turns out that the tangential instantaneous friction angle is maximum when the stress condition is triaxial extension, while the tangential cohesion is maximum when the stress condition is triaxial compression. The dependency of the equivalent Mohr-Coulomb strength parameters on the hydrostatic pressure and the Lode angle tends to be more substantial for the favorable rockmass of larger GSI value.

• Korea Journal of Hospital Management
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• v.17 no.1
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• pp.1-22
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• 2012

This study tires to examine affects that job and socio-psychological stresses of female office workers influence job satisfaction, organization commitment, and leaving intentions. A complete data are collected by conducting a survey with 240 female office workers from 9 medical institutions regarded as almost general hospital in Seoul. It is analyzed that the relation between socio-psychological stress and job satisfaction, organization commitment, and leaving intentions by using t-test; analysis of variance; correlation analysis; principal component analysis; linear structural equation modeling; etc. The results of this study are summarized as following. First, as it was comprehended by specific characteristics of subjects that the female office workers' level of job and socio-psychological stress, job satisfaction, organizational commitment, and leaving intention, there were statistically significant distinctions from their age, marital status, presence of children, position in the organization, type of employment, and monthly average income. Second, this study regarded relationship between the female office workers' level of job and socio-psychological stresses, job satisfaction, organizational commitment, and leaving intention. Job and socio-psychological stresses were negatively correlated with job satisfaction and organizational commitment, but the stresses were positive with leaving intention. Third, after evaluating effect that 8 features related to the job stress could influence job stress, the most effective valuables were in order to unfairness in organizational structure, workplace culture, inadequate compensation, and relationship conflict. Fourth, when looking at the overall effects of the job and sociopsychological stresses on job satisfaction, organizational commitment, and leaving intention, work autonomy was the most influencing factor of work stress levels. The level of the job stress seemed to be a prevalent impact on the leaving intention and it showed the most negative relationship that path coefficient from leaving intention to organizational commitment and also from organizational commitment to job satisfaction. Based on these findings, it can be defined that the job and socio-psychological stresses strongly influence job satisfaction, organizational commitment, and leaving intention.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.503-512
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• 2017

The perceived stress of pregnant women is a potential contributor to adverse birth outcomes. Although the importance of the psychosocial well-being of pregnant women has been emphasized, there are fewreliable and valid instruments to measure the stress level of pregnant women in Korea. This study evaluated the psychometric properties of Ahn's pregnancy related stress scale (PSS) that was originally developed in 1984. Two hundred pregnant women completed the survey questionnaire, which was comprised of the PSS, depression scale, and demographic information. Principal component analysis and confirmatory factor analysis was used to test the construct validity. The concurrent validity was evaluated using the correlation with depression scores. Based on exploratory factor analysis and a consideration of conceptual meaning, a five-factor structure was extracted, explaining 57.25% of the variance: physical discomfort, fetus, parenting, spouse relationship, and housework. The goodness-of-fit indices showed an acceptable fit overall with the full model and acceptable internal consistency (Cronbach's alpha =.89). The concurrent validity was confirmed by a comparing with the depression score (r=.48, p <.001). The shortened PSS, as a valid and reliable scale, is recommended to be used to assess pregnancy-related stress and to develop stress managing interventions for pregnant women in clinical settings.

• Tunnel and Underground Space
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• v.17 no.5
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• pp.389-410
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• 2007

For moderately jointed to massive rock masses, the failure and deformation behaviors around an excavated opening are absolutely influenced by the initial rock stress and strength of in-situ rock mass. The localized and progressive brittle failure around an opening does not mean whole collapse of an excavated opening. But, for many cases, it may induce temporary stopping of excavation works and reexamination of the current supporting system, which can result in delay of the entire construction works and additional construction cost. In this paper, the characteristics of the brittle failure around an opening with stress level and tunnel shape was studied by the biaxial compressive test using scaled specimen and by the numerical simulation with $PFC^{2D}$. The biaxial test results were well coincided with the stress induced failure patterns around the excavated openings observed and monitored in the in-situ condition. For the circular part of the opening wall, the stress induced cracks initially occurred at the wall surface in the direction of the minimum principal stress and contributed to the localized notch shaped failure region having a certain range of angle. But for the corner and straight part of the opening wall, the cracks initiated at sharp corners were connected and coalesced each other and with existing micro cracks. Further they resulted in a big notch shaped failure region connecting two sharp corners.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.401-407
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• 1984

In the previous paper, part I, the principal stresses were investigated on the normal tools and the workpieces whose materials were the same epoxy resin. In this paper, are measured and compared the stresses on the normal tools and restricted tools which have three various rake angles. Each restricted tool above has the same restricted angle. The workpieces used in this experiment are made of high quality lead. The photoelastic measuring device is attached to the saddle of the lathe and carried at the same speed as the cutting tool is feeded. The results obtained are summarized as follows; The shear stresses on the tip of the restricted tools of the rake angle .alpha.=12.deg. and .alpha.=0.deg. are less than those of normal tools. But, for the rake angle .alpha.=-12.deg., the former is greater than the latter. The result of photoelastic method shows that in the range of rapid decreasing of normal stress on the tool edge, the shear is maintaining a certain value.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.361-366
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• 2002

The deterioration of concrete structure due to corrosion of the reinforcement has created big financial losses on the overall industries. The volume expansion of the corrosion products causes internal pressure to concrete wall around reinforcing bar. If the maximum principal stress induced by internal pressure exceeds the tensile strength of the concrete at any point of time, a crack forms at any point of material. Therefore, in terms of life assessment of concrete structure, it is very important to predict the amount of corrosion products which induces initial concrete cracking. With this objective, this paper proposes the critical amount of corrosion products at interface between reinforcement and concrete using finite element analysis. If an actual survey of corrosion rates could be made, the model might supply information for condition assessment of existing concrete structure. As the mechanical properties of corrosion product and instantaneous geometry of corroded steel are considered in the analysis, the value obtained will be more realistic.

• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1597-1604
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• 2012

Genus Bacillus is a spore-forming bacterium that has unique properties in cell differentiation, allowing the forming of spores in stress conditions and activated in the vegetative cell, with suitable environments occurring during the life cycle acting as a trigger. Their habitat is mainly in soil; thus, many species of Bacillus are associated with plants as well as rhizosphere bacteria and endophytic bacteria. Signal transduction is the principal mechanism of interactions, both within the cell community and with the external environment, which provides the subsequent functions or properties for the cell. The antimicrobial compounds of Bacillus sp. are potentially useful products, which have been used in agriculture for the inhibition of phytopathogens, for the stimulation of plant growth, and in the food industry as probiotics. There are two systems for the synthesis of these substances: nonribosomal synthesis of cyclic lipopeptides (NRPS) and polyketides (PKS). For each group, the structures, properties, and genes of the main products are described. The different compounds described and the way in which they co-exist exhibit the relationship of Bacillus substances to plants, humans, and animals.