• Geomechanics and Engineering
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• v.5 no.6
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• pp.499-517
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• 2013

In order to investigate shear behavior of granular materials due to excavation and associated unloading actions, load-controlled plane strain compression tests under decreasing confining pressure were performed under drained conditions and the results were compared with the conventional plane strain compression tests. Four types of granular material consisting of two quartz sands and two glass beads were used to investigate particle shape effects. It is clarified that macro stress-strain behavior is more easily influenced by stress level and stress path in sands than in glass beads. Development of localized deformation was analyzed using photogrammetry method. It was found that shear bands are generated before peak strength and shear band patterns vary during the whole shearing process. Under the same test condition, shear band thickness in the two sands was smaller than that in one type of glass beads even if the materials have almost the same mean particle size. Shear band thickness also decreased with increase of confining pressure regardless of particle shape or size. Local maximum shear strain inside shear band grew approximately linearly with global axial strain from onset of shear band to the end of softening. The growth rate is found related to shear band thickness. The wider shear band, the relatively lower the growth rate. Finally, observed shear band inclination angles were compared with classical Coulomb and Roscoe solutions and different results were found for sands and glass beads.

• Structural Engineering and Mechanics
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• v.12 no.6
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• pp.685-698
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• 2001

In this paper, a general method for the automatic search for Strut-and-Tie (S&T) models representative of possible resistant mechanisms in reinforced concrete elements is proposed. The representativeness criterion here adopted is inspired to the principle of minimum strain energy and requires the consistency of the model with a reference stress field. In particular, a highly indeterminate pin-jointed framework of a given layout is generated within the assigned geometry of the concrete element and an optimum truss is found by the minimisation of a suitable objective function. Such a function allows us to search the optimum truss according to a reference stress field deduced through a F.E.A. and assumed as representative of the given continuum. The theoretical principles and the mathematical formulation of the method are firstly explained; the search for a S&T model suitable for the design of a deep beam shows the method capability in handling the reference stress path. Finally, since the analysis may consider the structure as linear-elastic or cracked and non-linear in both the component materials, it is shown how the proposed procedure allows us to verify the possibilities of activation of the design model, oriented to the serviceability condition and deduced in the linear elastic field, by following the evolution of the resistant mechanisms in the cracked non-linear field up to the structural failure.

• The Journal of Korean Society for School & Community Health Education
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• v.17 no.3
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• pp.1-10
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• 2016

Objectives: The purpose of this study was to verify correlation between social support & psychosocial stress and drinking behavior after consuming alcohol among college students. Methods: This study surveyed by questionnaire 440 students who consumed alcohol regularly from 36 colleges around the country in 2014. Data were analyzed using the program SPSS 21. Results: The effects of social support on problem behavior after drinking and psychosocial stress had significant influence with each path coefficient -0.178(CR= -3.408, p<0.001) and -0.294(CR= -6.195, p<0.001). Also, the effects of psychosocial stress on problem behavior after drinking had significant influence with path coefficient -0.141(CR= -2.858, p<0.05). Social support had significant influence(p<0.001) on problem behavior after drinking through psychosocial stress, serving as a mediator variable, and social support had significant influence on problem behavior after drinking through psychosocial stress. Conclusions: Problem behavior after consuming alcohol held strong relevance in social support and psychosocial stress.

• Journal of Korean Academy of Nursing
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• v.48 no.5
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• pp.578-587
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• 2018

Purpose: This study aimed to understand the mechanisms of decision regret and stress of family surrogates' end-of-life decision making using an exploratory path model. In particular, the research identified the direct effects of perceptions of uncertainty and effective decisions on decision regret and stress, and examined the indirect effects of being informed, having clear values, and being supported for decision regret and the stress of end-of-life decision making through the mediating variables of perceptions of uncertainty and effective decisions. Methods: Data were collected from 102 family surrogates who had participated in end-of-life decision making for patients with terminal cancer in a tertiary hospital. Results: Perception of effective decisions was a significant direct predictor of decision regret, and uncertainty was a significant predictor of stress among the participants. Being informed, having clear values, and being supported had a significant indirect influence on decision regret through the perception of effective decisions among family surrogates. However, only having clear values had a significant indirect influence on stress through the perception of uncertainty. The model explained 63.0% of decision regret and 20.0% of stress among the participants and showed a good fit with the data, ${\chi}^2=12.40$ (df=8, p=.134), TLI=.97, and RMSEA=.07. Conclusion: Nurses can support family surrogates in end-of-life decision-making processes to decrease their decision regret by providing information about end-of-life care choices, clarifying personal values, and supporting the decision-making process, and to relieve their stress by facilitating the clarification of personal values.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.579-584
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• 2003

Solenoid type magnetic actuator is the device, which could translate the electromagnetic energy to mechanical force. The force generated by magnetic flux, could be calculated by Maxwell stress tensor method. Maxwell stress tensor method is influenced by the magnetic flux path. Thus, magnetic force could be improved by modification of the iron case, which is the route of the magnetic flux. Modified design is obtained by parameter optimization using by Response surface methodology.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.57-63
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• 2008

In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio ($\tau_{sat}$) and increase of the thermal injection velocity ($V_{inj}$) contribute the increase of mobility. It is also shown that the decrease of the $\tau_{sat}$ is due to the decrease of the mean free path ($\lambda_O$). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased $V_{inj}$ because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.55-63
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• 2018

This study was intended to identify path structures through pathway analysis with an emphasis on the cognitive elements that influence the acculturative stress of marriage-based immigrant women. The results of the study were designed to establish a foundation for practical measures and policies to support marriage-based immigrant women to adjust their lives in the culture. This study has established research model on the path structure according to the psychological stress theory as to how social support, coping strategy, and acculturative attitude recognized as a cognitive element of marriage-based immigrant women on the acculturative stress and implement practical verification. In addition, control variables for the use of ages, education level, period of marriage, and income level of socio-demographic variables were analyzed. To obtain data for the study, convenience sampling and snowball sampling of marriage-based immigrant women that resided in the area of C and J were conducted simultaneously through surveys and applied to the analysis of 204 cases. Analysis of the path structure of influence of social support, coping strategies, and acculturative attitudes that were perceived as a cognitive element of marriage-based immigrant women influencing acculturative stress revealed that these factors were specifically weighted towards acculturative. Moreover, comprehensive acculturative attitude was identified as a crucial variable reducing the effects of acculturative stress during the acculturative procedures of marriage-based immigrant women. This assumes that establishing and performing policies supporting co-existence of homeland cultures of marriage-based immigrant women and Korean cultures might be an efficient action for dealing with acculturative stress rather than forcing them to adjust to Korean culture.

• Journal of Families and Better Life
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• v.34 no.4
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• pp.37-49
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• 2016

The purpose of this study was to examine the mediating effect of inner resilience and external resilience on the relationship between the job stress of early childhood education teachers and their teaching flow. Data were collected through questionnaires from 221 early childhood Korean teachers in the InCheon area. The instruments used in this study were the Kindergarten Teachers' Job Stress Scale, Early Childhood Teachers' Resilience Scale, and Teaching Flow Scale. The data were analyzed by Pearson's correlation analysis, multiple regression analysis, and Baron and Kenny's method. It was adapted to SPSS ver. 18.0 for Windows. This study followed a mediated effect model. First, there was a negative correlation between the job stress and teaching flow. There was a positive correlation between the teaching flow and the resilience. Secondly, there was a negative correlation with job stress and teaching flow in path model 1. In path model 2, there was a positive correlation with resilience and teaching flow. Teaching flow was statistically and significantly influenced by resilience. Thirdly, there was the mediating effect of inner resilience and external resilience on the relationship between the job stress of early childhood education teachers and their teaching flow. These results can be used as the basic data for the improvement of early childhood education teachers' teaching flow in the future.

• Computers and Concrete
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• v.19 no.1
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• pp.59-68
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• 2017

This study focused on modeling the behavior of the compressive stress using the average strain and ultrasonic test results in concrete. Feed-forward backpropagation artificial neural network (ANN) models were used to compare four types of concrete mixtures with varying water cement ratio (WC), ordinary concrete (ORC) and concrete with short steel fiber-reinforcement (FRC). Sixteen (16) $150mm{\times}150mm{\times}150mm$ concrete cubes were used; each contained eighteen (18) data sets. Ultrasonic test with pitch-catch configuration was conducted at each loading state to record linear and nonlinear test response with multiple step loads. Statistical Spearman's rank correlation was used to reduce the input parameters. Different types of concrete produced similar top five input parameters that had high correlation to compressive stress: average strain (${\varepsilon}$), fundamental harmonic amplitude (A1), $2^{nd}$ harmonic amplitude (A2), $3^{rd}$ harmonic amplitude (A3), and peak to peak amplitude (PPA). Twenty-eight ANN models were trained, validated and tested. A model was chosen for each WC with the highest Pearson correlation coefficient (R) in testing, and the soundness of the behavior for the input parameters in relation to the compressive stress. The ANN model showed increasing WC produced delayed response to stress at initial stages, abruptly responding after 40%. This was due to the presence of more voids for high water cement ratio that activated Contact Acoustic Nonlinearity (CAN) at the latter stage of the loading path. FRC showed slow response to stress than ORC, indicating the resistance of short steel fiber that delayed stress increase against the loading path.

• Journal of Korean Academy of Nursing
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• v.41 no.5
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• pp.663-672
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• 2011

Purpose: Purpose of this study was to investigate the status of depression in academic high school students and path analysis model for exploring the mediating role of entrapment to depression in relation to academic stress and perceived social support. Methods: Measurements were four reliable questionnaires measuring academic stress, social support, entrapment, and depression. Data were collected from students in 17 high schools in Seoul. Results: Students (n=5,346) completing the questionnaires indicated depression & entrapment from academic stress. Depression was more prevalent in girls, those whose parents' household income was less than two million won, who did not live with father or mother or both due to divorce, separation, or death, and those who smoked or used alcohol. Entrapment was more prevalent in students similar to cases of depression and in seniors. According to the proposed path model, 48.6% of depression was explained by academic stress, social support, and entrapment. The indirect effect of entrapment as a mediator between academic stress and depression was verified and larger than the direct effect of academic stress on depression. Conclusion: Considering levels of depression and entrapment demonstrated by these students, better mental health programs with diverse strategies should be developed for their psychological well-being.