• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1382-1399
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• 2023

Pressure relief valve (PRV) is one of the important control valves used in nuclear power plants, and its sealing performance is crucial to ensure the safety and function of the entire pressure system. For the sealing performance improving purpose, an explicit function that accounts for all design parameters and can accurately describe the relationship between the multi-design parameters and the seal performance is essential, which is also the challenge of the valve seal design and/or optimization work. On this basis, a surrogate model-based design optimization is carried out in this paper. To obtain the basic data required by the surrogate model, both the Finite Element Model (FEM) and the Computational Fluid Dynamics (CFD) based numerical models were successively established, and thereby both the contact stresses of valve static sealing and dynamic impact (between valve disk and nozzle) could be predicted. With these basic data, the polynomial chaos expansion (PCE) surrogate model which can not only be used for inputs-outputs relationship construction, but also produce the sensitivity of different design parameters were developed. Based on the PCE surrogate model, a new design scheme was obtained after optimization, in which the valve sealing stress is increased by 24.42% while keeping the maximum impact stress lower than 90% of the material allowable stress. The result confirms the ability and feasibility of the method proposed in this paper, and should also be suitable for performance design optimizations of control valves with similar structures.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.135-138
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• 2007

We may have had experience to use meaning of stress once at least. Because various mental and physical frustration, conflict, deprivation, and pressure have been happened around the us while we live our whole life. The stress is always existing at our surroundings as much. Now, most stress measurement method is composed of mental method and physical method. The accuracy of stress grade lacks to the disproportion of subjectivity, objectivity, and a science trait. Therefore, in this paper, we propose the index processing algorithm for a stress relief better, after mixing mental measurement result and physical measurement result.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.101-112
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• 2023

When a submerged floating tunnel is connected to the ground, there is a risk of stress concentration at the shore connection owing to the displacement imbalance caused by low confinement pressures in water and high confinement pressures in the ground. Here, the effects of the boundary condition and stiffness of the joints installed at the shore connection on the behaviors of a submerged floating tunnel and its shore connection were analyzed using a numerical method. The analysis results obtained with fixed and ground boundaries were similar due to the high stiffness of the ground boundary. However, the stability of the shore connection was found to be improved with the ground boundary as a small displacement was allowed at the boundary. The effect of the joint stiffness was evaluated by investigating the dynamic behavior of the submerged floating tunnel, the magnitude of the load acting on the bored tunnel, and the stress distribution at the shore connection. A lower joint stiffness was found to correspond to more effective relief of the stress concentration at the shore connection. However, it was confirmed that joints with low stiffness also increase the submerged floating tunnel displacement and decrease the frequency of the dynamic behavior, causing a risk of increased resonance when wave loads with low frequency are applied. Therefore, it is necessary to derive the optimal joint stiffness that can achieve both stress concentration relief and resonance prevention during the design of shore connections to secure their dynamic stability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.229-238
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• 2018

The purpose of this study is to examine the difference in the mediating effects of relief from fatigue through sleep and perceived subjective health in the relationship between perceived stress and subjective happiness in middle school students who attempted suicide. The analysis was conducted using Path analysis, the Bootstrapping method, Phantom variable and Multiple group analysis by AMOSS using the IBM SPSS 23 and IBM SPSS AMOS 23 programs with 820 middle school students who attempted suicide in the past 12 months using the raw data of the Korea Risk Behavior Web-Based Survey (2016). In the relationship between perceived stress and perceived subjective health, the indirect effect of relief from fatigue through sleep and perceived subjective health (${\beta}=-.12$, p=.003) was statistically significant. The difference in the magnitude of the two indirect effects was found to be greater for the subjective health status than for relief from fatigue through sleep (difference = .02, p=.028) and the effects were greater for the males (${\beta}=.44$, p <.001) than for the females (${\beta}=.23$, p<.001). Based on the findings, it is necessary to develop and apply an educational program that includes the factors that contribute to improving the happiness of middle school students.

• Journal of Agricultural Extension & Community Development
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• v.28 no.1
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• pp.13-23
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• 2021

This study aims to examine the market segmentation of rural healing tourists. A two-stage cluster method was used to segment the market of rural healing tourists, and the difference in satisfaction by segmented market was identified. In this study, a total of 433 cases were used for analysis. A total of four clusters of rural healing tourists were derived based on the purpose of visit and involvement with rural healing tourism. The names of each cluster were determined as 'high involvement, daily escape purpose type', 'high involvement, stress relief purpose type', 'low involvement, daily escape purpose type', and 'high involvement, exotic experience purpose type.' Each groups were found to have significant differences according to educational level, purpose of visit, companion, and expenditure. The satisfaction and the behavioral intention of rural healing tourists was highest in the group of 'high involvement, stress relief purpose type.' The results of this study suggest that the characteristics and satisfaction of rural healing tourists were differ according to the segmented group. This study suggests useful information for target marketing strategies for each segmented market according to the characteristics of rural healing tourists.

• Journal of Welding and Joining
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• v.11 no.4
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• pp.103-111
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• 1993

Recently, several high-tensile steels(e.g. 80kg and above, $2^{1/4}Cr$-1Mo)having good quality to high temperature and pressure-resistance are widely used to construct petroleum-plant and pressure vessel of heat or nuclear-power plant. However, in the steels, reheating crack at grain boundaries of the heat affected zone(HAZ) occures during post welding heat treatment(PWHT)to remove welding residual stress. In order to study theoretically the characteristics of reheating crack created by PWHT, the computer program of three-dimensional thermal-elasto-plasto-creep analysis based on finite element method are developed, and then the mechanical behavior(history of creep strain accumulation and stress relaxation, etc)of welded join in thick plate during PWTH is clarified by the numerical results.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.110-114
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• 2008

Determination of weld-induced residual stress has been an important issue in nuclear power industry because several failures were reported in dissimilar metal weld parts due to primary water stress corrosion cracking. In this context, a couple of remarkable round robin analyses were conducted to quantify the welding simulation variables and to establish optimized numerical analysis process. The purpose of the present research is to introduce welding simulation results for a safety and relief nozzle, which has a dissimilar metal weld part as well as a similar metal weld part. First, finite element analyses are carried out to calculate residual stresses at the inside of nozzle considering only dissimilar metal welding. Subsequently, residual stresses taking into account both the dissimilar and similar metal welding are computed. The similar metal weld effect is evaluated by compa

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.585-596
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• 2016

This study was designed to examine the relationships among the levels of perceived stress, dietary behaviors, physical exercise, drinking, smoking, and relief from fatigue through sleep which affect the subjective happiness in adolescents. Based on the study findings, this paper proposes the basic data required for offering practical solutions to improve the subjective happiness of adolescents. IBM SPSS 20 and AMOS 23 were used to conduct frequency and descriptive analyses, in conjunction with Pearson's correlation coefficients, the AMOS bootstrapping method and phantom variables, for the raw data obtained from the 9,599 participants included in the 11th Korea Youth Risk Behavior Web-based Survey. Those factors having a direct effect on the subjective happiness of the adolescents were the level of perceived stress, relief from fatigue through sleep, physical exercise, dietary behavior and smoking. Perceived stress had an indirect effect on subjective happiness, and the analysis of the indirect effect and significance level of multiple mediators by means of phantom variables showed that, as well as perceived stress, relief from fatigue through sleep, physical exercise, dietary behaviors, and smoking also had indirect effects on subjective happiness. Consequently, a multidisciplinary approach is needed to optimize the subjective happiness in adolescents and financial support for environmental improvements is particularly necessary.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.15 no.4
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• pp.513-521
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• 2008

Purpose: The purpose of this study was to investigate the effect of stress, social support and self-efficacy on the mental health of female undergraduate students. Method: Three hundred ninety-nine undergraduate students were conveniently selected from a university in Seoul. The instruments used in this study were stress, social support, self-efficacy, and mental health scales. ANOVA, t-test, Pearson correlation coefficients, and stepwise multiple regression with SPSS Win 16.0 Version were used to analyze the data. Results: Mental health was significantly influenced by stress, social support, self-efficacy, and monthly expenditures. These variables accounted for 44.2% of the variance in mental health. Conclusion: The important factor that was found to affect the mental health of undergraduate female students was stress. Therefore, future studies need to be pursued to develop various strategies, such as stress relief programs, for mental health promotion of female undergraduate students.

• Journal of Korean Clinical Nursing Research
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• v.14 no.3
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• pp.153-163
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• 2008

Purpose: The purpose of this research, using descriptive correlation design was to identify the extent to which the mothers having children with rare genetic metabolic diseases(MPS, PWS) have parenting stress and guilt feeling. Method: This study used PSI /SF(Abidin, 1995) and Guilt Index as devised herein. From 156 mothers, data were collected from February to July 2006, using self-administered questionnaires. This study received the approval from IRB at S Hospital (IRB File No: 2006-02-014). Data were analyzed with descriptive statistics, t-test, ANOVA, and correlation. Results: Mothers felt very high level of parenting stress and sense of guilt. Parenting stress was related positively to guilt feeling. Conclusion: These findings could help understand the families of children with rare genetic metabolic diseases and those provide basic information in developing effective counseling and education programs for relief of parenting stress and guilt feeling. This study would be significant in the fact that it is the first research, targeting on the families of children with rare genetic metabolic diseases in Korea.