• Nuclear Engineering and Technology
• /
• 제55권4호
• /
• pp.1382-1399
• /
• 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.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2007년도 춘계종합학술대회
• /
• pp.135-138
• /
• 2007

누구나 한번쯤은 스트레스란 말을 사용해본 경험이 있을 것이다. 왜냐면 살아가는 동안 주변의 여러 가지 정신적 육체적 압박, 갈등, 좌절, 결핍 등이 발생하기 때문이다. 그만큼 스트레스는 우리 주변에 언제나 존재하고 있다. 현재 대부분의 스트레스 측정방식은 심리적 방법과 생체적 방법으로 이루어져 있는데, 주관성, 객관성, 그리고 과학성의 불균형으로 스트레스 정도의 정확성이 부족하다. 따라서 본 논문에서는 심리적 측정결과와 생체적 측정결과를 혼합해서 지수화 하여 보다 스트레스 완화에 도움이 되기 위한 지수 처리 알고리즘을 제안한다.

• Geomechanics and Engineering
• /
• 제33권1호
• /
• pp.101-112
• /
• 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.

• 한국산학기술학회논문지
• /
• 제19권4호
• /
• pp.229-238
• /
• 2018

본 연구의 목적은 자살시도를 한 중학생의 스트레스 인자와 주관적 행복감의 관계에서 잠으로 피로회복, 주관적 건강인지를 이용하여 다중매개효과 차이를 파악하고자 함이다. 2016년(제 12차) 청소년건강형태온라인조사 원시자료에서 최근 12개월 동안 자살시도를 한 적이 있는 중학생 820명을 대상으로 IBM SPSS 23과 IBM SPSS AMOS 23 프로그램을 이용하여, 경로분석, 부트스트래핑, 팬텀변수, 다중집단분석으로 분석하였다. 연구결과 스트레스 인지와 주관적 행복감의 관계에서 잠으로 피로회복과 주관적 건강인지는 간접효과(${\beta}=-.12$, p=.003)가 통계적으로 유의하였다. 스트레스 인지와 주관적 행복감의 관계에서 잠으로 피로회복 간접효과는 -.05(p=.004), 주관적 건강인지 간접효과는 -.09(p=.004)로, 두 변수의 간접효과 크기 차이는 주관적 건강인지가 잠으로 피로회복보다 -.02(p=.028) 효과크기가 큰 것으로 나타났다. 남 여 중학생 집단별 경로 간 효과 크기의 차이를 본 결과 남학생집단(${\beta}=.44$, p<.001)이 여학생집단(${\beta}=.23$, p<.001) 보다 효과가 큰 것으로 나타났다. 연구결과를 바탕으로 자살시도 중학생의 행복감 증진에 도움이 되는 스트레스인지, 잠으로 피로회복, 주관적 건강인지 내용이 포함된 교육 프로그램의 개발 및 적용되어야 할 것이다.

• 농촌지도와개발
• /
• 제28권1호
• /
• pp.13-23
• /
• 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
• /
• 제11권4호
• /
• pp.103-111
• /
• 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.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.110-114
• /
• 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

• 한국산학기술학회논문지
• /
• 제17권7호
• /
• pp.585-596
• /
• 2016

본 연구는 청소년의 스트레스 인지, 식생활, 신체활동, 음주, 흡연, 잠으로 피로회복 정도에 따라 주관적 행복감에 미치는 영향을 파악하고, 이를 바탕으로 향후 청소년의 주관적 행복감을 향상시키는 실질적인 방안을 위한 기초자료를 제공하고자 한다. 2015년 제11차 청소년건강행태온라인조사 원시자료의 9,599명을 대상으로 IBM SPSS 20.0과 IBM SPSS AMOS 23 프로그램을 이용하였으며, 빈도분석, 기술통계, 상관분석, 부트스트래핑과 팬텀변수를 이용하였다. 연구결과, 주관적 행복감에 가장 많은 영향을 미치는 직접효과는 스트레스 인지(${\beta}=-.457$, p =. 005), 잠으로 피로회복(${\beta}=.136$, p = .004), 신체활동(${\beta}=.055$, p = .005), 식생활(${\beta}=-.035$, p = .014), 흡연(${\beta}=-.030$, p = .011이었다. 스트레스 인지가 주관적 행복감으로 가는 경로의 간접효과(${\beta}=-.052$, p = .006)가 있었으며, 팬텀변수를 이용하여 다중매개의 간접효과 크기와 유의도를 분석한 결과 스트레스 인지와 주관적 행복감 사이에 간접효과는 잠으로 피로회복(${\beta}=-.041$, p = .001), 신체활동(${\beta}=-.007$, p = .003), 식생활(${\beta}=-.003$, p = .008), 흡연(${\beta}=-.002$, p = .001)순으로 나타났으며, 음주는(${\beta}=000$, p = .636) 간접효과가 없었다. 그러므로 청소년의 주관적 행복감을 증진시키기 위하여 다학제간의 협력이 요구되며 가정, 학교, 지역사회 및 국가차원의 교육환경 개선과 인력 및 재정적 지원이 모색되어야 할 것이다.

• 기본간호학회지
• /
• 제15권4호
• /
• pp.513-521
• /
• 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.

• 임상간호연구
• /
• 제14권3호
• /
• pp.153-163
• /
• 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.