• Transactions of Materials Processing
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• v.24 no.1
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• pp.52-61
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• 2015

Evaluation of the elevated temperature flow stress for thermoplastic fiber metal laminates(TFMLs) sheet, comprised of two aluminum sheets in the exterior layers and a self-reinforced polypropylene(SRPP) in the interior layer, was conducted. The flow stress as a function of temperature should be evaluated prior to the actual forming of these materials. The flow stress can be obtained experimentally by uniaxial tensile tests or analytically by deriving a flow stress model. However, the flow stress curve of TFMLs cannot be predicted properly by existing flow stress models because the deformation with temperature of these types of materials is different from that of a generic pure metallic material. Therefore, the flow stress model, which includes the effect of the temperature, should be carefully identified. In the current study, the flow stress of TFMLs were first predicted by using existing flow stress models such as Hollomon, Ludwik, and Johnson-Cook models. It is noted that these existing models could not effectively predict the flow stress. Flow stress models such as the modified Hollomon and modified Ludwik model were proposed with respect to temperatures of $23^{\circ}C$, $60^{\circ}C$, $90^{\circ}C$, $120^{\circ}C$. Then the stress-strain curves, which were predicted using the proposed flow stress models, were compared to the stress-strain curves obtained from experiments. It is confirmed that the proposed flow stress models can predict properly the temperature dependent flow stress of TFMLs.

• The Journal of Korean Obstetrics and Gynecology
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• v.36 no.2
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• pp.85-100
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• 2023

Objectives: To evaluate stress patterns and coping abilities in women with infertility by conducting in-depth interviews. Methods: Ten women with infertility who visited the Korean Medicine Hospital and provided consent after being informed of the purpose and method of the study were selected after meeting the inclusion/exclusion criteria. They were requested to complete a preliminary questionnaire developed by the researchers, the Infertility Stress Scale, and the Korean version of the Fertility Problem Inventory (FPI). Subsequently, each participant was interviewed individually. Results: The preliminary questionnaire was used to evaluate sensitivity to each type of infertility-related stress and ability to express and resolve it. Among all infertility stress types, the largest proportion, accounting for an average of 47.5±26.95%, was that felt by the patient herself. Considering stress awareness intensity, the stress felt by the patient was the highest, with an average score of 4.30±0.64. Relative stress sensitivity due to infertility was the highest, with an average score of 3.90±0.94. Compared with general work stress, the average ability to relieve stress related to problems with spouses was the highest, with a score of 2.50±1.20. The average Infertility Stress Scale score was 2.88±1.35 and FPI score was 2.87±2.52. Conclusions: The highest stress scores were observed for the following items: meaning of children, need for parenthood, and stress due to the diagnosis of infertility. The lowest stress scores were allocated to the item concerning relationships with friends and co-workers. Based on the in-depth interviews conducted after the survey, stress in women with infertility may be classified as emotional, physical, and economic. Thus, the requirement for providing appropriate psychological and emotional support depending on the stress type in addition to general medical treatment for infertility treatment was confirmed.

• Nuclear Engineering and Technology
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• v.44 no.3
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• pp.343-354
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• 2012

Primary water stress corrosion cracking (PWSCC) is a major safety concern in the nuclear power industry worldwide. PWSCC is known to initiate only in the condition in which sufficiently high tensile stress is applied to alloy 600 tube material or alloy 82/182 weld material in pressurized water reactor operating environments. However, it is still uncertain how much tensile stress is re-quired to generate PWSCC or what causes such high tensile stress. This study was performed to pre-dict the magnitude of weld residual stress and operating stress and compare it with previous experi-mental results for PWSCC initiation. For the study, a pressurizer safety nozzle was selected because it is reported to be vulnerable to PWSCC in overseas plants. The assessment was conducted by nu-merical analysis. Before performing stress analysis for plant conditions, a preliminary mock-up ana-lysis was done. The result of the preliminary analysis was validated by residual stress measurement in the mock-up. After verification of the analysis methodology, an analysis under plant conditions was conducted. The analysis results show that the stress level is not high enough to initiate PWSCC. If a plant is properly welded and operated, PWSCC is not likely to occur in the pressurizer safety nozzle.

• Geomechanics and Engineering
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• v.22 no.2
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• pp.187-196
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• 2020

The changeable stress environment directly affect the propagation law of a stress wave. Stress wave propagation tests in sandstone with different axial stresses were carried using a modified split Hopkinson Pressure bar (SHPB) assuming the sandstone has a uniform pore distribution. Then the waveform and stress wave energy dissipation were analyzed. The results show that the stress wave exhibits the double peak phenomenon. With increasing axial stress, the intensity difference decreases exponentially and experiences first a dramatic decrease and then gentle development. The demarcation stress is σ/σ_c=30%, indicating that the closer to the incident end, the faster the intensity difference attenuates. Under the same axial stress, the intensity difference decreases linearly with propagation distance and its attenuation intensity factor displays a quadratic function with axial stress. With increasing propagation distance, the time difference decays linearly and its delay coefficient reflects the damage degree. The stress wave energy attenuates exponentially with propagation distance, and the relations between attenuation rate, attenuation coefficient and axial stress can be represented by the quadratic function.

• Steel and Composite Structures
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• v.27 no.1
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• pp.89-94
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• 2018

Uniaxial ratcheting behavior of Z2CND18.12N austenitic stainless steel used nuclear power plant piping material was studied. The results indicated that ratcheting strain increased with increasing of stress amplitude under the same mean stress and different stress amplitude, ratcheting strain increased with increasing of mean stress under the same stress amplitude and different mean stress. Based on least square method, a suitable method to arrest ratcheting by loading the materials was proposed, namely determined method of zero ratcheting strain rate. Zero ratcheting strain rate occur under specified mean stress and stress amplitudes. Moreover, three dimensional ratcheting boundary surface graph was established with stress amplitude, mean stress and ratcheting strain rate. This represents a graphical surface zone to study the ratcheting strain rates for various mean stress and stress amplitude combinations. The graph showed the ratcheting behavior under various combinations of mean and amplitude stresses. The graph was also expressed with the help of experimental results of certain sets of mean and stress amplitude conditions. Further, experimentation cost and time can be saved.

• Journal of Korean society of Dental Hygiene
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• v.13 no.4
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• pp.589-596
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• 2013

Objectives : The aim of the study is to investigate the influence of the stress of adults on their oral mucosal diseases, dry mouth and physical, mental stress symptoms. Structured equation model (SEM) was used to analyze the hypotheses of the study. Methods : The subjects were 500 adultsfrom July 1 to December 31, 2012. The data were analyzed using SPSS 18.0 (SPSS 18.0 K for window, SPSS Inc USA) and IBM SPSS Amos 18.0 (SPSS Inc, Chicago, IL, USA) set at the level of significance as 0.05. Results : The level of stress had a direct influence on oral mucosal diseases, and oral mucosal diseases affected stress symptoms directly. The level of stress had a significant impact on stress symptoms, and that exercised an indirect influence on stress symptoms through the medium of oral mucosal diseases and dry mouth. The level of stress affected dry mouth in a direct effects, and dry mouth had a direct impact on stress symptoms. Conclusions : The stress of adults had direct and indirect impacts on their oral health and systemic diseases. The oral health of adults should be promoted to let them stay healthy, and how to help them to get rid of their stress should be considered to improve their quality of life.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.450-460
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• 1996

To investigate the effect of stress wave propagation for crack tip, impact responses of two-dimensional plates with oblique cracks are investigated by a numerical method. In the numerical analysis, the finite element method is used in space domain discretization and the Newmark constant acceleration algorithm is used in time integration. According to the numerical results from the impact response analysis. it is found that the stress fields are bisected at the crack surface and the parts of stress intensity are moved along the crack face. The crack tip stress fields are yaried rapidly. The magnitude of crack tip stress fields are converted to dynamic stress intensity factor. Dynamic sress intensity factor appears when the stress wave has reached at the crack tip and the aspect of change of dynamic stress intensity factor is shown to be the same as the part of the flow of stress intensity.

• Journal of the Korean Society of Food Culture
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• v.35 no.5
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• pp.483-492
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• 2020

Dietary components can modulate stress, inflammatory indicators, and health risk. This study examined the relationship among diet, metabolic disease risk, and perceived stress in Korean adult females using the 2017-2018 Korea National Health and Nutrition Examination Survey. A total of 4,353 adult women aged 19-64 years were classified into four groups according to perceived stress level: very high stress group (VHSG, n=225), high stress group (HSG, n=1,079), moderate stress group (MSG, n=2,532), and low stress group (LSG, n=517). Data collection included the sociodemographics, anthropometrics, blood profile, and dietary survey. After adjusting for covariates, those in the VHSG had a higher body mass index (p=0.013) and obesity rate (p=0.053) with a shorter sleep time than the LSG group. The VHSG also tended to have a higher plasma LDL-cholesterol, hsC-reactive protein and lower levels of HDL-cholesterol, vitamin A, and vitamin E than the low stress group. High stress subjects demonstrated increased breakfast skipping frequency (p<0.0001), decreased fiber intake (p=0.001), potassium (p=0.041), and vitamin A (p=0.011) than the low stress ones. Therefore the perceived stress level was associated with the inflammatory indicators, obesity, and lack of anti-inflammatory or antioxidant nutrients. The dietary components may be an important mediator of stress and metabolic disease.

• The Korean Journal of Health Service Management
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• v.10 no.2
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• pp.193-204
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• 2016

Objectives : The purpose of this study was to identify the mediation effect of a positive stress coping strategy between clinical practice stress and clinical practice satisfaction in nursing students. Methods : In this study, data was collected from 248 nursing students at K University in South Korea from October of 2015 to November of 2015. The collected data was analyzed using the SPSS 22.0 Statistics Program. Results : Clinical practice stress and a positive stress coping strategy were significant predictors of clinical practice satisfaction (${\beta}$=.442, p<.001). The explanatory power of the measure of clinical practice satisfaction was increased to 29.3% (p<.001) with solely clinical practice stress, and it reached 44.2% (p<.001) when a positive stress coping strategy was reflected. The results of this study confirmed that a positive stress coping strategy has a mediation effect on clinical practice stress and clinical practice satisfaction levels. Conclusions : It is necessary to develop a program to take advantage of positive stress coping skills so that nursing college students can smoothly overcome stress during their clinical training and thus improve their clinical practice experience.

• Korean Journal of Human Ecology
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• v.24 no.1
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• pp.25-38
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• 2015

This paper focused to classify the consumption stress coping types among married women consumers and to investigate the differences of socio-economic variables, social class, perceived health status, and consumption stress among coping types. Data were collected from 500 married women through online surveys in South Korea. Two factors of consumption stress(consumption stress before purchase, consumption stress after purchase), and three factors of consumption stress coping(Social support coping, problem solving focused coping, Passive avoidance coping) were identified. K-mean cluster analysis classified into 4 coping types with consumption stress coping. 15% of the sample were included to the passive coping type, and 25% were classified into the ambivalent coping type. 26.8% of the sample were identified to the active coping type, and 35.2% were maladaptive coping type. There were significant differences among the consumption stress coping types on education, family income, social class, health status, consumption stress after purchase. Consumer education programs should develop and implement especially for passive coping type and maladaptive coping type to cope effectively with consumption stress.