• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.9
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• pp.1227-1238
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• 2000

This study examines the effects of the discretization schemes on numerical solutions of viscoelastic fluid flows. For this purpose, a temporally evolving mixing layer, a two-dimensional vortex pair interacting with a wall, and a turbulent channel flow are selected as the test cases. We adopt a fourth-order compact scheme (COM4) for polymeric stress derivatives in the momentum equations. For convective derivatives in the constitutive equations, the first-order upwind difference scheme (UD) and artificial diffusion scheme (AD), which are commonly used in the literature, show most stable and smooth solutions even for highly extensional flows. However, the stress fields are smeared too much and the flow fields are quite different from those obtained by higher-order upwind difference schemes for the same flow parameters. Among higher-order upwind difference schemes, a third-order compact upwind difference scheme (CUD3) shows most stable and accurate solutions. Therefore, a combination of CUD3 for the convective derivatives in the constitutive equations and COM4 for the polymeric stress derivatives in the momentum equations is recommended to be used for numerical simulation of highly extensional flows.

• The Journal of Korean Medicine
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• v.29 no.1
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• pp.134-145
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• 2008

Objectives : This study investigated the relationship between drinking, smoking and stress of workers by analyzing heart rate variability. The subjects were workers in the automobile manufacturing industry. Methods : The subjects consisted of 21,239 and 19,999 industrial workers who had received health examination by Korean oriental medicine and submitted questionnaires about drinking history and smoking history, during 8 months from April to November. The subjects were categorized into drinking history and smoking history. The heart rate variability was measured for five minute at rest using SA-3000P (Medicore) and reported stress severity as stress index, stress resistance and fatigue. We analyzed the relationship between drinking, smoking and stress into frequencies, $x^2$-test using the SPSS Ver. 12.0. Results : Regarding the relationship between drinking and stress index orstress resistance, there was no statistically significant difference, but regarding the relationship between drinking and fatigue, the drinker group had a significantly higher level of fatigue than the non-drinker group. There was a statistically significant difference in stress index, stress resistance and fatigue between the current-smoker group and others. Stress resistance of the current-smoker group had lower levels than the non-smoker group or ex-smokers. On the other hand, stress index and fatigue of the current-smoker group had higher levels than the non-smoker group or ex-smokers. Conclusions : The above results revealed that drinking and smoking could put workers under a lot of stress. Smoking workers were especially apt to be under stress and had difficulty in alleviating stress.

• Korea-Australia Rheology Journal
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• v.11 no.3
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• pp.225-232
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• 1999

This study presents 1-dimensional simple model for sheet casting or rectangular fiber spinning process. In order to achieve this goal, we introduce the concept of force flux balance at the die exit, which assigns for the extensional flow outside the die the initial condition containing the information of shear flow history inside the die. With the Leonov constitutive equation that predicts non-vanishing second normal stress difference in shear flow, we are able to describe the anisotropic swelling behavior of the extrudate at least qualitatively. In other words, the negative value of the second normal stress difference causes thickness swelling much higher than width of extrudate. This result implies the importance of choosing the rheological model in the analysis of polymer processing operations, since the constitutive equation with the vanishing second normal stress difference is shown to exhibit the characteristic of isotropic swelling, that is, the thickness swell ratio always equal to the ratio in width direction.

• Journal of Mechanical Science and Technology
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• v.20 no.3
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• pp.382-390
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• 2006

The present study proposes a modified temperature-dependent non-Newtonian viscosity model and investigates the flow characteristics and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The combined effects of temperature dependent viscosity, buoyancy, and secondary flow caused by the second normal stress difference are considered. Calculated Nusselt numbers by the modified temperature-dependent viscosity model give good agreement with the experimental results. The heat transfer enhancement of viscoelastic fluid in a rectangular duct is highly dependent on the secondary flow caused by the magnitude of second normal stress difference.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.4
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• pp.261-270
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• 2021

Purpose : The purpose of this study is to investigate the effects of sleep duration on stress and depression in college students. The results obtained will be used as a foundational framework for fostering a healthy sleep culture among college students and for formulating measures to improve the quality of their sleep. Ultimately, we intend to produce a publicity and educational material. Methods : For this study, a survey involving 100 college students was conducted, after which data based on a final total of 95 respondents were analyzed. The information on stress and depression were first analyzed in terms of general characteristics and then organized based on the data collected to investigate the effects of sleep duration on stress and depression. The participants were divided into the following groups: "less than 6 hours," "6 to 7 hours," and "7 to 8 hours." BEPSI-K (Brief encounter psychosocial instrument-Korean) was used for stress evaluation, while K-CESD-R (Korean version of center for epidemiologic studies depression scale-revised) was utilized for depression evaluation. Results : First, according to sleep duration, the BEPSI-K scores showed a statistically significant difference in each group (p<.01). In the post-hoc test, there was a difference among the "less than 6 hours" group, the "7 to 8 hours" group. A statistically significant difference was noted (p<.01). In addition, sleep duration had a statistically significant effect on the negative (-) direction of the BEPSI-K (p<.01). Second, the K-CESD-R score according to sleep duration showed a statistically significant difference in each group (p<.01). Notably, in the post-hoc test, the "less than 6 hours" group differed from the "6 to 7 hours" group, "7 to 8 hours" group. A statistically significant difference was noted (p<.01). In addition, sleep duration had a statistically significant effect on the negative (-) direction of the K-CESD-R (p<.01). Third, for the correlation between sleep duration and stress and depression, a negative (-) correlation was found between sleep duration and BEPSI-K and K-CESD-R. Meanwhile, a positive (+) correlation was found between BEPSI-K and K-CESD-R. Conclusion : Based on the findings of this study, the sleep duration of college students has an effect on stress and depression. The results of this study can be used as a foundational framework in formulating a plan for improving the quality of sleep of college students.

• Journal of Naturopathy
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• v.7 no.2
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• pp.51-62
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• 2018

Purpose: The purpose of this study was to investigate the changes of stress and cumulative stress in 49 people and the changes of job stress, socio-psychological stress and anxiety relief levels by conducting a survey of 85 people after Gyorae forest bathing. Methods: The level of stress was measured using the uBioMacpa, and questionnaire was conducted to derive the data. Results: In the stress level after the forest bath, the control group showed no significant and the experimental group showed a significant decrease in the bathing (p<.043). In the cumulative stress change, the control group showed no significant difference after the bathing, but experimental group decreased significantly (p<.02), and in the variance analysis, there was a significant difference between the groups, and also between the group and the before and after tests (p<.002). In the questionnaire about job stress, there was no significant difference in physical environment and job demand. Overall, in the case of job stress, there was a significant decrease (p<.001). Job autonomy, relationship conflict, organizational unfairness, inadequate compensation, and workplace culture also had a significant decrease in stress (p<.001). The social psychological stress was significantly decreased after bathing (p<.001). The state anxiety decreased significantly (p<.001) after forest bathing. Conclusions: After the forest bathing in the Gyorae forest, the stress and anxiety are both reduced and significant, providing basic information that is very helpful as a natural healing place for stress relief.

• Journal of Korean Public Health Nursing
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• v.30 no.1
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• pp.93-104
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• 2016

Purpose: The purpose of this study was to determine the relationship among infertility stress, depression and Resilience of infertile women during infertility treatment. Methods: As a descriptive study, we surveyed 129 infertile women in 1 fertility center from November 2014 to January 2015. The data was analyzed in SPSS WIn 18.0 program. Results: Infertility stress, depression, and resilience averaged $3.23{\pm}.32$ (range of scale 1~6), $1.42{\pm}.39$ (range of scale 1~4), and $3.45{\pm}.35$ (range of scale 1~5), respectively. There was significant difference in infertility stress by job, abortion experience after pregnancy with infertility treatments, anxiety of high risk pregnancy, burden of pregnancy, important of having child. There was significant difference in depression by job, Economy burden on infertility treatment, burden of pregnancy. Infertility stress had a positive correlation with depression (r=.192. p<.029) Resilience had a negative correlation with depression (r=-.349. p<.001). Conclusion: It is necessary to provide infertile women with the counseling on their infertility stress and depression, and the intervention programs for infertile women is expected to help them cope and adapt with their personal and marital problems, reduce their negative emotions, and thus promote their quality of life.

• Journal of The Korean Society of Integrative Medicine
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• v.4 no.3
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• pp.31-37
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• 2016

Purpose : The purpose of this study was to conduct a music listening program and investigate its effects on depression and academic stress. Method : 30 male and female at K university located in Busan Metropolitan City were selected as subject of this study and a half of them was experimental group, other were control group. An academic stress tester formed by modifying and supplementing sentences and vocabularies of the questionnaire developed by Oh, Mi Hyang and Cheon, Seong Mun (1994) to help understanding of students was used with Beck Depression Inventory (BDI) by Beck(1967), both before and after conductance of music listening program. Result : First of all, In the Academic stress was no difference between each group and there was no difference in effect according to the comparison period. Second, Score of depression in Experimental group was decreased after application of music listening program than control group's. Third, Score of depression in Experimental group was lower than control group's, depending on period. Conclusion : Put the results of this research together, music listening program dosen't affect the academic stress. But this program deceased the depression. In further study, it will be required to subdivided for academic stress and depression study from evaluation of the several times and apply a variety of diseases.

• Journal of Physiology & Pathology in Korean Medicine
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• v.25 no.4
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• pp.728-733
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• 2011

This study was designed to analyze the results of stress index by heart rate variability test. The subjects were workers in the automobile manufacturing industry. The subjects consisted of 23,767 workers who had answered about questionnaires of a job position, age, smoking, drinking, exercise state and sex. The stress index(SI) and stress resistance(SR) were examined by SA3000P. We analyzed the differences of SI and SR according to job positions, ages, the state of smoking, drinking, exercise and sex by T-test or ANOVA with SPSS ver. 17.0. Regarding the differences of SI among job positions, the SI was highest in sales positions. Among ages, the SI was highest in 30s. In smoking, the SI was lower in non-smoking group. In drinking, there was no significant differences in SI. In exercise, the SI was lower in exercise group. In sex, there was no significant difference. The case of SR, SR was lowest in sales positions. Among ages, the SR was lowest in 40s. In smoking, the SR was lower in smoking group. In drinking, there was no significant differences in SR. In exercise, there was no significant difference. In sex, the SR was lowest in male. According to these results, we should establish the methods of controlling stress from the perspective of Korean traditional medicine.

• The Journal of Korean Academic Society of Nursing Education
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• v.21 no.1
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• pp.65-74
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• 2015

Purpose: This study was carried outto compare dietary self-efficacy, obesity stress, and obesity-related quality of life (OQOL) according to BMI and stages of change in vegetable consumption. Methods: A convenience sample of 326 nursing students agreed to complete a questionnaire. Data were collected from October 7 to October 18, 2013. Results: Obesity stress and obesity-related quality of life were significantly different according to BMI. Dietary self-efficacy showed a significant difference between the pre-contemplation/contemplation stage, preparation stage, and action/maintenance stage (F=50.18, p<.001). With obesity stress, there was a significant difference between the PC/C, P, and A/M stages (F=17.63, p<.001). Dietary self-efficacy had a positive correlation with OQOL (r=.11, p<.001) and a negative correlation with obesity stress (r=-.14, p=.012). And obesity stress had a negative correlation with OQOL (r=-.45, p<.001). Conclusion: These findings emphasize that nutritional-intervention programs for changes in behavior during the PC/C and P stages of change in vegetable consumption need to develop strategies to enhance dietary self-efficacy for nursing students.