• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1801-1806
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• 2004

Stochastic nature of subgrid-scale stress causes the predictability problem in large eddy simulation (LES) by which the LES solution field decorrelates with field from filtered directnumerical simulation (DNS). In order to evaluate the predictability limit in a priori sense, the information on the interplay between resolved scale and subgrid-scale (SGS) is required. In this study, the analysis on the inter-scale interaction is performed by applying tophat and cutoff filters to DNS database of flow over a circular cylinder at Reynolds number of 3900. The effect of filter shape is investigated on the interpretation of correlation between scales. A critique is given on the use of tophat filter for SGS analysis using DNS database. It is shown that correlations between Karman vortex and SGS kinetic energy drastically decrease when the cutoff filter is used, which implies that the small scale universality holds even in the presence of the large scale coherent structure.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.3
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• pp.107-115
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• 2017

The purpose of this study is to find and compare the differences in stress level, stressor, and coping style of high school students according to their personality traits. And to identify the personality traits contributing to stress reduction. The results of the study can be used as basic data for reducing the stress of adolescents to improve their academic achievement and maintain mental and physical stability. The questionnaire survey was conducted for 10 days from June 7 to June 16, 2017 for S high school students in Chungbuk Province. The study employed four measuring instruments as Ego-gram, Ok-gram, stressor scale, and stress coping type scale. Individual personality traits were classified into ego-states and ok-states in TA (Transactional Analysis). Stressors are classified into 5 categories (school life, home life, human relationship, myself, environment) and stress coping styles are classified into 4 categories (problem-focused coping, social-support coping, feeling-focused coping, hope-thinking coping) used in the previous studies. The collected data were analyzed using T-test, ANOVA, and multiple regression analysis. As a result, the stress level of high school students showed significant differences according to sex, year, grade, sleeping time, personality traits, and coping styles. Personality traits that contributed to the stress increase were NP, AC, 'you positive', 'i negative' and personality trait that contributes to stress reduction is 'you negative.' Therefore, we can judge that individual personality traits have significant effects on stress level, stressor, and coping style and need to find the effective stress management method suitable for individual personality traits using counseling, repetition training, self-suggestion etc.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.1
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• pp.47-58
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• 2004

The $textsc{k}$-$\varepsilon$ algebraic stress model (KEASM) was applied to atmospheric dispersion simulation using the Lagrangian particle dispersion model and was compared with the most popular turbulence closure model in the field of atmospheric simulation, the Mellor-Yamada (MY) model. KEASM has been rarely applied to atmospheric simulation, but it includes the pressure redistribution effect of buoyancy due to heat and momentum fluxes. On the other hand, such effect is excluded from MY model. In the simulation study, the difference in the two turbulence models was reflected to both the turbulent velocity and the Lagrangian time scale. There was little difference in the vertical diffusion coefficient $\sigma$$_{z}$. However, the horizontal diffusion coefficient or calculated by KEASM was larger than that by MY model, coincided with the Pasquill-Gifford (PG) chart. The applicability of KEASM to atmospheric simulations was demonstrated by the simulations.s.

• Structural Engineering and Mechanics
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• v.69 no.2
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• pp.145-153
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• 2019

Modified couple stress formulation and first order shear deformation theory are used for magneto-electro-elastic bending analysis of three-layered curved size-dependent beam subjected to mechanical, magnetic and electrical loads. The governing equations are derived using a displacement field including radial and transverse displacements of middle surface and a rotation component. Size dependency is accounted based on modified couple stress theory by employing a small scale parameter. The numerical results are presented to study the influence of small scale parameter, initial electric and magnetic potentials and opening angle on the magneto-electro-elastic bending results of curved micro beam.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.330-331
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• 2005

It was found possible to evaluate the temperature at which major scale failure takes place during cooling by installing a most modem acoustic emission(AE) analytical system. Ultra low carbon steel and low carbon steels containing a few minor alloying elements were oxidized in air at 900, 1050 and $1200^{\circ}C$ for 20 min, and then cooled in vacuum at 30, 70 and $110^{\circ}C/min$. The significance of the present research is the evaluation of the spallation temperature and thus the calculation of apparent thermal stress for scale spallation using the difference between oxidation temperature and spallation temperature. They were assessed as 0.22 to 0.68, 0.45 to 1.80, and 0.65 to 1.95 GPa for oxidation at 900, 1050 and $1200^{\circ}C$, respectively.

• Journal of the Korean Home Economics Association
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• v.29 no.1
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• pp.203-216
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• 1991

Coping strategy and mid-life crisis were examined in a sample of 325 mid-life couples ranging in age 40∼59. Each participant was administered stressful life event scale, coping strategy scale, family cohesion scale and mid-life crisis scale. The results were as follows: 1. There is no significant differences between husbands and wives in the experiences of stressful life event, but the perceived stress level of wives significantly higher than the husband's. 2. Husbands seem to use problem solving strategy and wives seem to use restrain strategy more often. 3. Wives appear significantly higher mid-life crisis than husbands. Especially family cohesion and passive coping strategy have turned out to be significant on the mid life crisis of couples. Besides these predictors, experiences of stressful life event and perceived stress level are significant predictors for husband's mid-life crisis. As for wive's mid-life crisis, coping stratigies are significant predictors.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.6
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• pp.253-266
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• 2020

The extended slip-weakening model was investigated by using a compiled set of source-spectrum-related parameters, i.e. seismic moment M_o, S-wave velocity V_s, corner-frequency f_c, and source-controlled high-cut frequency fmax, for 113 shallow crustal earthquakes (focal depth less than 25 km, M_W 3.0~7.5) that occurred in Japan from 1987 to 2016. The investigation was focused on the characteristics of stress drop, radiation energy-to-seismic moment ratio, radiation efficiency, and fracture energy release rate, G_c. The scaling relationships of those source parameters were also investigated and compared with those in previous studies, which were based on generally used singular models with the dimensionless numbers corresponding to f_c given by Brune and Madariaga. The results showed that the stress drop from the singular model with Madariaga's dimensionless number was equivalent to the breakdown stress drop, as well as Brune's effective stress, rather than to static stress drop as has been usually assumed. The scale dependence of stress drop showed a different tendency in accordance with the size category of the earthquakes, which may be divided into small-moderate earthquakes and moderate-large earthquakes by comparing to M_o = 10¹⁷~10¹⁸ Nm. The scale dependence was quite similar to that shown by Kanamori and Rivera. The scale dependence was not because of a poor dynamic range of recorded signals or missing data as asserted by Ide and Beroza, but rather it was because of the scale dependent V_r-induced local similarity of spectrum as shown in a previous study by the authors. The energy release rate G_c with respect to breakdown distance D_c from the extended slip-weakening model coincided with that given by Ellsworth and Beroza in a study on the rupture nucleation phase; and the empirical relationship given by Abercrombie and Rice can represent the results from the extended slip-weakening model, the results from laboratory stick-slip experiments by Ohnaka, and the results given by Ellsworth and Beroza simultaneously. Also the energy flux into the breakdown zone was well correlated with the breakdown stress drop, ${\tilde{e}}$ and peak slip velocity of the fault faces. Consequently, the investigation results indicate the appropriateness of the extended slip-weakening model.

• Korean Journal of Psychosomatic Medicine
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• v.29 no.2
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• pp.136-143
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• 2021

Objectives : The coronavirus disease 2019 (COVID-19) outbreak is a global medical crisis imposing particular burden on public sector employees. The aim of this study was to investigate the psychiatric distress among public sector workers amid the COVID-19 pandemic. Methods : We conducted a cross-sectional study with 531 public sector workers in Gwangmyung city who completed Korean versions of the Perceived Stress Scale (PSS), Patient Health Questionnaire-9 (PHQ-9), and Impact of Event Scale-Revised-Korean (IES-R-K). Results : The results revealed more than moderate levels of stress (85.2%), depressive symptoms (22.2%), and posttraumatic stress symptoms (38.8%). PSS total score was significantly correlated with PHQ-9, IES-R-K total scores as well as IES-R-K subscale scores. Total scores on the PSS, PHQ-9, and IES-R-K were all inversely correlated with age. Conclusions : COVID-19-related workers experience considerable stress and depressive symptoms, with self-rated stress correlating significantly with depression scores. Age may serve as a protective factor against occupational stress and burnout. These findings highlight the need for adequate psychiatric screening and intervention for public sector workers.

• Physical Therapy Rehabilitation Science
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• v.11 no.1
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• pp.43-48
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• 2022

Objective: In the present study, to determine the extent of academic stress and pain from sitting for a long time, we will use a questionnaire to examine the effects of non-face-to-face stress and back pain on college students who have conducted non-face-to-face lectures. Design: Survey research Methods: A questionnaire was conducted using Naver foam to identify academic stress, attitude and time to listen to lectures, and the extent of back pain for college students who are experiencing non-face-to-face lectures. Outcome measures include the scale of academic stress (SAS), the Numeric rating scale (NRS), the Oswestry Disability Index (ODI Korea version) was implemented. The difference in academic stress was analyzed by t-test and one-way ANOVA, and the correlation between academic stress and back pain was analyzed using the Spearman correlation coefficient. In order to examine the academic stress, consistency, and stability, the reliability of the academic stress items was measured by examining the reliability with the Cron-Bach alpha coefficient. Allstatistical significance levels were α=0.05. Results: According to the general characteristics of the subject, there were no statistically significant results compared to gender (P<0.05), but the higher the grade, the higher the stress index, the higher the level of pain. Conclusions: This study confirmed that non-face-to-face lectures caused by COVID-19 have increased academic stress and the resulting increase in back pain in college students.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.3
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• pp.11-23
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• 2023

Purpose : The stress of job-seeking college students is gradually worsening due to the continuing recession in the job market. Therefore, this study aims to verify whether intervention with an 'aromatherapy education program,' which combines theory and practice, has greater effect on stress, self-efficacy, and autonomic nervous system function than simple inhalation of essential oils in female college students preparing for employment. Methods : A single-blind, randomized controlled trial was conducted once a week for a total of 4 weeks with 29 female college students preparing for employment. Interventions included essential oil inhalation combined with an aromatherapy education program (experimental group(EG), n=14) and essential oil inhalation alone (control group(CG), n=15); measurements were taken before, immediately after, and 2 weeks after completion of the intervention. Evaluations were conducted using the job-seeking stress scale, stress VAS, self-efficacy scale, and a pulse-wave measuring instrument. Results : There were significant differences between the CG and EG groups with repeated measurements of job-seeking stress (p=.003), cognitive stress (p<.001), and self-efficacy (p<.001). There was a significant interaction between group and time. There were also significant differences between the CG and EG in terms of autonomic nervous system changes stress index(p=.047), total power(p=.029), high frequency(p=.036), and low frequency/high frequency ratio(p=.049). However, there was no significant difference in low frequency between the groups. Conclusion : The aromatherapy education program was more effective in improving job-seeking stress, cognitive stress, self-efficacy, and autonomic nervous system function than simple essential oil inhalation. For the aromatherapy education program to be useful as a complementary intervention for stress management in job seekers, it will be necessary to gather additional evidence of its efficacy by conducting follow-up studies with diverse participants and expanding the numbers, and durations, of the interventions.