• Journal of Mechanical Science and Technology
• /
• v.20 no.3
• /
• pp.335-344
• /
• 2006

A comprehensive review of through thickness transverse residual stress distributions in a range of as-welded and mechanically bent components made up of a range of steels has been carried out, and simplified generic transverse residual stress profiles for a plate and pipe components have been proposed. The geometries consisted of welded pipe butt joints, T-plate joints, tubular T-joints, tubular Y-joints and a pipe on plate joints as well as cold bent tubes and pipes. The collected data covered a range of engineering steels including ferritic, austenitic, C-Mn and Cr-Mo steels. Measured residual stress data, normalised with respect to the parent material yield stress, has shown a good linear correlation versus the normalised depth of the region containing the residual stress resulting from the welding or cold-bending process. The proposed simplified generic residual stress profiles based on the mean statistical linear fit of all the data provides a reasonably conservative prediction of the stress intensity factors. Whereas the profiles for the assessment procedures are fixed and case specific, the simple bilinear profiles for the residual stresses obtained by shifting the mean and bending stress from the mean regression line have been proposed and validated.

• The Korean Journal of Emergency Medical Services
• /
• v.3 no.1
• /
• pp.43-54
• /
• 1999

This study is attempted for the purpose of clearly understanding the stressors which emergency medical technology students experience during clinical practice, giving guidance in desirable direction and improvement of clinical practice, and giving the basic materials so that emergency medical technology students may practice effectively. The design of this study was a descriptive survey. The subjects in this study were 59 emergency medical technology students who were 2nd grade in D college. The collection of questionnaires took 3 days from September 1, 1999 to September 3, 1999. This researcher explained the purpose of this study to students, after they agreed to this survey, the researcher gave the questionnaire to them, had them answer the questions and collected the questionnaire immediately. Data analysis included percentage, mean and standard deviation, t-test and ANOVA trough SPSS computer program. The results of this study are, briefly, as follows; 1. In 'satisfaction-degree to specializing in the science of emergency medical technology' 27.1% of the subjects is revealed as 'satisfied' and in 'satisfaction-degree of clinical practice', 8.5% of the subjects is revealed as 'satisfied'. 2. Viewed from each of the categories of stressors which emergency medical technology students experience during clinical practice, 'ideals and values' is the category in which emergency medical technology students experience most severe stress at a mean 3.25 and 'personal relations' is the category in which emergency medical technology students experience mildest stress at a mean 2.82. The total stress degree mean is 3.06, which emergency medical technology students experience during clinical practice is revealed as 'moderate' stress. 3. Considering the stressor involved in each category, the results are as follows; (1) In 'environment', 'orientation to the hospital before clinical practice' is revealed as the most severe stressor at a menu 3.44. (2) In 'personal relations', 'relations with doctor and nurse' is revealed as the most severe stressor at a mean 3.59. (3) In 'role', 'unilaterally when their role is seems to be obscure' is revealed as the most severe stressor at a mean 4.10. (4) In 'ideals and values', 'difference between college practice and hospital practice' is revealed as the most severe stressor at a mean 3.88. (5) In 'activity', 'repetition of simple and functional work during clinical practice' is revealed as the most severe stressor at a mean 3.98. (6) In 'total stress factors', 'unilaterally when their role is seems to be obscure' is revealed as the most severe stress factor at a mean 4.10 and 'relations with comrade students' is revealed as the stress factor causing mildest stress at a mean 2.20. 4. Considering the relationship between the categories of stressors and the general characteristics, the results are as follows; (1) 'Environment' is revealed as being positively correlated with 'satisfaction degree of clinical practice'(F=3.53, p= .0359). (2) 'Ideals and values' is revealed as being correlated with 'sex'(t=-2.31, p= .0240) and 'satisfaction degree of clinical practice'(F=3.31, p= .0438).

• Bulletin of the Korean Chemical Society
• /
• v.24 no.2
• /
• pp.178-182
• /
• 2003

The stress and the heat-flux auto-correlation functions in the Green-Kubo formulas for shear viscosity and thermal conductivity have non-decaying long-time tails. This problem can be overcome by improving the statistical accuracy by N (number of particles) times, considering the stress and the heat-flux of the system as properties of each particle. The mean square stress and the heat-flux displacements in the Einstein formulas for shear viscosity and thermal conductivity are non linear functions of time since the quantities in the mean square stress and the heat-flux displacements are not continuous under periodic boundary conditions. An alternative to these quantities is to integrate the stress and the heat-flux with respect to time, but the resulting mean square stress and heat-flux displacements are still not linear versus time. This problem can be also overcome by improving the statistical accuracy. The results for transport coefficients of liquid argon obtained are discussed.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.19 no.3 s.31
• /
• pp.146-157
• /
• 2006

Objective : This study is to explore the various of the stress by perceived by paitents with Bell's palsy Methods : 50 patients who were diagnosed as Bell's palsy were sequentially interviewed and examined Results : The results were as follows 1. The mean average PWI(Psychosocial well-being index, total : score)was $41.58{\pm}17.53$ :Factor I(Social performance and self-confidence) with a mean of $11.18{\pm}8.38$, Fact II( Depression) with a mean of $8.94{\pm}6.26$, Factor III(Sleeping disturbance and anxiety) with a mean $of7.56{\pm}5.20$, Factor IV(General well-being and vatality)with a mean $of9.90{\pm}4.44$ 2. With the respect to the general characteristics of subjects, there were statistically significant differences in the patients's stress perception by sex, having an occupation and the amount of sleeping time. Conclusions : We needed the further study about the relation between stress and Bell's palsy

• Journal of Korean Society for Quality Management
• /
• v.23 no.1
• /
• pp.41-49
• /
• 1995

This paper suggests optimal accelerated constant stress life tests in Exponential distribution. The relationship between the log-mean life and the loaded stress is assumed to be linear. Optimal plans considering mean square errors of maximum likelihood estimators of the log mean life and test costs are obtained. We consider accelerated life tests with two stress levels, and as data types, failure censoring( type II) and time censoring(type I) data are used. We propose the procedure to obtain the optimal plans for each case. Some examples are also included.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.23 no.11 s.170
• /
• pp.1970-1981
• /
• 1999

The low-cycle fatigue behaviour of a SiC-particulate-reinforced Al-Si cast alloy with two different volume fractions has been investigated from a series of strain-control led fatigue tests with zero and nonzero tensile mean strains. The composites including the unreinforced matrix alloy, exhibited cyclic hardening behaviour, with more pronounced strain-hardening for the composites with a higher volume fraction of the SiC particles. For the tensile mean strain tests, the initial high tensile mean stress relaxed to zero for the ductile Al-Si alloy, resulting in no influence of the tensile mean strain on the fatigue life of the matrix alloy. However, tensile mean strain for the composite caused tensile mean stresses and reduced fatigue life. The pronounced effects of mean strain on the low-cycle fatigue life of the composite compared to the unreinforced matrix alloy were attributed to the initial large prestrain and non-relaxing high tensile mean stress in the composite with very limited ductility and Cyclic plasticity. Fatigue damage parameter using strain energy, density efficiently accounted for the mean stress effects. Predicted fatigue life using the damage parameter correlated fairly well with the experimental life within a factor of 3. Also, the fatigue damage parameter indicated the inferior life in the low-cycle regime and superior life in the high-cycle regime for the composite, compared to the unreinforced matrix alloy.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.99-104
• /
• 2001

Effect of mean stress on the fatigue life of natural rubber for engine mount was investigated. Fatigue damage parameter based on the maximum Green-Lagrange strain was employed to account for the effect of mean stress. A procedure to predict the fatigue life of rubber components based on the maximum Green-Lagrange strain method was proposed. Nonlinear finite element analysis and fatigue test of jang-gu shape specimen were conducted to predict the fatigue life of engine mount. Predicted fatigue lives have a good agreement with tested lives within a factor of 3.

• Journal of Distribution Science
• /
• v.14 no.5
• /
• pp.91-96
• /
• 2016

Purpose - Although various studies have been conducted on the stress of service employees, there are still lack of studies regarding job stress and job satisfaction of call center workers. Especially there are quite few studies on the job stress according to employment type. This study focused on job stress and job satisfaction for call center employees and the correlation between the two factors and aimed to provide basic materials for seeking for the plans to reduce job stress and improve job satisfaction. Research design, data, and methodology - Frequency, percentage, and mean value were calculated through descriptive statistics in order to find out demographic characteristics, level of job stress, and job satisfaction. Differences in job stress according to employment type were calculated by using one-way ANOVA. Correlation between job stress and job satisfaction were identified through empirical analysis with Pearson's correlation coefficient. 150 materials were used for final analysis. The collected materials were analyzed to get statistics by using SPSS 20. Results - First, as for the job stress of call center workers, overall mean value was 2.54 in 4-point scales. Among the six sub-factors, job demands had the highest score, which was 2.67. Second, as for the job stress according to employment type, others showed higher score than mean value followed by contract job and full-time job in that order, in terms of job insecurity and organizational system. In terms of inappropriate remuneration, contract job showed higher score than mean value followed by others and full-time job. Third, as for the satisfaction with job, the mean value was 2.37 in 4-point scale and "very much satisfied" was only 3.3%. Lastly, in terms of job stress and job satisfaction, all sub-factors except for job demands showed significant correlation. The more job stress increased, the more job satisfaction decreased. Conclusions - First, as a result of analyzing job stress according to the employment type of call center workers, job stress increased more when the employment type was not full-time. Therefore, it was assumed that self-rescue efforts should be followed for effective employment management of call center business where contract employment takes most part as well as efforts to transfer them to full-time job. Second, decrease in job satisfaction of call center workers may affect the performance of an organization as well as service quality of the company providing the service. Therefore, various supports are required to decrease job stress and increase job satisfaction for call center workers through the expansion of rest area or break time. Third, I could recognize that there were lack of academic research on call center business in the whole service industry. Therefore, further research should be conducted more actively in the future. In particular, this study has special significance in the aspect that there were few studies on the job stress of call center workers according to employment type.

• Korean Journal of Community Nutrition
• /
• v.2 no.2
• /
• pp.169-178
• /
• 1997

Thin study measured dietary intakes in late pregnancy and psychological stress during the period of gestation and examined the roles of diet and psychological stress in pregnancy weight gain and infant birth weight. Study subjects were 98 pregnant women who delivered infants at 2 general hospitals in Taejon city. Mean weight gain during pregnancy was 14.6$\pm$4.89Kg. Mean infant birth weight was 3.39$\pm$0.62kg in males and 3.28$\pm$0.43Kg in females. Mean energy and protein intake levels were adequate, but mean iron and calcium intakes were only 61.2$\pm$14.9% and 79.1$\pm$18.2$\%$ of RDA, respectively. Fat intake which constitutes 22.0$\pm$4.3$\%$ of total energy intake, and animal protein intake which constitutes 22.0$\pm$4.3$\%$ of total energy intake, and animal protein intake which constitutes 53.7$\%$ of total protein intake were moderately high. Though mean energy, fat, animal protein, and meat protein intakes in the low psychological stress group were higher than those in the middle or high stress group, psychological stress did not significantly affect pregnancy weight gain and infant birth weight. High intakes of nutrients except for dairy protein, iron, and niacin were associated with higher pregnancy weight gain and high intakes of protein and meat protein were associated with higher infant birth weight. It is concluded that dietary intakes during pregnancy has effects on pregnancy weight gain and infant birth weight, and psychological stress has no direct effect on them.

• Journal of Biomedical Engineering Research
• /
• v.21 no.3 s.61
• /
• pp.261-271
• /
• 2000

The present study investigated flow dynamics of a two-dimensional abdominal aortic bifurcation model under sinusoidal flow conditions considering wall motion. impedance phase angle(time delay between pressure and flow waveforms), and non-Newtonian fluid using computational fluid dynamics. The wall shear stress showed large variations in the bifurcated region and the wall motion reduced amplitude of wall shear stress significantly. As the impedance phase angle was changed to more negative values, the mean wall shear stress (time-averaged) decreased while the amplitude (oscillatory) of wall shear stress increased. At the curvature site on the outer wall where the mean wall shear stress approached zero. influence of the phase angle was relatively large. The mean wall shear stress decreased by $50\%$ in the $-90^{\circ}$ phase angle (flow wave advanced pressure wave by a quarter period) compared to the $0^{\circ}$ phase angle while the amplitude of wall shear stress increased by $15\%$. Therefore, hypertensive patients who tend to have large negative phase angles become more vulnerable to atherosclerosis according to the low and oscillatory shear stress theory because of the reduced mean and the increased oscillatory wall shear stresses. Non-Newtonian characteristics of fluid substantially increased the mean wall shear stress resulting in a less vulnerable state to atherosclerosis.