• Journal of the Korean Data and Information Science Society
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• 제20권6호
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• pp.1169-1175
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• 2009

In this paper, the inferences of data obtained from periodic inspection and type I censoring for the step-stress accelerated life test are studied. The exponential distribution with a failure rate function that a log-linear function of stress and the tampered failure rate model are considered. The maximum likelihood estimators of the model parameters are estimated and also the optimal stress change time which minimize the asymptotic variance of maximum likelihood estimators of parameters is determined. A numerical example will be given to illustrate the proposed inferential procedures and the sensitivity of the asymptotic variance of the estimated mean by the guessed parameters is investigated.

• 대기
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• 제17권4호
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• pp.365-379
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• 2007

Global warming may shift the properties and dynamics of ENSO. We study the changes in ENSO characteristics in a coupled general circulation model, ECHO-G/S. First, we analyse the mean state changes by comparing present day simulation and various high $CO_2$ climates. The model shows a little El Nino-like changes in the sea surface temperature and wind stress in the eastern tropical Pacific. As the mean temperature rises, the ENSO amplitude and the frequency of strong El Ninos and La Nina decrease. The analysis shows that the weakening of the oceanic sensitivities is related to the weakening of ENSO. In addition to the surface changes, the remote subsurface sea temperature response in the western Pacific to the wind stress in the eastern Pacific influences the subsequent ENSO amplitude. However, ENSO amplitude does not show linear response to the greenhouse gas concentrations.

• 한국산업보건학회지
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• 제29권2호
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• pp.251-258
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• 2019

Objective: Chronic obstructive pulmonary disease(COPD) is characterized by persistent airflow limitations associated with chronic inflammatory response due to noxious particles or gases in the lung. Inflammation and oxidative stress are associated with COPD. The aim of this study was to evaluate the relationship among inflammation, oxidative stress, and airflow limitation severity in retired miners with COPD. Methods: The levels of serum high-sensitivity C-reactive protein(hsCRP) as a biomarker for inflammation, degree of reactive oxygen metabolites(dROMs) and biological antioxidants potential(BAP) in plasma as biomarkers for oxidative stress were measured in 211 male subjects with COPD. Degree of airflow limitation severity as determined by spirometry was divided into three grades grouped according to the classification of the Global Initiatives for Obstructive Lung Disease(GOLD)(1, mild; 2, moderate; $3{\leq}$, severe or more) using a fixed ratio, post- bronchodilator $FEV_1/FVC$ < 0.7. Results: Mean levels of dROMs significantly increased in relation to airflow limitation severity(GOLD 1, 317.8 U.CARR vs. GOLD 2, 320.3 U.CARR vs. GOLD $3{\leq}$, 350.9 U.CARR, p=0.047) and dROMs levels were correlated with serum hsCRP levels(r=0.514, p<0.001). Mean levels of hsCRP were higher in current smokers(non-smoker, 1.47 mg/L vs. smoker, 2.34 mg/L, p=0.006), and tended to increase with degree of airflow limitation severity(p=0.071). Mean levels of BAP were lower in current smokers(non-smoker, $1873{\mu}mol/L$ vs. smoker, $1754{\mu}mol/L$, p=0.006). Conclusions: These results suggest that inflammation and oxidative stress are related to airflow limitation severity in retired miners with COPD, and there was a correlation between inflammation and oxidative stress.

• Computers and Concrete
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• 제32권1호
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• pp.99-117
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• 2023

The crack under the influence of the higher intensities of the stresses grows and the structure gets collapsed with the time when the crack length reaches to critical value. Therefore, the fracture behavior of a structure in terms of stress intensity factors (SIF) becomes important to determine the remaining fracture strength and capacity of material and structure for avoiding catastrophic failure, increasing safety and further improvement in the design. The robustness of the method has been demonstrated by comparing the numerical results with analytical and experimental results of some problems. XFEM is used to model cracks and holes in structures and predict their strength and reliability under service conditions. Further, XFEM is extended with a stochastic method for predicting the sensitivity in terms of output COVs and fracture strength in terms of mean values of stress intensity factors (SIFs) of a structure with discontinuities (cracks and holes) under tensile loading condition with input individual and combined randomness in different system parameters. In stochastic technique, the second order perturbation technique (SOPT) has been used for the predicting the fracture behavior of the structures. The stochastic/perturbation technique is also known as Taylor series expansion method and it provides the reliable results if the input randomness is less than twenty percentage. From the present numerical analysis it is observed that, the crack tip near to the hole is under the influence of the stress concentration and the variational effect of the input random parameters on the crack tip in terms of the SIFs are lesser so the COVs are the less sensitive. The COVs of mixed mode SIFs are the most sensitive for the crack angles (α=45° to 90°) for all the values of c₁ and d₁. The plate with the shorter distance between hole and crack is the most sensitive with all the crack angles but the crack tip which is much nearer to the hole has the highest sensitivity.

• 성인간호학회지
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• 제22권4호
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• pp.418-429
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• 2010

Purpose: This study was performed to identify the relationship between Sense of Humor, Coping Humor, Perceived stress and self-esteem in the middle-aged women. Methods: Data were collected from the 20th of June to the 30th of August in 2009 from 145 middle-aged women living in Seoul. Data analysis was done with SPSS/WIN 12.0 program for descriptive statistics and Pearson correlation. Results: The mean score of the humor sense was $55.94{\pm}6.52$, coping humor was $21.11{\pm}3.82$, perceived stress was $22.21{\pm}3.03$ and self-esteem was $27.50{\pm}2.88$. Subcategories of sense of humor were that emotional expressiveness was average $20.75{\pm}2.70$, meta-message sensitivity was average $20.12{\pm}2.74$ and liking of humor was average $15.13{\pm}3.44$. Sense of humor was difference according to the economic status(t=2.000, p=.047), coping humor was difference according to the on medication use(t=2.227, p=.027). There was a significant correlation between the coping humor, perceived stress and the self-esteem. When the coping humor was higher, perceived stress was lower and the self-esteem was higher. Conclusion: This study showed that medication and economic status influences the humor scores and the sense of humor and coping humor were related to perceived stress and self-esteem in middle-aged women Therefore, these findings can provide the basis for the development of nursing intervention to increase the ability to coping with stress.

• Structural Engineering and Mechanics
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• 제49권2호
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• pp.203-223
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• 2014

The extensive use of prestressed reinforced concrete (PSC) highway bridges in marine environment drastically increases the sensitivity to both fatigue-and corrosion-induced damage of their critical structural components during their service lives. Within this scenario, an integrated method that is capable of evaluating the fatigue reliability, identifying a condition-based maintenance, and predicting the remaining service life of its critical components is therefore needed. To accomplish this goal, a procedure for fatigue reliability prediction of PSC highway bridges is proposed in the present study. Vehicle-bridge coupling vibration analysis is performed for obtaining the equivalent moment ranges of critical section of bridges under typical fatigue truck models. Three-dimensional nonlinear mathematical models of fatigue trucks are simplified as an eleven-degree-of-freedom system. Road surface roughness is simulated as zero-mean stationary Gaussian random processes using the trigonometric series method. The time-dependent stress-concentration factors of reinforcing bars and prestressing tendons are accounted for more accurate stress ranges determination. The limit state functions are constructed according to the Miner's linear damage rule, the time-dependent S-N curves of prestressing tendons and the site-specific stress cycle prediction. The effectiveness of the methodology framework is demonstrated to a T-type simple supported multi-girder bridge for fatigue reliability evaluation.

• 한국보건간호학회지
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• 제35권1호
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• pp.47-59
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• 2021

Purpose: To assess levels of mental health among community health practitioners during the COVID-19 outbreak in Korea and associations between practitioner mental health and personal and psychosocial factors. Methods: Data were collected from a convenient sample of 275 community health practitioners using an online questionnaire, which included items on mental health (K-WEMWBS), psychosocial factors (COVID-19 sensitivity, COVID-19 self-confidence, social support, perceived stress), and personal characteristics. Collected data were analyzed using the t-test, one-way ANOVA, Scheffe's test, Pearson's correlation coefficients, and multiple linear regression in SPSS 25.0. Results: Mean mental health score was 51.27±8.47. Multiple linear regression revealed that time spent as a community health practitioner, COVID-19 self-confidence, social support, and perceived stress were significantly associated with mental health. Conclusion: The findings of this study suggest that comprehensive intervention with emphases on improving COVID-19 self-confidence, social support, and reducing stress is required to improve community health practitioner mental health. The results also indicate a need for educational programs aimed at improving the mental health of young community health practitioners.

• 품질경영학회지
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• 제35권3호
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• pp.107-117
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• 2007

The fatigue has been considered the most failure mode of metal, ceramic, and composite materials. In this paper, numerical experiments to asses the usefulness of two Dixon's methods(small and large samples) and 14 S-N methods on assumptions of lognormal fatigue limit distribution under RFL(Random Fatigue Limit) model are conducted for staircase(or up-and-down) test and compared by MSE(Mean Squared Error) and bias for estimates of mean log-fatigue limit. Also, guidelines for staircase test plans to choose initial stress level and step size are recommended from numerical experiments including sensitivity analyses. In addition, the parametric bootstrap method to construct a confidence interval for the mean of log-fatigue limit by the percentile method using a transition probability matrix of Markov chain is presented and illustrated with an example.

• 대한핵의학회지
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• 제25권2호
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• pp.165-176
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• 1991

The purpose of this study was to assess the ability of quantitative Tl-201 tomography to identify and localize coronary artery disease (CAD). The study population consisted of 41 patients (31 males, 10 females; mean age $55{\pm}7$ yr) including 14 with prior myocardial infarction who underwent both exercise Tl-201 myocardium SPECT and coronary angiography for the evaluation of chest pain. From the short axis and vertical long axis tomograms, stress extent polar maps were generated by Cedars-Sinai Medical Center program, and the % stress defect extent (SDE) was quantified for each coronary artery territory. For the purpose of this study, the coronary circulation was divided into 6 arterial segments, and the "myocardial ischemic score" (MIS) was calculated from the coronary angiogram. Sensitivity for the detection of CAD ($\geq50%$ coronary stenosis by angiography) by angiography) by stress extent polar map was 95% in single vessel disease, and 100% in double and triple vessel deseases. Overall sensitivity was 97%. Sensitivity and specificity for the detection of individual diseased vessels were, respectively, 87% and 90% for the left anterior descending artery (LAD), 36% and 93% for the left circumflex artery (LCX), and 71% and 70% for the right coronary artery (RCA). Concordance for the detection of individual diseased vessels between the coronary angiography and stress polar map was fair for the LAD (kappa=0.70), and RCA (kappa=0.41) lesions, whereas it was poor for the LCX lesions (kappa : 0.32). There were siginificant correlations between the MIS and SDE in LAD (rs=0.56, p=0.0027), and RCA territory (rs=0.60, p=0.0094). No significant correlation was found in LCX territory. When total vascular territories were combined, there was a significant correlation between the MIS and SDE (rs=0.42, p=0.0116). In conclusion, the quantitative analysis of Tl-201 tomograms appears to be accurate for determining the presence and location of CAD.

• Journal of Hospice and Palliative Care
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• 제24권4호
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• pp.235-244
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• 2021

Purpose: This study aimed to provide basic data for developing interventions to relieve the end-of-life care stress experienced by pediatric nurses by examining the relationships of end-of-life care stress with compassionate competence and attitudes toward end-of-life care. Methods: Data were collected via a survey that was conducted from September 10 to September 30, 2018 and administered to 113 nurses who had worked for more than 6 months in a pediatric unit at a tertiary hospital in Seoul, South Korea. The data were analyzed for frequency, percentage, mean, and standard deviation, and the independent t-test, one-way analysis of variance, and Pearson correlation analysis were conducted using SPSS version 25.0. Results: End-of-life care stress among pediatric nurses had a weak positive correlation (r=0.216, P<0.05) with compassionate competence and had no significant correlation with attitudes toward end-of-life care. Among the sub-factors of end-of-life care stress, psychological difficulties had a weak positive correlation with sensitivity (r=0.309, P<0.01) and communication (r=0.230, P<0.05), which are aspects of compassionate competence. Lack of knowledge about end-of-life care had a weak positive correlation with communication (r=0.209, P<0.05) as an aspect of compassionate competence. Conclusion: To improve the quality of end-of-life care provided by pediatric nurses, it is necessary to improve their compassionate competence and reduce their end-of-life care stress by developing education and support programs tailored to the characteristics of children and specific communication methods.