• Nuclear Engineering and Technology
• /
• 제44권8호
• /
• pp.871-888
• /
• 2012

This paper aims at presenting the state of the art, the recent progress, and the perspective for the future, in the modelling of two-phase flow in the horizontal legs of a PWR. All phenomena relevant for safety analysis are listed first. The selection of the modelling approach for system codes is then discussed, including the number of fluids or fields, the space and time resolution, and the use of flow regime maps. The classical two-fluid six-equation one-pressure model as it is implemented in the CATHARE code is then presented and its properties are described. It is shown that the axial effects of gravity forces may be correctly taken into account even in the case of change of the cross section area or of the pipe orientation. It is also shown that it can predict both fluvial and torrential flow with a possible hydraulic jump. Since phase stratification plays a dominant role, the Kelvin-Helmholtz instability and the stability of bubbly flow regime are discussed. A transition criterion based on a stability analysis of shallow water waves may be used to predict the Kelvin-Helmholtz instability. Recent experimental data obtained in the METERO test facility are analysed to model the transition from a bubbly to stratified flow regime. Finally, perspectives for further improvement of the modelling are drawn including dynamic modelling of turbulence and interfacial area and multi-field models.

• 보건의료산업학회지
• /
• 제11권4호
• /
• pp.145-155
• /
• 2017

Objectives : To investigate the factors affecting bone mineral density in across stratified postmenopausal ages. Methods : Data from 1,698 subjects who completed the 2010-2011 National Health and Nutrition Survey were analyzed using SPSS Statistics 21.0 The $x^2$ test and one way (ANOVA) were used to verify the relationship between general characteristics and health behaviors and the prevalence of osteoporosis. Logistic regression analysis was used to verify the factors Influencing bone mineral density. Results : The bone mineral density distribution was the highest among those with osteopenia, with proportions of 21.8% in healthy subjects, 58.1% in osteopenia, and 20.0% in those with osteoporosis. The distribution of osteoporosis by age group was 5.2% among subjects in their 50s, 15.4% among those in their 60s, and 42.4% among those in their 70s. In multivariate logistic regression analysis, the prevalence of osteoporosis according to ages was significantly correlated with age, educational level, body mass index(BMI), and parity 4 of more than 1-2 babies. Conclusions : Although age is an uncontrollable factor in the prevention of osteoporosis, educational level and BMI are correctable factors to maintain bone mineral density. There is a need to maintain healthy BMI and expand osteoporosis prevention education.

• 한국학교보건학회지
• /
• 제29권3호
• /
• pp.267-276
• /
• 2016

Purpose: This study was conducted to identify the factors of suicidal ideation in middle school students by gender, and to announce the necessity of gaining upon a socio-cultural comprehension-based approach. Methods: Three middle schools were randomly selected from a pool of 21 middle schools in S City, and were stratified by school and grade. A total of 878 students were included in the analysis. Multiple logistic regression analysis was conducted to identify the factors that affect suicidal ideation by gender. Results: Suicidal ideation and depression scores of the female students were over twofold higher than those of the male students. The factor that was found to affect suicidal ideation in the male students was depression while for the female students the factors were visiting suicide-related websites, having friends who attempted to commit suicide, depression, and poor communication with one's parents. Conclusion: The findings in this study support gender differences in suicidal ideation, and suggest that building socio-cultural environments are needed to abate their negative emotions and to help youth find out their reasons to live.

• 한국보건간호학회지
• /
• 제31권3호
• /
• pp.492-504
• /
• 2017

Purpose: This study aims to investigate the effect of employment of elderly over 65 years on elderly depression using the "Nation Elderly Survey 2014". Methods: The subjects were 10,451 elderly aged 65 or older who were selected from 16 cities and provinces via multilevel stratified sampling method. In an effort to represent well the nation's elderly population, composite sample analysis method was used for the study, and a hierarchical logistic regression analysis was performed to identify those factors affecting the depression among the elderly population. Results: The factors affecting the depression were education level, household income, Perceived health status, smoking, drinking, physical activity, body mass index and employment status. It was found that the unemployed persons were 1.68 times more likely to be depressed than those who remain employed. Conclusion: Where the average life expectancy is getting longer and the poverty rate of elderly is high, employment activities of the elderly are of great significance in terms of ensuring economic stability as well as in lowering medical expenses through reduction of depression. Therefore, it is necessary to increase the employment rates of the elderly for economic, social and healthcare perspectives.

• 한국과학교육학회지
• /
• 제16권3호
• /
• pp.249-259
• /
• 1996

The purpose of this study was to analyze relationships among science achievement, science process skills and affective perception of high school students. The affective perception was included attitude toward science and science anxiety in the study. The instruments were developed HARS and SAMS for this study. The subject was sampled 1,115 students by stratified cluster sampling method. The major findings of this study were as follows: The tendency to affective perception was investigated according to students variables. Atittude toward science was showed a negative perception on female than male, in rural area than city. Science anxiety was percepted highly on female than male, in rural area than city. Attitude toward science showed positive relations to science process skills, science achievement, but which showed negative relation to science anxiety. Science anxiety showed negative relations among science process skills, science achievement and attitude toward science. Structural relationships among affective perception, science process skills and science achievement were analyzed by effect size through the path analysis on the independent and dependent variables. By the results, it was indicated that there have significant direct effect not only affective perception influence on science achievement but also on science process skills in hypothesized model. Prediction of science achievement and science process skills were clarified to characteristics of the affective perception.Therefore, understanding about affective perception will be helpful to make the strategy of science teaching

• 대한간호학회지
• /
• 제22권3호
• /
• pp.316-324
• /
• 1992

The purpose of this study was to develop a ratio scale to measure job satisfaction of nurses and health workers in health centers. Of the 224 health centers in Korea, 105 were drawn as the sample using disproportion리 stratified random sampling. The data collection period was from May 1 to June 30, 1990 and 771 nurses and health workers working at 75 health centers participated. Subjects were instructed to rate, according to the level of satisfaction, from one to four points, 42 items revised from the tool made by Stamps et. al. (1978). The internal consistency reliability of the tool was measured by Cronbach $\alpha$ and the corrected item-total correlation coefficient. As a result of the item analysis, one item was excluded since the item had negative correlation with total items. As a result of factor analysis on the 41 items with varimax or above. Labeling and numbering of 6 factors were as follows ; factor 1 (8 items) ; Professional status of job. factor 2 (6 items) ; Interaction. factor 3 (8 items) ; Autonomy. factor 4 (8 items) ; Administration. factor 5 (7 items) ; Pay. factor 6 (4 items) ; Job(Task). Further studies are needed to identify the relationship between this tool and the effectiveness of the health center and more research is needed for generalization.

• 한국자동차공학회논문집
• /
• 제13권1호
• /
• pp.9-18
• /
• 2005

The objective of this study is to analyse the spray characteristics according to the injection duration under the ambient pressure condition, and the injection timing in the visualization engine. In order to investigate the spray behavior, we obtained the spray velocity using the PIV method that has been an useful optical diagnostics technology, and calculated the vorticity from spray velocity component. These results elucidated the relationship between vorticity and entropy which play an important role in the diffusion process for the early injection case and the stratification process for the late injection case. In addition, we quantified the homogeneous diffusion rate of spray using the entropy analysis based on the Boltzmann's statistical thermodynamics. Using these method, it was found that the concentration of spray droplets caused by the increase of injection duration is more effective than the increase of momentum dissipation. We also found that the homogeneous diffusion rate increased as the injection timing moved to the early intake stroke process and BTDC $50^{\circ}$ was the most efficient injection timing for the stratified mixture formation during the compression stroke.

• Nuclear Engineering and Technology
• /
• 제37권3호
• /
• pp.245-258
• /
• 2005

This paper addresses two types of uncertainty: stochastic uncertainty and subjective uncertainty in probabilistic accident consequence assessments. The off-site consequence assessment code OSCAAR has been applied to uncertainty and sensitivity analyses on the individual risks of early fatality and latent cancer fatality in the population outside the plant boundary due to a severe accident. A new stratified meteorological sampling scheme was successfully implemented into the trajectory model for atmospheric dispersion and the statistical variability of the probability distributions of the consequence was examined. A total of 65 uncertain input parameters was considered and 128 runs of OSCAAR with 144 meteorological sequences were performed in the parameter uncertainty analysis. The study provided the range of uncertainty for the expected values of individual risks of early and latent cancer fatality close to the site. In the sensitivity analyses, the correlation/regression measures were useful for identifying those input parameters whose uncertainty makes an important contribution to the overall uncertainty for the consequence. This could provide valuable insights into areas for further research aiming at reducing the uncertainties.

• The Journal of Asian Finance, Economics and Business
• /
• 제7권10호
• /
• pp.329-338
• /
• 2020

The present study aims to investigate the perceived usefulness of business coaching as a moderator between the association of entrepreneurial competencies and business success of women micro-entrepreneurs. This study employs a stratified random sampling technique to collect data from women micro-entrepreneurs who attended business coaching sessions. In total, 261 questionnaires were distributed and collected. This study has divided the moderator (i.e., perceived usefulness of business coaching) into two groups, namely, group 1 (with a low mean) and group 2 (with a high mean) for moderation analysis. By using a comparative analysis of the path coefficient for groups 1 and 2, the path is moderated by the perceived usefulness of business coaching if the beta value for group 1 is significant, and the beta value for group 2 is non-significant. The results show that eight out of a total of sixteen hypotheses were supported, while the remaining hypotheses were rejected. The findings of the study suggest that the domains of entrepreneurial competencies for women micro-entrepreneurs, including strategic, commitment, conceptual, opportunity, and relationship competencies, together with the perceived usefulness of business coaching, are vital for the business success and should remain the principal focus of future research in women entrepreneurship.

• 대한가정학회지
• /
• 제26권2호
• /
• pp.49-67
• /
• 1988

The purpose of this study was to present a conceptual model for predicting housing quality. Housing quality was measured in three ways: perceived quality about physical features of houses, perceived level of the quality in comparison with perceived average level I urban area and housing satisfaction. The specific objectives to achieve the purpose were ; 1) to measure the perceived quality about physical features of houses and perceived level of the quality in comparison with the perceived average level I urban 2) to measure the level of housing satisfaction 3) to clarify the causality between the composite variables of housing quality. A final instrument was developed through two stage pilot surveys. The respondents were 1292 homemakers of middle and high economic class in seoul and Daejeon, selected through stratified random sampling technique. Data were collected during March and April, 1986, and analyzed using SPSS and SAS computer packages. The statistics used were frequency, percentage, F-test, Duncan's Multiple Range, x2, Cramer's V, Multiple linear Regression, Path analysis. The major finding were as follows; the variables significantly related to predict the housing quality were found. The simple, composite variables and 3 measures of housing quality were linked using path analysis, thereby a conceptual model predicting housing quality was suggested.