• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.790-798
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• 2008

Counter-rotating axial flow fan(CRF) consists of two counter-rotating rotors without stator blades. CRF shows the complex flow characteristics of the three-dimensional, viscous, and unsteady flow fields. For the understanding of the entire core flow in CRF, it is necessary to investigate the three-dimensional unsteady flow field between the rotors. This information is also essential to improve the aerodynamic characteristics and to reduce the aerodynamic noise level and vibration characteristics of the CRF. In this paper, experimental study on the three-dimensional unsteady flow of the CRF is performed at the design point(operating point). Flow fields in the CRF are measured at the cross-sectional planes of the upstream and downstream of each rotor using the $45^{\circ}$ inclined hot-wire. The phase-locked averaged hot-wire technique utilizes the inclined hot-wire, which rotates successively with 120 degree increments about its own axis. Three-dimensional unsteady flow characteristics such as tip vortex, secondary flow and tip leakage flow in the CRF are shown in the form of the axial, radial and tangential velocity vector plot and velocity contour. The phase-locked averaged velocity profiles of the CRF are analyzed by means of the stationary unsteady measurement technique. At the mean radius of the front rotor inlet and the outlet, the phase-locked averaged velocity profiles show more the periodical flow characteristics than those of the hub region. At the tip region of the CRF, the axial velocity is decreased due to the boundary layer effect of the fan casing and the tip vortex flow. The radial and the tangential velocity profiles show the most unstable and unsteady flow characteristics compared with other position of rotors. But, the phase-locked averaged velocity profiles of the downstream of the rear rotor show the aperiodic flow pattern due to the mixture of the front rotor wake period and the rear rotor rotational period.

• Earthquakes and Structures
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• v.24 no.1
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• pp.37-51
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• 2023

Türkiye has made significant changes and updates in both seismic risk maps and design codes over time, as have other countries with high seismic risk. In this study, the last two seismic design codes and risk maps were compared for the Aegean Region (Western Türkiye) where the earthquake risk has once again emerged with the 2020 Izmir Earthquake (Mw=6.9). In this study, information about the seismicity of the Aegean Region was given. The seismic parameters for all provinces in the region were compared with the last two earthquake risk maps. The spectral acceleration coefficients of all provinces have increased and differentiated with the current seismic hazard map as a result of the design spectra used on a regional basis have been replaced by the geographical location-specific design spectra. In addition, section damage limits were obtained for all provinces within the scope of the last two seismic design codes. Structural analyses for a sample reinforced-concrete building were made separately for each province using pushover analysis. The deformations in the cross-sections were compared with the limit states corresponding to the damage levels specified in the last two seismic design codes for the region. Target displacement requests for all provinces have decreased with the current code. The differentiation of geographical location-specific design spectra both in the last two seismic design code and between provinces has caused changes in section damages and building performance levels. The main aim of this study is to obtain and compare both seismic and structural analysis results for all provinces in the Aegean Region (Western Türkiye).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.290-302
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• 2022

In this study, it was examined for the reduction of wave overtopping and water level fluctuation in front of the revetment when applying a reinforcement method to revetment where wave overtopping occurs. As a result of the study, in the case of the cross-sectional experiment. more than 70% of the wave overtopping reduction effect depending on the reinforcement conditions was occurred, and it was analyzed that the result increases by about four times or more in the comparison with the 3d test. The average water level in front of the revetment was lowered when a low crest structure was not installed. and there was a tendency to rise under the condition of low crest structures installed. In the comparison with the wave basin test, there was a difference of about 0.5 to 0.6 times when a low crest structure was not installed, and it was increased by 5.5 times after low crest structures were installed.

• Journal of Korean Physical Therapy Science
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• v.29 no.4
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• pp.1-16
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• 2022

Background: This study was conducted to examine the correlation of VDT, posture and shoulder function among each group divided by according to the neck pain disorder index (NDI) scores for female patients with neck pain. Design: Cross-sectional study. Methods: Fifty adult women with neck pain voluntarily participated in this study and the neck pain disorder index questionnaire, VDT syndrome assessment tool questionnaire, craniovertebral angle, thoracic kyphosis angle, round shoulder posture, pectoralis minor length, shoulder joint hypermobility, and serratus anterior strength tests were conducted respectively. Subjects were divided into two groups where 21 subjects were allocated to the mild pain group whom have rated below 14 points on the NDI scores, and 29 subjects were in the severe pain group, whom have rated above 15 on the NDI score. Results: The study found that in the mean difference between variables in each group, VDT syndrome showed a higher mean score in the severe pain group than the mild pain group (p<0.05). In the group correlation and regression analysis, the mild pain group showed a significant negative correlation between the craniovertebral angle and round shoulder posture (r=-0.467, p<0.05), and the round shoulder posture for craniovertebral angle was shown to have significant positive influence (B=10.162, p<0.05). The severe pain group showed that the NDI and the VDT syndrome had a significant amount of correlation (r=0.520, p<0.01), the VDT syndrome showed significant positive influence (B=0.330, p<0.05), and the craniovertebral angle showed significant negative influence (B=-0.809, p<0.05). It was also shown that shoulder joint hypermobility had a significant negative correlation with the serratus anterior strength (r=-0.437, p<0.01), and that serratus anterior strength had a significant negative influence on shoulder joint hypermobility (B=-4.175, p<0.05). Conclusion: This study is of clinical significance in that it presented variables that should be considered depending on the degree of neck pain in treating patients with neck pain and that it presented patients with not only posture but also the function of the shoulder joint as factors to consider.

• Journal of Environmental Health Sciences
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• v.49 no.2
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• pp.118-128
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• 2023

Background: The use of heated tobacco products (HTP) causes many adverse health effects. Although the use of HTP by adolescents is prevalent worldwide, research related to it is very limited. There is a considerable lack of research related to the current HTP use rather than ever-HTP use. In particular, research related to predictive factors for current HTP use in adolescents is scarce. Objectives: The purpose of this study was to analyze related characteristics according to the current use of HTP among South Korean adolescents. Methods: This was a cross-sectional study that used data from the Seventeenth Korean Youth Risk Behavior Web-based Survey (KYRBWS). A total of 54,848 students in 2021 were included in this study. Chi-square-test, multiple logistic regression analysis, and chi-square test for trend were used for analyzing related characteristics according to use of HTP. Results: Overall, 715 (1.3%) students responded as having used HTP during the last 30 days among the 54,848 students. It was found that residence type, subjective body type recognition, subjective health recognition, alcohol use, habitual drug experience, close friend current smoking, and conventional cigarette smoking were significantly associated characteristics with the current use of heated tobacco products. Comparing 'very thin recognition' with 'very fat recognition', the adjusted odds ratio (OR) was 1.93 (95% confidence interval [CI]: 1.29~2.87) for current use of HTP. Additionally, comparing 'very unhealthy recognition' with 'very healthy recognition', the aOR was 3.82 (95% CI: 2.40~6.07) for current use of HTP. Conclusions: Based on these results, residence type, subjective body type recognition, subjective health recognition, alcohol use, habitual drug experience, close friend current smoking, and conventional cigarette smoking were associated with significantly increased odds of current HTP use. Therefore, the results of this study can provide useful evidence about adolescent behaviors in predicting current HTP use.

• Journal of Korean Public Health Nursing
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• v.37 no.2
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• pp.205-217
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• 2023

Purpose: This study sought to identify the levels of coronavirus disease 2019 (COVID-19) knowledge, anxiety, nursing professionalism, and clinical practicum stress, and the factors influencing this stress in nursing students. Methods: A cross-sectional and descriptive study was conducted with the participation of 140 junior and senior nursing students recruited from three nursing colleges in Busan and Gyeongsangnam-do. Data analysis was performed using independent t-tests, Pearson's correlation coefficient, and multiple regression using the SPSS/WIN 26.0 program. Results: The study arrived at a mean score of 63.18±13.89 for clinical practicum stress, which showed a significant difference based on the perceived health status and reasons for admission to nursing school. Anxiety and professionalism exhibited a noteworthy correlation with clinical practicum stress. The significant predictors of clinical practicum stress among nursing students were perceived health status (β=.39, p<.001), anxiety (β=.25, p=.033), and the reasons for admission to nursing school (β=.17, p=.012). The total explanatory power of these variables was 23.0% (F=6.28, p<.001). Conclusion: The results of this study suggest that it is necessary to provide effective education to promote nursing professionalism during a pandemic. It is also necessary to develop and include various programs in the curriculum that strategically intervene to prevent anxiety in pre-service nurses. This would reduce the stress in the clinical practice of nursing students when faced with new infectious diseases in the future.

• Journal of Korean Biological Nursing Science
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• v.25 no.3
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• pp.172-182
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• 2023

Purpose: This study investigated the differences in physical function, self-efficacy (SE), and health-related quality of life (HRQoL) categorized by disease severity in community-dwelling patients with chronic obstructive pulmonary disease (COPD). Methods: This cross-sectional study included 182 patients with COPD selected from the pulmonology outpatient department of a tertiary hospital. Disease severity was measured using forced expiratory volume in 1 second (FEV1). Physical function, SE, and HRQoL were measured with the six-minute walking distance, Pulmonary Rehabilitation Adapted Index of Self-Efficacy (PRAISE), and St. George's Respiratory Questionnaire (SGRQ). Disease duration, FEV1, and 12-month history of exacerbations were obtained from medical records. Patients were categorized by Global Initiative for Chronic Obstructive Lung Disease (GOLD) category. Data were analyzed using the χ² test, and one-way ANOVA. Results: Most of the participants were male and nonsmokers. The disease duration was 10.76 ± 10.03 years, the mean FEV1% was 62.13 ± 22.80, and 70.3% of the participants were in GOLD category 2 (moderate) or milder. Half of the participants reported modified Medical Research Council scores ≥ 2. Patients in GOLD categories 1 and 3 (mild and severe) exhibited significantly higher PRAISE scores than those in the other groups (F = 8.23, p < .001). The total SGRQ scores were highest in GOLD 4 (very severe), indicating the lowest HRQoL. Significant differences were identified among GOLD 1, GOLD 2 and 3, and GOLD 4 (F = 9.92, p < .001). Conclusion: We identified potentially useful variables to comprehensively assess disease severity and tailor management strategies, including airflow limitation, and to determine the consequences of COPD from patients' perspectives.

• Archives of Plastic Surgery
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• v.50 no.1
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• pp.106-115
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• 2023

Background Primary contraction of full-thickness graft has been traditionally quoted to be 40%. There are lacunae in literature to elaborate on the factors influencing it ever since. Methods About 75 subjects who underwent full-thickness grafting procedures to resurface small defects were included in the study. The initial and final graft dimensions after primary contraction were traced on X-ray templates and the percentage of contraction was evaluated using the graphical method. This was further correlated with age, collagen, elastic matrix metalloproteinases-1 (MMP-1) and -2 content along with dermal thickness of the skin specimen sent from the graft. Results The primary contraction of the graft had a very significant correlation only with the initial size of graft harvested with a linear regression of 33.3% and a Spearman's correlation of 0.587 significant at a p-value of 0.001. Conclusion This study though preliminary tries to highlight an important factor that primary contraction of grafts is a physical phenomenon independent of its contents like collagen, elastin, or MMP-1 and -2 or age and dependent on its initial size of harvest instead.

• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.219-225
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• 2009

The primary purpose of this study is to build computer models referring overall flow of complex and various semiconductor wafer manufacturing process and to implement a educational model which operates with a presentation tool showing device design. It is important that Korean semiconductor industries secure high competitive power on efficient manufacturing management and to develop technology continuously. Models representing the FAB processes and the functions of each process are developed for Seoul National University Semiconductor Research Center. However, it is expected that the models are effective as visually educational tools in Korean semiconductor industries. In addition, it is anticipated that these models are useful for semiconductor process courses in academia. Scalability and flexibility allow semiconductor manufacturers to customize the models and perform simulation education. Subsequently, manufacturers save budget.

• Journal of Home Health Care Nursing
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• v.30 no.2
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• pp.202-215
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• 2023

Purpose: This study attempted to determine the factors related to behaviors of reducing exposure to endocrine disrupting chemicals (BRE to EDCs) in pregnancy, based on the PRECEDE model. Methods: A cross-sectional survey was conducted with participants (N=239) who met the medical records and eligibility criteria from the Women's Hospital and Public Health Center. Data were collected using a specially-designed questionnaire based on the PRECEDE model and included BRE to EDCs predisposing factors, reinforcing factors, and enabling factors. The data were analyzed using the chi-square test, independent t-test, one way ANOVA, Pearson's correlation coefficients and a hierarchical multiple regression analysis. Results: In Model I it was found that participation in prenatal education influenced the BRE to EDCs significantly; and a regression showed that the determinant variables accounted for 3.4%. In Model II, the predisposing factors of perceived barriers of BRE to EDCs and environmental self-efficacy were added. It was shown that they significantly influenced BRE to EDCs in the order named, and a regression revealed that increases in the determinant variables accounted for 22.5%. In Model III, to which enabling factors were added, the information acquisition experience of BRE to EDCs interacted significantly with BRE to EDCs and a regression showed an increase in the determinant variables accounting for 25.3%. Conclusion: The results of this study, the content of endocrine disruptors must be included in the prenatal care education program for pregnant women, and it should be composed of contents that can reduce the perceived obstacle to BRE to EDCs, enhance the environmental self-efficacy, and provide the information in regard to reducing exposure to EDCs.