• Journal of the Society of Naval Architects of Korea
• /
• v.28 no.2
• /
• pp.118-131
• /
• 1991

The effects of free surface on vortex shedding phenomena around a bluff body were studied by both numerical simulation and flow visualization experiments. A vortex method, which approximates the vorticity field as the sum of discrete vortices; was used for the numerical simulation. Flow visualization experiments were performed in the KRISO cavitation tunnel. Hydrogen bubble was used as illumination material. Free surface elevation was also measured during experiments. The hydrodynamic drag and lift were predicted by numerical simulation. The predicted period of vortex shedding was compared with the results of experiments.

• Sleep Medicine and Psychophysiology
• /
• v.16 no.2
• /
• pp.85-90
• /
• 2009

Introduction: There has been an increasing interest in the relationship between sleep and suicidality. In addition, suicidal patients habitually report their sleep problems. Although sleep-related complaints and electroencephalographic changes are generally encountered in psychiatric disorders, sleep complaints such as insomnia, hypersomnia and nightmares are more common in suicidal patients. In current study, we aimed at investigating the relationship between self-reported sleep duration and suicidality in general population. Methods: One thousand general population (male:female=500:500, mean age=$39.6{\pm}11.6$ years, ranged age=20-77 years) completed Center for Epidemiologic Study-Depression (CES-D), Beck Suicide Intent scale (BSI), Spielberger State-Trait Anger Expression Inventory (STAXI), Barratt Impulsiveness Scale (BIS), Morningness-Eveningness Scale (MES) and brief questionnaire of sleep habits. Results: After controlling for age and sex, score of BSI was correlated positively with the score of CES-D, STAXI and BIS on partial correlation analysis ($r_p$=0.251; p<0.001, $r_p$=0.352; p<0.001, and $r_p$=0.175; p<0.001, respectively). In addition, score of BSI was inversely correlated with the score of MES (rp=-0.066; p=0.037). However, score of BSI showed no significant correlation with sleep duration. However, regression analysis revealed that short (<6 hrs) or long (>10 hrs) sleep duration, the family history of psychiatric illness, the score of CES-D, and the score of STAXI predicted higher score of BSI significantly in total subjects (F=17.837, adjusted $R^2$=0.166; p=0.003, p=0.003, p<0.001, and p=0.003, respectively). This model was explained better in depressed subjects with 16 or higher score of CES-D (F=9.920, adjusted $R^2$=0.298). Conclusion: Current result suggested that not only short sleep duration (<6 hrs) but also long sleep duration (>10 hrs) might be related to suicidality.

• The Journal of the Korea Contents Association
• /
• v.19 no.4
• /
• pp.120-128
• /
• 2019

Purpose: This study is a retrospective descriptive study to investigate the factors affecting sleep quality of Obstructive Sleep Apnea (OSA) patients. Methods: Data were collected from questionnaires and electronic medical records of 176 patients with obstructive sleep apnea were reviewed from 2017 to 2018. The collected data was analyzed into descriptive statistics, t-test, Pearson's correlation, and multiple regression analysis. Results: The mean age of the subjects was 49.37 years and 94.4%(n=166) had low sleep quality. The quality of sleep of the OSA patients had correlations with daytime sleepiness, and depression. The significant factors influencing quality of sleep were Gender(${\beta}=.18$, p<.004), depression(${\beta}=.50$, p<.001), dry mouth (${\beta}=.15$, p<.016), Headache(${\beta}=.17$, p<.008), explained 37.1% of the variance. Conclusion: To improve their sleep quality, required for OSA patients who have the depression, daytime sleepiness.

• Sleep Medicine and Psychophysiology
• /
• v.21 no.2
• /
• pp.74-79
• /
• 2014

Objectives: Shift work is a stressful situation. It is important to know the factors associated with the ability to adapt to a shift work schedule. The aim of the present study was to investigate the association between sleep, as well as personality variables, and the resilience of shift work nurses. Method: Self-report questionnaires were administered to 95 nurses who worked in one national university hospital. Connor-Davidson resilience scale, hospital anxiety and depression scale, morningness-eveningness scale, Pittsburgh sleep quality index, other sleep-related questionnaires, and Korean defense style questionnaires were used. Results: Age, shift work duration, off-day oversleep, depression, anxiety, adaptive defense style, and self-suppressive defense style were significantly associated with resilience (p < 0.05). Multiple regression analysis showed that age (${\beta}=0.34$, p < 0.05), depression (${\beta}=-0.25$, p < 0.05), adaptive defense style (${\beta}=0.45$, p < 0.001), and self-suppressive defense style (${\beta}=-0.19$, p < 0.05) significantly predicted the resilience of shift work nurses. Concerning individual defense mechanisms, resignation (${\beta}=-0.20$, p < 0.05), sublimation (${\beta}=0.19$, p < 0.05), omnipotence (${\beta}=0.19$, p < 0.05), and humor (${\beta}=0.20$, p < 0.05) significantly predicted the resiliency. Conclusion: The findings indicate that a specific defense style and other mechanisms were associated with the resilience of shift work nurses. A future prospective study with more participants could further clarify the relationship between sleep-related variables, as well as personality factors, and resilience of shift work nurses.

• Journal of Life Science
• /
• v.22 no.5
• /
• pp.613-620
• /
• 2012

To evaluate the effects of sleep habits on the powers of beta waves and the sensory motor rhythm of the electroencephalogram (EEG), female college student subjects were divided into four groups, according to their sleep habits, as follows: GSHG (Good Sleep Habit Group), CSHG (Common Sleep Habit Group: late bedtime), CSDG (Cognitive Sleep Disorder-Delayed Sleep Phase Syndrome Group), and NSDG (Non-cognitive Sleep Disorder-Delayed Sleep Phase Syndrome Group). Brain function was stimulated by reading a book for 3 min in the morning (9~12 am) and the EEG was measured. According to the results, the powers of the beta waves and sensory motor rhythm were not different during the resting period among the four groups. However, during the reading stimulation period, the powers of beta waves and the sensory motor rhythm in the GSHG were significantly greater than in the other groups ($p$ <0.05). Beta powers during stimulation also increased in all brain areas in the GSHG ($p$ <0.05). Interestingly, these were decreased in the frontal and temporal lobes in the CSHG by the reading stimulation ($p$ <0.05). On the other hand, sensory motor rhythm, which represents focusing efficacy, only improved in the GSHG. These results indicate that the brain's focusing function during the reading stimulation was not properly operating in the morning in the female college students who had a delayed bedtime and bad sleep habits.

• The Journal of the Convergence on Culture Technology
• /
• v.6 no.4
• /
• pp.311-316
• /
• 2020

The purpose of this study is to compare fatigue, stress and quality of sleep between good sleep quality and poor sleep quality. Fatigue, stress and quality of sleep were assessed using three questionnaires; fatigue severity scale(FSS), Perceived stress scale(PSS), and Pittsburgh sleep quality index(PSQL). As a result of the study, the higher stress(22.2 vs. 19.0, p=.000) and poorer quality of sleep(11.2 vs. 5.7, p=.000) were observed between good sleep quality and poor sleep quality groups. Our finding show that time of going to bed and stress level influenced quality of sleep.

• Sleep Medicine and Psychophysiology
• /
• v.5 no.2
• /
• pp.177-184
• /
• 1998

Objectives : Disturbance of sleep with or without sleep apnea may impair the memory function. Sleep deficiency, sleepiness, sleep apnea and emotional problem in sleep disorders can induce an impairment of memory function. Methods : In this study, the polysomnographies were administered to 58 sleep apnea patients and 38 sleep disorder patients without sleep apnea. Their clinical symptoms were quantitatively evaluated. Short term and long term memory were evaluated before and after polysom no graphy with Digit symbol test and Rey-Osterrieth complex figure test. And correlations among various sleep, repiratory and clinical variables were statistically studied in order to explore which variables may influence on memory function. Results and Conclusions : Results are as follows. Depth of sleep cis positively correlated with memory function. As sleep apnea increases and average saturation of blood oxygen decreases, memory function is more impaired. Emotional depression, high blood pressure, obesity or alcohol impaired memory function. However, daytime sleepiness was not significantly correlated with memory function. The possible mechanisms how above factors influence on the memory function were discussed.

• The Journal of the Korea Contents Association
• /
• v.15 no.1
• /
• pp.338-349
• /
• 2015

Purpose: This study was done to examine the relationship of benign prostatic hyperplasia(BPH) symptoms, anxiety, and depression, and to identify factors influencing quality of sleep in patients with BPH. Methods: 86 BPH patients were the subjects of this study. The collected data was analyzed into descriptive statistics, t-test, ANOVA, Pearson's correlation, and multiple regression analysis. Results: The quality of sleep of the BPH patients had negative correlations with BPH symptoms, anxiety, and depression. The significant factors influencing quality of sleep were house income, anxiety, explained 43.2% of the variance. Conclusion: It is necessary to develop a nursing intervention that manages anxiety decrease of the BPH patients.

• Korean Journal of Child Care and Education Policy
• /
• v.12 no.3
• /
• pp.55-76
• /
• 2018

The study aims to investigate nocturnal sleep duration in 4-year-olds and relative effects of various factors including the personal factor (temperament), the familial factor (mother's employment status), the time-use factors (hours spent in childhood educare institutions, on napping in the institutions, and on using electronic media). The data of 937 4-year-olds collected by the Korea Children and Youth Panel Survey in 2012 was analyzed. Using SPSS 21.0 program, frequency analysis, descriptive statistics, Pearson's correlation analysis and hierarchical regression were conducted. The results are as follows. First, there were significant negative correlations among the personal factor, familial factor and time-use factors. Finally, the time-use factors showed largest explanatory power on variance of children's nocturnal sleep duration, followed by the familial factor. But the personal factor was not statistically significant. These results suggested that parents and childhood educare institutions need to cooperate in order for children to sleep well. It is also necessary to implement and spread the social systems to support healthy development of children.

• Journal of the Korea Convergence Society
• /
• v.8 no.12
• /
• pp.179-187
• /
• 2017

The purpose of this study was to identify factors influencing sleep disturbance among benign prostate hyperplasia (BPH) patients in South Korea. A trained reporter filled out the questionnaire by explaining and reading the sentences to 164 BPH patients in J city. The questionnaire consisted of international prostate symptom score (IPSS), anxiety, depression, sleep disturbance. There was a statistically significant difference in sleep disturbance of participants according to income, regular exercise, and number of disease. There were statistically significant correlations between sleep disturbance and IPSS (r=.45, p<.001), anxiety (r=.59, p<.001), depression (r=.42, p<.001). The influential factors for sleep disturbance were anxiety (${\beta}=.41$, p<.001), income (${\beta}=-.36$, p<.001), IPSS (${\beta}=.28$, p=.021). These factors accounted for 41.2% of the variance in sleep disturbance. The result of this study can be used as a basic data for development of a management strategy considering convergent relationship between IPSS and anxiety in order to decrease sleep disturbance of BPH patients.