• Journal of the Society of Naval Architects of Korea
• /
• v.46 no.6
• /
• pp.688-698
• /
• 2009

In this paper, the steady lift force acting on a slender body moving beneath regular wave systems of arbitrary wavelengths and directions of propagation is considered. The momentum conservation theorem and the strip method are used to obtain the hydrodynamic forces acting on the body and affecting its motions on the assumption that the body is slender. In order to obtain the vertical steady force acting on it, or the free surface suction force, the second-order hydrodynamic forces caused by mutual interactions between the components of the first-order hydrodynamic forces are averaged over time. The validity of the method is tested by comparison of the calculated results with experimental data and found to be satisfactory. Through some parametric calculations performed for a typical model, some useful results are obtained as to the depth of submergence of the body, wavelengths, directions, etc.

• Sleep Medicine and Psychophysiology
• /
• v.23 no.2
• /
• pp.61-67
• /
• 2016

Objectives: We aimed to evaluate the effects of mattress type on both objective and subjective sleep quality in healthy good sleepers. Methods: Fifteen healthy good sleepers with a mean age of 30.8 years participated in this study. A randomized crossover trial was carried out using two different mattress types: a standard mattress and a contour coil mattress. After a night of adaptation, all participants were randomized to either a standard mattress or a contour coil mattress. Then, nocturnal polysomnography was conducted for two consecutive nights. Subjective evaluations were obtained using a self-report questionnaire before and after the polysomnographic recording sessions. Results: The polysomnographic showed no differences in total sleep time, sleep stage, or wake time after sleep onset between the two mattress conditions. Of the polysomnographic variables, only sleep onset latency was significantly reduced for the contour coil mattress. Additionally, participants reported better subjective sleep quality when sleeping on the contour coil mattress, according to the questionnaires. Conclusion: The type of mattress might affect not only subjective, but also objective sleep quality, including sleep onset latency.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.10
• /
• pp.4467-4474
• /
• 2011

The purpose of this study was to examine the factor of the quality of elderly women's sleep. The subjects in this study were 198 elderly women who were at the age of 60 and up. One instrument used to assess their quality of sleep was Buysse, et. al.(1989)'s Pittsburgh Sleep Quality Index(PSQI), and the other used to check their urinary incontinence was Jackson, et. al.(1996)'s Urination Symptom Inventory. The collected data were analyzed by the statistical package SPSS 18.0. The elderly women got $7.09{\pm}4.29$ in the quality of sleep of the PSQI, and 67.7 percent suffered from sleep disorders. Among the subfactors of the PSQI, their subjective quality of sleep was low, and the quality of sleep during, sleep latency was low as well. And their sleep disturbance was great. In contrast, the effectiveness of their habitual sleep was relatively good, and they didn't take medicine such as a sleep pill a lot, and their functional sleep disorder in the daytime wasn't great. There were differences in the quality of sleep according to their education, financial state, self-rated health status and family relations, and whether they worked out on a regular basis or not made a difference to that as well. No differences were found according to age, religion, occupation and having a coffee or not. There was a positive correlation between their quality of sleep in the PSQI and urinary incontinence(r=.51, p=.000). Out of the subfactors of the PSQI, the sleep disturbance factor was most closely linked to urinary incontinence(r=.465, p=.001). Finally, urinary incontinence and subjective health status were identified as the variables that exerted a statistically significant influence on the quality of sleep. Those variables made a 31% prediction of it.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2004.05b
• /
• pp.381-385
• /
• 2004

본 인구에서는 레이놀즈응력모형을 이용하여 직사각형 개수로 흐름을 수치모의 하고 이차흐름의 생성 메커니즘을 제시하였다. 수치모의 결과 자유수면과 측벽의 접합부 근처에서 inner secondary flow가 발생하였다. 이는 최근 Grega 등(1995)과 Hsu 등(2000)에 의해 밝혀진 새로운 이차흐름이다. 또한 측벽에서의 전단력 분포를 계산한 결과 inner secondary flow에 의하여 수면 근처에서의 전단력 값이 증가하는 것으로 나타났다. 계산된 결과를 이용하여 와도 방정식에서 각 항의 크기를 비교하여 이차 흐름의 생성 메커니즘을 살펴보았다. 그 결과 벽 및 측벽 경계 부근에서는 난류의 비등방성에 의한 와도 생성항에 의해 이차 흐름이 생성되고, 경계와 멀리 떨어진 영역에서는 레이놀즈응력에 의한 와도 생성항이 이차흐름을 생성시키는데 중요한 역할을 하는 것으로 나타났다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2011.06a
• /
• pp.55-57
• /
• 2011

경인 아라뱃길이 2011년 10월 개장을 앞두고 있다. 경인 아라뱃길이 시작되는 경인항 서해갑문 입출거시 예선사용기준에 대한 연구는 선박운항의 경제성 측면에서 매우 중요한 의미를 지닌다고 할 수 있다. 통상 선박의 크기(톤수)에 따른 예선의 소요마력 및 사용 척수는 대상선박의 크기, 모양, 접근수로, 부두시설의 위치 및 종류, 기타 환경조건 등의 영향을 받으며, 선체에 작용하는 수면상부의 풍압력과 수면하부의 유압력을 고려하여 규정하고 있다. 따라서 본 연구에서는 국내외 예선 규정 및 대상선박에 대한 예선 조종시뮬레이션을 통하여 경인항 서해갑문 입출거시 사용되는 예선의 기준을 설정하였다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.5
• /
• pp.451-458
• /
• 2018

This study was conducted to determine the association between quality of sleep (QOL) and the general characteristics, the health-behavioral factors, and the occupational characteristics of firefighting officers. The survey was conducted in October 2016 with a self-administered questionnaire using the Pittsburgh Sleep Quality Index (PSQI) developed by Pittsburgh University, targeting 600 male firefighting officers working at five fire stations in D city. As a result, the QOL of the study subjects measured by the PSQI revealed 13.2% to be good, and 86.8% to be poor. In relation to general characteristics and health habits, the rate of the group who had poor quality sleep was significantly higher in those with a lower subjective health status, in the non-smoking group, and in the low sleep-quality group, compared to the good sleep-quality group. For occupational characteristics, the rate of those with poor quality sleep was significantly higher in groups such as the fire suppression group, the shift work group, the hard physical labor group, the group with a lower sense of satisfaction in their work, and in the group classed as unfit for the job but who were not considering quitting their jobs, compared to their respective counterparts. Multiple regression analysis revealed factors of influence with explanatory powers of 24.4% for subjective health status, alcohol use, subjective quality of sleep, career, job position, and physical labor. The results of this study suggest that the quality of sleep for firefighting officers is significantly related to general characteristics, health-behavioral characteristics, and occupational characteristics.

• Sleep Medicine and Psychophysiology
• /
• v.12 no.1
• /
• pp.58-63
• /
• 2005

Objectives: REM sleep behavior disorder (RBD), characterized by excessive motor activity during REM sleep, is associated with loss of muscle atonia. In recent years, it has been reported that RBD has high co-morbidity with CNS disorders (especially, Parkinson's disease, dementia, multiple system atrophy, etc.). We aimed to assess differences in clinical and polysomnographic findings among RBD patients, depending on the presence or absence of central nervous system (CNS) disorders. Methods: The medical records and polysomnographic data of 81 patients who had been diagnosed as having RBD were reviewed. The patients were classified into two groups: associated RBD (aRBD, i.e., with a clinical history and/or brain MRI evidence of CNS disorder) and idiopathic RBD (iRBD, i.e., without a clinical history and/or brain MRI evidence of CNS disorder) groups. Twenty-one patients (25.9%) belonged to the aRBD group and 60 patients (74.1%) belonged to the iRBD group. The clinical characteristics and polysomnographic findings of the two groups were compared. Results: Periodic limb movement disorder (PLMD), i.e., PLMI (periodic limb movement index)>5, was observed more frequently in the aRBD group than in the iRBD group (p<0.001, Fisher's exact test). Also, obstructive sleep apnea syndrome (OSAS), i.e., RDI (respiratory disturbance index)>5, was found more frequently in the aRBD group (p=0.0042, Fisher's exact test). The percentages for slow wave sleep and sleep efficiency were significantly lower in the aRBD group than in the iRBD group. Conclusion: We found that 1 out of 4 RBD patients had associated CNS disorders, warranting more careful neurological evaluation and follow-up in this category of RBD. In this category of RBD patients, we also found more frequent PLMD and OSAS. These patients were also found to have lower slow wave sleep and sleep efficiency. In summary, RBD patients with associated CNS disorders suffer from more disturbed sleep than those without them.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2001.05a
• /
• pp.53-54
• /
• 2001

제주도 연근해에서는 소형선박으로 수동식 채낚기 어구와 선상 집어등으로 갈치를 유집하여 어획하고 있다. 총톤수 10톤의 갈치 채낚기 어선에는 6명의 선원, 수입산 냉동미끼, 대출력의 선상 집어등 등 조업경비의 지출이 심하여 조업선원의 감소를 할 수 있는 연속식 채낚기 어구 개발, 대출력 선상 집어등을 소출력의 수면 집어등, 어육미끼를 인공미끼로 대체하는 것이 절실하게 요구되고 있다. (중략)

• Sleep Medicine and Psychophysiology
• /
• v.5 no.1
• /
• pp.71-79
• /
• 1998

Objectives : This study was to evaluate sleep patterns and daytime sleepiness resulting from rotating shiftwork. The authors, also, tried to find out the relationship between the severity of daytime sleepiness and personality factors. Methods : The subjects consisted of 41 female rotating shiftwork nurses and the control group consisted of 39 female day timeworkers. All of them completed the Sleep questionnaire of Korea University Sleep Disorder Clinic, the Epworth Sleepiness Scale(ESS), the 16 Personality Factors(16PF), the Beck Depression Inventory(BDI) and the State Trait Anxiety Inventory(STAI). Multiple regression analysis of 16PF of the rotating shiftwork nurses was done to find out possible predictors of the severity of daytime sleepiness. Results : The mean duration of deprived sleep due to rotating shiftwork was $64.26\;{\pm}\;14.54\;min$. The frequency of sleep difficulty($1.24\;{\pm}\;1.17\;day/week$ vs $0.67\;{\pm}\;1.31\;day/week$, p < 0.05), time needed to fall asleep($103.05\;{\pm}\;73.48\;min$. vs $70.00\;{\pm}\;60.08\;min$, p < 0.05), sleep duration when having some difficulties in sleep ($204.25\;{\pm}\;79.90\;min$. vs $280.44\;{\pm}\;111.59\;min$., p < 0.001), recent changes in energy($x^2\;=\;4.16$, p < 0.05), worrying about sleep($x^2\;=\;11.08$, p < 0.05), and taking naps($x^2\;=\;4.98$, p < 0.05) showed significant differences between rotating shiftworkers and normal controls. The ESS socre of shiftworkers ($8.68\;{\pm}\;3.04$) was greater than that of normal controls ($6.86\;{\pm}\;3.04$)(p < 0.01). Personality factors such as C factor($R^2\;=0.283$), I factor($R^2\;=0.358$) and G factor($R^2\;=0.470$) were related with the severity of the daytime sleepiness(p < 0.001). Conclusions : The rotating shiftwork nurses had more difficulties in sleep such as having difficulties in falling asleep and in maintaining sleep, and showed lowered energy, decreased senses of well-being and so on. The rotating shiftwork nurses experienced more severe daytime sleepiness than controls did. Personality factors, such as C factor, I factor, and G factor of 16PF were suggested to be useful for predicting the severity of daytime sleepiness resulting from rotating shiftwork.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.10
• /
• pp.207-216
• /
• 2013

The aim of this study is to design a classifier for sleep stage analysis and select important feature set which shows sleep stage well based on physiological signals during sleep. Sleep has a significant effect on the quality of human life. When people undergo lack of sleep or sleep-related disease, they are likely to reduced concentration and cognitive impairment affects, etc. Therefore, there are a lot of research to analyze sleep stage. In this study, after acquisition physiological signals during sleep, we do pre-processing such as filtering for extracting features. The features are used input for the new combination algorithm using genetic algorithm(GA) and neural networks(NN). The algorithm selects features which have high weights to classify sleep stage. As the result of this study, accuracy of the algorithm is up to 90.26% with electroencephalography(EEG) signal and electrocardiography(ECG) signal, and selecting features are alpha and delta frequency band power of EEG signal and standard deviation of all normal RR intervals(SDNN) of ECG signal. We checked the selected features are well shown that they have important information to classify sleep stage as doing repeating the algorithm. This research could use for not only diagnose disease related to sleep but also make a guideline of sleep stage analysis.