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This study examined the aerodynamic power output change of wind turbines with inter-turbine spacing variation for a 6 MW wind farm composed of three sets of 2 MW wind turbines using computational fluid dynamics (CFD). The wind farm layout design is becoming increasingly important as the use of wind energy is steadily increasing. Among the many wind farm layout design parameters, the inter-turbine spacing is a key factor in the initial investment cost, annual energy production and maintenance cost. The inter-turbine spacing should be determined to maximize the annual energy production and minimize the wake effect, turbulence effect and fatigue load during the service lifetime of wind turbines. Therefore, some compromise between the aerodynamic power output of wind turbines and the inter-turbine spacing is needed. An actuator disc model with the addition of a momentum source was not used, and instead, a full 3-dimensional model with a tower and nacelle was used for CFD analysis because of its great technical significance. The CFD analysis results, such as the aerodynamic power output, axial direction wind speed change, pressure drop across the rotor of wind turbine, and wind speed deficit due to the wake effect with inter-turbine spacing variation, were studied. The results of this study can be applied effectively to wind farm layout design and evaluation. more...

Background and Objective The aim of this study is to compare the clinical, electrophysiological (Polysomnography, PSG; Multiple Sleep Latency Test, MSLT) and biological data (HLA DQB1*0602 typing) in idiopathic hypersomnia with narcolepsy without cataplexy. Methods 80 patients with narcolepsy without cataplexy and 71 patients with idiopathic hypersomnia without a long sleep time were recruited at the Sleep Center of St. Vincent’s Hospital. MSLT data and PSG findings from the time of their diagnosis were reviewed. HLA typing was performed. Results Results indicated that the idiopathic hypersomnia group showed a significant longer mean sleep latency in MSLT compared with the narcolepsy without cataplexy group. But there was no significant difference in the Epworth Sleepiness Scale (ESS) scores between the two groups. Although HLA positivity of both groups was not statistically significant (p = 0.065), HLA positivity tended to be higher in the narcolepsy without cataplexy group than the idiopathic hypersomnia group. The number of awakenings was slightly higher in the idiopathic hypersomnia group, but there was no statistical significance. The number of spontaneous arousal and total arousal indices was not significantly different between the groups. For the PSG, the idiopathic hypersomnia group showed a significantly longer sleep latency than the narcolepsy without cataplexy group (p = 0.009). REM sleep latency (REML) was significantly shorter in the narcolepsy without cataplexy group compared to the idiopathic hypersomnia group. The percentage of REM (SREM) was significantly higher in the narcolepsy without cataplexy group, and the percentage of the wake time during sleep period (SWT) was significantly lower in the narcolepsy without cataplexy group. Conclusions There were no significant differences of subjective sleep measures such as ESS, disturbed nocturnal sleep, number of naps, age of onset of hypnagogic hallucination, and age of onset of sleep paralysis between patients with narcolepsy without cataplexy and idiopathic hypersomnia. So, the use of objective tests such as the PSG and MSLT may be inevitable for the differential diagnosis of narcolepsy without cataplexy from idiopathic hypersomnia. more...

Background and Objective A diagnosis of narcolepsy is defined by less than 8 minutes of mean sleep latency, and two or more sleep onset rapid eye movement periods on the Multiple Sleep Latency Test. This study examined the relationship between the sleep onset rapid eye movement period frequencies during Multiple Sleep Latency Test and narcoleptic symptom severity. Methods From March 2004 to August 2009, 126 patients suffering from excessive daytime sleepiness who visited the Sleep Disorders Clinic of St. Vincent’s Hospital at the Catholic University of Korea were tested by polysomnography and Multiple Sleep Latency Test. Subjects were divided into three groups according to the number of sleep onset rapid eye movement periods that appeared on the Multiple Sleep Latency Test. Symptom severity instruments included the Epworth Sleepiness Scale and the Stanford Center for Narcolepsy Sleep Inventory, and various sleep parameters. In addition, we performed human leukocyte antigen genotyping for human leukocyte antigen-DQB1*0602 on all patients. Results Among the three groups classified by the number of sleep onset rapid eye movement periods during Multiple Sleep Latency Test, we found no significant differences in demographic features, Epworth Sleepiness Scale, and most polysomnographic findings. However, we observed cataplexy, hypnagogic hallucination, sleep paralysis, and human leukocyte antigen-DQB1*0602 positivity more frequently in groups with higher sleep onset rapid eye movement period frequencies. In addition, the proportions of stage II sleep, REM sleep latency from polysomnography, and mean sleep latency and mean REM sleep latency from the Multiple Sleep Latency Test significantly decreased with increasing sleep onset rapid eye movement period frequency. Conclusions In this study, we demonstrated that sleep onset rapid eye movement period frequency during Multiple Sleep Latency Test correlated with sleep architecture, daytime symptom severity, and frequency of human leukocyte antigen-DQB1*0602 positivity in narcolepsy. Further studies are needed to explore the pathophysiology of narcolepsy associated with sleep onset rapid eye movement periods. more...