• Magazine of the Korean Society of Agricultural Engineers
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• v.52 no.2
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• pp.32-44
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• 2010

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.121-122
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• 2011

본 논문에서는 무선 협력 네트워크(wireless cooperative network)의 전송 신뢰성과 공정성 향상을 위한 비례공정 중계(proportional-fair relaying) 기법을 제안한다. 다중 단말과 단일 기지국이 있는 다원 접속(multiple access) 환경에서 저속 페이딩(slow fading)에 의한 성능 열화를 저감하면서 단말간 자원 사용 공정성 보장하기 위해 비례공정 전송 기법과 중계 기법 결합한다. 이를 통해 기존 기회적(opportunistic) 전송 기법의 비대칭 채널(asymmetric channel)에서의 자원 사용 불공정성을 해결하면서 깊은 페이딩(deep fading)에 의한 데이터 무선 전송 손실을 최소화 한다. 컴퓨터 모의실험 결과를 통해 제안된 기법이 공정성 제한(fairness constraint)이 있는 다원 접속 환경에서 불능 확률(outage probability) 성능을 제고함을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.3B
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• pp.375-382
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• 2001

동북아시아 지역은 21세기, 정보화 시대를 맞이하여, 정보 기술, 정보산업 위주의 경제 개발을 추진함으로 해서, 세계 경제의 중심부로 부상될 수 있을 것이다. 이를 위해서는 동북아시아 지역을 종합적으로 연결하는 지역 정보통신 네트워크의 구성이 필요하다. 동북아시아 지역이 세계 경제의 중심으로 자리잡기 위하여 동북아의 초고속 정보통신 인프라 구축을 위한 방안을 대내외적 연건에 대한 객관적인 면과 전망에 근거하여 실혐 가능한 통신망 구축 전략을 제시하였다. 동북아시아의 통신망 구축을 위해서는 다원성, 경제성, 중계성 등을 고려하여 망을 구축하여야 하며, 기존의 망포설 현황, 현재 통신의 사용량 및 향후 발전 전망 등을 검토하여 한반도를 동북아시아 통신 허브국으로 선정하고, 그에 따른 망의 구성, 구축방안을 기술하였다.

• Sleep Medicine and Psychophysiology
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• v.12 no.1
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• pp.32-38
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• 2005

Objectives: Obstructive sleep apnea syndrome (OSAS) has drawn increasing attention as medical community has become to be aware of its co-morbidities and complications, especially cardiovascular complications and excessive daytime sleepiness with accident proneness. As of now, polysomnography is the standard tool to diagnose sleep apnea and estimate the treatment validity. However, its being rather expensive and inconvenient, alternate diagnostic tools have been proposed including wrist actigraphy. So far, actigraphies have been adopted usefully to field-survey sleep apnea prevalence. In this study, we attempted in a sleep laboratory setting to assess the supplemental value of actigraphy in diagnosing OSAS. Methods: This study was done at the Division of Sleep Studies, the Seoul National University Hospital. Thirty-seven clinically suspected cases of OSAS underwent the one-night polysomnography, simultaneously wearing an actigraphy on non-dominant wrist. We analyzed the data of 27 polysomnographically-proven OSAS patients (male：female 20： 7；age $47.6{\pm}12.9$ years old；age range 23 to 72 years) with no other sleep disorders. We calculated RDI (respiratory disturbance index) from the polysomnography data and FI (fragmentation index) from the actigraphy data. Pearson correlation was calculated in order to compare FI with RDI and to evaluate the supplemental diagnostic value of the actigraphy. Results: Mean total sleep time on polysomnography was $401.4{\pm}57.8\;min$ (range of 274.0 to 514.1 min). Mean RDI was $21.7{\pm}20.4/hour$. Mean FI was $21.9{\pm}13.0/hour$. RDI and FI showed significant correlation (r=0.55, p<0.01). Conclusions: Wrist actigraphy in OSAS patients generates a comparable outcome to polysomnography, in measuring the nocturnal sleep fragmentation. The actigraphy could be used supplementally in inpatients, outpatients, and field survey subjects, if polysomnography is unavailable or impossible. In follow-ups related with nasal CPAP (continuous positive airway pressure), upper airway surgery, and oral appliance in OSAS patients, the actigraphy might play a more dominant role in the future.

• Sleep Medicine and Psychophysiology
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• v.7 no.2
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• pp.102-108
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• 2000

Objectives: Parkinson's disease (PD) patients may experience fluent mobility upon awakening from a night's sleep, which is called sleep benefit (SB). Although SB is a phenomenon closely associated with sleep, sleep features of PD are not well characterized. The objectives of this study were, first, to investigate if there are any clinical characteristic features between patients with SB and without SB (NSB), and second, to examine if SB patients are associated with any specific sleep variables compared with NSB patients. Methods: Thirty-three PD patients (14 men and 19 women) participated in this study. All subjects were interviewed to examine whether or not they had SB and overnight polysomnography was performed at the sleep center. Various clinical variables were collected through medical record review. Results: The 331 PD patients were divided into 16 SB group (48.5%) and 17 NSB group (51.5%). SB patients were younger (p<0.02), had higher sleep efficiency (p<0.05), and showed shortened sleep latency (p<0.02) as compared with NSB patients. However, no difference was found between SB and NSB with respect to gender, duration or stage of PD, antiparkinsonian medications prescribed, and predominant motor symptoms. SB did not clearly relate to a specific sleep stage and other sleep variables except sleep efficiency and sleep latency. Although primary snoring was more prevalent in SB patients (p<0.05), other sleep disorders were seen with equal frequency in SB and NSB groups. Conclusion: Our results suggest that good sleep efficiency, shortened sleep latency, and age may have an effect on morning motor function (i.e., SB) in Parkinson's disease.

• Sleep Medicine and Psychophysiology
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• v.7 no.1
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• pp.43-50
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• 2000

Objectives: Obstructive sleep apnea syndrome(OSAS) is known to be associated with the changes of autonomic nervous system (ANS). Nasal continuous positive airway pressure(nCPAP) treatment was found to correct abnormal ANS changes in OSAS but it remains to be further clarified. We aimed to assess the effects of nCPAP on ANS manifested on electrocardiogram, using spectrum analysis in the subjects with OSAS. Methods: Digital polysomnography was performed in 18 patients with OSAS(mean age $43.7{\pm}16.6$ years ; 17 males, 1 female ; mean respiratory disturbance index (RDI) $48.6{\pm}20.9$) for one baseline and another CPAP nights. From each night, 300 continuous beats of ECGs without artifact were chosen from both stage 2 sleep and REM sleep and they were used for power spectrum analysis. We compared between baseline and CPAP nights the heart rate variability including VLF(very low frequency power), LF (low frequency power), HF(high frequency power), R-R means, R-R variance, and LF/HF ratio, using Wilcoxon signed ranks test. Results: In all patients, nCPAP proved to be effective in relieving apneas and snoring. During nCPAP night compared with baseline night, decreases in VLF(p<0.05), LF(p<0.01), and R-R variance(p<0.05) were found in stage 2 sleep, and decreased LF(p<0.05) was found in REM sleep. No significant differences in each sleep stage were found in other variables between the two nights. Conclusion: Our findings suggest that OSAS increases the activity of sympathetic nervous system and nCPAP application effectively decreases the activity. And nCPAP does not appear to influence the parasympathetic nervous activity in OSAS.

• Sleep Medicine and Psychophysiology
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• v.8 no.2
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• pp.113-120
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• 2001

Objectives: Obstructive sleep apnea syndrome is common and may produce various symptoms and serious complications. A substantial number of research articles on obstructive sleep apnea syndrome have been published in Korea. However, we found such limitations as lack of sufficient sample size and lack of polysomnography-proven cases. Therefore, we aimed at studying clinical features and sleep structure in a sufficient number of Korean patients with obstructive sleep apnea syndrome diagnostically confirmed with polysomnography. Methods: We studied 801 subjects referred to the Division of Sleep Studies, Seoul National University Hospital, who were diagnosed as having obstructive sleep apnea syndrome with polysomnography. Subjects were excluded if they had central sleep apnea syndrome, periodic limb movement disorder, narcolepsy or REM sleep behavior disorder. Foreign patients were also excluded. First of all, we studied the clinical features of the subjects. Secondly, we compared sleep-related parameters of the study subjects with those of age/sex-matched normal values. Thirdly, correlations of respiratory disturbance index (RDI) with each of the sleep-related parameters were calculated. Results: Among the 801 subjects, 668 were male subjects (83.4%) and 133 female subjects (16.4%). Their mean age was 46.6 years (${\pm}13.5$). The mean body mass index (BMI) was 25.8 (${\pm}3.8$) and subjects with BMI was over 28.0 accounted for 22.8% of the total. Fifty subjects (6.2%) were found to take benzodiazepines. Mean RDI and mean nocturnal oxygen saturation of all subjects was 31.2 (${\pm}24.4$) and 94.5% (${\pm}3.6$), respectively. In comparison with normal values, the subjects showed longer sleep latency, lower sleep efficiency, decreased total slow wave sleep % (TSWS %), and decreased total REM sleep % (TREM %)(p<0.01 in all). RDI had a negative correlation with each TSWS % and TREM % (p<0.01, p<0.01). However, RDI did not have significant correlation with either sleep latency or sleep efficiency. Conclusion: In this study, 6.2% of patients diagnosed as having obstructive sleep apnea syndrome were found to take benzodiazepines, although they are generally considered to be of litte benefit or even dangerous because of the respiratory suppressing effect. The proportion of obese subjects was only 22.8% and Korean patients with obstructive sleep apnea syndrome seem to be less obese than those described in foreign journals. This study also suggests that the severity of obstructive sleep apnea syndrome may have a more significant effect on sleep architecture defined as TSWS % and TREM % than on sleep efficiency.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1647-1656
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• 2007

With the growing international consensus regarding sustainable development of transportation, the plan of transportation infrastructure needs to meet various requirements toward enhancing environmental conditions. Accordingly, the upcoming long-term plan of high-speed rail network has to be reflecting the sustainability of transportation systems. In this paper, we propose methodologies based on multi-attribute utility theory for determining priorities of sustainable high-speed rail investment. The proposed methodologies identify indicators for sustainable transportation systems such as economic, environmental, social, and transportation-related ones and then, explain the way how to evaluate the overall sustainability by comparing the relative importance among indicators. This will help transportation agencies to prioritize high-speed rail investment toward sustainable transportation systems.

• Sleep Medicine and Psychophysiology
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• v.29 no.2
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• pp.35-39
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• 2022

REM sleep behavior disorder is parasomnia characterized by unpleasant dreams and dream-enactment behaviors associated with excessive electromyography activity in REM sleep. This may appear idiopathic or secondary to other neurological or medical conditions. REM sleep behavior disorder, which appears to be idiopathic, most often implies the possibility of later neurodegenerative diseases due to synucleinopathy, so accurate diagnosis is important in predicting prognosis. For the diagnosis of REM sleep behavioral disorder, REM sleep without atonia, which appears in the polysomnography, is essential. Obstructive sleep apnea, trauma-related sleep disorders, and vigorous periodic leg movements during sleep are known as diseases that show dream enactment behavior in elderly patients. Considering that it may be accompanied by other sleep disorders that can mimic REM sleep behavioral disorders, it is important to differentiate sleep

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.30 no.8
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• pp.45-53
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• 2001

열적 성질을 가지는 각종 용질을 물을 주체로 한 열매체 등에 혼합 분산시킴으로써 그 열매체인 유체의 성질을 바꾸어 다원적 기능성을 가지도록 한 기능성 열유체의 열에너지 수송성에 대해 살펴보고자 한다.