• Sleep Medicine and Psychophysiology
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• v.25 no.2
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• pp.51-57
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• 2018

Objectives: Previous studies have shown that periodic limb movements in sleep (PLMS) could be one of risk factors for cardiovascular morbidity. The purpose of this study was to investigate the association between PLMS and blood pressure changes during sleep. Methods: We analyzed data from 358 adults (176 men and 182 women) aged 18 years and older who were free from sleep apnea syndrome (Respiratory Disturbance Index < 5) and sleep disorders such as REM sleep behavior disorder or narcolepsy. Demographic characteristics, polysomnography records, and clinical variable data including blood pressure, body mass index, alcohol, smoking, and current medications were collected. In addition, self-report questionnaires including the Beck Depression Index, Epworth Sleepiness Scale and Pittsburgh Sleep Quality Index were completed. Blood pressure change from bedtime to awakening was compared between the two periodic limb movement index (PLMI) groups [low PLMI ($PLMI{\leq}15$) and high PLMI (PLMI > 15)]. Blood pressure change patterns were compared using repeated measures analysis of variance. Results: Systolic blood pressure in the high PLMI group was lower than that in the low PLMI group (p = 0.036). These results were also significant when adjusted for gender and age, but were not statistically significant when adjusted for BMI, alcohol, smoking, anti-hypertension medication use and sleep efficiency (p = 0.098). Systolic blood pressure dropped by 9.7 mm Hg in the low PLMI group, and systolic blood pressure in the high PLMI group dropped by 2.9 mm Hg. There was a significant difference in delta systolic blood pressure after sleep between the two groups in women when adjusted for age, BMI, alcohol, smoking, antihypertensive medication use and sleep efficiency (p = 0.023). Conclusion: PLMS was significantly associated with a decreasing pattern in nocturnal BP during sleep, and this association remained significant in women when adjusted for age, BMI, alcohol, smoking, antihypertension medication use and sleep efficiency related to blood pressure. We suggest that PLMS may be associated with cardiovascular morbidity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.466-473
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• 2010

Several protocols which are based on tree topology to guarantee the important metrics such as energy efficiency in sensor networks have been proposed. However, studies on the effect of topologies in sensor networks, where base node has a high mobility, are very few. In this paper, we propose a minimum Wiener index tree as a suitable topology to the wireless sensor networks with high mobile base node. The minimum Wiener index spanning tree problem which aims to find a tree with minimum Wiener index from a given weighted graph was proved to be NP-hard. We designed a branch and bound algorithm for this problem. To evaluate the performance of proposed tree, the comparisons with minimum spanning tree in terms of transmission distance, energy consumption during one round, and network lifetime was performed by simulations. Our proposed tree outperformed in transmission distance and energy efficiency but underperformed in lifetime.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.784-791
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• 2013

Recent advanced IT made layout design fast and accurate by using algorithms. Layout design should be determined by considering the position of equipment with satisfying various space constraints and its component works with optimum performance. Especially, engine room layout design is performed with mother ship data, theoretical optimal solution, design requirements and several design constraints in initial design stage. Piping design is affected by position of equipment seriously. Piping design depends on experience of designer. And also piping designer should consider correlation of equipment and efficiency of space. In this study, space evaluation method has been used to evaluate efficiency of space. And also this study suggested object function for optimal piping route, Average Reservation Index(ARI), Estimated Piping Productivity(EPP) and with modified space evaluation method. In this study, optimum pipe routing system has been developed to reflect automated piping route with space efficiency and experience of piping designer. Engine room is applied to the design of the piping in order to confirm validity of the developed system.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.9
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• pp.1-8
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• 2022

This paper studies market efficiency from a weak form aspect using opening and closing prices of the Shanghai stock exchange composite index (SSEC) and Shenzhen stock exchange composite index (SZSEC) under the expected return theory. Classical methods (autocorrelation and runs test) are used to examine the features of stock returns, and little evidence against mutual independence of returns is found. We predict daily returns of SSEC and SZSEC with AR(p) and VAR(p) models (in this paper, p = 5 is taken as a one-week lag) and perform a virtual experiment on two indexes based on the predicted value of daily returns from AR(p) or VAR(p) model. From the results of AR(p) and VAR(p) for two indexes, we attempt to find out how the market efficiency level changes when the information from the other market is under consideration as we check the market efficiency level in one market. We find that SSEC in 2014-2016 and SZSEC in 2015-2016 are inefficient from the result of autocorrelation, that SSEC in 2016 and SZSEC in 2013 are not efficient from the result of runs test, that the stock market is efficient except 2005, 2009, 2010 and 2017 in SSEC and 2005, 2016 and 2017 in SZSEC and that SSEC is more influenced by SZSEC but SSEC influences SZSEC less from the result of the virtual experiment.

• Proceedings of the Korean Society of Potoscience Conference
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• spring
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• pp.41-41
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• 1997

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.75.1-75.1
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• 2010

Dye sensitized solar cells(DSSCs) have been extensively studied due to their various advantages such as low production cost, colorful design, and eco-friendly process. Long optical path length is one of the most effective method to improve light harvest efficiency for DSSCs. Multi-layered $TiO_2$ nano-structured film with scattering layer has been studied to generate scattering effect by many researchers. It was expected that the difference of refractive index between $TiO_2$ particles and glass frit would generate the light scattering effect and provide the long optical path length. Therefore, to enhance the scattering effect, the frits of $Bi_2O_3-B_2O_3$-ZnO glass system that has the different refractive index were added to $TiO_2$ pastes in this study. First of all, the absorbance and haze factor of $TiO_2$ electrode with dyes and the refractive index of glass frit and $TiO_2$ were measured, respectively. To study the effect of frits, the efficiencies of DSSCs added glass frit and without glass frit were compared. Our results showed slightly higher efficiency with the different absorbance and haze factor of $TiO_2$ and glass frit. It was considered that the light scattering effect would be improved with adding frits to $TiO_2$ paste. Our preliminary studies will be useful for increasing efficiency of DSSCs.

• The Journal of the Korea Contents Association
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• v.10 no.10
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• pp.456-463
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• 2010

This study measured the relative efficiency and productivity change of the Korean professional sport teams using DEA model and Malmquist Index for 2006-2009. The main results of this study can be summarized as follows. First, in case of efficiency of CCR for 2006-2009, the number of efficient professional sport teams(CCR value is one) are two(Daejeon Citizen, Incheon United), three(Daejeon Citizen, Incheon United, FC Seoul), two(Daejeon Citizen, Incheon United), three(Kyungnam FC, Incheon United, FC Seoul) respectively. Second, Malmquist Index representing productivity change for 2006-2009 are 1.035, 0.9658, 1.5331 for Kyungnam FC, 1.2514, 0.8948, 0.9056 for Daegu FC, 1.1768, 0.8620, 0.9722 for Daejeon Citizen, 0.9368, 1.2609, 0.7714 for Incheon United, 1.0000, 1.0000, 1.0000 for FC Seoul, respectively. This result will be used by inefficient professional sport teams to improve inefficiency.

• Journal of Technology Innovation
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• v.21 no.3
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• pp.41-72
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• 2013

In this study, a comparison has been made among the countries regarding recent ICT practices being performed based on the measures of relative efficiency and productivity growth that use multiple inputs and outputs. Efficiency measures a country's ICT performance relative to a benchmark at a given point of time and productivity measures a country's performance over a period of time. An output-oriented Data Envelopment Analysis and Malmquist Index has been used for comparison among 28 countries over the period 2008-2011 by incorporating 9 variables. The empirical findings disclose gross inefficiencies in national ICT practices, which show that there is room for enhancing output gains through increased efficiency in their operations. In addition, 13 countries have performed better than others in total factor productivity mainly because of their improvement in the underlying technological progress in ICT. For those technically inefficient countries, however, technical inefficiency may hamper the growth of total factor productivity of ICT practices.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.272-277
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• 2012

KORAIL's logistics business coefficient is improved slightly from 197.4 in 2009 to 190.7 in 2010 but the cost is still high compared to the revenues. In order to derive activities for the efficient logistics and measure their effects quantitatively, the analysis of various indexes that can be extracted from the statistical data is very important. In this study, the various indexes are analyzed to evaluate the efficiency of freight cars based on railway logistics. It can be used to estimate the various activities for the efficient logistics associated with freight cars. We suggest the Indexes as the number of transport, cumulative transport distance and transport income to evaluate the efficiency of freight cars and they should be applied according to the characteristics of each index.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.7
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• pp.515-522
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• 2018

An orthogonal frequency division multiplexing with coded direct index modulation(OFDM-CDIM) system that can achieve higher performance and spectral efficiency than previous OFDM systems is proposed. Previous OFDM with index modulation(IM) and OFDM-IM using dual modes systems allocate additional data to indices of respective subcarriers through combining operation with high complexity and then transmit them. However, the proposed system directly allocates the mode selection information to each subcarrier without performing additional operations. Then, the system selects and transmits one symbol in the selected mode. Furthermore, only the data allocated to the index of the subcarrier is encoded, and a good performance improvement effect is obtained with a high code rate. Simulation results show quantitatively that an OFDM-CDIM system using four modes improves bit error rate performance and transmission efficiency in additive white Gaussian noise and Rayleigh fading channel environments compared with a conventional OFDM system using 4-ary quadrature amplitude modulation.