• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제33권7호
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• pp.9-17
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• 2005

The wake patterns and thrust characteristics of dual flapping airfoils in a biplane configuration are investigated using an unsteady panel method. To trace complicated wake shapes behind airfoils, a core addition scheme, a vortex core model, and the fourth order Runge-Kutta convection scheme are employed. Present results are verified by comparing them with flow visualization, exact solution and published computed results. The thickness and camber of thick airfoils has an effect of decreasing thrust. The airfoils produce maximum thrust when the phase angles between plunging and pitching motions are both 90 and 120 degrees. Thrust increases as the plunge velocity is increased, which is also found as the pitch amplitude is stepped up. Thrust decreases when the distance between the airfoils is less than 0.6c.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제17권5호
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• pp.404-409
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• 2005

This study is to investigate effects of thermal conditions on sleep. Five female university students participated in the sleep experiment. Three temperature levels (22, 26, and $30^{\circ}C$) were given, and relative humidity was maintained to $50\%$. When as subject arrived in the chamber at 9 o'clock in the evening, questionnaire was given to check physical and psychological conditions. After checking conditions, subjects went to bed till 07 : 30 in the morning. Body movement was checked during sleeping. After sleep in the chamber, questionnaire was given to the subject in order to check sleep quality. Subjects evaluated sleep quality by themselves by answering the time they fall asleep and wake up, frequency of wake during sleep, causes of each waking, and feeling after sleep. Sleep quality was rated with 7-point scale. At $30^{\circ}C$ condition, body movement was significantly higher than of other thermal conditions. The best sleep quality was obtained at the $26^{\circ}C$ condition, while the worst sleep was taken at the $30^{\circ}C$ condition.

• Wind and Structures
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• 제15권4호
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• pp.313-329
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• 2012

There have existed for a number of years good practice guidelines for the use of Computational Fluid Dynamics (CFD) in the field of wind engineering. As part of those guidelines, details are given for the size of flow domain that should be used around a building of height, H. For low-rise buildings, the domain sizes produced by following the guidelines are reasonable and produce results that are largely free from blockage effects. However, when high-rise or tall buildings are considered, the domain size based solely on the building height produces very large domains. A large domain, in most cases, leads to a large cell count, with many of the cells in the grid being used up in regions far from the building/wake region. This paper challenges this domain size guidance by looking at the effects of changing the domain size around a tall building. The RNG ${\kappa}-{\varepsilon}$ turbulence model is used in a series of steady-state solutions where the only parameter varied is the domain size, with the mesh resolution in the building/wake region left unchanged. Comparisons between the velocity fields in the near-field of the building and pressure coefficients on the building are used to inform the assessment. The findings of the work for this case suggest that a domain of approximately 10% the volume of that suggested by the existing guidelines could be used with a loss in accuracy of less than 10%.

• The Journal of Economics, Marketing and Management
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• 제5권2호
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• pp.33-39
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• 2017

As the aging population geworsened by the a of the low fertility rate in the wake of the birth of the low birth rate, the rapid increase in the retirement age of the baby boomers in the wake of the birth of the Korean War is a significant indication of the separation of the aged and the role of the economically rich and the role of the role of the economically rich. Therefore, this study aims to address issues and countermeasures. The study aims to provide basic data for the future life of the baby boom generation by examining the problems and responses to the economic activity after the retirement activity of the baby boomers. The research suggests that the limit was limited to the retirement age of the baby boomer generation in order to boost the employment of the elderly. Due to the lack of exploration of the exploratory research, the lack of analysis of exploratory facts is the biggest limitation of the analysis. So, further analysis of this will lead to meaningful studies. Looking at the composition of this study, the introduction of the study included the necessity and purpose of the study. The focus on the point was on the concepts and characteristics of the baby boomer, and analyzed the characteristics of the economic activity and analyses and analyses of domestic and international cases. In conclusion, the issue was drawn up and the alternatives were sought.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제49권2호
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• pp.23-30
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• 2012

This paper proposes a novel adaptive header-based power gating structure to compensate for the performance loss and the increased wake-up time of the power gating structures induced by the negative bias temperature instability (NBTI) effect. The proposed structure consists of variable width footers based on the two-pass power gating and a new NBTI sensing circuit for an adaptive control. The simulation results of the proposed structure are compared to those of power gating without the adaptive control and show that both the circuit-delay and wake-up time dependence of the power gating structure on the NBTI stress is minimized with only 3% and 4% increase, respectively while keeping small leakage power and rush-current. In this paper, a 45 nm CMOS technology and predictive NBTI model have been used to implement the proposed circuits.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제44권11호
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• pp.51-55
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• 2007

Generally, PLC (Power Line Communication) based home automation devices such as wall switch, walt socket, gas controller, etc, must maintain wake-up status at all time to control other electronic devices and monitor their on/off status whether they are in service or not. In order to reduce the unnecessary energy consumption during the standby mode, the new power-saving PLC 2 ports wall switch has been developed, separating PLC communication part and controller part and introducing sleep mode. In addition, to expand life cycle of PLC product and to reduce the rate of product failure in active mode, the instant controlling method in controlling process is adopted instead of the maintenance controlling method. In comparison to the earlier model, the new 2 ports PLC wall switch has reduced power by 0.95[W] less in standby mode and 3.2[W] less in active mode than the previous one.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• 제20권3호
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• pp.146-151
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• 2009

Objectives : We conducted this study to investigate the relationship between sleep duration and body mass index (BMI), in Korean children. Methods : We performed a cross-sectional analysis of data collected on 3,639 boys and girls (aged 7-12) in Daegu, Korea. The data included each child's age, sex, weight, height, extracurricular activities, bedtime, wake-up time, sleep latency, total sleep duration, parents' occupations, and parents' educational levels. The relationship between sleep duration and each variable was examined via analysis of variance (ANOVA). Results : The analysis showed an association between short sleep duration and high BMI. Boys showed a graded inverse relationship between sleep duration and BMI. However, there was no significant corresponding result for girls. In the total sample, hours of computer use, time when the computer was turned off, time when the television was turned off, mother's bedtime, and hours of extracurricular activity were associated with longer sleep duration. No association was found between sleep duration and hours of watching television, child's wake-up time, or educational level of the parents. Conclusion : The results of this study show an inverse relationship between a child's sleep duration and BMI；thus, children with shorter sleep duration tend to have higher BMIs.

• Journal of Korea Multimedia Society
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• 제10권3호
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• pp.348-357
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• 2007

One of the major issues in recent researches on wireless sensor networks is to reduce energy consumption of sensor nodes operating with limited battery power, in order to lengthen their lifespan. Among the researches, we are interested in the schemes in which a sensor node periodically turns on and off its radio and requires information on the time when its neighbors will wake up (or turn on). Clock synchronization is essential for wakeup scheduling in such schemes. This paper proposes three methods based on the asynchronous averaging algorithm for clock synchronization in sensor nodes which periodically wake up: (1) a fast clock synchronization method during an initial network construction period, (2) a periodic clock synchronization method for saving energy consumption, and (3) a decision method for switching the operation mode of sensor nodes between the two clock synchronization methods. Through simulation, we analyze maximum clock difference and the number of messages required for clock synchronization.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.164-165
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• 2015

Modular construction technique is an adaptation of factory-based mass production concept in ordinary manufacturing industries to construction industry and it assumes that panels, units, etc. are fabricated in factories and assembled in construction sites. Given its structural limitations, modular construction technique is primarily used in low-story buildings whose maximum height is usually five stories, but researchers are actively studying possible adaptation of modular construction technique to high-rise building designs these days as in the case of infill-type modular construction design. Infill-type modular construction technique, most frequently used in high-rise building construction projects, completes frame construction first in reinforced concrete structures and fills unit modules in such structures. However, infill-type modular construction technique leads to longer construction schedule accompanying increase in construction cost, cost overrun due to additional of temporary work, and possible damage to units in the wake of facility construction. Accordingly, this study is performed as a basic study for the development of bottom-up infill-type modular construction technique intended to construct structural frames and fill in units sequentially in a bid to address such drawbacks of current infill-type modular construction technique.

• Journal of computational fluids engineering
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• 제15권3호
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• pp.39-45
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• 2010

The turbulent flows in a tunnel mock-up($10L{\times}0.5W{\times}0.25H$ m3 : scale reduction 1/20) with rectangular cross section were investigated. The instantaneous velocity fields of Re = 49,029, 89,571 were measured by the 2-D PIV system which is consisted of double pulsed Nd:Yag laser and the tracer particles in the straight-duct mock-up where the flows were fully developed. The mean velocity profiles were taken from the ensemble averages of 1,000 instantaneous velocity fields. Simultaneously, numerical simulations(RANS) were performed to compare with experimental data using STREAM code. Non-linear eddy viscosity model (NLEVM : Abe-Jang-Leschziner Eddy Viscosity Model) was employed to resolve the turbulent flows in the duct. The calculated mean velocity profiles were well compared with PIV results. In the log-law profiles, the experimental data were in good agreement with numerical simulations all the way to the wake region except the viscous sub-layer (near wall region).