• Ocean and Polar Research
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• v.30 no.4
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• pp.537-543
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• 2008

The sediment resuspension and diffusion model is an integral part of a sediment transport and morphologic change model. We examined a vertical one-dimensional sediment resuspension and diffusion model using field data collected at about 10-m depth off the Saemangeun $4^{th}$ dike. The field data include waves, currents and suspended sediment concentration near the bed for about a day in May, 2007. The suspended sediment concentration obtained from the 1D model overestimated the observation about two orders of magnitude with single grain size and multiple grain sizes. The incorporation of the bed armoring effect, which adjusts the amount of suspended sediment with the available bed sediment, improved the agreement between the model and observation within a factor of two.

• Journal of the Korean Society of Combustion
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• v.3 no.1
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• pp.41-48
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• 1998

A numerical study on combustion in a fluidized bed is based on three dimensional mixing and dispersion phenomena in the bed owing to the bubble growth in the vertical direction. As fluidizing velocities increase, bubble diameters increase, which activates the fuel dispersion in the bed. The combustion rates, however, reduce due to the decrease of gas exchange rates between bubble and emulsion phases. Fuel distributions in the bed are dependent on fluidizing velocities, equivalence ratios, fuel particle diameters, fuel feeding points, and the number of fuel feeders.

• Journal of Drive and Control
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• v.18 no.4
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• pp.19-27
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• 2021

A bunker bed is a type of furniture that efficiently utilizes a narrow indoor space by having a high bed and using the empty space below as a living and storage space. The demand for multi-purpose furniture is increasing due to the recent increase in single-person households and wide-spread shared accommodation. According to the consumer research, one of the major drawbacks of a bunker bed was to get on and off the bed through a ladder or stairs. In order to overcome these problems, it was confirmed that the height adjustment function that can easily adjust the minimum and maximum heights of the bed was necessary. In this study, a height adjustable bunker bed was designed by using a gas spring that generates a repulsive force by the compressed gas inside. The design process consisted of the following three steps: Firstly, the hysteresis characteristics due to a friction and spring constant of a commercial gas spring were confirmed by measuring the repulsive force vs. compressed displacement. Secondly, requirements of the vertical lifting force exerted on the bed against gravity force were derived. Finally, the height-adjustable bed using the four-bar link mechanism was designed with 4 parameters so that the bed weight of 60-70 kgf could be adjusted to 800 mm in height by an affordable initial operation force. The performance was verified through prototype production and the results of vertical displacement and force to move were nearly the same as designed. In addition, an electrically operated height-adjustable bed was also designed with linear actuators and the performance was proved with the prototype.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.71-72
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.751-752
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• 2013

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1199-1204
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• 2006

The pressure drop and heat transfer coefficient were measured at room temperature in CFB heat exchanger with multiple vertical tubes. Also the circulation rate of solid particles was measured. The theoretical model for predicting heat transfer coefficient using the solid flowrate was developed in this study. The model predictions were compared with the measured heat transfer coefficient to show relatively good agreement.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.755-760
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• 2006

The exhaust gas with solid particle goes through the riser in both particle circulating type and circulating fluidized bed type heat exchanger to recover the heat. During heat transfer, gas velocity in vertical riser decreases as viscosity of exhaust gas decreases. In this case, when the particle size is fixed, sometimes the exhaust gas happens to have lower velocity which prohibit them to go out of the riser. In this paper the particle motion in vertical Rayleigh flow was studied. The behavior of heat transfer was investigated by means of velocity and temperature distribution. The result from numerical analysis was validated by the experimental results. Fortran code was used to analyze the particle motion in vertical Rayleigh flow.

• Journal of Wetlands Research
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• v.16 no.1
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• pp.51-59
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• 2014

A sewage was treated using serially combined vertical and horizontal flow zeolite-filled reed bed. The sewage from the student dormitory of Changwon National University was fed into the reed bed for 10 minutes every 6 hours at the hydraulic load of 314 $L/m^2{\cdot}day$. The reed bed depth was 100cm and the zeolite mixture was filled in the reed bed. The mixture consisted of the same volume of two types of zeolite ; 0.5~1mm and 1~3mm in diameter. pH value decreased in vertical bed, while it increased in horizontal bed. But DO concentration in the effluent of both beds was higher than that in the influent. Average removal efficiencies of the entire treatment system were 99.22% SS, 95.56% BOD, 91.02% $COD_{Cr}$, 87.78% $COD_{Mn}$, 45.87% T-N, 99.88% $NH{_4}^+-N$ and 71.17% T-P. Most of T-N in the effluent was $NO{_3}^--N$. However, the concentration of $NO{_2}^--N$ in the effluent was lower than 0.04 mg/L. All removal efficiencies did not show a remarkable seasonal change.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.357-373
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• 2022

The high-temperature gas-cooled reactor pebble-bed module project is the first commercial Generation-IV NPP(Nuclear Power Plant) in China. A new joint is used for the vertical support of RPV(Reactor Pressure Vessel). The steel corbel is integrally embedded into the reactor-cabin wall through eight asymmetrically arranged pre-stressed high-strength bolts, achieving the different path transmission of shear force and moment. The vertical monotonic loading test of two specimens is conducted. The results show that the failure mode of the joint is bolt fracture. There is no prominent yield stage in the whole loading process. The stress of bolts is linearly distributed along the height of corbel at initial loading. As the load increases, the height of neutral axis of bolts gradually decreases. The upper and lower edges of the wall opening contact the corbel plate to restrict the rotation of the corbel. During the loading, the pre-stress of some bolts decreases. The increase of the pre-stress strength ratio of bolts has no noticeable effect on the structure stiffness, but it reduces the ultimate bearing capacity of the joint. A simplified calculation model for the elastic stage of the joint is established, and the estimation results are in good agreement with the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.26-27
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• 2014

This paper proposes a new bed stage system for vibration attenuation in patient compartment of ambulance. The bed stage which consist of four MR dampers can isolate vibration in the vertical, rolling and pitching directions. After evaluating dynamic characteristics of MR damper, 1/4 bed stage model is formulated. The sky hook controller is then utilized for vibration control. Finally, control responses of the bed stage equipped with MR dampers are presented.