• Journal of Energy Engineering
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• v.21 no.1
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• pp.43-46
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• 2012

A fluidized bed drying approach was utilized to the synthesis of water glass based silica aerogel powders. The effects of the fluidized bed drying conditions such as the superficial velocity and temperature of hot air and bead size as well as bead/wet-gel ratio, on the physical properties such as tapping density and productivity of the aerogel powders were systematically investigated. The experimental results showed that the amount of beads mixed with wet-gels in the fluidized bed column has the most profound impact on the fluidization efficiency, greatly enhancing the yield of the aerogel powders up to 98% with a proper bead/wet-gel weight ratio as compared to 72% without using beads. No significant change was observed in the tapping density over a wide range of the fluidized drying condition. Consequently the fluidized bed drying approach shows a good promise as an alternative route for the large-scale production of the aerogel powders.

• Current Optics and Photonics
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• v.3 no.3
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• pp.243-247
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• 2019

We have developed a compact, wavelength-selectable, Q-switched Nd:YAG laser at mid ultraviolet for chemical warfare agent detection. The fundamental wave at 1064 nm is delivered by a pulsed solid state laser incorporating with a square-type Nd:YAG rod in a resonator closed by two crossed Porro prisms for environmental reliability. The output energy at 213 nm ($5{\omega}$) and 266 nm ($4{\omega}$) by ${\chi}^{(2)}$ process in the sequentially disposed BBO crystals are measured to be 6.8 mJ and 15.1 mJ, respectively. The output wavelength is selected for $5{\omega}$ and $4{\omega}$ by a motorized wavelength switch. The energy ratio of the $5{\omega}$ to the $4{\omega}$ is varied from 0.05 to 0.85 by controlling the phase matching temperature of the nonlinear crystal for sum-frequency generation without change of the output pulse parameters.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.1
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• pp.47-55
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• 1985

To determine the change of the mechanical properties of the wool/polyester blend fabrics in proportion to blend ratio, 10 mechanical properties were measured on 6 blend fabrics by KES-F system. Blend ratio on the 6 blend fabrics was increased by $20\%$, and the structure of the fabric were plain, 2/2 twill, respectively. And wearing performances in propoetion to blend ratio on the 6 blend fabrics were investigated. In this experiment. the following conclusions were obtained with the increase of blend ratio of polyester. 1) The values of WT, RT in tensile properties. tensile energy and elongation, and RC in compressional properties were decreased. 2) The values of B, 2HB in bending properties, 2HG. 2HG 5 in shearing properties were increased. 3) Putting on clothes, wearing performance was bad because crumbling of shape and wrinkle were easily made an appearance. Particularly it was remarkably bad as blend ratio of polyester was expressed $60\%$.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.580-584
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• 2007

The ZrC layer instead of SiC layer is a critical and essential layer in TRISO coated fuel particles since it is a protective layer against diffusion of fission products and provides mechanical strength for the fuel particle. In this study, we carried out computational simulation before actual experiment. With these simulation results, Zirconium carbide (ZrC) films were chemically vapor deposited on $ZrO_2$ substrate using zirconium tetrachloride $(ZrCl_4),\;CH_4$ as a source and $H_2$ dilution gas, respectively. The change of input gas ratio was correlated with growth rate and morphology of deposited ZrC films. The growth rate of ZrC films increased as the input gas ratio decreased. The microstructure of ZrC films was changed with input gas ratio; small granular type grain structure was exhibited at the low input gas ratio. Angular type structure of increased grain size was observed at the high input gas ratio.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.1
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• pp.53-58
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• 2007

In an estuary, mixing and transport of contaminant sometimes occurs in the salt finger favorable condition (Hwang ang Rehmann, 2004). Linearized theory is applied to predict flow dynamics in salt finger favorable condition. The simulated results match well with previous laboratory experiments. When the density ratio is larger than 2, the heat and salt system shows $0.55{\sim}0.57$ as Turner (1967) found, and the salt and sugar system produces 0.87 of Griffiths (1980). As the ratio of molecular diffusivities of two scalars increases, the flux ratio increases. The flux and eddy diffusivity ratios decrease with increase of density ratio, and it takes longer time for flux ratio to be steady state at the higher density ratios.

• Journal of Hydrogen and New Energy
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• v.22 no.6
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• pp.749-758
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• 2011

The present work explores the performance and operation limit of electrodialysis cell for HI concentration in sulfur iodine thermochemical hydrogen production process, For this purpose, the electrodialysis cell was assembled with Nafion 117 as a PEM membrane and two activated carbon papers as the electrodes. HIx solution was prepared with composition of HI: $I_2$: $H_2O$ = 1: 0.5~2.5: 5.2 in molar ratio. The cell and its peripheral apparatus were placed in the specially designed convective oven in order to uniformly maintain the operation temperature. As operation temperature increased, the amount of water transport from anode to cathode increased, thus reducing HI molarity in catholyte. Meanwhile, the current efficiency was constant as about 90 %, irrespective of temperature change. The cell voltage increased with initial $I_2$ mole ratio as well as anolyte to catholyte mole ratio. Moreover the cell voltage overshot took place within 10 h cell operation, which is due to the $I_2$ precipitation inside the cell. From the analysis of $I_2$ mole ratio in the anolyte, it is noted that operation limit (in $I_2$ mole ratio) of the electrodialysis cell, arising from was measured to be 3.2, which is much lower than bulk solubility limit of 4.7.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.5
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• pp.347-352
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• 2017

Reverse electrodialysis (RED), which generates electrical energy from the difference in concentration of two solutions, has been actively studied owing to its high potential and the increased interest in renewable energy resulting from the Paris Agreement on climate change. For RED commercialization, its power density needs to be maximized, and therefore various methods have been discussed. In this paper, the power density was measured using various flow shapes based on the aspect ratio, opening ratio, and number of distribution channels. We found that the power density is enhanced with a decrease in the aspect ratio and an increase in the opening ratio and number of distribution channels.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.99-104
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• 2016

In this study, we researched the energy load according to the change of the inner window area ratio, the distance of the air gap and the azimuth of the curtain wall building, which installed the multistory double-skin facade(DSF). and we compared the results with the no double-skin facade situation as follows. With the DSF, it is better than other case, when the window area ratio is 40% and the air gap is 1.2m on the west, south-45-west, south-45-east and east. And it's best when the window area ratio is 40% and the air gap is 0.4m on the south. And on the east or south-45-east, the window area ratio is 40% and the air gap is 1.2m is better than other case with the DSF. On south, it is best when the window area ratio is 100% without DSF. On the south-45-west or west, it is best when the window area ratio is 40% without the DSF.

• Clinical and Experimental Emergency Medicine
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• v.3 no.3
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• pp.148-157
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• 2016

Objective Our aim was to compare the compression quality, exercise intensity, and energy expenditure in 5-minute single-rescuer cardiopulmonary resuscitation (CPR) using 15:1 or 30:2 compression-to-ventilation (C:V) ratios or chest compression only (CCO). Methods This was a randomized, crossover manikin study. Medical students were randomized to perform either type of CPR and do the others with intervals of at least 1 day. We measured compression quality, ratings of perceived exertion (RPE) score, heart rate, maximal oxygen uptake, and energy expenditure during CPR. Results Forty-seven students were recruited. Mean compression rates did not differ between the 3 groups. However, the mean percentage of adequate compressions in the CCO group was significantly lower than that of the 15:1 or 30:2 group ($31.2{\pm}30.3%$ vs. $55.1{\pm}37.5%$ vs. $54.0{\pm}36.9%$, respectively; P<0.001) and the difference occurred within the first minute. The RPE score in each minute and heart rate change in the CCO group was significantly higher than those of the C:V ratio groups. There was no significant difference in maximal oxygen uptake between the 3 groups. Energy expenditure in the CCO group was relatively lower than that of the 2 C:V ratio groups. Conclusion CPR using a 15:1 C:V ratio may provide a compression quality and exercise intensity comparable to those obtained using a 30:2 C:V ratio. An earlier decrease in compression quality and increase in RPE and heart rate could be produced by CCO CPR compared with 15:1 or 30:2 C:V ratios with relatively lower oxygen uptake and energy expenditure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.101-109
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• 2013

Recently, it is certain that the increase of heating and cooling energy consumption by radical change in climate condition has caused serious problems related to environmental and energy concerns associated with increase of fossil fuel usage and carbon dioxide production as well as global warming. So, various actions to reduce greenhouse gas exhaustion and energy consumption have been prepared by world developed countries. Our government has also been trying to seek energy control methods for houses and buildings by proclaiming political polices on low-carbon green growth and construction and performance standards for environment-friendly housing. The energy consumption by buildings approximately reaches 25% of total korea energy consumption, and the increasing rate of energy consumption by buildings is stiffer than the rate by the other industries. The greatest part in the buildings of the energy consumption is building facade. While lots of research projects for reducing energy consumption of the facade have been conducted, but a few research projects on concrete comprising more than 70% of outsider of buildings has been tried. This research presents here a study to improve the insulation property of structural concrete formed by micro form admixture (MFA) with experimentally reviewing the physical, mechanical and thermal characteristics of the concrete. As the results of this experiment, in the case of concrete mixed with MFA, slump loss has been improved. As the mixing ratio of MFA increases, the compressive strength is decreased and thermal conductivity is increased. Also it was found that water-cement ratio increases, the compressive strength is decreased and thermal conductivity is increased. but, there was not big influence by the change of fine aggregate ratio.