• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.1
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• pp.45-54
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• 2007

This study was performed to evaluate strength and watertightness properties of EVA modified high strength concrete in order to improve durability of concrete used in agricultural water utilization facilities that are in constant contact with water. Materials used were cement, coarse and fine aggregates, silica fume, EVA and AE water reducing agent. Tests for the slump, compressive and flexural strengths, absorption ratio and permeability coefficient according to curing condition (water and water+dry curing) and content ratio of EVA were performed. The slump results of EVA modified high strength concrete similarly showed in the content ratio of EVA powder less than 4% and decreased in the content ratio of EVA powder more than 6% compared to that of concrete without EVA powder. The compressive strength of EVA modified high strength concrete decreased with increasing the content ratio of EVA powder. The flexural strength of EVA modified high strength concrete increased with increasing the content ratio of EVA powder in the content ratio of EVA powder ratio less than 4% and had similar or slightly decreased in the content ratio of EVA powder more than 6% compared to that of concrete without EVA powder. The absorption ratio and permeability coefficient of EVA modified high strength concrete decreased with increasing the content ratio of EVA powder in the content ratio of EVA powder less than 4% and slightly increased in the content ratio of EVA powder more than 6%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.3
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• pp.219-227
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• 1989

Performance analysis of an absorption heat pump system for solar energy recovery has been done by computer simulation to find improved working pairs. Based on the thermodynamic analysis, the coefficient of performance and mass flow ratio have been calculated to compare two aqueous solutions [LiCl-water, $LiCi-CaCl_2-Zn(NO_3)_2$-water] which were developed for cooling by others, with the conventional LiBr-water solution. As a result of this analysis, the performances of the new aqueous solutions were found to be better than that of LiBr-water solution not only in cooling systems, but also in heating and in heat transformer systems. Their theoretical thermodynamic performance data were given here with.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.4
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• pp.285-292
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• 1985

A computer program for thermal design analysis has been developed to predict the performance of an absorption heat transformer. The effects of temperature boost, cooling water temperature and effectiveness of components on the performance were investigated. Not only the detailed thermodynamic states such as temperatures, concentration of the solution, and mass flow rate at each point of the process but also the heat transfer rate in each component could be easily determined with given input parameters. The system's coefficient of performance (COP) was seen to increase with increased effectiveness of components, decreased temperature boost of hot water, and decreased cooling water temperature. Even though the COP increases with increased effectiveness of the components, the variation in the COP is not substantial above certain values of the effectiveness. A reference design point can be selected on this basis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.196-206
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• 1995

Experimental investigations on heat and mass transfer characteristics in a vertical tube absorber have been carried out. Three different copper tubes with a length of 1.5m have been tested using LiBr solution and LiBr-$CaCl_2$ solution. The effects of solution flow rate, cooling water temperature, solution inlet temperature and evaporation temperature have been investigated in detail. It is found that heat transfer coefficient increases gradually with the increase of solution flow rate, but decreases rapidly for the flow rates less than 0.02kg/ms. The grooved tube generally shows better heat transfer performances than the smooth tube. LiBr solution shows almost no absorption capability for the cooling water temperatures over $40^{\circ}C$. LiBr-$CaCl_2$ gives less decreasing rate in absorption capability at these temperatures and the heat transfer coefficient becomes less dependent on the types of tubes in use. Considering heat and mass transfer rates, LiBr-$CaCl_2$ solution is found to be more suitable than LiBr solution for air cooled absorber, which operates at higher temperature than water cooled absorber.

• Journal of the Semiconductor & Display Technology
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• v.12 no.1
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• pp.23-28
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• 2013

Epoxy resins are widely used in microelectronics packaging such as printed circuit board and encapsulating for semiconductor manufacturing. Water can diffuse into and through the epoxy matrix systems and moisture absorption at boarding interfaces of matrix resin systems can lead to a hydrolysis at the interfaces resulting in delamination of encapsulating materials. In the study, the changes of diffusion coefficient and moisture content ratio of epoxy resin systems with nano-sized fillers according to the change of liquid type epoxy resins were investigated. RE-304S, RE-310S, RE-810NM and HP-4032D as a epoxy resin, Kayahard AA as a hardener, and 1B2MI as a catalyst were used in these epoxy resin systems. After curing, moisture content ratios were measured with time under the 85 and 85% relative humidity condition using a thermo-hydrostat. The maximum moisture absorption ratio and diffusion coefficient of EMC decrease with the filler content. It can be seen that these decreases are due to the increase of filler surface area and the decrease of moisture through channel with the content of nano-sized filler.

• YAKHAK HOEJI
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• v.22 no.1
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• pp.27-32
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• 1978

Metoclopramide reacts with ammonium cobaltothiocyanate to form a stable ion pair which has an absorption maximum of 625mm. The reaction product was insoluble in water but soluble in most organic solvents. 1,2-Dichlorethane was the best extracting solvent among the several organic solvents tested. Metoclopramide can be determinded not only by visible light spectrophotometry but also indirectly by estimation of cobalt in the organic phase by flameless atomic absorption spectrophotometry. Linear relationship was found between absorbance and concentration in the range of 10$^{-4/}$-10$^{-3}$M by spectrophotometry and 10$^{-5}$-10$^{-4}$M by flameless atomic absorption spectrophotometry. The coefficient of variation by spectrophotometry was 0.9% and that of flameless atomic absorption was 1.8%. There was no interference with excipients, pH, temperature and reaction time. With this method, it is possible to determine accurately metoclopramide and tertiary amines in pharmaceutical preparations.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.555-560
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• 2023

Conventional aqueous amine-based CO₂ capture has a problem in that a large amount of renewable energy is required for CO₂ stripping and solvent regeneration in its industrial applications. This work proposes a water-lean absorbent that can reduce regeneration energy by lowering the water content in the absorbent with high absorption capacity for CO₂. To this purpose, this water-lean solvent introduced NMP (N-methyl-2-pyrrolidone), which has a higher physical solubility in CO₂ and a low specific heat capacity comparing to water, along with 3-methylaminopropylamine (MAPA), a diamine, into the absorbent. The circulating absorption capacity and absorption rate for CO₂ of this water-lean solvent were measured using a packed tower. When NMP was added to the absorbent, the absorption rate was improved. In the case of the absorbent containing 2.5M MAPA was used, the maximum circulating absorption capacity was obtained when 10 wt% of NMP was included in absorbent. The overall mass transfer coefficient increased as the concentration of NMP increased. However, at loading values higher than 0.5, the increment in mass transfer coefficient decreased as the concentration of NMP increased. When the lean loading value is low, the mass transfer resistance due to viscosity of the absorbent is low, so the overall mass transfer coefficient increases with the addition of NMP. However, as the lean loading value increases, the viscosity of the absorbent increases, and the diffusivity of CO₂ and MAPA decreases, resulting in sharply decreasing of the overall mass transfer coefficient.

• The Journal of the Acoustical Society of Korea
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• v.23 no.7
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• pp.497-502
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• 2004

Both ultrasonic velocity at 3 MHz and absorption coefficient in the frequency range of 0.2-2 MHz were measured for poly (sodium 4-styrenesulfonate) aqueous solution over the concentration range of 5 to 25 % by weight. Pulse echo overlap method was employed to measure the ultrasonic velocity over the temperature range of 10-90 ℃ and the high-a ultrasonic resonator method was used for the absorption coefficient measurement at 20 ℃. The velocity exhibited a maximum value at approximately 55. 59, 63. 67, and 71 ℃ in 25, 20. 15, 10. and 5 wt% solutions, respectively. The velocity increased with poly (sodium 4-styrenesulfonate) concentration at a given temperature. The concentrations dependences of the relaxation frequency and amplitude showed that the relaxation around 200 kHz is related to the structural fluctuations of polymer molecules, such as the segmental motions of the polymer chains and that around 1 MHz resulted from the proton transfer reaction of the oxygen sites of SO₃. Both the absorption and the shear viscosity increase with the Polymer concentration. but decrease with temperature.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2180-2182
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• 2000

Laser emission, a part of electromagnetic wave, has short propagation length in water, and the underwater applications of laser are limited. The acquisition of underwater imaging is possible only by using a blue-green laser since the blue-green range has relatively small absorption coefficient in water. We introduce the conditions of the laser required for underwater imaging and the attenuation characteristics of a blue-green laser used in water.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.525-532
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• 2000

Evaporation heat transfer characteristics have been investigated experimentally when distilled water is sprayed on the outside wall of horizontal tubes in a evaporator. This problem is of particular interest in the design of evaporator of an absorption system. Hydrophilic surface treatment was employed to increase the wettability on copper tubes. The results indicate that evaporation heat transfer with hydrophilic tubes is shown to be 25-44% higher than that with bare tubes at evaporation pressure of 31.8 Torr(evaporation temperature$ 30^{\circ}C). Evaporation heat transfer rates of hydrophilic treatment tubes are improved substantially, comparing with those of conventional copper tubes in the wide range of operating parameters, such as water inlet temperatures, water mass flow rates and evaporation pressures.