• International Journal of Highway Engineering
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• v.15 no.2
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• pp.57-63
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• 2013

PURPOSES : This study was performed to investigate a feasibility of job-site use of recycled concrete aggregate exceeding 3% of absorption rate. Test variables are coarse aggregate types such as natural aggregate, job-site processed recycled aggregate, and recycled aggregate processed from the intermediate waste treatment company. METHODS : First, aggregate properties such as gradation, specific gravity and absorption rate were determined. Next a basic series of mechanical properties of concrete was tested. RESULTS : All strength test results such as compression, flexure and modulus were satisfied for the minimum requirements. Finally up to first 48 elapsed days the shrinkage strains of concretes made from both recycled aggregates (in case of volume-surface ratio of 300) appeared to be greater than 26% of the companion concretes made from natural aggregates. CONCLUSIONS : Drying shrinkage result is ascribed to greater absorption rate and specific gravity of those specimens made from recycled aggregate. This may be reduced with an addition of admixtures.

• Journal of the Korean Solar Energy Society
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• v.24 no.3
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• pp.39-46
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• 2004

In this paper, thermodynamic design data for heating of double-effect absorption system using LiCl-water for evaporator heating source of sofar energy are investigated for the water-LiCl pair and a comparative study of the water-LiCl pair with the water-LiBr pair is given used for the computer simulation. The computer simulation is based on mass, material and heat balance equations for each part of the system. Coefficients of performance and flow ratios for effects of different operating temperatures are investigated. It is found that the heating COP is higher for the water -LiCl pair than for the water-LiBr pair, and FR is lower for the water-LiCl pair than for the water LiBr pair.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.815-816
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• 2012

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.77-86
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• 1992

This paper discusses the thermodynamic study on the suction cooling-steam injected gas turbine cycle. The aim of this study is to improve the thermal efficiency and the specific output by steam injection produced by the waste heat from the waste heat recovery boiler and by cooling compressor inlet air by an ammonia absorption-type suction cooling system. The operating region of this newly devised cycle depends upon the pinch point limit and the outlet temperature of refrigerator. The higher steam injection ratio and the lower the evaporating temperature of refrigerant allow the higher thermal efficiency and the specific output. The optimum pressure ratios and the steam injection ratios for the maximum thermal efficiency and the specific output can be found. It is evident that this cycle considered as one of the most effective methods which can obtain the higher thermal efficiency and the specific output comparing with the conventional simple cycle and steam injected gas turbine cycle.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.85-92
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• 2021

The purpose of this study is to investigate the properties of hardener-free epoxy-modified mortars(EMMs) using ground granulated blast furnace slag(GGBFS) and alkali activators. The hardener-free EMMs with a GGBFS content of 20% using 4 types of alkali activators were prepared with various polymer-binder ratios, and tested for strengths, water absorption, carbonation depth, chloride ion and H2SO4 penetration depth. The conclusions obtained from the test results are summarized as follows: The compressive strength of the EMMs with a GGBFS content of 20% attains a maximum at a polymer-binder ratio of 10%. The flexural strength of the hardener-free EMMs using Ca(OH)2 as a alkali activator is improved with increasing polymer-binder ratios. However, the flexural strength of the EMMs using NaCO3, Na2SO4 and Li2CO3 is gradually decreased with increasing polymer-binder ratios. Regardless of the type of alkali activator, the water absorption, chloride ion penetration and carbonation depth are remarkably decreased with increasing polymer-binder ratios due to the epoxy film formed in the EMMs. The H2SO4 penetration depth of the hardener-free EMMs with a GGBFS content of 20% is gradually increased with increasing polymer-binder ratio. In this study, the properties of hardener-free EMMs using Ca(OH)2 as a alkali activator are more excellent than those of other alkali activators.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.327-340
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• 1996

In this study, a series of $LiNbO_{3}$ crystals with different [Li]/[Nb] ratios, congruent $LiNbO_{3}$ crystals with doped Mg and with Mg and codoped with Mn were grown by the Czocharalski method. These were investigated by UV and IR spectrophotometry. Stoichiometry dependences of the UV absorption edge and the $OH^{-}$ absorption spectra were studied with different [Li]/[Nb] ratios. The position of the UV absorption edge adn the shape and peak point of the $OH^{-}$ absorption spectra changed monotonously upto a critical concentration of Mg ions. The mechanism of the incorporation of Mg ions changes at this concentration. The decomposition of the $OH^{-}$ absorption spectra using a Gaussian lineshape function showed that in Li-deficient crystals the absorption spectra consist of five components in contrast to more or less perfect stoichiometric crystals which reveal to three components. On the basis of these results, the intrinsic and the extrinsic defect structure models in $LiNbO_{3}$ crystals were examined. The behaviour of $\nu$ (OH) reflects the defect structure and supports the Li-site vacancy model as the intrinsic defect structure model and the corresponding extrinsic defect model. A brief discussion is also given of the behaviour of $\nu$ (OH) in $LiNbO_{3}$ crystals simultaneously doped with several kinds of impurity.

• Journal of Applied Biological Chemistry
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• v.64 no.2
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• pp.159-164
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• 2021

Heavy metals exist in soils in various chemical forms including free metal ions and organo-metal complexes. The ratio of free metal ions has been known to be highly associated with the plant absorption of heavy metals. This study aims to understand the effect of free ions and organo-metal complexes on the absorption of lead (Pb) and cadmium (Cd) by plants. For this, lettuce grown in a hydroponic system for 28 days was consequently grown another 48 hours using Pb and Cd solutions. The ratios of free ion to organo-metal complexes in the solutions were adjusted at 100:0, 90:10, 70:30, 60:40 by four different organic acids (citric, oxalic, acetic, and humic acid). After that, the concentration of Pb and Cd in lettuce were analyzed. The Pb and Cd absorption by lettuce was more relied on the types of organic acids treated and the type of metals rather than the ratio of free metal ions. For example, citric acid increased the Pb absorption while it decreased the Cd absorption by lettuce. There was no significant relationship between free metal ion ratios and both Pb and Cd uptake by lettuce. It could be explained that citric acid, a relatively higher molecular weight organic acid, has higher ion binding capacity, so it forms organo-Pb complex easily due to the higher affinity of Pb on the binding site in comparison with Cd. Consequently, this complexation would assist Pb uptake by lettuce.

• 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.

• Journal of the Korean Wood Science and Technology
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• v.51 no.6
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• pp.470-480
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• 2023

This study aimed to develop a sound-absorbing composite using sugarcane bagasse (SB) and coffee silver skin (CS) as raw materials. The composite boards were manufactured by bonding the fibers with Melamine Urea-Formaldehyde adhesive, ensuring a consistent thickness of 30 mm. Various densities were employed, namely 380, 450, and 520 kg/m³. The samples were fabricated with different fiber ratios, including SB100%, SB75% with CS25%, and SB50% with CS50%. The sound absorption coefficient (SAC) and noise reduction coefficient (NRC) were measured using the impedance tube method within a frequency range of 63-6,300 Hz. The experimental results revealed that the mixing ratio of CS exerted a notable influence on enhancing the SAC, while the density of the composite board exhibited a significant impact on increasing both the SAC and NRC. Among the densities tested, the optimal value was observed at 520 kg/m³, yielding a SAC value of 0.65 at a frequency of 1,000 Hz and an NRC value of 0.55 for the SB50-CS50 composite plate. These findings underscore the importance of considering the CS mixing ratio and composite board density when aiming to optimize sound absorption properties.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.67-74
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• 2009

Nowadays, recycling of recycled aggregates from the waste concrete is seriously demanded for the protection of environment and the shortage of aggregates owing to the large scale construction project. In this study, for the development of polymer composite recycling recycled aggregates from the waste concrete, twenty five specimens of the polymer composite were prepared with the five levels of replacement ratios of recycled aggregates (0, 25, 50, 75, 100%) and polymer-cement ratios (0,5, 10, 15, 20%), respectively. For the evaluation of the performance of polymer composite specimens, various physical properties such as compressive and flexural strengths, water absorption, hot water resistance, total pore volume and porosity were investigated. As a result, physical properties of polymer composite were remarkably improved with an increase of polymer cement ratios, but greatly decreased with the replacement ratios of recycled aggregates.