• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.7 s.250
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• pp.779-786
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• 2006

Woven sisal textile reinforced composites were manufactured to evaluate fracture toughness, and tensile test. All specimens were immersed in water five times. All specimens are immersed in pure water during 9 days at room temperature, and dried in 1 day at $50^{\circ}C$. Two kinds of polymer matrices such as epoxy and vinyl-ester were used. Fractured surface were investigated to study the failure mechanism and fiber/matrix interfacial adhesion. It is shows that it can be enhanced to improve their mechanical performance to reveal the relationship between fracture toughness and water absorption fatigue according to different polymer matrices. Water uptake of the epoxy composites was found to increase with cycle times. Mechanical properties are dramatically affected by the water absorption cycles. Water-absorbed samples observed poor mechanical properties such as lower values of maximum strength and extreme elongation. The $K_{IC}$ values demonstrate a decrease in inclination with increasing cyclic times of wetting and drying fur the epoxy and vinyl-ester.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.977-984
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• 2013

A hygroscopic rotor comprises many microchannels with high adsorption characteristics. In this study, the iterative adsorption/desorption processes that were affected by the humid air flow in a channel were numerically simulated. In consideration of the accuracy and computational costs, in the desiccant layer, only surface diffusion was considered in this simulation. The results were compared with the previous numerical results and found to show good agreement. By conjugating the heat and mass transfer between the desiccant and the flow layers, temporal and spatial changes in the vapor mass fraction, adsorbed liquid water mass fraction, and temperature in the channel were presented.

• Journal of Conservation Science
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• v.32 no.2
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• pp.249-259
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• 2016

Effect of the flame retardants on Dancheong is studied in the present work. Two kinds of flame retardants were applied on Dancheong specimens and compared with control groups on which distilled water was applied instead of the flame retardants. The flame retardants enhanced the hygroscopic property of the surface of Dancheong. Furthermore, the added flame retardants reacted with oyster shell white($CaCO_3$) and lead red($Pb_3O_4$), producing new chemical compounds like Calcium phosphate tribasic and Lead Phosphates which make the painted layer of Dancheong dissolving and whitening over certain period of time. When applied in excessive amount and exposed in repetitive wet and dry condition, especially, they aggravate the surface problems significantly. These results will provide a good reference on the study of the discoloring/whitening effect of Dancheong layers at many traditional wooden building in Korea.

• Korean Journal of Environmental Agriculture
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• v.17 no.4
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• pp.358-361
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• 1998

This study was carried out to develop a short term hardening method of tree seedlings of Rhus chinensis Mill., Evodia daniellii Hemsley and Parthenocissus tricuspidata(Sieb. et Zucc.) Planck for afforestation on a concave and a crack of cut-rock slope. The seedlings were grown in a cylinder shaped pot made of polyvinyl net with the soil media of peatmoss, vermiculite, clay, compost, fertilizer, and absorbant(40:25:19:15:1:0.1, v:v). They were cultivated in a greenhouse for four months and in field condition for two months. During the last three months of the growing period the seedlings were hardened by periodic desiccation and irrigation in 4 to 10 days interval. The hardened seedlings showed lower leaf water potential, higher leaf osmotic pressure, and lower T/R ratio than those before the hardening. The hardened seedlings survived well on the soil medium in the concave of cut-rock slope.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.555-560
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• 2018

The high temperature stability of a chloride mixture, $NaCl-KCl-ZnCl_2$ (NaKZn-Chloride), is investigated to evaluate its potential as a thermal storage material. A thermal storage media should maintain a stable thermal properties within the temperature range of heat storage. Results from an a priori experiment showed that the NaKZn-chloride is stable only up the much lower temperature, while its stability limit is reported to be $850^{\circ}C$ in the literature. This study aims to investigate if the thermal property is changed by the moisture absorbed in the heat storage material. The effect of moisture content on the thermal properties was measured. The results show that the melting point remains the same regardless of the amount of moisture absorbed. Meanwhile, the high temperature stability is lower for the moisture treated samples. The results of this work infer that the loss of a hygroscopic thermal storage media can be reduced by avoiding its contacts to moisture in designing high temperature thermal storage systems.

• Journal of Sericultural and Entomological Science
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• v.47 no.1
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• pp.41-47
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• 2005

Kayagum is a traditional musical instrument in Korea. Kayagum strings are usually made of raw silk. It needs good vibration and durability. This study was carried out to increase durability of the strings by chemical treatment and manufacture of silk/polyester and silk/wild silk compound yarn. In this study, we used MKW-810(water solube acrylic adhesive)and polyvinyl alcohol as a adhesive. Before the twisting, the raw silk wet on the string manufacture process. The adhesive reagent were added in this process. And compound yarn were prepated by domestic silk, polyester and wild silk(antheraea pernyi) for make of Kayagum strings, respectively. The result are as follows. 1. Tenacity and elongation of the strings are almost same between none and chemical treatment. However number of extension cycling to breaks of the strings was largely increased by chemical treatment. Number of extension cycling to breaks of the strings is very important and useful item to check durability of the strings. The stiffness of the strings were almost same between none and adhesive treatment 2. Tenacity of the silk/polyester strings is largely decreased by increasing of polyester portion, but elongation of the silk/polyester strings increased. However tenacity of the silk/polyester(mono filament) strings are higher than that of silk strings. 3. Tenacity of the domestic silk/wild silk strings is largely decreased by increasing of wild silk portion, but elongation of the domestic silk/wild silk strings is almost same among silk and domestic silk/wild silk strings.

• Analytical Science and Technology
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• v.18 no.1
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• pp.43-50
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• 2005

A number of carbonyl compounds including formaldehyde and acetaldehyde are well known for their toxicity and irritancy. Hence, acquisition of both qualitative and quantitative tool for their analysis is essential to resolve issues associated with malodor or indoor pollution. Using HPLC/UV method, we examined various aspects involved in the measurements of formaldehyde in environmental samples. The results of our analysis indicated that its detection was made as low as 0.5 ppb (assuming 5 L of sample volume), while its precision was maintained near 2% in terms of relative standard error (RSE). When the stability of calibration was checked by variability of slope values obtained over long-term period (e.g., one month), its values were found to remain constantly with RSE values of 3%. It was also found that liquid-phase reaction between formaldehyde and DNPH proceed very slowly to attain equilibrium (one and half hour), while requiring adequate amount of DNPH to form their derivatives. The overall results of our study thus suggest that there are a number of factors to consider for the accurate analysis of formaldehyde in ambient air.