• 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.

• Journal of the Korean Society of Clothing and Textiles
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• v.41 no.3
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• pp.517-526
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• 2017

The biodegradation and water absorption properties of lignin/poly(vinyl alcohol) (PVA) nanofibrous webs are investigated. Lignin/PVA nanofibrous webs containing 0, 50, and 85wt% of lignin were prepared via an electrospinning process to observe the effect of the lignin concentration on the biodegradability and water absorption properties of lignin/PVA nanofibrous webs. The morphology of the materials was examined by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). To understand the wetting behavior and hydrophilic nature of the electrospun lignin/PVA nanofibrous webs, the water absorbency, contact angle, and water uptake were examined. The enzymatic degradation of lignin/PVA nanofibrous webs was investigated using laccase by measuring total organic carbon (TOC) concentration over a course of 50 days. Water drops were absorbed immediately into all of the specimens. The water uptake of lignin/PVA nanofibrous webs increased as the amount of PVA in the lignin/PVA hybrid webs increased. The enzymatic degradation experiment indicated that the inherent biodegradability of lignin was retained after its transformation into nanofibers. Our findings imply that blending these two types of polymers is promising because it can lead to the development of a new range of multifunctional materials such as antimicrobial absorbent nanotextiles based on sustainable biopolymers.

• Advances in aircraft and spacecraft science
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• v.5 no.4
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• pp.499-513
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• 2018

One of the major problems in glass fiber reinforced epoxy (GFRE) composite pipes is the durability under water absorption. This condition is generally recognized to cause degradations in strength and mechanical properties. Therefore, there is a need for an intelligent system for detecting the absorption rate and computing the mass of water absorption (M%) as a function of absorption time (t). The present work represents a new non-destructive evaluation (NDE) technique for detecting the water absorption rate by evaluating the dielectric properties of glass fiber and epoxy resin composite pipes subjected to internal hydrostatic pressure at room temperature. The variation in the dielectric signatures is employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such defects. ECS consists of twelve electrodes mounted on the outer surface of the pipe. Radius-electrode ratio is defined as the ratio of inner and outer radius of pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes on the basis of water absorption rate in the pipe material as a function of absorption time. The arrangements for positioning12-electrode sensor parameters such as capacitance, capacitance change and change rate of capacitance are analyzed by ANSYS and MATLAB to plot the mass of water absorption curve against absorption time (t). An analytical model based on a Fickian diffusion model is conducted to predict the saturation level of water absorption ($M_S$) from the obtained mass of water absorption curve. The FE results are in excellent agreement with the analytical results and experimental results available in the literature, thus, validating the accuracy and reliability of the proposed expert system.

• Advances in nano research
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• v.14 no.1
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• pp.81-92
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• 2023

In this work, the effect of the addition of Aerosil 200, an insulating resin applied in many industries, on the water absorption of cement plast mixture has been experimentally evaluated. First, the preparation stages of cement plast mixture was evaluated based on corresponding standards and then, the effect of the addition of Aerosil 200 nanoparticles (NPs) to cement plast mixtures with sand weight percentage range of 0-0.1% on the variation of water absorption properties was evaluated based on National Standard Institution of Iran 20185 for Concrete Flooring Blocks - Requirements and Test Procedures. Based on the obtained results, it could be found that excessive addition of NPs did not affect the physical properties of the final product. Water absorption percentage was increased in the weight percentage of cement. By the increase of the amount of Aerosil 200 NPs in the prepared cement plast mixture, the percentage of water absorption in weight percentage of sand was decreased. Cement plast with NPs presented significantly lower water absorption than that without NPs.

• Advanced Composite Materials
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• v.16 no.2
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• pp.83-94
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• 2007

Woven sisal textile fiber reinforced composites were used to evaluate fracture toughness, tensile and three-point bending. The water absorption testing of all specimens was repeated five times in this study. All specimens were 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 surfaces were taken to study the failure mechanism and fiber/matrix interfacial adhesion. It is shown 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 showed poor mechanical properties, such as lower values of maximum strength and extreme elongation. The $K_{IC}$ values demonstrated a decrease in inclination with increasing cyclic times of wetting and drying for the epoxy and vinyl-ester.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.88-89
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• 2020

Research is underway to incorporate water-repellent agents inside mortars to improve the durability of concrete. Therefore, in this study, the mechanical properties and absorption rate were evaluated by adding a hybrid water repellent in which a liquid and a solid were mixed at a constant ratio.As a result of the experiment, the compressive strength of the mortar added with the hybrid water repellent showed a strength reduction of about 5% than the compressive strength of the OPC, and the overall water absorption was lower than that of the water repellent used alone.

• Journal of the Korean Wood Science and Technology
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• v.32 no.3
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• pp.71-78
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• 2004

The purpose of this study was to investigate the water absorption and thickness swelling of biocomposites at room temperature. These properties of bio-composites mainly depend on the ability of the agro-flour to absorb water through hydrogen bonding between water and the hydroxyl groups of the holocellulose and lignin in the cell wall. As the content of agro-flour increased, the water absorption and thickness swelling of the bio-composites increased. The effects of agro-flour content and rice husk flour (RHF) particle size on the water absorption and thickness swelling of the bio-composites were evaluated. In general, wood-based materials showed significantly higher water absorption and thickness swelling than the bio-composites. This might be attributed to the ability of the polybutylene succinate (PBS) hydrophobic polymer to prohibit the water absorption and thickness swelling of the bio-composites, Therefore, the use of agro-flour filled PBS bio-composites, which exhibit improved dimensional stability in comparison with wood-based materials, is recommended.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.3_4
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• pp.539-545
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• 2004

In this study, the effect of washing, bleaching, and abrasion on tactile and the water absorption properties of the split-type Nylon/Polyester (N/P) microfiber pile-knit was investigated under various enduse conditions. We examined the water absorption and surface properties of PET microfiber which will be very useful in the future. We also studied the variations of their performance during usage caused by friction and repeated washing, regard to all kinds of physical, chemical changes which will appear while using those textiles. Progress in further splitting of PET microfiber fabric is observed with increases in the number of washing and bleaching cycles, and treatment temperature. Initial water absorption (%) was increased with progress in splitting, which provided efficient capillary channel. Surface properties were varied with additional splitting by washing and abrasion. Formation of pilling and splitting by abrasion increase surface roughness, diminishing tactile property, and reduced water absorption property. The current results from this study is expected to provide the appropriate washing management guide to consumers, and to inform end-use performance of product to a producer for improving product quality.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.3
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• pp.119-125
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• 2013

IInsulation material is generally used for preventing heat loss from heat transport fluids, and water absorption severely reduces the insulation property. The purpose of this study is to evaluate the amount of water absorption supplied by the pouring method and spraying method, to investigate the effects of water absorption on the thermal conductivity of an insulation material, and modeling the relation between water absorption and thermal conductivity. E-glass, a kind of glass fiber, and HYPERLITE, mainly composed of pearlite, are selected, to compare hygroscopic and insulation properties. E-glass is found to have much higher water absorptivity, compared to HYPERLITE. The thermal conductivity of the water-absorbed E-glass is increased by more than 150%, compared to that of no absorption, while variation of the thermal conductivity of HYPERLITE with water absorption is insignificant. A three-stage model of water absorption for thermal conductivity is developed, and the modeling results are found to be in good agreement with the experimental data.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.11 no.1
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• pp.8-14
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• 1975

The optical properties of the sea water were studied by use of underwater lux-meters in the coastal waters of Busan from May to November 1975. The absorption coefficient of the sea water in the area ranges from O. 169 to 1. 049 and the mean absorpflOn coefficient is 0.413. Maximum monthly mean absorption coefficient (0. 56) was observed in August, while the minimum was O. 338 in September. There was a distinct discontinuity layer of the absorption coefficient in accordance with the thermocline and the halocline in summer. The mean transparency of the area was 3. 8 meters, and transparency in autumn was higher than that in summer. The relation between absorption coefficient (m) and transparency (D) was deduced, m=1. 57/ D. The rate of light penetration at 5 m-layer of sea water was 2. 5 percent when the solar altitude was six degree in July 1975.