• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.169-177
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• 2018

Glass fiber reinforced polyester (GFRP) composites are widely used as structural materials in harsh environment such as underground pipes, tanks and boat hulls, which requires long-term water resistance. Especially, these materials might be damaged due to delamination between gelcoat and composites through an osmotic process when they are immersed in water. In this study, GFRP laminates were prepared by surface treatment of UPE (unsaturated polyester) gelcoat by vacuum infusion process to improve the durability of composite materials used in underground pipes. The composite surface coated with gelcoat was examined for surface defects, cracking, and hardness change characteristics in water-immersion environments (different temperatures of $60^{\circ}C$, $75^{\circ}C$, and $85^{\circ}C$). The penetration depth of cracks was investigated by micro CT imaging according to water immersion temperature. It was confirmed that cracks developed into the composites material at $75^{\circ}C$ and $85^{\circ}C$ causing loss of durability of the materials. The point at which the initial crack initiated was defined as the failure time and the life expectancy at $23^{\circ}C$ was measured using the Arrhenius equation. The results from this study is expected to be applied to reliability evaluation of various industrial fields where gelcoat is applied such as civil engineering, construction, and marine industry.

• Journal of Ocean Engineering and Technology
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• v.12 no.3 s.29
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• pp.31-41
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• 1998

Single fiber fragmentation technique was used to evaluate the change of interfacial properties by degradation of fiber tensile strength in the fiber reinforced composites. The influences of fiber tensile strength on the interfacial properties have been evaluated by the fragmentation specimens(weak fiber samples) of glass fiber/epoxy resin that was made using the pre-degraded glass fiber in distilled water at $80^{circ}C$ for specified periods. The effects of the immersion time on the interfacial properties in the distilled water at $80^{circ}C$ also have been evaluated by the fragmentation specimens(original fiber samples) of glass fiber/epoxy resin that was made using the received glass fiber. As the result, the tensile strength of glass fiber was decreased with the increasing of the treatment time in the distilled water at $80^{circ}C$ and the interfacial shear strength was independent of the change of the glass fiber strength in the single fiber fragmentation test. But in the durability test using the single fiber fragmentation specimen, interfacial shear strength decreased with the increasing of the immersion time in distilled water ar $80^{circ}C$. And it turned out that the evaluating of interfacial shear strength using original fiber tensile strength was valuable in the durability test for the water environment by the single fiber fragmentation technique.

• Archives of Pharmacal Research
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• v.26 no.10
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• pp.880-885
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• 2003

Research in this paper focuses on the kinetic evaluation of swelling of the liquid crystalline phases of glyceryl monooleate (GMO). Swelling of the lamellar and cubic liquid crystalline phases of GMO was studied using two in vitro methods, a total immersion method and a Franz cell method. The swelling of the lamellar phase and GMO having 0 %w/w initial water content was temperature dependent. The swelling ratio was greater at $20^{\circ}^C than 37^{\circ}^C$ . The water uptake increased dramatically with decreasing initial water content of the liquid crystalline phases. The swelling rates obtained using the Franz cell method with a moist nylon membrane to mimic buccal drug delivery situation were slower than the total immersion method. The swelling was studied by employing first-order and second-order swelling kinetics. The swelling of the liquid crystalline phases of GMO could be described by second-order swelling kinetics. The initial stage of the swelling (t < 4 h) followed the square root of time relationship, indicating that this model is also suitable for describing the water uptake by the liquid crystalline matrices. These results obtained from the current study demonstrate that the swelling strongly depends on temperature, the initial water content of the liquid crystalline phases and the methodology employed for measuring the swelling of GMO.

• Structural Monitoring and Maintenance
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• v.11 no.3
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• pp.247-262
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• 2024

Domestic sewage can greatly affect the macro-micro physical-mechanical properties of building foundation soils. In order to investigate the effect of domestic sewage on physical and mechanical properties of soils, the physicochemical properties of three groups of different concentrations of domestic sewage contaminated soil were tested through indoor experiments. Combined with scanning electron microscopy, X-ray diffraction experiments, and grey relational analysis, the degree of influence of different concentrations of domestic sewage on the physicochemical properties of soil was compared and analyzed from multiple perspectives such as microstructure and mineral composition, revealing the influencing mechanism of soil pollution by domestic sewage. The results showed that under the immersion of contaminated water, the color of the soaking water turned black first and then yellow, and brownish yellow secretions appeared on the surface of the soil samples. The moisture content, specific gravity, density, and pore ratio index of the soil samples immersed in 50% and 100% domestic sewage decreased with the increase of sewage concentration, while the liquid limit of the soil samples changed in the opposite direction. The immersion time had little effect on the slope of the compression curve of the soil samples soaked in tap water. For the soil samples immersed in domestic sewage, the slope of the compression curve and the compression coefficient increased with the increase of domestic sewage concentration and immersion time, while the compression modulus showed the opposite trend. In the soil samples immersed in tap water, there were a large number of small particles and cementitious substances, and the structure was relatively dense. With the increase of domestic sewage concentration, the microstructure of the soil changed significantly, with the appearance of sigle particle structure, loose and disorderly arrangement of particles, increased and enlarged pores, gradual reduction of small particle substances and cementitious substances, and the soil structure transformed from compact to loose. The research findings can provide theoretical reference for contaminated geotechnical engineering.

• The Korean Journal of Community Living Science
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• v.21 no.4
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• pp.633-639
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• 2010

This study was carried out to compare human thermoregulatory responses and preferred air temperature by feet immersion between summer and winter in terms of thermal comfort. Five healthy female university students participated in the study as subjects. They experienced feet immersion at $40^{\circ}C$ of water in the climatic chamber of $24^{\circ}C$, 50%RH from 19:30 to 21:00 in the summer and winter, respectively. Rectal temperature gradually decreased and maintained $0.08^{\circ}C$ lower in winter than summer, while mean skin temperature changed $0.4^{\circ}C$ greater in winter than summer(p=0.00). Air temperature selected by each subject for their thermal comfort revealed $0.8^{\circ}C$ higher in summer than winter(p=0.06). The results obtained suggest an increase in human thermoregulation and be used as preliminary data to maintain optimal indoor temperature in summer and winter.

• Journal of Surface Science and Engineering
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• v.49 no.5
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• pp.395-400
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• 2016

This article reports improved corrosion resistance and adhesion of electro-paint (E-paint) with fluoride conversion coating (FCC) on AZ31 Mg alloy for the first time. These improvements were observed in comparison to chemically polished samples with no chemical conversion coating and samples with cerium conversion coatings (CeCC). FCCs were prepared in a hydrofluoric acid (HF) solution for four different times; 10, 30, 60, and 120 s. The colour of the samples changed from light gold to brown with increasing immersion time, indicating the formation of thicker FCC coatings with increasing immersion time. The adhesion of the E-paint on FCC-coated AZ31 Mg alloy was tested after 500 h of immersion in deionized (DI) water. Salt spray test (SST) results revealed delamination of E-paint on the chemically polished sample, severe blistering on the samples with CeCC, but no delamination and no blistering on the samples with FCC.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.733-742
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• 2020

Taking the cylindrical float of the floating fence of a floating litter collection device as the research object, based on the shallow immersion characteristics of the cylindrical float, the Morison equation is modified, and the interaction between regular waves and the partially immersed horizontal cylindrical float is discussed in combination with scale model test. The results show that the modified Morison equation can accurately predict the wave force of the horizontal cylindrical float and reveal the influence of amplitude, immersion depth and period on the wave force of the cylindrical float. For partially immersed cylindrical floats, the wave force increases with the increase in wave height and decays with the increase in period. The positive value distribution of the wave force is larger than that of the negative direction, and the difference between the positive and negative directions is mainly affected by the immersion depth.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.161-170
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• 2003

The aesthetic restorative materials are widely used in recent dentistry, showed not only the different quality between each component but also showed that the environment of the material has important effect on the physical properties of the material. Especially, when the restoratives are restored in the mouth, and since saliva is existing, the restoratives are always exposed to water and affected by the saliva. The purpose of this study was to research and compare the change of the degree of water sorption after water immersion of three types of the resin-based materials and the compressive strength, and observe the relation between the change of the water absorbing degree and the compressive strength. Z-100(3M, U.S.A) as a composite resin, F-2000(3M, U.S.A) as a compomer and Vitremer Restoratives(3M, U.S.A) as a resin-modified GIC were used, and each specimen was made to measure the water sorption and to evaluate the compressive strength. The specimens for measurement of the water sorption and the compressive strength were divided into 4 groups(1 day, 2 weeks, 4 weeks, and 8weeks). Each specimen was filled in the 30cc vial with 20cc of distilled water during the fixed amount of period in $37^{\circ}C$. The water sorption is decided by dividing the difference of weight before and after the immersion by the volume, and the compressive strength was measured by using the instron after the immersion. The following results were obtained ; 1. The more the water sorption increased, the more the immersion period of three restorative materials was long. And the most of water sorption was obtained during the first 2 weeks(P<0.001). 2. The water sorption of resin-modified GIC was higher than composite resin and compomer. 3. The more the compressive strength decreased, the more the immersion period of three restorative materials increased(composite resin and compomer: P<0.001, resin-modified GIC: P<0.05). Especially, the amount of the reduction in compressive strength of the composite resin was the highest. 4. The more the water sorption of all materials increased, the more the compressive strength decreased(P<0.05).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.45 no.2
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• pp.77-84
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• 2009

This paper is to investigate the effect of the immersion time in the traditional hairtail hand line for developing the fishing methods and the fishing gear in the coast of jeju. The operating of 32 times was made with each different immersion time of hairtail hand line, and the relations between the catch and the immersion time were examined. As the result, targeted species rate was over 98% of total catch. From about 800 seconds after casting, the hooking rate was decreased and the bite loss rate was increased, it seems to be made by the decreasing factors of predators including the cutting of branch lines etc. In addition, it was supposed that the hooking rate and the bait loss rate had a deep connection with feeding time zone. The level of the correlation coefficient of the bait loss rate according to the immersion time was 0.54 at $p{\leq}0.01$, in the case of the hooking rate, 0.59 was chosen after about 800 seconds. The hooking rate and the bait loss rate according to the hook number were not irrelevant to the fish school layer. Additionally, it was assumed that the bait loss rate was related to the depth of water.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.6
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• pp.1581-1590
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• 2016

In order to reduce the risk of death from hypothermia for the fishing vessel's crew at sea, this paper suggests that the criteria of equipment of fishing vessels should be revised for fishing vessels engaged in coastal and inshore fisheries to be equipped with the immersion suit. The criteria of equipment of fishing vessels for immersion suits was amended to reflect the sinking of No.501 Oryongho but it was only reflected in ocean fisheries at Bering sea and Antarctic ocean that immersion suits must be provided with the same number of the total number of crew on board. Therefore, this paper analyses the relationship between maritime accident of fishing vessels and weather condition based on sea water temperature to find out the risk of hypothermia and also compares the international conventions(SFV Protocol 1993, Cape Town Agreement 2012, STCW-F 1995 and SOLAS 1974) and domestic law concerning criteria of equipment of fishing vessels. As a result, fishing vessels engaged in coastal and inshore fisheries are exposed to the risk of hypothermia when they are in distress and the criteria of equipment of fishing vessels should be amended to provide the immersion suits in accordance with the revision trend of international conventions.