• Current Research on Agriculture and Life Sciences
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• v.4
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• pp.50-54
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• 1986

The sorption characteristics of green tea were investigated at $20^{\circ}C$ with various relative humidities. Particle size showed little effect on the sorption behavior of green tea. At low relative humidities below 57%, the sorption equilibrium were easily attained, but a high relative humidities above 75%, the sorption equilibrium were not reached after 10 days. From the estimation of sorption rate at arbitrary humidities an empirical equation was obtained; $Ln{\frac{dw}{dt}}=nLn(t)+Lnc$ The monolayer moisture contents of green tea obtained by B.E.T. equation were found to be 7.87%(powder) and 7.01%(whole), respectively.

• Composites Research
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• v.21 no.2
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• pp.1-7
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• 2008

Composite materials are currently used in aero-space industry, sport and leisure industry but it has many problems such as mechanical properties deterioration by moisture absorption. In this study, we appraised interlaminar shear strength with specimen that immersed/ immersed-dried in water environment(distilled/sea) during $100{\sim}200$days. In the result, properties degradation of resin part and silan part by moisture absorption is judged early on main cause of interlaminar shear strength, and later destruction of mechanical bonding between silan part and fiber by moisture absorption is Judged later main cause of interlaminar shear strength. In conclusion, the recovery of interlaminar shear strength is judged to difficult due to interfacial destruction by moisture when pass over irreversible by moisture in composite material.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.594-602
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• 2010

Since the requirement of the high density integration and thin package technique of semiconductor have been increasing, the main package type of semiconductor will be a chip scale package (CSP). The changes of diffusion coefficient and moisture content ratio of epoxy resin systems according to the change of liquid type epoxy resin and fillers for CSP applications were investigated. The epoxy resins used in this study are RE-304S, RE310S, and HP-4032D, and Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The micro-sized and nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these epoxy molding compound (EMC) according to the change of filler size. The temperature of glass transition (Tg) of these EMC was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these EMC according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these EMC were calculated in terms of modified Crank equation based on Ficks' law. An increase of diffusion coefficient and maximum moisture absorption ratio with Tg in these systems without filler can be observed, which are attributed to the increase of free volume with Tg. In the EMC with filler, the changes of Tg and maximum moisture absorption ratio with the filler content can be hardly observed, however, the diffusion coefficients of these systems with filler content show the outstanding changes according to the filler size. The diffusion via free volume is dominant in the EMC with micro-sized filler; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the EMC with nano-sized filler.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.9
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• pp.1344-1350
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• 2016

The purpose of this study was to evaluate the effect of edible coating on hygroscopicity and quality characteristics of a freeze-dried Actinidia arguta snack. Freeze-dried A. arguta snacks were coated with various edible coating materials such as albumin, dextrin, and whole soy flour. There were no significant effects of coating on major quality properties such as moisture content, water activity, yield, water soluble index, water absorption index, and rehydration properties of all samples. Compared with non-coated samples, edible coated samples effectively inhibited hygroscopicity as a function of hygroscopic time. The samples coated with dextrin showed lower hygroscopicity than the other coated samples. In addition, the effects of edible coating treatment on hardness, total phenolic content, and antioxidant activity measured by 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity were investigated. Edible coated samples had higher hardness, total phenolic content, and antioxidant activity than the non-coated samples as a function of hygroscopic time. Among edible coating materials, dextrin was the most effective coating material. Dextrin as an edible coating material for freeze-dried A. arguta snack may help to prevent hygroscopicity and extend market quality and shelf-life during storage.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.4
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• pp.476-483
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• 1993

The moisture sorption characteristics of commercially produced seasoned dried layer (Porphyra yezoensis) was investigated by measuring sorption isotherms. The laver and two kinds of desiccant (silica gel and zeolite based desiccant) were used at temperatures of 30, 40 and 5$0^{\circ}C$ respectively using the method of saturated salt solution. Time to reach the equilibrium moisture content at each temperature and relative humidity varied from 4~6hr for the laver to 20~25hr for the silica gel and 43~46hr for the zeolite. The isotherms of the layer and the desiccants showed the characteristic sigmoidal curve. Monomolecular layer moisture content calculated using the BET equation at each temperature (30, 40, 5$0^{\circ}C$) were 5.26, 4.46 and 3.49% (d.b.) for the laver, 17.32, 15.24 and 12.89% (d.b.) for the silica gel, 16.89, 14.92 and 14.44% (d.b.) for the zeolite, respectively, Both desiccants showed higher values of the monomolecular layer moisture content than the laver. In all cases, the monomolerular layer moisture contents were decreased linearly as the temperature was increased in the experimental ranges. Water vapor transmission rate of the packaged material was also influenced by the temperature, which could be explained by the Arrhenius equation.

• Korean Journal of Food Science and Technology
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• v.31 no.1
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• pp.128-137
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• 1999

In this study, shiitake mushrooms were dried by hot air, vacuum and freeze drying methods and theire physical properties were compared. Since the pore size affects the amount of absorption, the characteristics of water sorption were investigated at various humidities and temperatures. Results showed that the freeze dried product had the greatest pore area and the highest absorption capacity. However, all the dried samples showed similar quality. The browning degrees were severely changed with increased relative humidities and temperatures. Among these drying methods, the freeze drying gave the greatest change in browning degree. The GAB monolayer moisture contents of the dried shiitake mushroom were $5.3{\sim}7.7%$. The prediction model was also provided using parameters such as relative humidity, temperature and pore area.

• The Korean Journal of Applied Statistics
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• v.22 no.5
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• pp.961-969
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• 2009

Water absorption in water-cooled generator stator windings can cause serious accidents such as insulation breakdown and it brings a generator to the unexpected sudden outage. Accordingly, it is important to diagnose the water absorption of them in the effective operation of power plant. Especially, the capacitance value which is measured for diagnosis is very small so the special diagnosis methods like stochastic theory are needed. KEPRI developed the water absorption test equipment and diagnosis technology for them. In this paper we propose that water absorption test of generator stator windings using probability distributions. The proposed diagnosis technology is applied to the real system and the results of water absorption test for stator windings are agreed to them of water leak test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.139-145
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• 2016

In this study, the moisture related hygroscopic characteristics and mechanical properties of epoxy-clay nanocomposites were investigated by experiments as a function of the weight fraction of nanoclay. The hygroscopic and mechanical properties including the moisture saturation amount, moisture diffusivity, adhesive strength, and tensile properties were obtained by moisture absorption test and various tensile tests, respectively. Also, the molecular dynamics (MD) simulation was devised to study of hygroscopic characteristics of nanocomposites and the results were compared to experimental results as a function of the nanoclay content. It was demonstrated that the proposed MD simulation technique can be successfully used for the prediction of the effects of the nanoclay on the moisture diffusion characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.9
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• pp.867-873
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• 2010

The failure of water-cooled generator stator windings as a result of insulation breakdown due to coolant water leaks and water absorption often occurs worldwide. Such failure can cause severe grid-related accidents as well as huge economic losses. More than 50% of domestic generators have been operated for over 15 years, and therefore, they exhibit signs of aging. Leaking and water-absorbing windings are often found during an overhaul. In an existing method for evaluating the integrity of generator stator windings, the drying process of the interior of the windings is ignored and only final leak tests are performed. In this study, it is shown that water leaks and water absorption in stator windings can be detected indirectly through vacuum pattern analysis in the vacuum drying mode, which is the used in the preparation stage of the leak test.

• Korean Journal of Food Science and Technology
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• v.17 no.2
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• pp.101-106
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• 1985

Dried soymilk residue(SMR) which was prepared by washing with ethanol and acetone, followed by drying at $60^{\circ}C$ was investigated for its sorption characteristics and the relationship between moisture content and water activity when it was mixed with wheat flour. During storage at $20^{\circ}C$ and various RH, an excess sorption phenomena was observed for solvent treated and dried SMR before equilibrium reached. A simple equation of log(dw/dt)=b log t+log a, where t is storage time(hr) and w is %$(H_2O)$ was drived for sorption or desorption rate of dried SMR at RH range of 12%-92%. From sorption isothermifigure, the moisture content(Mi) could be calculated from water activity by the equation of Mi=b Aw+a. The proposed equation was proved to have better fitness than those of the Smith isotherm equation or Lang and Steinberg equation for the mixture of dried SMR and wheat flour.