• Geomechanics and Engineering
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• v.25 no.4
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• pp.283-294
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• 2021

This paper presents a rigorous solution for spherical cavity expansion in unsaturated soils under constant suction condition. The hydraulic behavior that describes the saturation-suction relationship is modeled by a void ratio-dependent soil-water characteristic curve, which allows the hydraulic behavior to fully couple with the mechanical behavior that is described by an extended critical state soil model for unsaturated soil through the specific volume. Considering the boundary condition and introducing an auxiliary coordinate, the problem is formulated to a system of first-order differential equations with three principal stress components and suction as basic unknowns, which is solved as an initial value problem. Parameter analyses are conducted to investigate the effects of suction and the overconsolidation ratio on the overall expansion responses, including the pressure-expansion response, the distribution of the stress components around the cavity, and the stress path of the soil during cavity expansion. The results reveal that the expansion pressures and the distribution of the stress components in unsaturated soils are generally higher than those in saturated soils due to the existence of suction.

• Journal of applied mathematics & informatics
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• v.40 no.3_4
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• pp.603-618
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• 2022

In this paper, a numerical solution of the generalized diffusion equation with a delay has been obtained by a numerical technique based on the Galerkin finite element method by applying the cubic B-spline basis functions. The time discretization process is carried out using the forward Euler method. The numerical scheme is required to preserve the delay-independent asymptotic stability with an additional restriction on time and spatial step sizes. Both the theoretical and computational rates of convergence of the numerical method have been examined and found to be in agreement. As it can be observed from the numerical results given in tables and graphs, the proposed method approximates the exact solution very well. The accuracy of the numerical scheme is confirmed by computing L₂ and L_∞ error norms.

• Food Science and Preservation
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• v.22 no.3
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• pp.314-321
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• 2015

This study was conducted to investigate the quality and characteristics of semi-dried persimmons soaked in different concentrations of sugar solution and stored at $7^{\circ}C$ for 20 days. The L value and chroma value were significantly higher in S5 and S10 compared to the other concentrations of sugar solution. The ${\Delta}E$ and browning degree were increased according to the increase in concentration of sugar solution. Total sugar, reducing sugar, and sugar free contents were higher in the control (semi-dried persimmon) than those in S0, but they increased according to the increase in concentration of sugar solution. Polyphenol oxidase and peroxidase activities were decreased according to the increase in sugar solution concentration, which were highest in S0 among other semi-dried persimmons soaked in sugar solutions. Total ascorbic acid content was highest in S10 (12.29 mg/g), followed by S0 (2.54 mg/g), S5 (7.76 mg/g), S15 (6.05 mg/g), and S20 (5.05 mg/g). Total polyphenols, flavonoids and proanthocyanidins contents were the highest in S10 compared to other semi-dried persimmons soaked in sugar solutions. Furthermore, the same tendency was observed with DPPH radical scavenging ability. These results showed that 10% sugar solution could be applied to semi-dried persimmons in order to achieve high quality, nutritional value, and browning inhibition.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.143-147
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• 2000

The effects of alginate extracting conditions from sea tangle and the effects of film preparation conditions on the physical properties of the alginate film were investigated by measuring ester compounds permeability. The higher concentration of sodium carbonate solution as extracting solvent made the higher ethyl acetate permeability of alginate film, but extracting time showed little efficacy of alginate film permeability. The higher concentration of sorbitol as a plasticizer showed higher ethyl acetate permeability of alginate film, Adding various plasticizers, the ethyl acetate permeability of algiante films was increased in order as follow : sorbitol, glycerol and polyethylene glycol. Ester compounds haying the lower molecular weight showed the higher permeability. And the higher temperature made the ethyl acetate permeability of algiante film to be high.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.287-293
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• 2021

This study was intended to investigate the influence of Al content on hardness and microstructural characteristics of discontinuous precipitates (DPs) formed by isothermal aging in Mg-8.7%Al and Mg-10%Al alloys. In order to obtain large amount of DPs in the microstructure, the alloy specimens were solution-treated at 688K for 24 h followed by water quenching, and then aged at 418K for 48h. The Mg-Al alloy with higher Al content was characterized by higher volume fraction of DPs at the same aging condition, lower interlamellar spacing of the DPs, thinner β phase layer and higher β phase content in the DPs. This is closely related to the higher velocity of discontinuous precipitation process resulting from the higher Al supersaturation in the α-(Mg) matrix. The Mg-10%Al alloy showed higher hardness of the DPs and greater difference in hardness between as-cast state and DPs than the Mg-8.7%Al alloy.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.3
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• pp.284-288
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• 1983

This experiment was carried out to investigate the stability of ascorbic acid (AsA) in the mixed solution of AsA and catechin according to the content changes of AsA and catechin under boiling, and for the respective concentration and pH. The loss of AsA was most for 10 minutes of boiling and accelerated by the mixture of catechin, but the loss was less in the high mixture rate than in the low the loss of catechin most for 10 minutes of boiling, also as the concentration of AsA becomes higher but that of cathchin lower, and as that of AsA lower but that of catechin higher, the loss of catechin becomes less moreover in the case of the low content ratio of catechin, the stability of AsA was better in order of the pH 4, pH 5, pH 6, namely as the pH increased, but in the case of the high better in order of the pH 6, pH 5, pH 4, that is as in decreased.

• Coupled systems mechanics
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• v.9 no.3
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• pp.237-264
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• 2020

This article investigates the static behaviour of functionally graded (FG) plates sometimes declared as advanced composite plates by using a simple and accurate quasi-3D and 2D hyperbolic higher-order shear deformation theories. The properties of functionally graded materials (FGMs) are assumed to vary continuously through the thickness direction according to exponential law distribution (E-FGM). The kinematics of the present theories is modeled with an undetermined integral component and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate; therefore, it does not require the shear correction factor. The fundamental governing differential equations and boundary conditions of exponentially graded plates are derived by employing the static version of principle of virtual work. Analytical solutions for bending of EG plates subjected to sinusoidal distributed load are obtained for simply supported boundary conditions using Navier'is solution procedure developed in the double Fourier trigonometric series. The results for the displacements and stresses of geometrically different EG plates are presented and compared with 3D exact solution and with other quasi-3D and 2D higher-order shear deformation theories to verify the accuracy of the present theory.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.6
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• pp.455-463
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• 2021

The adsorption process using GAC is one of the most secured methods to remove of phosphate from solution. This study was conducted by impregnating Cu(II) to GAC(GAC-Cu) to enhance phosphate adsorption for GAC. In the preparation of GAC-Cu, increasing the concentration of Cu(II) increased the phosphate uptake, confirming the effect of Cu(II) on phosphate uptake. A pH experiment was conducted at pH 4-8 to investigate the effect of the solution pH. Decrease of phosphate removal efficiency was found with increase of pH for both adsorbents, but the reduction rate of GAC-Cu slowed, indicating electrostatic interaction and coordinating bonding were simultaneously involved in phosphate removal. The adsorption was analyzed by Langmuir and Freundlich isotherm to determine the maximum phosphate uptake(q_m) and adsorption mechanism. According to correlation of determination(R²), Freundlich isotherm model showed a better fit than Langmuir isotherm model. Based on the negative values of q_m, Langmuir adsorption constant(b), and the value of 1/n, phosphate adsorption was shown to be unfavorable and favorable for GAC and GAC-Cu, respectively. The attempt of the linearization of each isotherm obtained very poor R². Batch kinetic tests verified that ~30% and ~90 phosphate adsorptions were completed within 1h and 24 h, respectively. Pseudo second order(PSO) model showed more suitable than pseudo first order(PFO) because of higher R². Regardless of type of kinetic model, GAC-Cu obtained higher constant of reaction(K) than GAC.

• The Korean Journal of Food And Nutrition
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• v.30 no.1
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• pp.139-147
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• 2017

The objective of this study was to develop anti-browning agents for commercial ready-to-eat pear products, which are preferred not only to maintain the flavor, color and texture of pears, but also to increase consumers' preference. The sliced 'Shin-go (Niitaka)' pears were immersed in 5% and 10% oxidized starch, 1% citric acid, and 5% and 10% oxidized starch with addition of 0.1% sucralose for 3 minutes, and then they were packaged in vacuum sealed bags at $1^{\circ}C$ for 9 days. In order to evaluate the quality of packaged sliced pears, the quality index was determined in terms of color, firmness, soluble solids, and sensory quality. With the passage of storage time, no specific variation in firmness and soluble solids was observed. However, the ${\Delta}E$ value of the sliced pears treated with 5% oxidized starch solution was significantly lower than that of the other pears. Also, the Hunter L and b values of the sliced pears treated with 5% oxidized starch solution remained nearly constant from the beginning of storage. This observation shows that 5% oxidized starch solution was effective in reducing surface browning of sliced pears. Moreover, sliced pears treated with oxidized starch solution with addition of 0.1% sucralose were given an overall liking score which was slightly higher than that given to the other pears because of the sweetness of sucralose. In conclusion, 5% oxidized starch solution with addition of 0.1% sucralose was effective in reducing browning of sliced pears and in improving the taste of sliced pears.

• Resources Recycling
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• v.18 no.4
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• pp.38-43
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• 2009

The synthesis of aluminum oxalate, one of the aluminum organic compounds, has been performed using aluminum hydroxide as a raw material. For this aim, domestic aluminum hydroxide of 99.7% purity was dissolved by oxalic acid to produce an aqueous aluminum solution. As a result, it was found that aluminum hydroxide could be dissolved almost completely by the reaction with 1.0 mole/l oxalic acid solution at $90^{\circ}C$ for 16 hr. It was strongly required to keep the ratio of ethanol/Al solution more than 2.0 for the synthesis of aluminum oxalate from the aluminum solution. Furthermore, the pH should be controlled to be more than 8.2 in order to obtain the recovery of aluminum oxalate higher than 90%. From the chemical analysis of aluminum oxalate prepared in this work, the content of $NH_4$, Al and C was found to be 14.5, 7.18 and 17.4%, respectively. Accordingly, the aluminum oxalate synthesized from the aluminum solution was confirmed to be $(NH_4)_3Al(C_2O_4)_3$ $3H_2O$.