• Journal of the Mineralogical Society of Korea
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• v.29 no.2
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• pp.59-71
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• 2016

To investigate the sorption characteristics of Cs, which is one of the major isotopes of nuclear waste, on natural zeolite chabazite, XRD, EPMA, EC, pH, and ICP analysis were performed to obtain the informations on chemical composition, cation exchange capacity, sorption kinetics and isotherm of chabazite as well as competitive adsorption with other cations ($Li^+$, $Na^+$, $K^+$, $Rb^+$, $Sr^{2+}$). The chabazite used in this experiment has chemical composition of $Ca_{1.15}Na_{0.99}K_{1.20}Mg_{0.01}Ba_{0.16}Al_{4.79}Si_{7.21}O_{24}$ and its Si/Al ratio and cation exchange capacity (CEC) were 1.50 and 238.1 meq/100 g, respectively. Using the adsorption data at different times and concentrations, pseudo-second order and Freundlich isotherm equation were the most adequate ones for kinetic and isotherm models, indicating that there are multi sorption layers with more than two layers, and the sorption capacity was estimated by the derived constant from those equations. We also observed that equivalent molar fractions of Cs exchanged in chabazite were different depending on the ionic species from competitive ion exchange experiment. The selectivity sequence of Cs in chabazite with other cations in solution was in the order of $Na^+$, $Li^+$, $Sr^{2+}$, $K^+$ and $Rb^+$ which seems to be related to the hydrated diameters of those caions. When the exchange equilibrium relationship of Cs with other cations were plotted by Kielland plot, $Sr^{2+}$ showed the highest selectivity followed by $Na^+$, $Li^+$, $K^+$, $Rb^+$ and Cs showed positive values with all cations. Equilibrium constants from Kielland plot, which can explain thermodynamics and reaction kinetics for ionic exchange condition, suggest that chabazite has a higher preference for Cs in pores when it exists with $Sr^{2+}$ in solution, which is supposed to be due to the different hydration diameters of cations. Our rsults show that the high selectivity of Cs on chabazite can be used for the selective exchange of Cs in the water contaminated by radioactive nuclei.

• Journal of Korean Society of Forest Science
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• v.37 no.1
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• pp.17-30
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• 1978

Press drying was used on italian poplar (Populus euamericana) to find the profitable means of drying. This study was designed to investigate the process of platen drying considering core temperature, drying time, current moisture content, drying rate, shrinkage and recovery, and green volume specific gravity, equilibrium moisture content and dimensional stability of press dried material and air dried material, The drying tests were conducted using 1.5 centimeter thick material at platen temperature of $175^{\circ}C$. The results were summarized as follows. 1. Core temperature was divided into three stages of drying characterized by period initial heating, plateau temperature and rising core temperature. Plateau temperature was 114 to $119^{\circ}C$. 2. The following predicting equations of drying time(y) in different core temperatures were developed for initial thickness($x_1$), initial moisture content ($x_2$) and final moisture content ($x_3$) 3. The predicting equaltion of current moisture content(u) was log u=4.658-0.060t as funtion of drying time(t) and that of drying rate(r) was log r=-2.797-0.049t. Current moisture content and drying rate of air drying were shown in figure 2. 4. The predicting equation of shrinkage in thickness direction(y) was log y=1.933+0.038t as function of drying time(t), and that of expansion in width direction was $y=-0.692+0.043t-0.001t^2$. 5. Thickness shrinkage was increased more than proportional at to pressure increase. Width shrinkage and thickness recovery was greatest at 35psi. 6. Green volume specific gravity of press dried material was 25% greater than that of air dried material. But equilibrium moisture content of press dried material was less 24% than that of air dried material. Antishrinkage efficiency of press dried material were obtained 27.7%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5542-5550
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• 2012

Third-order shear deformation theory is reformulated using the nonlocal elasticity of Eringen. The equation of equilibrium of the nonlocal elasticity are derived. This theory has ability to capture the both small scale effects and quadratic variation of shear strain through the plate thickness. Navier's method has been used to solve the governing equations for all edges simply supported boundary conditions. Analytical solutions of buckling of nano-scale plates are presented using this theory to illustrate the effect of nonlocal theory on buckling load of the nano-scale plates. The relations between nonlocal third-order and local theories are discussed by numerical results. Further, effects of (i) length (ii) nonlocal parameter, (iii) aspect ratio and (iv) mode number on nondimensional buckling load are studied. In order to validate the present solutions, the reference solutions are used and discussed. The present results of nano-scale plates using the nonlocal theory can provide a useful benchmark to check the accuracy of related numerical solutions.

• Clean Technology
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• v.26 no.3
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• pp.186-195
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• 2020

The isothermal adsorption, dynamic, and thermodynamic parameters of Acid black (AB) and Quinoline yellow (QY) adsorption by activated carbon were investigated using the initial concentration, contact time, temperature, and pH of the dyes as adsorption parameters. The adsorption equilibrium data fits the Freundlich isothermal adsorption model, and the calculated Freundlich separation factor values found that activated carbon can effectively remove AB and QY. Comparing the kinetic data showed that the pseudo second order model was within 10% error in the adsorption process. The intraparticle diffusion equation results were divided into two straight lines. Since the slope of the intraparticle diffusion line was smaller than the slope of the boundary layer diffusion line, it was confirmed that intraparticle diffusion was the rate-controlling step. The thermodynamic experiments indicated that the activation energies of AB and QY were 19.87 kJ mol^-1 and 14.17 kJ mol^-1, which corresponded with the physical adsorption process (5 ~ 40 kJ mol^-1). The adsorption reaction was spontaneous because the free energy change in the adsorption of AB and QY by activated carbon was negative from 298 to 318 K. As the temperature increased, the free energy value decreased resulting in higher spontaneity. Adsorption of AB and QY by activated carbon showed the highest adsorption removal rate at pH 3 due to the effect of anions generated by dissociation. The adsorption mechanism was electrostatic attraction.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.213-220
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• 2015

CFT column has a lot of structural advantages due to the composite behavior between in-filled concrete and steel tube. This paper deals with the development of an effective numerical model which can consider the bond-slip behavior between both components of concrete matrix and steel tube without taking double nodes. Since the applied axial load to in-filled concrete matrix is delivered to steel tube by the confinement effect and the friction, the governing equation related to the slip behavior can be constructed on the basis of the force equilibrium and the compatability conditions. In advance, the force and displacement relations between adjacent two nodes make it possible to express the slip behavior with the concrete nodes only. This model results in significant savings in the numerical modeling of CFT columns to take into account the effect of bond-slip. Finally, correlation studies between numerical results and experimental data are conducted to verifying the efficiency of the introduced numerical model.

• Korean Journal of Food Science and Technology
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• v.15 no.1
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• pp.19-26
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• 1983

A study was designed to investigate the sorption characteristics of binary mixtures of NaCl and sucrose or glucose stored at various relative humidities ranging from 46% to 92%. At low relative humidity below RH 65%, the sorption equilibrium was easily achieved, whereas at higher relative humidity values over 73%, all of the mixtures tended to cintinously absorb moisture with increase in storage time. A linear equation of log $({\frac{dw}{dt}})$ = a log(t) + log(b) was found to be valid between the sorption rate and storage time with respect to storage humidities. In sucrose-NaCl mixture, the slope showed a increasing tendency as the percentage of NaCl increased in the mixture, while that of glucose-NaCl mixture failed to show a definite trend. Plateaus were obtained when the amount of water absorbed was plotted on the X axis and the percent composition of mixture on the Y axis at different storage time. The shape of plateau was varied with respect to the kind of sugar-NaCl mixture, composition of the mixture and relative humidities. A linearity was found between log(1-Aw) and the amount of water absorbed over the Aw range 0.73-0.92 and the slope was affected by the kind and composition of sugar-NaCl mixtures.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1112-1116
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• 2009

The importance of securing water resources and their efficient management has attracted more attention recently due to water deficit. In water budget analysis, however, evapotranspiration (${\lambda}E$) has been approximated as the residual in the water balance equation or estimated from empirical equations and assumptions. To minimize the uncertainties in these estimates, it is necessary to directly measure ${\lambda}E$. In this study, using the eddy covariance technique, we have measured ${\lambda}E$ in a mixed forest in the Seolmacheon catchment in Korea from September 2007 to December 2008. During the growing season (May - July), ${\lambda}E$ in this mixed forest averaged about 2.2 mm $d^{-1}$, whereas it was on average 0.5 mm $d^{-1}$ during the non-growing season in winter. The annual total ${\lambda}E$ in 2008 was 581 mm $y^{-1}$, which is about 1/3 of the annual precipitation of 1997 mm. Despite the differences in the amount and frequency of precipitation, the accumulated ${\lambda}E$ during the overlapping period (i.e., September to December) for 2007 and 2008 was both ${\sim}$ 110 mm, showing virtually no difference. The omega factor, which is a measure of decoupling between forest and the atmosphere, was on average 0.5, indicating that the contributions of equilibrium ${\lambda}E$ and imposed ${\lambda}E$ to the total ${\lambda}E$ were about the same. The results suggest that ${\lambda}E$in this mixed forest was controlled by various factors such as net radiation, vapor pressure deficit, and canopy conductance. In this study, based on the direct measurements of ${\lambda}E$, we have quantified the relative contribution of ${\lambda}E$in the water balance of a mixed forest in the Seolmacheon catchment. In combination with runoff data, the information on ${\lambda}E$ would greatly enhance the reliability of water budget analysis in this catchment.

• Korean Journal of Environmental Agriculture
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• v.16 no.1
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• pp.72-79
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• 1997

Adsorption, leaching, and retention of the Flupyrazofos(KH-502), a new active ingredient for insecticide, in the soils under laborarory and field conditions were investigated to provide the basic data for the safety use and to assess a secondary impact of this insecticide on soil and water environments. A significant power function relation was found between the adsorbed KH-502 and time, representing that 45% of the added KH-502 was adsorbed within 30 min. but a quasiequilibrium was reached after 6 to 12 hr with a slower adsorption. Adsorption phenomena followed th first-order kinetics and time required for 50% adsorption was 5.8 hr. The equilibrium adsorption isotherm was explained by the Freundlich equation and was classified as S-type. The amounts of KH-502 leached through the soil column (C) as compared to initial conc. ($C_0$) were very low and these relative concentrations ($C/C_0$) were 0.073 and 0.017 in SL and CL soils, respectively. The residual conc. of KH-502 in the surface soil was comparatively low and decreased with time. Half-lives of KH-502 in the surface soil was comparatively low and decreased with time. Half-lives of KH-502 under the field conditions were estimated to be 20 and 18 days in the SL and CL soils, respectively. The KH-502 cone, transported to the subsurface soils was extremely low. These results demonstrate that KH-502 has a low pollution risk potential to the surrounding environment as far as it is used following the recommended guideline.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.298-304
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• 2017

The corrosion of reinforcements embedded in concrete causes some durability problems in reinforced and prestressed concrete structures. The epoxy coated reinforcements are one of the effective and reliable methods to prevent corrosion of reinforcements. However, it has been known that the epoxy coating reduces the bond capacity of reinforcement to concrete. This paper investigates the bond behaviors of epoxy coated reinforcements experimentally using direct pull-out test. Bond behaviors of epoxy coated bars for various reinforcement diameters of 10, 19 and 29mm and thicknesses of cover concrete of 1, 2, 3, and $4.5c/d_b$ (ratio of cover to bar diameter) are examined. Total 66 specimens were manufactured and tested according to the RILEM standard method. As the diameters of the epoxy coated reinforcements increase, the difference of bond strength between epoxy coated reinforcements and uncoated bars also increases. Epoxy coated bars showed more than 85% bond performance compared to those of uncoated bars. A new formular for estimating basic development length of epoxy coated reinforcement based on equilibrium equation is proposed using this experimental result.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.106-113
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• 1997

Dynamic loading of structures often causes excursions of stresses well into the inelastic range, and the influence of the geometric changes on the dynamic response is also significant in many cases. Therefore, both material and geometric nonlinearity effects should be considered in case that a dynamic load acts on the structure. A structure in a nuclear power plant is a structure of importance which puts emphasis on safety. A nuclear container is a pressure vessel subject to internal pressure and this structure is constructed by a reinforced concrete or a pre-stressed concrete. In this study, the material nonlinearity effect on the dynamic response is formulated by the elasto-viscoplastic model highly corresponding to the real behavior of the material. Also, the geometrically nonlinear behavior is taken into account using a total Lagrangian coordinate system, and the equilibrium equation of motion is numerically solved by a central difference scheme. The constitutive relation of concrete is modeled according to a Drucker-Prager yield criterion in compression. The reinforcing bars are modeled by a smeared layer at the location of reinforcements, and the steel layer model under Von Mises yield criteria is adopted to represent an elastic-plastic behavior. To investigate the dynamic response of a nuclear reinforced concrete containment structure, the steel-ratios of 0, 3, 5 and 10 percent, are considered. The results obtained from the analysis of an example were summarized as follows 1. As the steel-ratio increases, the amplitude and the period of the vertical displacements in apex of dome decreased. The Dynamic Magnification Factor(DMF) was some larger than that of the structure without steel. However, the regular trend was not found in the values of DMF. 2. The dynamic response of the vertical displacement and the radial displacement in the dome-wall junction were shown that the period of displacement in initial step decreased with the steel-ratio increases. Especially, the effect of the steel on the dynamic response of radial displacement disapeared almost. The values of DMF were 1.94, 2.5, 2.62 and 2.66, and the values increased with the steel-ratio. 3. The characteristics of the dynamic response of radial displacement in the mid-wall were similar to that of dome-wall junction. The values of DMF were 1.91, 2.11, 2.13 and 2.18, and the values increased with the steel-ratio. 4. The amplitude and the period of the hoop-stresses in the dome, the dome-wall junction, and the mid-wall were shown the decreased trend with the steel-ratio. The values of DMF were some larger than those of the structure without steel. However, the regular trend was not found in the values of DMF.