• Economic and Environmental Geology
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• v.42 no.6
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• pp.609-618
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• 2009

High permeable faults are important geological structures for fluid flow, energy, and solute transport. Therefore, high permeable faults play an important role in the formation of hydrothermal fluid (or hot spring), high heat flow, and hydrothermal ore deposits. We conducted 2-D coupled thermal and hydraulic modeling to examine thermohydraulic behavior in fault zones with various permeabilities and geometric conditions. The results indicate discharge temperature in fault zones increases with increasing fault permeability. In addition, discharge temperature in fault zones is linearly correlated with Peclet number ($R^2=0.98$). If Peclet number is greater than 1, discharge temperature in fault zones can be higher than $32^{\circ}C$. In this case, convection is dominant against conduction for the heat transfer in fault zones.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.225-229
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• 2017

Micron-sized dextran particles, which now attract wide attention as a promising drug delivery systems, can be prepared via the supercritical anti-solvent (SAS) process. In SAS process, dextran particles are obtained as a result of recrystallization of dissolved dextran in dimethyl sulfoxide (DMSO) on addition of supercritical $CO_2$ as an anti-solvent. In this work, with an intention to provide information on the feasible operating conditions of the process, the phase behavior of Dexran/DMSO/$CO_2$ is observed by measuring the cloud point in favor of a variable volume cell. From the experimental study, it is concluded that a feasible operating condition of the SAS process for preparation of dextran particles would be 300.15 K~330.15 K and 90 bar~130 bar, respectively, and solute concentration ranges from 5mg/ml to 20 mg/ml.

• Journal of Korea Foundry Society
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• v.43 no.6
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• pp.286-293
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• 2023

In this study, we investigated the microstructural evolution of Al-Mg-Zn aluminum alloy billet during homogenization treatment using OM, SEM, EDS and DSC. There were numerous phases found, such as; AlMgZn, AlMgFe, and AlMgZnSi phases, in the grain of the cast billet. After 6 hours homogenization treatment, Zn was mostly dissolved, whereas, Mg and Si were only partly dissolved. Accordingly, only AlMgFe and AlMgSi remained. After 18 hours, all of the leftover Mg and Si were dissolved, leaving only AlMgFe, which was also found after 24 hours. The results of the alloy design program, JMatPro showed that Mg dissloved more rapidly than Zn. According to the homogenization kinetic equation, Mg and Zn are completely dissolved within 1.9 and 3.5 hours, respectively.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.104-114
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• 2001

To investigate the effects of the addition of Nb and Sn on the recrystallization of Zr- Sn-Nb alloys, both Vickers micro-hardness test and TEP measurement were carried out on cold-worked specimens annealed at various temperatures from $300^{\circ}C$ to 75$0^{\circ}C$. The microstructures of heat treated specimens were analyzed by optical microscope, SEM, and TEM. The study of microhardness and microstructures showed that both recrystallization process and grain growth were retarded as the activation energy was increased by the addition of Nb and Sn. Especially, the addition of Sn was more effective on retarding recrystallization. Precipitates were formed more easily when Nb was added because the solubility of Nb into Zr is lower than that of Sn. However, the recrystallization process was affected more by Sn than Nb because the strain field formed by substitutional Sn repressed the dislocation movement. TEP was increased due to the decrease of electron scattering as recovery and recrystallization were proceeded and saturated when the recrystallization completed. However, when precipitates formed, TEP was increased because the decrease of solute concentration near the precipitates caused the decrease of electron scattering.

• KSBB Journal
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• v.14 no.3
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• pp.371-376
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• 1999

Simulation of preparative protein chromatography becomes necessary for separation as well as optimal operation. A mathematical model describing the behavior of elution peaks in preparative protein chromatography for single and binary component separation was solved numerically using a PDEsolver Macsyma$^{\circledR}$(Macsyma Inc., Arlington, MA, U.S.A.). Band profiles were calculated with the equilibrium-dispersive model of chromatography. The effects of the sample volume, concentrations of solutes in the sample, flow velocity and column length on the band profile of the elution peaks are discussed. The results in this paper suggest the model simulation for the binary mixture can be extended to multicomponent separations.

• Analytical Science and Technology
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• v.10 no.6
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• pp.408-417
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• 1997

Normal phase or reversed phase liquid chromatographic separation of some structural isomers of functionalized heterocyclic compounds has been carried out by using several different columns and various mobile phases. The optimal experimental conditions for separation of structural isomers were found on a ternary solvent system including alcohol as a modifier. This polar modifier is preferentially adsorbed onto strong adsorption site, leaving a more uniform population of weaker site that then serve to retain the sample. This 'deactivation' of the adsorbent leads to a number of improvements in subsequent separations. The optimal mobile phase system of separation were found on normal phase on structural isomers. Retention mechanism of normal phase system was also studied depending on adsorption strength between solute and stationary phase of column. However, retention factors of reversed phase system were found on hydrophobic interaction with solvophobic effect.

• Membrane Journal
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• v.26 no.4
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• pp.273-280
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• 2016

Pressure assisted forward osmosis (PAFO) is recently introduced because of its improved process efficiency to overcome drawbacks of forward osmosis (FO) such as low water flux and reverse solute diffusion. However, it is known that membrane fouling becomes deteriorated by additional hydraulic pressure applied in PAFO compared to FO. This study was performed to investigate possibility of intermittent pressure-assisted forward osmosis (I-PAFO) operation for fouling mitigation using colloidal silica particles as model foulants. FO, PAFO were operated as well to compare with. Two different solution pH conditions (pH 3, 10) were applied to see the effect of electrostatic interactions between the membrane and silica particles on fouling tendency. In the results, higher water flux was observed during pressurization and pressure relaxation periods in I-PAFO than water flux of PAFO, and FO on both pH conditions. Water flux decreased less in I-PAFO than PAFO after fouling. It resulted in higher water flux recovery in I-PAFO than PAFO after physical cleaning.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.33-36
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• 2007

In recent years the convective-dispersive equation has been often discredited in predicting subsurface solute transport under field conditions due to presence of preferential flow paths. Kim et al. (2005) proposed a simple equation that can predict the breakthrough of solutes without excessive data requirements. In their Generalized Preferential Flow Model (GPFM), the soil is conceptually divided in a saturated "distribution layer" near the surface and a "conveyance zone" with preferential flow paths below. In this study, we test the model with previously published data, and compare it with a classical convective-dispersive model (CDM). With three parameters required-apparent water content of the distribution zone, and solute velocity and dispersion in the conveyance zone-GPFM was able to describe the breakthrough of solutes both through silty and sandy loam soils. Although both GPFM and CDM fitted the data well in visual, variables for GPFM were more realistic. The most sensitive parameter was the apparent water content, indicating that it is the determining factor to apply GPFM to various soil types, while Kim et al. (2005) reported that changing the velocity of GPFM reproduced solute transport when same soils were used. Overall, it seems that the GPFM has a great potential to predict solute leaching under field conditions with a wide range of generality.

• Analytical Science and Technology
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• v.6 no.1
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• pp.107-119
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• 1993

The purpose of this study is to investigated the elution behavior of platinoid metal acetylacetonates, which is the key to elucidate their retention mechanism and optimize their RPLC separation conditions. The retention data of four platinoid metal acetylacetonates have been measured on four different columns in methanol-water and acetonitrile-water systems. The retention of uncharged platinoid metal acetylacetonates is interpreted by solvophobic effect. The retention of platinoid metal acetylacetonates is also greatly influenced by the geometric structure of the complexes. The square planar chelates, $Pd(acac)_2$, $Pt(acac)_2$, are retained longer than the octahedral chelates, $Rh(acac)_3$, $Ir(acac)_3$. It is likely due to that square planar chelates show greater interaction with nonpolar stationary phase than octahedral chelates. The results of van't Hoff plots have shown that platinoid metal acetylacetonates is operated on the same retention mechanism in the temperature range of $25{\sim}45^{\circ}C$. The study of the retention mechanism by the enthalpy-entropy compensation phenomenon has indicated that the retention mechanism of octahedral chelates and square planar chelates do not vary with the composition change of methanol-water mobile phase, respectively. In acetonitrile-water mobile phase, however, the retention mechanism is observed to be more complicated. Optimum condition for the separation of four platinoid metal acetylacetonates is found to be 40% methanol, polymeric C18 column, and $45^{\circ}C$.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.882-892
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• 2011

The influence of rhenium (Re) and ruthenium (Ru) addition on the solidification and solute redistribution behaviors in advanced experimental Ni-base superalloys has been investigated. A series of model alloys with different levels of Re and Ru were designed based on the composition of Ni-6Al-8Ta and were prepared by vacuum arc melting of pure metallic elements. In order to identify the influence of Re and Ru addition on the thermo-physical properties, differential scanning calorimetry analyses were carried out. The results showed that Re addition marginally increases the liquidus temperature of the alloy. However, the ${\gamma}^{\prime}$ solvus was significantly increased at a rate of $8.2^{\circ}C/wt.%$ by the addition of Re. Ru addition, on the other hand, displayed a much weaker effect on the thermo-physical properties or even no effect at all. The microsegregation behavior of solute elements was also quantitatively estimated by an electron probe microanalysis on a sample quenched during directional solidification of primary ${\gamma}$ with the planar solid/liquid interface. It was found that increasing the Re content gradually increases the microsegregation tendency of Re into the dendritic core and ${\gamma}^{\prime}$ forming elements, such as Al and Ta, into the interdendritic area. The strongest effect of Ru addition was found to be Re segregation. Increasing the Ru content up to 6 wt.% significantly alleviated the microsegregation of Re, which resulted in a decrease of Re accumulation in the dendritic core. The influence of Ru on the microstructural stability toward the topologically close-packed phase formation was discussed based on Scheil type calculations with experimentally determined microsegregation results.