• Proceedings of the Korean Radioactive Waste Society Conference
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• 2006.06a
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• pp.158-159
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• 2006

• Proceedings of the Membrane Society of Korea Conference
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• 2000.11a
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• pp.71-74
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• 2000

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1999.04a
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• pp.6-7
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• 1999

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05a
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• pp.465-470
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• 2001

No Abstract (See Full-text)

• Proceedings of the Korea Water Resources Association Conference
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• 2003.05b
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• pp.759-762
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• 2003

• Journal of the Korean Chemical Society
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• v.52 no.2
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• pp.186-196
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• 2008

purpose of this study was to investigate college students' understanding of the thermodynamic aspects of the dissolution of solids and gases. The subjects were 34 juniors from the Seoul area who answered questionnaires composed of six items which asked the directions and reasons for the changes in enthalpy, entropy, and the solubility by temperature for the dissolution of solid sodium chloride and gaseous carbon dioxide into water. The results showed that the students understanding of the enthalpy change of dissolution was poor: many students answered that the dissolution of solids is an exothermic process because the dissolution occurs when the solute-solvent interaction is greater than the solute-solute interaction; the students also thought that the enthalpy should be reduced for spontaneous dissolution because the spontaneity depends on the enthalpy change only. For the entropy change, the students understanding was better and they explained it according to the meaning of disorder. For the temperature dependence of solubility, most students answered correctly regarding the direction, but only 25% of them explained the reason accounting for the enthalpy change. Many students who answered incorrectly on the enthalpy change could not explain the reason why.

• Membrane and Water Treatment
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• v.6 no.2
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• pp.127-139
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• 2015

Rejection of ionic solutes by reverse osmosis (RO) and nanofiltration (NF) membranes is controlled mainly by electrochemical interaction as well as pore size, but it is very difficult to directly evaluate such electrochemical interaction. In this work, we used an inverse HPLC method to investigate the interaction between ionic solutes and poly (m- phenylenediaminetrimesoyl) (PPT), a polymer similar to the skin layer of polyamide RO and NF membranes. Silica gel particles coated with PPT were used as the stationary phase, and aqueous solutions of the ionic solutes were used as the mobile phase. Chromatographs obtained for the ionic solutes showed features typical of exclusion chromatographs: the ionic solutes were eluted faster than water (mobile phase), and the exclusion intensity of the ionic solute decreased with increasing solute concentration, asymptotically approaching a minimum value. The charge density of PPT was estimated to be ca. 0.007 mol/L. On the basis of minimum exclusion intensity, the exclusion distances between a salt and neutralized PPT was examined, and the following average values were obtained: 0.49 nm for 1:1 salts, 0.57 nm for 2:1 salts, 0.60 nm for 1:2 salts, and 0.66 nm for 2:2 salts. However, $NaAsO_2$ and $H_3BO_3$, which are dissolved at neutral pH in their undissociated forms, were not excluded.

• Korean Journal of Materials Research
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• v.26 no.10
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• pp.528-534
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• 2016

The aim of this paper is to consider the effect of the manufacturing processes on corrosion and centerline cracking of ancient bronze spoons. The ancient bronze spoons in question were made by several steps of forging, in reheated condition with cast ingots. The manufacturing method is similar to that of the modern spoons. The investigations include observations from light and scanning electron microscopes of the microstructure in terms of the crack propagation. Cracks in the centerline are caused by solute segregation in the center-line region; this solute is solidified in the final stage of bronze spoon manufacture. Centerline cracking is also caused by ${\alpha}$ phase segregation, accompanied by forged overlapping along the longitudinal direction of the spoons. A vertical stripe with cracks along the centerline of the spoon's width is formed by folding in the wrought process. The overlapping area causes crack propagation with severe corrosion on the spoon surfaces over a period of a thousand years. The failure mechanisms of ancient bronze spoons may be similar to that of modern spoons, and the estimation of the failure mechanisms of ancient spoons can be appropriate to determine failure causes for such modern spoons.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.292-299
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• 2012

The objective of this study is to develop a novel method for evaluating forward osmosis (FO) membrane performances using a non-pressurized FO system. Basic membrane performance parameters including water (A) and solute (B) permeability coefficients and unique parameter for FO membrane such as the support layer structural parameter (S) were determined in two FO modes (i.e., active layer faces feed solution (AL-FS) and active layer faces draw solution (AL-DS)). Futhermore, these parameters were compared with those determined in a pressurized reverse osmosis (RO) system. Theoretical water flux was calculated by employing these parameters to a model that accounts for the effects of both internal and external concentration polarization. Water flux from FO experiment was compared to theoretical water fluxes for assessing the reliability of those parameters determined in three different operation modes (i.e., AL-FS FO, AL-DS FO, and RO modes). It is demonstrated that FO membrane performance parameters can be accurately measured in non-pressurized FO mode. Specifically, membrane performance parameters determined in AL-DS FO mode most accurately predict FO water flux. This implies that the evaluation of FO membrane performances should be performed in non-pressurized FO mode, which can prevent membrane compaction and/or defect and more precisely reflect FO operation conditions.

• Journal of the Korean Chemical Society
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• v.43 no.6
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• pp.656-662
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• 1999

We have obtained retention data of benzene, toluene, ethylbenzene, phenol, and acetophenone at 25, 30, 35, 40, 45 and 50 $^{\circ}C$ in 30/70, 40/60, 50/50, 60/40, 70/30, and 80/20 (v/v %) methanol/water eluents using a $C_18$ phase with a high ligand density. We drew van't Hoff plots from the data, and computed enthalpies and entropies of solute transfer from the mobile to the stationary phase. The cavity formation effect was found the major factor that governs the solute distribution between the mobile and stationary phases. The hydrophobic effect became significant in highly aqueous mobile phases. We also concluded that the Shodex C18-5B stationary phase was a polymer-like phase with a high ligand density, and followed a partially adsorption-like mechanism.