• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.25-30
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• 2013

The pore volume of hardened cement with waterproofing materials is lower compared to that of hardened cement without waterproofing materials. Thus, fewer gaps will appear by means of chemical reactions between $Ca^{2+}$ ions in hardened cement and water, solutes, and other ions. Due to the selective permeability, the osmotic pressure of hardened cement can change due to physical effects such as the reduction of the pore volume and the reduction in the number of pores, as well as by the electrochemical reaction between water, solutes, other ions and $Ca^{2+}$ ions in hardened cement. Of course, these factors do not have independent effects but instead a combined complex effect. Accordingly, we studied changes in the osmotic pressure due to the difference in the pore structure of hardened cement. A pore size smaller than 1 nm in hardened cement had only a slight effect on the osmotic pressure, whereas a pore size larger than 1 nm had a direct effect on the osmotic pressure.

• Membrane and Water Treatment
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• v.7 no.4
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• pp.355-365
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• 2016

The improvement of fouling resistance of porous polymeric membrane is one of the most important targets in membrane preparation for water purification in many process like wastewater treatment. Membranes can be modified by various techniques, including the treatment of polymer material, blending of hydrophilic polymer into polymer solution, and post treatment of fabricated membrane. This research proposed the modifications of morphology and surface property of hydrophobic membrane by blending polyethersulfone (PES) with three polymeric additives, polyvinylpyrrolidone (PVP), Pluronic F127 (Plu), and Tetronic 1307 (Tet). PES hollow fiber membranes were fabricated via dry-wet spinning process by using a spinneret with inner and outer diameter of 0.7 and 1.0 mm, respectively. The morphology changes of PES blend membrane by those additives, as well as the change of performance in ultrafiltration module were comparatively observed. The surface structure of membranes was characterized by atomic force microscopy and Fourier transform infra red spectroscopy. The cross section morphology of PES blend hollow fiber membranes was investigated by scanning electron microscopy. The results showed that all polymeric additives blended in this system affected to improve the performances of PES membrane. The ultra-filtration experiment confirmed that PES-PVP membrane showed the best performance among the three membranes on the basis of filtration stability.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.161-168
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• 2002

Latex modified concrete is governed by both cement hydration and polymer film formation processes in its binder phase. Such the reactions are expected to improve the polymer-cement co-matrixes themselves and the bond between the cement hydrates and aggregates, and to improve the properties of hardened latex-modified concrete. The purpose of this study was to study the strength and chemical resistance of Rapid-setting latex modified concrete(RSLMC) with the main experimental variables such as latex content(0, 5, 10, 15, 20%) and water-cement ratio(36, 38, 40%) at latex content 15%. Water absorption test was earned out to estimate water permeability resistance. Chemical resistance test was carried out to measure the weight change and to observe the appearance of RSLMC immersion in hydrochloric acid, sulfuric acid, and calcium choloride.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.155-165
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• 2014

In this study, using a complex of physical, chemical, and biological evaluation factors, the ecological vulnerability to climate change were evaluated at each river in the Nakdong river basin. First, runoff, sediment rate, and low flow discharge changes according to AIB climate change scenario using the SWAT model were simulated. Also, for the assessment of chemical and biological factors, 48 points that water quality monitoring sites and ecological health measurement points are matched with each other was selected. The water quality data of BOD and T-P and the biological data of IBI and KSI in each point were reflected in the assessment. Also, the future rise in water temperature of the rivers in Nakdong river basin was predicted, and the impact of water temperature rise on the fish habitat was evaluated. The top 10 most vulnerable points was presented through a summary of each evaluation factor. This study has a contribution to river restoration or management plan according to the characteristics of each river.

• Bulletin of the Korean Chemical Society
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• v.4 no.3
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• pp.128-132
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• 1983

The self-diffusion experiment of water was performed across two series of tactic poly(2-hydroxyethyl methacrylate), P(HEMA) membranes prepared by crosslinking with various amount of hexamethylene diisocyanate (HMDIC). The tagging material was tritium hydroxide (THO) and the efflux of THO was counted on a Liquid Scintillation Counter. The transport data of THO show that the permeability decreases as the amount of HMDIC increased from 2.5 to 10 mole % and the self-diffusions coefficient shows a parallel trend with it. The diffusivity data was discussed in terms of the change of water structural orderliness within membranes. Using the relation between viscosities and diffusivities derived from Eyring's absolute rate theory, the corresponding viscosities of water within two series of tactic P(HEMA) membranes were obtained. From this, it is seen that the viscosity of water within tactic P(HEMA) membranes may have the same values with those of supercooling water whose temperature ranges from -28 to -$36^{\circ}C.$.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.619-622
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• 2003

The concentrations of nutrients in precipitation increased slightly from May to June and did not change afterwards. Regarding irrigation water, the nutrient concentrations were high in the early stage of rice growth but decreased during the period of mid-June to mid-July. The concentration of Tot-N in runoff water increased significantly during the period of fertilizer application (basal, tillering, and panicle fertilization) and then decreased. The concentrations of Tot-N in runoff water ranged from 0.4 to 39.8mg/L (average of 5.9mg/L). The concentration of Tot-P in runoff water ranged from 0.0004 to 0.2084mg/L (average of 0.055mg/L). The Tot-P concentrations were high only at the early stage of rice growth after fertilizer application and did not change afterwards.

• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.431-436
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• 2003

Solvolytic rate constants at 25℃ are reported for solvolyses of cinnamyl bromide (1) in binary mixtures of water with acetone, ethanol, methanol, methanol-d, and 2,2,2-trifluoroethanol. Product selectivities are reported for solvolyses of 1 in aqueous ethanol and methanol. Rate ratios in solvents of the same $Y_{Br}$ value and different nucleophilicity provide measures of the minimum extent of nucleophilic solvent assistance (e.g. $[k_{40EW}/k_{97TFE}]$Y = 2.88, EW = ethanol-water). With use of the extended Grunwald-Winstein equation, the l and m values are similar to the values of 0.43 and 0.88 obtained for the solvolyses of 1 using the equation (see below) which includes a parameter (I) for solvation of aromatic rings. The magnitude of l and m values associated with a change of solvent composition predicts the $S_{N1}$ reaction mechanism rather than an $S_{N2}$ channel. Product selectivities (S), defined by S = [ether product]/[alcohol product]×[water]/[alcohol solvent] are related to four rate constants for reactions involving one molecule of solvent as nucleophile and another molecule of solvent as general base catalyst. A linear relationship between 1/S and molar ratio of solvent is derived theoretically and validated experimentally for solvolyses of the above substrates from water up 75% 1/S = $(k_{wa}/k_{aw})$([alcohol solvent]/[water]) + $k_{ww}/k_{aw}$ alcohol-water. The results are best explained by product formation from a “free” carbocation intermediate rather than from a solvent-separated ion pair.

• Bulletin of the Korean Chemical Society
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• v.11 no.2
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• pp.118-123
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• 1990

X-ray photoelectron spectra have been obtained and comparisons have been made for 1-2-3 and 2-1-1 phases of YBaCuO compounds. The photoelectron binding energies of all the constituent elements are consistently larger for the 2-1-1 phase than for the 1-2-3 phase. The peak intensities reflect different stoichiometries of the two phases. For the superconducting 1-2-3 phase, its degradation in air and interaction with water and carbon dioxide were examined by taking core level spectra of all the elements. It appears that yttrium is the most affected by exposure to air, since it undergoes a rapid change to carbonate when water and subsequently carbon dioxide are introduced.

• Journal of the Korean Chemical Society
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• v.61 no.6
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• pp.346-351
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• 2017

This study was planned considering the chain length, hydrophilicity, and hydrophobicity of the additives to be used in the polymerization, while various ophthalmic lenses that use various additives with similar water contents were manufactured before their optical and physical properties were compared and analyzed. With regard to the additives required for manufacturing high-, medium-, and low-water content lens groups, HEA (hydroxyethyl acrylate), PVP (polyvinylpyrrolidone), and NMV(N-methyl-N-vinylacetamide) were used as additives for preparing the high-water content lens group, HEMA(2-hydroxyethyl methacrylate), HPMA(hydroxypropyl methacrylate) and BD(1,4-butanediol) were used for the medium-water content lens group. For the low-water content lens group, BMA(buthyl methacrylate), BDDA(1,4-butanediol diacrylate), and Bis-GMA(bisphenol A glycerolate diacrylate) were used, respectively. The average water content of HEA was 40.14%; that of PVP, 39.63%; and that of NMV, 40.52%. The mean of water content was 35.92% for HEMA, 35.74% for BD, and 34.62% for HPMA. For the low-water content lens group, the mean of water content was 26.69% for BMA, 27.76% for BDDA, and 26.14% for Bis-GMA. With regard to the results of the water content measurement using a moisture analyzer, the average water content of the high-water content lens group was 41.34% for HEA, 42.62% for PVP, and 42.73% for NMV. Finally, for the low-water content lens group, the average water content was 28.62% for BMA, 28.82% for BDDA, and 28.32% for Bis-GMA. The measurements of the water contents of the lenses using the two methods showed that the water content and refractive index of the lenses were similar in all the lens groups. The measurements of the contact angles, however, showed a different wettability value for each lens with a similar water content. Also, the change tendency of the lens curvature according to the change of time showed that the change amount became larger and the recovery time became longer from the lens samples with a lower water content to those with a higher water content. Based on these results that will be helpful for the study of ophthalmic lenses.

• Clean Technology
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• v.22 no.1
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• pp.45-52
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• 2016

This study reports on the modeling and simulation of heat transfer in packaging boxes used for vaccine shipping. Both water and n-tetradecane are used as primary insulation materials inside a multi-slab system. The one-dimensional model, which is a spherical model using a radius equivalent to the rectangular geometry of container, is applied in this study. N-tetradecane with low thermal diffusivity and proper phase transition temperature exhibits higher heat transfer resistance during both heating and cooling processes compared to water. Thus, n-tetradecane is a better candidate as an insulating material for packaging containers for vaccine shipping. Furthermore, the developed method can also become a rapid and economic tool for screening appropriate phase change materials used as insulation materials with suitable properties in logistics applications.