• Membrane Journal
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• v.26 no.1
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• pp.62-69
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• 2016

In this study, sulfonated poly(ether ether ketone) (SPEEK) as cation exchange membrane and blended and crosslinked poly(vinyl amine) (PVAm) with poly(vinyl alcohol) (PVA) membrane as anion exchange membrane were used and then the performance experiments of the membrane capacitive deionization (MCDI) installed with both membranes were carried out. The newly prepared anion exchange membrane were characterized through water content, ion exchange capacity and FT-IR. The crosslinking time of 3 h to 5 h indicated that the salt removal was reduced from 81.3, 65.7% to 53.8%. The effect of PVAm contents from 40, 60, to 80% on the salt removal was shown 81.3, 75.2 and 37.7%, respectively. As a result, it was concluded that the crosslinking time and the content of PVAm had an influence on the salt removal efficiency.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.361-369
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• 2018

A manufacturing method has been devised to prepare novel heterogeneous cation exchange membranes by mixing ethylene vinyl acetate (EVA) copolymers with a commercial cation exchange resin. Optimum material characteristics, mixture ratios and manufacturing conditions have been worked out for achieving favorable membrane performance. Ion exchange capacity, electrical resistance, water uptake, swelling ratio and tensile strength properties were measured. SEM analysis was used to monitor morphology. Effects of vinyl acetate (VA) content, melt index (MI) and ion exchange resin content on properties of heterogeneous cation exchange membranes have been discussed. An application test was carried out by mounting a selected membrane in a membrane capacitive deionization (MCDI) system to investigate its desalination capability. 0.92 meq/g of ion exchange capacity, $8.7{\Omega}.cm^2$ of electrical resistance, $40kgf/cm^2$ of tensile strength, 19% of swelling ratio, 42% of water uptake, and 56.4% salt removal rate were achieved at best. VA content plays a leading role on the extent of physical properties and performance; however, MI is important for having uniform distribution of resin grains and achieving better ionic conductivity. Overall, manufacturing cost has been suppressed to 5-10% of that of homogeneous ion exchange membranes.

• Membrane Journal
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• v.27 no.5
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• pp.449-457
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• 2017

In this study, the 10 stages stacked module was designed by increasing the number of unit cells in the membrane capacitive deionization(MCDI) process. The aminated polysulfone and sulfonated poly(ether ether ketone) were synthesized and coated on porous carbon electrode by casting method. The salt removal efficiency was measured for the 10 stage stacked module under the operation conditions of adsorption voltage and time, desorption voltage and time, flow rate and concentration of feed water, and di-valent solutions including $CaSO_4$, $MgCl_2$ and tap water. Typically, when 100 mg/L of NaCl as the feed was used, the salt removal efficiency was 98.3% at a flow rate of 100 mL/min, the adsorption condition of 1.2 V/3 min and desorption condition of -0.5 V/5 min.

• Membrane Journal
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• v.27 no.2
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• pp.129-137
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• 2017

In this study, we have developed cation-exchange membranes (CEMs) which can efficiently separate heavy-metal ions among the cations contained in a water system. Sulfonated polyetheretherketone (SPEEK) was used as a base polymer and a powdered chelating resin with strong binding ability to heavy-metal ions was added into it. In order to optimize the performance of the CEM, the content of chelating resin powder and the ion exchange capacity of SPEEK have been controlled. As a result, it was confirmed that the removal efficiency of heavy metal ion was improved by more than 20% by applying the CEM to membrane capacitive deionization (MCDI).

• Journal of the Korean Data and Information Science Society
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• v.28 no.2
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• pp.361-369
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• 2017

This paper analyzes the causal relationship between dollar exchange rate and international oil price. Although large literature on the relationship has accumulated, results are not unique but diversified. Based on the idea that such diversified results may be due to different causality at different economic status, we considers an approach to test the causal relationship at each quantile. This approach is different from the mean causality analysis widely employed by the existing literature of the causal relationship. In this paper, monthly data from May 1987 to 2013 is used for the causal analysis in which Brent oil price and Major Currencies Dollar Index (MCDI) are considered. The test method is the nonparametric test for causality in quantile suggested by Jeong et al. (2012). The results show that although dollar exchange rate causes oil price in mean, the causal relationship does not exist at most quantiles.

• Korean Journal of Child Studies
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• v.23 no.5
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• pp.19-34
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• 2002

This study explored the relationship between language and play of 42 infants(21 boys and 21 girls) from 13 months to 23 months old and examined how their maternal language and play were related to the infants' language and play. The play of infant-mother and maternal language were videotaped at home. The MacArthur Communicative Development Inventory-Korean(MCDI-K; Fenson, 1991; Pae, 1993) was used to measure infant's language. The score of the infants' receptive language was higher than that of expressive language. Mean level of the infant's play was in the relational play, that is, he/she integrated two or more toys in an inappropriate manner during the play. There was no significant sex difference in the total language scores and in their play. The development of the infant's language was positively correlated with the infant's play level. The maternal language and play were positively correlated with the infant's language and play development.

• Korean Journal of Child Studies
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• v.26 no.1
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• pp.155-167
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• 2005

Korean infants' use of gesture was examined with 45 10-to 17-month olds. The mothers of infants were asked to check each word in the MacArthur Communicative Development Inventory-Korean (MCDI-K) vocabulary checklist if their infant had a gesture for a given word and to indicate what kind of early communicative behavior she showed in 5 different situations. The results show that infants in this study have 11 gestures, of which many are learned within the context of routines or games. Referential gestures were rarely reported. There was no positive correlation between the number of gestures and the number of expressive words. However, more qualitative measures on early communicative behaviors show that there was a positive correlation between "frequent use of gestures" and "try to communicate by verbal means".

• Korean Journal of Child Studies
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• v.30 no.5
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• pp.155-165
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• 2009

This study was conducted to identify relationships between toddler-teacher joint attention and toddlers' vocabularies. Toddlers' vocabularies were assessed by the MacArthur Communicative Development Inventory-Korean (MCDI-K) modified by Kim (2006); joint attention episodes were observed by classification categories for engagement condition (Bakeman & Adamson, 1984). Data were analyzed by means, t-test and Pearson's correlations. Results were that : (1) receptive vocabulary of toddlers was about 1.1 times as high as their expressive vocabulary. (2) Coordinated joint attention was observed most frequently, followed by supported joint attention; coordinated joint attention was closely related to support joint attention. (3) The relationship between toddler-teacher joint attention and toddlers' vocabularies were significant in a positive direction.

• Speech Sciences
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• v.10 no.4
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• pp.255-261
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• 2003

The purpose of this study was to investigate correlation of auditory development and language development of children with hearing impairment Eighteen subjects with severe or profound hearing loss participated in this study. They were 22-to 55-month-olds who had hearing parents with no additional disabling conditions. The test material was the Meaningful Auditory Integration Scale (MAIS) and MacArthur Communicative Development Inventory-Korea (MCDI-K). A Pearson Correlation Coefficient was determined through a statistical analysis. The results followed as; firstly there was a strong correlation between auditory development and receptive language development. Secondly, there was a strong correlation between receptive language development and expressive language development. Finally, there was a strong correlation between auditory development and education onset time. Therefore, auditory training is important method for auditory rehabilitation and education onset time is important variation for auditory development.

• Membrane Journal
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• v.27 no.1
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• pp.84-91
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• 2017

In this study, heterogeneous ion exchange membranes were prepared by mixing cation or anion exchange resins and commercial polyvinylidene fluoride (PVDF) for MCDI process. The mixing ratios of PVDF and ion exchange resins were 1 : 1, 1.4 : 1, 2 : 1, and 3 : 1. We characterized SEM, water content, ion exchange capacity, methanol permeability, and ion conductivity. In the viewpoint of membrane characterization, the blending ratio of 2 : 1 showed the best. For the blending ratio of 2 : 1, heterogeneous cation exchange membrane showed the water content 34%, ion exchange capacity 1.54 meq/g, ion conductivity 0.019 S/cm, and methanol permeability $2.28{\times}10^{-7}{\sim}8.86{\times}10^{-7}cm^2/s$ while In the case of heterogeneous anion exchange membrane, the result showed 37%, 2.18 meq/g, and 0.034 S/cm and $1.46{\times}10^{-7}{\sim}8.66{\times}10^{-7}cm^2/s$.