• Journal of Digital Convergence
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• v.15 no.6
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• pp.29-38
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• 2017

The purpose of this study was to examine the effects of users' organization-public relationship of the donation activities of corporate via social network service on corporate image and reputation focused on social network service users. The subjects were 228 SNS users selected. The data were analyzed by the correlation analysis, reliability analysis and structural equation modeling analysis using SPSS 21 and AMOS 21 program. The results were as follow. First, Organization-public relationships influenced positively on corporate image. Second, Organization-public relationships influenced positively on corporate reputation. Third, Corporate image influenced positively on corporate reputation. These results will contribute to develop a marketing strategy via social network service of corporate.

• Polymer(Korea)
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• v.24 no.6
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• pp.751-756
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• 2000

The copolymerization of ethylene (E) and cycloolefin (CO) was carried out with rac-Et(Ind)$_2$ZrC $l_2$ and MMAO cocatalyst system to examine the effect of CO structure on catalytic behaviors and properties of copolymer (COC). Various cycloolefins such as norbornene (N), 5-phenyl-2-norbornene (PN) and 5-vinyl-2-norbornene (VN) were used as comonomers. With increasing [CO]/[E] feed ratio, the catalytic activity decreased while the glass transition temperature of copolymer increased. With analysis of the structure of E/VN copolymer by FT-IR and $^{l3}$C-NMR, it was found that the cyclic C=C bond of VN comonomer is selectively polymerized and the vinyl C=C bond remains unreacted. The resulting vinyl C=C bond attached into copolymer provided the functionalization moiety using glycidyl methacrylate.e.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1824-1833
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• 2016

In this paper, we propose networked airborne relay-based positioning scheme (N-ARPS) based on time division multiple access (TDMA) networks to improve the performance of relative navigation (RelNav). To integrate the ARPS into TDMA, there are three problems such as slot allocation, selection of airborne relays, and method for signal loss to be solved. A subframe of N-ARPS is designed to assign the slots for broadcast and relay of navigation signals consecutively to minimize the effect of mobility. The selection algorithm determines the optimum set of airborne relays by selecting evenly distributed nodes depending on their distances to the master station. Finally, we uses precise position location information (PPLI) messages, which are received in data transmission period, to estimate a user position when the navigation signals are missing. The simulation results indicate that N-ARPS significantly improves user accuracy over RelNav.

• Polymer(Korea)
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• v.24 no.5
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• pp.664-672
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• 2000

It is generally agreed that transesterification provides the, copolymer in the melt blending of poly(ethylene naphthalate) (PEN) and poly($\varepsilon$-caprolactone) (PCL). Effects of the conditions of transesterification reaction and catalyst on the degree of randomness and average sequence length of PEN/PCL blends were investigated and results were used to interpret the biodegradability of PEN/PCL blends. It was found that degree of randomness values of obtained copolymer lied between 0 and 1, and it indicated that this blend consisted with physical blends of PEN/PCL and PEN/PCL block copolymers. The degree of randomness reached almost 1 which is the theoretical value of random copolymers and the average sequence length became shorter by the further transesterification reaction. In additions, it was found that the increase of copolymers, especially random copolymers reduced the biodegradability in PEN/PCL blends.

• Polymer(Korea)
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• v.24 no.5
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• pp.638-645
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• 2000

Linear and star-shaped, poly(lactic acid) (PLA) stereo-block copolymers were synthesized by sequential polymerization of DL-lactic acid and L-lactide in the presence of diol or polyol compounds. The molecular weight of block copolymers could be controlled to some extent by the variation of alcohol content. These block copolymers had relatively narrow molecular weight distributions. The glass transition temperature and melting temperature of block copolymers appeared at around 5$0^{\circ}C$ and 100~14$0^{\circ}C$, respectively. The block copolymers were found to crystallize even at the high D-stereoisomer concentration of 35 mol%, in contrast to the amorphous nature of the random copolymer with similar composition. Also we could observe the crystallinity of PLA stereo-block copolymers varying with annealing temperature and time.

• Journal of Digital Convergence
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• v.15 no.9
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• pp.125-135
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• 2017

The purpose of this study was to investigate the relationship among organization-public relationships, external reputation and job satisfaction of workers in small and medium-sized IT enterprises. The subjects were 221 workers in small and medium-sized IT enterprises selected. The data were analyzed by the exploratory factor analysis, confirmatory factor analysis, correlation analysis, reliability analysis and structural equation modeling analysis using IBM SPSS 21 program and IBM AMOS 21 program. The results were as follow. First, Organization-public relationships influenced positively on external reputation. Second, Organization-public relationships influenced not significantly on job satisfaction of workers in small and medium-sized IT enterprises. Third, External reputation influenced positively on job satisfaction of workers in small and medium-sized IT enterprises. These results will contribute to provide implications related to organization effectiveness.

• Polymer(Korea)
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• v.27 no.6
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• pp.528-535
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• 2003

The effects of surfactants, organic solvents, and functional monomers on the emulsion polymerization of perfluoroalkyleoylacryaltes and n-alkylacrylates were investigated. In particular, the dependence of the surface properties, contact angle and water repellency on the crystal melting temperature (T$\_$m/) of the fluorocopolymer and the variation of polymer latex particle sizes was investigated. Using WAXD experiments and synthesizing different types of fluorocopolymers which have fallowing fluoroacrylaytes [CH$_2$=CHCO$_2$CH,$_2$(CF$_2$CF$_2$) nH] (n = 4, 5 or 6), the relationship between the molecular packing structure of pendent side groups of fluorocopolymers and the surface properties was also investigated. We observed that the structure of primary carbon atoms of pendent side groups of fluorocopolymers plays key role in determining the surface properties.s.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.309-315
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• 1976

An efficient separation method and the utilization of sericin are searched. Sericin was extracted with hot water from cocoons under atmospheric pressure. The separated sericin was gel-filtrated with Sephadex G-75 and G-150 at room temperature and at $70^{\circ}C$. The results indicated that sericin is consisted of only one fraction in elution diagram. In the graft copolymerization of acrylonitrile to sericin ceric ammonium nitrate was chosen as an initiatior. A maximum yield was obtained at certain concentration of the initiator confirming our previous experiments. Viscosity measurement of alkali-hydrolyzed graft copolymers indicated that the polyacrylonitrile graft had the molecular weight in the range of 7,000.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.1-6
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• 2008

Block copolymers spontaneously assemble into various nanoscale structures such as spheres, cylinders, and lamellar structures according to the relative volumn ratio of each macromolecular block and their overall molecular weights. The self-assembled structures of block copolymer have been extensively investigated for the applications such as nanocomposites, photonic crystals, nanowires, magnetic-storage media, flash memory devices. However, the naturally formed nanostructures of block copolymers contain a high density of defects such that the practical applications for nanoscale devices have been limited. For the practical application of block copolymer nanostructures, a robust process to direct the assembly of block copolymers in thin film geometry is required to be established. To exploit self-assembly of block copolymer for the nanotechnology, it is indispensible to fabricate defect-free self-assembled nanostructure over an arbitrarily large area.

• Elastomers and Composites
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• v.48 no.1
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• pp.30-38
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• 2013

Polyolefin is one of the most important commodity polymers having excellent physical properties and cost competitiveness, which has continuously broadened their market in response to a heavy demand from industry. However, the lack of polarity in polyolefin has limited its applications, especially where interactions with other materials are important. In view of the above, the incorporation of polar functional groups in polyolefin has been widely attempted. Especially, the preparations of segmented modified polyolefin copolymers, such as block and graft copolymers have been extensively investigated, since the loss of the original properties of polyolefin can be minimized while the polar segments can endow interactions with other materials. Living radical polymerization (LRP) method can be one of the most attractive synthetic tools for the preparation of the modified polyolefin block or graft copolymers. In this review, progress on the preparation of the polyolefin based block or graft copolymers through LRP technique is briefly summarized.